JP2023024253A - Radar system - Google Patents

Abstract

To provide a radar system capable of accurately detecting targets.SOLUTION: A radar system 10 includes: a transmission circuit that outputs alternately a first transmission signal with a first center frequency and a second transmission signal with a second center frequency, which is the center frequency higher than the first center frequency every transmission cycle; and a transmitting antenna that transmits the first and second transmission signals. The second center frequency is a frequency higher than (1+1/Nc) times the first center frequency (Nc is an integer indicating the number of times each of the first transmission signal and the second transmission signal is transmitted in each transmission cycle within a predetermined cycle).SELECTED DRAWING: Figure 2

Description

The present disclosure relates to radar equipment.

2. Description of the Related Art In recent years, studies have been made on radar devices using short-wavelength radar transmission signals including microwaves or millimeter waves that can provide high resolution. Also, in order to improve outdoor safety, there is a demand for the development of a radar device (wide-angle radar device) that detects small objects such as pedestrians and falling objects in a wide-angle range in addition to vehicles.

As a configuration of radar equipment with a wide detection range, reflected waves are received by an array antenna consisting of multiple antennas (antenna elements), and the reflected waves are processed by a signal processing algorithm based on the reception phase difference with respect to the element spacing (antenna spacing). There is a configuration that uses a method of estimating the arrival angle (arrival direction) of (Direction of Arrival (DOA) estimation). For example, the method for estimating the angle of arrival includes the Fourier method, or the Capon method, MUSIC (Multiple Signal Classification), and ESPRIT (Estimation of Signal Parameters via Rotational Invariance Techniques) as methods that provide high resolution.

Further, as a radar device, for example, in addition to the receiving unit, the transmitting unit is also equipped with a plurality of antennas (array antennas), and beam scanning is performed by signal processing using the transmitting and receiving array antennas (MIMO (Multiple Input Multiple Output) radar is also called) has been proposed (see, for example, Non-Patent Document 1).

JP 2008-304417 A Japanese Patent Publication No. 2011-526371 JP 2014-119344 A WO2019/054504

J. Li, and P. Stoica, "MIMO Radar with Colocated Antennas", Signal Processing Magazine, IEEE Vol. 24, Issue: 5, pp. 106-114, 2007 M. Kronauge, H. Rohling, "Fast two-dimensional CFAR procedure", IEEE Trans. Aerosp. Electron. Syst., 2013, 49, (3), pp. 1817-1823 Direction-of-arrival estimation using signal subspace modeling Cadzow, J.A.; Aerospace and Electronic Systems, IEEE Transactions on Volume: 28 , Issue: 1 Publication Year: 1992 , Page(s): 64 - 79

However, methods for detecting target objects (or targets) in radar devices (for example, MIMO radar) have not been sufficiently studied.

A non-limiting embodiment of the present disclosure contributes to providing a radar device capable of accurately detecting a target.

A radar apparatus according to an embodiment of the present disclosure is configured such that, for each transmission period, a first transmission signal having a first center frequency and a second transmission signal having a second center frequency, which is a center frequency higher than the first center frequency. and a transmitting antenna for transmitting the first transmission signal and the second transmission signal, wherein the second center frequency is (1+1/N _c ) times the first center frequency ( _Nc is an integer representing the number of times each of the first transmission signal and the second transmission signal is transmitted in each transmission period within a predetermined period).

It should be noted that these generic or specific embodiments may be embodied in systems, devices, methods, integrated circuits, computer programs, or recording media. Any combination of media may be implemented.

According to an embodiment of the present disclosure, a target can be detected with high accuracy in a radar device.

Further advantages and advantages of an embodiment of the disclosure are apparent from the specification and drawings. Such advantages and/or advantages are provided by the several embodiments and features described in the specification and drawings, respectively, not necessarily all provided to obtain one or more of the same features. no.

A diagram showing an example of nonuniform Doppler multiplexing Block diagram showing a configuration example of a radar device A diagram showing an example of a chirp signal A diagram showing an example of a radar transmission signal Diagram showing an example of Doppler peak Diagram showing an example of Doppler peak Diagram showing an example of Doppler peak Diagram showing an example of Doppler peak Diagram showing an example of Doppler determination processing Diagram showing another example of chirp signal A diagram showing a configuration example of a radar device A diagram showing an example of a radar transmission signal Diagram showing an example of Doppler multiplex transmission Diagram showing an example of Doppler multiplex transmission A diagram showing an example of a chirp signal Diagram showing an example of Doppler multiplex transmission The figure which shows the structural example of a radar receiving part A diagram showing a configuration example of a radar device A diagram showing a configuration example of a radar device A diagram showing a configuration example of a radar device Block diagram showing another configuration example of the radar device A diagram showing another example of a radar transmission signal

In MIMO radar, for example, signals (radar transmission waves) multiplexed using time division, frequency division, or code division are transmitted from a plurality of transmission antennas (or called transmission array antennas), and signals reflected by surrounding objects ( Radar reflected waves) are received using a plurality of receiving antennas (or called receiving array antennas), and multiplexed transmission signals are separated and received from the respective received signals. Through such processing, the MIMO radar can extract the channel response indicated by the product of the number of transmitting antennas and the number of receiving antennas, and performs array signal processing on these received signals as a virtual receiving array.

Moreover, in the MIMO radar, by appropriately arranging the element intervals in the transmitting and receiving array antennas, it is possible to virtually enlarge the antenna aperture and improve the angular resolution.

[Time division multiplex transmission]
For example, Patent Document 1 discloses a MIMO radar multiplex transmission method using time-division multiplex transmission (hereinafter referred to as "time-division multiplex MIMO radar") in which signals are transmitted by shifting the transmission time for each transmission antenna. ) is disclosed. Time division multiplex transmission can be realized with a simpler configuration than frequency multiplex transmission or code multiplex transmission. In addition, time-division multiplex transmission can maintain good orthogonality between transmission signals by sufficiently widening the interval of transmission time. A time-division multiplex MIMO radar outputs a transmission pulse, which is an example of a transmission signal, while sequentially switching transmission antennas at a predetermined cycle. A time-division multiplex MIMO radar receives signals obtained by transmitting pulses reflected by objects with a plurality of receiving antennas, and performs, for example, spatial FFT (Fast Fourier Transforma) processing (reflection direction-of-arrival estimation processing).

A time-division multiplex MIMO radar sequentially switches transmission antennas for transmitting transmission signals (for example, transmission pulses or radar transmission waves) at predetermined intervals. Therefore, time-division multiplexing can take longer to finish transmitting transmission signals from all transmit antennas than frequency-division or code-division transmission. For this reason, for example, as in Patent Document 2, when transmitting a transmission signal from each transmitting antenna and detecting the Doppler frequency (for example, the relative velocity of the target) from those reception phase changes, in order to detect the Doppler frequency In applying Fourier frequency analysis to , the time interval (for example, the sampling interval) for observing the received phase change is lengthened. Therefore, the maximum Doppler frequency range based on the sampling theorem (for example, the Doppler frequency range that can be detected without aliasing or the relative velocity range of the target that can be detected) is reduced.

In addition, when it is assumed that a reflected wave signal from a target with a Doppler frequency exceeding the maximum Doppler frequency based on the sampling theorem is received, the radar equipment observes the Doppler frequency of aliasing components that differ from the true frequency. can be In this case, it is difficult for the radar apparatus to identify whether the reflected wave signal is a folding component or not, and ambiguity (ambiguity) of the Doppler frequency (for example, the relative velocity of the target) occurs.

For example, when a radar device transmits a transmission signal (transmission pulse) by sequentially switching Nt transmission antennas at a predetermined period T _r , the transmission time until transmission of the transmission signal from all the transmission antennas is completed. is T _r ×Nt. If we repeat such time-division multiplexing N _c times and apply Fourier frequency analysis for Doppler frequency detection (relative velocity detection), the Doppler frequency range over which we can detect the Doppler frequency without aliasing is determined by the sampling theorem Therefore, ±1/(2T _r ×Nt). Therefore, the Doppler frequency range in which the Doppler frequency can be detected without aliasing decreases as the number of transmitting antennas Nt increases, and Doppler frequency ambiguity tends to occur even at lower relative velocities.

[Doppler multiplex transmission]
Since time-division multiplexing MIMO radar may cause Doppler frequency ambiguity as described above, a method of simultaneously multiplexing and transmitting transmission signals from a plurality of transmission antennas will be focused below as an example.

As a method of simultaneously multiplexing and transmitting transmission signals from a plurality of transmission antennas, for example, a method of transmitting signals so that a plurality of transmission signals can be separated on the Doppler frequency axis in the receiving unit (hereinafter referred to as Doppler multiplex transmission). (see, for example, Non-Patent Document 3).

In Doppler multiplex transmission, the transmission unit, for example, for a transmission signal transmitted from a reference transmission antenna, a transmission signal transmitted from a transmission antenna different from the reference transmission antenna, the Doppler frequency bandwidth of the received signal A larger Doppler shift amount is given, and transmission signals are transmitted from a plurality of transmission antennas in the same transmission cycle (same transmission slot). In Doppler multiplex transmission, the receiving unit separates and receives transmission signals transmitted from each transmission antenna by filtering on the Doppler frequency axis.

Doppler multiplexing applies Fourier frequency analysis for Doppler frequency (or relative velocity) detection, compared to time division multiplexing, by transmitting the transmitted signals from multiple transmit antennas with the same transmission period. It is possible to shorten the time interval for observing the actual reception phase change. However, in Doppler multiplex transmission, since the transmission signals of each transmission antenna are separated by filtering on the Doppler frequency axis, the effective Doppler frequency bandwidth per transmission signal is limited.

For example, in Doppler multiplexing, a case will be described in which a radar device transmits transmission signals from Nt transmission antennas at a period T _r . When such Doppler multiplexing is repeated N _c times within a predetermined period and Fourier frequency analysis is applied to detect Doppler frequencies (or relative velocities), the Doppler frequency range in which Doppler frequencies can be detected without aliasing is It is ±1/(2×T _r ) according to the sampling theorem. For example, the Doppler frequency range in which the Doppler frequency can be detected without aliasing in Doppler multiplex transmission is expanded by Nt times compared to the case of time division multiplex transmission (eg, ±1/(2T _r ×Nt)). Note that the predetermined period is composed of the Doppler multiplex transmission period (cycle T _r ×Nc)+non-transmission period.

However, in Doppler multiplexing, the transmitted signals are separated by filtering on the Doppler frequency axis, as described above. Therefore, the effective Doppler frequency bandwidth per transmitted signal is narrower than the Doppler frequency range over which Doppler frequencies can be detected without aliasing. For example, if the Doppler frequency range ±1/(2×T _r ) in which the Doppler frequency can be detected without aliasing is equally divided into Nt transmitted signals, the effective Doppler frequency range for each signal is 1/(T _r × Nt), the Doppler frequency range is the same as in the case of time-division multiplex transmission. In addition, in Doppler multiplexing transmission, in the Doppler frequency band that exceeds the effective Doppler frequency range per transmission signal, the transmission signal is mixed with the Doppler frequency band of the other transmission signal, so the transmission signal is correctly separated. can be difficult to do.

[Unequally spaced Doppler multiplex transmission]
As a method for expanding the maximum detectable Doppler frequency range in such Doppler multiplex transmission, for example, the Doppler frequency range ±1/(2T _r ) in which the Doppler frequency can be detected without folding is equally divided into Nt+1, Among the Doppler shift amounts divided into Nt+1, there is a method of allocating Nt Doppler shift amounts to Nt transmission signals and simultaneously transmitting the transmission signals from Nt transmission antennas (for example, Patent Document 4).

In this Doppler multiplexing transmission, for example, a transmission signal is not allocated to some of the Doppler shift amounts equally divided into Nt+1 pieces, so the Doppler shift interval (hereinafter referred to as " Doppler multiplex spacing") will be unequal spacing. Such Doppler multiplexing is hereinafter referred to as "unequal interval Doppler multiplexing".

Next, an example of reception processing of radar reflected waves when using unequal interval Doppler multiplex transmission will be described.

In the output obtained by applying Fourier frequency analysis for Doppler frequency detection (relative velocity detection), for example, among the Doppler shift amounts equally divided into Nt+1, the Doppler shift amount corresponding to the Doppler shift amount to which the transmission signal is not assigned is lower than the received power level in Doppler corresponding to the amount of Doppler shift to which the transmitted signal is assigned. A radar device may, for example, estimate the Doppler frequency using this difference in received power levels. This estimation processing enables the radar device to estimate the Doppler frequency of the radar reflected wave in the Doppler frequency range ±1/(2T _r ).

In this way, the Doppler frequencies exceeding ±1/(2T _r × (Nt+1)) of the Doppler frequency domain divided by unequal Doppler multiplexing that imparts Doppler shifts at unequal intervals in the Doppler frequency domain. Even when a target is included, the radar system can suppress the ambiguity of the Doppler frequency by detecting Doppler regions with uneven intervals, and can expand the maximum detectable Doppler frequency to 1/2T _r . As a result, in unequal-interval Doppler multiplexing, the detectable Doppler frequency range is expanded by Nt times as compared with the method described in Patent Document 3, for example.

For example, in Patent Document 4, Doppler frequencies (or relative velocities) exceeding the maximum detectable Doppler frequency 1/2T _r are not detected due to restrictions of the sampling theorem of Fourier frequency analysis. For example, although it is possible to expand the Doppler detection range by shortening the transmission cycle T _r , in order to shorten the transmission cycle T _r while maintaining the detectable distance range or distance resolution, A with a higher sampling rate is required. Since the /D converter is used, the hardware configuration becomes complicated. In addition, increasing the sampling rate of the A/D converter may increase power consumption or heat generation in the radar device. On the other hand, if the transmission period _Tr is shortened under the restrictions of the sampling rate of the A/D converter, the detectable distance range is reduced, or the distance resolution is deteriorated, resulting in the distance detection range or distance in the radar device. Separation performance may deteriorate.

Further, in unequal interval Doppler multiplexing, for example, when there are a plurality of reflected waves from the same distance to the radar device, and the Doppler intervals of those reflected waves are the Doppler multiplexing interval (for example, "Δf _DDM ”), or if it matches a multiple of the Doppler multiplexing interval, the radar device is likely to make errors in detecting Doppler regions that are unevenly spaced, resulting in separation errors of multiple waves or angle measurement errors of multiple reflected waves. easier to increase.

For example, as shown in FIG. 1, the radar apparatus uses Nt=2 transmitting antennas, and among the Doppler shift amounts equally divided into 3 (=Nt+1), two Doppler shift amounts are used for unequal Interval Doppler multiplex transmission is performed, reflected waves #1 and #2 are received from targets at the same distance from the radar system, and the difference between the Doppler frequencies of reflected waves #1 and #2 is _Δf A case will be described.

(a), (b) and (c) of FIG. 1 show the output (e.g., the output of the frequency analysis section) of applying Fourier frequency analysis for Doppler frequency detection (or relative velocity detection), and FIG. (a) shows the received power of the reflected wave #1, (b) of FIG. 1 shows the received power of the reflected wave #2, and (c) of FIG. 1 shows the reflected wave #1 and the reflected wave Figure 2 shows the result of synthesizing the received signal of #2. Since the difference in Doppler frequency between reflected wave #1 and reflected wave #2 is Δf _DDM , reflected wave #2 in FIG. is shifted by +Δf _DDM .

As shown in (a) and (b) of FIG. 1, among the Doppler shift amounts equally divided into Nt+1, the received power level of the Doppler frequency corresponding to the Doppler shift amount to which no transmission signal is assigned is It is lower than the received power level of Doppler corresponding to the amount of Doppler shift to which the signal is assigned (approximately the noise level). tend to be high.

For example, in the case of (c) in FIG. 1, for reflected wave #1, the Doppler frequency -1/2T _r +2Δf _DDM , which corresponds to the amount of Doppler shift to which no transmission signal is assigned, has the transmission Since the signal matches the Doppler frequency corresponding to the assigned Doppler shift amount, the received power level tends to be high. Similarly, in the reflected wave #2, the Doppler frequency -1/ _2Tr corresponding to the Doppler shift amount to which the transmission signal is not assigned corresponds to the Doppler shift amount to which the transmission signal in the other reflected wave #1 is assigned. Since it matches the Doppler frequency, the received power level tends to be high.

In addition, since the received signal is composed of phase and amplitude, the received power obtained by combining a plurality of transmitted signals varies in the combined amplitude value depending on the phase value. For example, in the case of (c) in FIG. 1, the Doppler frequency component of -1/2T _r +Δf _DDM is the reflected wave #1 and the reflected wave #2, and matches the Doppler shift amount to which the transmission signal is assigned. Therefore, the received power is combined with each other, and the combined amplitude value changes depending on the phase value.

A radar receiver in a radar device using unequal-interval Doppler multiplexing demultiplexes the unequal-interval Doppler multiplexing, for example, using a Doppler demultiplexing unit, which will be described later, to match the Doppler multiplexing interval to which the transmission signal is assigned. Doppler peak positions are detected and Doppler multiplexed signals are separated. At this time, the Doppler demultiplexing unit uses the fact that the received power of the Doppler frequency components in Doppler multiplexing intervals to which Doppler multiplexed transmission signals are not assigned is sufficiently low,
Separate the Doppler multiplexed signals.

By using such a difference in received power level, the Doppler frequency can be uniquely estimated in the Doppler frequency range ±1/(2T _r ), and the Doppler multiplexed transmission signal can be separated. For example, in (a) of FIG. 1, the received power of the reflected wave #1 is -1/2T _r that matches the Doppler multiplexing interval Δf _DDM , and the Doppler peak position of the Doppler frequency components of -1/2T _r +Δf _DDM . is detected, and the received power of the Doppler frequency component (-1/2T _r +2Δf _DDM ) shifted from these Doppler peak positions by the Doppler multiplexing interval Δf _DDM is sufficiently low. Estimation and separation of Doppler multiplexed signals are performed.

However, for example, the received power at the Doppler frequency -1/2T _r +2Δf _DDM in (c) of FIG. 1 is higher than the received power at the Doppler frequency -1/2T _r +2Δf _DDM in (a) of FIG. It becomes a Doppler position, the Doppler frequency estimation of the reflected wave #1 is likely to be erroneous, and the separation performance of the transmitting antenna deteriorates. Similarly, for example, the received power at the Doppler frequency -1/2T _r in (c ₎ of FIG. The Doppler frequency estimation of reflected wave #2 is likely to be erroneous, and the separation performance of the transmitting antenna deteriorates.

In addition, in FIG. 1 (c), at the Doppler frequency (-1/2T _r +1Δf _DDM ), the Doppler of Tx#2 of reflected wave #1 and the Doppler of Tx#1 of reflection #2, which are different in phase and amplitude, respectively , the phase and amplitude change from the states shown in (a) and (b) of FIG.

For example, in (c) of FIG. 1, the difference in Doppler frequency between reflected wave #1 and reflected wave #2 is +Δf _DDM . At the frequency (solid line x mark, -1/2T _r +2Δf _DDM ), the Dop frequency component of the reflected wave #2, to which the transmission signal by Tx#2 is assigned, is received redundantly.

In addition, since the difference between the Doppler frequencies of reflected wave #2 and reflected wave #1 is -Δf _DDM , the Doppler frequency corresponding to the Doppler shift amount to which the transmitted signal is not assigned in reflected wave #2 (dotted circle, -1 /2T _r ), of the reflected wave #1, the Dopp frequency component to which the transmission signal by Tx#1 is assigned is received in duplicate.

Therefore, if reflected waves #1 and #2 are received from targets at the same distance, and the difference between the Doppler frequencies of reflected waves #1 and #2 is Δf _DDM , the Doppler The Doppler frequency corresponding to the shift amount (solid line x mark or dotted line circle mark in FIG. 1(c)) is originally the Doppler shift amount (Tx# of reflected wave #1 in FIG. 1(a)) to which the transmission signal is assigned. 1 and Tx#2, Tx#1 and Tx#2 at reflected wave #2 in FIG. 1(b)).

However, the Doppler frequency corresponding to the Doppler shift amount to which no transmission signal is assigned tends to be high because it includes the received power of the other reflected wave. For example, for the solid line x mark in FIG. 1(a), since Tx#2 of the reflected wave #2 in FIG. 1(b) is included, the Doppler frequency in FIG. 1(c)=-1/2T _r + The combined received power in 2Δf _DDM tends to be high.

Therefore, in the state of (c) in FIG. 1, the radar apparatus has an increased probability of erroneously estimating the Doppler frequency. If the radar system makes a mistake in Doppler frequency estimation, it is likely to make a mistake in properly separating the transmitting antennas, and the angle measurement error is likely to increase.

Moreover, even if the Doppler frequency is correctly estimated, as shown in FIG. (Doppler frequency is -1/2T _r +1Δf _DDM ), they are added (combined) as a complex signal, so the amplitude component or phase component changes from the state of (a) and (b) in FIG. Angle measurement accuracy of the radar device tends to deteriorate.

Accordingly, in a non-limiting embodiment of the present disclosure, a method for expanding the range of Doppler frequencies in which aliasing does not occur (eg, ambiguity does not occur) in Doppler multiplexing will be described. As a result, the radar apparatus according to one embodiment of the present disclosure can accurately detect a target over a wider Doppler frequency range.

Further, in a non-limiting embodiment of the present disclosure, the Doppler interval of reflected waves from each of a plurality of targets at approximately the same distance from the radar device is the Doppler multiplex interval (or a multiple of the Doppler multiplex interval). A method for enabling separate detection of each reflected wave even when they match will be described.

Further, in a non-limiting embodiment of the present disclosure, in Doppler multiplex transmission, the range of Doppler frequencies (relative velocities) in which aliasing does not occur is expanded, and multiple targets at similar distances to the radar device A method for enabling separate detection of each reflected wave even when the Doppler interval of the reflected wave from each matches the Doppler multiplex interval (or a multiple of the Doppler multiplex interval) will be described.

Note that the radar device according to an embodiment of the present disclosure may be mounted on a moving object such as a vehicle, for example. The positioning output (information on estimation results) of the radar device installed in the mobile object is used, for example, by an advanced driver assistance system (ADAS) that enhances collision safety, or a control ECU (Electronic Control Unit) such as an automatic driving system. Unit) (not shown) and may be used for vehicle drive control or alarm call control.

Also, the radar apparatus according to an embodiment of the present disclosure may be attached to a relatively high structure (not shown) such as a roadside utility pole or a traffic signal. Such a radar device can be used, for example, as a sensor in a support system that enhances the safety of passing vehicles or pedestrians, or an intrusion prevention system for suspicious persons. Further, the positioning output of the radar device may be output to a control device (not shown) in, for example, a support system that enhances safety or a system for preventing intrusion by suspicious persons, and may be used for alarm call control or abnormality detection control.

Note that the uses of the radar device are not limited to these, and may be used for other uses.

Hereinafter, an embodiment according to an example of the present disclosure will be described in detail with reference to the drawings. In addition, in the embodiments, the same constituent elements are denoted by the same reference numerals, and redundant description thereof will be omitted.

In the following, in a radar device, a transmission branch transmits different transmission signals that are multiplexed simultaneously from a plurality of transmission antennas, and a reception branch separates each transmission signal and performs reception processing (for example, a MIMO radar configuration). will be explained.

Also, in the following, as an example, a configuration of a radar system using a frequency-modulated pulse wave such as a chirp pulse (for example, also called chirp pulse transmission (fast chirp modulation)) will be described. However, the modulation method is not limited to frequency modulation. For example, one embodiment of the present disclosure is also applicable to a radar system using a pulse compression radar that transmits a pulse train by phase-modulating or amplitude-modulating it.

(Embodiment 1)
[Configuration of radar device]
The radar device 10 of FIG. 2 has a radar transmitter (transmission branch) 100 and a radar receiver (reception branch) 200 .

Radar transmission section 100 generates a radar signal (radar transmission signal) and transmits the radar transmission signal at a predetermined transmission cycle using a transmission array antenna composed of a plurality of transmission antennas 106-1 to 106-Nt. do.

Radar receiver 200 receives a reflected wave signal, which is a radar transmission signal reflected by a target (not shown), using a receiving array antenna including a plurality of receiving antennas 202-1 to 202-Na. The radar receiver 200 performs signal processing on the reflected wave signal received by each receiving antenna 202, and, for example, detects the presence or absence of a target or estimates the direction of arrival of the reflected wave signal.

A target is an object to be detected by the radar device 10, and includes, for example, vehicles (including four-wheeled vehicles and two-wheeled vehicles), people, blocks, curbs, and the like.

[Configuration of radar transmission unit 100]
Radar transmission section 100 has radar transmission signal generation section 101, signal generation control section 104, Doppler shift sections 105-1 to 105-Nt, and transmission antennas 106-1 to 106-Nt. For example, the radar transmitter 100 has Nt transmit antennas 106 , each of which is connected to an individual Doppler shifter 105 .

The radar transmission signal generation unit 101 generates a radar transmission signal based on control from the signal generation control unit 104, for example. The radar transmission signal generator 101 has, for example, a modulated signal generator 102 and a VCO (Voltage Controlled Oscillator) 103 . Each component in the radar transmission signal generator 101 will be described below.

The modulated signal generator 102 periodically generates, for example, a sawtooth-shaped modulated signal. Here, the radar transmission cycle is _Tr .

The VCO 103 generates a frequency modulated signal (hereinafter referred to as a frequency chirp signal or a chirp signal, for example) based on the modulated signal output from the modulated signal generating section 102, and the Doppler shift sections 105-1 to 105-Nt, Then, it outputs to the radar receiving section 200 (the mixer section 204 described later).

The signal generation control section 104 controls the radar transmission signal generation section 101 (for example, the modulation signal generation section 102 and the VCO 103) to generate a radar transmission signal. For example, the signal generation control unit 104 may set parameters (for example, modulation parameters) relating to chirp signals so that chirp signals with different center frequencies are alternately transmitted.

The two chirp signals with different center frequencies are hereinafter referred to as "first chirp signal" and "second chirp signal", respectively.

FIG. 3 shows examples of chirp signals (eg, a first chirp signal and a second chirp signal).

As shown in FIG. 3, the modulation parameters for the chirp signal include, for example, center frequency f _c (q), frequency sweep bandwidth B _w (q), sweep start frequency f _cstart (q), sweep end frequency f _cend ( q), frequency sweep time T _sw (q), and frequency sweep change rate D _m (q). Note that D _m (q)=B _w (q)/T _sw (q). Also, B _w (q)=f _cend (q)−f _cstart (q) and f _c (q)=(f _cstart (q)+f _cend (q))/2. Also, for example, q=1,2, where q=1 may represent the modulation parameter of the first chirp signal, and q=2 may represent the modulation parameter of the second chirp signal.

Also, the frequency sweep time T _sw (q) corresponds to, for example, a time range (or called a range gate) for acquiring A/D sample data in the A/D converter 207 of the radar receiver 200 described later. The frequency sweep time T _sw (q) may be set, for example, to the entire interval of the chirp signal as shown in FIG. It may be set to the interval of part.

Although FIG. 3 shows an example of an up-chirp waveform in which the modulation frequency gradually increases over time, it is not limited to this, and a down-chirp in which the modulation frequency gradually decreases over time is applied. good too. A similar effect can be obtained regardless of whether the modulation frequency is up-chirp or down-chirp.

For example, the signal generation control unit 104 may set (or select) a center frequency f _c (q) that satisfies a predetermined condition (an example will be described later).

In the following, as an example, among the modulation parameters set for the first chirp signal and the second chirp signal, the center frequencies f _c (q) are different from each other, and the other modulation parameters other than the center frequencies are the same ( or common) will be described. However, it is not limited to this, and for the application of an embodiment of the present disclosure, for example, the first chirp signal and the second chirp signal need only have the same resolution in the distance axis, so the frequency sweep bandwidth B _w (q ) are set to have the same relationship (an example will be described later).

Further, in the following description, the signal generation control unit 104 controls the modulation signal generation unit 102 and the VCO 103 so that, for example, two chirp signals with different center frequencies f _c (q) are alternately transmitted Nc times. you can

FIG. 4 shows an example of a chirp signal output by the radar transmission signal generator 101 under the control of the signal generation controller 104. As shown in FIG.

In FIG. 4, the transmission period T _r1 of the first chirp signal and the transmission period T _r2 of the second chirp signal may be different (T _r1 ≠T _r2 ) or may be the same (T _r1 =T _r2 ). In addition, hereinafter, a cycle combining the transmission cycles T _r1 and T _r2 is expressed as “T _rs ”. For example, the transmission period T _rs indicates the transmission period during which the set of first and second chirp signals are transmitted, where T _rs =T _r1 +T _r2 . In addition, in the following description, unless otherwise specified, each transmission period T _r1 and T _r2 represents the same value parameter (for example, T _r1 =T _r2 ), and is conveniently referred to as the transmission period T _r sometimes.

Similarly, the frequency sweep bandwidth, frequency sweep time (or range gate), and frequency sweep rate of change are the same for each of the first chirp signal and the second chirp signal, unless otherwise specified. where B _w (1)=B _w (2)=B _w , T _sw (1)=T _sw (2)=T _sw , D _m (1)=D _m (2)=D _m and There is something to express.

Also, the frequency sweep bandwidths of the chirp signals with different center frequencies may not include overlapping bands as shown in FIG. It may include a band. One embodiment of the present disclosure, for example, if the center frequency relationship between the first chirp signal and the second chirp signal satisfies a predetermined condition, regardless of whether the frequency sweep bandwidth includes overlapping bands, , a similar effect is obtained.

In an embodiment of the present disclosure, the transmission period T _rs may be set to, for example, several hundred μs or less, and the transmission time interval of the radar transmission signal may be set relatively short. As a result, for example, even if the center frequencies of the first chirp signal and the second chirp signal are different, the frequency of the beat signal of the received reflected wave (for example, the beat frequency index) does not change. It is detectable as a change in Doppler frequency.

Each chirp signal output from the radar transmission signal generator 101 (eg, VCO 103) is input to each mixer 204 and Nt Doppler shifters 105 of the radar receiver 200, for example.

The Doppler shift unit 105 gives a phase rotation φ _n to the chirp signal input from the VCO 103 in order to give a Doppler shift amount DOP _n for each chirp signal transmission period (for example, T _r1 or T _r2 ). and outputs the Doppler-shifted signal to the transmitting antenna 106 . where n=1,...,Nt. An example of a method of giving the Doppler shift amount DOP _n (for example, phase rotation φ _n ) in the Doppler shifter 105 will be described later.

The output signals of Doppler shifters 105-1 to 105-Nt are amplified to a predetermined transmission power and radiated into space from each transmission antenna 106 (for example, Tx#1 to Tx#Nt).

[Configuration of radar receiver 200]
In FIG. 2, the radar receiving section 200 has Na receiving antennas 202 (for example, Rx#1 to Rx#Na) and constitutes an array antenna. Further, the radar receiving unit 200 includes Na antenna system processing units 201-1 to 201-Na, a CFAR (Constant False Alarm Rate) unit 211, a Doppler demultiplexing unit 212, a Doppler determination unit 213, and a direction estimation unit. a portion 214;

Note that the CFAR unit 211 may include, for example, a CFAR unit 211-1 and a CFAR unit 211-2 respectively corresponding to the first chirp signal and the second chirp signal having different center frequencies. Similarly, the Doppler demultiplexer 212 may include, for example, a Doppler demultiplexer 212-1 and a Doppler demultiplexer 212-2 respectively corresponding to the first chirp signal and the second chirp signal having different center frequencies. Although FIG. 2 shows a configuration in which CFAR units 211 are provided in parallel (CFAR units 211-1 and 211-2), one CFAR unit 211 is provided and its input is sequentially switched. It is good also as a structure which processes. FIG. 2 shows a configuration in which Doppler demultiplexing units 212 are provided in parallel (Doppler demultiplexing units 212-1 and 212-2). A configuration in which processing is sequentially switched may be employed.

Each receiving antenna 202 receives a reflected wave signal, which is a radar transmission signal reflected by a target, and outputs the received reflected wave signal to the corresponding antenna system processing section 201 as a received signal.

Each antenna system processing section 201 has a receiving radio section 203 and a signal processing section 206 .

Receiving radio section 203 has mixer section 204 and LPF (low pass filter) 205 . In reception radio section 203, mixer section 204 mixes the received reflected wave signal (reception signal) with a chirp signal, which is a transmission signal. Further, by passing the output of the mixer section 204 through the LPF 205, a beat signal having a frequency corresponding to the delay time of the reflected wave signal is extracted. For example, the difference frequency between the frequency of the transmission signal (transmission frequency modulated wave) and the frequency of the received signal (reception frequency modulated wave) is obtained as the beat frequency (or beat signal).

The signal processing unit 206 of each antenna system processing unit 201-z (where z = any of 1 to Na) has an A/D conversion unit 207, a beat frequency analysis unit 208, and a Doppler analysis unit 210. . The Doppler analysis section 210 may include, for example, a Doppler analysis section 210-1 and a Doppler analysis section 210-2 respectively corresponding to the first chirp signal and the second chirp signal having different center frequencies.

A signal (for example, a beat signal) output from the LPF 205 is converted into discrete sample data that is discretely sampled by the A/D conversion section 207 in the signal processing section 206 .

The beat frequency analysis unit 208 performs FFT processing on N _data pieces of discrete sample data obtained in a predetermined time range (range gate) for each transmission cycle _Tr . Here, the range gate sets the frequency sweep time T _sw (q). Here, for example, q=1, 2, where q=1 represents the frequency sweep time of the first chirp signal, and q=2 represents the frequency sweep time of the second chirp signal. As a result, the signal processing unit 206 outputs a frequency spectrum in which a peak appears at the beat frequency corresponding to the delay time of the reflected wave signal (radar reflected wave). Note that the beat frequency analysis unit 208 may multiply window function coefficients such as a Han window or a Hamming window during FFT processing. Side lobes generated around the beat frequency peak can be suppressed by using the window function coefficients.

Here, RFT z _,q (f _b , m) is the beat frequency response output from the beat frequency analysis unit 208 in the z-th signal processing unit 206 obtained by transmitting the m-th chirp pulse of the q-th chirp signal. Represented by where f _b represents the beat frequency index and corresponds to the FFT index (bin number). For example, f _b =0,˜,N _data /2−1, z=1,˜,Na, m=1,˜, _NC , and q=1 or 2. A smaller beat frequency index f _b indicates a beat frequency with a shorter delay time of the reflected wave signal (eg, closer to the target).

Also, the beat frequency index f _b can be converted into distance information R(f _b ) using the following equation (1). Therefore, the beat frequency index f _b is hereinafter referred to as the “distance index f _b ”.

where B _w represents the frequency sweep bandwidth in the chirp signal and C ₀ represents the speed of light. Also, in Equation (1), C ₀ /2B _w represents the distance resolution. Range resolution ΔR=C ₀ /2B _w is hereinafter expressed.

Based on the control signal output from the signal generation control unit 104, the output switching unit 209 switches the output of the beat frequency analysis unit 208 to 2 according to the transmission cycle of the first chirp signal or the transmission cycle of the second chirp signal. Doppler analysis units 210 are selectively switched for output. For example, the output switching unit 209 outputs the output of the beat frequency analysis unit 208 in the transmission period _Tr1 of the first chirp signal (eg, q=1) to the Doppler analysis unit 210-1. Also, for example, the output switching unit 209 outputs the output of the beat frequency analysis unit 208 in the transmission period _Tr2 of the second chirp signal (eg, q=2) to the Doppler analysis unit 210-2.

The q-th Doppler analysis unit 210 (also referred to as Doppler analysis unit 210-q) outputs a beat _frequency response RFT _z,q ( Doppler analysis is performed for each distance index f _b using f _b , 1), RFT _z,q (f _b , 2), ∼, RFT _z,q (f _b , N _C ). For example, the q-th Doppler analysis unit 210 may estimate the Doppler frequency from the reflected wave signal of the q-th chirp signal reflected from the target.

For example, if _Nc is a power of 2, FFT processing can be applied in Doppler analysis. In this case, the FFT size is N _c , and the maximum Doppler frequency without aliasing derived from the sampling theorem is ±1/(2T _rs ). Also, the Doppler frequency interval of the Doppler frequency index _fs is 1/( _Nc × _Trs ), and the range of the Doppler frequency index _fs is _fs = _-Nc /2, ~, 0, ~, _Nc / 2-1.

A case where N _c is a power of 2 will be described below as an example. If N _c is not a power of 2, for example, FFT processing can be performed with a data size of powers of 2 by including zero-padded data. Also, the Doppler analysis unit 210 may multiply window function coefficients such as a Han window or a Hamming window during FFT processing. By applying the window function, side lobes generated around the beat frequency peak can be suppressed.

For example, the output VFT _z,q (f _b , f _s ) of the q-th Doppler analysis unit 210 of the z-th signal processing unit 206 is given by the following equation (2). Note that j is an imaginary unit, z=1 to Na, and q=1,2.

The processing in each component of the signal processing unit 206 has been described above.

In FIG. 2, the CFAR unit 211 performs CFAR processing (for example, adaptive threshold determination) using the output from the Doppler analysis unit 210 of the 1st to Na-th signal processing units 206, and local peaks Extract the range index f _{b_cfar} and the Doppler frequency index f _{s_cfar} that gives the signal. As shown in FIG. 2, the CFAR unit 211 includes a first CFAR unit 211 (or referred to as a CFAR unit 211-1) that performs CFAR processing using the output of the first Doppler analysis unit 210, and a second Doppler analysis unit. A second CFAR unit 211 (or referred to as CFAR unit 211-2) that performs CFAR processing using the output of 210 may be provided.

The q-th CFAR unit 211 (q=1, 2), for example, outputs VFT _1,q (f _b , f _s ), VFT _2,q (f _b , f _s ), ~, VFT _Na,q (f _b , f _s ) are power-added, and from the distance axis and Doppler frequency axis (equivalent to relative velocity) Two-dimensional CFAR processing or CFAR processing combining one-dimensional CFAR processing is performed. For CFAR processing that combines two-dimensional CFAR processing or one-dimensional CFAR processing, for example, the processing disclosed in Non-Patent Document 2 may be applied.

The q-th CFR section 211 adaptively sets a threshold, and uses the distance index f _{b_cfar} (q), the Doppler frequency index f _{s_cfar} (q), and the received power information PowerFT(f _{b_cfar} (q ), f _{s_cfar} (q)) to the q-th Doppler demultiplexer 212 .

The Doppler demultiplexing unit 212 performs Doppler demultiplexing processing using the outputs of the first Doppler analysis unit 210 and the first CFAR unit 211 (or represented as Doppler demultiplexing unit 212-1), and a second Doppler demultiplexing unit 212 (or represented as Doppler demultiplexing unit 212-2) that performs Doppler demultiplexing processing using the outputs of the second Doppler analysis unit 210-2 and the second CFAR unit 211. .

The q-th Doppler demultiplexing unit 212 (q=1, 2) receives information input from the q-th CFAR unit 211 (for example, distance index f _{b_cfar} (q), Doppler frequency index f _{s_cfar} (q), and received power information Based on PowerFT (f _{b_cfar} (q), f _{s_cfar} (q))), using the output from the q-th Doppler analysis unit 210, from the Doppler multiplexed signal (hereinafter referred to as “Doppler multiplexed signal”) , separates the transmission signal transmitted from each transmission antenna 106 (eg, the reflected wave signal for the transmission signal). The q-th Doppler demultiplexer 212 outputs, for example, information about the demultiplexed signal to the Doppler determiner 213 and the direction estimator 214 . Information about the separated signal includes, for example, a distance index f _{b_cfar} (q) corresponding to the separated signal, and a Doppler frequency index (hereinafter also referred to as separation index information) (f _{demul_Tx#1} (q), f _{demul_Tx#2} (q), …, f _{demul_Tx#Nt} (q)) may be included. The q-th Doppler demultiplexer 212 also outputs the output from the q-th Doppler analyzer 210 to the direction estimator 214 .

An operation example of the q-th Doppler demultiplexing unit 212 will be described below together with the operation of the Doppler shift unit 105 .

[How to set Doppler shift]
First, an example of a method for setting the Doppler shift amount given by the Doppler shift unit 105 will be described.

The Doppler shift units 105-1 to 105-Nt give different Doppler shift amounts DOP _n to the chirp signals input thereto. In one embodiment of the present disclosure, between Doppler shift units 105-1 to 105-Nt (for example, between transmitting antennas 106-1 to 106-Nt), the interval between Doppler shift amounts DOP _n (Doppler shift interval) is At least one Doppler interval is set to be different, not the interval.

For example, the n-th Doppler shifter 105 gives the input m-th and q-th chirp signals a phase rotation φ _n (m) with mutually different Doppler shift amounts DOP _n and outputs them. As a result, transmission signals transmitted from a plurality of transmission antennas 106 are given different Doppler shift amounts. For example, in one embodiment, Doppler multiplex N _DM =Nt. Here, m=an integer from 1 to N _C , n=an integer from 1 to Nt, and q=1,2.

In the q-th Doppler analysis unit 210, the range of the Doppler frequency _fd in which aliasing does not occur, which is derived from the sampling theorem, is -1/(2T _rs ) ≤ f _d <1/(2T _rs ).

For this reason, if a transmission signal transmitted from Nt transmission antennas 106 is transmitted, the phase rotation φ _n (m) at which the Doppler shift interval is equal to 1/(Nt×T _rs ) is given by the following equation ( 4).

where φ ₀ is the initial phase and Δφ ₀ is the reference Doppler shift phase. Also, round(x) is a round function that outputs a rounded integer value for the real value x. The term round(N _C /N _t ) is introduced for the purpose of setting the phase rotation amount to an integer multiple of the Doppler frequency interval in the Doppler analysis section 210 .

If, for example, the phase rotation φ _n (m) shown in Equation (4) is used, the phase rotation intervals between the transmission signals given to the m-th and q-th chirp signals are all equal and equal to 2πround (N _C /N _t )/N _C .

As an example, in equation (4), when phase rotation φ _n (m) is given with Nt=2, Δφ ₀ =0, φ ₀ =0, the Doppler shift amount is DOP ₁ =0, DOP ₂ =- 1/(2T _rs ).

For example, each interval of the Doppler shift amount given to the transmission signals transmitted from the plurality of transmission antennas 106 is the range of the Doppler frequency (for example, the Doppler frequency at which aliasing does not occur) in the radar device 10 (radar receiver 200). range)) at equal intervals. For example, the interval of the Doppler shift amount given to the transmission signals transmitted from Nt=2 transmission antennas 106 is the Doppler frequency range in which aliasing does not occur (for example, -1/(2T _rs ) ≤ f _d < 1/(2T _rs )) divided by the number of transmitting antennas 106 (for example, Nt=2) (1/(2T _rs ) in the above example). Thus, the Doppler interval between Doppler peak P1 and Doppler peak P2 is 1/(2T _rs ).

FIG. 5 shows DOP ₁ = 0, DOP ₂ = -1/(2T _rs ) is used, an example of a Doppler peak obtained by Doppler analysis (FFT) in the Doppler analysis unit 210 is shown.

As shown in FIG. 5, Nt (Nt=2 in FIG. 5) Doppler peaks are generated for one measured target Doppler frequency (target doppler) _{fd_TargetDoppler} .

Below, as an example, in FIG. 5, the transmission transmitted from the transmit antenna Tx#1 when the Doppler frequency of the target to be measured f _{d_TargetDoppler} = -1/(4T _rs ) and when f _{d_TargetDoppler} = 1/(4T _rs ) The positional relationship between the Doppler peak generated when receiving the reflected wave signal for the signal and the Doppler peak generated when receiving the reflected wave signal for the transmission signal from the transmitting antenna Tx#2 is compared.

<When target Doppler frequency f _{d_TargetDoppler} =-1/(4T _rs )>
When f _{d_TargetDoppler} =-1/(4T _rs ), as shown in FIG. 5, the Doppler peak generated when receiving the reflected wave signal for the transmission signal from the transmission antenna Tx#2 is the peak of the folded signal ( FFT output as P2A). Therefore, when f _{d_TargetDoppler} =1/(4T _rs ), as shown in FIG. This is the positional relationship with the Doppler peak (P2A) of the received signal. The Doppler interval between Doppler peak (P1) and Doppler peak (P2A) is 1/(2T _rs ). Note that the Doppler peak (P2') is the signal before aliasing and is shown for reference, but it does not actually exist in the FFT output.

<When target Doppler frequency f _{d_TargetDoppler} =1/(4T _rs )>
In the case of f _{d_TargetDoppler} =1/(4T _rs ), as shown in FIG. This is the positional relationship with the Doppler peak (P2) generated when the reflected wave signal for the transmission signal from 2 is received. The Doppler interval between Doppler peak (P1) and Doppler peak (P2) is 1/(2T _rs ).

Thus, when f _{d_TargetDoppler} =−1/(4T _rs ) and when f _{d_TargetDoppler} =1/(4T _rs ), the Doppler peak (P1) corresponding to transmit antenna Tx#1 and transmit antenna Tx The Doppler intervals between the Doppler peaks corresponding to #2 (P2 or P2A) are both 1/(2T _rs ). Therefore, f _{d_TargetDoppler} =−1/(4T _rs ) and 1/(4T _rs ) makes it impossible to distinguish the positional relationship of the Doppler peaks corresponding to Tx#1 and Tx#2, resulting in ambiguity. Thus, in the example shown in FIG. 5, the unambiguous target Doppler frequency range is, for example, −1/(4T _rs )≦ _{fd_TargetDoppler} <1/(4T _rs ).

On the other hand, as shown in FIG. 6, the Doppler shift unit 105 according to an embodiment of the present disclosure sets the Doppler shift amount that makes the Doppler multiplexing interval unequal. For example, the Doppler shift unit 105 may assign Doppler shift amounts at intervals obtained by dividing the Doppler frequency range for which the Doppler frequency folding count is determined into uneven intervals. For example, in the Doppler shifter 105, the interval of the Doppler shift amount DOP _n (or the phase rotation φ _n (m)) given to the transmission signal transmitted from the transmission antenna 106 differs by at least one.

Further, for example, the Doppler shift unit 105 separates the intervals of the Doppler shift amounts imparted to the transmission signals transmitted from the Nt transmission antennas 106 as much as possible, and at least one interval of the phase rotation φ _n (m) is Apply the Doppler shift DOP _n differently. As a result, the separation performance of Doppler multiplexing can be improved.

For example, the n-th Doppler shift unit 105 has a different Doppler shift amount DOP _n between the respective Doppler shift units for the input m-th first chirp signal or second chirp signal. Give the phase rotation φ _n (m) as in (5).

Here, A is a coefficient that gives a positive/negative polarity of 1 or -1. δ is an integer of 1 or more. Note that the term round (N _C / (Nt + δ)) is introduced for the purpose of setting the phase rotation amount to an integer multiple of the Doppler frequency interval in the Doppler analysis unit 210, but is not limited to this, and the expression (5 ), 2π/(Nt+δ) may be used instead of the term (2π/N _C )×round(N _C /(Nt+δ)).

For example, the radar apparatus 10 performs unequal interval Doppler multiplexing on the first chirp signal and the second chirp signal at the same Doppler multiplexing interval.

As an example, in Equation (5), when Nt=2, Δφ ₀ =0, φ ₀ =0, A=1, δ=1, N _C is a multiple of 3 and phase rotation φ _n (m) is given , the Doppler shift amounts are DOP ₁ =0 and DOP ₂ =1/(3T _rs ).

FIG. 6 shows DOP ₁ =0 and DOP 2 =1/(3T _rs ) for transmission signals transmitted from Nt=2 transmission antennas 106 (hereinafter referred to as Tx#1 and Tx# ₂ ). An example of a Doppler peak obtained by Doppler analysis in the Doppler analysis unit 210 when the Doppler shift amount is used is shown.

As shown in FIG. 6, Nt (Nt=2 in FIG. 6) Doppler peaks are generated for one measured target Doppler frequency (target doppler) _{fd_TargetDoppler} .

As an example, FIG. 6 shows the output of the Doppler analysis unit 210 when the Doppler frequency of the target to be measured is f _{d_TargetDoppler} = -1/(4T _rs ) and when f _{d_TargetDoppler} = 1/(4T _rs ). Doppler peak generated when receiving a reflected wave signal for the transmission signal transmitted from Tx#1, Doppler peak generated when receiving a reflected wave signal for the transmission signal transmitted from the transmitting antenna Tx#2, Compare the positional relationship of

<When target Doppler frequency f _{d_TargetDoppler} = -1/(4T _rs )>
When f _{d_TargetDoppler} = -1/(4T _rs ), as shown in FIG. 6, the Doppler peak (P1) generated when receiving the reflected wave signal for the transmission signal from the transmission antenna Tx#1 and the transmission antenna Tx This is the positional relationship with the Doppler peak (P2) generated when the reflected wave signal for the transmission signal from #2 is received. The Doppler interval between Doppler peak P1 and Doppler peak P2 is 1/(3T _rs ).

<When target Doppler frequency f _{d_TargetDoppler} = 1/(4T _rs )>
When f _{d_TargetDoppler} = 1/(4T _rs ), as shown in Fig. 6, the Doppler peak generated when receiving the reflected wave signal for the transmission signal from the transmission antenna Tx#2 is the peak of the folded signal (P2A ) is output as FFT. Therefore, when f _{d_TargetDoppler} = 1/(4T _rs ), the Doppler peak (P1) generated when receiving the reflected wave signal for the transmitted signal from the transmitting antenna Tx#1 and the Doppler peak (P2A ). The Doppler interval between Doppler peak (P1) and peak (P2A) is 2/(3T _rs ).

As _shown in _FIG . 6 _, the _Doppler peak ( P1) and the Doppler peak (P2 or P2A) corresponding to the transmitting antenna Tx#2 are different from each other.

Therefore, in the example shown in FIG. 6, the Doppler demultiplexing unit 212 performs the target Doppler frequency f _{d_TargetDoppler} =−1/(4T _rs ) (for example, when there is no aliasing) and f _{d_TargetDoppler} =1/(4T _rs ) (for example, with wrapping).

For example, when the assumed target Doppler frequency is -1/(2T _rs ) ≤ f _{d_TargetDoppler} < 1/(2T _rs ), the Doppler demultiplexing unit 212 performs the target Doppler frequency f _{d_TargetDoppler} = -1/(4T _rs ). case, it can be determined that the return signal is not included. Therefore, for example, in the case of f _{d_TargetDoppler} = -1/(4T _rs ) shown in FIG. 6, the Doppler demultiplexing unit 212 does not include the aliasing signal, and from the Doppler peak with the lowest frequency, the transmission antennas Tx#1 and Tx It can be determined that it is the reflected wave signal for the transmission signal from #2.

Further, for example, when the assumed target Doppler frequency is -1/(2T _rs ) ≤ f _{d_TargetDoppler} < 1/(2T _rs ), the Doppler demultiplexing unit 212 sets the target Doppler frequency f _{d_TargetDoppler} = 1/(4T _rs ) , it can be determined that a folded Doppler peak (for example, P2A) is included, and it can be determined that the Doppler frequency f _{d_TargetDoppler} = 1/(4T _rs ). Therefore, for example, when f _{d_TargetDoppler} =1/(4T _rs ) shown in FIG. 6, the aliasing signal (P2A) is included, so the Doppler demultiplexing unit 212 sets the Doppler peak interval to 2/(3T _rs ). It can be determined that the higher Doppler peak is the reflected wave signal corresponding to the transmitting antenna Tx#1, and the lower Doppler peak is the reflected wave signal corresponding to the transmitting antenna Tx#2. Although P1′ and P2′ are shown in FIG. 6 for ease of explanation, they do not actually exist in the output of the Doppler analysis section 210 .

Next, as another example, in FIG. 6, when the Doppler frequency of the target to be measured f _{d_TargetDoppler} = -1/(2T _rs ) and when f _{d_TargetDoppler} = 1/(2T _rs ), transmission from the transmission antenna Tx#1 Compare the positional relationship between the Doppler peak generated when receiving the reflected wave signal for the transmitted signal transmitted from transmitting antenna Tx#2 and the Doppler peak generated when receiving the reflected wave signal for the transmitted signal transmitted from transmitting antenna Tx#2 do.

<When target Doppler frequency f _{d_TargetDoppler} = -1/(2T _rs )>
When f _{d_TargetDoppler} = -1/(2T _rs ), as shown in FIG. 6, the Doppler peak (P1) generated when receiving the reflected wave signal for the transmission signal from the transmission antenna Tx#1 and the transmission antenna Tx This is the positional relationship with the Doppler peak (P2) generated when the reflected wave signal for the transmission signal from #2 is received. The Doppler interval between Doppler peak (P1) and Doppler peak (P2) is 1/(3T _r ).

<When target Doppler frequency f _{d_TargetDoppler} =1/(2T _rs )>
When f _{d_TargetDoppler} =1/(2T _rs ), as shown in FIG. 6, the Doppler peak generated when receiving the reflected wave signal for the transmission signal from the transmission antenna Tx#1 is the Doppler peak of the folded signal ( P1A) is FFT-output, and the Doppler peak generated when receiving the reflected wave signal for the transmission signal from the transmitting antenna Tx#2 is FFT-output as the Doppler peak (P2A) of the folded signal. Therefore, there is a positional relationship between the Doppler peak (P1A) generated when the reflected wave signal for the transmission signal from the transmission antenna Tx#1 is received and the Doppler peak (P2A) of the folded signal. The Doppler interval between Doppler peak (P1A) and Doppler peak (P2A) is 1/(3Tr).

Thus, when the target Doppler frequency f _{d_TargetDoppler} =−1/(2T _rs ) and when f _{d_TargetDoppler} =1/(2T _rs ), the Doppler peak (P1) corresponding to the transmitting antenna Tx#1 and , and the Doppler peak (P2 or P2A) corresponding to transmit antenna Tx#2 are both 1/(3T _rs ). Therefore, in the case of f _{d_TargetDoppler} =－1/(2T _rs ) and f _{d_TargetDoppler} =1/(2T _rs ), the positional relationship of the Doppler peaks corresponding to Tx#1 and Tx#2 becomes indistinguishable, resulting in ambiguity. occurs. Therefore, in the example shown in FIG. 6, the target Doppler frequency range where no ambiguity occurs in the Doppler demultiplexer 212 is, for example, −1/(2T _rs )≦f _{d_TargetDoppler} <1/(2T _rs ).

Therefore, in the Doppler shift setting of FIG. 6, the target Doppler frequency range that does not cause ambiguity is compared with time division multiplexing or Doppler multiplexing where the Doppler shift amount is evenly spaced (see, for example, FIG. 5). can be enlarged Nt times (for example, twice in FIG. 6).

In the present embodiment, a method of further expanding the Doppler frequency range of the target in which ambiguity does not occur by processing of the Doppler determination unit 213, which will be described later, will be described.

Next, an example of a method of separating signals corresponding to each transmitting antenna 106 in Doppler demultiplexing section 212 will be described.

As an example, the operation of the Doppler demultiplexing unit 212 when Nt=2 will be described.

In the following, the case where the Doppler shift unit 105 gives the phase rotation φ _n (m) shown in Equation (5) will be described as an example. In the following description, Δφ ₀ =0, φ ₀ =0, δ=1, and _NC is a multiple of 3 as an example. When A=1, the Doppler shift for each transmit antenna 106 is _DOP1 =0, _DOP2 =1/( _3Tr ), and when A=-1, the Doppler shift for each transmit antenna 106 is _DOP1. = 0, _DOP2 = -1/(3T _r ).

In this case, the q-th Doppler demultiplexing unit 212 uses the peak (distance index f _{b_cfar} (q) and Doppler frequency index f _{s_cfar} (q)) with received power greater than the threshold input from the q-th CFAR unit 211 to , separate the Doppler multiplexed signals.

For example, the q-th Doppler demultiplexing unit 212 generates transmission signals transmitted from transmission antennas Tx#1 to Tx#Nt for a plurality of Doppler frequency indexes f _{s_cfar} (q) having the same distance index f _{b_cfar} (q). It is determined which one of the above the reflected wave signal corresponds to. The Doppler demultiplexing unit 212 separates and outputs the determined reflected wave signals for each of the transmitting antennas Tx#1 to Tx#Nt.

The following describes the operation when there are Ns multiple Doppler frequency indexes _{fs_cfar} (q) with the same distance index _{fb_cfar} (q). For example, let f _{s_cfar} (q)∈{fd _#1 , fd _{#2 .} . . , fd _#Ns }.

Here, Nt=2 Doppler shift amounts for one target Doppler frequency _{fd_TargetDoppler} are obtained by the Doppler shift amounts DOP ₁ and DOP ₂ given to the transmission signals respectively transmitted from the transmission antennas Tx#1 and Tx#2. A peak occurs. The Doppler index interval corresponding to the Doppler interval between Doppler peaks is the phase rotation φ ₁ (m) for transmitting antenna Tx#1 and the phase rotation φ ₂ (m) for transmitting antenna Tx#2 shown in the following equation (6). From the difference of , it becomes round(N _c /(Nt+1)). Also, when a folding signal is included, the Doppler index interval corresponding to the Doppler interval between Doppler peaks is N _c -round(N _c /(Nt+1)).

For example, the q-th Doppler demultiplexing unit 212 uses the distance index f_{b_cfar}Multiple Doppler frequency indices f with the same (q)_{s_cfar}(q) ∈{fd_#1,fd_#2…,fd_#Ns}, the Doppler index interval is calculated. Then, the q-th Doppler demultiplexing unit 212 calculates the Doppler index interval round(N_c/(Nt+1)), or the Doppler index interval (N_c-round(N_c/(Nt+1))).

The q-th Doppler demultiplexing unit 212 performs the following processing based on the search results described above.

(1) When there is a Doppler frequency index that matches the index interval round(N _c /(Nt+1)) corresponding to the interval of the Doppler shift amount when no aliasing signal is included, the q-th Doppler demultiplexing unit 212 These Doppler frequency index pairs (for example, fd _#p and fd _#q ) are output as separation index information (f _{demul_Tx#1} (q), f _{demul_Tx#2} (q)) of Doppler multiplexed signals.

Here, when the Doppler shift amounts for the transmitting antennas Tx#1 and Tx#2 are in a relationship of DOP ₁ <DOP ₂ , the q-th Doppler demultiplexing unit 212 selects the larger one of fd _#p and fd _#q as Tx# 2 is determined as the Doppler frequency index f _{demul_Tx#2} (q), and the lower one is determined as the Doppler frequency index f _{demul_Tx#1} (q) corresponding to Tx#1. On the other hand, when the Doppler shift amounts for the transmitting antennas Tx#1 and Tx#2 have a relationship of DOP ₁ > DOP ₂ , the Doppler demultiplexing unit 212 assigns the larger one of fd _#p and fd _#q to Tx#1. Doppler frequency index f _{demul_Tx#1} (q) corresponding to Tx#2, and the lower one is determined as Doppler frequency index f _{demul_Tx#2} (q) corresponding to Tx#2.

(2) If there is a Doppler frequency index that matches the index interval N _c -round (N _c /(Nt+1)) corresponding to the interval of the Doppler shift amount when the folded signal is included, the q-th Doppler demultiplexing unit 212 outputs these Doppler frequency index pairs (eg, fd _#p , fd _#q ) as separation index information (f _{demul_Tx#1} (q), f _{demul_Tx#2} (q)) of Doppler multiplexed signals.

Here, when the Doppler shift amounts for the transmitting antennas Tx#1 and Tx#2 are in a relationship of DOP ₁ <DOP ₂ , the q-th Doppler demultiplexing unit 212 selects the larger one of fd _#p and fd _#q as Tx# The Doppler frequency index f _{demul_Tx#1} (q) corresponding to 1 is determined, and the lower one is determined as the Doppler frequency index f _{demul_Tx#2} (q) corresponding to Tx#2. On the other hand, when the Doppler shift amounts for the transmitting antennas Tx#1 and Tx#2 have a relationship of DOP ₁ >DOP ₂ , the q-th Doppler demultiplexing unit 212 selects the larger one of fd _#p and fd _#q as Tx#2 and the lower one is determined as the Doppler frequency index f demul_Tx _{# 1} (q) corresponding to Tx#1.

(3) Doppler frequency index matching the index interval round(N _c /(Nt+1)) corresponding to the interval of the Doppler shift amount when no aliasing signal is included, and the Doppler shift amount when including the aliasing signal If there is no Doppler frequency index matching the index interval N _c -round(N _c /(Nt+1)) corresponding to the interval, the q-th Doppler demultiplexer 212 determines that the generated Doppler peak is a noise component. In this case, the Doppler demultiplexing unit 212 may omit outputting the demultiplexing index information (f _{demul_Tx#1} (q), f _{demul_Tx#2} (q)) of the Doppler multiplexed signal.

As described above, the q-th Doppler demultiplexing unit 212 can demultiplex the Doppler multiplexed signal.

Although the Doppler multiplexing operation example in the case of Nt=2 has been described, the number of transmission antennas Nt is not limited to two, and may be three or more. As another example, the operation of the radar device 10 when Nt=3 will be described below.

In the following, the case where the Doppler shift unit 105 gives the phase rotation φ _n (m) shown in Equation (5) will be described as an example. In the following, as an example, Δφ ₀ =0, φ ₀ =0, A=1, and δ=1. In this case, the Doppler shifts for each transmit antenna 106 are DOP ₁ =0, DOP ₂ =1/(4T _rs ), DOP ₃ =−1/(2T _rs ).

When such a Doppler shift amount is used, for example, as shown in FIG. 7, Nt (three in FIG. 7) Doppler peaks are generated for one target Doppler frequency _{fd_TargetDoppler} to be measured. FIG. 7 is a diagram showing changes in the Doppler peak at Nt=3 when the horizontal axis indicates the target Doppler frequency and the vertical axis indicates the output of the q-th Doppler analysis unit 210 (FFT).

<When the target Doppler frequency is 0≦ f _{d_TargetDoppler} <1/(2T _rs )>
As shown in FIG. 7, the Doppler peak (solid line) generated when the reflected wave signal for the transmission signal from the transmitting antenna Tx#1 is received and the reflected wave signal for the transmission signal from the transmitting antenna Tx#3 are received. The Doppler interval between the Doppler peak (dashed-dotted line) occurring at the time is 1/(2T _rs ). Also, in this case, since none of the transmitting antennas Tx#1, Tx#2, and Tx#3 include aliasing signals in 0≦f _{d_TargetDoppler} <1/(4T _rs ), the q-th Doppler demultiplexing unit 212 , and low-frequency Doppler peaks, it can be determined that they are reflected wave signals for the transmission signals from the transmission antennas Tx#3, Tx#1, and Tx#2.

Also in this case, 1/(4T _rs )≦f _{d_TargetDoppler} <1/(2T _rs ) contains the folding signal for Tx#2. Therefore, the q-th Doppler demultiplexing unit 212 determines that the higher Doppler peak (solid triangle) among the Doppler peaks with a Doppler peak interval of 1/(2T _rs ) is the reflected wave signal corresponding to the transmitting antenna Tx#1. It can be determined that the lower Doppler peak (solid line square) is the reflected wave signal corresponding to the transmitting antenna Tx#3, and the remaining Doppler peak is the reflected wave signal from the transmitting antenna Tx#2.

<When the target Doppler frequency is -1/(2T _rs ) ≤ f _{d_TargetDoppler} <0>
As shown in FIG. 7, since Tx#1 includes a return signal, the Doppler peak (solid line) generated when receiving the reflected wave signal for the transmission signal from the transmission antenna Tx#1 and the Doppler peak from the transmission antenna Tx#2 The Doppler interval between the Doppler peak (dotted line) generated when the reflected wave signal for the transmitted signal is received is 1/(4T _rs ). Also, the Doppler peak (dotted line) generated when receiving the reflected wave signal for the transmission signal from transmitting antenna Tx#2 and the Doppler peak generated when receiving the reflected wave signal for the transmission signal from transmitting antenna Tx#3 The Doppler spacing between peaks (constant dashed line) is 1/(4T _rs ).

Also, in this case, since a folding signal is included for the transmitting antenna Tx#1, the q-th Doppler demultiplexing unit 212 starts from the low-frequency Doppler peak, and the signals from the transmitting antennas Tx#1, Tx#2, and Tx#3 are respectively It can be determined that it is a reflected wave signal for a transmission signal.

Thus, in the example shown in FIG. 7, the unambiguous target Doppler frequency range is, for example, −1/(2T _rs )≦ _{fd_TargetDoppler} <1/(2T _rs ).

Next, an example of a method of separating signals corresponding to each transmitting antenna 106 in the q-th Doppler demultiplexing section 212 will be described.

In the following, the case where the Doppler shift unit 105 gives the phase rotation φ _n (m) shown in Equation (5) will be described as an example. In the following, Nt=3, Δφ ₀ =0, φ ₀ =0, δ=1, and _NC is a multiple of 3 as an example. When A=1, the amount of Doppler shift for each transmit antenna 106 is DOP ₁ =0, DOP ₂ =1/(4T _rs ), DOP ₃ =1/(2T _rs )=−1/(2T _rs ). , A=−1, the Doppler shifts for each transmit antenna 106 are DOP ₁ =0, DOP ₂ =−1/(4T _rs ), DOP ₃ =−1/(2T _rs ).

The q-th Doppler demultiplexing unit 212 uses peaks (distance index f _{b_cfar} (q) and Doppler frequency index f _{s_cfar} (q)) with received power greater than the threshold input from the q-th CFAR unit 211 to perform Doppler multiplexing. Perform signal separation.

For example, the q-th Doppler demultiplexing unit 212 generates transmission signals transmitted from transmission antennas Tx#1 to Tx#Nt for a plurality of Doppler frequency indexes _{fs_cfar} (q) having the same distance index _{fb_cfar} (q). It is determined which one of the above the reflected wave signal corresponds to. The q-th Doppler demultiplexer 212 separates and outputs the determined reflected wave signals for each of the transmitting antennas Tx#1 to Tx#Nt.

The following describes the operation when there are Ns multiple Doppler frequency indexes _{fs_cfar} (q) with the same distance index _{fb_cfar} (q). For example, let f _{s_cfar} (q)∈{fd _#1 , fd _{#2 .} . . , fd _#Ns }.

For example, the q-th Doppler demultiplexing unit 212, for a plurality of Doppler frequency indexes _{fs_cfar} (q)ε{fd _#1 , fd _#2 . . . , fd _#Ns } with the same distance index f _{b_cfar} (q), Calculate the Doppler index interval. Then, in the q-th Doppler demultiplexing unit 212, the two Doppler index intervals when viewing the three Doppler frequency indexes in ascending order match the index interval corresponding to the interval of the Doppler shift amount when no aliasing signal is included. Search for combinations of Doppler frequency indices. Alternatively, the q-th Doppler demultiplexing unit 212 performs a Doppler index interval in which two Doppler index intervals when viewing the three Doppler frequency indexes in ascending order match the index interval corresponding to the interval of the Doppler shift amount when aliasing signals are included. Search for frequency index combinations.

The q-th Doppler demultiplexing unit 212 performs the following processing based on the search results described above.

(1) If there is a combination of Doppler frequency indexes that does not include aliased signals and matches the index interval corresponding to the interval of the Doppler shift amount, the q-th Doppler demultiplexing unit 212 generates a pair of Doppler frequency indexes (for example, fd _#p1 , fd _#p2 , fd _#p3 ) are output as separation index information of Doppler multiplexed signals (f _{demul_Tx#1} (q), f _{demul_Tx#2} (q), f _{demul_Tx#3} (q)) do.

Here, if the Doppler shift amounts for the transmitting antennas Tx#1 to Tx#3 have a relationship of DOP ₃ <DOP ₁ <DOP ₂ , the q-th Doppler demultiplexing unit 212 performs fd _#p1 , fd _#p2 , fd _#p3 Determine the Doppler frequency index f _{demul_Tx#2} (q), f _{demul_Tx#1} (q), f demul_Tx#3 (q) corresponding to Tx#2, Tx#1, and Tx _#3 from the larger one (0≦ _{fd_TargetDoppler} <1/(4T _rs ) in FIG. 7). Also, when the Doppler shift amounts for the transmitting antennas Tx#1 to Tx#3 have a relationship of DOP ₁ >DOP ₂ >DOP ₃ , the q-th Doppler demultiplexing unit 212 performs fd _#p1 , fd _#p2 , and fd _#p3 . The Doppler frequency indexes f _{demul_Tx#1} (q), f _{demul_Tx#2} (q), and f _{demul_Tx#3 (q) corresponding to Tx#1, Tx#2, and Tx#3} are determined from the larger one.

(2) If there is a combination of Doppler frequency indices that includes a folded signal and matches the index interval corresponding to the interval of the Doppler shift amount, the q-th Doppler demultiplexer 212 demultiplexes those Doppler frequency index pairs (for example, fd _#q1 , fd _#q2 , fd _#q3 ) are output as separation index information of Doppler multiplexed signals (f _{demul_Tx#1} (q), f _{demul_Tx#2} (q), f _{demul_Tx#3} (q)) .

For example, if there is a combination of Doppler frequency indexes where the Doppler shift amounts for the transmitting antennas Tx#1 to Tx#3 are DOP ₃ <DOP ₁ <DOP ₂ and the Doppler frequency corresponding to DOP ₃ is a folding signal, The q-th Doppler demultiplexing unit 212 performs Doppler frequency index f _{demul_Tx#2} (q) corresponding to Tx _# 3, Tx#2, and Tx#1 from the larger one of fd _#q1 , fd _#q2 , and fd #q3. , f _{demul_Tx#1} (q), f _{demul_Tx#3} (q) (-1/(2T _rs )≦ _{fd_TargetDoppler} <0 in FIG. 7). Further, when the Doppler shift amounts for the transmitting antennas Tx#1 to Tx#3 have a relationship of DOP ₁ > DOP ₂ > DOP ₃ , and there is a combination of Doppler frequency indexes where the Doppler frequency corresponding to DOP ₃ is a folding signal, The q-th Doppler demultiplexing unit 212 selects f _{demul_Tx#2} (q), f demul_Tx corresponding to Tx _# 3, Tx#1, and Tx _# 2 from the larger one of fd _#q1 , fd #q2 , and fd _#q3 . _#3 (q), f _{demul_Tx#1} (q).

(3) If there is a combination of Doppler frequency indexes that include aliased signals and match the index interval corresponding to the interval of the Doppler shift amount, the q-th Doppler demultiplexer 212 demultiplexes those Doppler frequency index pairs (for example, fd _#u1 , fd _#u2 , and fd _#u3 ) are output as separation index information (f _{demul_Tx#1} (q), f _{demul_Tx#2} (q), f _{demul_Tx#3} (q)) of Doppler multiplexed signals .

Here, when the amount of Doppler shift for the transmitting antennas Tx#1 to Tx#3 has a relationship of DOP ₃ < DOP ₁ < DOP ₂ , and there is a combination of Doppler frequency indexes where the Doppler frequency corresponding to DOP ₂ is a folding signal. , the q-th Doppler demultiplexing unit 212 selects fd _#u1 , fd _#u2 , fd _#u3 from the larger one to f _{demul_Tx#3} (q), f Determine _{demul_Tx#2} (q), f _{demul_Tx#1} (q) (1/(4T _rs )≦ _{fd_TargetDoppler} <1/(2T _rs ) in FIG. 7).

Further, when the Doppler shift amounts for the transmitting antennas Tx#1 to Tx#3 are in a relationship of DOP ₁ > DOP ₂ > DOP ₃ , and there is a combination of Doppler frequency indexes where the Doppler frequency corresponding to DOP ₁ is a folding signal, The q-th Doppler demultiplexing unit 212 performs f _{demul_Tx#3} (q), f _{demul_Tx} corresponding to Tx _# 2, Tx#3, and Tx _# 1 from the larger one of fd _#u1 , fd #u2 , and fd #u3 _#1 (q), f _{demul_Tx#2} (q).

(4) The q-th Doppler demultiplexer 212 determines a Doppler peak corresponding to a Doppler frequency index that does not correspond to any of (1), (2), and (3) above to be a noise component. In this case, the q-th Doppler demultiplexing unit 212 omits outputting the demultiplexing index information (f _{demul_Tx#1} (q), f _{demul_Tx#2} (q), f _{demul_Tx#3} (q)) of the Doppler multiplexed signal. You may

As described above, the Doppler demultiplexing unit 212 can demultiplex the Doppler multiplexed signal.

Also, the case of using the phase rotation φ _n (m) shown in Equation (5) has been described as an example of the phase rotation corresponding to the Doppler shift amount DOP _n imparted to the transmission signal. However, the phase rotation is not limited to the phase rotation φ _n (m) shown in Equation (5).

As another example, the n-th Doppler shift unit 105, with respect to the input m-th chirp signal (transmission signal), the following equation that becomes a Doppler shift amount DOP _n different from the case of using equation (5) The phase rotation φ _n (m) of (7) may be given. Note that the term round (N _C / (Nt + δ)) is introduced for the purpose of setting the phase rotation amount to an integral multiple of the Doppler frequency interval in the Doppler analysis unit 210, but is not limited to this, and the expression (7 ), 2π/Nt may be used instead of the (2π/N _C )×round(N _C /Nt) term.

where dp _n is the component that makes the phase rotation unequally spaced in the Doppler frequency range. _{For example ,} dp ₁ , dp 2 _{, .} but at least one contains components with different values. The term round(N _C /Nt) is introduced for the purpose of setting the amount of phase rotation to be an integral multiple of the Doppler frequency interval in Doppler analysis section 210 .

As an example, in equation (7), when Nt=2, Δφ ₀ =0, φ ₀ =0, A=1, dp ₁ =0, and dp ₂ =π/5, the phase rotation _φn (m) is When applied, the amount of Doppler shift is DOP ₁ =0, DOP ₂ =1/(2T _rs )+1/(10T _rs )=6/(10T _rs )=−4/(10T _rs ).

FIG. 8 shows the _target Doppler frequency on the horizontal axis and the output of the Doppler analysis unit ₂₁₀ (FFT) on the vertical _axis . FIG. 4 is a diagram showing changes in Doppler peak; In this case, _DOP1 > _DOP2 .

<If the target Doppler frequency is -1/(10T _rs ) ≤ _{fd_TargetDoppler} <1/(2T _rs )>
As shown in FIG. 8, the Doppler peak (solid line) generated when the reflected wave signal for the transmission signal from the transmitting antenna Tx#1 is received, and the reflected wave signal for the transmission signal from the transmitting antenna Tx#2 are received. The Doppler spacing between the Doppler peaks (dotted lines) occurring at the time is 4/(10T _rs ).

Also, in this case, none of the transmitting antennas Tx#1 and Tx#2 contain the return signal.
Therefore, the q-th Doppler demultiplexing unit 212 determines that the higher Doppler peak (solid triangle) among the Doppler peaks with a Doppler peak interval of 4/(10T _rs ) is the reflected wave signal corresponding to the transmitting antenna Tx#1. It can be determined that the lower Doppler peak (solid line square) is the reflected wave signal corresponding to the transmitting antenna Tx#2.

<When the target Doppler frequency is -1/(2T _rs ) ≤ _{fd_TargetDoppler} < -1/(10T _rs )>
As shown in FIG. 8, the Doppler peak (solid line) generated when the reflected wave signal for the transmission signal from the transmitting antenna Tx#1 is received, and the reflected wave signal for the transmission signal from the transmitting antenna Tx#2 are received. The Doppler spacing between the Doppler peaks (dotted lines) occurring at the time is 6/(10T _rs ).

Also, in this case, a folding signal is included for Tx#2 (solid line circle). Therefore, the q-th Doppler demultiplexer 212 can determine, for example, from the low-frequency Doppler peaks (dotted-line triangles) that they are reflected wave signals for the transmission signals from the transmission antennas Tx#1 and Tx#2.

Thus, in the example shown in FIG. 8, the unambiguous target Doppler frequency range is, for example, −1/(2T _rs )≦ _{fd_TargetDoppler} <1/(2T _rs ).

An operation example of the Doppler demultiplexing unit 212 has been described above. In the above description of the operation example of the Doppler demultiplexing unit 212, the radar apparatus 10 performs unequal Doppler multiplexing on the first chirp signal and the second chirp signal at the same (unequal division) Doppler multiplexing interval. However, the radar device 10 is not limited to this, and the radar device 10 uses different parameters such as different (unequal division) Doppler multiplexing intervals for the first chirp signal and the second chirp signal. Equidistant Doppler multiplexing may be performed.

For example, when Nt=2, the Doppler shift unit 105 sets the Doppler shift amount for each transmitting antenna 106 to DOP ₁ =0 and DOP ₂ =1/(3T _r ) for the first chirp signal, and the second chirp signal For the signal, in Doppler shift section 105, the amount of Doppler shift for each transmitting antenna 106 is set to DOP ₁ =0 and DOP ₂ =1/(4T _r ), and the Doppler multiplexing interval is different between the first chirp signal and the second chirp signal. Unequally spaced Doppler multiplexing may be performed using the parameters as follows.

Alternatively, for example, when Nt=2, for the first chirp signal, the Doppler shift unit 105 sets the Doppler shift amount for each transmitting antenna 106 to DOP ₁ =0 and DOP ₂ =1/(3T _r ), and For the two chirp signals, the Doppler shift unit 105 sets the Doppler shift amount for each transmitting antenna 106 to DOP ₁ =1/(4T _r ) and DOP ₂ =−1/(2T _r ), the first chirp signal and the second chirp signal. Unequally spaced Doppler multiplexing may be performed using parameters that provide different Doppler multiplexing intervals between chirp signals.

Even in such a case, in the radar receiver 200, the first chirp signal is processed by the first Doppler analyzer 210 and the first Doppler demultiplexer 212, and the second chirp signal is processed by the second Since the Doppler analysis unit 210 and the second Doppler demultiplexing unit 212 process independently of each other, the operation described above can be applied. In this way, in the radar apparatus 10, each chirp signal is received and processed individually, so that it is possible to omit sharing the parameters for performing unequal interval Doppler multiplexing among the chirp signals.

In FIG. 2, Doppler determination section 213 determines the Doppler frequency corresponding to the Doppler peak based on the outputs of first Doppler demultiplexer 212 and second Doppler demultiplexer 212 . For example, the Doppler determination unit 213 determines that even if the Doppler frequency _{fd_TargetDoppler} of the target includes a target with a Doppler frequency exceeding the Doppler frequency range −1/(2T _rs )≦ _{fd_TargetDoppler} <1/(2T _rs ), By determining the target Doppler frequency, the Doppler detection range can be further expanded.

For _example , the Doppler determination unit 213 uses separation index information (f _{demul_Tx #1} (1), f _{demul_Tx#2} (1), ..., f _{demul_Tx#Nt} (1)) and separation index information (f _{demul_Tx#1} (2 ), f _{demul_Tx#2} (2), ..., f _{demul_Tx#Nt} (2)) for Doppler frequencies over the Doppler frequency range -1/(2T _rs ) ≤ f _{d_TargetDoppler} < 1/(2T _rs ) Determine the Doppler frequency of a target containing

Determination of the Doppler frequency in the Doppler determination unit 213 is performed by the first chirp signal and the second chirp signal, which are radar transmission signals generated by the signal generation control unit 104 and the radar transmission signal generation unit 101, and have different center frequencies. take advantage of that.

The operation principle of the Doppler frequency determination process and an operation example of the Doppler determination unit 213 will be described below.

In the following description, the Doppler determination unit 213 uses Doppler multiplexing signals output from the first Doppler demultiplexing unit 212 and the second Doppler demultiplexing unit 212, in which the distance indexes f _{b_cfar} (1) and f _{b_cfar} (2) are common. An example of performing processing using signal separation index information will be described. Therefore, hereinafter, the distance index is abbreviated as “f _{b_cfar} ” (=f _{b_cfar} (1)=f _{b_cfar} (2)).

For example, if the center frequency of the first chirp signal differs from the center frequency of the second chirp signal, the Doppler frequency of the reflected wave also changes. For example, when the radar device 10 is stationary and the target moves toward the radar device 10 at a speed v, the Doppler frequency f _d (1) observed using the first chirp signal is f _d (1)=2v×f _c (1)/C ₀ , and the Doppler frequency f _d (2) observed using the second chirp signal is f _d (2)=2v×f _c (2)/C becomes ₀ . Therefore, the relationship between both Doppler frequencies is expressed as f _d (2)/f _d (1)=f _c (2)/f _c (1). For example, f _d (2) can be calculated by multiplying f _d (1) by the center frequency ratio f _c (2)/f _c (1) (f _d (2)=(f _c (2)/ f _c (1))×f _d (1)). where C ₀ represents the speed of light.

Also, for example, it is assumed that the target Doppler frequency f _{d_TargetDoppler} exceeds the Doppler frequency range −1/(2T _rs )≦f _{d_TargetDoppler} <1/(2T _rs ), and the first Doppler analysis unit 210 and the first Doppler demultiplexing When the Doppler frequency estimate value detected in section 212 is f _{d_VFT} (1), the Doppler frequency f _{d_TargetDoppler} of the target is expressed by the following equation (8) in consideration of Doppler aliasing. Here, n _al represents the number of times of Doppler folding and takes an integer value.
f _{d_TargetDoppler} = f _{d_VFT} (1) + n _al /T _rs (8)

Since it is difficult to determine the number of Doppler folding times n _al from the outputs of the first Doppler analysis unit 210 and the first Doppler demultiplexing unit 212, the outputs of the second Doppler analysis unit 210 and the second Doppler demultiplexing unit 212 are The conditions that can be determined using Here, the Doppler frequency observed using the second chirp signal is obtained by multiplying the center frequency ratio f _c (2)/f _c (1) by the formula (8) as shown in the following formula (9). can get.
_fc (2)/ _fc (1)× _{fd_TargetDoppler} = _fc (2)/ _fc (1)×( _{fd_VFT} (1)+ _nal / _Trs ) (9)

For example, the Doppler frequency observed using the second chirp signal is f _c (2)/f _c (1)×f _{d_VFT} (1) when the Doppler folding number n _al =0, and the Doppler folding number n f _c (2)/f _c (1)×(f _{d_VFT} (1)+1/T _rs ) when al =1, and f _c (2) when the _Doppler aliasing number n _al =-1 /f _c (1)×(f _{d_VFT} (1)-1/T _rs ). The same applies to other Doppler folding times.

In this way, the Doppler frequency difference due to the difference in the number of Doppler folding times n _al has a relationship of being an integer multiple of f _c (2)/f _c (1) / _Trs .

Here, the difference between f _c (2)/f _c (1) /T _rs and 1/T _rs , which is the folding frequency interval of the second Doppler analysis unit 210, is the Doppler frequency resolution in the second Doppler analysis unit 210. If it is larger than Δf _d , the Doppler determination unit 213 can detect (for example, determine) the Doppler frequency difference due to the difference in the number of Doppler folding times n _al .

Therefore, for example, the radar device 10 (for example, the signal generation control unit 104) sets the center frequency f _c ( 1) and the center frequency f _c (2) of the second chirp signal may be determined.

Here, for example, when f _c (2)>f _c (1), the determination condition for f _c (1) and f _c (2) shown in equation (10) is expressed by the following equation (11) .

Further, for example, when f _c (2)<f _c (1), the determination condition for f _c (1) and f _c (2) shown in equation (10) is expressed by the following equation (12).

Alternatively, for example, the determination condition shown in the following equation (13) may be used. However, α≧1.

Equation (13) expresses that the difference between f _c (2)/f _c (1) / T _rs and 1/T _rs , which is the folding frequency interval of the second Doppler analysis unit 210, is Define conditions for center frequencies f _c (1) and f _c (2) that satisfy the condition of being larger than an integer multiple α of the Doppler frequency resolution Δf _d . According to the determination condition shown in equation (13), the Doppler determination unit 213 can more easily determine the Doppler frequency difference due to the difference in the number of Doppler folding times n _al compared to the determination condition shown in equation (10). . For example, by using the determination condition shown in Equation (13), it is possible to improve the determination accuracy compared to the determination condition shown in Equation (10) even when there is a noise effect such as when the received signal level is low.

Here, for example, when f _c (2)>f _c (1), the determination condition for f _c (1) and f _c (2) shown in equation (13) is expressed by the following equation (14) .

Further, for example, when f _c (2)<f _c (1), the determination enable condition for f _c (1) and f _c (2) shown in equation (13) is expressed by the following equation (15).

As an example, when f _c (1) = 78 GHz, f _c (2) > f _c (1), f _c (2) is 78.61 for α = 1 and N c = 128, based on equation (14). GHz, and with α=2 and Nc=128, f _c (2) is set to be greater than 79.22 GHz.

In this way, by setting the center frequencies f _c (1) and f _c (2) that satisfy any of the determination conditions of formulas (10) to (15), the Doppler determination unit 213 determines the Doppler frequency range −1. /(2T _rs ) ≤ f _{d_TargetDoppler} < 1/(2T _rs ) Even when a target with a Doppler frequency exceeding 1/(2T rs ) is included (for example, when Doppler aliasing occurs), the Doppler frequency of the target can be determined.

For example, the Doppler determination unit 213 determines separation index information (f _{demul_Tx #1} (1), f _{demul_Tx#2} (1) , to f _{demul_Tx#Nt} (1)), and demultiplexing index information (f _{demul_Tx #1} (2), f _{demul_Tx #2} (2) to f _{demul_Tx#Nt} (2)) may be used to perform the following Doppler determination processing.

For example, the Doppler determination unit 213 determines separation index information (f _{demul_Tx #1} (1), f _{demul_Tx#2} (1) ˜f _{demul_Tx#Nt} (1)) is one, and separation index information (f _{demul_Tx #1} (2 ), f _{demul_Tx#2} (2) to f _{demul_Tx#Nt} (2)) is one, the following Doppler determination operation may be performed.

Further, the Doppler determination unit 213 has, for example, a plurality of demultiplexing index information of the Doppler multiplexed signal in the distance index f _{b_cfar} (1) output from the first Doppler demultiplexing unit 212, and the second Doppler demultiplexing unit 212 When there is a plurality of separation index information of the Doppler multiplexed signal in the output distance index f _{b_cfar} (2), the reception power indicated by those indices is compared, and the separation index information of the same reception power level is paired as each pair. can be related.

After that, the Doppler determination unit 213 determines the demultiplexing index information of the Doppler multiplexed signal output from the first Doppler demultiplexer 212 associated as a pair and the demultiplexing index of the Doppler multiplexed signal output from the second Doppler demultiplexer 212. The information may be used to perform the following Doppler determination operations. For example, the Doppler determination unit 213 associates separation index information of the Doppler multiplexed signal output from the first Doppler demultiplexer 212 and separation index information of the Doppler multiplexed signal output from the second Doppler demultiplexer 212. The following Doppler determination operation may be sequentially performed for each pair of , and may be repeated until the following operation is completed for all pairs.

An example of the Doppler determination operation in the Doppler determination unit 213 will be described below.

First, Doppler determination section 213 extracts separation index information (f _{demul_Tx #1} (1), f _{demul_Tx#2} (1) _{, . _ _} , the Doppler frequency estimate f _{d_VFT} (1) is calculated.

Here, separation index information (f _{demul_Tx #1} (1), f _{demul_Tx#2} (1) to f _{demul_Tx#Nt} (1)) includes a component of a predetermined Doppler shift amount given to each transmitting antenna 106 in the radar transmitting section 100 . For example, the Doppler determining unit 213 may calculate the Doppler frequency estimated value f _{d_VFT} (1) from which the Doppler shift amount component is removed.

Similarly, the Doppler determination unit 213 obtains demultiplexed index information (f _{demul_Tx #1} (2), f _{demul_Tx#2} (2 ) to f _{demul_Tx#Nt} (2)), the Doppler frequency when the target Doppler frequency is assumed to be within the Doppler frequency range -1/(2T _rs ) ≤ f _{d_TargetDoppler} < 1/(2T _rs ) Calculate the estimated value f _{d_VFT} (2).

Here, separation index information (f _{demul_Tx #1} (2), f _{demul_Tx#2} (2) to f _{demul_Tx#Nt} (2) includes a component of a predetermined Doppler shift amount given to each transmitting antenna 106 in the radar transmission unit 100. For example, the Doppler determination unit 213 obtains a Doppler frequency estimated value from which the Doppler shift amount component is removed. f _{d_VFT} (2) may be calculated.

Next, the Doppler determination unit 213 calculates the Doppler turn-around number n _al that minimizes the following equation (16).

Here, the Doppler turn-around number n _al is an integer value and is calculated within a range of integer values that cover the expected target Doppler frequency range.

Further _, f _est (f _{d_VFT (1)} , n _al ) is, for example, the Doppler frequency ( f _{d_VFT(1)} + n _al /T _rs ) and convert it to the observed Doppler frequency using a second chirp signal with center frequency f _c (2), f _c (2)/f _c ( Represents a function that outputs the value obtained by multiplying 1). For example, f _est (f _{d_VFT(1)} , n _al ) represents the Doppler frequency estimate corresponding to the second chirp signal estimated based on the Doppler frequency estimate f _{d_VFT} (1).

In equation (17), Fmod[x] is a function for calculating the _{Doppler frequency in consideration of the aliasing of the Doppler analysis unit 210 of ±1/2T rs .} Calculate =floor((x-1/(2T _rs ))/T _rs )+1 and output x - nmod/T _rs . Also, if x<-1/(2T _rs ), Fmod[x] computes nmod=ceil((|x|-1/(2T _rs ))/T _rs ) and x + nmod/T _rs to output Here, floor(x) is a floor function, a function that outputs the largest integer value that does not exceed x. Also, ceil(x) is a ceiling function, which is a function that outputs the smallest integer value exceeding x.

Hereinafter, the matching (or matching degree, closeness) between the Doppler frequency f _est (f _{d_VFT(1)} , n _al ) and the Doppler frequency estimated value f _{d_VFT} (2) when the Doppler folding number n _al is varied The number of Doppler aliasing times n _al (for example, n _al at which Equation (16) is minimized) when is the highest is denoted as "estimated Doppler number of aliasing times n _alest ".

Next, an example of the Doppler determination operation described above will be described with reference to FIG. In FIG. 9 , the horizontal axis represents the Doppler frequency of the target, and the vertical axis represents the Doppler frequency estimated value based on the outputs of the first Doppler demultiplexer 212 and the second Doppler demultiplexer 212 .

In FIG. 9, the solid line represents the Doppler frequency estimation value (for example, f _{d_VFT} (1)) when using the first chirp signal with the center frequency f _c (1), and the dotted line represents the center frequency f _c (2 ) represents the Doppler frequency estimate (f _{d_VFT} (2)) when the second chirp signal of ) is used. However, FIG. 9 shows an example where f _c (2)>f _c (1).

Also, in FIG. 9, circles represent Doppler frequency estimates based on the output of the first Doppler demultiplexer 212 for the Doppler frequency f _{d_VFT} (1)+n _al / _Trs . As shown in FIG. 9, the Doppler frequency estimation values (values on the vertical axis) indicated by circles are values (for example, f _{d_VFT} (1)) that do not depend on the number of Doppler folding times n _al .

Also, in FIG. 9, square marks represent Doppler frequency estimation values based on the output of the second Doppler demultiplexer 212 for the Doppler frequency f _{d_VFT} (1)+n _al / _Trs . As shown in FIG. 9, the Doppler frequency estimation values (values on the vertical axis) indicated by square marks are values dependent on the number of Doppler folding times n _al (for example, f _est (f _{d_VFT(1)} , n _al )) and Become. again. For example, the intervals in the vertical direction of the square marks in FIG. 9 are intervals larger than the Doppler frequency resolution Δf _d in the second Doppler analysis unit 210, and different Doppler frequency estimated values are detected according to the Doppler folding times n _al . It is possible.

For _example , the _Doppler determining unit 213 converts _the plot of square marks shown in FIG _. may be calculated using Then, for example, the Doppler determination unit 213 uses the calculated value (the value on the vertical axis of the square plot shown in FIG. 9) and the Doppler frequency estimation when using the second chirp signal with the center frequency f _c (2) The Doppler turn-around number n _al (for example, n _al at which equation (16) is minimized) that best matches the value f _{d_VFT} (2) (dotted line shown in FIG. 9) is set as the Doppler turn-around number estimated value n _alest . good.

In this way, the Doppler determination unit 213 determines the Doppler peak observed by the reflected wave signal corresponding to the first chirp signal with the center frequency f _c (1) (for example, the circle in FIG. 9, the first peak position), and , the reflection corresponding to the second chirp signal with center frequency f _c (2) based on the ratio f _c (2)/f _c (1) between the center frequency f _c (1) and the center frequency f _c (2) After estimating the Doppler peak of the wave signal (for example, the square mark in FIG. 9, the second peak position), the estimated Doppler peak and the Doppler peak observed by the reflected wave signal corresponding to the second chirp signal (for example, the 9 (dotted line, third peak position)), the number of turns n _alest may be determined based on the degree of matching (closeness). The degree of coincidence is the closeness in consideration of the change in the Dopp-peak value due to aliasing.

Note that the larger f _c (2)/f _c (1) in f _c (2)>f _c (1), or f _c (2)/f in f _c (2)<f _c (1) The smaller _c (1) is, the larger the difference in f _est (f _{d_VFT(1)} , n _al ) according to the number of folds n _al (for example, the difference from f _{d_VFT(1)} ). Then, it becomes easy to distinguish the Doppler frequency by the number of folding times n _al (for example, determine the number of folding times n _al ).

On the other hand, if the difference in Doppler frequency due to the number of aliasing n _al increases and exceeds ±1/(2T _rs ), the Doppler frequency becomes ambiguous, and the probability of an estimation error in the estimated value of the Doppler aliasing number n _alest increases. can increase.

Here, when the number of _Doppler aliasing is n _al , the Doppler frequency aliasing component n _al ×f _c (2)/f _c (1) / The condition that the difference between T _rs and n _al /T _rs that is the frequency interval of the number of folding times n _al of the second Doppler analysis unit 210 does not exceed ±1/(2T _rs ) is expressed by the following equation (18). be.

For example, when n _al is positive, Δn _al is in the range of ±1/(2T _rs ) up to the maximum n _al that satisfies the following equation (19), and the Doppler determination unit 213 can unambiguously estimate aliasing. Note that the maximum n _al that satisfies the following equation (19) is expressed as “n _almax ”. Also, for example, when n _al is negative, n _al =−n _almax satisfies the following equation (19). For these reasons, the Doppler frequency detection range is expanded, for example, n _almax times the Doppler frequency range for one transmitting antenna.

For example, if n _almax =2, if f _c (2)>f _c (1), then f _c (2) is set to a frequency lower than 1.25 times f _c (1). Well, f _c (1) may be set to a frequency lower than 1.25 times f _c (2) if f _c (2)<f _c (1). Also, for example, when n _almax =3, when f _c (2)>f _c (1), f _c (2) is (7/6) times f _c (1) It may be set to a low frequency, and if f _c (2) < f _c (1), then f _c (1) is set to a frequency lower than (7/6) times f _c (2). you can Note that the value of n _almax is not limited to 2 or 3, and may be another value.

For example, if f _c (1) and f _c (2) satisfy the condition of n _almax =2, the detection range of the Doppler frequency f _d is ±2/(T _rs ), and the Doppler frequency at one transmitting antenna is It is magnified by a factor of two over the frequency range.

Note that f _c (1) and f _c (2) may be set within the pass frequency range of the radar transmission unit 100 or the radar reception unit 200, and expansion of the detection range of the Doppler frequency is achieved by the radar transmission unit 100 or the radar Restrictions on the pass frequency characteristics of the receiving section 200 may also be applied.

For example, in the settings of f _c (1) and f _c (2), the maximum Doppler turn-around number n _almax is determined based on the assumed maximum Doppler frequency of the target, and the determination condition and expression (17) f _c (1) and f _c (2) that satisfy may be determined. Also, f _c (1) and f _c (2) may be determined so that f _c (1) and f _c (2) are within the pass frequency range of the radar transmitter 100 or the radar receiver 200 .

The operation example of the Doppler determination unit 213 has been described above.

In FIG. 2, the direction estimation unit 214 receives information input from the q-th Doppler demultiplexing unit 212 (for example, the distance index f _{b_cfar} (q) and the demultiplexing index information (f _{demul_Tx#1} (q), f _{demul_Tx#2} (q) to f _{demul_Tx#Nt} (q))), perform target direction estimation processing.

For example, the direction estimation unit 214 obtains the distance index f _{b_cfar} (q) and the separation index information (f _{demul_Tx#1} (q), f _{demul_Tx#2} (q) to f _{demul_Tx#Nt} (q)), the output of the q-th Doppler analysis unit 210 is extracted, and the q-th virtual reception array correlation vector h _q (f _{b_cfar} ( q), f _{demul_Tx#1} (q), f _{demul_Tx#2} (q) to f _{demul_Tx#Nt} (q)) and perform direction estimation processing. where q=1,2.

The q-th virtual receive array correlation vector h _q (f _{b_cfar} (q), f _{demul_Tx#1} (q), f _{demul_Tx#2} (q) to f _{demul_Tx#Nt} (q)) is expressed by equation (20) as , contains Nt×Na elements that are the product of the number of transmit antennas Nt and the number of receive antennas Na. The virtual receive array correlation vector h _q (f _{b_cfar} (q), f _{demul_Tx#1} (q), f _{demul_Tx#2} (q) to f _{demul_Tx#Nt} (q)) is It is used for direction estimation processing based on the phase difference between the receiving antennas 202 . where integer z=1 to Na. Since direction estimation section 214 performs direction estimation processing using the outputs of first and second Doppler demultiplexing sections 212 with the same distance index, f _{b_cfar} (1) = f _{b_cfar} (2) = f _{b_cfar} .

In Equation (20), h _cal[b] is an array correction value that corrects the phase deviation and amplitude deviation between transmitting array antennas and between receiving array antennas. Integer b=1 to (Nt×Na).

The direction estimation unit 214, for example, calculates the direction estimation evaluation function value P _H (θ _u , f _{b_cfar} , f _{demul_Tx#1} (1) to f _{demul_Tx#Nt} (1), f _{demul_Tx#1} (2) to f _{demul_Tx#Nt} The spatial profile is calculated by changing the azimuth direction θ _u in (2)) within a predetermined angle range. The direction estimation unit 214 extracts a predetermined number of maximal peaks of the calculated spatial profile in descending order, and outputs the azimuth directions of the maximal peaks as direction-of-arrival estimation values (for example, positioning output).

Note that the direction estimation evaluation function value P _H (θ _u , f _{b_cfar} , f _{demul_Tx#1} (1) to f _{demul_Tx#Nt} (1), f _{demul_Tx#1} (2) to f _{demul_Tx#Nt} (2)) is There are various methods depending on the direction-of-arrival estimation algorithm. For example, an estimation method using an array antenna disclosed in Non-Patent Document 3 may be used.

For example, when Nt×Na virtual reception arrays are linearly arranged at regular intervals of d _H , the beamformer method can be expressed by the following equation (21). In addition to the beamformer method, methods such as Capon and MUSIC are also applicable. Note that in equation (21), the superscript H is the Hermitian transposition operator.

Also, in equation (21), a _q (θ _u ) indicates the direction vector of the virtual receiving array for the incoming wave in the azimuth direction θ _u and is expressed by equation (22). In equation (22), λ _q is the wavelength of the radar transmit signal (eg, the qth chirp signal) for center frequency f _c (q), and λ _q =C ₀ /f _c (q).

Also, the azimuth direction θ _u is a vector obtained by changing the azimuth range in which direction-of-arrival estimation is performed at a predetermined azimuth interval β ₁ . For example, θ _u is set as follows.
_θu = θmin + uβ ₁ , integer u = 0 to NU
NU=floor[(θmax−θmin)/ _β1 ]+1
where floor(x) is a function that returns the largest integer value that does not exceed the real number x.

For example, instead of the direction vector a _q (θ _u ) shown in Equation (22), the direction estimator 214 uses the center frequencies f _c (1) and f _c (2) as shown in Equation (23). The direction vector a(θ _u ) of the virtual receiving array for the incoming wave in the azimuth direction θ at the average center frequency may be used in common. where λ _a is the wavelength of the radar transmission signal for the center frequency (f _c (1)+f _c (2))/2, and λ _a =2C ₀ /(f _c (1)+f _c ( 2)). In this case, the direction estimator 214 can commonly use the direction vector a(θ _u ) of the virtual reception array for the processing of each chirp signal, thereby reducing the memory capacity for storing the direction vectors of the virtual reception array. You can also get the effect you can.

In the above example, the direction estimator 214 calculates the azimuth direction as the direction-of-arrival estimation value. However, the present invention is not limited to this. Direction-of-arrival estimation in azimuth and elevation directions is also possible by using MIMO antennas. For example, the direction estimator 214 may calculate the azimuth direction and the elevation angle direction as the direction-of-arrival estimation values and use them as the positioning output.

Through the above operation, direction estimation section 214 outputs distance index f _{b_cfar} (q), separation index information of Doppler multiplexed signals (f _{demul_Tx#1} (q), f _{demul_Tx#2} (q), . , f _{demul_Tx#Nt} (q)) may be output. Further, the direction estimation unit 214 further includes, as positioning outputs, a distance index f _{b_cfar} (q), separation index information of Doppler multiplexed signals (f _{demul_Tx#1} (q), f _{demul_Tx#2} (q), . . . , f _{demul_Tx#Nt} (q)) may be output. The direction estimator 214 may output the positioning output (or the positioning result) to, for example, a vehicle control device for an in-vehicle radar or an infrastructure control device for an infrastructure radar (not shown).

Further, the direction estimation unit 214, for example, the Doppler frequency information f _{d_VFT(1)} +n _alest /T _rs determined by the Doppler determination unit 213 and f _c (2)/f _c (1) (f _{d_VFT(1 )} +n _alest /T _rs ) or both of them may be output.

Also, the distance index f _{b_cfar} may be converted into distance information using Equation (1) and output.

Further, the Doppler frequency information determined by the Doppler determination unit 213 may be converted to relative velocity information and output. To convert the Doppler frequency information f _{d_VFT(1)} +n _alest /T _rs by the center frequency f _c (1) determined by the Doppler determination unit 213 to the relative velocity v _d , the following equation (24) is used. can be converted.

Similarly, the Doppler frequency information f _c (2)/f _c (1) (f _{d_VFT(1)} +n _alest /T _rs ) by the center frequency f _c (2) determined by the Doppler determination unit 213 is used as the relative velocity When converted to v _d , the value is the same as in Equation (24) as shown in Equation (25) below, so the relative velocity component information is output as a common value (or unified value) for different center frequencies. may be

As described above, in the present embodiment, the radar apparatus 10, for each transmission cycle in which the transmission signal is transmitted from the transmission antenna 106, for example, the first center Alternating between the frequency and the second center frequency. Thereby, the radar device 10 can determine the number of times of folding back based on the deviation of the Doppler frequency in the Doppler analysis according to the difference in the center frequency. Therefore, the radar device 10 can expand the Doppler frequency range (or the maximum value of the relative velocity) in which the Doppler multiplexed signal can be separated, for example, according to the number of times of folding that can be determined.

As described above, according to this embodiment, it is possible to expand the Doppler frequency range (or the maximum value of the relative velocity) in which ambiguity does not occur. Thereby, the radar device 10 can accurately detect a target (for example, the direction of arrival) in a wider Doppler frequency range.

In addition, in the present embodiment, the Doppler frequency range in which the Doppler multiplexed signal can be separated is expanded by setting the center frequency of the chirp signal. may be omitted. Therefore, according to the present embodiment, complication of the hardware configuration in the radar device 10 can be suppressed, and an increase in power consumption or heat generation in the radar device 10 can be suppressed. Further, in this embodiment, the Doppler frequency range in which the Doppler multiplexed signal can be separated is expanded by setting the center frequency of the chirp signal, so the application of the method of shortening the transmission period _Tr may be omitted. Therefore, according to the present embodiment, it is possible to suppress the reduction of the range of distance detectable by the radar device 10 or the deterioration of the distance resolution.

In this embodiment, the modulation parameters for the first chirp signal and the second chirp signal have a common parameter other than the center frequency, but the present invention is not limited to this. An embodiment of the present disclosure may be applied to, for example, chirp signals having the same range resolution and the same frequency sweep bandwidth B _w (q).

For example, as shown in FIG. 10, it is set by modulation parameters such that B _w (1)=B _w (2), T _sw (1)≠T _sw (2), and D _m (1)≠D _m (2). A first chirp signal and a second chirp signal may be used. In this case, although the frequency sweep times T _SW of the first chirp signal and the second chirp signal are different, the frequency sweep bandwidth B _w is the same, and the range resolution ΔR (=C ₀ /2B _w ) is the same. The device 10 can obtain the same effect by performing the operation according to the embodiment of the present disclosure described above.

Further, for example, as shown in FIG. 10, by setting T _sw (1)≠T _sw (2), the beat signal output from each reception radio section 203 is converted to the A/D conversion section of each signal processing section 206 . When performing discrete sampling at 207, the number of discrete sampling data obtained in a predetermined time range (range gate) T _sw (1)≠T _sw (2) is different. Therefore, the beat frequency analysis unit 208 performs the following operation instead of performing FFT processing on N _data pieces of discrete sampling data obtained in a predetermined time range (range gate) T _sw in each transmission cycle _Tr , for example. good too.

For example, the beat frequency analysis unit 208 performs FFT processing on N _data (1) pieces of discrete sampling data obtained in a predetermined time range (range gate) T _sw (1) in the period in which the first chirp signal is transmitted, Also, in the cycle in which the second chirp signal is transmitted, FFT processing may be performed on N _data (2) pieces of discrete sampling data obtained in a predetermined time range (range gate) T _sw (2). Then, the beat frequency analysis unit 208 may perform subsequent processing, for example, with the smaller one of N _data (1) and N _data (2) being N _data .

(Embodiment 2)
The radar device according to this embodiment may be similar to the radar device 10 shown in FIG.

In Embodiment 1, the conditions for determining the number of Doppler folding times regarding the center frequency f _c (1) of the first chirp signal and the center frequency f _c (2) of the second chirp signal have been described. For example, in Embodiment 1, the Doppler determination unit 213 determines the number of Doppler loopbacks when the determination condition is satisfied. explained that it is

Here, for example, in MIMO radar using unequal interval Doppler multiplexing, if there are multiple reflected waves from similar distances, and the Doppler intervals of those reflected waves are the Doppler multiplexing interval (or the Doppler multiplexing interval multiple), the radar device 10 is likely to detect erroneous detection of Doppler frequency regions with unequal intervals. There is

In this embodiment, in addition to the effects of the first embodiment, a radar device capable of improving detection performance even in such a situation will be described. For example, in the present embodiment, conditions for determining a plurality of reflected waves regarding the center frequency f _c (1) of the first chirp signal and the center frequency f _c (2) of the second chirp signal will be described. For example, setting conditions (determinable conditions) for the center frequency f _c (1) of the first chirp signal and the center frequency f _c (2) of the second chirp signal set in the signal generation control unit 104 of the radar transmission unit 100, Also, the operation of the Doppler determination unit 213 is different from that in the first embodiment. In the following, the operation of the present embodiment, which is different from that of the first embodiment, will be mainly described.

[Determinable conditions]
First, regarding the setting condition (determinable condition) of the center frequency f _c (1) of the first chirp signal and the center frequency f _c (2) of the second chirp signal set in the signal generation control unit 104 of the radar transmission unit 100 explain.

The Doppler shifter 105 of the radar transmitter 100 may use, for example, the phase rotation φ _n (m) shown in Equation (4). In this case, the Doppler multiplexing interval Δf _DDM is expressed by the following equation (26).

Some of the Doppler multiplexing intervals Δf _DDM shown in Equation (26) are not used for Doppler multiplexing and are not assigned transmission signals. Here, δ is an integer of 1 or more. When δ is 1, the Doppler multiplexing interval Δf _DDM is the widest, and as δ increases, the Doppler multiplexing interval Δf _DDM becomes narrower. For example, the narrower the Doppler multiplexing interval, the greater the mutual interference between Doppler multiplexed signals.

For example, Doppler frequencies f _{d1_T#1} and f _{d1_T} #2 of reflected waves from two targets (hereinafter referred to as “Target#1” and “Target#2”) detected at the same distance index are Doppler When arriving at a multiplexing interval Δf _DDM (or a multiple of the Doppler multiplexing interval N _mul ×Δf _DDM ), the Doppler frequencies f _{d1_T#1} and f _{d1_T#2} are expressed by the following equations (27) and (28). , Doppler frequencies f _{d1_T#1} and f _{d1_T#2} have the relationship of Equation (29). Here, the relational expression when using the first chirp signal with the center frequency f _c (1) is shown.
f _{d1_T#1} = f _{d_T#1_VFT} (1)+n _{al_T#1} /T _rs (27)
f _{d1_T#2} = f _{d1_T#2_VFT} (1) + n _{al_T#2} /T _rs (28)
|f _{d1_T#1} - f _{d1_T#2} |= N _mul ×Δf _DDM (29)

Here, f _{d_T#1_VFT} (1) is the Doppler frequency estimate value of Target #1 detected by the first Doppler analysis unit 210 and the first Doppler demultiplexing unit 212, and f _{d1_T#2_VFT} (1) is It is a Doppler frequency estimate value of Target #2 detected by the first Doppler analysis unit 210 and the first Doppler demultiplexing unit 212. FIG. Also, n _{al_T#1} represents the number of Doppler turn-around times for Target#1, and n _{al_T#2} represents the number of Doppler turn-around times for Target#2. Also, n _{al_T#1} and n _{al_T#2} take integer values.

Also, N _mul is a natural number within the assumed Doppler frequency range. _For example _, N _mul may be set to N _{mul ε} {1, . 1, . . . , (Nt+δ)×n _almax }.

For the relational expression of the two targets (Target#1, Target#2) expressed as above, the radar device 10 observes the Doppler frequency using the second chirp signal with the center frequency f _c (2). The following relational expressions (30), (31), and (32) are obtained for the case where Note that the relational expressions (30), (31), and (32) indicate that the Doppler frequencies f _{d2_T#1} and f _{d2_T#2} when using the second chirp signal with the center frequency f _c (2) are equal to the Doppler It utilizes the fact that it can be calculated by multiplying the frequencies f _{d1_T#1} and f _{d1_T#2} by the center frequency ratio f _c (2)/f _c (1).
_{fd2_T#s1} = _fc (2)/ _fc (1)×( _{fd_T#1_VFT} (1)+ n _{al_T#1} / _Trs ) (30)
f _{d2_T#2} = f _c (2)/f _c (1) × (f _{d1_T#2_VFT} (1) + n _{al_T#2} /T _rs ) (31)
|f _{d2_T#1} - f _{d2_T#2} |= f _c (2)/f _c (1)×(N _mul ×Δf _DDM ) (32)

Here, the difference between f _c (2)/f _c (1) × (N _mul × Δf _DDM ) and the Doppler multiplexing interval N _mul × Δf _DDM (for example, the value of expression (32) and expression (29 ) is greater than the Doppler frequency resolution Δf _d in the second Doppler analysis unit 210, the center frequency ratio f _c (2)/f _c (1) may be set.

For example, the radar apparatus 10 sets the center frequency f _c (1) of the first chirp signal and the center frequency f _c of the second chirp signal so as to satisfy the “second determinable condition (1)” of the following equation (33). (2) may be determined.

As a result, for example, using the outputs of the second Doppler analysis unit 210 and the second Doppler demultiplexing unit 212 using the second chirp signal with the center frequency f _c (2), Target#1 and Target#2 can each be The Doppler frequency is the Doppler frequency estimate value (for example _{, Doppler multiplexing interval Δf DDM (} or It is observed as a Doppler frequency shifted from at least the Doppler frequency resolution Δf _d in the second Doppler analysis unit 210 from the interval of the multiple).

Therefore, the radar apparatus 10 can suppress duplication of Doppler multiplexed signal components between two reflected waves observed at the same distance, for example, and improve separation performance of the Doppler multiplexed signals of the two reflected waves. For example, the second determinable condition (1) is that the estimated Doppler frequencies of Target #1 and Target #2 detected by the first Doppler analysis unit 210 and the first Doppler demultiplexing unit 212 are equal to the Doppler multiplexing interval Δf _DDM ( Alternatively, even if the interval is a multiple of Δf _DDM ) and Doppler demultiplexing is difficult for Target #1 and Target #2, the second Doppler analysis unit 210 and the second Doppler demultiplexing unit 212 using the second chirp signal Target#1 and Target#2 can be Doppler demultiplexed based on the output, and Doppler frequency estimates of Target#1 and Target#2 can be obtained.

Here, when f _c (2)>f _c (1), the conditions f _c (1) and f _c (2) in the second determinable condition (1) are represented by the following equation (34).

For example, if N _mul =1 is satisfied, then N _mul >1 also holds, so the second determinable condition (1) may be expressed as in the following equation (35).

Similarly, when _fc (2)< _fc (1), the conditions _fc (1) and _fc (2) in the second determinable condition (1) are expressed by the following equation (36).

For example, if N _mul =1 is satisfied, then N _mul >1 also holds, so the second determinable condition (1) may be expressed as in the following equation (37).

Similarly, the Doppler frequencies f _{d2_T#1} and f _{d2_T#2} of the reflected waves from two targets (for example, Target#1 and Target#2) detected at the same distance index are the Doppler multiplexing intervals Δf _DDM ( Alternatively, when arriving at an interval that is a multiple of the Doppler multiplexing interval N _mul ×Δf _DDM ), the Doppler frequencies f _{d2_T#1} and f _{d2_T#2} are expressed by the following equations (38) and (39), and the Doppler frequency f _{d2_T#1} and f _{d2_T#2} have the relationship of Equation (40). Here, the relational expression when using the second chirp signal with the center frequency f _c (2) is shown.
f _{d2_T#1} = f _{d_T#1_VFT} (2) + n _{al_T#1} /T _rs (38)
f _{d2_T#2} = f _{d1_T#2_VFT} (2) + n _{al_T#2} /T _rs (39)
|f _{d2_T#1} - f _{d2_T#2} | = N _mul ×Δf _DDM (40)

Here, f _{d_T#1_VFT} (2) is the Doppler frequency estimate value of Target #1 detected by the second Doppler analysis unit 210 and the second Doppler demultiplexing unit 212, and f _{d1_T#2_VFT} (2) is It is the Doppler frequency estimate value of Target #2 detected by the second Doppler analysis unit 210 and the second Doppler demultiplexing unit 212. FIG. Also, n _{al_T#1} represents the number of Doppler turn-around times for Target#1, and n _{al_T#2} represents the number of Doppler turn-around times for Target#2. Also, n _{al_T#1} and n _{al_T#2} take integer values.

For the relational expression of the two targets (Target#1, Target#2) expressed as above, the radar device 10 observes the Doppler frequency using the first chirp signal with the center frequency f _c (1). The following relational expressions (41), (42), and (43) are obtained for the case where Note that the relational expressions (41), (42), and (43) indicate that the Doppler frequencies f _{d1_T#1} and f _{d1_T#2} when using the first chirp signal with the center frequency f _c (1) are equal to the Doppler It utilizes the fact that it can be calculated by multiplying the frequencies f _{d2_T#1} and f _{d2_T#2} by the center frequency ratio f _c (1)/f _c (2).
f _{d1_T#1} = fc(1)/fc(2)×(f _{d_T#1_VFT} (2)+ n _{al_T#1} /T _rs ) (41)
f _{d1_T#2} = fc(1)/fc(2)×( f _{d1_T#2_VFT} (2)+ n _{al_T#2} /T _rs ) (42)
|f _{d1_T#1} - f _{d1_T#2} |= fc(1)/fc(2)×(N _mul ×Δf _DDM ) (43)

Here, the difference between f _c (1)/f _c (2) × (N _mul × Δf _DDM ) and the Doppler multiplexing interval N _mul × Δf _DDM (for example, the value of expression (43) and expression (40 ) is greater than the Doppler frequency resolution Δf _d in the first Doppler analysis unit 210, the center frequency ratio f _c (1)/f _c (2) may be set.

For example, the radar apparatus 10 sets the center frequency f _c (1) of the first chirp signal and the center frequency f _c of the second chirp signal so as to satisfy the “second determinable condition (2)” of the following equation (44). (2) may be determined.

As a result, for example, using the outputs of the first Doppler analysis unit 210 and the first Doppler demultiplexing unit 212 using the first chirp signal with the center frequency f _c (1), Target#1 and Target#2 can each be The _{Doppler frequency is the Doppler frequency estimate value (for example, Doppler multiplexing interval Δf DDM (} or interval of multiples), it is observed as a Doppler frequency that deviates from at least the Doppler frequency resolution Δf _d in the first Doppler analysis unit 210 .

Therefore, the radar apparatus 10 can suppress duplication of Doppler multiplexed signal components between two reflected waves observed at the same distance, for example, and improve separation performance of the Doppler multiplexed signals of the two reflected waves. For example, the second determinable condition (2) is that the estimated Doppler frequencies of Target #1 and Target #2 detected by the second Doppler analysis unit 210 and the second Doppler demultiplexing unit 212 are equal to the Doppler multiplexing interval Δf _DDM ( or an interval that is a multiple of Δf _DDM ), and even if Doppler demultiplexing is difficult for Target #1 and Target #2, the first Doppler analysis unit 210 and the first Doppler demultiplexing unit 212 using the first chirp signal Target#1 and Target#2 can be Doppler demultiplexed based on the output, and Doppler frequency estimates of Target#1 and Target#2 can be obtained.

Here, when f _c (2)>f _c (1), the conditions of f _c (1) and f _c (2) in the second determinable condition (2) are represented by the following equation (45).

For example, when N _mul =1 is satisfied (meaning that N _mul >1 is also satisfied), the second determinable condition (2) may be expressed as the following equation (46).

Moreover, when the second determination condition (2) is satisfied as in the following equation (47), the second determination condition (1) is also satisfied.

Therefore, for example, the following equation (48) is called a "second determinable condition" when f _c (2)>f _c (1).

Similarly, when f _c (2)<f _c (1), the conditions f _c (1) and f _c (2) in the second determinable condition (2) are expressed by the following equation (49).

For example, when N _mul =1 is satisfied (meaning that N _mul >1 is also satisfied), the second determinable condition (2) may be expressed as in the following equation (50).

Further, for example, from equations (37) and (50), when the second determinable condition (2) is satisfied as in the following equation (51), the second determinable condition (1) is also satisfied.

Therefore, for example, the following equation (52) is called a "second determinable condition" in the case of f _c (2)<f _c (1).

Also, for example, in the second determinable condition shown in Equation (33) or Equation (44), center frequencies f _c (1) and f that satisfy a condition larger than an integer multiple (for example, α times) of the Doppler frequency resolution Δf _d . _c (2) may be used (where α≧1). In this case, the radar apparatus 10 can more easily perform Doppler separation even when there is a noise effect, such as when the received signal level is low, as α increases. Further, for example, the second determinable condition shown in formula (48) when f _c (2) > f _c (1), and the formula (52) when f _c (2) < f _c (1) may be represented by the following equations (53) and (54).

As an example, when f _c (1) = 78 GHz, f _c (2) > f _c (1), α = 1, N c = 128, Nt = 3, δ = 1, f _c (2) is 80.51 It is set to be greater than GHz and is set to f _c (2)=83.2 GHz when α=2 and Nc=128. Also, for example, when α=1, Nc=256, Nt=3, δ=1, f _c (2) is set to 79.23 GHz, and when α=2, Nc=256, f _c (2) is larger than 80.51 GHz. set.

Note that the second determinable condition is a condition in which the difference |f _c (2)−f _c (1) | between the center frequencies of the chirp signals is wider than the first determinable condition. For example, when the second determinable condition is satisfied, the first determinable condition is also satisfied.

In addition, f _c (1) and f _c (2) may be set within the pass frequency range of the radar transmission unit 100 or the radar reception unit 200, and expansion of the detection range of the Doppler frequency is achieved by the radar transmission unit 100 or the radar Restrictions on the pass frequency characteristics of the receiving section 200 may also be applied.

Also, the second determinable condition may also be set in consideration of the restrictions of the frequency condition shown in Equation (18) or (19). Thereby, the effect of Embodiment 1 can be similarly obtained.

In addition, a frequency condition may be added to the second determination enable condition such that the difference between the Doppler frequencies observed between f _c (1) and f _c (2) is less than the Doppler multiplexing interval Δf _DDM . For example, f _c (1) and f _c (2) may be set so as to satisfy the conditions shown in the following equations (55) and (56).

Here, N _mul is a natural number within the assumed Doppler frequency range. _For example _, N _mul may be set to N _{mul ε} {1, . 1, . . . , (Nt+δ)×n _almax }.

The determination possible conditions have been described above.

[Doppler determination method]
Next, the Doppler determination unit 213 may perform the following operations using the center frequencies f _c (1) and f _c (2) that satisfy the above-described second determination condition.

The Doppler determination unit 213 separates the separation index information of the Doppler multiplexed signal output from the first Doppler demultiplexer 212 and the Doppler multiplexed signal output from the second Doppler demultiplexer 212 at the distance index f _{b_cfar} , for example. When the same number of index information is included, the same operation as in the first embodiment may be performed. As a result, the same effect as in the first embodiment can be obtained.

On the other hand, the Doppler determination unit 213 uses the separation index information of the Doppler multiplexed signal output from the first Doppler _{demultiplexer} 212 and the Doppler If the same number of separation index information of multiplexed signals is not included, the following processing may be performed. For example, the Doppler determination unit 213, for example, when there are a plurality of reflected waves from similar distances to the radar device 10, one of the Doppler analysis for the first chirp signal and the Doppler analysis for the second chirp signal If multiple reflected waves are separated and there is a possibility that multiple reflected waves are not separated, the following process may be performed.

<Case 1>
In case 1, for example, the distance index f _{b_cfar} includes a plurality of demultiplexing index information of the Doppler multiplexed signal output from the first Doppler demultiplexing unit 212, and the Doppler multiplexing output from the second Doppler demultiplexing unit 212 is included. A case where no signal separation index information is included will be described. For example, in case 1, the Doppler multiplexed signal is demultiplexed by the first Doppler demultiplexer 212 and the Doppler multiplexed signal is not demultiplexed by the second Doppler demultiplexer 212. For example, the following cases are the cases.

When there are two reflected waves from the same distance from the radar device 10, the separation index information of the Doppler multiplexed signal output from the first Doppler demultiplexer 212 and the output from the second Doppler demultiplexer 212 It is expected that the separation index information of the Doppler multiplexed signals for the two reflected waves will be output as the separation index information of the Doppler multiplexed signals.

However, by transmitting using the second chirp signal, the reflected wave #1 and the reflected wave #2 are Doppler multiplexing interval Δf _DDM or a multiple of the Doppler multiplexing interval, as shown in (c) of FIG. 1, for example. , a portion of the Doppler multiplexed signal may be received as overlapping Doppler frequency components between reflected wave #1 and reflected wave #2. Therefore, it becomes difficult to demultiplex the Doppler multiplexed signal, and the demultiplexing index information of the Doppler multiplexed signal output from the second Doppler demultiplexer 212 may not be included.

On the other hand, even if such a reflected wave exists, the radar device 10 satisfies the second determination condition by transmitting using the first chirp signal, so the reflected wave #1 and the reflected wave #2 are the same. Doppler-multiplexed signals in some parts are no longer received as duplicated Doppler frequency components. Therefore, the demultiplexing index information of the Doppler multiplexed signal output from the first Doppler demultiplexing unit 212 is included. In such a case, the following operations are performed.

In the following, as an example, as the demultiplexing index information of the Doppler multiplexed signal output from the first Doppler demultiplexer 212, the Doppler multiplexed signals of the reflected waves from two targets (for example, Target#1 and Target#2) A case where separation index information is included will be described.

For example, when using a chirp signal with a center frequency f _c (2), the Doppler determination unit 213 determines Doppler frequencies f _{d2_T#1} and f _{d2_T#} of reflected waves from two targets (Target#1 and Target#2). ₂ arrived at a Doppler frequency interval equal to the Doppler multiplexing interval Δf _DDM (or a multiple of the Doppler multiplexing interval N _mul ×Δf _DDM ). In this case, the Doppler determination unit 213 may perform the following Doppler determination process when arriving waves overlap.

For example, the Doppler determination unit 213 may calculate the Doppler turn-around number n _{al_#T1} for Target #1 and the Doppler turn-around number n _{al_#T2} for Target #2 that minimize the following equation (57).

Here, the Doppler turn-around times n _{al_#T1} and n _{al_#T2} are integer values and may be calculated within a range of integer values covering the expected target Doppler frequency range. For example, n _{al_#T1} and n _{al_#T2} may be calculated within the range of ±n _almax using the maximum number of times of folding n _almax that satisfies Equation (19). In addition, when the Doppler turn-around times n _{al_#T1} and n _{al_#T2} are varied, the respective Doppler turn-around times that minimize Equation (57) are denoted as n _{alest_#T1} and n _{alest_#T2} . Also, mod[x,y] is a function representing the remainder when x is divided by y.

For example, when using a chirp signal with a center frequency f _c (2), the Doppler frequencies f _{d2_T#1} and f _{d2_T#2} of reflected waves from two targets (Target#1 and Target#2) are the Doppler multiplexing interval Equation (57) is minimized when the condition of arrival at a Doppler frequency interval of Δf _DDM (or a multiple of the Doppler multiplexing interval N _mul ×Δf _DDM ) is met. The Doppler determination unit 213 uses this fact to estimate the Doppler turn-around times n _{alest_#T1} and n _{alest_#T2} of Target#1 and Target#2.

Note that in equation (57), for example, Doppler frequencies f _{d2_T#1} and f d2_T _#2 in the case of Doppler turn-around times n _{al_#T1} and n _{al_#T2} are f _est (f _{d_T#1_VFT(1)} , n _{al_T#1} ) and f _est (f _{d_T#2_VFT(1)} , n _{al_T#2} ). Here, f _est (f _{d_VFT(1)} , n _al ) may be the function shown in Equation (17). Further, each of the Doppler frequency estimation values f _{d_T#1_VFT(1)} and f _{d_T#2_VFT(1)} is, for example, demultiplexing index information of the Doppler multiplexed signal at the distance index f _{b_cfar} output from the first Doppler demultiplexing unit 212. is the Doppler frequency estimate assuming that the Doppler frequency of the target is in the Doppler frequency range −1/(2T _rs )≦ _{fd_TargetDoppler} <1/(2T _rs ) based on .

<Case 2>
In case 2, for example, the distance index f _{b_cfar} includes a plurality of demultiplexing index information of the Doppler multiplexed signal output from the second Doppler demultiplexer 212, and the Doppler multiplexed signal output from the first Doppler demultiplexer 212 A case where no signal separation index information is included will be described. For example, in case 2, the Doppler multiplexed signal is not demultiplexed in the first Doppler demultiplexer 212 and the Doppler multiplexed signal is demultiplexed in the second Doppler demultiplexer 212. For example, the following case is .

When there are two reflected waves from the same distance from the radar device 10, the separation index information of the Doppler multiplexed signal output from the first Doppler demultiplexer 212 and the output from the second Doppler demultiplexer 212 It is expected that the separation index information of the Doppler multiplexed signals for the two reflected waves will be output as the separation index information of the Doppler multiplexed signals.

However, by transmitting using the first chirp signal, the reflected wave #1 and the reflected wave #2 are Doppler multiplexing interval Δf _DDM or a multiple of the Doppler multiplexing interval, as shown in (c) of FIG. 1, for example. , a portion of the Doppler multiplexed signal may be received as overlapping Doppler frequency components between reflected wave #1 and reflected wave #2.

Therefore, it becomes difficult to demultiplex the Doppler multiplexed signal, and the demultiplexed index information of the Doppler multiplexed signal output from the first Doppler demultiplexer 212 may not be included.

On the other hand, even if such a reflected wave exists, the radar device 10 satisfies the second determination condition by transmitting using the second chirp signal, so the reflected wave #1 and the reflected wave #2 are the same. Doppler-multiplexed signals in some parts are no longer received as duplicated Doppler frequency components. Therefore, the demultiplexing index information of the Doppler multiplexed signal output from the second Doppler demultiplexing unit 212 is included. In such a case, the following operations are performed.

In the following, as an example, as the demultiplexing index information of the Doppler multiplexed signal output from the second Doppler demultiplexer 212, the Doppler multiplexed signals of the reflected waves from two targets (for example, Target#1 and Target#2) A case where separation index information is included will be described.

For example, when using a chirp signal with a center frequency f _c (1), the Doppler determination unit 213 determines Doppler frequencies f _{d1_T#1} and f _{d1_T#} of reflected waves from two targets (Target#1 and Target#2). ₂ arrived at a Doppler frequency interval equal to the Doppler multiplexing interval Δf _DDM (or a multiple of the Doppler multiplexing interval N _mul ×Δf _DDM ). In this case, the Doppler determination unit 213 may perform the following Doppler determination process when arriving waves overlap.

For example, the Doppler determining unit 213 may calculate the Doppler turn-around times n _{al_#T1} and n _{al_#T2} of Target#1 and Target#2 that minimize the following equation (58).

Here, the Doppler turn-around times n _{al_#T1} and n _{al_#T2} are integer values and may be calculated within a range of integer values covering the expected target Doppler frequency range. For example, n _{al_#T1} and n _{al_#T2} may be calculated within the range of ±n _almax using the maximum number of times of folding n _almax that satisfies Equation (19). In addition, when the Doppler turn-around times n _{al_#T1} and n _{al_#T2} are varied, the respective Doppler turn-around times that minimize Equation (58) are denoted as n _{alest_#T1} and n _{alest_#T2} .

For example, when using a chirp signal with a center frequency f _c (1), the Doppler frequencies f _{d1_T#1} and f _{d1_T#2} of reflected waves from two targets (Target#1 and Target#2) are the Doppler multiplexing interval Equation (58) is minimized when the condition of arrival at a Doppler frequency interval of Δf _DDM (or a multiple of the Doppler multiplexing interval N _mul ×Δf _DDM ) is satisfied. The Doppler determination unit 213 uses this fact to estimate the Doppler turn-around times n _{alest_#T1} and n _{alest_#T2} of Target#1 and Target#2.

Note that in equation (58), for example, Doppler frequencies f _{d1_T#1} and f d1_T _#2 in the case of Doppler turn-around times n _{al_#T1} and n _{al_#T2} , f _est2 (f _{d_T#1_VFT(2)} , n _{al_T#1} ) and f _est2 (f _{d_T#2_VFT(2)} , n _{al_T#2} ). Further, each of the Doppler frequency estimates f _{d_T#1_VFT(2)} and f _{d_T#2_VFT(2)} is based on the demultiplexing index information of the Doppler multiplexed signal in the distance index f _{b_cfar} output from the second Doppler demultiplexing unit 212. is the Doppler frequency estimate when the Doppler frequency of the target is assumed to be in the Doppler frequency range -1/(2T _rs ) ≤ _{fd_TargetDoppler} < 1/(2T _rs ).

Also, f _est2 (f _{d_VFT(2)} , n _al ) is a function shown in the following equation (59) and is calculated based on the demultiplexing index information of the Doppler multiplexed signal output from the second Doppler demultiplexer 212. Calculate the Doppler frequency (f _{d_T#1_VFT(2)} + n _al /T _rs ) when the estimated Doppler frequency f _{d_VFT(2)} is the Doppler folding number n _al , and the center frequency f _c (1) Represents a function that outputs a value multiplied by f _c (1)/f _c (2) to convert to the Doppler frequency observed using the first chirp signal.

By the operation of the Doppler determining unit 213 as described above, the separation index information of the Doppler multiplexed signal output from the first Doppler _{demultiplexing} unit 212 and the Doppler demultiplexing unit 212 output from the second Doppler demultiplexing unit 212 can Even if the same number of multiplexed signal demultiplexing index information is not included, the Doppler determination unit 213, as in Case 1 or Case 2, performs Doppler demultiplexing based on the Doppler multiplexed signal demultiplexing index information obtained in one Doppler demultiplexing unit 212. , the Doppler frequency of the reflected wave when using the chirp signal with the other center frequency is assumed to arrive at a Doppler frequency interval equal to the Doppler multiplexing interval Δf _DDM (or a multiple of the Doppler multiplexing interval N _mul ×Δf _DDM ). can be used to estimate the number of Doppler foldovers.

For example, the Doppler determination unit 213, for example, among the Doppler analysis corresponding to the first chirp signal and the Doppler analysis corresponding to the second chirp signal, the result of one Doppler analysis in which a plurality of reflected wave signals are separated is estimating the Doppler peaks of each of the plurality of targets in the other Doppler analysis in which the plurality of reflected wave signals are not separated, and based on the estimated Doppler peak interval between the plurality of targets and the Doppler multiplexing interval , the number of Doppler frequency loopbacks of each of a plurality of targets is determined.

In the present embodiment, subsequent processing of the radar device 10 may be the same as in the first embodiment. Also, the radar device 10 may output the Doppler frequency estimation value as the positioning output, for example, using the estimated Doppler turn-around times, n _{alest_#T1} and n _{alest_#T2} . As described above, in the present embodiment, the radar apparatus 10 uses the center frequency f _c (1) of the first chirp signal and the center frequency f _c (2) of the second chirp signal that satisfy the second determination condition, The effects of the first embodiment can be obtained.

Furthermore, in the radar device 10, for example, the Doppler frequencies of the reflected waves from the two targets arrive at Doppler frequency intervals equal to the Doppler multiplexing interval Δf _DDM (or the multiple of the Doppler multiplexing interval N _mul ×Δf _DDM ), Doppler demultiplexing of those targets using chirp signals of . Even in this case, the radar apparatus 10, regarding the other chirp signal, sets the Doppler frequencies of the reflected waves from the two targets to a Doppler multiplexing interval Δf _DDM (or a multiple of the Doppler multiplexing interval N _mul ×Δf _DDM ). Doppler demultiplexing of the two targets can be performed by making the frequency interval different from at least the Doppler resolution of the Doppler analysis unit 210 .

As a result, in the present embodiment, the radar device 10 can improve the detection performance of a plurality of waves arriving from the same distance, improve the target detection probability in the radar device 10, reduce the non-detection probability, and improve the radar detection performance. can be improved.

(Modification of Embodiment 2)
As a modification of the second embodiment, when the assumed target Doppler frequency f _{d_TargetDoppler} is in the Doppler frequency range of −1/(2T _rs )≦f _{d_TargetDoppler} <1/(2T _rs ), the radar device 10 Using the center frequency f _c (1) of the first chirp signal and the center frequency f _c (2) of the second chirp signal that satisfy the second determination condition, the Doppler determination unit 213 performs processing omitting the folding number estimation processing. you can go For example, the radar device 10 may perform separation detection processing of a plurality of reflected waves without estimating the number of times of return.

In this case, the Doppler determination unit 213 may perform the following case 1a and case 2a processes instead of the above-described case 1 and case 2 processes, for example.

<Case 1a>
In case 1a, for example, the distance index f _{b_cfar} includes a plurality of demultiplexing index information of the Doppler multiplexed signal output from the first Doppler demultiplexing unit 212, and the Doppler multiplexing output from the second Doppler demultiplexing unit 212 is included. This is the case where the signal separation index information is not included, for example, the following case.

When there are two reflected waves from the same distance from the radar device 10, the separation index information of the Doppler multiplexed signal output from the first Doppler demultiplexer 212 and the output from the second Doppler demultiplexer 212 It is expected that the separation index information of the Doppler multiplexed signals for the two reflected waves will be output as the separation index information of the Doppler multiplexed signals.

However, by transmitting using the second chirp signal, the reflected wave #1 and the reflected wave #2 are Doppler multiplexing interval Δf _DDM or a multiple of the Doppler multiplexing interval, as shown in (c) of FIG. 1, for example. , a portion of the Doppler multiplexed signal may be received as overlapping Doppler frequency components between reflected wave #1 and reflected wave #2.

Therefore, it becomes difficult to demultiplex the Doppler multiplexed signal, and the demultiplexing index information of the Doppler multiplexed signal output from the second Doppler demultiplexer 212 may not be included. On the other hand, even if such a reflected wave exists, the radar device 10 satisfies the second determination condition by transmitting using the first chirp signal, so the reflected wave #1 and the reflected wave #2 are the same. Doppler-multiplexed signals in some parts are no longer received as duplicated Doppler frequency components.

Therefore, there is a case where the demultiplexing index information of the Doppler multiplexed signal output from the first Doppler demultiplexer 212 is included (assuming a case where reflected waves #1 and #2 similar to case 1 arrive). In such a case, operations different from Case 1 will be described below.

In the following, as an example, as the demultiplexing index information of the Doppler multiplexed signal output from the first Doppler demultiplexer 212, the Doppler multiplexed signals of the reflected waves from two targets (for example, Target#1 and Target#2) A case where separation index information is included will be described.

For example, when using a chirp signal with a center frequency f _c (2), the Doppler determination unit 213 determines Doppler frequencies f _{d2_T#1} and f _{d2_T#} of reflected waves from two targets (Target#1 and Target#2). ₂ arrived at a Doppler frequency interval equal to the Doppler multiplexing interval Δf _DDM (or a multiple of the Doppler multiplexing interval N _mul ×Δf _DDM ). In this case, Doppler determining section 213 may output demultiplexing index information of the Doppler multiplexed signal output from first Doppler demultiplexing section 212 to direction estimating section 214, for example.

The direction estimation unit 214 performs direction estimation processing using the distance index f _{b_cfar} output from the first Doppler demultiplexing unit 212 and the demultiplexing index information of the Doppler multiplexed signal (q=1). The direction estimation unit 214 may perform direction estimation processing using q=1 in Equation (21), for example.

<Case 2a>
In case 2a, for example, the distance index f _{b_cfar} includes a plurality of demultiplexing index information of the Doppler multiplexed signal output from the second Doppler demultiplexing unit 212, and the Doppler multiplexing output from the first Doppler demultiplexing unit 212 is included. This is the case where the signal separation index information is not included, for example, the following case.

When there are two reflected waves from the same distance from the radar device 10, the separation index information of the Doppler multiplexed signal output from the first Doppler demultiplexer 212 and the output from the second Doppler demultiplexer 212 It is expected that the separation index information of the Doppler multiplexed signals for the two reflected waves will be output as the separation index information of the Doppler multiplexed signals.

However, when transmitted using the first chirp signal, reflected wave #1 and reflected wave #2 coincide with the Doppler multiplexing interval Δf _DDM or a multiple of the Doppler multiplexing interval, as shown in (c) of FIG. In this case, some Doppler multiplexed signals may be received as overlapping Doppler frequency components between reflected waves #1 and #2.

Therefore, it becomes difficult to demultiplex the Doppler multiplexed signal, and the demultiplexed index information of the Doppler multiplexed signal output from the first Doppler demultiplexer 212 may not be included.

On the other hand, even if such a reflected wave exists, the radar device 10 satisfies the second determination condition by transmitting using the second chirp signal, so the reflected wave #1 and the reflected wave #2 are the same. Doppler-multiplexed signals in some parts are no longer received as duplicated Doppler frequency components. Therefore, there is a case where the demultiplexing index information of the Doppler multiplexed signal output from the second Doppler demultiplexing unit 212 is included (assuming a case where reflected waves #1 and #2 similar to case 2 arrive). In such a case, operations different from Case 2 will be described below.

In the following, as an example, as the demultiplexing index information of the Doppler multiplexed signal output from the second Doppler demultiplexer 212, the Doppler multiplexed signals of the reflected waves from two targets (for example, Target#1 and Target#2) A case where separation index information is included will be described.

For example, when using a chirp signal with a center frequency f _c (1), the Doppler determination unit 213 determines Doppler frequencies f _{d1_T#1} and f _{d1_T#} of reflected waves from two targets (Target#1 and Target#2). ₂ arrived at a Doppler frequency interval equal to the Doppler multiplexing interval Δf _DDM (or a multiple of the Doppler multiplexing interval N _mul ×Δf _DDM ). In this case, Doppler determining section 213 may output demultiplexing index information of the Doppler multiplexed signal output from second Doppler demultiplexing section 212 to direction estimating section 214, for example.

The direction estimation unit 214 performs direction estimation processing using the distance index f _{b_cfar} output from the second Doppler demultiplexing unit 212 and the demultiplexing index information of the Doppler multiplexed signal (q=2). The direction estimation unit 214 may perform direction estimation processing using q=2 in Equation (21), for example.

Case 1a and case 2a have been described above.

Thus, in the Doppler frequency range where the target Doppler frequency f _{d_TargetDoppler} is -1/(2T _rs ) ≤ f _{d_TargetDoppler} < 1/(2T _rs ), the center frequency f of the first chirp signal that satisfies the second decidability condition is satisfied. The following effects can be obtained by using _c (1) and the center frequency f _c (2) of the second chirp signal.

For example, the Doppler frequencies of reflected waves from two targets arrive at a Doppler frequency interval that is the Doppler multiplex interval Δf _DDM (or a multiple of the Doppler multiplex interval N _mul ×Δf _DDM ), and one target based on the chirp signal Doppler demultiplexing of . Even in this case, by using the other chirp signal (chirp signal with a different center frequency), the interval between the Doppler frequencies of the reflected waves from the two targets can be changed to the Doppler multiplexing interval Δf _DDM (or a multiple of the Doppler multiplexing interval N _mul ×Δf _DDM ), and can be set to an interval larger than at least the Doppler resolution of the Doppler analysis unit 210 . Therefore, the radar system 10 enables Doppler demultiplexing of two targets.

As described above, in the modification of the second embodiment, the radar apparatus 10 performs Doppler analysis on one of the Doppler analysis on the first chirp signal and the Doppler analysis on the second chirp signal. A direction estimation process may be performed based on the results of the analysis.

As a result, for example, in the Doppler analysis of the reflected wave signal corresponding to one chirp signal, the interval between the Doppler frequencies (Doppler peaks) corresponding to a plurality of reflected waves at approximately the same distance from the radar device 10 is Doppler multiplexed. Even if the interval (or a multiple of the Doppler multiplexing interval) matches, the radar apparatus 10 performs Doppler multiplexing corresponding to each of the plurality of reflected waves based on the Doppler analysis result of the reflected wave signal corresponding to the other chirp signal. Signals can be separated and detected.

Thus, in the modified example of the second embodiment, the radar device 10 can improve the detection performance of a plurality of reflected waves arriving from the same distance, improve the target detection probability in the radar device 10, and reduce the non-detection probability. can be reduced. Therefore, according to the modification of the second embodiment, the radar detection performance of the radar device 10 can be improved.

(Embodiment 3)
In Embodiment 1, a configuration example of the radar device including one radar transmission signal generation unit was shown, but the configuration of the radar device is not limited to this, and a radar device including a plurality of radar transmission signal generation units may be used. may be used.

For example, FIG. 11 shows a configuration example including two radar transmission signal generators 101 in the radar transmitter 100a of the radar device 10a. In Embodiment 1, the radar device 10 is configured to include one radar transmission signal generator 101, and the radar transmission waves (for example, chirp signals) of different center frequencies are temporally switched for each transmission period _Tr . , alternately transmitting. On the other hand, in the present embodiment, as shown in FIG. 11, a radar device 10a including a plurality of radar transmission signal generators 101 transmits radar transmission waves (for example, chirp signals) with different center frequencies. Transmission is performed simultaneously from a plurality of transmission antennas 106 for each period _Tr . Even with such a configuration, the effect of expanding the detectable Doppler frequency range can be obtained, as in the first embodiment.

Hereinafter, regarding the operation in the present embodiment, an operation example different from that in the first embodiment will be mainly described.

[Configuration example of radar transmission unit 100a]
FIG. 11 shows, as an example, a configuration including two radar transmission signal generators 101 in the radar transmitter 100a of the radar device 10a. In the following, the two radar transmission signal generation units 101 are respectively referred to as “first radar transmission signal generation unit 101 (or radar transmission signal generation unit 101-1)” and “second radar transmission signal generation unit 101- 2 (or radar transmission signal generator 101-2)”.

In FIG. 11, the configuration of each radar transmission signal generator 101 may be the same as in the first embodiment. Each radar transmission signal generation unit 101 generates a radar transmission signal based on control from the signal generation control unit 104, for example.

The signal generation control section 104 controls the first and second radar transmission signal generation sections 101 (for example, the modulation signal generation section 102 and the VCO 103) to generate radar transmission signals. For example, the signal generation control unit 104 sets parameters (for example, modulation parameters) related to chirp signals so that chirp signals with different center frequencies are transmitted from each of the first and second radar transmission signal generation units 101. good. Hereinafter, the chirp signal generated by the first radar transmission signal generator 101 will be called "first chirp signal", and the chirp signal generated by the second radar transmission signal generator 101 will be called "second chirp signal".

As in Embodiment 1, the modulation parameters for the chirp signal include, for example, the center frequency f _c (q), the frequency sweep bandwidth B _w (q), the sweep start frequency f _cstart (q), the sweep end frequency f _cend (q), frequency sweep time T _sw (q), and frequency sweep change rate D _m (q). Note that D _m (q)=B _w (q)/T _sw (q). Also, B _w (q)=f _cend (q)−f _cstart (q) and f _c (q)=(f _cstart (q)+f _cend (q))/2. Also, for example, q=1,2, where q=1 may represent the modulation parameter of the first chirp signal, and q=2 may represent the modulation parameter of the second chirp signal.

Signal generation control section 104 may set (or select) center frequency f _c (q) that satisfies a predetermined condition, for example, as in the first embodiment. In the following, as an example, of the modulation parameters set for the first chirp signal and the second chirp signal, the center frequencies f _c (q) are different from each other, and the modulation parameters other than the center frequencies are the same ( or common) will be described. However, it is not limited to this, and for the application of an embodiment of the present disclosure, for example, the first chirp signal and the second chirp signal need only have the same resolution in the distance axis, so the frequency sweep bandwidth B _w (q ) are set to have the same relationship.

Further, the signal generation control unit 104 controls the modulation signal generation unit 102 and the VCO 103 so that, for example, two chirp signals with different center frequencies f _c (q) are simultaneously transmitted (or output) Nc times. You can control it.

FIG. 12 shows an example of chirp signals (for example, a first chirp signal and a second chirp signal) output by the first and second radar transmission signal generators 101 under the control of the signal generation controller 104 . Although FIG. 12 shows an example of an up-chirp waveform in which the modulation frequency gradually increases over time, it is not limited to this, and a down-chirp in which the modulation frequency gradually decreases over time is applied. good too. A similar effect can be obtained regardless of whether the modulation frequency is up-chirp or down-chirp.

In FIG. 12, the first chirp signal and the second chirp signal are transmitted simultaneously with a transmission period T _r . In the following, unless otherwise specified, the frequency sweep bandwidth, frequency sweep time (or range gate), and frequency sweep change rate are for each of the first chirp signal and the second chirp signal. represent parameters of the same value, B _w (1)=B _w (2)=B _w , T _sw (1)=T _sw (2)=T _sw , D _m (1)=D _m (2)=D Sometimes expressed as _m .

Also, the frequency sweep bandwidths of the chirp signals with different center frequencies may not include overlapping bands as shown in FIG. It may include a band. One embodiment of the present disclosure, for example, if the center frequency relationship between the first chirp signal and the second chirp signal satisfies a predetermined condition, regardless of whether the frequency sweep bandwidth includes overlapping bands, , a similar effect is obtained.

In one embodiment of the present disclosure, the transmission cycle T _r may be set to, for example, several hundred microseconds or less, and the transmission time interval of the radar transmission signal may be set relatively short. As a result, for example, even if the center frequencies of the first chirp signal and the second chirp signal are different, the frequency of the beat signal of the received reflected wave (for example, the beat frequency index) does not change. It is detectable as a change in Doppler frequency.

The first chirp signal output from the first radar transmission signal generator 101 (eg, VCO 103) is generated by, for example, N1 Doppler shifters 105 (eg, Doppler shifter 105- 1 to 105-N1). Further, the first chirp signal output from the first radar transmission signal generation unit 101 is generated by, for example, N3 mixer units 204 (for example, the antenna system processing unit 201) among the Na mixer units 204 of the radar reception unit 200a. -1 to 201-N3 are input to the mixer units 204), respectively.

On the other hand, the second chirp signal output from the second radar transmission signal generator 101 (for example, VCO 103) is generated by N2 Doppler shifters 105 (for example, Doppler shifter 105) out of Nt Doppler shifters 105, for example. 105-N1+1 to 105-Nt). Further, the second chirp signal output from the second radar transmission signal generation unit 101 is generated by, for example, N4 mixer units 204 (for example, the antenna system processing unit 201) among the Na mixer units 204 of the radar reception unit 200a. -N3+1 to 201-Na).

Here, N1+N2=Nt and N3+N4=Na. N1 and N2 may each be 2 or more, and Nt may be 4 or more. Also, N3 and N4 may each be 1 or more, and Na may be 2 or more.

Then, the output signals of N1 Doppler shift units 105 to which the first chirp signal is input are amplified to a predetermined transmission power and radiated into space from each transmission antenna 106 (for example, Tx#1 to Tx#N1). . Further, the output signals of N2 Doppler shift units 105 to which the second chirp signals are input are amplified to a predetermined transmission power and radiated into space from each transmission antenna 106 (for example, Tx#N1+1 to Tx#Nt). be done. As a result, the first chirp signal and the second chirp signal are transmitted at the same time every transmission period _Tr .

In the following, N1 Doppler shift units 105 (for example, Doppler shift units 105-1 to 105-N1) to which the first chirp signal is input, and each transmission for transmitting the output signals of these N1 Doppler shift units 105 Antennas 106 (eg, Tx#1 to Tx#N1) are referred to as the "first transmit sub-block." Also, N2 Doppler shift units 105 to which the second chirp signal is input (for example, Doppler shift units 105-N1+1 to 105-Nt), and each transmitting antenna for transmitting the output signals of these N2 Doppler shift units 105 106 (for example, Tx#N1+1 to Tx#Nt) are called "second transmission sub-blocks".

For example, the Doppler shift unit 105 included in the first transmission sub-block gives phase rotation φ _nsub1 to the first chirp signal in order to give the Doppler shift amount DOP _nsub1 for each chirp signal transmission cycle T _r . and outputs the Doppler-shifted signal to the transmitting antenna 106 (for example, Tx#1 to Tx#N1). Here, nsub1=an integer from 1 to N1. Also, the Doppler shifter 105 included in the second transmission sub-block imparts a phase rotation φ _nsub2 to the second chirp signal in order to impart a Doppler shift amount DOP _nsub2 for each chirp signal transmission period _Tr . and outputs the Doppler-shifted signal to the transmitting antenna 106 (for example, Tx#N1+1 to Tx#Nt). Here, nsub2=an integer from 1 to N2.

The Doppler shift amount DOP _nsub1 (or phase rotation φ _nsub1 ) and the Doppler shift amount DOP _nsub2 (or phase rotation φ _nsub2 ) in the Doppler shift unit 105 included in the first and second transmission sub-blocks are given. An example method is described below.

Also, when Nt is an even number, the number of transmission antennas 106 included in the first and second transmission sub-blocks may be the same, for example, by setting N1=N2. Also, when Nt is an odd number, for example, by setting N1=(Nt+1)/2 or N1=(Nt-1)/2, the transmission antennas 106 included in the first and second transmission sub-blocks may be approximately equal to one transmit antenna difference. Thus, the number of transmit antennas 106 included in the first sub-block (eg, the transmit antennas 106 transmitting the first chirp signal) and the number of transmit antennas 106 included in the second transmit sub-block (eg, the second chirp signal) The number of transmit antennas 106) for transmitting the may be set to be the same or differ by one. By setting the number of transmitting antennas 106 included in the first and second sub-blocks to be the same or substantially the same, the radar apparatus 10a uses the first chirp signal and the second chirp signal to perform Doppler multiplexing when performing Doppler multiplexing. It is possible to obtain the effect of further enlarging the interval (for example, the effect of enlarging it by about two times) as compared with the first embodiment.

Further, in Embodiment 1, the first chirp signal and the second chirp signal are switched in a time division manner (for example, the first chirp signal and the second chirp signal are alternately transmitted at each transmission period _Tr ). Thus, Doppler multiplexed signals are multiplexed in the Doppler frequency range ±1/2T _rs where T _rs >T _r . On the other hand, in the present embodiment, as shown in FIG. 12, the first chirp signal and the second chirp signal are transmitted at the same time every transmission cycle T _r , so that the Doppler frequency range ±1/2 T _r Doppler multiplexing signals can be multiplexed. For example, compared to the case of Doppler multiplex transmission with T _rs =2T _r in Embodiment 1, this embodiment enables multiplex transmission of Doppler multiplexed signals in a Doppler frequency range twice as large. Therefore, by setting the number of transmission antennas 106 included in the first and second transmission sub-blocks to be the same or approximately the same, the Doppler multiplexing interval when Doppler multiplexing is performed using the first chirp signal and the second chirp signal is As compared with the first embodiment, the effect of enlarging about four times is obtained.

For example, if the Doppler multiplexing intervals are close when Doppler multiplexing is performed, interference between Doppler multiplexed signals is likely to occur in the case of a target whose Doppler component is spread out, and the accuracy of direction estimation deteriorates. detection accuracy tends to deteriorate. In this embodiment, since the Doppler multiplexing interval can be expanded when Doppler multiplexing is performed, it is possible to reduce the occurrence of such interference between Doppler multiplexed signals, and it is possible to suppress the deterioration of the direction estimation accuracy and the deterioration of the target detection accuracy. .

In addition, in this embodiment, since the Doppler multiplexing interval can be expanded when Doppler multiplexing is performed, even if more transmitting antennas 106 are used for Doppler multiplexing, the occurrence of interference between Doppler multiplexed signals can be reduced and direction estimation can be performed. It is possible to suppress deterioration of accuracy and deterioration of target detection accuracy. Therefore, in this embodiment, more transmitting antennas 106 can be used for Doppler multiplexing than in the first embodiment. In this way, when Doppler multiplexing is performed using more transmitting antennas 106, this embodiment is more suitable than the first embodiment.

[Configuration Example of Radar Receiver 200a]
In FIG. 11, the radar receiving section 200a comprises, for example, Na receiving antennas 202 (eg, Rx#1 to Rx#Na) to form an array antenna. Further, the radar receiving unit 200a includes, for example, Na antenna system processing units 201-1 to 201-Na, a CFAR unit 211, a Doppler demultiplexing unit 212, a Doppler determination unit 213, a direction estimation unit 214, have

Each receiving antenna 202 receives a reflected wave signal that is a radar transmission signal (for example, a first chirp signal and a second chirp signal) reflected by a target, and transmits the received reflected wave signal to the corresponding antenna system. It is output to the processing unit 201 as a received signal.

Each antenna system processing section 201 has a receiving radio section 203 and a signal processing section 206 .

Receiving radio section 203 has mixer section 204 and LPF 205 . In reception radio section 203, mixer section 204 mixes the received reflected wave signal (reception signal) with a chirp signal, which is a transmission signal.

Here, the first chirp signal output from the first radar transmission signal generator 101-1 (for example, the VCO 103) is generated by the N3 antenna system processors 201 (for example, out of the Na antenna system processors 201). For example, they are input to mixer units 204 of antenna system processing units 201-1 to 201-N3). In the antenna system processing units 201-1 to 201-N3, by passing the output of the mixer unit 204 through the LPF 205, the output of the mixer unit 204 corresponding to the reflected wave of the second chirp signal is out of the passband of the LPF 205. Since the frequency is high, the LPF 205 easily outputs a beat signal having a frequency corresponding to the delay time of the reflected wave signal of the first chirp signal.

Similarly, the second chirp signal output from the second radar transmission signal generator 101-2 (for example, the VCO 103) is generated by the N4 antenna system processors 201 (for example, out of the Na antenna system processors 201). For example, they are input to the mixer units 204 of the antenna system processing units 201-N3+1 to 201-Na). In the antenna system processing units 201-N3+1 to 201-Na, by passing the output of the mixer unit 204 through the LPF 205, the output of the mixer unit 204 corresponding to the reflected wave of the first chirp signal is out of the passband of the LPF. Since the frequency is high, the LPF 205 easily outputs a beat signal having a frequency corresponding to the delay time of the reflected wave signal of the second chirp signal.

Therefore, the antenna system processing units 201-1 to 201-N3 process the reflected wave signals of the first chirp signals received by the receiving antennas 202-1 to 202-N3. After that, connect to the antenna system processing unit 201 (for example, the reception radio unit 203 and the signal processing unit 206) that processes the reflected wave of the first chirp signal, and the antenna system processing unit 201 that processes the reflected wave of the first chirp signal. The received antenna 202 is called a "first receive sub-block".

Further, the antenna system processing units 201-N3+1 to 201-Na process reflected wave signals of the second chirp signals received by the receiving antennas 202-N3+1 to 202-Na. After that, connect to the antenna system processing unit 201 (for example, the reception radio unit 203 and the signal processing unit 206) that processes the reflected wave of the second chirp signal, and the antenna system processing unit 201 that processes the reflected wave of the second chirp signal. The received antenna 202 is called a "second receive sub-block".

Here, N3+N4=Na. Incidentally, N3 and N4 may each be 1 or more, and Na may be 2 or more.

The signal processing section 206 of each antenna system processing section 201 -z _q included in the q-th reception sub-block has an A/D conversion section 207 , a beat frequency analysis section 208 and a Doppler analysis section 210 . Here, when q=1, z ₁ = any of 1 to N3, and when q=2, z ₂ = any of N3+1 to Na.

A signal (for example, a beat signal) output from the LPF 205 is converted into discrete sample data that is discretely sampled by the A/D conversion section 207 in the signal processing section 206 .

A beat frequency analysis unit 208 included in the q-th reception sub-block performs FFT processing on N _data pieces of discrete sample data obtained in a predetermined time range (range gate) at each transmission cycle Tr. Here, the range gate sets the frequency sweep time T _sw (q). For example, q=1,2, where T _sw (1) represents the frequency sweep time of the first chirp signal when q=1, and T _sw (2) represents the frequency sweep time of the second chirp signal when q=2. represents the frequency sweep time of the signal. As a result, the signal processing unit 206 outputs a frequency spectrum in which a peak appears at the beat frequency corresponding to the delay time of the reflected wave signal (radar reflected wave). Note that the beat frequency analysis unit 208 may multiply window function coefficients such as a Han window or a Hamming window during FFT processing. Side lobes generated around the beat frequency peak can be suppressed by using the window function coefficients.

Here, the beat frequency response output from the beat frequency analysis section 208 in the _zq -th signal processing section 206 of the q-th reception sub-block obtained by transmitting the m-th chirp pulse of the q-th chirp signal is referred to as "RFT _zq (f _b , m)”. where f _b represents the beat frequency index and corresponds to the FFT index (bin number). For example, f _b = 0, ~, N _data /2-1, z ₁ = 1 ~ N3, z ₂ = N3 + 1 ~ Na, m = 1, ~, N _C and q = 1 or 2. . A smaller beat frequency index f _b indicates a beat frequency with a shorter delay time of the reflected wave signal (eg, closer to the target).

The Doppler analysis unit 210 in the _zq -th signal processing unit 206 of the q- _th reception sub-block calculates the beat frequency response RFT _zq (f _b , 1), RFT Doppler analysis is performed for each distance index f _b using _{z q} (f _b , 2), ˜, RFT z q ₍ f _b , N _C ). For example, the Doppler analysis unit 210 of the q-th reception sub-block may estimate the Doppler frequency from the reflected wave signal of the q-th chirp signal reflected from the target.

For example, if _Nc is a power of 2, FFT processing can be applied in Doppler analysis. In this case, the FFT size is N _c , and the maximum Doppler frequency without aliasing derived from the sampling theorem is ±1/(2T _r ). Also, the Doppler frequency interval of the Doppler frequency index _fs is 1/( _Nc × _Tr ), and the range of the Doppler frequency index _fs is _fs = _-Nc /2, ~, 0, ~, _Nc / 2-1.

A case where N _c is a power of 2 will be described below as an example. If N _c is not a power of 2, for example, FFT processing can be performed with a data size of powers of 2 by including zero-padded data. Also, the Doppler analysis unit 210 may multiply window function coefficients such as a Han window or a Hamming window during FFT processing. By applying the window function, side lobes generated around the beat frequency peak can be suppressed.

For example, the output VFT _zq (f _b , f _s ) of the Doppler analysis section 210 in the z _q -th signal processing section 206 of the q-th reception sub-block is given by the following equation (60). Note that j is an imaginary unit, z ₁ =1 to N3, z ₂ =N3+1 to Na, and q=1,2.

The processing in each component of the signal processing unit 206 has been described above.

The CFAR unit 211 includes, for example, a first CFAR unit 211 (or a CFAR unit 211-1) and a second CFAR unit 211 (or a CFAR unit 211-1) corresponding to a first chirp signal and a second chirp signal having different center frequencies. 2). Similarly, the Doppler demultiplexing unit 212 includes, for example, a first Doppler demultiplexing unit 212 (or a Doppler demultiplexing unit 212-1) and a second A 2-Doppler demultiplexer 212 (or Doppler demultiplexer 212-2) may be provided.

Although FIG. 11 shows a configuration in which CFAR units 211 are provided in parallel (CFAR units 211-1 and 211-2), one CFAR unit 211 is provided and its input is sequentially switched for processing. It's okay. FIG. 11 shows a configuration in which Doppler demultiplexers 212 are provided in parallel (Doppler demultiplexers 212-1 and 212-2). may be configured to switch to and process.

In FIG. 11, CFAR section 211 performs CFAR processing (for example, adaptive threshold determination) using the output from Doppler analysis section 210 of signal processing section 206 included in the q-th received sub-block, and local Extract the range index f _{b_cfar} and the Doppler frequency index f _{s_cfar} that gives the peak signal.

As shown in FIG. 11, CFAR section 211 performs CFAR processing using the output of Doppler analysis section 210 of signal processing section 206 included in the first reception sub-block (or CFAR section 211-1 ), and a second CFAR unit 211 (or CFAR unit 211-2) that performs CFAR processing using the output of the Doppler analysis unit 210 of the signal processing unit 206 included in the second reception sub-block. good.

The q-th CFAR unit 211 (q=1, 2) adds the power of the output of the Doppler analysis unit 210 of the signal processing unit 206 included in the q-th reception sub-block, for example, as shown in the following equation (61), and Doppler frequency axis (corresponding to relative velocity), or CFAR processing combining one-dimensional CFAR processing. For CFAR processing that combines two-dimensional CFAR processing or one-dimensional CFAR processing, for example, the processing disclosed in Non-Patent Document 2 may be applied.
Here, z ₁ =1 to N3, z ₂ =N3+1 to Na.

The q-th CFR section 211 adaptively sets a threshold, and uses the distance index f _{b_cfar} (q), the Doppler frequency index f _{s_cfar} (q), and the received power information PowerFT(f _{b_cfar} (q ), f _{s_cfar} (q)) to the q-th Doppler demultiplexer 212 .

The Doppler demultiplexing unit 212 performs Doppler demultiplexing processing using the outputs of the Doppler analysis unit 210 and the first CFAR unit 211 of the signal processing unit 206 included in the first reception sub-block (or , Doppler demultiplexing unit 212-1), Doppler analysis unit 210-2 of signal processing unit 206 included in the second reception sub-block, and outputs of second CFAR unit 211 are used to perform Doppler demultiplexing processing. A 2-Doppler demultiplexer 212 (or represented as a Doppler demultiplexer 212-2) may be provided.

The q-th Doppler demultiplexing unit 212 (q=1, 2) receives information input from the q-th CFAR unit 211 (for example, distance index f _{b_cfar} (q), Doppler frequency index f _{s_cfar} (q), and received power information Based on PowerFT (f _{b_cfar} (q), f _{s_cfar} (q))), using the output from the Doppler analysis unit 210 included in the q-th reception sub-block, Doppler multiplexed signals (hereinafter referred to as “Doppler multiplex signal”) from each transmit antenna 106 (eg, a reflected wave signal for that transmit signal).

The q-th Doppler demultiplexer 212 outputs, for example, information about the demultiplexed signal to the Doppler determiner 213 and the direction estimator 214 . Information about the separated signal may include, for example, a distance index f _{b_cfar} (q) corresponding to the separated signal and a Doppler frequency index (hereinafter also referred to as separation index information). Here, the demultiplexing index information of the first Doppler demultiplexing unit 212 is the Doppler frequency index obtained by demultiplexing the signals transmitted from the transmitting antennas Tx#1, Tx#2, . , which are respectively represented as (f _{demul_Tx#1} , f _{demul_Tx#2} , ~, f _{demul_Tx#N1} ). Similarly, the demultiplexing index information of the second Doppler demultiplexing unit 212 demultiplexes the signals transmitted from the transmitting antennas Tx#N1+1, Tx#N1+2, . are Doppler frequency indices, and are respectively represented by (f _{demul_Tx#N1+1} , f _{demul_Tx#N1+2} , ~, f _{demul_Tx#Nt} ).

The q-th Doppler demultiplexer 212 also outputs the output from the q-th Doppler analyzer 210 to the direction estimator 214 . Note that the q-th Doppler demultiplexing unit 212 receives information input from the q-th CFAR unit 211 (for example, distance index f _{b_cfar} (q), Doppler frequency index f _{s_cfar} (q), and received power information PowerFT(f _{b_cfar} ( q), f _{s_cfar} (q))), the output from Doppler analysis section 210 included in the q-th received sub-block may be output to direction estimation section 214 .

The operation of the q-th Doppler demultiplexer 212 will be described below together with the operation of the Doppler shifter 105 in the radar transmitter 100a.

[How to set Doppler shift]
Doppler shift units 105-1 to 105-N1 included in the first transmission sub-block perform phase rotation to give the first chirp signal a Doppler shift amount DOP _nsub1 for each chirp signal transmission _period Tr. φ _nsub1 is added, and the Doppler-shifted signal is output to the transmitting antenna 106 (for example, Tx#1 to Tx#N1). Here, nsub1=1 to N1. In this embodiment, between the Doppler shift units 105-1 to 105-N1 (or between the transmitting antennas 106-1 to 106-N1), the interval of the Doppler shift amount DOP _nsub1 (Doppler shift interval) is equal to Instead, at least one Doppler interval may be set at unequal intervals.

For example, the nsub1-th Doppler shift unit 105 gives the input m-th first chirp signal a phase rotation φ _nsub1 (m) with different Doppler shift amounts DOP _nsub1 and outputs it. As a result, transmission signals transmitted from a plurality of transmission antennas 106 are given different Doppler shift amounts. For example, in the present embodiment, the Doppler multiplex number N _DM =N1. Here, m=an integer from 1 to N _C and nsub1=an integer from 1 to N1.

Similarly, Doppler shift units 105-N1+1 to 105-Nt included in the second transmission sub-block provide the second chirp signal with a Doppler shift amount DOP _nsub2 for each chirp signal transmission period _Tr . , phase rotation φ _nsub2 is applied, and the Doppler-shifted signal is output to the transmitting antenna 106 (for example, Tx#N1+1 to Tx#Nt). Here, nsub2=1 to N2. In this embodiment, between the Doppler shift units 105-N1+1 to 105-Nt (or between the transmitting antennas 106-N1+1 to 106-Nt), the interval of the Doppler shift amount DOP _nsub2 (Doppler shift interval) is equal to Instead, at least one Doppler interval may be set at unequal intervals.

Thus, by setting the Doppler shift amount in Doppler shift section 105 for the first and second transmission sub-blocks, first Doppler demultiplexing section 212 operates in the same manner as Doppler demultiplexing section 212 in Embodiment 1. , the Doppler indices of Tx#1 to Tx#N1 can be separated, and the Doppler frequencies can be calculated within the range of ±1/T _r . Further, the second Doppler demultiplexing unit 212 described later separates the Doppler indices Tx#N1+1 to Tx#Nt by the same operation as the Doppler demultiplexing unit 212 in Embodiment 1, and ±1/T _r Doppler frequency can be calculated in the range of Based on these outputs of the Doppler demultiplexing unit 212, the Doppler determination unit 213, which will be described later, performs the same operation as the Doppler determination unit 213 in Embodiment 1, and determines the presence or absence of Doppler frequency folding based on the Doppler frequency difference. can be determined and the Doppler frequency over the range of ±1/T _r can be calculated.

The operations of Doppler shift units 105-1 to 105-N1 included in the first transmission sub-block are the same as those between Doppler shift units 105-1 to 105-Nt (or transmission antennas 106-1 to 106-Nt) in Embodiment 1. In the explanation of the operation of the interval), the operation is the same as the operation in which "Nt" is replaced with "N1" and " _Trs " is replaced with " _Tr ", so the detailed explanation of the operation will be omitted.

Further, the operation of Doppler shift units 105-N1+1 to 105-Nt included in the second transmission sub-block is similar to that between Doppler shift units 105-N1+1 to 105-Nt (or transmission antennas 106-N1+1 to 106 -Nt), the operation is the same as that in which "Nt" is replaced with "N2" and "T _rs " is replaced with "T _r ", so a detailed description of the operation will be omitted. .

For example, in relation to Equation (5) described in Embodiment 1, in this embodiment, Doppler shift sections 105-1 to 105-N1 of the first transmission sub-block are input m-th A phase rotation φ _nsub1 (m) given by the following equation (62) is given to one chirp signal so that the Doppler shift amounts DOP _nsub1 differ between the Doppler shift sections 105 .

Similarly, the Doppler shift sections 105-N1+1 to 105-Nt of the second transmission sub-block apply Doppler shift amounts DOP _nsub2 A phase rotation φ _nsub2 (m) such as the following equation (63) is given.

Here, A is a coefficient that gives a positive/negative polarity of 1 or -1. Also, .delta.1 and .delta.2 are integers of 1 or more. The terms round( _NC /(N1+δ1)) and round( _NC /(N2+δ2)) are introduced for the purpose of setting the amount of phase rotation to be an integral multiple of the Doppler frequency interval in the Doppler analysis unit 210. , but not limited thereto, and 2π/(N1+δ1) may be used instead of the term (2π/N _C )×round(N _C /(N1+δ1)) in equation (62). Similarly, 2π/(N2+δ2) may be used instead of the term (2π/N _C )×round(N _C /(N2+δ2)) in equation (63).

Also, φ ₀₁ and φ ₀₂ are initial phases, and may be the same or different. For example, the Doppler frequencies match whether φ ₀₁ and φ ₀₂ are equal or different. Δφ ₀₁ and Δφ ₀₂ are reference Doppler shift phases, which may be equal or different. For example, the Doppler frequencies match whether Δφ ₀₁ and Δφ ₀₂ are equal or different.

For example, the radar device 10a performs unequal interval Doppler multiplexing on the first chirp signal and the second chirp signal with the Doppler multiplexing numbers N1 and N2, respectively.

In _the following, the Doppler multiplexing interval " _{ΔDOP min1} ”. Similarly, the Doppler multiplexing interval "ΔDOP _min2 " of the Doppler multiplexed signal that allocates (2π/N _C )×round(N _C /(N2+δ2)) or 2π/(N2+δ2) in Equation (63) to the second chirp signal call.

As an example when the number of transmitting antennas Nt = 4, in Equation (62), N1 = 2, Δφ ₀₁ = 0, φ ₀₁ = 0, A = 1, δ1 = 1, N _C is a multiple of 3, and the phase rotation is φ _nsub1 (m)=2π(nsub1−1)×(m−1)/3 is added to the first chirp signal every transmission period _Tr , so the Doppler shift amount is DOP ₁ =φ ₁ (m) /{2π(m−1)T _r }=0, DOP ₂ =φ ₂ (m)/{2π(m−1)T _r }=1/(3T _r ). Each upper part of (a) to (d) of FIG. 13 shows an arrangement example of Doppler multiplexed signals when transmitting the first chirp signal.

Further, as an example of a case where the number of transmitting antennas Nt=4, in Equation (63), Nt=4, N2=2, Δφ ₀₂ =0, φ ₀₂ =0, A=1, δ2=1, _NC is 3 As a multiple of , the phase rotation φ _nsub2 (m)=2π(nsub2−1)×(m−1)/3 is given to the second chirp signal every transmission period _Tr , so the Doppler shift amount is DOP ₁ = 0 and _DOP2 = 1/(3T _r ). Each lower part of (a) to (d) of FIG. 13 shows an arrangement example of Doppler multiplexed signals when transmitting the second chirp signal.

The arrangement of the Doppler multiplexed signals for the first chirp signal and the second chirp signal shown in (a) of FIG. 13 is the same arrangement. With such an arrangement, the Doppler frequency shift in the Doppler multiplexed signal multiplexed on the first chirp signal and the second chirp signal when the first chirp signal and the second chirp signal are received in the Doppler determination unit 213 described later. Calculations can be made easier.

Note that the arrangement of Doppler multiplexed signals is not limited to the example of FIG. 13(a). The arrangement of Doppler multiplexed signals for the first chirp signal and the second chirp signal may be different.

For example, in FIG. 13(b), by setting Δφ ₀₂ ≠0 in equation (63), the Doppler multiplexed signal for the second chirp signal has a predetermined Doppler frequency component in the arrangement of the Doppler multiplexed signal for the first chirp signal. It may be arranged with an offset.

Further, for example, in FIG. 13(c), two Doppler ranges obtained by dividing the Doppler range of ±1/T _r by 3 (=(N2+δ2)) are shown for each of the first chirp signal and the second chirp signal. Multiple signals are assigned. In (c) of FIG. 13, nsub1=1, 2 in equation (62) for the Doppler multiplexed signal for the first chirp signal, and nsub2 in equation (63) for the Doppler multiplexed signal for the second chirp signal. =2, 3 may be arranged. For example, the allocation of the Doppler multiplexed signals in (N1+.delta.1) (=(N2+.delta.2)) division may be made different for the Doppler multiplexed signals between the first chirp signal and the second chirp signal.

Further, for example, in FIG. 13(d), by setting δ2=2 in equation (63), the Doppler multiplexing interval of the Doppler multiplexed signal for the second chirp signal differs from the Doppler multiplexed interval of the Doppler multiplexed signal for the first chirp signal. Allocations (eg, ΔDOPmin1≠ΔDOPmin2) may be applied.

Further, as an example when the number of transmitting antennas is Nt=5, in Equation (62), N1=2, Δφ ₀₁ =0, φ ₀₁ =0, A=1, δ1=2, and N _C is a multiple of 4, Phase rotation φ _nsub1 (m)=π(nsub1−1)×(m−1)/2 is applied to the first chirp signal every transmission period _Tr , so the Doppler shift amount is DOP ₁ =φ ₁ ( m)/{2π(m−1)T _r }=0, DOP ₂ =φ ₂ (m)/{2π(m−1)T _r }=1/(4T _r ). Each upper part of (a) to (d) of FIG. 14 shows an arrangement example of Doppler multiplexed signals when transmitting the first chirp signal.

Further, as an example of the case where the number of transmitting antennas Nt=5, in Equation (63), Nt=5, N2=3, Δφ ₀₂ =0, φ ₀₂ =0, A=1, δ2=1, N _C is 4 As a multiple of , the _phase rotation φ _nsub2 (m)=π×(m−1)/2 is given to the second chirp signal every transmission period _Tr . ₂ = 1/(4T _r ). Each lower part of (a) to (d) of FIG. 14 shows an arrangement example of Doppler multiplexed signals when transmitting the second chirp signal.

The arrangement of Doppler multiplexed signals for the first chirp signal and the second chirp signal shown in FIG. 14(a) is the same arrangement. With such an arrangement, the Doppler frequency shift in the Doppler multiplexed signal multiplexed on the first chirp signal and the second chirp signal when the first chirp signal and the second chirp signal are received in the Doppler determination unit 213 described later. Calculations can be made easier.

Note that the arrangement of Doppler multiplexed signals is not limited to the example of FIG. 14(a). The arrangement of Doppler multiplexed signals for the first chirp signal and the second chirp signal may be different.

For example, in FIG. 14(b), by setting Δφ ₀₂ ≠0 in equation (63), the Doppler multiplexed signal for the second chirp signal has a predetermined Doppler frequency component in the arrangement of the Doppler multiplexed signal for the first chirp signal. It may be arranged with an offset.

Further, for example, in FIG. 14(c), for each of the first chirp signal and the second _chirp signal, two or Three Doppler multiplexed signals are assigned. In (c) of FIG. 14, for the Doppler multiplexed signal for the first chirp signal, nsub1=1,2 in equation (62), and for the Doppler multiplexed signal for the second chirp signal, nsub2 in equation (63) =3,4,5. For example, the allocation of the Doppler multiplexed signals in (N1+.delta.1) (=(N2+.delta.2)) division may be made different for the Doppler multiplexed signals between the first chirp signal and the second chirp signal.

Further, for example, in FIG. 14(d), by setting δ1=1 in equation (62), the Doppler multiplexing interval for the Doppler multiplexed signal for the second chirp signal differs from the Doppler multiplexing interval for the Doppler multiplexed signal for the first chirp signal. Allocations (eg, ΔDOPmin1≠ΔDOPmin2) may be applied.

[Operation example of Doppler demultiplexing unit 212]
The first Doppler demultiplexing unit 212 performs the interval of the Doppler shift amount DOP _nsub1 between the Doppler shift units 105-1 to 105-N1 included in the first transmission sub-block (for example, between the transmission antennas 106-1 to 106-N1). To separate and receive signals transmitted with (Doppler shift intervals) set not at equal intervals but with at least one Doppler interval being different.

First Doppler demultiplexing section 212 demultiplexes signals Doppler-multiplexed at unequal intervals by the same operation as in Embodiment 1, based on the outputs of Doppler analysis section 210 and CFAR section 211 in the first reception sub-block. . Then _, first Doppler demultiplexing section 212 provides demultiplexing index information ₍ f _{demul_Tx #1} , f demul_Tx _{# 2} , .

Note that the operation of Doppler shift sections 105-1 to 105-N1 included in the first transmission sub-block is the same as that between Doppler shift sections 105-1 to 105-Nt (for example, transmission antennas 106-1 to 106-Nt) in Embodiment 1. -Nt), the operation of the first Doppler demultiplexing unit 212 is similar to the operation in which Nt is replaced with N1 and T _rs is replaced with T _r . In the description of the operation of the Doppler shift unit 105 of form 1, by using the same operation as the operation in which "Nt" is replaced with "N1" and "T _rs " is replaced with " _Tr ", the transmission antenna 106-1 106-N1 can be separated. Therefore, detailed description of the operation of the first Doppler demultiplexer 212 is omitted.

Second Doppler demultiplexing section 212 also performs Doppler shift amount DOP _nsub2 between Doppler shift sections 105-N1+1 to 105-Nt (for example, between transmission antennas 106-N1+1 to 106-Nt) included in the second transmission sub-block. (Doppler shift interval) is not equal, but is set to have at least one different Doppler interval, and the signals are separately received.

Second Doppler demultiplexing section 212 demultiplexes signals Doppler-multiplexed at unequal intervals by the same operation as in Embodiment 1, based on the outputs of Doppler analysis section 210 and CFAR section 211 in the second reception sub-block. . Then _, second Doppler demultiplexing section 212 provides demultiplexing index information ₍ f _{demul_Tx #N1+1} , f _{demul_Tx#N1+2 , .}

Note that the operations of Doppler shift units 105-N1+1 to 105-Nt included in the second transmission sub-block are the same as those between Doppler shift units 105-1 to 105-Nt in Embodiment 1 (for example, transmission antennas 106-1 to 106 -Nt), the operation of the second Doppler demultiplexing unit 212 is similar to the operation in which Nt is replaced with N2 and T _rs is replaced with T _r . In the description of the operation of the Doppler shift unit 105 of form 1, by using the same operation as the operation in which "Nt" is replaced with "N2" and "T _rs " is replaced with " _Tr ", the transmission antenna 106-N1+1 ∼106-Nt Doppler multiplexed signals can be separated. Therefore, detailed description of the operation of the second Doppler demultiplexing unit 212 is omitted.

[Example of operation of Doppler determination unit 213]
In FIG. 11 , the Doppler determining section 213 determines the Doppler frequency corresponding to the Doppler peak based on the outputs of the first Doppler demultiplexing section 212 and the second Doppler demultiplexing section 212 . For example, the Doppler determination unit 213 determines that even if the Doppler frequency _{fd_TargetDoppler} of the target includes a target with a Doppler frequency exceeding the Doppler frequency range −1/(2T _r )≦ _{fd_TargetDoppler} <1/(2T _r ), By determining the target Doppler frequency, the Doppler detection range can be further expanded.

For _example , the Doppler determination unit 213 uses separation index information (f _{demul_Tx #1} , f _{demul_Tx#2} , ~, f _{demul_Tx#N1} ) and separation index information (f _{demul_Tx#N1+1} , f _{demul_Tx#N1+2} , ~, f _{demul_Tx#Nt} ) is used to determine the Doppler frequencies of targets that include Doppler frequencies above the Doppler frequency range -1/(2T _r ) ≤ _{fd_TargetDoppler} < 1/(2T _r ).

The principle of determining the Doppler frequency of the target including the Doppler frequency exceeding the Doppler frequency range −1/(2T _r )≦f _{d_TargetDoppler} <1/(2T _r ) in the Doppler determination unit 213 is the same as in the first embodiment. The fact that the first chirp signal and the second chirp signal, which are radar transmission signals generated by the generation control unit 104 and the radar transmission signal generation unit 101, have different center frequencies is utilized.

In Embodiment 1, Doppler frequency determination is performed based on changes in Doppler frequencies in Doppler multiplexed signals for the same transmit antenna 106 . In contrast, in the present embodiment, Doppler determination section 213 determines the Doppler frequency based on the change in Doppler frequency in Doppler multiplexed signals for different transmitting antennas 106 . When using different transmit antennas 106, the receive phase changes, but the received Doppler frequency does not change. Therefore, as in Embodiment 1, the Doppler determination unit 213 determines the Doppler frequency of the target including the Doppler frequency exceeding the Doppler frequency range −1/(2T _r ) ≦ f _{d_TargetDoppler} <1/(2T _r ). can.

Regarding the operation principle of the Doppler frequency determination process and the operation example of the Doppler determination unit 213, with respect to the description of the operation principle of the Doppler frequency determination process and the operation example of the Doppler determination unit 213 in Embodiment 1 , differ in the following points (1), (2) and (3).
(1) replacing "T _rs " with "T _r ";
(2) Doppler determination section 213 according to Embodiment 1 performs separation index information (f _{demul_Tx #1} (1), f _{demul_Tx#2} (1), ~, f _{demul_Tx#Nt} (1)), the Doppler frequency of the target is within the Doppler frequency range -1/(2T _rs ) ≤ f _{d_TargetDoppler} < 1/(2T _rs ) Calculate the Doppler frequency estimate f _{d_VFT} (1) assuming that On the other hand, in the present embodiment, Doppler determination section 213 uses separation index information (f _{demul_Tx #1} , f _{demul_Tx#2} , ~, f _{demul_Tx#N1} ), the Doppler frequency assuming the target Doppler frequency is within the Doppler frequency range -1/(2T _r ) ≤ f _{d_TargetDoppler} < 1/(2T _r ) a point for calculating the frequency estimate f _{d_VFT} (1), and
(3) Doppler determination section 213 in Embodiment 1 performs separation index information (f _{demul_Tx #1} (2), f _{demul_Tx#2} (2), ~, f _{demul_Tx#Nt} (2)), the Doppler frequency of the target is within the Doppler frequency range -1/(2T _rs ) ≤ f _{d_TargetDoppler} < 1/(2T _rs ) Calculate the Doppler frequency estimated value f _{d_VFT} (2) assuming that On the other hand, in the present embodiment, Doppler determination section 213 uses separation index information (f _{demul_Tx #N1+1} , f _{demul_Tx# N1+2} , ~, f _{demul_Tx#Nt} ), assume that the target Doppler frequency is within the Doppler frequency range -1/(2T _r ) ≤ f _{d_TargetDoppler} < 1/(2T _r ) A point for calculating the Doppler frequency estimate f _{d_VFT} (2) when

In the present embodiment, the operation of the Doppler determination unit 213, which is different from the above three points, is the same as that of the first embodiment, so the explanation of the operation is omitted.

Further, similarly to the Doppler determination unit 213 in Embodiment 1, the center frequency f _c (that satisfies any of the determinable conditions of formulas (10) to (15) obtained by replacing "T _rs " with "T _r ". By setting 1) and f _c (2), the Doppler determination unit 213 determines that when a target with a Doppler frequency exceeding the Doppler frequency range -1/(2T _r ) ≤ f _{d_TargetDoppler} <1/(2T _r ) is included ( For example, even if Doppler folding occurs, the Doppler frequency of the target can be determined. Equations (10) and (13) are equations that include T _rs , but by transforming the equations, T An expression without _rs is obtained. Therefore, the center frequencies f _c (1) and f _c (2) that satisfy the determination condition are the same conditions as in the first embodiment.

Note that equation (18) used to describe the first embodiment is expressed as the following equation (64) by replacing T _rs with _Tr .

Equation (64) expresses the Doppler frequency aliasing component n _{al × {f c (} 2)/f _c (1)}/Tr and the condition that the difference between n _al / _{T r that} is the frequency interval of the number of folding times n _al of the first Doppler analysis unit 210 does not exceed ±1/(2T _r ). For example, when n _al is positive, Δn _al is in the range of ±1/(2T _r ) up to the maximum n _al that satisfies Equation (19), and the Doppler determination unit 213 can unambiguously estimate aliasing. Note that the maximum n _al that satisfies Equation (19) is denoted as “n _almax ”. For example, when n _al is negative, n _al =−n _almax satisfies Equation (19) in the same way.

Here, in Embodiment 1, the first chirp signal or the second chirp signal is transmitted at the T _rs period, and the detection range of the Doppler frequency is, for example, n _almax times the Doppler frequency range for one transmitting antenna. is expanded to On the other hand, in the present embodiment, since the first chirp signal and the second chirp signal are transmitted with the T _r period, the detection range of the Doppler frequency is, for example, It is magnified 2×n _almax times. Therefore, in the present embodiment, compared with the first embodiment, the Doppler frequency detection range can be further expanded under the conditions of the same center frequencies f _c (1) and f _c (2) of the chirp signal.

For example, if f _c (1) and f _c (2) satisfy the condition of n _almax =1, the detection range of the Doppler frequency f _d is ±1/(T _r ), and the Doppler frequency at one transmitting antenna is It is doubled over the frequency range ±1/(2T _r ). Also, for example, if f _c (1) and f _c (2) satisfy the condition of n _almax =2, the detection range of the Doppler frequency f _d is ±2/(T _r ), and one transmission antenna is expanded by a factor of 4 over the Doppler frequency range of ±1/(2T _r ).

The operation example of the Doppler determination unit 213 has been described above.

[Example of Operation of Direction Estimation Unit 214]
In FIG. 11, the direction estimation unit 214 receives information input from the first Doppler demultiplexing unit 212 (for example, the distance index f _{b_cfar} (1) and the separation index information of the Doppler multiplexed signal at the distance index f _{b_cfar} (1) (f _{demul_Tx#1} , f _{demul_Tx #} 2 , _. Based on the separation index information (f _{demul_Tx#N1+1} , f _{demul_Tx#N1+2} , to f _{demul_Tx#Nt} )) of the Doppler multiplexed signal in _{b_cfar} (2), the output of the first Doppler analysis unit 210 and The output of the Doppler analysis unit 210 is extracted and target direction estimation processing is performed.

In this embodiment, between the N1 transmitting antennas 106 included in the first transmitting subblock and the N3 receiving antennas 202 included in the first receiving subblock, N1×N3 MIMO virtual receiving antennas is configured. Similarly, N2×N4 MIMO virtual receive antennas are configured between the N2 transmit antennas 106 included in the second transmit subblock and the N4 receive antennas 202 included in the second receive subblock. be. Direction estimator 214 may perform direction estimation processing using these two sets of virtual receive antennas.

For example, the direction estimation unit 214 obtains the distance index f _{b_cfar} (1) and the separation index information of the Doppler multiplexed signal (f _{demul_Tx#1} , f _{demul_Tx#2} , ~, f _{demul_Tx# N1} ), the output of the first Doppler analysis unit 210 is extracted, and the first virtual receive array correlation vector h ₁ (f _{b_cfar} (1) , f _{demul_Tx#1} , f _{demul_Tx#2} ,~, f _{demul_Tx#N1} ).

Further, the direction estimation unit 214, for example, from the output of the second Doppler demultiplexing unit 212, the distance index f _{b_cfar} (2) and the separation index information of the Doppler multiplexed signal (f _{demul_Tx#N1+1} , f _{demul_Tx#N1+2} , ~, f _{demul_Tx#Nt} ), the output of the second Doppler analysis unit 210 is extracted, and a second virtual receive array correlation vector h ₂ consisting of N2×N4 elements as shown in the following equation (66): Generate (f _{b_cfar} (2), f _{demul_Tx#N1+1} , f _{demul_Tx#N1+2} , ~, f _{demul_Tx#Nt} ).

Since the direction estimator 214 performs direction estimation processing using the outputs of the first and second Doppler demultiplexers 212 with the same distance index, f _{b_cfar} (1) = f _{b_cfar} (2) = f _{b_cfar} .

In equation (65), h _1cal[b] is an array correction value that corrects the phase deviation and amplitude deviation between the transmitting antennas Tx#1 to Tx#N1 and between the receiving antennas Rx#1 to #N3. Integer b=1 to (N3×N1).

Also, in equation (66), h _2cal[b] is an array correction that corrects the phase deviation and amplitude deviation between the transmitting antennas Tx#N1+1 to Tx#Nt and between the receiving antennas Rx#N3+1 to #Na. value. Integer b=1 to (N4×N2).

The direction estimation unit 214, for example, determines the azimuth direction θ _u in the direction estimation evaluation function value _PH (θ _u , f _{b_cfar} , f _{demul_Tx#1} , f _{demul_Tx#2} , ~, f _{demul_Tx#Nt} ) within a predetermined angle range. , the spatial profile is calculated as variable. The direction estimation unit 214 extracts a predetermined number of maximal peaks of the calculated spatial profile in descending order, and outputs the azimuth directions of the maximal peaks as direction-of-arrival estimation values (for example, positioning output). Here, _{fb_cfar} represents a distance index that satisfies _{fb_cfar} (1)= _{fb_cfar} (2).

The direction estimation evaluation function value P _H (θ _u , f _{b_cfar} , f _{demul_Tx#1} , f _{demul_Tx#2} , ~, f _{demul_Tx#Nt} ) has various methods depending on the direction of arrival estimation algorithm. For example, an estimation method using an array antenna disclosed in Non-Patent Document 3 may be used.

For example, the beamformer method can be expressed as in Equation (67) below. In addition to the beamformer method, methods such as Capon and MUSIC are also applicable. Note that in equation (67), the superscript H is the Hermitian transposition operator.

In equation (67), a ₁ (θ _u ) is configured between the N1 transmit antennas 106 included in the first transmit subblock and the N3 receive antennas 202 included in the first receive subblock. , N1×N3 MIMO virtual reception antenna directional vectors (column vectors with N1×N3 elements), which form N1×N3 MIMO virtual reception antennas when reflected waves arrive from _{the u} direction Represents the phase or complex amplitude response at each virtual receive antenna.

Similarly, in equation (67), a ₂ (θ _u ) is Represents the directional vectors (column vectors with N2×N4 elements) of the configured N2×N4 MIMO virtual reception antennas, and represents the N2×N4 MIMO virtual reception antennas when reflected waves arrive from the θ _u direction. represents the phase or complex amplitude response at each virtual receive antenna that constitutes .

Note that the directional vector a _q (θ _u ) is _the phase response or complex Amplitude response may be used. Alternatively, the direction vector a(θ _u ) of the virtual receiving array for the incoming wave in the azimuth direction θ at the average center frequency of the center frequencies f _c (1) and f _c (2) may be used in common.

Also, the azimuth direction θ _u is a vector obtained by changing the azimuth range in which direction-of-arrival estimation is performed at a predetermined azimuth interval β ₁ . For example, θ _u is set as follows.
_θu = θmin + uβ ₁ , integer u = 0 to NU
NU=floor[(θmax−θmin)/ _β1 ]+1
where floor(x) is a function that returns the largest integer value that does not exceed the real number x.

In the above example, the direction estimator 214 calculates the azimuth direction as the direction-of-arrival estimation value. However, the present invention is not limited to this. Direction-of-arrival estimation in azimuth and elevation directions is also possible by using MIMO antennas. For example, the direction estimator 214 may calculate the azimuth direction and the elevation angle direction as the direction-of-arrival estimation values and use them as the positioning output.

Through the above operation, the direction estimation unit 214 uses the distance index f _{b_cfar} and the direction-of-arrival estimated value in the separation index information (f _{demul_Tx#1} , f _{demul_Tx#2} , to, f _{demul_Tx#Nt} ) of the Doppler multiplexed signal as the positioning output. can be output. Moreover, the direction estimation unit 214 may further output the distance index _{fb_cfar} and separation index information (f _{demul_Tx#1} , f _{demul_Tx#2} , to f _{demul_Tx#Nt} ) of the Doppler multiplexed signal as the positioning output. The direction estimator 214 may output the positioning output (or the positioning result) to, for example, a vehicle control device for an in-vehicle radar or an infrastructure control device for an infrastructure radar (not shown).

Further, the direction estimation unit 214, for example, the Doppler frequency information f _{d_VFT(1)} +n _alest /T _s determined by the Doppler determination unit 213 and f _c (2)/f _c (1)(f _{d_VFT(1 )} +n _alest /T _s ) or both may be output.

Further, the distance index f _{b_cfar} may be converted into distance information using Equation (1) and output.

Further, the Doppler frequency information determined by the Doppler determination unit 213 may be converted to relative velocity information and output. To convert the Doppler frequency information f _{d_VFT(1)} +n _alest /T _s based on the center frequency f _c (1) determined by the Doppler determining unit 213 to the relative velocity v _d , use the following equation (68): can be converted.

Similarly, the Doppler frequency information f _c (2)/f _c (1) (f _{d_VFT(1)} +n _alest /T _r ) by the center frequency f _c (2) determined by the Doppler determination unit 213 is used as the relative velocity When converted to v _d , the following equation (69) gives the same value as equation (68), so the relative velocity component information is output as a common value (or unified value) for different center frequencies. may be

As described above, in the present embodiment, the radar device 10a includes a plurality of radar transmission signal generators 101, and for example, the first center frequency and the first 2 center frequencies, the transmission signal is transmitted from the transmission antenna 106 for each predetermined transmission period. As a result, the radar device 10a can determine the number of loopbacks in the Doppler determination section 213 based on the deviation of the Doppler frequencies detected by the Doppler analysis section 210 and the Doppler demultiplexing section 212 according to the difference in center frequency. Therefore, the radar device 10a can expand the Doppler frequency range (or the maximum value of the relative velocity) in which the Doppler multiplexed signal can be separated, for example, according to the number of folds that can be determined.

In addition, in the present embodiment, the first chirp signal and the second chirp signal are transmitted at the same time every transmission cycle T _r , so Doppler multiplexed signals can be multiplexed within the Doppler frequency range ±1/2 T _r . becomes. For example, compared with the case of Doppler multiplex transmission with T _rs =2T _r as in Embodiment 1, in this embodiment, Doppler multiplex transmission is performed with twice the Doppler frequency range (or the maximum value of the relative velocity). Signals can be multiplexed.

Also, for example, by setting the number of transmission antennas 106 included in the first and second transmission sub-blocks to be the same or substantially the same, the Doppler multiplexing interval when Doppler-multiplexing is performed using the first chirp signal and the second chirp signal is can obtain the effect of enlarging about four times as compared with the first embodiment.

When the Doppler multiplexing interval is close when Doppler multiplexing is performed, interference between Doppler multiplexed signals is likely to occur in the case of a target whose Doppler component spreads, and the accuracy of direction estimation deteriorates. detection accuracy tends to deteriorate. Compared with Embodiment 1, the present embodiment can expand the Doppler multiplexing interval during Doppler multiplexing. Degradation of target detection accuracy can be suppressed. In addition, in this embodiment, compared to Embodiment 1, the Doppler multiplexing interval for Doppler multiplexing can be expanded. can be reduced, and deterioration of direction estimation accuracy and deterioration of target detection accuracy can be suppressed. Therefore, in this embodiment, Doppler multiplexing transmission using more transmitting antennas 106 is possible than in the first embodiment.

As described above, according to this embodiment, it is possible to expand the Doppler frequency range (or the maximum value of the relative velocity) in which ambiguity does not occur. Thereby, the radar device 10a can accurately detect a target (for example, the direction of arrival) in a wider Doppler frequency range.

In addition, in the present embodiment, the Doppler frequency range in which the Doppler multiplexed signal can be separated is expanded by setting the center frequency of the chirp signal. may be omitted. Therefore, according to the present embodiment, complication of the hardware configuration of the radar device 10a can be suppressed, and an increase in power consumption or heat generation in the radar device 10a can be suppressed. Further, in this embodiment, the Doppler frequency range in which the Doppler multiplexed signal can be separated is expanded by setting the center frequency of the chirp signal, so the application of the method of shortening the transmission period _Tr may be omitted. Therefore, according to the present embodiment, it is possible to suppress the reduction of the detectable distance range or the deterioration of the distance resolution in the radar device 10a.

In the present embodiment, the radar device 10a includes two radar transmission signal generators 101, and for example, a first center frequency and a second center frequency that satisfy any of equations (10) to (15). is used to transmit a transmission signal from the transmission antenna 106 at each predetermined transmission cycle, but the present invention is not limited to this. The radar device 10a may be configured to include more (three or more) radar transmission signal generators 101, for example.

For example, the radar device 10a includes three radar transmission signal generators 101, and has a first center frequency fc(1) and a second center frequency fc(2) that satisfy any of equations (10) to (15). and further, using the second center frequency fc(2) and the third center frequency fc(3) that satisfy any one of the formulas (10) to (15), the transmitting antenna 106 You may transmit a transmission signal from. Note that fc(1)>fc(2)>fc(3) or fc(1)<fc(2)<fc(3) may be satisfied. In this case, three reception sub-blocks may be provided in radar reception section 200a, and outputs from three radar transmission signal generation sections 101 may be input to mixer section 204 of each reception sub-block. Further, in radar receiving section 200a, CFAR section 211 and Doppler demultiplexing section 212 are provided for each reception subblock, and each of them may perform the same operation as in the present embodiment. As a result, demultiplexed received signals for the three chirp signals are obtained, and the Doppler determination unit 213 performs Doppler determination based on these output signals, thereby expanding the Doppler frequency detection range.

Further, for example, the radar device 10a may be configured to include three or more radar transmission signal generators 101, and the number of transmission antennas included in each transmission sub-block may be the same or substantially the same. This provides the effect of further expanding the Doppler multiplexing interval when Doppler multiplexing is performed using a plurality of chirp signals. Therefore, since the Doppler multiplexing interval can be expanded when Doppler multiplexing is performed, the occurrence of interference between Doppler multiplexed signals can be reduced, and deterioration of direction estimation accuracy and target detection accuracy due to interference can be suppressed. In addition, since the Doppler multiplexing interval during Doppler multiplexing can be expanded, interference between Doppler multiplexed signals can be reduced even if more transmitting antennas 106 are used for Doppler multiplexing than in the first embodiment. , deterioration of direction estimation accuracy and deterioration of target detection accuracy can be suppressed.

Also, in the present embodiment, the modulation parameters for the first chirp signal and the second chirp signal have a common parameter other than the center frequency, but the present invention is not limited to this. An embodiment of the present disclosure may be applied to, for example, chirp signals having the same range resolution and the same frequency sweep bandwidth B _w (q).

For example, as shown in FIG. 15, it is set by modulation parameters such that B _w (1)=B _w (2), T _sw (1)≠T _sw (2), and D _m (1)≠D _m (2). A first chirp signal and a second chirp signal may be used. In this case, although the frequency sweep times T _SW of the first chirp signal and the second chirp signal are different, the frequency sweep bandwidth B _w is the same, and the range resolution ΔR (=C ₀ /2B _w ) is the same. The device 10a can obtain the same effect by performing the operation according to the embodiment of the present disclosure described above.

Further, for example, as shown in FIG. 15, by setting T _sw (1)≠T _sw (2), the beat signal output from each reception radio section 203 is converted to the A/D conversion section of each signal processing section 206 . When performing discrete sampling at 207, the number of discrete sampling data obtained in a predetermined time range (range gate) T _sw (1)≠T _sw (2) is different. Therefore, the beat frequency analysis unit 208 performs the following operation instead of performing FFT processing on N _data pieces of discrete sampling data obtained in a predetermined time range (range gate) T _sw in each transmission cycle _Tr , for example. good too.

For example, the beat frequency analysis unit 208 in the first reception sub-block performs N _data (1) discrete samplings obtained in a predetermined time range (range gate) T _sw (1) in the period in which the first chirp signal is transmitted. The data may be FFT processed. In addition, the beat frequency analysis unit 208 in the second reception sub-block performs N _data (2) discrete samplings obtained in a predetermined time range (range gate) T _sw (2) in the cycle in which the second chirp signal is transmitted. The data may be FFT processed. Then, for example, the beat frequency analysis unit 208 sets the smaller one of N _data (1) and N _data (2) to N _data , and performs subsequent processing (CFAR unit 211, Doppler demultiplexing unit 212, Doppler demultiplexing unit 212, processing of the determination unit 213 and the direction estimation unit 214) may be performed.

Further, the radar device 10a of the present embodiment includes a plurality of radar transmission signal generators 101, and, for example, a first center frequency and a second center frequency that satisfy any of equations (10) to (15). is used to transmit a transmission signal from the transmission antenna 106 at each predetermined transmission cycle. Thereby, the radar device 10a can determine the number of times of folding back based on the deviation of the Doppler frequency in the Doppler analysis according to the difference in the center frequency. Therefore, the radar device 10a can expand the Doppler frequency range (or the maximum value of the relative velocity) in which the Doppler multiplexed signal can be separated, for example, according to the number of folds that can be determined. Moreover, compared with the first embodiment, the Doppler frequency range (or the maximum value of the relative velocity) capable of separating Doppler multiplexed signals can be doubled.

Also, in the present embodiment, the Doppler detection range in Doppler analysis section 210 is twice as large as that in the first embodiment. Also, in the present embodiment, the number of transmitting antennas N1 or N2 used for Doppler multiplexing is smaller than the number Nt of transmitting antennas used for Doppler multiplexing in the first embodiment. Therefore, in the present embodiment, the Doppler multiplexing interval can be at least doubled compared to the first embodiment. For example, when the Doppler multiplexing intervals are close, interference between Doppler multiplexed signals is likely to occur in the case of a target whose Doppler component has a spread. On the other hand, in this embodiment, it is possible to perform multiplex transmission using more transmitting antennas 106 .

(Modification 1 of Embodiment 3)
In this embodiment, the Doppler shift units 105-1 to 105-N1 and the Doppler shift units 105-N1+1 to 105-Nt included in the first and second transmission sub-blocks are the first and second chirps. The operation when the intervals (Doppler shift intervals) between the respective Doppler shift amounts DOP _nsub1 and DOP _nsub2 for the signals are set not at equal intervals but at unequal intervals with at least one Doppler interval different has been described.

However, the present invention is not limited to this, and at least one of the Doppler intervals set by Doppler shift section 105 in the first or second transmission sub-block is not equal, but is set to a different uneven interval, and the other is set to be equal. may

As an example, the Doppler shift units 105-1 to 105-N1 included in the first transmission sub-block apply Doppler shift amounts DOP A case will be described in which a phase rotation φ _nsub1 (m) such as Equation (62), which becomes _nsub1 , is given and unequal-interval Doppler multiplexing is performed with the Doppler multiplexing number N1. In this case, the Doppler shift units 105-N1+1 to 105-Nt included in the second transmission sub-block provide different amounts of Doppler shift between the Doppler shift units 105 for the input m-th second chirp signal. A phase rotation φ _nsub2 (m) such as the following equation (70), which becomes DOP _nsub2 , may be given, and equal-interval Doppler multiplexing may be performed with the Doppler multiplexing number N2.

Alternatively, as another example, the Doppler shift sections 105-1 to 105-N1 included in the first transmission sub-block each doppler shift sections 105 for the input m-th first chirp signal. A case will be described in which a phase rotation φ _nsub1 (m) such as the following equation (71) that results in a different Doppler shift amount DOP _nsub1 is given, and equal-interval Doppler multiplexing is performed with the Doppler multiplexing number N1. In this case, the Doppler shift units 105-N1+1 to 105-Nt included in the second transmission sub-block provide different amounts of Doppler shift between the Doppler shift units 105 for the input m-th second chirp signal. A phase rotation φ _nsub2 (m) such as Equation (63), which becomes DOP _nsub2 , may be given, and unequal interval Doppler multiplexing may be performed with the Doppler multiplexing number N2.

Here, in equations (70) and (71), A is a coefficient that gives a positive or negative polarity of 1 or -1. The terms round(N _C /N1) and round(N _C /N2) are introduced for the purpose of setting the phase rotation amount to an integral multiple of the Doppler frequency interval in the Doppler analysis unit 210, but are limited to this. 2π/N1 may be used instead of the term (2π/N _C )×round(N _C /N1) in equation (71). Similarly, 2π/N2 may be used instead of the term (2π/N _C )×round(N _C /N2) in equation (70). Also, φ ₀₁ and φ ₀₂ are initial phases, and may be equal or different. The Doppler frequencies match whether φ ₀₁ and φ ₀₂ are equal or different. Δφ ₀₁ and Δφ ₀₂ are reference Doppler shift phases, which may be equal or different. The Doppler frequencies match whether Δφ ₀₁ and Δφ ₀₂ are equal or different.

As an example when the number of transmitting antennas Nt = 4, in Equation (62), N1 = 2, Δφ ₀₁ = 0, φ ₀₁ = 0, A = 1, δ1 = 1, N _C is a multiple of 6, and the phase rotation is φ _nsub1 (m)=2π(nsub1−1)×(m−1)/3 is added to the first chirp signal every transmission period _Tr , so the Doppler shift amount is DOP ₁ =φ ₁ (m) /{2π(m−1)T _r }=0, DOP ₂ =φ ₂ (m)/{2π(m−1)T _r }=1/(3T _r ). The upper part of FIG. 16(a) shows an arrangement example of Doppler multiplexed signals when transmitting the first chirp signal.

Further, as an example when the number of transmitting antennas Nt=4, in Equation (70), Nt=4, N2=2, Δφ ₀₂ =0, φ ₀₂ =0, A=1, N _C being a multiple of 6, Since the phase rotation φ _nsub2 (m)=2π(nsub2−1)×(m−1)/2 is applied to the second chirp signal every transmission period _Tr , the Doppler shift amount is DOP ₁ =0, _DOP2 = 1/ _Tr . The lower part of FIG. 16(a) shows an arrangement example of Doppler multiplexed signals when transmitting the second chirp signal.

Further, as an example when the number of transmitting antennas Nt=5, in equation (71), if N1=3, Δφ ₀₁ =0, φ ₀₁ =0, A=1, and N _C is a multiple of 3, then the phase rotation φ Since _nsub1 (m)=2π(nsub1−1)×(m−1)/3 is added to the first chirp signal every transmission period _Tr , the Doppler shift amount is DOP ₁ =φ ₁ (m)/{ 2π(m−1) _Tr }=0, _DOP2 = _φ2 (m)/{2π(m−1) _Tr }=1/( _3Tr ), DOP3= _{φ3 (} m)/{2π (m−1)T _r }=2/(3T _r )=−1/(3T _r ). The upper part of FIG. 16(b) shows an arrangement example of Doppler multiplexed signals when transmitting the first chirp signal.

Further, as an example of a case where the number of transmitting antennas is Nt=5, in Equation (63), Nt=5, N2=2, Δφ ₀₂ =0, φ ₀₂ =0, A=1, δ2=1, _NC is 3 , the phase rotation φ _nsub2 (m)=π×(m−1)/2 is applied to the second chirp signal every transmission period _Tr , so the Doppler shift amount is DOP ₁ =0, _DOP2 = 1/(3T _r ). The lower part of FIG. 16(b) shows an arrangement example of Doppler multiplexed signals when transmitting the second chirp signal.

Thus, when the Doppler intervals between Doppler multiplexed signals set in Doppler shifter 105 in the first or second transmission sub-block are equal intervals, Doppler demultiplexer 212 in radar receiver 200a performs ±1/ In the Doppler frequency range of T _r , estimation of the Doppler frequency becomes difficult, so output of separation index information of the Doppler multiplexed signal becomes difficult. Radar receiver 200a, for example, performs Doppler shifts for received signals corresponding to signals of transmission sub-blocks in which the Doppler intervals between Doppler multiplexed signals set in Doppler shifter 105 in the first or second transmission sub-block are unequal. Demultiplexing processing is performed using the output of the demultiplexing unit 212 .

FIG. 17 shows the radar receiver in the case where the Doppler shift unit 105 in the first transmission sub-block performs unequal Doppler multiplexing and the Doppler shift unit 105 in the second transmission sub-block performs equidistant Doppler multiplexing in the radar device 10a. 200a configuration example.

The first reception sub-block performs reception processing of the reflected wave of the first transmission sub-block. The radar receiver 200a shown in FIG. 17 differs from the radar receiver 200a shown in FIG. 11 in that the output from the first Doppler demultiplexer 212 is input to the second Doppler demultiplexer 212, for example. An operation example of the Doppler demultiplexer 212 in the radar receiver 200a shown in FIG. 17, which is different from the radar receiver 200a shown in FIG. 11, will be described below.

The operation of demultiplexing the Doppler multiplexed signal in the first Doppler demultiplexer 212 is the same as the operation described above (the operation in FIG. 11), but the first Doppler demultiplexer 212 uses distance index f _{b_cfar} (1) information and , separation index information (f _{demul_Tx#1} , f _{demul_Tx#2} , to f _{demul_Tx#N1} ) of N1 Doppler multiplexed signals multiplexed in the first transmission subblock at distance index f b_cfar ( ₁ ), Output to the 2-Doppler demultiplexing unit 212 .

The second Doppler demultiplexing unit 212, for example, demultiplexes index information (f _{demul_Tx #1} , f _{demul_Tx#2} , . _{f demul_Tx#Nt} ) _, the _estimated Doppler frequency f _{d_VFT} ( 1) is calculated. For example, the second Doppler demultiplexing unit 212 may calculate the Doppler frequency estimation value f _{d_VFT} (1) from which a component of a known predetermined Doppler shift amount given to each transmitting antenna 106 in the radar transmitting unit 100a is removed. .

_{Then, second Doppler demultiplexing section 212 generates a peak (distance index f b_cfar (} 2 ) and the Doppler frequency index f _{s_cfar} (2)) to separate the Doppler multiplexed signals. For example, the second Doppler demultiplexing unit 212 calculates a plurality of Doppler frequency indices f _{s_cfar} (2) ∈ _{ fd _#N1+1 , fd _{#N1+2 .} . . , fd _#Nt }, using the Doppler frequency estimation value f _{d_VFT} (1), which of the transmitted signals transmitted from the transmitting antennas Tx#N1+1 to Tx#Nt is the reflected wave signal corresponding to judge.

For example, the Doppler shift amounts that the Doppler shift section 105 in the second transmission sub-block gives to the second chirp signals output from the transmission antennas Tx#N1+1 to Tx#Nt are known. Therefore, the second Doppler demultiplexing unit 212 calculates the reception Doppler frequencies for the transmission antennas Tx#N1+1 to Tx#Nt assuming that the Doppler frequency of the target is the Doppler frequency estimate f _{d_VFT} (1). It is possible.

Reception Doppler frequencies for the transmission antennas Tx#N1+1 to Tx#Nt in this case are expressed as {fdRef _#N1+1 , fdRef _#N1+2 , to fdRef _#Nt }.

The second Doppler demultiplexer 212 can generate such signals for each transmit antenna 106 . For these Doppler frequencies, the second Doppler demultiplexing unit 212, for example, selects a Doppler frequency index f _{s_cfar} (2) from the second CFAR unit 211 that has the smallest difference and is smaller than ±ΔDOP _min2 /2. The frequencies are determined to be the receive Doppler frequencies for the transmit antennas Tx#N1+1 through Tx#Nt.

Then, the second Doppler demultiplexing unit 212 separates and outputs reflected wave signals for each of the determined transmitting antennas Tx#N+1 to Tx#Nt. For example, the second Doppler demultiplexing unit 212 _uses distance index f _{b_cfar} (2) information and demultiplexing index information (f _{demul_Tx#N1+1} , f _{demul_Tx #N1+} 2 , .

As a premise that such operation of the second Doppler demultiplexing unit 212 is possible, the difference in the Doppler frequency of the target caused by the difference between the center frequency of the first chirp signal and the center frequency of the second chirp signal is Assume that the relative velocity of the target is within this range under the condition that it is within ±ΔDOP _min2 /2.

In radar apparatus 10a, Doppler shift section 105 in the second transmission sub-block may perform unequal interval Doppler multiplexing, and Doppler shift section 105 in the first transmission sub-block may perform equal interval Doppler multiplexing. In this case, as in the example of FIG. Doppler demultiplexing is possible.

In this way, the Doppler shifter 105 in at least one of the first or second transmission sub-blocks is set to perform unequal Doppler multiplexing, and the Doppler shifter 105 in the remaining transmission sub-blocks is set to perform equidistant Doppler multiplexing. may be As a result, the radar apparatus 10a can obtain the effect of further expanding the Doppler multiplexing interval when Doppler multiplexing is performed using the first chirp signal and the second chirp signal. By expanding the Doppler multiplexing interval during Doppler multiplexing, it is possible to reduce the occurrence of interference between Doppler multiplexed signals, thereby suppressing deterioration in direction estimation accuracy and target detection accuracy. In addition, in Doppler shift section 105 in the following embodiments, the setting of unequal interval Doppler multiplexing and equal interval Doppler multiplexing can be similarly applied, and similar effects can be obtained.

(Modification 2 of Embodiment 3)
Also, the configuration of the radar device 10a shown in FIG. 11 may be realized by combining a plurality of transmitting/receiving chips, as shown in FIG. 18, for example. In the example of FIG. 18, the radar device 10a is composed of a transmitting/receiving chip #1 and a transmitting/receiving chip #2.

Transmission/reception chip #q includes radar transmission signal generator 101-q, q-th transmission sub-block, q-th reception sub-block, q-th CFAR unit 211 (or CFAR unit 211-q), and q-th Doppler demultiplexing unit 212. (or Doppler demultiplexing unit 212-q). where q=1 or 2.

At least one of the Doppler determining unit 213 and the direction estimating unit 214 may be implemented in another signal processing chip or ECU, or may be incorporated in any of the transmitting/receiving chips.

18 differs from FIG. 11 in that a synchronization signal generator 215 is provided, and a synchronization signal (for example, a reference signal) output from the synchronization signal generator 215 is transmitted to the radar of the radar transmitter 100a of each transmission/reception chip. It is output to the transmission signal generating section 101 . As a result, the frequency difference between the first chirp signal output from the transmission sub-block of the transmission/reception chip #1 and the second chirp signal output from the transmission sub-block of the transmission/reception chip #2 is an allowable predetermined error. It is possible to output a chirp signal so as to be within. Even with the configuration shown in FIG. 18, the same effect as in the third embodiment can be obtained, and by combining general-purpose transmission/reception chips, cost can be reduced.

(Embodiment 4)
In Embodiment 3, a MIMO antenna configuration with the number of transmitting antennas Nt and the number of receiving antennas Na is used. The operation of performing direction estimation processing using the above has been described. where N1+N2=Nt and N3+N4=Na. In this case, the number of antennas that can be used in direction estimation section 214 is less than Nt×Na.

In the present embodiment, as in Embodiment 3, when radar transmission signals with different frequencies are simultaneously transmitted in each transmission period, the number of MIMO virtual reception antennas that can be used in direction estimation section 214 as in Embodiment 1 is is set to Nt×Na.

For example, FIG. 19 shows a configuration example including two radar transmission signal generation sections 101 in the radar transmission section 100b of the radar device 10b. As shown in FIG. 19, a radar apparatus 10b has radar transmission signals with different center frequencies generated in a plurality of radar transmission signal generation sections 101, similarly to the configuration of the radar apparatus 10a shown in FIG. (for example, a chirp signal) are simultaneously transmitted from a plurality of transmit antennas 106 every transmission period T _r .

On the other hand, the radar receiver 200b shown in FIG. 11 different. In addition, the radar receiver 200b shown in FIG. 19 is an output switching unit that switches the output destination of the beat frequency analysis unit 208 to one of the two Doppler analysis units 210 in conjunction with the switching operation of the switching unit 216. 217.

Hereinafter, regarding the operation of the present embodiment, an operation example different from that of the third embodiment will be mainly described.

FIG. 19 shows, as an example, a configuration including two radar transmission signal generation sections 101 in the radar transmission section 100b of the radar device 10b. In the following, the two radar transmission signal generators 101 are respectively referred to as "first radar transmission signal generator 101 (or radar transmission signal generator 101-1)" and "second radar transmission signal generator 101 ( Alternatively, it is called the radar transmission signal generator 101-2).

In FIG. 19, the configuration of each radar transmission signal generator 101 may be the same as in the first embodiment. Each radar transmission signal generation unit 101 generates a radar transmission signal based on control from the signal generation control unit 104, for example.

The signal generation control section 104 controls the first and second radar transmission signal generation sections 101 (for example, the modulation signal generation section 102 and the VCO 103) to generate radar transmission signals. For example, the signal generation control unit 104 sets parameters (for example, modulation parameters) related to chirp signals so that chirp signals with different center frequencies are transmitted from each of the first and second radar transmission signal generation units 101. good. Hereinafter, the chirp signal generated by the first radar transmission signal generator 101 will be called "first chirp signal", and the chirp signal generated by the second radar transmission signal generator 101 will be called "second chirp signal".

Signal generation control section 104 may set (or select) center frequency f _c (q) that satisfies a predetermined condition, for example, as in the first embodiment. In the following, as an example, of the modulation parameters set for the first chirp signal and the second chirp signal, the center frequencies f _c (q) are different from each other, and the modulation parameters other than the center frequencies are the same ( or common) will be described. However, it is not limited to this, and for the application of an embodiment of the present disclosure, for example, the first chirp signal and the second chirp signal need only have the same resolution in the distance axis, so the frequency sweep bandwidth B _w (q ) are set to have the same relationship. where q=1,2.

Further, for example, as in Embodiment 3, the signal generation control unit 104 simultaneously transmits two chirp signals having different center frequencies f _c (q) 2Nc times, respectively, as shown in FIG. The modulated signal generator 102 and the VCO 103 may be controlled to (or output).

In one embodiment of the present disclosure, the transmission cycle T _r may be set to, for example, several hundred microseconds or less, and the transmission time interval of the radar transmission signal may be set relatively short. As a result, for example, even if the center frequencies of the first chirp signal and the second chirp signal are different, the frequency of the beat signal of the received reflected wave (for example, the beat frequency index) does not change. It is detectable as a change in Doppler frequency.

The first chirp signal output from the first radar transmission signal generator 101 (eg, VCO 103) is generated by, for example, N1 Doppler shifters 105 (eg, Doppler shifter 105- 1 to 105-N1). Further, the first chirp signal output from the first radar transmission signal generating section 101 is divided into the first switching section 216 (or referred to as switching section 216-1) and the second switching section 216 (or switching section 216 -2).

On the other hand, the second chirp signal output from the second radar transmission signal generator 101 (for example, VCO 103) is generated by N2 Doppler shifters 105 (for example, Doppler shifter 105) out of Nt Doppler shifters 105, for example. 105-N1+1 to 105-Nt). Also, the second chirp signal output from the second radar transmission signal generation section 101 is input to the first and second switching sections 216, respectively.

Here, N1+N2=Nt.

Then, the output signals of N1 Doppler shift units 105 to which the first chirp signal is input are amplified to a predetermined transmission power and radiated into space from each transmission antenna 106 (for example, Tx#1 to Tx#N1). . Further, the output signals of N2 Doppler shift units 105 to which the second chirp signals are input are amplified to a predetermined transmission power and radiated into space from each transmission antenna 106 (for example, Tx#N1+1 to Tx#Nt). be done. As a result, the first chirp signal and the second chirp signal are simultaneously transmitted every transmission period _Tr .

For example, the first and second switching units 216 switch the first chirp signal input from the first radar transmission signal generation unit 101 and the second chirp signal input from the second radar transmission signal generation unit 101 to the radar transmission signal. , and output to one of the mixer units 204 of the Na antenna system processing units 201 of the radar receiving unit 200b.

For example, in the odd-numbered transmission period, the first and second switching units 216 switch the first chirp signal to N3 antenna system processing units 201 ( For example, they may be input to the mixer units 204 of the antenna system processing units 201-1 to 201-N3). Further, for example, in the odd-numbered transmission period, the first and second switching units 216 switch the second chirp signal to N4 antenna system processing units among the Na antenna system processing units 201 of the radar receiving unit 200b. 201 (eg, antenna system processing units 201-N3+1 to 201-Na).

Here, N3+N4=Na.

Further, for example, in even-numbered transmission cycles, the first and second switching units 216 switch the first chirp signal to N4 antenna system processing units among the Na antenna system processing units 201 of the radar receiving unit 200b. 201 (eg, antenna system processing units 201-N3+1 to 201-Na). Further, for example, in even-numbered transmission cycles, the second chirp signal is transmitted to N3 antenna system processing units 201 (for example, antenna system processing units 201- 1 to 201-N3), respectively.

Note that the output destinations of the first and second chirp signals in the odd-numbered and even-numbered transmission periods (the switching destinations of the first and second switching units 216) may be reversed. In this way, the output destinations of the first chirp signal and the second chirp signal (receiving sub-blocks to be described later) may be alternately switched for each transmission cycle.

In the following, N1 Doppler shift units 105 to which the first chirp signal is input, and each transmitting antenna 106 (for example, Tx#1 to Tx#N1) transmitting the output signals of these N1 Doppler shift units 105 are , is called the "first transmission sub-block". Also, N2 Doppler shift units 105 to which the second chirp signal is input, and each transmitting antenna 106 (for example, Tx#N1+1 to Tx#Nt) for transmitting the output signals of these N2 Doppler shift units 105 is called a "second transmission sub-block". where N1+N2=Nt. Note that N1 and N2 are each 2 or more, and Nt is 4 or more.

For example, the Doppler shift unit 105 included in the first transmission sub-block gives phase rotation φ _nsub1 to the first chirp signal in order to give the Doppler shift amount DOP _nsub1 for each chirp signal transmission cycle T _r . and outputs the Doppler-shifted signal to the transmitting antenna 106 (for example, Tx#1 to Tx#N1). Here, nsub1=an integer from 1 to N1. Also, the Doppler shifter 105 included in the second transmission sub-block imparts a phase rotation φ _nsub2 to the second chirp signal in order to impart a Doppler shift amount DOP _nsub2 for each chirp signal transmission period _Tr . and outputs the Doppler-shifted signal to the transmitting antenna 106 (for example, Tx#N1+1 to Tx#Nt). Here, nsub2=an integer from 1 to N2.

The Doppler shift amount DOP _nsub1 (or phase rotation φ _nsub1 ) and the Doppler shift amount DOP _nsub2 (or phase rotation φ _nsub2 ) in the Doppler shift unit 105 included in the first and second transmission sub-blocks are given. An example of the method differs from the third embodiment, and an example will be described later.

Also, when Nt is an even number, the number of transmission antennas 106 included in the first and second transmission sub-blocks may be the same, for example, by setting N1=N2. Also, when Nt is an odd number, for example, by setting N1=(Nt+1)/2 or N1=(Nt-1)/2, the transmission antennas 106 included in the first and second transmission sub-blocks may be approximately equal to one transmit antenna difference. Thus, the number of transmit antennas 106 included in the first sub-block (eg, the transmit antennas 106 transmitting the first chirp signal) and the number of transmit antennas 106 included in each second transmit sub-block (eg, the second chirp signal) The number of transmit antennas 106) for transmitting signals may be set to be the same or differ by one. By setting the number of transmitting antennas 106 included in the first and second sub-blocks to be the same or substantially the same, the radar apparatus 10b can perform Doppler multiplexing using the first chirp signal and the second chirp signal. It is possible to obtain the effect of further enlarging the interval (for example, the effect of enlarging it by about two times) as compared with the first embodiment.

For example, if the Doppler multiplexing intervals are close when Doppler multiplexing is performed, interference between Doppler multiplexed signals is likely to occur in the case of a target whose Doppler component is spread out, and the accuracy of direction estimation deteriorates. detection accuracy tends to deteriorate. In this embodiment, since the Doppler multiplexing interval can be expanded when Doppler multiplexing is performed, it is possible to reduce the occurrence of such interference between Doppler multiplexed signals, and it is possible to suppress the deterioration of the direction estimation accuracy and the deterioration of the target detection accuracy. .

In addition, in this embodiment, since the Doppler multiplexing interval can be expanded when Doppler multiplexing is performed, even if more transmitting antennas 106 are used for Doppler multiplexing, the occurrence of interference between Doppler multiplexed signals can be reduced and direction estimation can be performed. It is possible to suppress deterioration of accuracy and deterioration of target detection accuracy. Therefore, in this embodiment, more transmitting antennas 106 can be used for Doppler multiplexing than in the first embodiment. In this way, when Doppler multiplexing is performed using more transmitting antennas 106, this embodiment is more suitable than the first embodiment.

[Configuration Example of Radar Receiver 200b]
In FIG. 19, the radar receiving section 200b comprises, for example, Na receiving antennas 202 (eg, Rx#1 to Rx#Na) to form an array antenna. Further, the radar receiving unit 200b includes, for example, Na antenna system processing units 201-1 to 201-Na, a CFAR unit 211, a Doppler demultiplexing unit 212, a Doppler determination unit 213, a direction estimation unit 214, have

Each receiving antenna 202 receives a reflected wave signal that is a radar transmission signal (for example, a first chirp signal and a second chirp signal) reflected by a target, and transmits the received reflected wave signal to the corresponding antenna system. It is output to the processing unit 201 as a received signal.

Each antenna system processing section 201 has a receiving radio section 203 and a signal processing section 206 .

Receiving radio section 203 has mixer section 204 and LPF 205 . In reception radio section 203, mixer section 204 mixes the received reflected wave signal (reception signal) with a chirp signal, which is a transmission signal.

Here, for example, in the odd-numbered transmission period, the first chirp signal output from the first or second switching unit 216 is the N3 antenna system processing units 201 out of the Na antenna system processing units 201. They are input to mixer section 204 in reception radio section 203 . In the antenna system processing units 201-1 to 201-N3, by passing the output of the mixer unit 204 through the LPF 205, the output of the mixer unit 204 corresponding to the reflected wave of the second chirp signal is out of the passband of the LPF 205. Since the frequency is high, the LPF 205 easily outputs a beat signal having a frequency corresponding to the delay time of the reflected wave signal of the first chirp signal.

Further, for example, in the odd-numbered transmission period, the second chirp signal output from the first or second switching unit 216 is received by N4 antenna system processing units 201 out of Na antenna system processing units 201. They are input to mixer section 204 in radio section 203 . In the antenna system processing units 201-N3+1 to 201-Na, by passing the output of the mixer unit 204 through the LPF 205, the output of the mixer unit 204 corresponding to the reflected wave of the first chirp signal is out of the passband of the LPF 205. Since the frequency is high, the LPF 205 easily outputs a beat signal having a frequency corresponding to the delay time of the reflected wave signal of the second chirp signal.

On the other hand, for example, in an even-numbered transmission cycle, the second chirp signal output from the first or second switching unit 216 is the N3 antenna system processing units 201 out of the Na antenna system processing units 201. are input to the mixer section 204 in the receiving radio section 203 of each. In antenna system processing units 201-1 to 201-N3, by passing the output of mixer unit 204 through LPF 205, the output of mixer unit 204 corresponding to the reflected wave of the first chirp signal is outside the passband of LPF 205. Therefore, the LPF 205 easily outputs a beat signal having a frequency corresponding to the delay time of the reflected wave signal of the second chirp signal.

Also, for example, in even-numbered transmission cycles, the first chirp signal output from the first or second switching unit 216 is received by N4 antenna system processing units 201 out of Na antenna system processing units 201. They are input to mixer section 204 in radio section 203 . In the antenna system processing units 201-N3+1 to 201-Na, by passing the output of the mixer unit 204 through the LPF 205, the output of the mixer unit 204 corresponding to the reflected wave of the second chirp signal is outside the passband of the LPF 205. Therefore, the LPF 205 easily outputs a beat signal having a frequency corresponding to the delay time of the reflected wave signal of the first chirp signal.

Therefore, the antenna system processing units 201-1 to 201-N3, for example, process the reflected wave signals of the first chirp signals received by the receiving antennas 202-1 to 202-N3 in the odd-numbered transmission periods, and process the even-numbered transmission periods. , the reflected wave signals of the second chirp signals received by the receiving antennas 202-1 to 202-N3 in the transmission period of . After that, the antenna system processing unit 201 (for example, the reception radio unit 203 and the signal processing 206), and the receiving antenna 202 connected to these antenna system processing units 201 are referred to as a "first receiving sub-block".

Further, the antenna system processing units 201-N3+1 to 201-Na, for example, process reflected wave signals of the second chirp signals received by the receiving antennas 202-N3+1 to 202-Na in odd-numbered transmission cycles, and process even-numbered chirp signals. The reflected wave signals of the first chirp signals received by the receiving antennas 202-N3+1 to 202-Na in the th transmission period are processed. After that, the antenna system processing unit 201 (for example, the receiving radio unit 203 and the signal processing 206) and the receiving antenna 202 connected to these antenna system processing units 201 are referred to as a "second receiving sub-block".

Here, N3+N4=Na. Incidentally, N3 and N4 may each be 1 or more, and Na may be 2 or more.

For example, the first receiving sub-block (corresponding to the first receiving circuit, for example) mixes the signal received by the receiving antenna 202 using the first chirp signal in the odd-numbered transmission period, thereby obtaining the first A reflected wave signal of the chirp signal reflected by the target is output, and the signal received by the receiving antenna 202 is mixed with the second chirp signal in the even-numbered transmission period. Outputs the reflected wave signal. Also, the second reception sub-block (for example, corresponding to the second reception circuit) mixes the signal received by the reception antenna 202 using the second chirp signal in the odd-numbered transmission period to obtain the second The first chirp signal is reflected to the target by mixing the signal received by the receiving antenna 202 with the first chirp signal in even-numbered transmission periods. Outputs the reflected wave signal.

Note that the chirp signals to be processed in each reception sub-block in the odd-numbered and even-numbered transmission cycles (for example, the switching destinations of the first and second switching units 216) may be reversed. In this manner, the chirp signal to be processed in each reception sub-block may be alternately switched for each transmission cycle.

The signal processing unit 206 of each antenna system processing unit 201-z _q included in the q-th reception sub-block includes an A/D conversion unit 207, a beat frequency analysis unit 208, an output switching unit 217, and a Doppler analysis unit 210. , have Here, when q=1, z ₁ = any of 1 to N3, and when q=2, z ₂ = any of N3+1 to Na.

A signal (for example, a beat signal) output from the LPF 205 is converted into discrete sample data that is discretely sampled by the A/D conversion section 207 in the signal processing section 206 .

A beat frequency analysis unit 208 included in the first reception sub-block performs FFT processing on N _data pieces of discrete sample data obtained in a predetermined time range (range gate) for each transmission cycle _Tr . Here, the range gate sets the frequency sweep time T _sw (q). For example, q=1,2, where T _sw (1) represents the frequency sweep time of the first chirp signal when q=1, and T _sw (2) represents the frequency sweep time of the second chirp signal when q=2. represents the frequency sweep time of the signal. In the beat frequency analysis section 208 included in the first reception sub-block, for example, q=1 may be set in odd-numbered transmission cycles, and q=2 may be set in even-numbered transmission cycles. As a result, in the signal processing unit 206 of the first reception sub-block, for example, the reflected wave signal (radar reflected wave) is delayed with respect to the first chirp signal in odd-numbered transmission cycles and the second chirp signal in even-numbered transmission cycles. A frequency spectrum is output in which a peak appears at the beat frequency corresponding to time.

Also, beat frequency analysis section 208 included in the second reception sub-block performs FFT processing on N _data pieces of discrete sample data obtained in a predetermined time range (range gate) for each transmission period _Tr . Here, the range gate sets the frequency sweep time T _sw (q). For example, q=1,2, where T _sw (1) represents the frequency sweep time of the first chirp signal when q=1, and T _sw (2) represents the frequency sweep time of the second chirp signal when q=2. represents the frequency sweep time of the signal. In the beat frequency analysis section 208 included in the second reception sub-block, for example, q=2 may be set in odd-numbered transmission cycles, and q=1 may be set in even-numbered transmission cycles. As a result, in the signal processing unit 206 of the second reception sub-block, for example, the reflected wave signal (radar reflected wave) is delayed with respect to the second chirp signal in odd-numbered transmission cycles and the first chirp signal in even-numbered transmission cycles. A frequency spectrum is output in which a peak appears at the beat frequency corresponding to time.

Here, the beat frequency response output from the beat frequency analysis section 208 in the zq-th signal processing section 206 of the _q-th reception sub-block obtained by the m-th chirp pulse transmission is expressed as "RFT _zq (f _b , m)”. where f _b represents the beat frequency index and corresponds to the FFT index (bin number). For example, _{f b} =0,˜,N _data /2−1, z ₁ =1˜N3, z ₂ =N3+1˜Na, m=1˜2NC, q=1 or 2. A smaller beat frequency index f _b indicates a beat frequency with a shorter delay time of the reflected wave signal (eg, closer to the target).

For example, when m is an odd number, RFT _z1 (f _b , m) represents a frequency spectrum in which a peak appears at the beat frequency corresponding to the delay time of the reflected wave signal (radar reflected wave) with respect to the first chirp signal, and RFT _z2 (f _b , m) represents a frequency spectrum in which a peak appears at the beat frequency corresponding to the delay time of the reflected wave signal (radar reflected wave) with respect to the second chirp signal. On the other hand, for example, when m is an even number, RFT _z1 (f _b , m) is a frequency spectrum in which a peak appears at the beat frequency corresponding to the delay time of the reflected wave signal (radar reflected wave) with respect to the second chirp signal. RFT _z2 (f _b , m) represents a frequency spectrum in which a peak appears at the beat frequency corresponding to the delay time of the reflected wave signal (radar reflected wave) with respect to the first chirp signal.

Output switching section 217 in _z1 -th signal processing section 206 of the first reception sub-block converts beat frequency response RFT _z1 (f _b , m) input from beat frequency analysis section 208 to is output to the first Doppler analysis unit 210 (or Doppler analysis unit 210-1), and if m is an even number, switch to output to the second Doppler analysis unit 210 (or Doppler analysis unit 210-2) take action.

Output switching section 217 in z ₂ -th signal processing section 206 of the second reception sub-block converts beat frequency response RFT _z2 (f _b , m) input from beat frequency analysis section 208 to If m is an even number, the output is switched to the first Doppler analysis unit 210 .

As a result, any of the first Doppler analysis sections 210 of each reception sub-block processes the reflected wave signals for the first chirp signals received by the reception antennas 202-1 to 202-N3 in the odd-numbered transmission periods. , reflected wave signals for the first chirp signals received by the receiving antennas 202-N3+1 to 202-Na in even-numbered transmission periods are processed. Further, any of the second Doppler analysis units 210 of each reception sub-block processes the reflected wave signal for the second chirp signal received by the reception antennas 202-N3+1 to 202-Na in the odd-numbered transmission period, Reflected wave signals for the second chirp signals received by the receiving antennas 202-1 to 202-N3 in even-numbered transmission periods are processed.

Further, for example, the first reception sub-block processes reflected wave signals for the first chirp signals received by the reception antennas 202-1 to 202-N3 in odd-numbered transmission cycles, and processes reflected wave signals in even-numbered transmission cycles. , the reflected wave signals for the second chirp signals received by the receiving antennas 202-1 to 202-N3 are processed. Further, for example, the second reception sub-block processes the reflected wave signal for the second chirp signal received by the reception antennas 202-N3+1 to 202-Na in the odd-numbered transmission period, and processes the reflected wave signal in the even-numbered transmission period. , the reflected wave signals for the first chirp signals received by the receiving antennas 202-N3+1 to 202-Na are processed.

The first Doppler analysis unit 210 in the _z1- th signal processing unit 206 of the first reception sub-block calculates the beat frequency response RFT _z1 (f _b , 1) obtained by N _C chirp pulse transmissions of the first chirp signal. _, RFT _z1 (f _b , 3), . For example, the first Doppler analysis unit 210 may estimate the Doppler frequency from the reflected wave signal of the first chirp signal reflected from the target.

Also, the second Doppler analysis unit 210 in _{the z1} -th signal processing unit 206 of the first reception sub-block obtains the beat frequency response RFT _z1 (f _b , 2) Doppler analysis for each distance index f _b using RFT _z1 (f _b , 4), . . . For example, the second Doppler analysis unit 210 may estimate the Doppler frequency from the reflected wave signal of the second chirp signal reflected from the target.

Also, the first Doppler analysis unit 210 in the z ₂ -th signal processing unit 206 of the _second reception sub-block obtains the beat frequency response RFT _z2 (f _b , 2) Doppler analysis for each distance index f _b using RFT _z2 (f _b , 4), . . . For example, the first Doppler analysis unit 210 may estimate the Doppler frequency from the reflected wave signal of the first chirp signal reflected from the target.

In addition, the second Doppler analysis unit 210 in the z ₂ -th signal processing unit 206 of the second _reception sub-block obtains the beat frequency response RFT _z2 (f _b , 1), RFT _z2 (f _b , 3), . . . are used to perform Doppler analysis for each distance index f _b . For example, the second Doppler analysis unit 210 may estimate the Doppler frequency from the reflected wave signal of the second chirp signal reflected from the target.

For example, if _Nc is a power of 2, FFT processing can be applied in Doppler analysis. In this case, the FFT size is N _c , and the maximum Doppler frequency without aliasing derived from the sampling theorem is ±1/(4T _r ). Also, the Doppler frequency interval of the Doppler frequency index _fs is 1/( _Nc × _2Tr ), and the range of the Doppler frequency index _fs is _fs = _-Nc /2, ~, 0, ~, _Nc / 2-1.

A case where N _c is a power of 2 will be described below as an example. If N _c is not a power of 2, for example, FFT processing can be performed with a data size of powers of 2 by including zero-padded data. Also, the Doppler analysis unit 210 may multiply window function coefficients such as a Han window or a Hamming window during FFT processing. By applying the window function, side lobes generated around the beat frequency peak can be suppressed.

For example, the output VFT z1,1 (f b , f s ) of the first Doppler analysis unit 210 and the output VFT _z1,1 (f _b , f _s ) of the second Doppler analysis unit 210 in the z ₁ -th signal processing unit 206 of the first reception sub-block _z1,2 (f _b , f _s ) is given by the following equations (72) and (73). Note that j is an imaginary unit and z ₁ =1 to N3.

Also, for example, the output VFT _z2,1 (f _b , f _s ) of the first Doppler analysis unit 210 in the z ₂ -th signal processing unit 206 of the second reception sub-block, and the The output VFT _z2,2 (f _b , f _s ) is given by the following equations (74) and (75). Note that j is an imaginary unit, and z ₂ =N3+1 to Na.

The processing in each component of the signal processing unit 206 has been described above.

The CFAR unit 211 includes, for example, a first CFAR unit 211 (or a CFAR unit 211-1) and a second CFAR unit 211 (or a CFAR unit 211-1) corresponding to a first chirp signal and a second chirp signal having different center frequencies. 2). Similarly, the Doppler demultiplexing unit 212 includes, for example, a first Doppler demultiplexing unit 212 (or a Doppler demultiplexing unit 212-1) and a second A 2-Doppler demultiplexer 212 (or Doppler demultiplexer 212-2) may be provided.

FIG. 19 shows a configuration in which CFAR units 211 are provided in parallel (CFAR units 211-1 and 211-2). It's okay. FIG. 19 shows a configuration in which Doppler demultiplexing units 212 are provided in parallel (Doppler demultiplexing units 212-1 and 212-2). may be configured to switch to and process.

In FIG. 19, the CFAR unit 211 performs CFAR processing (for example, adaptive threshold determination) using the output from the Doppler analysis unit 210 of the signal processing unit 206 included in the first and second reception sub-blocks. Extract the distance index f _{b_cfar} and the Doppler frequency index f _{s_cfar} that give a realistic peak signal.

In FIG. 19, CFAR section 211 performs CFAR processing using the output of first Doppler analysis section 210 of signal processing section 206 included in the first and second reception sub-blocks (or CFAR section 211 -1), and second CFAR unit 211 (or CFAR unit 211- 2).

The first CFAR unit 211 performs, for example, the first Doppler analysis of the signal processing unit 206 included in the first and second reception sub-blocks, which is the result of estimating the Doppler frequency from the reflected wave signal of the first chirp signal reflected from the target. The output from unit 210 is used to perform CFAR processing (eg, adaptive thresholding) to extract the distance index f _{b_cfar} and Doppler frequency index f _{s_cfar} that give the local peak signal.

In addition, the second CFAR unit 211 is, for example, the result of estimating the Doppler frequency from the reflected wave signal of the second chirp signal reflected from the target. CFAR processing (for example, adaptive threshold determination) is performed using the output from the Doppler analysis unit 210 to extract the distance index f _{b_cfar} and the Doppler frequency index f _{s_cfar} that give the local peak signal.

The q-th CFAR unit 211 (q=1, 2) converts the output of the q-th Doppler analysis unit 210 of the signal processing unit 206 included in the first and second reception sub-blocks into the power Then, two-dimensional CFAR processing consisting of the distance axis and Doppler frequency axis (corresponding to relative velocity) or CFAR processing combining one-dimensional CFAR processing is performed. For CFAR processing that combines two-dimensional CFAR processing or one-dimensional CFAR processing, for example, the processing disclosed in Non-Patent Document 2 may be applied. Here, z ₁ =1 to N3, z ₂ =N3+1 to Na.

The q-th CFR section 211 adaptively sets a threshold, and uses the distance index f _{b_cfar} (q), the Doppler frequency index f _{s_cfar} (q), and the received power information PowerFT(f _{b_cfar} (q ), f _{s_cfar} (q)) to the q-th Doppler demultiplexer 212 .

Doppler demultiplexing section 212 performs Doppler demultiplexing processing using the output of first CFAR section 211 and the output of first Doppler analysis section 210 of signal processing section 206 included in each received sub-block. The output of demultiplexing section 212 (or Doppler demultiplexing section 212-1), the output of second CFAR section 211, and the output of second Doppler analysis section 210-2 of signal processing section 206 included in each received sub-block are A second Doppler demultiplexing unit 212 (or represented as Doppler demultiplexing unit 212-2) that performs Doppler demultiplexing processing may be provided.

The q-th Doppler demultiplexing unit 212 (q=1, 2) receives information input from the q-th CFAR unit 211 (for example, distance index f _{b_cfar} (q), Doppler frequency index f _{s_cfar} (q), and received power information Based on PowerFT (f _{b_cfar} (q), f _{s_cfar} (q))), the output from the q-th Doppler analysis unit 210 included in each reception sub-block is used to generate a Doppler-multiplexed signal (hereinafter referred to as “Doppler A transmission signal transmitted from each transmission antenna 106 (for example, a reflected wave signal for the transmission signal) is separated from the multiplexed signal).

The q-th Doppler demultiplexer 212 outputs, for example, information about the demultiplexed signal to the Doppler determiner 213 and the direction estimator 214 . Information about the separated signal may include, for example, a distance index f _{b_cfar} (q) corresponding to the separated signal and a Doppler frequency index (hereinafter also referred to as separation index information). Here, the demultiplexing index information of the first Doppler demultiplexing unit 212 is the Doppler frequency index obtained by demultiplexing the signals transmitted from the transmitting antennas Tx#1, Tx#2, . , which are respectively represented as (f _{demul_Tx#1} , f _{demul_Tx#2} , ~, f _{demul_Tx#N1} ). Similarly, the demultiplexing index information of the second Doppler demultiplexing unit 212 demultiplexes the signals transmitted from the transmitting antennas Tx#N1+1, Tx#N1+2, . are Doppler frequency indices, and are respectively represented by (f _{demul_Tx#N1+1} , f _{demul_Tx#N1+2} , ~, f _{demul_Tx#Nt} ).

The q-th Doppler demultiplexer 212 also outputs the output from the q-th Doppler analyzer 210 to the direction estimator 214 . Note that the q-th Doppler demultiplexing unit 212 receives information input from the q-th CFAR unit 211 (for example, distance index f _{b_cfar} (q), Doppler frequency index f _{s_cfar} (q), and received power information PowerFT(f _{b_cfar} ( q), f _{s_cfar} (q))), the output from Doppler analysis section 210 included in the q-th received sub-block may be output to direction estimation section 214 .

An example of the operation of the q-th Doppler demultiplexer 212 will be described below together with the operation of the Doppler shifter 105 in the radar transmitter 100b.

[How to set Doppler shift]
An example of a method for setting the Doppler shift amount given by the Doppler shift unit 105 will be described.

In this embodiment, the inputs of the first chirp signal and the second chirp signal to the mixer section 204 are switched between the odd-numbered transmission period and the even-numbered transmission period, and the same transmission phase change occurs in these received signals. Granted. Therefore, it is different from the third embodiment in that the Doppler shift section 105 gives the same phase rotation to the odd-numbered transmission period and the even-numbered transmission period. For example, Doppler shift section 105 gives the chirp signal a phase rotation set to the same Doppler shift amount as in Embodiment 3 in odd-numbered transmission cycles, and in even-numbered transmission cycles, the preceding odd-numbered transmission The same phase rotation as the phase rotation imparted to the period is imparted to the chirp signal.

For example, the present embodiment differs from the formulas (62) and (63) described in the third embodiment in the following points.

The Doppler shift sections 105-1 to 105-N1 of the first transmission sub-block perform different Doppler shifts among the Doppler shift sections 105 for the input odd-numbered m=2u-1-th first chirp signal. Add phase rotation φ _nsub1 (2u-1) as shown in the following equation (77), which becomes the shift amount DOP _nsub1 , and output the Doppler-shifted signal to the transmitting antenna 106 (for example, Tx#1 to Tx#N1) do. Here, nsub1=1 to N1 and u=1 to Nc.

In addition, Doppler shift sections 105-1 to 105-N1 of the first transmission sub-block perform respective Doppler shift shifts for the subsequently input even-numbered m=2u-th chirp signal in the same manner as the odd-numbered first chirp signal. A phase rotation φ _nsub1 (2u) given by the following equation (78) is applied, which makes the Doppler shift amounts DOP _nsub1 different between the shift sections 105 .

As a result, transmission signals transmitted from a plurality of transmission antennas 106 (for example, Tx#1 to Tx#N1) included in the first transmission subblock are given different Doppler shift amounts in each transmission cycle. . Also, transmission signals transmitted from the transmission antennas 106 (eg, Tx#1 to Tx#N1) included in the first transmission sub-block may be Doppler-multiplexed, for example, with the Doppler multiplexing number N _DM =N1.

Similarly, the Doppler shift units 105-N1+1 to 105-Nt of the second transmission sub-block receive the input odd-numbered m=2u−1-th second chirp signal between the Doppler shift units 105 as follows: A phase rotation φ _nsub2 (m) as shown in the following equation (79) is applied to give Doppler shift amounts DOP _nsub2 different from each other, and the signals after the Doppler shift are transmitted to the transmitting antenna 106 (for example, Tx# N1+1 to Tx#Nt ). Here, nsub2=1 to N2 and u=1 to Nc.

In addition, Doppler shift sections 105-N1+1 to 105-Nt of the second transmission sub-block shift the Doppler shift units 105-N1+1 to 105-Nt of the subsequently input even-numbered m=2u-th chirp signal to each Doppler shift unit in the same manner as the odd-numbered A phase rotation φ _nsub2 (2u) given by the following equation (80) is applied, which gives different Doppler shift amounts DOP _nsub2 between the shift sections 105 .

As a result, transmission signals transmitted from a plurality of transmission antennas 106 (for example, Tx#N1+1 to Tx#Nt) included in the second transmission subblock are given different amounts of Doppler shift in each transmission cycle. be done. Also, transmission signals transmitted from the transmission antennas 106 (eg, Tx# N1+1 to Tx#Nt) included in the second transmission sub-block may be Doppler-multiplexed with a Doppler multiplexing number N _DM =N2, for example. .

It should be noted that the setting of the Doppler shift amount in Doppler shift section 105 described in Embodiment 3 may be applied to this embodiment without being limited to Expressions (62) and (63).

For example, the radar device 10b may perform unequal interval Doppler multiplexing on the first chirp signal and the second chirp signal with the Doppler multiplexing numbers N1 and N2, respectively. Alternatively, the radar apparatus 10b may perform unequal interval Doppler multiplexing on at least one of the first chirp signal and the second chirp signal at Doppler multiplexing numbers N1 and N2, respectively.

[Operation example of Doppler demultiplexing unit 212]
The first Doppler demultiplexing unit 212 performs the interval of the Doppler shift amount DOP _nsub1 between the Doppler shift units 105-1 to 105-N1 included in the first transmission sub-block (for example, between the transmission antennas 106-1 to 106-N1). To separate and receive signals transmitted with (Doppler shift intervals) set not at equal intervals but with at least one Doppler interval being different.

First Doppler demultiplexing section 212 demultiplexes signals Doppler-multiplexed at unequal intervals based on the outputs of first Doppler analysis section 210 and first CFAR section 211 in the first and second reception sub-blocks. Then _, first Doppler demultiplexing section 212 provides demultiplexing index information ₍ f _{demul_Tx #1} , f demul_Tx _{# 2} , .

In the present embodiment, the inputs of the first chirp signal and the second chirp signal to mixer section 204 are switched between the odd-numbered transmission period and the even-numbered transmission period, and these received signals have the same transmission phase. Change is granted. Therefore, the Doppler shifter 105 applies the same phase rotation to the odd-numbered transmission period and the even-numbered transmission period. Correspondingly, the operation of the first Doppler demultiplexing unit 212 is the same as that in the description of the operation of the Doppler shift unit 105 in Embodiment 1, where “Nt” is replaced with “N1” and “T _rs ” is replaced with “2T _r , the signals Doppler-multiplexed between the transmitting antennas 106-1 to 106-N1 can be separated. Therefore, detailed description of the operation of the first Doppler demultiplexer 212 is omitted.

Similarly, second Doppler demultiplexing section 212 performs Doppler shift amount DOP Signals transmitted with not equal _nsub2 intervals (Doppler shift intervals) but with at least one different Doppler interval are separately received.

Second Doppler demultiplexing section 212 demultiplexes signals Doppler-multiplexed at unequal intervals based on the outputs of second Doppler analysis section 210 and second CFAR section 211 in the first and second reception sub-blocks. Then _, second Doppler demultiplexing section 212 provides demultiplexing index information ₍ f _{demul_Tx #N1+1} , f demul_Tx# _{N1+ 2 ,} .

In this embodiment, the input of either the first chirp signal or the second chirp signal to mixer section 204 is switched between the odd-numbered transmission period and the even-numbered transmission period. The same transmit phase change is applied. Therefore, the Doppler shifter 105 gives the same phase rotation in the odd-numbered transmission period and the even-numbered transmission period. Correspondingly, the operation of the second Doppler demultiplexing unit 212 is described in the description of the operation of the Doppler shift unit 105 in the first embodiment by replacing "Nt" with "N2" and "T _rs " with "2T _r , can be used to separate Doppler-multiplexed signals among the transmitting antennas 106-N1+1 to 106-Nt. Therefore, detailed description of the operation of the second Doppler demultiplexing unit 212 is omitted.

[Example of operation of Doppler determination unit 213]
In FIG. 19 , the Doppler determining section 213 determines the Doppler frequency corresponding to the Doppler peak based on the outputs of the first Doppler demultiplexing section 212 and the second Doppler demultiplexing section 212 . For example, the Doppler determination unit 213 determines that even if the Doppler frequency _{fd_TargetDoppler} of the target includes a target with a Doppler frequency exceeding the Doppler frequency range −1/(2T _r )≦ _{fd_TargetDoppler} <1/(2T _r ), By determining the target Doppler frequency, the Doppler detection range can be further expanded.

For _example , the Doppler determination unit 213 uses separation index information (f _{demul_Tx #1} , f _{demul_Tx#2} , ~, f _{demul_Tx#N1} ) and separation index information (f _{demul_Tx#N1+1} , f _{demul_Tx#N1+2} , ~, f _{demul_Tx#Nt} ) is used to determine the Doppler frequencies of targets that include Doppler frequencies above the Doppler frequency range -1/(2T _r ) ≤ _{fd_TargetDoppler} < 1/(2T _r ).

The principle of determining the Doppler frequency of the target including the Doppler frequency exceeding the Doppler frequency range −1/(2T _r )≦f _{d_TargetDoppler} <1/(2T _r ) in the Doppler determination unit 213 is the same as in the first embodiment. The fact that the first chirp signal and the second chirp signal, which are radar transmission signals generated by the generation control unit 104 and the radar transmission signal generation unit 101, have different center frequencies is utilized.

In Embodiment 1, Doppler frequency determination is performed based on changes in Doppler frequencies in Doppler multiplexed signals for the same transmit antenna 106 . In contrast, in the present embodiment, Doppler determination section 213 determines the Doppler frequency based on the change in Doppler frequency in Doppler multiplexed signals for different transmitting antennas 106 . When using different transmit antennas 106, the receive phase changes, but the received Doppler frequency does not change. Therefore, as in Embodiment 1, the Doppler determination unit 213 determines the Doppler frequency of the target including the Doppler frequency exceeding the Doppler frequency range −1/(2T _r ) ≦ f _{d_TargetDoppler} <1/(2T _r ). can.

Regarding the operation principle of the Doppler frequency determination process and the operation example of the Doppler determination unit 213, with respect to the description of the operation principle of the Doppler frequency determination process and the operation example of the Doppler determination unit 213 in Embodiment 1 , differ in the following points (1), (2) and (3).
(1) Replacing “T _rs ” with “2T _r ”;
(2) Doppler determination section 213 according to Embodiment 1 performs separation index information (f _{demul_Tx #1} (1), f _{demul_Tx#2} (1), ~, f _{demul_Tx#Nt} (1)), the Doppler frequency of the target is within the Doppler frequency range -1/(2T _rs ) ≤ f _{d_TargetDoppler} < 1/(2T _rs ) Calculate the Doppler frequency estimate f _{d_VFT} (1) assuming that On the other hand, in the present embodiment, Doppler determination section 213 uses separation index information (f _{demul_Tx #1} , f _{demul_Tx#2} , ~, f _{demul_Tx#N1} ), the Doppler frequency assuming the target Doppler frequency is within the Doppler frequency range -1/(4T _r ) ≤ f _{d_TargetDoppler} < 1/(4T _r ) a point for calculating the frequency estimate f _{d_VFT} (1), and
(3) Doppler determination section 213 in Embodiment 1 performs separation index information (f _{demul_Tx #1} (2), f _{demul_Tx#2} (2), ~, f _{demul_Tx#Nt} (2)), the Doppler frequency of the target is within the Doppler frequency range -1/(2T _rs ) ≤ f _{d_TargetDoppler} < 1/(2T _rs ) Calculate the Doppler frequency estimated value f _{d_VFT} (2) assuming that On the other hand, in the present embodiment, Doppler determination section 213 uses separation index information (f _{demul_Tx #N1+1} , f _{demul_Tx# N1+2} ,~, f _{demul_Tx#Nt} ), assume that the target Doppler frequency is within the Doppler frequency range -1/(4T _r ) ≤ f _{d_TargetDoppler} < 1/(4T _r ) A point for calculating the Doppler frequency estimate f _{d_VFT} (2) when

In the present embodiment, the operation of the Doppler determination unit 213, which is different from the above three points, is the same as that of the first embodiment, so the explanation of the operation is omitted.

Further, similarly to the Doppler determination unit 213 in Embodiment 1, the center frequency f _c (that satisfies any of the determination enable conditions of formulas (10) to (15) in which "T _rs " is replaced with "2T _r ". By setting 1) and f _c (2), the Doppler determination unit 213 determines that when a target with a Doppler frequency exceeding the Doppler frequency range -1/(2T _r ) ≤ f _{d_TargetDoppler} <1/(2T _r ) is included ( For example, even if Doppler folding occurs, the Doppler frequency of the target can be determined. Equations (10) and (13) are equations that include T _rs , but by transforming the equations, T An expression without _rs is obtained. Therefore, the center frequencies f _c (1) and f _c (2) that satisfy the determination condition are the same conditions as in the first embodiment.

Note that equation (18) used to describe the first embodiment is expressed as the following equation (81) by replacing T _rs with 2T _r .

Expression (81) expresses the Doppler frequency aliasing component n _{al × {f c (} 2)/f _c (1)}/2T _r and _2n al /T _r , which is the frequency interval of the number of times n _al of folding in the first Doppler analysis unit 210, does not exceed ±1/(4T _r ). For example, when n _al is positive, Δn _al is in the range of ±1/(4T _r ) up to the maximum n _al that satisfies Equation (19), and the Doppler determination unit 213 can unambiguously estimate aliasing. Note that the maximum n _al that satisfies Equation (19) is denoted as “n _almax ”. For example, when n _al is negative, n _al =−n _almax satisfies Equation (19) in the same way.

Here, in Embodiment 1, the first chirp signal or the second chirp signal is transmitted at the T _rs period, and the detection range of the Doppler frequency is, for example, n _almax times the Doppler frequency range for one transmitting antenna. is expanded to On the other hand, in the present embodiment, a signal corresponding to the first chirp signal or the second chirp signal is input to the first or second Doppler analysis unit 210 via the output switching unit 217 at a 2T _r cycle. , frequency analysis processing is performed. Therefore, in the present embodiment, the Doppler frequency detection range is the same as in the first embodiment, and is expanded, for example, n _almax times the Doppler frequency range for one transmitting antenna.

The operation example of the Doppler determination unit 213 has been described above.

[Example of Operation of Direction Estimation Unit 214]
In FIG. 19, the direction estimation unit 214 receives information input from the first Doppler demultiplexing unit 212 (for example, the distance index f _{b_cfar} (1) and the demultiplexing index information of the Doppler multiplexed signal at the distance index f _{b_cfar} (1) ( _{f demul_Tx#1 ,} f _{demul_Tx# 2} , . 2) Doppler multiplexed signal separation index information (f _{demul_Tx#N1+1} , f _{demul_Tx#N1+2} , ~, f _{demul_Tx#Nt} )), and Doppler frequency information f _dest = f _{The first Doppler analysis unit _ _ _} 210 and the output of the second Doppler analysis unit 210 are extracted, and target direction estimation processing is performed.

In this embodiment, N1 transmit antennas 106 included in the first transmit subblock, N3 receive antennas 202 included in the first receive subblock, and N4 receive antennas included in the second receive subblock 202, N1×(N3+N4)=N1×Na MIMO virtual receive antennas are configured. Similarly, N2 transmit antennas 106 included in the second transmit subblock, N3 receive antennas 202 included in the first receive subblock, and N4 receive antennas 202 included in the second receive subblock. , N2×(N3+N4)=N2×Na MIMO virtual receive antennas are configured. Direction estimation section 214 may perform direction estimation processing using these two sets of virtual reception antennas, for example, Nt×Na MIMO virtual reception antennas.

For example, the direction estimation unit 214 obtains the distance index f _{b_cfar} (1) and separation index information ₍ f _{demul_Tx#1} , f _{demul_Tx#2} , ~, f _{demul_Tx#N1} ), the output of the first Doppler analysis unit 210 is extracted, and the first Generate a virtual receive array correlation vector h ₁ (f _{b_cfar} (1), f _{demul_Tx#1} , f _{demul_Tx#2} , ~, f _{demul_Tx#N1} ).

Further, the direction estimation unit 214, for example, from the output _of the second Doppler demultiplexing unit 212, the distance index f _{b_cfar} (2) and the demultiplexing index information (f _{demul_Tx# N1+1} , f _{demul_Tx#N1+2} , ~, f _{demul_Tx#Nt} ), the output of the second Doppler analysis unit 210 is extracted, and N2×(N3+N4) as shown in the following equation (83) A second virtual receive array correlation vector h ₂ (f _{b_cfar} (2), f _{demul_Tx#N1+1} , f _{demul_Tx#N1+2} , ~, f _{demul_Tx#N1} ) consisting of elements is generated.

Since the direction estimator 214 performs direction estimation processing using the outputs of the first and second Doppler demultiplexers 212 with the same distance index, f _{b_cfar} (1) = f _{b_cfar} (2) = f _{b_cfar} .

In equation (82), h ₁₁ (f _{b_cfar} , f _{demul_Tx#1} , f _{demul_Tx#2} , ~, f _{demul_Tx#N1} ) is a column vector consisting of N1×N3 elements as in equation (84) of the first Doppler analysis unit 210 obtained by receiving the signals transmitted from the N1 transmitting antennas 106 included in the first transmitting subblock with the N3 receiving antennas 202 included in the first receiving subblock. A vector containing the output as elements.

Also, in equation (82), h ₂₁ (f _{b_cfar} , f _{demul_Tx#1} , f _{demul_Tx#2} , ~, f _{demul_Tx#N1} ) consists of N1×N4 elements as in equation (85) It represents a column vector and is obtained by receiving signals transmitted from N1 transmitting antennas 106 included in the first transmitting subblock with N4 (=Na−N3) receiving antennas 202 included in the second receiving subblock. is a vector containing the output of the second Doppler analysis unit 210 as an element.

In addition, in equation (83), h ₁₂ (f _{b_cfar} , f _{demul_Tx#N1+1} , f _{demul_Tx#N1+2} , ~, f _{demul_Tx#Nt} ) has N2 × N3 The signals transmitted from N2 (=Nt−N1) transmitting antennas 106 included in the second transmitting subblock are transmitted from N3 receiving antennas 202 included in the first receiving subblock. It is a vector containing the output of the second Doppler analysis unit 210 obtained by reception as an element.

In addition, in equation (83), h ₂₂ (f _{b_cfar} , f _{demul_Tx#N1+1} , f _{demul_Tx#N1+2} , ~, f _{demul_Tx#Nt} ) has N2 × N4 N4 (=Na-N3) signals transmitted from N2 (=Nt−N1) transmitting antennas 106 included in the first transmitting subblock are represented by N4 (=Na−N3) included in the second receiving subblock. 2 is a vector containing as elements the outputs of the second Doppler analysis unit 210 obtained by receiving with the receiving antennas 202 .

Also, for the reception timing of _h11 (f _{b_cfar} , f _{demul_Tx#1} , f _{demul_Tx#2} , ~, f _{demul_Tx#N1} ), _h21 (f _{b_cfar} , f _{demul_Tx#1} , f _{demul_Tx#2} , ~, f _{demul_Tx#N1} ) is delayed _{by Tr} . The term exp[-j2πf _dest T _r ] included in equation (82) is a correction term for correcting the phase fluctuation due to the delay based on the Doppler frequency f _dest of the target estimated by the Doppler determination section 213 .

Also, for the reception timing of _h22 (f _{b_cfar} , f _{demul_Tx#1} , f demul_Tx _{# 2} , ~, f _{demul_Tx#N1} ), _h12 (f _{b_cfar} , f demul_Tx#1, f _{demul_Tx#2} , ~ f _{demul_Tx #N1} ) is delayed by _Tr . The term exp[-j2πf _dest T _r ] included in equation (83) is a correction term for correcting the phase fluctuation due to the delay based on the Doppler frequency f _dest of the target estimated by the Doppler determination section 213 .

Also, in equations (84) and (85), h _1cal[b] is an array that corrects the phase deviation and amplitude deviation between the transmitting antennas Tx#1 to Tx#N1 and between the receiving antennas Rx#1 to #Na. Correction value. Integer b=1 to (Na×N1).

Also, in equations (86) and (87), h _2cal[bb] corrects the phase deviation and amplitude deviation between the transmitting antennas Tx#N1+1 to Tx#Nt and between the receiving antennas Rx#1 to #Na. is the array correction value for Integer bb=1 to (Na×N2).

The direction estimation unit 214, for example, determines the azimuth direction θ _u in the direction estimation evaluation function value _PH (θ _u , f _{b_cfar} , f _{demul_Tx#1} , f _{demul_Tx#2} , ~, f _{demul_Tx#Nt} ) within a predetermined angle range. , the spatial profile is calculated as variable. The direction estimation unit 214 extracts a predetermined number of maximal peaks of the calculated spatial profile in descending order, and outputs the azimuth directions of the maximal peaks as direction-of-arrival estimation values (for example, positioning output). Here, _{fb_cfar} represents a distance index that satisfies _{fb_cfar} (1)= _{fb_cfar} (2).

The direction estimation evaluation function value P _H (θ _u , f _{b_cfar} , f _{demul_Tx#1} , f _{demul_Tx#2} , ~, f _{demul_Tx#Nt} ) has various methods depending on the direction of arrival estimation algorithm. For example, an estimation method using an array antenna disclosed in Non-Patent Document 3 may be used.

For example, the beamformer method can be expressed as in Equation (88) below. In addition to the beamformer method, methods such as Capon and MUSIC are also applicable. Note that in equation (88), the superscript H is the Hermitian transpose operator.

In equation (88), a ₁ (θ _u ) is between the N1 transmit antennas 106 included in the first transmit subblock and the Na receive antennas 202 included in the first and second receive subblocks. N1×Na MIMO virtual reception antenna direction vectors (column vectors with N1×Na elements), and N1×Na MIMO virtual reception antennas when _reflected waves arrive from Represents the phase or complex amplitude response at each virtual receive antenna that makes up the antenna.

Also, in equation (88), a ₂ (θ _u ) is the N2 transmit antennas 106 included in the second transmit subblock and the Na receive antennas 202 included in the first and second receive subblocks. N2×Na MIMO virtual receiving antenna directional vectors (column vectors with N2×Na elements), and N2×Na MIMO when reflected waves arrive from _u direction Represents the phase response or complex amplitude response at each virtual receive antenna that constitutes the virtual receive antenna.

Note that the directional vector a _q (θ _u ) is _the phase response or complex Amplitude response may be used. Alternatively, the direction vector a(θ _u ) of the virtual receiving array for the incoming wave in the azimuth direction θ at the average center frequency of the center frequencies f _c (1) and f _c (2) may be used in common.

Also, the azimuth direction θ _u is a vector obtained by changing the azimuth range in which direction-of-arrival estimation is performed at a predetermined azimuth interval β ₁ . For example, θ _u is set as follows.
_θu = θmin + uβ ₁ , integer u = 0 to NU
NU=floor[(θmax−θmin)/ _β1 ]+1
where floor(x) is a function that returns the largest integer value that does not exceed the real number x.

In the above example, the direction estimator 214 calculates the azimuth direction as the direction-of-arrival estimation value. However, the present invention is not limited to this. Direction-of-arrival estimation in azimuth and elevation directions is also possible by using MIMO antennas. For example, the direction estimator 214 may calculate the azimuth direction and the elevation angle direction as the direction-of-arrival estimation values and use them as the positioning output.

Through the above operation, the direction estimation unit 214 uses the distance index f _{b_cfar} and the direction-of-arrival estimated value in the separation index information (f _{demul_Tx#1} , f _{demul_Tx#2} , to, f _{demul_Tx#Nt} ) of the Doppler multiplexed signal as the positioning output. can be output. Moreover, the direction estimation unit 214 may further output the distance index _{fb_cfar} and separation index information (f _{demul_Tx#1} , f _{demul_Tx#2} , to f _{demul_Tx#Nt} ) of the Doppler multiplexed signal as the positioning output. The direction estimator 214 may output the positioning output (or the positioning result) to, for example, a vehicle control device for an in-vehicle radar or an infrastructure control device for an infrastructure radar (not shown).

Further, the direction estimation unit 214, for example, the Doppler frequency information f _{d_VFT(1)} +n _alest /T _rs determined by the Doppler determination unit 213 and f _c (2)/f _c (1) (f _{d_VFT(1 )} +n _alest /T _rs ) or both of them may be output.

Further, the distance index f _{b_cfar} may be converted into distance information using Equation (1) and output.

Further, the Doppler frequency information determined by the Doppler determination unit 213 may be converted to relative velocity information and output. To convert the Doppler frequency information f _{d_VFT(1)} +n _alest /2T _r by the center frequency f _c (1) determined by the Doppler determination unit 213 to the relative velocity v _d , the following equation (89) is used. can be converted.

Similarly, the Doppler frequency information f _c (2)/f _c (1) (f _{d_VFT(1)} +n _alest /T _r ) by the center frequency f _c (2) determined by the Doppler determination unit 213 is used as the relative velocity When converted to v _d , the value is the same as in equation (89), as in equation (90) below, so the relative velocity component information is output as a common value (or unified value) for different center frequencies. may be

As described above, in the present embodiment, the radar device 10b includes a plurality of radar transmission signal generators 101, and for example, the first center frequency and the first 2 center frequencies, the transmission signal is transmitted from the transmission antenna 106 for each predetermined transmission period. As a result, the radar apparatus 10b can determine the number of loopbacks in the Doppler determination section 213 based on the deviation of the Doppler frequencies detected by the Doppler analysis section 210 and the Doppler demultiplexing section 212 according to the difference in center frequency. Therefore, the radar device 10b can expand the Doppler frequency range (or the maximum value of the relative velocity) in which the Doppler multiplexed signal can be separated, for example, according to the number of times of folding that can be determined.

As described above, according to the present embodiment, it is possible to expand the Doppler frequency range (or the maximum value of the relative velocity) in which ambiguity does not occur. Thereby, the radar device 10b can accurately detect a target (for example, the direction of arrival) in a wider Doppler frequency range.

In addition, in the present embodiment, the Doppler frequency range in which the Doppler multiplexed signal can be separated is expanded by setting the center frequency of the chirp signal. may be omitted. Therefore, according to the present embodiment, complication of the hardware configuration of the radar device 10b can be suppressed, and an increase in power consumption or heat generation in the radar device 10b can be suppressed. Further, in this embodiment, the Doppler frequency range in which the Doppler multiplexed signal can be separated is expanded by setting the center frequency of the chirp signal, so the application of the method of shortening the transmission period _Tr may be omitted. Therefore, according to the present embodiment, it is possible to suppress the reduction of the detectable distance range or the deterioration of the distance resolution in the radar device 10b.

Also, in the present embodiment, more MIMO virtual reception antennas can be used in direction estimation section 214 than in the third embodiment. As a result, the radar device 10b can improve the SNR and improve the direction estimation accuracy. In addition, in this embodiment, as compared with Embodiment 3, a greater number of MIMO virtual reception antennas can be used, so the aperture length of the MIMO virtual reception antennas can be increased, and the angular resolution can be improved. .

(Modification 1 of Embodiment 4)
The configuration of the radar device 10b shown in FIG. 19 may be realized by combining a plurality of transmitting/receiving chips, as shown in FIG. 20, for example. In the example of FIG. 20, the radar device 10b is composed of a transmitting/receiving chip #1 and a transmitting/receiving chip #2.

Transmission/reception chip #q includes radar transmission signal generation section 101-q, qth transmission sub-block, qth reception sub-block, qth CFAR section 211, qth Doppler demultiplexing section 212, and qth switching section 216. FIG. where q=1 or 2.

At least one of the Doppler determining unit 213 and the direction estimating unit 214 may be implemented in another signal processing chip or ECU, or may be incorporated in any of the transmitting/receiving chips.

20 differs from FIG. 19 in that a synchronization signal generator 215 is provided, and the synchronization signal (for example, a reference signal) output from the synchronization signal generator 215 is applied to the radar transmitter 100b of each transmission/reception chip. It is output to the radar transmission signal generator 101 . This allows a frequency difference between the first chirp signal output from the first transmission sub-block of the transmission/reception chip #1 and the second chirp signal output from the second transmission sub-block of the transmission/reception chip #2. It is possible to output a chirp signal that is within a predetermined error obtained. Even with the configuration shown in FIG. 20, the same effect as in the fourth embodiment can be obtained, and by combining general-purpose transmitting/receiving chips, the cost can be reduced.

An embodiment according to the present disclosure has been described above.

[Other embodiments]
(Variation 1)
For example, in Embodiment 1, an example of application to Doppler multiplexing MIMO radar with unequal Doppler multiplexing intervals was shown, but the present invention is not limited to this, and the number of transmitting antennas is one (Nt=1). (for example, SIMO (Single Input Multiple Output) radar).

Further, the operation according to Embodiment 1 can also be applied to a radar (for example, MISO (Multiple Input Single Output) radar) with one receiving antenna (Na=1).

Further, the operation according to Embodiment 1 is, for example, a radar (for example, SISO (Single Input Single Output ) radar).

Note that when there is one receiving antenna (Na=1), for example, it corresponds to setting Na=1 in the first embodiment, and the same effect as described in the first embodiment can be obtained.

Also, when there is one transmitting antenna (Nt=1), for example, it corresponds to setting Nt=1 in Embodiment 1, and the effect described in Embodiment 1 can be similarly obtained.

Note that when there is one transmission antenna (Nt=1), Doppler multiplex transmission may be omitted. Therefore, the Doppler shift in the Doppler shifter 105 may be omitted. Also, the Doppler demultiplexing unit 212 does not need to perform Doppler demultiplexing, and may perform peak extraction processing extracted from the Doppler analysis unit 210 of the index indicated by the output from the CFAR unit 211 . Therefore, when there is one transmitting antenna (Nt=1), for example, the configuration of the radar apparatus shown in FIG. 21 may be used.

FIG. 21 is a block diagram showing a configuration example of the radar device 10c. In FIG. 21, the same reference numerals are given to the same configurations as in Embodiment 1 (for example, FIG. 2), and the description thereof will be omitted. For example, the radar device 10c shown in FIG. 21 may have one transmitting antenna 106c (for example, Tx#1). Further, the radar device 10c may omit the Doppler shifter 105 in the radar device 10 shown in FIG. 1, for example. Also, the radar device 10c may include a q-th peak extractor 218 instead of the q-th Doppler demultiplexer 212, for example.

The operation of the radar device 10c that differs from that of the radar device 10 will be described below.

In FIG. 21 , the radar transmission signal output from radar transmission signal generation section 101 is output (radiated) from transmission antenna Tx# 1 without passing through Doppler shift section 105 .

In FIG. 21 , q-th CFR section 211 adaptively sets a threshold, and distance index f _{b_cfar} (q), Doppler frequency index f _{s_cfar} (q) information, and received power information PowerFT _q ( f _{b_cfar} (q) and f _{s_cfar} (q)) are output to the q-th peak extractor 218 . where q=1,2.

The q-th peak extraction unit 218 sets, for example, information about the Doppler frequency index f _{s_cfar} (q) to Doppler index information (f _{demul_Tx#1} (q)). Also, the q-th peak extraction unit 218 outputs, for example, the distance index f _{b_cfar} (q) and the Doppler index information (f _{demul_Tx#1} (q)) to the Doppler determination unit 213c. Further, the q-th peak extraction unit 218, for example, in addition to the distance index f _{b_cfar} (q), the Doppler index information (f _{demul_Tx#1} (q)), and the Doppler index information (f _{demul_Tx#1} (q)) The output of the corresponding q-th Doppler analysis unit 210 is output to the direction estimation unit 214c. where q=1,2.

The Doppler determination unit 213c uses the Doppler index information (f _{demul_Tx #1} (1)) output from the first peak extraction unit 218 and the _second Using the Doppler index information (f _{demul_Tx#1} (2)) output from the peak extraction unit 218, the Doppler frequency f _{d_TargetDoppler} of the target is set within the Doppler frequency range −1/(2T _rs ) ≦f _{d_TargetDoppler} <1/(2T The Doppler frequency is determined assuming that a target with a Doppler frequency exceeding _rs ) is included. Note that the operation of the Doppler determination unit 213c is the same as the operation of the Doppler determination unit 213 of Embodiment 1, so description thereof will be omitted.

The direction estimation unit 214c extracts the output of the q-th Doppler analysis unit 210 based on the distance index f _{b_cfar} (q) and the Doppler index information (f _{demul_Tx#1} (q)) from the q-th peak extraction unit 218, Generate the q-th virtual receive array correlation vector h _q (f _{b_cfar} (q), f _{demul_Tx#1} (q), f _{demul_Tx#2} (q), . . . , f _{demul_Tx#Nt} (q)) and perform direction estimation process. where q=1,2.

By the above operation, the same effects as in the first embodiment can be obtained even in the case of the radar device 10 (for example, SIMO radar) having one transmission antenna (Nt-1).

(Variation 2)
In each of the above-described embodiments, a case has been described in which radar transmission signals are simultaneously transmitted (Doppler multiplex transmission) from a plurality of transmission antennas 106 in the radar device 10. However, the present invention is not limited to this. A radar transmission signal may be transmitted by switching.

For example, as shown in FIG. 22 , when the radar device 10 switches between two transmitting antennas 106 to transmit a radar transmission signal (for example, a chirp signal), from the first transmitting antenna 106 (first transmitting antenna) , a first chirp signal with a center frequency f _c (1) is transmitted with a period T _rs1 , a second chirp signal with a center frequency f _c (2) is transmitted with a period T _rs1 , and obtained from reflected waves of these transmitted signals The same processing as in the first embodiment may be performed on the received signal. Thereby, the radar apparatus 10 can determine the Doppler frequency even when the Doppler frequency f _{d_TargetDoppler} of the target exceeds the Doppler frequency range −1/(2T _rs1 )≦f _{d_TargetDoppler} <1/(2T _rs ). Here, T _rs1 is the period of transmitting the first chirp signal (or the period of transmitting the second chirp signal) from the first transmitting antenna 106 .

Further, as shown in FIG. 22, the radar apparatus 10 transmits a first chirp signal having a center frequency f _c (1) from a second transmitting antenna 106 (second transmitting antenna) at a period T _rs2 and the center frequency The second chirp signal of f _c (2) may be transmitted with a period T _rs2 and the received signal obtained from the reflected wave of the transmitted signal may be processed in the same manner as in the first embodiment. As a result, the radar device 10 can determine the Doppler frequency of the target even when the Doppler frequency f _{d_TargetDoppler} exceeds the Doppler frequency range −1/(2T _rs2 )≦f _{d_TargetDoppler} <1/(2T _rs2 ). . Here, T _rs2 is the period of transmitting the first chirp signal (or the period of transmitting the second chirp signal) from the second transmitting antenna 106 .

Note that the number of transmitting antennas 106 for switching transmission of radar transmission signals is not limited to two, and may be three or more.

Variation 2 has been described above.

In the radar device according to an embodiment of the present disclosure, the radar transmission section and the radar reception section may be individually arranged at physically separate locations. Also, in the radar receiver according to an embodiment of the present disclosure, the direction estimator and other components may be individually arranged at physically separate locations.

Further, in one embodiment of the present disclosure, for example, the center frequency f _c (q), the number of transmitting antennas Nt, the number of receiving antennas Na, the Doppler multiplexing number N _DM , the values related to the judgment possible conditions (α, N _c, etc.), the phase Values related to rotation (δ, φ ₀ , δ, Δφ ₀ , dpn _{, etc.} ) and numerical values used for frequency are examples, and are not limited to those values.

Although not shown, the radar device according to an embodiment of the present disclosure includes, for example, a CPU (Central Processing Unit), a storage medium such as a ROM (Read Only Memory) storing a control program, and a RAM (Random Access Memory). It has working memory. In this case, the functions of the respective units described above are realized by the CPU executing the control program. However, the hardware configuration of the radar device is not limited to this example. For example, each functional unit of the radar device may be implemented as an IC (Integrated Circuit), which is an integrated circuit. Each functional unit may be individually integrated into one chip, or may be integrated into one chip so as to include a part or all of them.

Various embodiments have been described above with reference to the drawings, but it goes without saying that the present disclosure is not limited to such examples. It is obvious that a person skilled in the art can conceive of various modifications or modifications within the scope described in the claims, and these also belong to the technical scope of the present disclosure. Understood. Also, the components in the above embodiments may be combined arbitrarily without departing from the gist of the disclosure.

In addition, the notation of "... part" in the above-described embodiment may be "... circuit (circuitry)", "... assembly", "... device", "... unit", or , “... module” may be substituted.

In each of the above-described embodiments, the present disclosure has been described as an example configured using hardware, but the present disclosure can also be realized by software in cooperation with hardware.

Also, each functional block used in the description of each of the above embodiments is typically implemented as an LSI, which is an integrated circuit. The integrated circuit may control each functional block used in the description of the above embodiments and may have an input terminal and an output terminal. These may be made into one chip individually, or may be made into one chip so as to include part or all of them. Although LSI is used here, it may also be called IC, system LSI, super LSI, or ultra LSI depending on the degree of integration.

Also, the method of circuit integration is not limited to LSI, and may be implemented using a dedicated circuit or a general-purpose processor and memory. An FPGA (Field Programmable Gate Array) that can be programmed after LSI manufacturing, and a reconfigurable processor (Reconfigurable Processor) that can reconfigure connections or settings of circuit cells inside the LSI may be used.

Furthermore, if an integration technology that replaces the LSI appears due to advances in semiconductor technology or another derived technology, the technology may naturally be used to integrate the functional blocks. Application of biotechnology, etc. is possible.

<Summary of this disclosure>
A radar apparatus according to an embodiment of the present disclosure is configured such that, for each transmission period, a first transmission signal having a first center frequency and a second transmission signal having a second center frequency, which is a center frequency higher than the first center frequency. and a transmitting antenna for transmitting the first transmission signal and the second transmission signal, wherein the second center frequency is (1+1/N _c ) times the first center frequency ( _Nc is an integer representing the number of times each of the first transmission signal and the second transmission signal is transmitted in each transmission period within a predetermined period).

In one embodiment of the present disclosure, the second center frequency is less than 1.25 times the first center frequency.

In one embodiment of the present disclosure, the second center frequency is a frequency lower than (7/6) times the first center frequency.

In one embodiment of the present disclosure, the transmitting antenna alternately transmits the first transmission signal and the second transmission signal in each transmission cycle.

In one embodiment of the present disclosure, the transmitting antenna simultaneously transmits the first transmission signal and the second transmission signal in each transmission period.

In one embodiment of the present disclosure, the transmitting antennas are a plurality of transmitting antennas, among the plurality of transmitting antennas, the number of transmitting antennas that transmit the first transmission signal and the number of transmitting antennas that transmit the second transmission signal The number of transmit antennas may be the same or different by one.

In an embodiment of the present disclosure, a receiving antenna for receiving a first reflected wave signal of the first transmission signal reflected by a target and a second reflected wave signal of the second transmission signal reflected by the target; A first Doppler analysis circuit for estimating a first Doppler frequency from the first reflected wave signal, a second Doppler analysis circuit for estimating a second Doppler frequency from the second reflected wave signal, the first Doppler frequency and the second and a receiving circuit that determines the number of times the Doppler frequency is folded, the determining circuit estimating a first peak position of the first Doppler frequency observed by the first reflected wave signal. and estimating a second peak position of the second Doppler frequency based on the first peak position and the ratio between the first center frequency and the second center frequency; Based on the degree of matching with the third peak position observed by the second reflected wave signal, the number of folding times of the Doppler frequency of the target is determined.

In one embodiment of the present disclosure, the transmitting antenna is a plurality of transmitting antennas, and the transmitting circuit is configured to transmit at least one of the first transmission signal and the second transmission signal transmitted from the plurality of transmitting antennas. , Doppler shift amounts are given at intervals obtained by dividing the Doppler frequency range for which the Doppler frequency folding count is determined into unequal intervals.

In one embodiment of the present disclosure, when the interval of the Doppler shift amount divided into the unequal intervals is Δf _DDM =1/(T _rs (N _t + δ)) (Nt is the number of the plurality of transmitting antennas is an integer greater than or equal to 1, _Trs is a transmission cycle in which the set of the first transmission signal and the second transmission signal is transmitted), and the second center frequency is the first center frequency are frequencies higher than N _c /(N _c -(N _t +δ)) times of .

In an embodiment of the present disclosure, a plurality of first reflected wave signals reflected by the plurality of targets of the first transmission signal and a plurality of second reflected wave signals of the second transmission signal reflected by the plurality of targets a first Doppler analysis circuit for estimating a first Doppler frequency from the plurality of first reflected wave signals; and a second Doppler analysis for estimating a second Doppler frequency from the plurality of second reflected wave signals. and a determination circuit that determines the number of times of folding of the first Doppler frequency and the second Doppler frequency, wherein the determination circuit includes the first Doppler analysis circuit and the second Doppler analysis circuit. Based on the Doppler frequency estimated by a Doppler analysis circuit that separates the first reflected wave signal and the second reflected wave signal, among the Doppler analysis circuits, the interval between peak positions between the plurality of targets and the Doppler shift The number of Doppler frequency folds for each of the plurality of targets is determined based on the distance between the quantities.

In an embodiment of the present disclosure, a plurality of first reflected wave signals reflected by the plurality of targets of the first transmission signal and a plurality of second reflected wave signals of the second transmission signal reflected by the plurality of targets a first Doppler analysis circuit for estimating a first Doppler frequency from the plurality of first reflected wave signals; and a second Doppler analysis for estimating a second Doppler frequency from the plurality of second reflected wave signals. and a determination circuit for determining the number of times of folding of the first Doppler frequency and the second Doppler frequency, wherein the receiving circuit comprises the first Doppler analysis circuit and the second Doppler analysis circuit. Among the Doppler analysis circuits, a direction estimation circuit for estimating a direction based on the Doppler frequency estimated by the Doppler analysis circuit that separates the first reflected wave signal and the second reflected wave signal is further provided.

In an embodiment of the present disclosure, a receiving antenna for receiving a first reflected wave signal of the first transmission signal reflected by a target and a second reflected wave signal of the second transmission signal reflected by the target; A first Doppler analysis circuit for estimating a first Doppler frequency from the first reflected wave signal, a second Doppler analysis circuit for estimating a second Doppler frequency from the second reflected wave signal, the first Doppler frequency and the second a determination circuit that determines the number of Doppler frequency folding times, the receiving antenna includes a first receiving antenna and a second receiving antenna, and the first Doppler analysis circuit includes: processing the first reflected wave signal received by the first receiving antenna in one of the even-numbered and odd-numbered transmission periods, and processing the first reflected wave signal received by the first receiving antenna in one of the even-numbered and odd-numbered transmission periods; The second Doppler analysis circuit processes the second reflected wave signal received by the second receiving antenna in the one transmission period, and processes the second reflected wave signal received by the second receiving antenna in the one transmission period. Processing the second reflected wave signal received by the first receiving antenna in a transmission period.

In an embodiment of the present disclosure, by mixing a signal received by a receiving antenna and a signal received by the receiving antenna using the first transmission signal in one of even-numbered and odd-numbered transmission periods, Outputting a first reflected wave signal in which the first transmission signal is reflected by the target, and using the second transmission signal for the signal received by the reception antenna in the other of the even-numbered and odd-numbered transmission periods a first receiving circuit for outputting a second reflected wave signal in which the second transmission signal is reflected by a target by mixing; The second reflected wave signal is output by mixing using the signal, and the signal received by the receiving antenna is mixed using the first transmission signal in the other transmission period. and a second receiving circuit that outputs the first reflected wave signal.

In one embodiment of the present disclosure, the first transmission signal and the second transmission signal are chirp signals, and the chirp signal of the first center frequency and the chirp signal of the second center frequency are frequency swept bandwidths are identical.

In one embodiment of the present disclosure, the chirp signal with the first center frequency and the chirp signal with the second center frequency have different frequency sweep times.

In one embodiment of the present disclosure, a first receiving antenna receives a first reflected wave signal of the first transmission signal reflected by a target, and a second reception antenna receives a second reflected wave signal of the second transmission signal reflected by the target. a second receiving antenna, a first receiving circuit that processes the first reflected wave signal, and a second receiving circuit that processes the second reflected wave signal; a first transmission circuit that outputs a transmission signal; and a second transmission circuit that outputs the second transmission signal, wherein the transmission antenna includes the first transmission antenna that transmits the first transmission signal and the second transmission antenna a second transmitting antenna that transmits a transmission signal, wherein the first transmitting antenna, the first transmitting circuit, the first receiving antenna, and the first receiving circuit are included in a first chip; The second transmitting antenna, the second transmitting circuit, the second receiving antenna, and the second receiving circuit are included in a second chip.

In one embodiment of the present disclosure, a first receiving antenna that receives a first reflected wave signal of the first transmission signal reflected by a target and a second reflected wave signal of the second transmission signal reflected by the target , a second receiving antenna for receiving the first reflected wave signal and the second reflected wave signal; a first receiving circuit that processes a reflected wave signal and processes the second reflected wave signal received by the first receiving antenna in the other of even-numbered and odd-numbered transmission periods; a second receiving circuit for processing the second reflected wave signal received by the second receiving antenna and processing the first reflected wave signal received by the second receiving antenna in the other transmission cycle; Further, the transmission circuit includes a first transmission circuit that outputs the first transmission signal and a second transmission circuit that outputs the second transmission signal, and the transmission antenna is configured to output the first transmission signal. and a second transmitting antenna for transmitting the second transmission signal, wherein the first transmitting antenna, the first transmitting circuit, the first receiving antenna, the first The receiving circuit is included in a first chip, and the second transmitting antenna, the second transmitting circuit, the second receiving antenna, and the second receiving circuit are included in a second chip.

In one embodiment of the present disclosure, determining the number of times Doppler frequency folds are applied to a first transmission signal having a first center frequency and a second transmission signal having a second center frequency having a center frequency higher than the first center frequency. a transmission circuit that imparts a Doppler shift amount at intervals obtained by dividing a Doppler frequency range to be processed into non-equidistant intervals; and a transmission antenna, wherein the transmission circuit outputs the first transmission signal and the second transmission signal in each transmission period, and the second center frequency is (1+1/ N _c ) frequency higher than twice (N _c is an integer indicating the number of times each of the first transmission signal and the second transmission signal is transmitted in each transmission cycle within a predetermined period), and the unequal When the interval of the Doppler shift amount divided into intervals is Δf _DDM =1/(T _rs (N _t + δ)) (Nt is an integer indicating the number of the plurality of transmitting antennas, δ is an integer of 1 or more where T _rs is the transmission period during which the set of the first transmission signal and the second transmission signal is transmitted), and the second center frequency is N _c /(N _c −(N _{t )} of the first center frequency +δ)) times higher frequency.

The present disclosure is suitable as a radar device that detects a wide-angle range.

Reference Signs List 10, 10a, 10b, 10c radar device 100, 100a, 100b, 100c radar transmitter 101 radar transmission signal generator 102 modulated signal generator 103 VCO
104 signal generation control unit 105 Doppler shift unit 106, 106c transmission antenna 200, 200a, 200b, 200c radar reception unit 201 antenna system processing unit 202 reception antenna 203 reception radio unit 204 mixer unit 205 LPF
206 signal processing unit 207 A/D conversion unit 208 beat frequency analysis unit 209, 217 output switching unit 210 Doppler analysis unit 211 CFAR unit 212 Doppler demultiplexing unit 213, 213c Doppler determination unit 214, 214c direction estimation unit 215 synchronization signal generation unit 216 switching unit 218 peak extracting unit

Claims (18)

a transmission circuit that outputs a first transmission signal with a first center frequency and a second transmission signal with a second center frequency that is higher than the first center frequency in each transmission period;
a transmitting antenna that transmits the first transmission signal and the second transmission signal;
and
The second center frequency is a frequency higher than (1+1/N _c ) times the first center frequency (N _c is a frequency in which each of the first transmission signal and the second transmission signal is the above frequency within a predetermined period of time). an integer indicating the number of transmissions per transmission cycle),
radar equipment. The second center frequency is a frequency lower than 1.25 times the first center frequency.
The radar device according to claim 1. The second center frequency is a frequency lower than (7/6) times the first center frequency.
The radar device according to claim 1. The transmitting antenna alternately transmits the first transmission signal and the second transmission signal in each transmission cycle,
The radar device according to claim 1. the transmitting antenna simultaneously transmits the first transmission signal and the second transmission signal in each transmission period;
The radar device according to claim 1. the transmitting antenna is a plurality of transmitting antennas,
Among the plurality of transmitting antennas, the number of transmitting antennas for transmitting the first transmission signal and the number of transmitting antennas for transmitting the second transmission signal are the same or different by one,
The radar device according to claim 5. a receiving antenna for receiving a first reflected wave signal of the first transmission signal reflected by a target and a second reflected wave signal of the second transmission signal reflected by the target;
a first Doppler analysis circuit for estimating a first Doppler frequency from the first reflected wave signal; a second Doppler analysis circuit for estimating a second Doppler frequency from the second reflected wave signal; and a receiving circuit including a determination circuit that determines the number of times the two Doppler frequencies are folded,
The determination circuit is
estimating a first peak position of the first Doppler frequency observed by the first reflected wave signal;
estimating a second peak position of the second Doppler frequency based on the first peak position and the ratio between the first center frequency and the second center frequency;
Determining the number of folds of the Doppler frequency of the target based on the degree of matching between the second peak position and the third peak position observed by the second reflected wave signal;
The radar device according to claim 1. the transmitting antenna is a plurality of transmitting antennas,
The transmission circuit is configured to distribute Doppler frequency ranges for determination of the number of times of Doppler frequency folding at unequal intervals in at least one of the first transmission signal and the second transmission signal transmitted from the plurality of transmission antennas. Give the Doppler shift amount of the divided interval,
The radar device according to claim 1. The interval of the Doppler shift amount divided into unequal intervals is

where (Nt is an integer indicating the number of the plurality of transmitting antennas, δ is an integer equal to or greater than 1, and _Trs is the transmission cycle in which the set of the first transmission signal and the second transmission signal is transmitted. ),
The second center frequency is less than the first center frequency

is a higher frequency than
The radar device according to claim 8. a receiving antenna for receiving a plurality of first reflected wave signals resulting from reflection of the first transmission signal from the plurality of targets and a plurality of second reflected wave signals resulting from the reflection of the second transmission signal from the plurality of targets;
a first Doppler analysis circuit for estimating a first Doppler frequency from the plurality of first reflected wave signals; a second Doppler analysis circuit for estimating a second Doppler frequency from the plurality of second reflected wave signals; and the first Doppler a receiver circuit including a determination circuit that determines the frequency and the number of times of folding of the second Doppler frequency,
The determination circuit, of the first Doppler analysis circuit and the second Doppler analysis circuit, separates the first reflected wave signal and the second reflected wave signal based on the Doppler frequency estimated by the Doppler analysis circuit, Determining the number of Doppler frequency loopbacks for each of the plurality of targets based on the interval of peak positions between the plurality of targets and the interval of the Doppler shift amount;
A radar device according to claim 9 . a receiving antenna for receiving a plurality of first reflected wave signals resulting from reflection of the first transmission signal from the plurality of targets and a plurality of second reflected wave signals resulting from the reflection of the second transmission signal from the plurality of targets;
a first Doppler analysis circuit for estimating a first Doppler frequency from the plurality of first reflected wave signals; a second Doppler analysis circuit for estimating a second Doppler frequency from the plurality of second reflected wave signals; and the first Doppler a receiver circuit including a determination circuit that determines the frequency and the number of times of folding of the second Doppler frequency,
The receiving circuit, of the first Doppler analysis circuit and the second Doppler analysis circuit, based on the Doppler frequency estimated by the Doppler analysis circuit that separates the first reflected wave signal and the second reflected wave signal, further comprising a direction estimation circuit that performs direction estimation;
A radar device according to claim 9 . a receiving antenna for receiving a first reflected wave signal of the first transmission signal reflected by a target and a second reflected wave signal of the second transmission signal reflected by the target;
a first Doppler analysis circuit for estimating a first Doppler frequency from the first reflected wave signal; a second Doppler analysis circuit for estimating a second Doppler frequency from the second reflected wave signal; and a receiving circuit including a determination circuit that determines the number of times the two Doppler frequencies are folded,
The receiving antennas include a first receiving antenna and a second receiving antenna,
The first Doppler analysis circuit processes the first reflected wave signal received by the first receiving antenna in one of the even-numbered and odd-numbered transmission periods, processing the first reflected wave signal received by the second receiving antenna in a transmission period;
The second Doppler analysis circuit processes the second reflected wave signal received by the second reception antenna in the one transmission period, and processes the second reflected wave signal received by the first reception antenna in the other transmission period. 2 processing the reflected wave signal,
The radar device according to claim 5. a plurality of receive antennas including a first receive antenna and a second receive antenna;
By mixing the signal received by the first receiving antenna with the first transmission signal every first period, a first reflected wave signal of the first transmission signal reflected by the target is output. and mixing the signal received by the first receiving antenna with the second transmission signal in each second period different from the first period, so that the second transmission signal reaches the target. a first receiving circuit that outputs a reflected second reflected wave signal;
outputting the second reflected wave signal by mixing the signal received by the second receiving antenna with the second transmission signal every the first period; and a second receiving circuit that outputs the first reflected wave signal by mixing the signal received by the second receiving antenna with the first transmission signal,
The radar device according to claim 5. the first transmission signal and the second transmission signal are chirp signals;
The chirp signal with the first center frequency and the chirp signal with the second center frequency have the same frequency sweep bandwidth.
The radar device according to claim 1. The frequency sweep time differs between the chirp signal with the first center frequency and the chirp signal with the second center frequency.
15. A radar system according to claim 14. a first receiving antenna that receives a first reflected wave signal that is the first transmission signal reflected by a target;
a second receiving antenna that receives a second reflected wave signal that is the second transmission signal reflected by the target;
a first receiving circuit that processes the first reflected wave signal;
and a second receiving circuit that processes the second reflected wave signal,
The transmission circuit includes a first transmission circuit that outputs the first transmission signal and a second transmission circuit that outputs the second transmission signal,
the transmitting antenna includes a first transmitting antenna that transmits the first transmission signal and a second transmitting antenna that transmits the second transmission signal;
the first transmitting antenna, the first transmitting circuit, the first receiving antenna, and the first receiving circuit are included in a first chip;
The second transmitting antenna, the second transmitting circuit, the second receiving antenna, and the second receiving circuit are included in a second chip,
The radar device according to claim 5. a first receiving antenna for receiving a first reflected wave signal of the first transmission signal reflected by a target and a second reflected wave signal of the second transmission signal reflected by the target;
a second receiving antenna that receives the first reflected wave signal and the second reflected wave signal;
processing the first reflected wave signal received by the first receiving antenna in one of the even-numbered and odd-numbered transmission periods, and processing the first reflected wave signal in the other of the even-numbered and odd-numbered transmission periods; a first receiving circuit that processes the second reflected wave signal received by an antenna;
processing the second reflected wave signal received by the second receiving antenna in the one transmission cycle, and processing the first reflected wave signal received by the second receiving antenna in the other transmission cycle; 2 receiving circuit;
further comprising
The transmission circuit includes a first transmission circuit that outputs the first transmission signal and a second transmission circuit that outputs the second transmission signal,
the transmitting antenna includes a first transmitting antenna that transmits the first transmission signal and a second transmitting antenna that transmits the second transmission signal;
the first transmitting antenna, the first transmitting circuit, the first receiving antenna, and the first receiving circuit are included in a first chip;
The second transmitting antenna, the second transmitting circuit, the second receiving antenna, and the second receiving circuit are included in a second chip,
The radar device according to claim 5. A Doppler frequency range subject to determination of the number of Doppler frequency folding times is added to a first transmission signal having a first center frequency and a second transmission signal having a second center frequency having a center frequency higher than the first center frequency. a transmission circuit that imparts Doppler shift amounts at intervals divided into unequal intervals;
a plurality of transmitting antennas for transmitting the first transmission signal and the second transmission signal to which the Doppler shift amount has been added;
and
The transmission circuit outputs the first transmission signal and the second transmission signal for each transmission cycle,
The second center frequency is a frequency higher than (1+1/ _Nc ) times the first center frequency ( _Nc is a frequency in which each of the first transmission signal and the second transmission signal is the above frequency within a predetermined period of time). an integer indicating the number of transmissions per transmission cycle),
The interval of the Doppler shift amount divided into unequal intervals is

where (Nt is an integer indicating the number of the plurality of transmitting antennas, δ is an integer equal to or greater than 1, and _Trs is the transmission cycle in which the set of the first transmission signal and the second transmission signal is transmitted. ),
The second center frequency is less than the first center frequency

is a higher frequency than
radar equipment.

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