JP7266234B2 - radar equipment - Google Patents

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. Further, in order to improve outdoor safety, there is a demand for the development of a radar device (wide-angle radar device) that detects objects (targets) including pedestrians in a wide-angle range in addition to vehicles.

In addition, as a radar device, in addition to the reception branch, the transmission branch also has a plurality of antenna elements (array antennas), and a configuration that performs beam scanning by signal processing using the transmission and reception array antennas (MIMO (Multiple Input Multiple Output) radar and is also called) has been proposed (see, for example, Non-Patent Document 1).

In MIMO radar, a virtual receiving array antenna (hereinafter referred to as a virtual receiving array) equal to the product of the number of transmitting antenna elements and the number of receiving antenna elements is created by devising the placement of antenna elements in the transmitting and receiving array antennas. Configurable. This has the effect of increasing the effective aperture length of the array antenna with a small number of elements.

In addition to vertical or horizontal one-dimensional scanning, MIMO radar can also be applied to vertical and horizontal two-dimensional beam scanning (see, for example, Patent Document 1 and Non-Patent Document 1). reference).

Japanese Patent Publication No. 2017-534881

P. P. Vaidyanathan, P. Pal, Chun-Yang Chen, "MIMO radar with broadband waveforms: Smearing filter banks and 2D virtual arrays," IEEE Asilomar Conference on Signals, Systems and Computers, pp.188 -192, 2008. 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

One aspect of the present disclosure contributes to providing a radar apparatus capable of increasing the aperture length per antenna element and increasing the aperture length of a virtual reception array.

A radar apparatus according to an aspect of the present disclosure includes a radar transmission circuit that transmits a radar signal from a transmission array antenna, and a radar reception circuit that receives a reflected wave signal of the radar signal reflected by a target from a reception array antenna. one of the transmitting array antenna and the receiving array antenna includes a first antenna group and a second antenna group, and the first antenna group has a phase center of each antenna element in a first axis direction. One or more first antenna elements and one shared antenna element arranged at first intervals along the line, and the second antenna group includes a plurality of second antenna elements and the one and the phase center of each antenna element is arranged in two rows at a second arrangement interval along a second axial direction different from the first axial direction, and included in each of the two rows. The phase centers of the antenna elements have different positions in the second axis direction, and the phase centers of the other of the transmitting array antenna and the receiving array antenna are located at the first arrangement interval along the first axis direction. arranged at a third arrangement interval smaller than the first arrangement interval, and arranged at a fourth arrangement interval larger than the second arrangement interval along the second axial direction. It adopts a configuration including a plurality of third antenna elements arranged every.

A radar apparatus according to an aspect of the present disclosure includes a radar transmission circuit that transmits a radar signal from a transmission array antenna, and a radar reception circuit that receives a reflected wave signal of the radar signal reflected by a target from a reception array antenna. wherein one of the transmit array antenna and the receive array antenna includes a first antenna group and a second antenna group, the first antenna group being one shared antenna element, or each One or more first antenna elements having phase centers of the antenna elements arranged along a first axial direction and the one shared antenna element, and the second antenna group includes a plurality of second antenna elements. and the one shared antenna element, wherein the position of the phase center of each antenna element in a second axis direction different from the first axis direction is different from each other, and at least one phase center of the plurality of second antenna elements and the phase center of the one shared antenna element have the same position in the first axis direction, and are arranged in one or more rows in the second axis direction at every second arrangement interval.

In addition, these generic or specific aspects may be realized by a system, method, integrated circuit, computer program, or recording medium, and any of the system, apparatus, method, integrated circuit, computer program and recording medium may be implemented. may be implemented in any combination.

According to one aspect of the present disclosure, one aspect of the present disclosure can provide a radar apparatus that can increase the aperture length per antenna element and increase the aperture length of a virtual reception array.

Further advantages and advantages of one aspect of the present disclosure will be 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, but not necessarily all to obtain one or more of the same features. No need.

1 is a block diagram showing an example of a configuration of a radar device according to Embodiment 1; FIG. 1 is a block diagram showing an example of a configuration of a radar transmission unit according to Embodiment 1; FIG. A diagram showing an example of a radar transmission signal according to Embodiment 1 A diagram showing an example of a time-division switching operation of transmission antennas by the control unit according to Embodiment 1 4 is a block diagram showing an example of another configuration of the radar transmission signal generator according to Embodiment 1. FIG. 1 is a block diagram showing an example of the configuration of a radar receiver according to Embodiment 1; FIG. A diagram showing an example of the transmission timing of the radar transmission signal and the measurement range of the radar device according to the first embodiment. FIG. 4 is a diagram showing a three-dimensional coordinate system used for explaining the operation of the direction estimation unit according to Embodiment 1; Diagram showing an example of arrangement of transmitting antennas according to Embodiment 1 A diagram showing an example of the arrangement of receiving antennas according to Embodiment 1 A diagram showing an example of arrangement of virtual receiving antennas according to Embodiment 1 A diagram showing an example of the arrangement of transmitting antennas according to Variation 1 of Embodiment 1 A diagram showing an example of arrangement of receiving antennas according to Variation 1 of Embodiment 1 A diagram showing an example of an arrangement of virtual receiving antennas according to Variation 1 of Embodiment 1 FIG. 4 shows an example of the size of an antenna element according to Variation 1 of Embodiment 1; FIG. 10 is a diagram showing an example of a directivity pattern of two-dimensional beams by the virtual receiving array according to Variation 1 of Embodiment 1 and a cross-sectional view along the first axis direction; FIG. 10 is a diagram showing an example of a cross-sectional view along the second axis direction, which is a directivity pattern of two-dimensional beams by the virtual receiving array according to Variation 1 of Embodiment 1; A diagram showing an example of an arrangement of transmitting antennas according to a comparative example A diagram showing an example of an arrangement of virtual receiving antennas according to a comparative example FIG. 10 is a diagram showing an example of a cross-sectional view along the second axis direction of a directivity pattern by a virtual receiving array according to a comparative example; A diagram showing an example of the arrangement of transmitting antennas according to Variation 2 of Embodiment 1 A diagram showing an example of arrangement of receiving antennas according to Variation 2 of Embodiment 1 A diagram showing an example of the arrangement of virtual receiving antennas according to Variation 2 of Embodiment 1 FIG. 10 is a diagram showing an example of the size of an antenna element according to Variation 2 of Embodiment 1; FIG. 10 is a diagram showing an example of a cross-sectional view along the first axis direction, which is a directivity pattern of two-dimensional beams by the virtual receiving array according to Variation 2 of Embodiment 1; FIG. 10 is a diagram showing an example of a cross-sectional view along the second axis direction, which is a directivity pattern of two-dimensional beams by the virtual receiving array according to Variation 2 of Embodiment 1; A diagram showing an example of a directivity pattern by a virtual reception array according to Variation 2 of Embodiment 1 A diagram showing an example of a directivity pattern by a virtual reception array according to Variation 2 of Embodiment 1 A diagram showing an example of arrangement of antenna elements of a transmission array antenna according to Embodiment 2 A diagram showing an example of arrangement of antenna elements of a receiving array antenna according to Embodiment 2 Diagram showing an example of arrangement of virtual reception arrays according to Embodiment 2 The figure which shows an example of the size of the antenna element which concerns on Embodiment 2. FIG. 10 is a diagram showing an example of arrangement of antenna elements of a transmission array antenna according to Variation 1 of Embodiment 2 FIG. 10 is a diagram showing an example of arrangement of antenna elements of a receiving array antenna according to Variation 1 of Embodiment 2; A diagram showing an example of the arrangement of virtual reception arrays according to Variation 1 of Embodiment 2 A diagram showing an example of arrangement of antenna elements of a transmission array antenna according to Variation 2 of Embodiment 2 FIG. 10 is a diagram showing an example of arrangement of antenna elements of a receiving array antenna according to Variation 2 of Embodiment 2; A diagram showing an example of the arrangement of virtual reception arrays according to Variation 2 of Embodiment 2 FIG. 11 shows an example of antenna element sizes 113k and 215k according to Variation 2 of Embodiment 2 A diagram showing an example of a cross-sectional view along the first axis direction of a directivity pattern by a virtual receiving array according to Variation 2 of Embodiment 2. A diagram showing an example of a cross-sectional view along the second axis direction of a directivity pattern by a virtual receiving array according to variation 2 of embodiment 2.

For example, as a radar device, a pulse radar device that repeatedly transmits pulse waves is known. The signal received by the wide-angle pulse radar that detects vehicles/pedestrians in a wide-angle range is a mixture of multiple reflected waves from a target (e.g. vehicle) at a short distance and a target (e.g. pedestrian) at a long distance. signal. Therefore, (1) the radar transmission unit is required to transmit a pulse wave or a pulse-modulated wave having autocorrelation characteristics (hereinafter referred to as low-range sidelobe characteristics) with low range sidelobes, and (2) A radar receiver is required to have a configuration with a wide reception dynamic range.

As the configuration of the wide-angle radar device, there are the following two configurations.

The first configuration uses a directional beam with a narrow angle (a beam width of about several degrees) to scan a pulsed wave or modulated wave mechanically or electronically to transmit a radar wave, thereby achieving a narrow-angle directional beam. In this configuration, a reflected wave is received using a polar beam. In this configuration, the number of scans is increased to obtain high resolution, so the followability to a target moving at high speed is degraded.

In the second configuration, in the receiving branch, an array antenna consisting of multiple antennas (multiple antenna elements) receives the reflected waves, and the arrival of the reflected waves is detected by a signal processing algorithm based on the reception phase difference with respect to the antenna element spacing. This configuration uses a method of estimating angles (Direction of Arrival (DOA) estimation). In this configuration, even if the scanning interval of the transmission beam in the transmission branch is thinned out, the arrival angle can be estimated in the reception branch, so the scanning time can be shortened, and the tracking can be performed as compared with the first configuration. improve sexuality. For example, direction-of-arrival estimation methods include Fourier transform based on matrix operation, Capon method and LP (Linear Prediction) method based on inverse matrix operation, or MUSIC (Multiple Signal Classification) and ESPRIT (Estimation of Signal Parameters) based on eigenvalue operation. via Rotational Invariance Techniques).

In addition, a MIMO radar that performs beam scanning using a plurality of antenna elements in a transmission branch in addition to a reception branch transmits signals multiplexed using time division, frequency division, or code division from a plurality of transmission antenna elements, The signals reflected by the object are received by a plurality of receiving antenna elements, and multiplexed transmission signals are separated and received from each of the received signals.

Furthermore, in MIMO radar, by devising the layout of the antenna elements in the transmission and reception array antennas, it is possible to configure a virtual reception array antenna (virtual reception array) equal to the product of the number of transmission antenna elements and the number of reception antenna elements at maximum. . As a result, it is possible to obtain the channel response indicated by the product of the number of transmitting antenna elements and the number of receiving antenna elements. The angle resolution can be improved by virtually enlarging the length.

Here, the antenna element configuration in MIMO radar is roughly divided into a configuration using one antenna element (hereinafter referred to as a single antenna) and a configuration in which a plurality of antenna elements are sub-arrayed (hereinafter referred to as a sub-array). .

When a single antenna is used, compared with the case of using a sub-array, the antenna has a wider directivity, but the antenna gain is relatively low. Therefore, in order to improve the reception SNR (Signal to Noise Ratio) of the reflected wave signal, in the reception signal processing, for example, more addition processing is performed, or an antenna is configured using a plurality of single antennas. become.

On the other hand, when a subarray is used, compared to the case of using a single antenna, one subarray includes a plurality of antenna elements, so the physical size of the antenna becomes larger, and the main beam direction becomes larger. Antenna gain can be increased. Specifically, the physical size of the subarray is equal to or larger than the wavelength of the radio frequency (carrier frequency) of the transmission signal.

In addition to vertical or horizontal one-dimensional scanning, the MIMO radar can also be applied to vertical and horizontal two-dimensional beam scanning (see, for example, Patent Document 1, Non-Patent Document 1).

However, as in Non-Patent Document 1, in each of the transmitting antenna element and the receiving antenna element, when the antenna elements are arranged at equal intervals of about half a wavelength in the horizontal direction and the vertical direction, the antenna elements are adjacent to each other. Due to physical restrictions, it is difficult to increase the antenna gain by sub-arraying the antenna elements.

On the other hand, the more the antenna spacing is increased by one wavelength or more in order to sub-array the antenna elements, the more grating lobes or side lobe components are generated in the angular direction, increasing the probability of erroneous detection.

In addition, if there are restrictions on the number of antenna elements in the transmission/reception branch (for example, about 4 antenna elements for transmission/4 antenna elements for reception) in order to reduce the size and cost of MIMO radar, more antenna elements can be used. It is difficult to improve the reception SNR of the reflected wave signal by using the MIMO radar, and the vertical and horizontal aperture lengths are restricted in the planar virtual reception array of the MIMO radar.

From the above, when the transmitting antenna elements and the receiving antenna elements are arranged at equal intervals of about half a wavelength in the vertical and horizontal directions, the aperture length per antenna element should be increased because the antenna elements are adjacent to each other. Therefore, it is difficult to increase the gain of the antenna element. On the other hand, the wider the antenna element spacing, the closer the grating lobe is to the main lobe, and the higher the probability of erroneous detection.

(Embodiment 1)
In one aspect of the present disclosure, the antenna elements are sub-arrayed to improve the reception SNR of the reflected wave signal, and the virtual reception arrays are arranged at regular intervals of about half a wavelength to suppress the grating lobe or sidelobe components. According to one aspect of the present disclosure, while increasing the aperture length per antenna element to increase the gain without increasing the probability of false detection, the virtual reception array is arranged at equal intervals, and the aperture length in the virtual reception array can be provided.

Hereinafter, embodiments 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.

Before explaining the arrangement of a plurality of transmitting antennas (transmitting sub-arrays) and a plurality of receiving antennas (receiving sub-arrays), the configuration of the radar apparatus will be described. Specifically, in the transmission branch of the radar device, multiple transmission antennas are switched in a time division manner to transmit different time division multiplexed radar transmission signals, and in the reception branch, each transmission signal is separated and reception processing is performed. The configuration of the MIMO radar to be used will be described. However, the configuration of the radar device is not limited to this. In the transmission branch, different transmission signals that are frequency division multiplexed are transmitted from a plurality of transmission antennas, and in the reception branch, each transmission signal is separated and subjected to reception processing. may be configured. Similarly, the configuration of the radar apparatus may be such that a transmission branch transmits a code-division-multiplexed transmission signal from a plurality of transmission antennas, and a reception branch performs reception processing.

In addition, the embodiment described below is an example, and the present disclosure is not limited to the following embodiment.

[Configuration of radar device 10]
FIG. 1 is a block diagram showing an example configuration of a radar device 10 according to Embodiment 1. As shown in FIG. The radar apparatus 10 includes a radar transmission section (also referred to as transmission branch or radar transmission circuit) 100, a radar reception section (also referred to as reception branch or radar reception circuit) 200, a reference signal generation section (reference signal generation circuit) 300, and a control unit (control circuit) 400 .

The radar transmission unit 100 generates a high-frequency (radio frequency) radar signal (radar transmission signal) based on the reference signal received from the reference signal generation unit 300 . Radar transmission section 100 then switches the plurality of transmission antenna elements #1 to #Nt in a time division manner to transmit radar transmission signals.

The radar receiver 200 receives a reflected wave signal, which is a radar transmission signal reflected by a target (not shown), using a plurality of receiving antenna elements #1 to #Na. The radar receiver 200 performs processing in synchronization with the radar transmitter 100 by performing the following processing operations using the reference signal received from the reference signal generator 300 . The radar receiver 200 performs signal processing on the reflected wave signal received by each receiving antenna element 202, and at least detects the presence or absence of a target or estimates its direction. A target is an object to be detected by the radar device 10, and includes, for example, a vehicle (including two-wheeled, three-wheeled, and four-wheeled vehicles) or a person.

The reference signal generator 300 is connected to each of the radar transmitter 100 and the radar receiver 200 . The reference signal generation section 300 supplies the reference signal to the radar transmission section 100 and the radar reception section 200 to synchronize the processing of the radar transmission section 100 and the radar reception section 200 .

The control unit 400 sets the pulse code generated by the radar transmission unit 100, the phase set in the variable beam control by the radar transmission unit 100, and the level at which the radar transmission unit 100 amplifies the signal for each radar transmission cycle Tr. . The control unit 400 outputs a control signal (code control signal) that instructs the pulse code, a control signal (phase control signal) that instructs the phase, and a control signal (transmission control signal) that instructs the amplification level of the transmission signal. , to the radar transmitter 100 . Further, control section 400 outputs to radar receiving section 200 an output switching signal that instructs the switching timing of transmission sub-arrays #1 to #N in radar transmitting section 100 (radar transmission signal output switching).

[Configuration of radar transmission unit 100]
FIG. 2 is a block diagram showing an example of the configuration of radar transmission section 100 according to Embodiment 1. As shown in FIG. The radar transmission unit 100 includes a radar transmission signal generation unit (radar transmission signal generation circuit) 101, a transmission frequency conversion unit (transmission frequency conversion circuit) 105, a power divider (power distribution circuit) 106, and a transmission amplification unit (transmission amplifier circuit) 107 and a transmission array antenna 108 .

In the following, the configuration of the radar transmission unit 100 using a coded pulse radar is shown as an example, but is not limited to this. For example, radar transmission using frequency modulation of FM-CW (Frequency Modulated Continuous Wave) radar It can be applied to signals as well.

The radar transmission signal generator 101 generates a timing clock (clock signal) by multiplying the reference signal received from the reference signal generator 300 by a predetermined number, and generates a radar transmission signal based on the generated timing clock. Then, the radar transmission signal generating section 101 repeatedly outputs the radar transmission signal at the radar transmission period Tr based on the code control signal from the control section 100 for each predetermined radar transmission period Tr.

A radar transmission signal is represented by y(k _t ,M)=I(k _T ,M)+jQ(k _t ,M). Here, j represents the imaginary unit, k represents the discrete time, and M represents the ordinal number of the radar transmission period. Also, I(k _T ,M) and Q(k _T ,M) are in-phase components (In-Phase components) of the radar transmission signal (k _T ,M) at discrete time k _T in the M-th radar transmission cycle. , and quadrature components, respectively.

Radar transmission signal generation section 101 includes code generation section (code generation circuit) 102 , modulation section (modulation circuit) 103 , and LPF (Low Pass Filter) 104 .

Based on the code control signal for each radar transmission cycle Tr, the code generation unit 102 generates a code a _n (M) (n=1, . . . , L) ( pulse code). For the code a _n (M) generated in the code generating section 102, a pulse code that provides low-range sidelobe characteristics is used. Examples of code sequences include Barer codes, M-sequence codes, and Gold codes. Note that the codes a _n (M) generated by the code generation unit 102 may be the same code or codes containing different codes.

The modulation unit 103 performs pulse modulation (amplitude modulation, ASK (Amplitude Shift Keying), pulse shift keying) or phase modulation (PSK) on the code a _n (M) output from the code generation unit 102. and outputs the modulated signal to the LPF 104 .

LPF 104 outputs signal components below a predetermined band limit in the modulated signal output from modulation section 103 to transmission frequency conversion section 105 as a baseband radar transmission signal.

The transmission frequency converter 105 frequency-converts the baseband radar transmission signal output from the LPF 104 into a radar transmission signal in a predetermined carrier frequency (RF: Radio Frequency) band.

Power divider 106 divides the radio frequency band radar transmission signal output from transmission frequency conversion section 105 into Nt pieces and outputs the divided signals to respective transmission amplification sections 107 .

The transmission amplifying section 107 (107-1 to 107-Nt) amplifies the output radar transmission signal to a predetermined level based on the transmission control signal for each radar transmission period Tr instructed by the control section 400, and outputs the signal. or turn off the transmission output.

The transmit array antenna 108 has Nt transmit antenna elements #1 to #Nt (108-1 to 108-Nt). Each transmission antenna element #1 to #Nt is connected to individual transmission amplifiers 107-1 to 107-Nt, and transmits radar transmission signals output from individual transmission amplifiers 107-1 to 107-Nt. do.

3 is a diagram showing an example of a radar transmission signal according to Embodiment 1. FIG. In each radar transmission period Tr, a pulse code sequence is transmitted during the code transmission section Tw, and the remaining section (Tr-Tw) is a no-signal section. A code length L pulse code sequence is included in the code transmission section Tw. One code includes L sub-pulses. In addition, Nr (=No×L) samples are included in each code transmission interval Tw by performing pulse modulation using No samples per sub-pulse. Nu samples are included in a no-signal period (Tr-Tw) in the radar transmission cycle Tr.

FIG. 4 shows an example of the time division switching operation of each of the transmitting antenna elements #1 to #Nt by the control section 400. In FIG. In FIG. 4, the control unit 400 controls a control signal (code control signal, transmission control signal) to the radar transmission unit 100 . Further, the control unit 400 sets the transmission output period of each transmission sub-array to (Tr×Nb), and performs the switching operation of the transmission output period of all the transmission sub-arrays (Tr×Np)=(Tr×Nb×Nt) Nc times. Repeat control. Further, the radar receiving unit 200, which will be described later, performs positioning processing based on the switching operation of the control unit 400. FIG.

For example, when transmitting a radar transmission signal from transmission antenna element #1, control section 400 causes transmission amplification section 107-1 connected to transmission antenna element #1 to amplify the input signal to a predetermined level. It outputs a transmission control signal instructing to turn off the transmission output to the transmission amplifier sections 107-2 to 107-Nt not connected to the transmission antenna element #1.

Similarly, when transmitting a radar transmission signal from transmission antenna element #2, control section 400 instructs transmission amplification section 107-2 connected to transmission antenna element #2 to amplify the input signal to a predetermined level. , and outputs a transmission control signal instructing the transmission amplifier 107 not connected to the transmission antenna element #2 to turn off the transmission output.

Thereafter, control section 400 sequentially performs similar control on transmitting antenna elements #3 to #Nt. The output switching operation of the radar transmission signal by the control unit 400 has been described above.

[Other Configurations of Radar Transmission Unit 100]
FIG. 5 is a block diagram showing an example of another configuration of radar transmission signal generation section 101 according to Embodiment 1. In FIG. The radar transmitter 100 may include a radar transmission signal generator 101a shown in FIG. 5 instead of the radar transmission signal generator 101. FIG. Radar transmission signal generation section 101a does not have code generation section 102, modulation section 103 and LPF 104 shown in FIG. conversion circuit) 112.

The code storage unit 111 preliminarily stores code sequences generated by the code generation unit 102 shown in FIG. 2, and cyclically reads out the stored code sequences.

The DA conversion unit 112 converts the code sequence (digital signal) output from the code storage unit 111 into an analog baseband signal.

[Configuration of radar receiver 200]
FIG. 6 is a block diagram showing an example of the configuration of radar receiving section 200 according to Embodiment 1. As shown in FIG. The radar receiving unit 200 includes a receiving array antenna 202, Na antenna element system processing units (antenna element system processing circuits) 201 (201-1 to 201-Na), a direction estimation unit (direction estimation circuit) 214, have

The receiving array antenna 202 has Na receiving antenna elements #1 to #Na (202-1 to 202-Na). The Na receiving antenna elements 202-1 to 202-Na receive reflected wave signals, which are radar transmission signals reflected by reflecting objects including measurement targets (objects), and respectively correspond to the received reflected wave signals. It is output as a received signal to the antenna element system processing units 201-1 to 201-Na.

Each antenna element system processing section 201 (201-1 to 201-Na) has a receiving radio section (receiving radio circuit) 203 and a signal processing section (signal processing circuit) 207. FIG. The reception radio unit 203 and the signal processing unit 207 generate a timing clock (reference clock signal) obtained by multiplying the reference signal received from the reference signal generation unit 300 by a predetermined number, and operate based on the generated timing clock to perform radar transmission. Synchronization with the unit 100 is ensured.

The reception radio section 203 has an amplifier (amplification circuit) 204 , a frequency converter (frequency conversion circuit) 205 , and a quadrature detector (quadrature detection circuit) 206 . Specifically, in the z-th receiving radio section 203, the amplifier 204 amplifies the received signal received from the z-th receiving antenna element #z to a predetermined level. where z=1,...,Nr. Next, the frequency converter 205 frequency-converts the received signal in the high frequency band to the baseband band. The quadrature detector 206 then converts the baseband received signal into a baseband received signal including the I signal and the Q signal.

Each signal processing unit 207 includes a first AD conversion unit (AD conversion circuit) 208, a second AD conversion unit (AD conversion circuit) 209, a correlation calculation unit (correlation calculation circuit) 210, and an addition unit (addition circuit ) 211, an output switching unit (output switching circuit) 212, and Nt Doppler analysis units (Doppler analysis circuits) 213-1 to 213-Nt.

First AD converter 208 receives the I signal from quadrature detector 206 . The first AD converter 208 converts the I signal into digital data by sampling the baseband signal including the I signal at discrete times.

Second AD converter 209 receives the Q signal from quadrature detector 206 . The second AD converter 209 converts the Q signal into digital data by sampling the baseband signal including the Q signal at discrete times.

Here, in the sampling of the first AD converter 208 and the second AD converter 209, Ns discrete samples are performed per time Tp (=Tw/L) of one subpulse in the radar transmission signal. That is, the number of oversamples per subpulse is Ns.

FIG. 7 shows an example of the transmission timing of the radar transmission signal and the measurement range of the radar device 10 according to Embodiment 1. FIG. In the following description, using the I signal I _z (k, M) and the Q signal Q _z (k, M), the M-th A baseband received signal at a discrete time k of a radar transmission period Tr[M] is expressed as a complex number signal x _z (k, M)=I _z (k, M)+jQ _z (k, M). In the following description, the discrete time k is based on the start timing of the radar transmission cycle (Tr) (k=1), and the signal processing unit 207 uses k =(N _r +N _u )N _s /N _o are measured periodically. That is, k=1,...,(N _r +N _u )N _s /N _o . where j is the imaginary unit.

式（１）において、アスタリスク（*）は複素共役演算子を表す。 In the z-th signal processing unit 207, the correlation calculation unit 210 receives discrete sample values x _z (k,M) from the first AD conversion unit 208 and the second AD conversion unit 209 for each radar transmission period Tr. and a pulse code a _n (M) of code length L (where z=1, . . . , Na, n=1, . For example, the correlation calculator 210 performs a sliding correlation calculation between the discrete sample value x _z (k,M) and the pulse code a _n (M). For example, the correlation calculation value AC _z (k,M) of the sliding correlation calculation at discrete time k in the M-th radar transmission cycle Tr[M] is calculated based on Equation (1).

In equation (1), the asterisk (*) represents the complex conjugate operator.

_{Correlation calculation} section 210 performs correlation _calculation over a period of k=1, _.

Note that the correlation calculation unit 210 is not limited to performing the correlation calculation for k=1, . . . , (N _r +N _u )N _s /N _o . Depending on the range, the measurement range (ie the range of k) may be limited. By limiting, the amount of calculation processing in the correlation calculator 210 is reduced. For example, correlation calculator 210 may limit the measurement range to k=N _s (L+1), . . . , (N _r +N _u )N _s /N _o −N _s L. In this case, as shown in FIG. 7, the radar device 10 does not perform measurement during the time interval corresponding to the code transmission interval Tw.

With the above-described configuration, even when the radar transmission signal directly reaches the radar receiving section 200, the processing by the correlation calculation section 210 is not performed during the period (at least the period less than τ1) during which the radar transmission signal enters. Therefore, the radar device 10 can perform measurements while excluding the effects of wraparound. Further, when limiting the measurement range (k range) may be applied. As a result, the amount of processing in each component can be reduced, and the power consumption in the radar receiver 200 can be reduced.

In the z-th signal processing unit 207, the adding unit 211, based on the output switching signal output from the control unit 400, calculates the radar transmission cycle continuously transmitted from the ND- _th transmitting antenna element _#ND . Addition (coherent integration) processing is performed using the correlation calculation value AC _z (k,M) received from the correlation calculation unit 210 at each discrete time k in units of Nb periods (Tr×Nb) of Tr. where N _D =1,...,Nt and z=1,...,Na.

ここで、CI_z ^(ND)(k,m)は相関演算値の加算値（以下、相関加算値と呼ぶ）を表し、mは加算部２１１における加算回数の序数を示す１以上の整数である。また、z=1,…,Naである。 Addition (coherent integration) processing over a period (Tr×Nb) is represented by the following equation (2).

Here, CI _z ^(ND) (k, m) represents the added value of the correlation calculation value (hereinafter referred to as the correlation added value), and m is an integer of 1 or more indicating the ordinal number of additions in the adder 211. . Also, z=1,...,Na.

In order to obtain an ideal addition gain, it is a condition that the phase components of the correlation calculation values are uniform within a certain range in the addition interval of the correlation calculation values. In other words, the number of additions is preferably set based on the assumed maximum moving speed of the target to be measured. This is because the higher the assumed maximum moving speed of the target, the larger the amount of variation in the Doppler frequency contained in the reflected wave from the target, and the shorter the time period with high correlation, so Np (= N × Nb) is a small value. This is because the effect of improving the gain by the addition in the adder 211 becomes small.

In the z-th signal processing unit 207, the output switching unit 212, based on the output switching signal output from the control unit 400, sets a plurality of radar transmission cycles Tr continuously transmitted from the _ND transmission antenna element. Alternatively, the addition result CI _z ^(ND) (k,m) for each discrete time k obtained by adding the period Nb times (Tr×Nb) to the _ND -th Doppler analysis unit 213- _ND Switch output. where N _D =1,...,Nt and z=1,...,Na.

ここで、FT_CI_z ^(ND)(k,f_s,w)は、第z番目の信号処理部２０７における第N_D番目のドップラ解析部２１３－Ｎ_Ｄにおける第w番目の出力であり、加算部２１１の第N_D番目の出力に対する、離散時間kでのドップラ周波数f_sΔΦのコヒーレント積分結果を示す。ただし、N_D=1,…,Ntであり、f_s=－Nf+1,…,0,Nfであり、k=1,…,(Nr+Nu)Ns/Noであり、wは自然数であり、ΔΦは位相回転単位であり、jは虚数単位であり、z=1,…,Naである。 Each signal processing section 207 has Nt Doppler analysis sections 213-1 to 213-Nt, the same number as the transmission antenna elements #1 to #Nt. The Doppler analysis unit 213 (213-1 to 213-Nt) outputs CI _z ^(ND) ₍ k, N _C (w−1)+ 1) ∼ CI _z ^(ND) (k, N _C ×w) is used as one unit, and coherent integration is performed with discrete time k timing aligned. For example, the Doppler analysis unit 213 calculates phase variations Φ(f _s )=2πf _s (T _r ×N _b ) ΔΦ corresponding to 2Nf different Doppler frequencies f _s ΔΦ as shown in the following equation (3): After correction, coherent integration is performed.

Here, FT_CI _z ^(ND) (k, f _s , w) is the w-th output of the ND _- th Doppler analysis unit 213- _ND in the z-th signal processing unit 207, and the addition unit 21 shows coherent integration results of Doppler frequency f _s ΔΦ at discrete time k for the N _D -th output of 211 . where N _D =1,…,Nt, f _s =−Nf+1,…,0,Nf, k=1,…,(Nr+Nu)Ns/No, and w is a natural number. , where ΔΦ is the phase rotation unit, j is the imaginary unit, and z=1,...,Na.

, FT_CI _z ^(ND) (k, -Nf ₊ 1, w), ^{. ND)} (k, Nf−1, w) is obtained for each Nb×Nc period (Tr×Nb×Nc) of the radar transmission period Tr.

When ΔΦ=1/N _c , the above-described processing of the Doppler analysis unit 213 performs discrete Fourier processing on the output of the addition unit 211 at the sampling interval T _m =(Tr×N _p ) and the sampling frequency f _m =1/T _m . It is equivalent to transform (DFT) processing.

Also, by setting Nf to a power of 2, the Doppler analysis unit 213 can apply Fast Fourier Transform (FFT) processing, and can reduce the amount of arithmetic processing. In addition, when _Nf > ^Nc , the Doppler analysis unit 213 similarly performs FFT processing can be applied to , and the amount of arithmetic processing can be reduced.

Further, in the Doppler analysis unit 213, instead of the FFT processing, a processing of sequentially calculating the sum of products shown in the above equation (3) may be performed. That ^is , the Doppler analysis unit 213 _calculates f Coefficients exp[-j2πf _s T _r N _b qΔΦ] corresponding to _s =−Nf+1, . where q=0,...,N _c -1.

In the following description, similar processing is performed in each of the signal processing unit 207 of the first antenna element system processing unit 201-1 to the signal processing unit 207 of the Na-th antenna system processing unit 201-Na. The obtained w-th output FT_CI _z ⁽¹⁾ (k, f _s , w), …, FT_CI _z ^(Na) (k, f _s , w) is expressed by the following formula (4) (or formula (5 )) as a virtual received array correlation vector h(k,f _s ,w).

The virtual receive array correlation vector h(k, f _s , w) has Nt×Na elements, which is the product of the number Nt of transmit antenna elements #1 to #Nt and the number Na of receive antenna elements #1 to #Na. including. The virtual receiving array correlation vector h(k, f _s , w) is used in the explanation of the process of estimating the direction based on the phase difference between the receiving antenna elements #1 to #Na for the reflected wave signal from the target, which will be described later. use. where z=1,...,Na and N _D =1,...,Nt.

In the above equations (4) and (5), the phase rotation for each Doppler frequency (f _s ΔΦ) caused by the transmission time difference from each transmission sub-array is corrected. That is, with the first transmission sub-array (N _D =1) as a reference, the received signal FT_CI _z ^(Na) (k, f _s , w) of the Doppler frequency (f _s ΔΦ) component from the N _D -th transmission sub-array is is multiplied by exp[-j2πf _s ΔΦ(N _D -1)T _r N _b ].

The processing in each component of the signal processing unit 207 has been described above.

The direction estimation unit 214 performs the w-th Doppler analysis output from the signal processing unit 207 of the first antenna element system processing unit 201-1 to the signal processing unit 207 of the Na-th antenna element system processing unit 201-Na. For the virtual reception array correlation vector h(k,f _s ,w) of the unit 213, the phase shift deviation between the transmission array antennas 108 and the reception array antenna 202 and By multiplying the array correction value h _cal[b] for correcting the amplitude deviation, the virtual reception array correlation vector h _{_after_cal} (k, f _s , w) corrected for the inter-antenna deviation is calculated. Note that b=1,...,(Nt×Na).

The virtual reception array correlation vector _{h_after_cal} (k,f _s ,w) corrected for the inter-antenna deviation is a column vector consisting of Na×Nr elements. Below, each element of the virtual received array correlation vector _{h_after_cal} (k, _fs ,w) is denoted by _h1 (k,fs,w),...,hNa _×Nr (k,fs,w), It is used for explaining the direction estimation processing.

Next, the direction estimation unit 214 uses the virtual reception array correlation vector h _{_after_cal} (k, f _s , w) to estimate the direction of arrival of the reflected wave signal based on the phase difference of the reflected wave signal between the receiving antennas 202. I do.

The direction estimating unit 214 calculates a spatial profile by changing the azimuth direction θ in the direction estimation evaluation function value P _H (θ, k, fs, w) within a predetermined angle range, and increases the maximum peak of the calculated spatial profile. A predetermined number of samples are sequentially extracted, and the azimuth direction of the maximum peak is used as an estimated value of the direction of arrival.

Note that the evaluation function value P _H (θ, k, fs, w) has various values depending on the direction-of-arrival estimation algorithm. For example, an estimation method using an array antenna disclosed in Non-Patent Document 2 may be used.

For example, the beamformer method can be expressed as in Equations (7) and (8) below.

ここでfloor(x)は、実数xを超えない最大の整数値を返す関数である。 where the superscript H is the Hermitian transpose operator. _In addition, a _H (θ _u ) indicates the direction vector _of the virtual receiving array for the incoming wave in the azimuth direction θ _u . It is. For example, θ _u is set as follows.

where floor(x) is a function that returns the largest integer value that does not exceed the real number x.

It should be noted that methods such as Capon and MUSIC can also be applied in place of the beamformer method.

FIG. 8 shows a three-dimensional coordinate system used for explaining the operation of direction estimation section 214 according to the first embodiment. A case in which estimation processing is performed in two-dimensional directions by applying the processing of the direction estimation unit 214 to the three-dimensional coordinate system shown in FIG. 8 will be described below.

In FIG. 8, the position vector of the target _PT with respect to the origin O is defined as _rPT . In FIG. 8, the projection point obtained by projecting the position vector r _PT of the target _PT onto the XZ plane is _PT '. In this case, the azimuth angle θ is defined as the angle between the straight line OP _T ′ and the Z axis (θ>0 if the X coordinate of the target P _T is positive). Also, the elevation angle φ is defined as the angle of a line connecting the target P _T , the origin O and the projected point P _T ' in the plane containing the target P _T , the origin O and the projected point P _T ' (object φ>0 if the Y coordinate of the target P _T is positive). In the following description, an example of arranging the transmitting array antenna 108 and the receiving array antenna 202 in the XY plane will be described.

The position vector of the n _va -th antenna element in the virtual reception array with reference to the origin O is denoted by Sn _va . where n _va =1,..., Nt×Na.

The position vector _S1 of the first (n _va =1) antenna element in the virtual reception array is determined based on the positional relationship between the physical position of the first reception antenna element Rx#1 and the origin O. be. _Position vectors S ₂ , _. is determined while maintaining the relative arrangement of the virtual receiving array determined from the element spacing of . Note that the origin O may coincide with the physical position of the first receiving antenna element Rx#1.

When the radar receiver 200 receives a reflected wave from a target _PT existing in the far field, the received signal at the second antenna element is based on the received signal at the first antenna element of the virtual reception array. The phase difference d(r _PT ,2,1) of the received signal is given by Equation (9) below. where <x,y> is the inner product operator of vector x and vector y.

The position vector of the second antenna element based on the position vector of the first antenna element of the virtual reception array is represented by the following equation (10) as an inter-element vector D(2,1).

Similarly, when the radar receiving unit 200 receives a reflected wave from a target _PT existing in the far field, the received signal at the n _va ^(r) th antenna element of the virtual reception array is used as a reference, and the The phase difference d(r _PT , n _va ^{(t) ,} n _va ^(r) ) of the received signal at the n va (t)-th antenna element is given by Equation (11) _below . where n _va ^(r) = 1,..., Nt x Na and n _va ^(t) = 1,..., Nt x Na.

Note that the position vector of the n _va ^{(t)-th antenna element based on the position vector of the n va (r} ₎ ^-th antenna element of the virtual reception array is the inter-element vector D(n _va ^(t) , n _va ^(r) ) in the following equation (12).

As shown in the above equations (11) and (12), at the n _va ^(t) -th antenna element with reference to the received signal at the n _va ^(r) -th antenna element of the virtual reception array The phase difference d(r _PT , n _va ^(t) , n _va ^(r) ) of the received signal is a unit vector (r _PT /|r _PT |) indicating the direction of the target P _T existing in the far field and It depends on the inter-element vector D(n _va ^(t) , n _va ^(r) ).

Also, when the virtual receiving array exists on the same plane, the inter-element vector D(n _va ^(t) , n _va ^(r) ) exists on the same plane. The direction estimating unit 214 uses all or part of such inter-element vectors to configure a virtual plane array antenna assuming that antenna elements are virtually present at the positions indicated by the inter-element vectors. Perform direction estimation processing in . That is, direction estimating section 214 performs direction-of-arrival estimation processing using a plurality of virtual antennas interpolated by interpolation processing for the antenna elements forming the virtual reception array.

In addition, when the virtual antenna elements overlap, the direction estimation unit 214 may preliminarily select one antenna element among the overlapping antenna elements. Alternatively, the direction estimator 214 may perform averaging processing using received signals from all overlapping virtual antenna elements.

Two-dimensional direction estimation processing using the beamformer method when a virtual plane array antenna is configured using N _q inter-element vector groups will be described below.

Here, the nq-th inter-element vector constituting the virtual plane array antenna is expressed as D(n _va(nq) ^(t) , n _va(nq) ^(r) ). where nq=1,..., _Nq .

The direction estimation unit 214 uses h ₁ (k, fs, w), ..., h _{Na × N} (k, fs, w), which are the elements of the virtual received array correlation vector _{h_after_cal} (k, fs, w). Then, the virtual plane array antenna element correlation vector h _VA (k, fs, w) shown in the following equation (13) is generated.

The virtual surface arrangement array direction vector a _VA (θu, φv) is given by the following equation (14).

When the virtual receiving array exists in the XY plane, the relationship between the unit vector (r _PT /|r _PT |) indicating the direction of the target P _T and the azimuth angle θ and elevation angle φ is given by the following equation (15). show.

The direction estimating unit 214 uses the above equation (15) to determine the unit vector (r _PT /|r _PT |) for each of the angular directions θu and φv for calculating the vertical and horizontal two-dimensional spatial profiles. calculate.

Further, the direction estimation unit 214 uses the virtual plane array antenna element correlation vector h _VA (k, fs, w) and the virtual plane array antenna element correlation vector a _VA (θu, φv) to calculate horizontal and vertical directions. performs two-dimensional direction estimation processing.

For example, in two-dimensional direction estimation processing using the beamformer method, using the virtual plane array antenna correlation vector h _VA (k, fs, w) and the virtual plane array antenna direction vector a _VA (θu, φv), Calculate the two-dimensional spatial profile in the vertical and horizontal directions using the two-dimensional direction estimation evaluation function shown in the following equation (16), and the azimuth and elevation directions that give the maximum value or local maximum value of the two-dimensional spatial profile be the direction-of-arrival estimate.

Note that the direction estimator 214 uses the virtual plane array antenna correlation vector h _VA (k, fs, w) and the virtual plane array antenna direction vector a _VA (θu, φv) other than the beamformer method to obtain the Capon A high-resolution direction-of-arrival estimation algorithm such as the MUSIC method or the MUSIC method may be applied. As a result, although the amount of calculation increases, the angular resolution can be improved.

ここで、Twは符号送信区間を表し、Lはパルス符号長を表し、C₀は光速度を表す。 Note that the discrete time k described above may be converted to distance information and output. When converting the discrete time k into the distance information R(k), the following equation (17) may be used.

Here, Tw represents the code transmission period, L represents the pulse code length, and _C0 represents the speed of light.

ここで、λは送信周波数変換部１０５から出力されるRF信号のキャリア周波数の波長である。 Also, the Doppler frequency information may be converted into a relative velocity component and output. When converting the Doppler frequency fsΔΦ into the relative velocity component v _d (f _s ), the following equation (18) can be used.

Here, λ is the wavelength of the carrier frequency of the RF signal output from transmission frequency converter 105 .

[Antenna Element Arrangement in Radar Device 10]
Arrangement of Nt transmitting antenna elements Tx#1 to #Nt of transmitting array antenna 108 and Na receiving antenna elements Rx#1 to #Na of receiving array antenna 202 of radar apparatus 10 having the above configuration will be described.

Each of the Nt transmitting antenna elements #1 to #Nt and the Na receiving antenna elements Rx#1 to #Na are arranged according to a certain rule in the horizontal and vertical directions. Note that the following arrangement of transmitting antennas and arrangement of receiving antennas are not limited to transmitting antennas and receiving antennas, respectively. In other words, even if the placement of the transmitting antennas and the placement of the receiving antennas are exchanged, a similar virtual receiving array can be obtained. Therefore, the placement of the transmitting antennas and the placement of the receiving antennas may be interchanged. Also, the arrangement of the transmitting antennas and the arrangement of the receiving antennas may be horizontally reversed, vertically reversed, or both may be rotated.

9A and 9B show the arrangement of transmitting antennas and the arrangement of receiving antennas according to Embodiment 1, respectively. 9C shows an example of the arrangement of virtual receiving antennas according to Embodiment 1. FIG. Here, the coordinates in FIG. 9 indicate the phase centers of the antenna elements.

The first axis uses the first spacing _dH as a basic unit, and the second axis uses the second spacing _dV as a basic unit, and the antenna elements are arranged at the positions of the coordinates indicated by integral multiples of the basic units. do. In one example, with reference to the wavelength used in the radar transmission signal, for example, the first interval d _H and the second interval d _V are, for example, 0.3 wavelength or more and 2 wavelengths or less, and about half a wavelength, or equal to half a wavelength. Here, the first axis and the second axis may be on the XY plane shown in FIG. 8, or may be arranged so as to be orthogonal to each other.

The transmitting antenna elements Tx#1 to #Nt shown in FIG. 9A include a first antenna group G1 and a second antenna group G2. The first antenna group G1 includes p _t1 antenna elements (at least one first antenna element). The second antenna group G2 includes p _t2 antenna elements (a plurality of second antenna elements).

ここで、iは１からp_t1までの整数である。式（１９）によって、第１のアンテナ群Ｇ１は、p_r1間隔で、アンテナ素子が配置されることがわかる。 Assuming that the coordinates of the phase center indicated by the white circle in FIG. 9A of the i-th antenna element of the first antenna group G1 are _Tx1i , _Tx1i is expressed by the following equation (19).

where i is an integer from 1 to p _t1 . It can be seen from equation (19) that the antenna elements are arranged at intervals of p _r1 in the first antenna group G1.

ここで、jは１からp_t2までの整数である。式（２０）より、第２のアンテナ群Ｇ２は、第１軸方向にp_tHシフトして、第２軸方向にジグザグ（zigzag）状にアンテナ素子が配置されることがわかる。 As for the second antenna group G2, if the coordinates of the phase center indicated by the white circle in FIG. 9A of the j-th antenna element are Tx2 _j , Tx2 _j is expressed by the following equation (20).

where j is an integer from 1 to p _t2 . From equation (20), it can be seen that the second antenna group G2 is shifted p _tH in the direction of the first axis, and the antenna elements are arranged in a zigzag pattern in the direction of the second axis.

As will be described later, _xc and _yc are values indicating the numbers of antenna elements shared by the first antenna group G1 and the second antenna group G2. For example, in FIG. 9A, x _c =1 and y _c =1 since the first antenna element of the first antenna group G1 and the first antenna element of the second antenna group G2 are shared.

The second antenna group G2 is arranged with a second interval in the direction of the second axis and is shifted by x _s in the direction of the first axis. Since the antenna elements are not concentrated in the second axis direction, it is possible to increase the antenna gain by increasing the aperture length to such an extent that the antenna elements are sub-arrayed so as not to physically interfere with adjacent antenna elements.

即ち、送信アンテナ素子Ｔｘ＃１～＃Ｎｔの第１のアンテナ群Ｇ１の第x_c番目のアンテナ素子と第２のアンテナ群Ｇ２の第y_c番目のアンテナ素子とは共通のアンテナ素子であり、Tx1_xc=Tx2_ycとなる。つまり、第１のアンテナ群Ｇ１の第x_cのアンテナ素子（図９Ａではx_c＝1）と第２のアンテナ群Ｇ２の第y_cのアンテナ素子（図９Ａではy_c＝1）とが共有される形で、第１のアンテナ群Ｇ１と第２のアンテナ群Ｇ２とが交差する。したがって、送信アンテナ素子＃１～＃Ｎｔの総数Ntとp_t1とp_t2との間には、Nt=p_t1+p_t2-1の関係が成立する。 From equations (19) and (20) above, it can be seen that _xc and _yc represent the positional relationship of the antenna elements shared by the first antenna group G1 and the second antenna group G2. Specifically, the following equation (21) is derived from the above equations (19) and (20).

That is, the x _c -th antenna element of the first antenna group G1 of the transmitting antenna elements Tx#1 to #Nt and the y _c-th antenna element of the second antenna group G2 are common antenna elements, Tx1 _xc =Tx2 _yc . That is, the x _c -th antenna element (x _c =1 in FIG. 9A) of the first antenna group G1 and the y _c -th antenna element (y _c =1 in FIG. 9A) of the second antenna group G2 share The first antenna group G1 and the second antenna group G2 intersect. Therefore, the relationship of Nt=p _t1 +p _t2 −1 is established between the total number Nt of transmitting antenna elements #1 to #Nt and p _t1 and p _t2 .

As an example, Tx#1 in FIG. 9A will be described. For the coordinate Tx1 _i=1 of the phase center of the first antenna element of the first antenna group G1, the following _equation ( 19-1) is obtained.

Next, for the coordinate Tx2 _j=1 of the phase center of the first antenna element of the second antenna group G2, substitute x _c =1, y _c =1, j=1 into the above equation (20). By doing so, the following equation (20-1) is obtained.

Therefore, the coordinate Tx1i ₌₁ of the phase center of the first antenna element of the first antenna group G1 and the coordinate _Tx2j=1 of the phase center of the first antenna element of the second antenna group G2 are: It is equal to the coordinate of the phase center of the transmitting antenna element Tx#1.

Similarly, the coordinate Tx2 _j=2 of the phase center of the second antenna element of the second antenna group is
By substituting x _c =1, y _c =1, j=2 into the above equation (20), the following equation (20-2) can be obtained.

Here, when the shift amount _xs of the second antenna group G2 in the first axial direction is 1, it can be expressed as the following equation (20-3).

ここで、iは１からp_r1までの整数、jは１からp_r2までの整数である。受信アンテナ素子＃１～＃Ｎａの総数Naとp_r1とp_r2との間には、Na=p_r1×p_r2の関係が成立する。 Let Rx1 _ij be the coordinates of the phase center of the _j -th row and i-th column of the receiving antenna elements Rx#1 to #Na (a plurality of third antenna elements) shown in FIG. , is represented by the following equation (22).

Here, i is an integer from 1 to p _r1 and j is an integer from 1 to p _r2 . The relationship Na=p _r1 ×p _r2 is established between the total number Na of the receiving antenna elements #1 to #Na and p _r1 and p _r2 .

The constants in the above equations (19) to (22) are, respectively, (x _t0 , y _t0 ) the origin coordinates of the transmitting antenna element group, (x _r0 , y _r0 ) the origin coordinates of the receiving antenna group, p _t1 is the number of transmitting antennas arranged in the first axial direction (p _t1 ≧1), p _t2 is the number of transmitting antennas arranged in the second axial direction (p _t2 >1), and p _r1 is the number of receiving antennas arranged in the first axial direction (first number of columns) (p _r1 > 1), p _r2 is the number of receiving antennas arranged in the second axis direction (p _r2 ≥ 1), x _c is the repeating point of the second antenna group of transmitting antennas (the first axis of the shared antenna element position in the direction) (1≦x _c ≦ p _t1 ), y _c is the repeat point of the first antenna group G1 of the transmitting antennas (1≦y _c ≦ p _t2 ), x _s is the transmitting antenna second antenna group The amount of shift of G2 in the direction of the first axis (1≦x _s <p _r1 ), all integers. Note that p _r1 is equal to the antenna element spacing of the first antenna group G1 of the transmitting antennas.

A virtual receive array formed by the transmit and receive antennas shown in FIGS. 9A and 9B is configured as shown in FIG. 9C. The total number of virtual antenna elements in the virtual receiving array is Nt×Na. A virtual receiving array in which p _t1 ×p _r1 virtual antenna elements are continuously arranged in the direction of the first axis is arranged in p _r2 rows at regular intervals in the direction of the second axis. In addition, virtual receiving arrays in which p _t2 ×p _r2 virtual antenna elements are continuously arranged in the direction of the second axis are arranged in p _r1 −1 rows at regular intervals in the direction of the first axis.

In the antenna arrangement according to Embodiment 1 shown in FIG. 9A, the antenna elements Tx#1 and Tx#p _t1 +1 to Tx#Nt of the second antenna group G2 of the transmitting array antenna 108a are arranged on the first axis of the phase center. They are arranged in a zigzag pattern so that the coordinates are x _t0 and x _t0 +p _tH . The phase centers of the antenna elements Tx#1 and Tx#p _t1 +1 to Tx#Nt of the second antenna group G2 are not evenly spaced at the second spacing _dV . However, in the virtual receive array, the phase centers of the virtual antenna elements can be equally spaced by a second spacing _dV . Therefore, the width of the beam formed by the virtual receiving array, that is, the resolution, depends on the maximum aperture length in the first and second axial directions of the virtual receiving array.

<Variation 1 of Embodiment 1>
FIG. 10A shows an example of arrangement of transmitting antenna elements Tx#1 to #Nt according to Variation 1 of Embodiment 1. FIG. FIG. 10B shows an example of arrangement of receiving antenna elements Rx#1 to #Na according to Variation 1 of Embodiment 1. FIG. 10C shows an example of the arrangement of virtual reception antennas according to Variation 1 of Embodiment 1. FIG.

In the example shown in FIGS. 10A and 10B, the constants in the above equations (19) to (22) are respectively (x _t0 ,y _t0 )=(1,1), (x _r0 ,y _r0 )=(1,1), p _t1 =1, p _t2 =4, p _r1 =8, p _r2 =1, x _c =1, y _c =1, x _s =1. Also, the first axis and the second axis are orthogonal to each other.

In FIG. 10A, the total number Nt of transmitting antenna elements #1 to #Nt is 4, and the respective transmitting antenna elements are represented by Tx#1 to Tx#4. The first antenna group G1 includes Tx#1 (at least one first antenna element). The second antenna group G2 includes Tx#1 to Tx#4 (a plurality of second antenna elements). In FIG. 10B, the total number Na of receiving antenna elements #1 to #Na (a plurality of third antenna elements) is 8, and the respective receiving antenna elements are represented by Rx#1 to Rx#8.

The features of the antenna element arrangement shown in FIGS. 10A and 10B will be described below.

(1) Aperture Length of Antenna Element FIG. 11 shows an example of the size of an antenna element according to variation 1 of the first embodiment. For the arrangement of antenna elements shown in FIGS. 10A and 10B, the size of the antenna elements can be defined as shown in FIG. 11, for example. Here, the antenna element sizes 113c and 215c are sizes that do not interfere with adjacent antenna elements.

As shown in FIG. 11, the antenna elements of the transmission array antenna 108c are arranged in a _zigzag pattern in the direction of the second axis. is formed with an opening length of 2× _dV or less. Since the antenna elements of the receiving array antenna 202c are arranged linearly in the direction of the first axis, they are formed with an aperture length of d _H or less in the direction of the first axis, and there are no adjacent antenna elements in the direction of the second axis. , can be formed with an arbitrary opening length (4×d _V in the example shown in FIG. 11).

When the antenna elements of the transmission array antenna 108c are linearly arranged at equal intervals at the basic intervals d _H and d _V in the first axis direction and the second axis direction, respectively, the size of the antenna elements of the transmission array antenna is the second d _V in the axial direction. In contrast, in the configuration of the present disclosure, for example, as shown in FIG. 11, the transmitting array antenna 108c is arranged in two rows (zigzag pattern) in the second axis direction, and the receiving array antenna 202c is arranged in the second They are arranged in one row (linearly) in one axial direction. With this configuration, the antenna element size 113c of the transmitting array antenna 108c can be increased to _2dV in the second axis direction, and the antenna element size 215c of the receiving array antenna 202c can be increased to _4dV in the second axis direction. Due to the increased size of the antenna elements, high antenna gain can be obtained in the configuration of the present disclosure.

Antenna elements may be configured using subarray antenna elements, and side lobes may be suppressed by applying array weights to the subarray antennas.

(2) Beam Pattern Formed by Virtual Reception Array FIG. 12A shows an example of a two-dimensional beam directivity pattern of the virtual reception array according to Variation 1 of Embodiment 1, which is a cross-sectional view along the first axis direction. show. 12B shows an example of a cross-sectional view of a two-dimensional beam directivity pattern of the virtual receiving array according to Variation 1 of Embodiment 1 along the second axis direction. FIG.

Specifically, in the two-dimensional beam pattern formed by the beamformer method using the virtual receive array shown in FIG. 10C, FIG. Figure shows. In the same beam pattern, FIG. 12B shows a cross-sectional view along the second axis direction at 0 degree in the first axis direction. 12A and 12B show the case of d _H =0.5 wavelength and d _V =0.6 wavelength.

As shown in FIG. 10C, the virtual receive array has an aperture length of 8×d _H in the first axis direction, an aperture length of 3×d _V in the second axis direction, and evenly spaced virtual antenna elements. are placed. Thereby, a grating-free beam can be formed as shown in FIGS. 12A and 12B.

<Comparative example>
For comparison with Variation 1 of Embodiment 1, a case where four transmitting antenna elements are arranged side by side in the second axis direction in a comparative example will be described. FIG. 13 shows an example of arrangement of transmitting antenna elements according to a comparative example. FIG. 14 shows an example of arrangement of virtual antenna elements according to a comparative example. FIG. 15 shows an example of a cross-sectional view along the second axis direction of the directivity pattern of the virtual receiving array according to the comparative example.

For example, when the size of the antenna element of the transmitting antenna is increased, as shown in FIG. 13, the transmitting antenna is spaced apart by 2×d _V or more in the second axis direction so as not to interfere with adjacent antenna elements. placed.

If the receive antennas are arranged as shown in FIG. 10B, the virtual receive array will be arranged as shown in FIG. As a result, the virtual receiving arrays are also arranged at intervals of 2× _dV or more in the second axis direction, which is coarser than in FIG. 10C. In addition, FIG. 10C is arranged at intervals of 1 _dV in the second axis direction. The beams received by the virtual receive array shown in FIG. 14 contain grating lobes, as indicated by the dashed lines in FIG. 15, increasing the probability of false positives.

<Variation 2 of Embodiment 1>
Variation 2 of Embodiment 1 describes an antenna arrangement that can obtain a higher resolution with the same number of elements in the virtual receiving array as Variation 1, and a direction-of-arrival estimation method using that antenna arrangement.

FIG. 16A shows an example of arrangement of elements Tx#1 to #Nt of the transmitting antenna according to Variation 2 of Embodiment 1. FIG. 16B shows an example of arrangement of elements Rx#1 to #Na of the receiving antenna according to Variation 2 of Embodiment 1. FIG. 16C shows an example of the arrangement of virtual reception antennas according to Variation 2 of Embodiment 1. FIG. Note that the number of elements of the virtual receiving antenna is 32, which is the same as variation 1.

In one example shown in FIGS. 16A and 16B, the constants in the above equations (19)-(22) are respectively (x _t0 ,y _t0 )=(1,1), (x _r0 ,y _r0 ) =(1,1), p _t1 =4, p _t2 =5, p _r1 =2, p _r2 =2, x _c =2, y _c =2, x _s =1. The first axis and the second axis are orthogonal to each other.

In FIG. 16A, the total number of antenna elements Nt of the transmission array antenna 108e is 8, and the antenna elements of the transmission array antenna 108e are denoted by Tx#1 to Tx#8. The first antenna group G1 includes Tx#1 to Tx#4 (at least one first antenna element). A second antenna group G2 includes Tx#5, Tx#2, and Tx#6 to Tx#8 (a plurality of second antenna elements). In FIG. 16B, the total number Na of antenna elements (a plurality of third antenna elements) of the receiving array antenna 202e is 4, and the antenna elements of the receiving array antenna 202e are represented by Rx#1 to Rx#4.

The antenna arrangement shown in FIGS. 16A and 16B will be described below.

(1) Aperture Length of Antenna Element FIG. 17 shows an example of sizes 113f and 215f of antenna elements according to variation 2 of the first embodiment. In order to obtain the virtual receive array shown in FIG. 16C, that is, in _{FIG .} Thus, the antenna elements are arranged as shown in FIGS. 16A and 16B.

For the antenna arrangements shown in FIGS. 16A and 16B, the antenna element sizes 113, 215 can be defined, for example, as shown in FIG. Here, the antenna element sizes 113f and 215f are sizes that do not interfere with adjacent antenna elements.

The antenna elements of the transmission array antenna 108f are formed with an aperture length of d _H or less in the first axis direction and an aperture length of 2×d _V or less in the second axis direction. The antenna elements of the receiving array antenna 202f are formed with an aperture length of d _H or less in the first axis direction and an aperture length of 5×d _V or less in the second axis direction.

When the antenna elements of the transmitting array antenna 108f are arranged in the first axis direction and the second axis direction at 1×d _H intervals and 1×d _V intervals, respectively, in one column and one row (linearly), The size of the antenna element cannot be greater than d _H and d _V in the first and second axis directions, respectively. On the other hand, as shown in FIG. 17, the antenna elements of the transmitting array antenna 108 and the receiving array antenna 202f are sized from _dH and _dV in the first axis direction and the second axis direction, respectively. can be expanded to be large, a high antenna gain can be obtained.

The antenna elements shown in FIG. 17 may be configured using subarray antennas, and side lobes may be suppressed by applying array weights to the subarray antennas. That is, the antenna elements in FIG. 17 are replaced with subarray antennas, and the subarray antennas are configured using a plurality of antenna elements.

(2) Beam Pattern Formed by Virtual Receiving Array FIG. 18A shows an example of a cross-sectional view along the first axis direction of a two-dimensional beam directivity pattern by the virtual receiving array according to Variation 2 of Embodiment 1. show. 18B shows an example of a cross-sectional view along the second axis direction, which is a directivity pattern of two-dimensional beams by the virtual receiving array according to Variation 2 of Embodiment 1. FIG.

Specifically, in the two-dimensional beam pattern formed by the beamformer method using all antenna elements of the virtual receive array shown in FIG. 16C, FIG. 1 shows a cross-sectional view along a direction. Also, FIG. 18B shows a cross-sectional view along the second axis direction at 0 degrees in the first axis direction. 18A and 18B show the case of d _H =0.5 wavelength and d _V =0.68 wavelength.

As shown in FIG. 16C, the virtual receiving array has an aperture length of 7×d _H (VA#1 to VA#8, VA#17 to VA#24) in the first axis direction and Aperture length is 9× _dV (VA#9, VA#4, VA#11, VA#14, VA#15, VA#25, VA#20, VA#27, VA#30, VA#31) . The virtual antennas are evenly spaced at intervals of 1×d _V or 1×d _H . Thereby, a grating-free beam can be formed as shown in FIGS. 18A and 18B.

19A shows virtual reception arrays (VA#1 to VA#8, VA#17 to VA#) arranged at equal intervals in the first axis direction of the virtual reception array (FIG. 16C) according to variation 2 of Embodiment 1. FIG. 24) shows an example of a directivity pattern by a one-dimensional beam.

Of the virtual reception arrays VA#1 to VA#32 shown in FIG. 16C, the virtual reception arrays VA#1 to VA#8 or the virtual reception arrays VA#17 to VA# arranged at equal intervals in the first axis direction 24, an aperture length of 7×d _H forms, for example, a one-dimensional beam pattern in the first axis direction shown in FIG. 19A.

FIG. 19B shows an example of a directivity pattern of a one-dimensional beam by a virtual reception array arranged at equal intervals in the second axis direction of the virtual reception array according to Variation 2 of Embodiment 1. FIG.

Among the virtual reception arrays VA#1 to VA#32 shown in FIG. 16C, virtual reception arrays VA#9, VA#4, Using VA#11, VA#14, VA#15, VA#25, VA#20, VA#27, VA#30, and VA#31, an aperture length of 9× _dV is shown in FIG. 19B, for example. A one-dimensional beam pattern is formed in the direction of the second axis.

By comparing FIGS. 12A and 12B according to Variation 1 of Embodiment 1 with FIGS. 19A and 19B according to Variation 2, the following can be understood. Compared to variation 1 of Embodiment 1, in which virtual reception arrays are densely arranged at equal intervals of the same number shown in FIG. 10C, variation 2 shown in FIG. Smaller and higher angular resolution is obtained.

On the other hand, Variation 2 of Embodiment 1 shown in FIGS. 18A and 18B has a higher side lobe level of the two-dimensional beam than Variation 1 of Embodiment 1 shown in FIGS. 12A and 12B.

Therefore, first, in the antenna arrangement of Variation 2 of Embodiment 1, the directions of arrival are roughly estimated using the two-dimensional beams shown in FIGS. 18A and 18B. Next, in the vicinity of the estimated angle of arrival, the direction of arrival is precisely estimated using a virtual reception array that forms a one-dimensional beam shown in FIGS. 19A and 19B in the same variation 2 antenna arrangement. good too.

Such an estimation process reduces the probability of false positives with the one-dimensional beam shown in FIGS. 19A and 19B, which has lower sidelobes than the two-dimensional beam shown in FIGS. can be estimated. In addition, it becomes possible to estimate the positions of two or more targets, which are difficult to determine with the one-dimensional beams shown in FIGS. 19A and 19B, and further reduce the amount of calculation.

Variation 1 and Variation 2 have been described above as examples of the antenna arrangement according to the first embodiment.

As described above, in the first embodiment, the radar apparatus 10 includes the radar transmission section 100 that transmits a radar transmission signal by switching the plurality of transmission antenna elements #1 to #Nt of the transmission array antenna 108, and the radar transmission section 100 that transmits the radar transmission signal as a target. and a radar receiver 200 that receives a reflected wave signal reflected at the transmission array antenna 202 using a plurality of reception antenna elements #1 to #Na of the transmission array antenna 202 . Also, in Embodiment 1, the transmitting antenna elements #1 to #Nt and the receiving antenna elements #1 to #Na are arranged according to the above rule.

Thereby, the transmitting array antenna 108 and the receiving array antenna 202 can be formed into sub-arrays, for example, to increase the size of the antenna elements and improve the antenna gain. In addition, a virtual receiving array arranged at equal intervals of the first interval d _H and the second interval d _V can be constructed by arranging the antennas, and angular sidelobe or grating lobe components can be suppressed.

According to Embodiment 1, the sizes of the transmitting array antenna 108 and the receiving array antenna 202 are expanded by, for example, sub-arraying, the reception SNR of the reflected wave signal is improved, and the side lobe in the beam pattern formed by the virtual receiving array is reduced. Alternatively, a MIMO radar capable of suppressing grating lobes can be constructed.

(Embodiment 2)
In the first embodiment, the second antenna group is arranged in two rows in a zigzag pattern, for example, like the second antenna group G2 in FIG. 9A. As shown in FIG. 9A, the antenna Tx2 ₁ of the first row and the antenna Tx2 ₂ of the second row are spaced apart by a second spacing along the second axis and are spaced apart by a first spacing along the first axis. are spaced x _s times apart. _Further , the antenna Tx2-2 is arranged between the antenna _Tx2-1 and the antenna _Tx1-1 in the coordinates of the first axis.

Instead, an arrangement in which the antenna elements of the second antenna group expand the arrangement range on the first axis will be described. In other words, the antenna elements of the second antenna group are all arranged at different second axis coordinates. Furthermore, at least two antenna elements of the second antenna group are positioned at the same first axis coordinate. As a result, compared with the first embodiment, the opening length of the antenna elements constituting the transmission array antenna can be widened in the second axis direction, and the gain of the antenna elements can be increased. can.

In Embodiment 2 and variations ₁ and 2 thereof, which will be described below, the antenna elements may have a sub-array configuration. Arrays can be configured.

In Embodiment 2, when the size of the transmitting antenna element is increased in the second axis direction compared to Embodiment 1, the probability of false detection is reduced, and an antenna arrangement that configures an efficient virtual reception array. , and a direction-of-arrival estimation method using it.

FIG. 20A shows an example of arrangement of antenna elements Tx#1 to #Nt of the transmitting array antenna 108g according to the second embodiment. FIG. 20B shows an example of arrangement of antenna elements Rx#1 to #Na of receiving array antenna 202g according to the second embodiment. FIG. 20C shows an example of arrangement of the virtual reception array 500g according to the second embodiment.

20A to 20C show as an example a case where the number of antenna elements Nt of the transmitting array antenna 108g is 6, the number of antenna elements Na of the receiving array antenna 202g is 8, and the number of elements of the virtual receiving array 500g is 48. ing. A first axis and a second axis shown in FIGS. 20A and 20B are orthogonal to each other.

In FIG. 20A, the antenna elements of the transmission array antenna 108g are denoted by Tx#1 to Tx#6. The first antenna group G1 includes Tx#1 (at least one first antenna element). The second antenna group G2 includes Tx#1 to Tx#6 (a plurality of second antenna elements).

As shown in FIG. 20A, the transmitting antenna elements Tx#1 to Tx#6 are arranged at second intervals in the second direction. In other words, the transmitting antenna elements Tx#1 to Tx#6 are arranged at different second axis coordinates. Furthermore, the transmitting antenna elements Tx#1 to Tx#4 are respectively arranged at a first interval in the first axis direction, and the first axis coordinates of the transmitting antenna elements Tx#1 and Tx#2 are respectively Equal to the first axis coordinates of Tx#5 and Tx#6.

In FIG. 20B, the receiving antenna elements (a plurality of third antenna elements) are represented by Rx#1 to Rx#8. As shown in FIG. 20B, the receiving antenna elements Rx#1 to Rx#8 are arranged at equal intervals in the first axial direction at first intervals.

When the arrangement of antenna elements shown in FIGS. 20A and 20B is used, the configuration of the virtual receiving array 500g shown in FIG. The construction of the virtual receive array 500g is obtained, including the regions with d _V and 1×d _H .

FIG. 21 shows an example of sizes 113 and 215 of antenna elements according to the second embodiment.

For the antenna arrangements shown in FIGS. 20A and 20B, the antenna element sizes 113, 215 can be defined as shown in FIG. 21, for example. Here, the sizes 113 and 215 of the antenna elements are sizes that do not interfere with adjacent antenna elements.

In FIG. 21, the antenna element size 113h of the transmission array antenna 108h is formed with an aperture length of d _H or less in the first axis direction and an aperture length of 4×d _V or less in the second axis direction. Also, the antenna element size 215h of the receiving array antenna 202h is formed with an aperture length of d _H or less in the first axis direction and an arbitrary aperture length in the second axis direction.

Each of the antenna elements shown in FIG. 21 may be configured using a sub-array antenna using a plurality of antenna elements. Furthermore, the side lobe may be suppressed by applying an array weight to the subarray antenna.

Note that the transmission array antenna 108h may be beamformed by a plurality of antenna elements. For example, power is supplied to the transmission antenna elements Tx#1 to Tx#6 while controlling the phase, and 8 virtual reception array elements are configured with 1 transmission antenna element and 8 reception antenna elements.

For example, in the transmission antenna 108h _shown in _FIG . Since the antennas can be arranged densely, it is possible to form a beam with a low sidelobe level when forming the beam.

In this manner, the antenna arrangement and antenna element sub-array configuration of the present disclosure allows the transmit antenna 108 to be used as a single high-gain antenna. In the case of time-division multiplexing MIMO radar, the number of multiplexing is reduced, so the transmission period is shortened, and therefore the maximum Doppler speed that can be analyzed by the Doppler analysis unit can be increased. Therefore, the above example is more suitable for detecting long-distance, high-speed objects than when signals are transmitted independently from the transmitting antenna elements.

<Variation 1 of Embodiment 2>
In Variation 1 of Embodiment 2, compared with Embodiment 2, the antenna arrangement in which the spacing in the first axis direction of the receiving antennas is widened to widen the aperture length of the virtual receiving array and high resolution is obtained. explain.

FIG. 22A shows an example of arrangement of antenna elements Tx#1 to #Nt of transmission array antenna 108i according to Variation 1 of Embodiment 2. FIG. FIG. 22B shows an example of arrangement of antenna elements Rx#1 to #Na of receiving array antenna 202i according to Variation 1 of Embodiment 2. In FIG. FIG. 22C shows an example of arrangement of virtual reception arrays 500i according to variation 1 of the second embodiment.

FIGS. 22A to 22C show, as an example, the case where the number of antenna elements Nt of the transmitting array antenna 108i is 5, the number of antenna elements Na of the receiving array antenna 202i is 6, and the number of elements of the virtual receiving array 500i is 30. ing. The first and second axes shown in FIGS. 22A and 22B are orthogonal to each other.

In FIG. 22A, the antenna elements of the transmission array antenna 108i are denoted by Tx#1 to Tx#5. The first antenna group G1 includes Tx#1 (at least one first antenna element). The second antenna group G2 includes Tx#1 to Tx#5 (a plurality of second antenna elements).

As shown in FIG. 22A, the transmitting antenna elements Tx#1 to Tx#5 are arranged at second intervals in the second direction. In other words, the transmitting antenna elements Tx#1 to Tx#5 are arranged at different second axis coordinates. Furthermore, the transmitting antenna elements Tx#1 to Tx#4 are arranged at a first interval in the first axis direction, and the first axis coordinate of the transmitting antenna element Tx#1 is the first axis coordinate of Tx#5. Equal to axis coordinates.

In FIG. 22B, the receiving antenna elements (a plurality of third antenna elements) are represented by Rx#1 to Rx#6. As shown in FIG. 22B, the receiving antenna elements Rx#1 to Rx#6 are arranged at equal intervals of 2×d _H in the first axis direction, and are arranged at intervals of 5×d _V in the second axis direction. is placed in

When using the arrangement of antenna elements shown in FIGS. 22A and 22B, the configuration of the virtual receiving array 500i shown in FIG. 22C, that is, the virtual The configuration of receive array 500g is obtained.

For the antenna arrangements shown in FIGS. 22A and 22B, the sizes of the antenna elements can be defined similarly to the antenna element sizes 113, 215 of Embodiment 2 shown in FIG. 21, for example.

For example, the antenna elements of the transmission array antenna 108i shown in FIG. 22A are formed with an aperture length of d _H or less in the first axis direction and an aperture length of 4×d _V or less in the second axis direction. Also, the antenna elements of the receiving array antenna 202i shown in FIG. 22B are formed with an aperture length of 2×d _H or less in the first axis direction and an aperture length of 5×d _HV or less in the second axis direction.

Each of the antenna elements shown in FIG. 22A may be configured using a sub-array antenna using multiple antenna elements. Furthermore, the side lobe may be suppressed by applying an array weight to the subarray antenna.

According to variation 1 of the second embodiment, virtual reception array 500i shown in FIG. 22C is configured by the configurations shown in FIGS. 22A and 22B. As a result, the aperture length of the transmitting array antenna elements in the second axial direction can be increased, and the aperture length of the receiving array antenna elements in the first axial direction can be increased more than in the second embodiment.

<Variation 2 of Embodiment 2>
The antenna arrangement of variation 2 of the second embodiment adopts an antenna arrangement that partially includes the antenna arrangement of variation 1 of the embodiment. In addition to the effect obtained in variation 1 of the second embodiment, the effect of improving the resolution and, in the case of time-division MIMO, the effect of improving the maximum Doppler velocity that can be analyzed by the Doppler analysis unit can be obtained.

FIG. 23A shows an example of arrangement of antenna elements Tx#1 to #Nt of transmission array antenna 108j according to variation 2 of embodiment 2. FIG. FIG. 23B shows an example of the arrangement of antenna elements Rx#1 to #Na of receiving array antenna 202j according to Variation 2 of Embodiment 2. In FIG. FIG. 23C shows an example of arrangement of virtual reception array 500j according to variation 2 of the second embodiment.

In FIG. 23A, transmitting antenna elements Tx#1 to Tx#5 have the same configuration as transmitting antenna elements Tx#1 to Tx#5 of Variation 1 of Embodiment 2 shown in FIG. 22A. Also, in FIG. 23A, the first antenna group G1 includes transmitting antenna elements Tx#4, Tx#6, Tx#7, and Tx#8, and the second antenna group G2 includes transmitting antenna elements Tx#1 to Includes Tx#5.

23B, receiving antenna elements Rx#1, Rx#2, Rx#4, Rx#5, and Rx#6 are the receiving antenna elements Rx#1 and Rx# of Variation 1 of Embodiment 2 shown in FIG. 22B. 2, Rx#4, Rx#5, and Rx#6. Also, in FIG. 23B, the first axis coordinate and the second axis coordinate of the receiving antenna element Rx#3 correspond to the positions of the other receiving antenna elements Rx so that the virtual antenna elements of the virtual receiving array are configured at overlapping positions. It differs from any of the first and second axis coordinates of #1, Rx#2, Rx#4, Rx#5 and Rx#6.

In the virtual reception array shown in FIG. 23C, at the position of the virtual antenna element VA#6, a virtual antenna element configured by a transmission antenna element Tx#2 and a reception antenna element Rx#3, and a transmission antenna element Tx#3. A virtual antenna element configured by the receiving antenna element Rx#2 is overlapped. Therefore, at the position of virtual antenna element VA#6, there are two received signals corresponding to overlapping virtual antenna elements. One of the two received signals may be used to estimate the direction of arrival, the average value thereof may be used to estimate the direction of arrival, or the sum thereof may be used to estimate the direction of arrival. Since the positions of the virtual antennas overlap, there is no phase difference due to the arrival angles of the two overlapping received signals. Also, Doppler analysis may be performed using two overlapping received signals.

FIG. 24 shows an example of antenna element sizes 113k and 215k according to variation 2 of the second embodiment.

As shown in FIG. 24, antenna sizes 113k and 215k can be defined similarly to the second embodiment and variation 1 of the second embodiment, for example. Here, the antenna element sizes 113k and 215k are sizes that do not interfere with adjacent antenna elements.

In FIG. 24, the sizes of the transmitting antenna elements Tx#1 to #8 and the receiving antenna elements Rx#1 to #6 are the same. However, the sizes of the transmitting antenna elements Tx#1-#8 and the receiving antenna elements Rx#1-#6 may differ as long as they are of a size that does not interfere with adjacent antennas. Also, the transmitting antenna elements and the receiving antenna elements may be configured using subarray antennas, and side lobes may be suppressed by applying array weights to the subarray antennas.

For example, each of the receiving antenna elements Rx#1 to Rx#6 may be composed of a sub-array of two elements in the first axis direction and four elements in the second axis direction. Furthermore, the transmitting antenna elements Tx#6 to Tx#8 may be configured by a subarray having an aperture length of 3×d _H in the first axis direction and 8×d _V in the second axis direction. Compared to the configuration of FIG. 23, the beam pattern of the transmitting antenna 108k becomes narrower, and the antenna gain in the front direction increases, thereby improving the SNR.

FIG. 25A is a directivity pattern of a two-dimensional beam (main beam: horizontal 0°, vertical 0° direction) by virtual receiving array 500j according to variation 2 of Embodiment 2 shown in FIG. 1 shows an example of a cross-sectional view along . FIG. 25B shows an example of a cross-sectional view along the second axis direction of a directivity pattern of two-dimensional beams by the virtual receiving array according to Variation 2 of Embodiment 2. FIG.

Compared to variation 1 of the second embodiment, variation 2 of the second embodiment has a higher side lobe level because virtual reception arrays 500j are arranged sparsely. Therefore, as described above in the description of variation 2 of Embodiment 1, by combining with the method of independently estimating the directions of arrival in the first axial direction and the second axial direction, erroneous detection due to the height of the side lobe level may suppress the effect on the probability of For example, the virtual reception array 500j shown in FIG. 23C performs precise direction-of-arrival estimation in the first and second axial directions, and performs precise direction-of-arrival estimation using a two-dimensional beam for angles exceeding a certain threshold. I do. As a result, it is possible to suppress the influence of the height of the sidelobe level on the probability of erroneous detection, and further reduce the amount of calculation required for direction-of-arrival estimation.

As in Embodiment 2 and Variation 1 of Embodiment 2, some of the plurality of transmitting antenna elements Tx#1 to Tx#8 included in transmitting array antenna 108j may be multiplexed and used. For example, among the plurality of transmitting antenna elements Tx#1 to Tx#8 included in the transmitting array antenna 108j, five transmitting antennas Tx#1 to Tx#5 may be multiplexed and used. As a result, the angle estimation performance in the second axis direction (vertical direction) can be maintained, and the number of multiplexed antennas can be reduced. Further, for example, among the plurality of transmitting antenna elements Tx#1 to Tx#8 included in the transmitting array antenna 108j, the four transmitting antennas Tx#4, Tx#6, Tx#7, and Tx#8 are May be used multiplexed. As a result, the number of multiplexed antennas can be reduced while maintaining the angle estimation performance in the direction of the first axis (horizontal direction). In the case of time-division multiplexing MIMO radar, the smaller the number of multiplexed antennas, the more signals with shorter transmission cycles can be analyzed by Doppler analysis section 213, and the maximum speed that can be analyzed by Doppler analysis section 213 can be increased.

Also, beam formation may be performed by a plurality of antenna elements included in a plurality of transmitting antenna elements Tx#1 to Tx#8.

(Other embodiments)
In Embodiment 1, as the second antenna group, the antenna elements are arranged at intervals of a second interval in the direction of the second axis, and are arranged at intervals of x _s times the first interval in the direction of the first axis for each antenna element. configuration. Alternatively, as a second group of antennas, the antennas are arranged at intervals of a second interval in the direction of the second axis, and are arranged at intervals of x _s,j times the first interval in the direction of the first axis in N cycles. Other configurations are also conceivable.

ここで、Nは2よりも大きくp_r1以下の整数であり、j=0,1,…,N-1に対して、x_s,jは、それぞれ、0以上p_r1未満の整数である。 Specifically, in the formula (20) described in the description of the first embodiment _, instead of p _tH , p' A configuration using _tH is also conceivable.

Here, N is an integer greater than 2 and less than p _r1 , and x _s,j is an integer greater than or equal to 0 and less than p _r1 for j=0, 1, . . . , N−1.

For example, if N=p _r1 and x _s,j =j, then the antenna element of the transmit array antenna 108 has an aperture length of N×d _V in the second axis direction. Therefore, compared to the case where the antenna elements of the transmission array antenna 108 are arranged linearly at equal intervals at the basic intervals d _H and d _V , the size of the antenna elements of the transmission array antenna 108 and the reception array antenna 202 can be increased and the antenna height can be increased. gain can be obtained. Also, by arranging the virtual receiving arrays at regular intervals of about half a wavelength, the grating lobe or sidelobe components can be suppressed.

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 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.

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 inputs and outputs. 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. After the LSI is manufactured, a programmable FPGA (Field Programmable Gate Array) and a reconfigurable processor capable of reconfiguring connection or setting 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. For example, the application of biotechnology is a possibility.

A radar apparatus according to the present disclosure includes a radar transmission circuit that transmits a radar signal from a transmission array antenna, and a radar reception circuit that receives a reflected wave signal of the radar signal reflected by a target from a reception array antenna, One of the transmitting array antenna and the receiving array antenna includes a first antenna group and a second antenna group, and the first antenna group has a phase center of each antenna element aligned along a first axis direction. The second antenna group includes one or more first antenna elements and one shared antenna element arranged at intervals of one, and the second antenna group includes a plurality of second antenna elements and the one shared antenna element. wherein the phase center of each antenna element is arranged in two rows along a second axis direction different from the first axis direction at a second arrangement interval, and the phase of the antenna elements included in each of the two rows The center positions in the second axis direction are different from each other, and the phase center of the other of the transmitting array antenna and the receiving array antenna is located along the first axis direction in the first position based on the first arrangement interval. arranged at a third arrangement interval that is smaller than the first arrangement interval, and arranged at a fourth arrangement interval that is larger than the second arrangement interval along the second axial direction. Also includes a plurality of third antenna elements.

In the radar device of the present disclosure, the first arrangement interval is equal to p _r1 times the first interval, the second arrangement interval is equal to the second interval, and the first row number is equal to the p _r1 , the third spacing is equal to the first spacing, the fourth spacing is equal to p _t2 times the second spacing, and the two antennas of the second antenna group columns are positioned on the first axis that differ from each other by x _s times the first spacing, wherein p _r1 is an integer greater than 1, and p _t2 is an integer greater than 1; and the x _s is an integer greater than 0 and less than the p _r1 .

In the radar device of the present disclosure, said _xs is equal to one.

In the radar apparatus of the present disclosure, the number of elements of the one or more first antenna elements is equal to one.

In the radar device of the present disclosure, the number of elements of the plurality of third antenna elements is equal to the number of the first columns.

In the radar device of the present disclosure, the number of elements of the plurality of third antenna elements is greater than the number of the first columns.

In the radar device of the present disclosure, the first interval and the second interval are 0.3 wavelengths or more and 2 wavelengths or less with respect to the wavelength of the radar signal.

In the radar device of the present disclosure, the first antenna group and the second antenna group are arranged in a T shape or a cross shape.

In the radar device of the present disclosure, the first axial direction and the second axial direction are orthogonal to each other.

A radar apparatus according to the present disclosure includes a radar transmission circuit that transmits a radar signal from a transmission array antenna, and a radar reception circuit that receives a reflected wave signal of the radar signal reflected by a target from a reception array antenna, one of the transmit array antenna and the receive array antenna includes a first antenna group and a second antenna group, the first antenna group being one shared antenna element or the phase of each antenna element One or more first antenna elements centered along the first axial direction and the one shared antenna element, and the second antenna group includes a plurality of second antenna elements and the one antenna element. and a shared antenna element, wherein the position of the phase center of each antenna element in a second axis direction different from the first axis direction is different from each other, and at least one phase center of the plurality of second antenna elements and the one The phase centers of the shared antenna elements have the same position in the first axis direction, and are arranged in one or more rows at the second arrangement interval in the second axis direction.

INDUSTRIAL APPLICABILITY The present disclosure is suitable for radar devices that detect a wide angle range, and can be mounted on vehicles, for example.

REFERENCE SIGNS LIST 10 radar device 100 radar transmitter 101, 101a radar transmission signal generator 102 code generator 103 modulator 104 LPF
105 transmission frequency conversion unit 106 power divider 107 transmission amplification unit 108 transmission array antenna 108-1, . , . . . , 201-Na antenna element system processing unit 202 receiving array antenna 202-1, . Conversion unit 209 Second AD conversion unit 210 Correlation calculation unit 211 Addition unit 212 Output switching unit 213-1, ..., 213-Nt Doppler analysis unit 214 Direction estimation unit 215 Size of receiving antenna element 300 Reference signal generation unit 400 Control unit 500 Virtual Receive Array

Claims (10)

a radar transmission circuit for transmitting a radar signal from a transmission array antenna;
a radar receiver circuit for receiving a reflected wave signal of the radar signal reflected by a target from a receiving array antenna;
and
one of the transmitting array antenna and the receiving array antenna includes a first antenna group and a second antenna group;
The first antenna group includes one or more first antenna elements and one shared antenna element,
the phase center of each antenna element of the first antenna group is arranged parallel to the first axis at intervals of pr1 times the first interval,
The second antenna group includes a plurality of second antenna elements and the one shared antenna element,
the phase center of each antenna element of the second antenna group is arranged in a first row and a second row parallel to the second axis;
the second axis and the first axis are orthogonal to each other;
the antenna elements in the first row are spaced parallel to the second axis by twice a second spacing;
the antenna elements in the second row are spaced parallel to the second axis every two times the second spacing;
The first row is shifted relative to the second row parallel to the first axis by xs times the first distance and parallel to the second axis by the second distance. placed in a shifted position,
the other of the transmitting array antenna and the receiving array antenna includes a third antenna element of column pr1 and row pr2;
phase centers of the third antenna elements are arranged parallel to the first axis and spaced apart by the first spacing;
arranged parallel to the second axis every fourth spacing greater than the second spacing;
said pr1 is an integer greater than 1, said pr2 is an integer greater than or equal to 1, and said xs is an integer greater than 0 and less than said pr1;
radar equipment. said fourth interval is equal to pt2 times said second interval;
said pt2 is an integer greater than 1;
The radar device according to claim 1. said xs is equal to 1,
The radar device according to claim 1 or 2. the number of elements of the one or more first antenna elements is equal to one;
The radar device according to any one of claims 1 to 3. said pr2 is equal to 1;
The radar device according to any one of claims 1 to 4. said pr2 is greater than 1;
The radar device according to any one of claims 1 to 4. The first interval and the second interval are 0.3 wavelength or more and 2 wavelengths or less with respect to the wavelength of the radar signal,
Radar device according to any one of claims 1 to 6. a radar transmission circuit for transmitting a radar signal from a transmission array antenna;
a radar receiver circuit for receiving a reflected wave signal of the radar signal reflected by a target from a receiving array antenna;
and
one of the transmitting array antenna and the receiving array antenna includes a first antenna group and a second antenna group;
The first antenna group is one shared antenna element, or one or more first antenna elements in which the phase center of each antenna element is arranged parallel to the first axis and the one shared antenna element. including
The second antenna group includes a plurality of second antenna elements and the one shared antenna element,
each of the phase centers of each antenna element of the second antenna group is arranged at a non-overlapping position;
At least two antenna elements among the plurality of second antenna elements and the one shared antenna element are arranged at different positions separated by four times the second spacing on the second axis, and placed at the same position on the axis,
Among the plurality of second antenna elements and the one shared antenna element, the remaining antenna elements are arranged at different positions on the second axis and arranged at different positions on the first axis,
At least one antenna element adjacent to the at least two antenna elements among the remaining antenna elements is arranged at a position xs times the first distance on the first axis,
the first axis and the second axis are orthogonal to each other,
the other of the transmitting array antenna and the receiving array antenna includes a third antenna element of column pr1 and row pr2;
the phase centers of the third antenna elements are arranged parallel to the first axis, in the pr2 rows, at every integer multiple of the first interval;
The radar device, wherein the pr1 is an integer greater than 1, the pr2 is an integer equal to or greater than 1, and the xs is an integer greater than 0 and smaller than the pr1. The phase centers of the third antenna elements in the pr1 column and the pr2 row are further arranged parallel to the second axis, in the pr1 column, at every integer multiple of the second interval,
The radar device according to claim 8 . One of the phase centers of the third antenna element of the pr1 column and pr2 row is
further arranged parallel to the first axis at a position shifted by the first spacing and parallel to the second axis at a position shifted by the second spacing;
A radar device according to claim 9 .

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