WO2021181598A1

WO2021181598A1 - Radar device

Info

Publication number: WO2021181598A1
Application number: PCT/JP2020/010760
Authority: WO
Inventors: 隆文永野; 亘辻田; 広幸蔦田
Original assignee: 三菱電機株式会社
Priority date: 2020-03-12
Filing date: 2020-03-12
Publication date: 2021-09-16
Also published as: JP7270835B2; JPWO2021181598A1

Abstract

According to the present invention, first to Mth chirp signals having first to Mth (M is an integer greater than or equal to 2) transmission frequency bands having the same bandwidth and adjacent to each other are synchronized and repeatedly generated and transmitted for each chirp period. A reflected wave generated by reflecting a transmission wave at a target is received to generate first to Mth reception signals. First to Mth beat signals are generated from the first to Mth chirp signals and the first to Mth reception signals. One composite signal is generated by connecting the first to Mth beat signals to each other. The distance from a plurality of sequentially generated composite signals to a target and the speed of the target are calculated. Even when the target is moving, the distance can be measured with high resolution without causing distortion, splitting, or the like at the peak of the Fourier transform.

Description

Radar device

This disclosure relates to radar equipment. The present disclosure relates to a radar device having a particularly high range resolution.

The target is detected with high distance resolution by transmitting the chirp signal, converting the received signal obtained by receiving the reflected wave at the target (target object) into a beat signal, and detecting the peak from the Fourier transform. FMCW (Frequency-Modulated Continuous Wave) radar is known. In the FMCW radar, the range resolution can be increased by widening the bandwidth of the chirp signal, but the wider the bandwidth, the more difficult it is to generate the chirp signal, and it becomes difficult to widen the bandwidth of the antenna, amplifier, and the like. Therefore, it is being studied to improve the long-distance resolution by using a plurality of adjacent frequency bands.

For example, Non-Patent Document 1 discloses a method for fusing measurement data of two frequency bands. In the technique of Non-Patent Document 1, the frequency step is performed by simultaneously measuring the reflected wave with a transmitter / receiver having a frequency band of 40 GHz and 60 GHz and a frequency band of 100 GHz and 150 GHz, zero padding to the Fourier transform of the measurement data, and inverse Fourier transform. If there is a frequency gap between the two frequency bands, the missing frequency points are linearly interpolated.

When a moving target is detected by the technique of Non-Patent Document 1, phase continuity cannot be ensured between data in two frequency bands, distortion, splitting, etc. occur at the peak of the Fourier transform, and the distance is high resolution. May not be able to be measured.

The present disclosure provides a radar device that can measure a distance with high resolution without causing distortion, splitting, etc. at the peak of the Fourier transform even if the target is moving by using a plurality of adjacent frequency bands. With the goal.

The radar device according to the present disclosure is
The first to M chirp signals of the first to M (M is an integer of 2 or more) transmission frequency bands having equal bandwidths and adjacent to each other and having continuous frequency changes are synchronized with each chirp cycle. A signal generator that repeatedly generates signals and
A signal transmitting device that transmits a first to M transmission wave corresponding to the first to M chirp signals repeatedly generated by the signal generating device, and a signal transmitting device.
Reception of the first to M corresponding to the first to M transmission frequency bands, respectively, of the reflected wave generated by the reflection of the first to M transmission waves transmitted by the signal transmission device at the target. A signal receiver that receives in the frequency band and generates the first to M received signals, and
From the first to M chirp signals generated by the signal generator and the first to M received signals generated by the signal receiving device, frequency components corresponding to the distance to the target are obtained. A signal conversion device that generates the first to Mth beat signals to have, and
A signal synthesizing unit that connects the first to M beat signals generated by the signal conversion device to each other at boundaries between the chirp periods to generate one composite signal for each chirp period.
It is provided with a target detection unit that calculates the distance to the target and the speed of the target from a plurality of synthetic signals sequentially generated by the signal synthesis unit.

According to the radar device of the present disclosure, it is possible to measure the distance with high resolution without causing distortion, splitting, etc. at the peak of the Fourier transform even if the target is moving.

It is a block diagram which shows the outline of the radar apparatus of embodiment. It is a block diagram which shows the specific configuration example of the radar apparatus of FIG. It is a block diagram which shows the structural example of the signal processing apparatus of FIG. (A) is a waveform diagram showing a transmission signal and a reception signal of the radar device of the embodiment, (b) to (d) are diagrams showing a beat signal obtained from the above transmission signal and the reception signal, (e). ~ (G) is a figure which shows the composite signal obtained by connecting the said beat signals. FIG. 4A is an enlarged view of a part of FIG. 4A, and a code indicating a period is added to the transmission signal, the reception signal, and the frequency difference, and FIG. 4B is the beat due to the frequency difference in FIG. 4A. A figure showing one method of connecting signals by a comparative example, (c) is a figure showing a method of connecting beat signals by the frequency difference of (a) according to an embodiment. (A) is a diagram in which a part of FIG. 4 (a) is enlarged and a code indicating a period is added to the transmission signal, the reception signal, and the frequency difference, and the portion of the reception signal that arrives with a delay. (B) is a diagram showing a method of synthesizing a beat signal based on the frequency difference of (a). It is a figure which shows an example of the result of the Fourier transform for one composite signal. (A) is a diagram showing the results of Fourier transform on a plurality of composite signals, and (b) is an example of a change in peak phase in (a). It is a figure which shows an example of the result of the further Fourier transform with respect to the result of the Fourier transform shown in FIG. 8 (a). It is a flowchart which shows an example of the processing procedure after receiving the reflected wave of the radar apparatus of embodiment. It is a figure which shows the hardware configuration of the computer which realizes the function of the part other than the antenna of the radar apparatus of Embodiment 1. FIG.

FIG. 1 shows an outline of the radar device RD of the embodiment.
The illustrated radar device RD repeatedly generates and transmits chirp signals of the first to third М (М is an integer of 2 or more) frequency bands having the same bandwidth and adjacent to each other in synchronization with each other, and at the target TG. The reflected wave due to the reflection of the above is received to generate a received signal, and the distance to the target TG and the speed of the target TG are calculated based on the beat signal due to the frequency difference between the transmitted chirp signal (transmitted signal) and the received signal.
In the following, a case where the above М is 3 and the chirp signal is an up chirp signal will be described.

The radar device RD shown in FIG. 1 includes a control device 100, a reference signal generator 102, a signal generation device 110, a signal transmission device 120, a signal reception device 130, a signal conversion device 140, and a signal processing device 150.
The signal transmission device 120 has first to third transmission units 121 to 123. The signal receiving device 130 has first to third receiving units 131 to 133. The signal conversion device 140 has first to third conversion units 141 to 143.
The first transmitting unit 121, the first receiving unit 131, and the first conversion unit 141 are provided so as to correspond to each other. The second transmitting unit 122, the second receiving unit 132, and the second converting unit 142 are provided so as to correspond to each other. The third transmitting unit 123, the third receiving unit 133, and the third conversion unit 143 are provided so as to correspond to each other.

FIG. 2 shows a specific configuration example of the radar device RD of FIG.
The radar device RD shown in FIG. 2 includes a control device 100, a reference signal generator 102 (omitted in FIG. 2), and a signal processing device 150, as well as a DDS 3, a high frequency signal generator 4, mixers 11 to 13, and amplifiers 21 to 21. 23, a transmission / reception switch 31 to 33, an antenna 41 to 43, an amplifier 51 to 53, a mixer 61 to 63, an amplifier 71 to 73, and an A / D converter 81 to 83 are provided.
DDS is an abbreviation for Direct Digital Synthesizer (Digital Direct Synthesizer).

The signal generator 110 is composed of the DDS 3, the high frequency signal generator 4, and the mixers 11 to 13.

The amplifier 21, the transmission / reception switch 31, and the antenna 41 constitute the first transmission unit 121. The amplifier 22, the transmission / reception switch 32, and the antenna 42 constitute a second transmission unit 122. The amplifier 23, the transmission / reception switch 33, and the antenna 43 constitute a third transmission unit 123.

The first receiving unit 131 is composed of the antenna 41, the transmission / reception switching device 31, and the amplifier 51. The second receiving unit 132 is composed of the antenna 42, the transmission / reception switching device 32, and the amplifier 52. The antenna 43, the transmission / reception switch 33, and the amplifier 53 constitute a third receiving unit 133.

The mixer 61, the amplifier 71, and the A / D converter 81 constitute the first conversion unit 141. The mixer 62, the amplifier 72, and the A / D converter 82 constitute a second conversion unit 142. The mixer 63, the amplifier 73, and the A / D converter 83 constitute a third conversion unit 143.

Since the control device 100 controls the DDS3 of the signal generation device 110, it can be seen as forming a part of the signal generation device 110.
Similarly, since the control device 100 controls the A / D converters 81 to 83 of the signal conversion device 140, it can be seen as forming a part of the signal conversion device 140.

As shown in FIG. 3, the signal processing device 150 has a signal synthesis unit 151 and a target detection unit 152.

The control device 100, DDS3, high-frequency signal generator 4, A / D converters 81 to 83, and signal processing device 150 are connected to a common reference signal generator 102 (FIG. 1) and operate in synchronization with each other.
It is assumed that each of the mixers 11 to 13 and 61 to 63 has a function of filtering signals other than the desired signal after mixing the signals.

The signal generation device 110 _{repeats the first} to _third chirp signals S1 to S3 and generates them in synchronization with each other.
Examples of chirp signals _S 1 ~ _{S 3} is shown in Figure 4 (a).
Each chirp signals S _{1 ~} S ₃ as shown are up-chirp signal, the modulation width, i.e. bandwidth equal. This modulation width is represented by B. Chirp signal _S 1 ~ _{S 3} chirp starting frequency (start frequency) respectively represented by _{_f} 1 ~ _f _3.
The band from f ₁ to f ₁ + B is called the first frequency band and is represented _{by the code FC 1.} The band from f ₂ to f ₂ + B is referred to as a second frequency band and is represented _{by the code FC 2.} The band from f ₃ to f ₃ + B is called a third frequency band and is represented _{by the code FC 3.}

The length of the period of the chirp signal S _{1 ~} S ₃ (chirp period) are equal to each other, as soon as one cycle is completed the next cycle begins. In FIG. 4A, i, i + 1, i + 2, ... Are assigned as cycle numbers k.

_{A chirp signal S m} _{emitted in a certain frequency band FC m} (m is 1 or 2 in this case) in a certain period and a frequency band FC adjacent to the above frequency band FC _m in the next cycle on the higher frequency side. _The frequency changes continuously with the chirp signal S _{m + 1 emitted at m + 1.} That is, the frequency _f m + B at the chirp termination of the chirp signal _{S m} of the m, and the frequency _{f m + 1} at the (m + 1) of the chirp signal _{S m + 1} of the chirp start are equal. That is,
f _{m + 1} = f _m + B
There is a relationship.

Further, the phase at the chirp termination of the chirp signal S _m of the m, and the m + 1 of the chirp signal S _{m + 1} of the chirp at the beginning of the phase is equal.

Further, the product of the center frequency h _m _{(m is 1, 2 or 3 here) of each of the first} to third frequency bands FC 1 to FC ₃ and the length T of the chirp period is an integer, and the first to third frequencies are used. phase (initial _{_{phase) φ 1, k ~ φ 3}} , k at the beginning chirp of the chirp signals S _{1 ~} S ₃ of the M are identical to each other between mutually equal, and all chirp period.
Between the center frequency h _m and frequency f _m at chirp start, a relationship of the following equation (1).

Controller 100, a modulation width B, a length T of the period, the starting frequency _f 1 ~ _{f 3} of the chirp signal _S 1 ~ _{S 3,} the first phase phi ₁ the period of the chirp signal _S 1 ~ _{S _3,} _{Control is performed so that k} to φ3 _{and k} are values that satisfy the above conditions, respectively.

In the following, the modulation width B of the chirp signal S _{1 ~} S ₃ is assumed to be predetermined. In that case, the control device 100, the length T of the period, the starting frequency _{f 1} of the chirp signal _{S 1,} the first phase phi ₁ the period of the chirp signal _{_{_{S 1 ~ S 3, k ~}}} φ 3, and _k specify.

_{The DDS 3} generates a chirp signal S 0 based on a predetermined modulation width B, a period length T specified by the control device 100, a start frequency f ₁ , and a phase φ _{1, k.}
Chirp signal S ₀ generated is an end frequency start frequency at f ₁ -B is f _1, the length of the period T.

The high frequency signal generator 4 generates a predetermined high frequency signal HF of frequency B.

The chirp signal S ₀ output from the DDS 3 is input to the mixer 11.
Mixers 11-13 chirp signal _{S 0,} based on the high-frequency signal HF high-frequency signal generator 4 occurs, generates a chirp signal _{_S} 1 ~ _S _3.

The DDS 3 and the high-frequency signal generator 4 cause the mixers 11 to 13 to generate chirp signals S ₁ to S _{3 in} _{which the first phase of each cycle is a specified value φ 1, k} to φ _{3, k, respectively.} , Chirp signal S ₀ and high frequency signal HF are output. Specifically, the phase of the chirp signal S ₀ and the high frequency signal HF so that the first phase of each period of the chirp signals S ₁ to S ₃ _{becomes the specified values φ 1, k} to φ _{3, k, respectively.} The phase of is controlled.

_{The chirp signal S 0} is supplied from the DDS 3 to the mixer 11, and the high frequency signal HF is supplied from the high frequency signal generator 4.
In the mixer 11 therein, it generates a chirp signals _{S 1} the end frequency _f 1 + B starting frequency at _{f 1,} an end frequency starting frequency _f 1 -2B and _f 1 -B chirp signals _{S 1} 'is It is, of which chirp signals S _{1 'is} removed by filtering the chirp signals S ₁ is output. The chirp signal S ₁ is supplied to the amplifier 21 and the mixer 12.

To the mixer 12, the chirp signal S ₁ is supplied from the mixer 11, the high-frequency signal HF is supplied from the high frequency signal generator 4.
In its interior the mixer 12, an end frequency starting frequency _f 1 + B chirp signal _{S 2} of _f 1 + 2B, the end frequency start frequency at _f 1 -B are generated and chirp signal _{S 2} 'of the _{f 1} , of which the chirp signal S _{2 'are} removed by filtering the chirp signal S ₂ is outputted. The chirp signal S ₂ is supplied to the amplifier 22 and the mixer 13.

_{The chirp signal S 2} is supplied from the mixer 12 to the mixer 13, and the high frequency signal HF is supplied from the high frequency signal generator 4.
In the mixer 13 therein, a chirp signal _{S 3} end frequency of _f 1 + 3B in the start frequency _f 1 + 2B, end frequency start frequency at _{f 1} is and a chirp signal _{S 3} 'of _f 1 + B is generated, Among them chirp signal S _{3 'is} removed by filtering, the chirp signal S ₃ is output. The chirp signal _{S 3} is supplied to an amplifier 23.

Thus, the start frequency _{f 2} of the chirp signal _{S 2} is equal to the end frequency _f 1 + B of the chirp signal _{S 1,} starting frequency _{f 3} of the chirp signal _{S 3} is equal to the end frequency _f 2 + B of the chirp signal _{S 2.}
Therefore, chirp signals S _{1 ~} S ₃ can be said to change in frequency is continuous with each other.
Also, chirp signals _S 1 ~ _{S 3} phase _{_{φ 1, k ~ φ 3,}} k are equal to each other at the start chirp of each cycle is the same in different circumferential periods.

Signal transmitter 120 transmits a chirp signal _S 1 ~ _{S 3} generated by the signal generator 110 as a transmission wave.

Chirp signal

_S 1 ~ _{S 3} are amplified by the amplifiers 21 to 23 respectively, are supplied to the antenna 41 to 43 through the duplexer 31 to 33, from the antenna 41 to 43, the transmission wave corresponding to the chirp signal _S 1 ~ _{S 3} Is sent.
The transmitted chirp signal is also called a transmission signal.

The signal receiving device 130 receives the reflected wave generated by reflecting the transmitted wave transmitted by the signal transmitting device 120 at the target TG and generates a received signal. The received signal generated by receiving the reflected wave generated by reflecting the transmitted wave corresponding to the transmitted signal at the target TG is referred to as a received signal corresponding to the above-mentioned transmitted signal.

The receiving units 131 to 133 of the signal receiving device 130 are provided corresponding to the _{frequency bands FC 1} to FC _{3, respectively.} Similarly, the conversion units 141 to 143 of the signal conversion device 140 are provided corresponding to the _{frequency bands FC 1} to FC _{3, respectively.}

Reflected wave transmission wave transmitted from the antenna 41 to 43 in each frequency band are generated by reflection at the target TG is received by the antennas 41 to 43, the results generated received signal R _{1 ~} R ₃ are exchanged It passes through the switches 31 to 33 and is amplified by the amplifiers 51 to 53.
The amplified received signals _R 1 ~ _{R 3} are, as the output of the signal receiver 130, supplied to the signal converter 140.

Signal converting apparatus 140, the received signal _R 1 ~ _{R 3} outputted from the signal receiver 130, generates a beat signal _Q 1 ~ _{Q 3} from the transmission signal _S 1 ~ _{S 3} Metropolitan output from the signal generator 110 ..

Specifically, the received signals _R 1 ~ _{R 3} outputted from the signal receiver 130 is input to a mixer 61 to 63, is mixed with the transmission signal _S 1 ~ _{S 3} corresponding.
The mixer 61 mixes the received signal R ₁ and the transmitted signal S ₁ and removes signals other than the desired signal by filtering to generate the _{beat signal Q 1 shown in FIG. 4 (b).}

The mixer 62 mixes the received signal R ₂ and the transmitted signal S ₂ and removes signals other than the desired signal by filtering to generate the _{beat signal Q 2 shown in FIG. 4 (c).}
The mixer 63 mixes the received signal R ₃ and the transmitted signal S ₃ and removes signals other than the desired signal by filtering to generate the _{beat signal Q 3 shown in FIG. 4 (d).}
The figure shows the start and end of each of the beat signals Q _{1 ~} Q ₃ by an arrow.

The frequency of the beat signal Q ₁ is equal to the difference between the frequencies of the transmission signal S ₁ and the frequency of the reception signal R _1. The frequency of the beat signal Q ₂ is equal to the difference between the frequencies of the transmission signal S ₂ and the frequency of the reception signal R _2. The frequency of the beat signal Q ₃ is equal to the difference between the frequencies of the transmission signal S ₃ and the frequency of the reception signal R _3.
In FIG. 4 (a), the difference between the frequency, the same reference numerals as the corresponding beat signals Q _{1 ~} Q ₃ is are given.

The mixers 61 to 63 have a function of removing signals other than the desired signal, but the first to third receiving units 131 to 133 are among the received signals in the corresponding conversion units 141 to 143, respectively. it is desirable to have a function of removing frequency components other than the frequency components necessary for producing the desired beat signals Q _{1 ~} Q ₃ in the mixer by filtering.

Beat signals _Q 1 ~ _{Q 3} generated by the mixer 61 to 63 are amplified by the amplifiers 71 to 73, is converted into a digital signal by the A / D converters 81 to 83. The digital signal is also represented by the same reference numerals as the beat signals Q _{1 ~} Q ₃ analog.

Since the beat signal _Q 1 ~ _{Q 3} in which each generated from the transmission signal _S 1 ~ _{S 3} of frequency band _FC 1 ~ FC _3, respectively, the beat signal corresponding to the frequency band _FC 1 ~ FC _3, or frequency It is said to be a beat signal of bands FC ₁ to FC _3.

Signal combining unit 151 of the signal processing device 150, FIG. 4 a beat signal _{_{Q 1 ~ Q 3 (e)}} , (f), coupled as shown in (g), to generate a composite signal CS at every cycle.

Each composite signal CS is periodically (e.g., period i) the beat signal Q ₁ generated using the transmission signals S ₁ of the first frequency band FC _1, first in the next cycle (e.g., cycle i + 1) produced using a beat signal _{Q 2} to which has been generated using a second transmission signal _{S 2} of frequency bands FC _2, further next cycle (e.g., cycle i + 2) of the transmission signal _{S 3} of the third frequency band FC ₃ It is obtained by connecting the beat signal Q ₃ which is.

Coupling when the terminating of the beat signal Q ₁ (part of the period at the end), connecting the starting end of the beat signal Q ₂ (part of the cycle starting point), and the end of the beat signal Q _2, the beginning of the beat signal Q ₃ Connect with.
Such a connection can be said to be a process of switching the beat signal at the boundary point between one cycle and the next cycle, and is also a process of connecting the beat signals of each frequency band in ascending order of the frequencies of the corresponding frequency bands. It can be said that there is.

The target detection unit 152 Fourier transforms each composite signal generated by the signal synthesis unit 151, further arranges the Fourier transforms of a plurality of composite signals, Fourier transforms in the arranged direction, and detects the peak to detect the target TG. Calculate the distance to and the speed of the target TG.

Hereinafter, the conditions for properly connecting the beat signals in the above radar device RD will be described.

FIG. 5A is an enlargement of a part of FIG. 4A, and a reference numeral representing a frequency band and a period is added to a transmission signal, a reception signal, and a frequency difference. That is, the transmission signal of cycle k of the frequency band FC _m (k-th period) indicated by reference numeral S (m, k), the received signal having a period k of the frequency band FC _m is represented by R (m, k) , The beat signal of the period k of the frequency band FC _m is indicated by Q (m, k).

^{The instantaneous value s (m, k)} of the transmission signal having a period k of the frequency band FC _m is expressed by the following equation (2).

In equation (2)
t is the time,
α is the amplitude of the transmitted signal,
f _m is the chirp start frequency of the _mth frequency band FC m,
T is the length of the chirp cycle,
B is the modulation width of the transmitted signal, that is, the bandwidth of each frequency band.
Φ _{m and k} represent the initial phase of the chirp period k of the _mth frequency band FC m.

Assuming that the target TG is moving at a constant velocity v in the line-of-sight direction of the radar device RD, the instantaneous value r ^{(m, k)} of the received signal obtained by receiving the reflected wave at the target TG is as follows. It is expressed by the equation (3) of.

In equation (3), β is the amplitude of the received signal.
Further, δ is given by the following equation (4).

In equation (4), c is the speed of light.
Further, v is the speed of the target TG, and the direction away from the radar device RD is the positive direction.

In the formula (3), τ ₀ is the delay time of the received signal at time t = 0, and is represented by the following formula (5).

In equation (5), x ₀ represents the position of the target TG at time t = 0, that is, the distance from the radar device RD.

Before explaining the method of processing beat signals in a plurality of frequency bands in the present embodiment, generally, there is a phase between beat signals generated by using received signals received simultaneously in a plurality of frequency bands. Explain that continuity cannot be ensured.

The _m r _{(m r} is any one of 1 to M) the received signal _{_R (m} r, _k r) of a frequency band _{FC mr} period _{k r} with, the _m s (the _{m s} either from 1 M) phase difference between the transmission signal _{_S (m} s, _k s) of the frequency band _{FC ms} period _{k s,} i.e. the beat signal _{_{_{Q (m r, k r,}}} m s, k s) the instantaneous value of the phase of the following It is represented by the formula (6).

In equation (6), _{the value when mr} = m _s = m and _kr = k _s = k, that is, the transmission signal S (m, k) and the reception signal R having a period k of the mth frequency band. The instantaneous value of the phase of the beat signal Q (m, k) generated from (m, k) is expressed by the following equation (7).

As a comparative example, as shown in FIGS. 5A and 5B, a beat signal generated from a transmission signal S (m, k) and a reception signal R (m, k) having a period k of the mth frequency band. The end of Q (m, k) and the start of the beat signal Q (m + 1, k) generated from the transmission signal S (m + 1, k) and the reception signal R (m + 1, k) with the period k of the first m + 1 frequency band. Think about connecting with.
The end of the beat signal Q (m, k) is at the end of the cycle k, and the start of the beat signal Q (m + 1, k) is at the start of the cycle k.
The phase difference between the two beat signals at the connecting portion is expressed by the following equation (8).

Since δ = 1 when the target TG is stationary, the phase difference represented by the equation (8) becomes 0, and the phase continuity between the beat signals can be ensured.
When the target TG is moving, the phase difference represented by the equation (8) is not always 0 because the equation (8) includes the _{delay time τ 0.} That is, the continuity of the phase between the beat signals cannot be ensured.

On the other hand, in this embodiment, the connection is performed as follows. That is, as shown in FIGS. 5A and 5C, the beat signal Q (m) generated from the transmission signal S (m, k) and the reception signal R (m, k) having the period k of the mth frequency band. , K) is connected to the end of the beat signal Q (m + 1, k + 1) generated from the transmission signal S (m + 1, k + 1) and the reception signal R (m + 1, k + 1) having a period k + 1 in the mth frequency band. ..

The end of the beat signal Q (m, k) is at the end of the cycle k, and the start of the beat signal Q (m + 1, k + 1) is at the start of the cycle k + 1.
The phase difference between the two beat signals at the connecting portion is 0 as represented by the following equation (9).

In this way, since the phase difference between the two beat signals becomes 0, the phase continuity between the beat signals can be ensured even if the target TG is moving. As a result, high distance resolution can be realized without causing distortion, splitting, or the like at the peak of the Fourier transform for the synthesized signal.

Subsequently, a portion of the received signal that arrives with a delay in the next chirp cycle will be described with reference to FIG. 6A. The received signal that arrives with a delay means a received signal corresponding to the reflected wave that arrives with a delay.
FIG. 6A is a diagram similar to that of FIG. 5A, but shows the portion of the received signal that arrives with a delay in the next chirp cycle.
"The portion of the received signal that arrives late in the next chirp cycle" means the portion of the received signal corresponding to the transmitted signal transmitted in a certain cycle that is received in the next cycle of the above cycle. do.

For example, as shown in FIG. 6A, the delay time is Td, and a part R (m, k) of the received signal R (m, k) corresponding to the transmitted signal S (m, k) transmitted in the period k ( m, k) d is received in the next cycle k + 1. The reception signal R (m + 1, k + 1) having a period k + 1 of the frequency band FC _{m + 1} includes a part R (m) of the reception signal R (m, k) corresponding to the transmission signal S (m, k) transmitted in the period k. , K) It can also be said that d is included.

The received signal portion R (m, k) d is the reception processing by the receiver for the frequency band _{FC m + 1,} in the conversion unit for frequency band _{FC m + 1,} the frequency band _{FC m + 1} of the next period k + 1 of the transmitted signal It is mixed with S (m + 1, k + 1) to generate the start end portion of the beat signal Q (m + 1, k + 1) having the period k + 1. The above-mentioned " _{receiver for frequency band FC m + 1} " refers to receiver 132 if m = 1 and receiver 133 if m = 2, and "conversion for _{frequency band FC m + 1".} When m = 1, the “unit” refers to the conversion unit 142, and when m = 2, it refers to the conversion unit 143.
In FIG. 6B, such a starting end portion is indicated by the reference numeral Q (m, k) d, and the portion other than the starting end portion is indicated by the reference numeral Q (m + 1, k + 1) u.

In the case of a radar with a long maximum ranging distance, the maximum value of the delay time Td becomes long, and the continuity of the phase between the beat signals in the delay portion (the portion of the period Td in FIG. 6A) is also important.

^{The phase Δθ (m, k} ) at the end of the cycle of the beat signal Q (m, k) u generated from the transmission signal S (m, k) and the reception signal R (m, k) having the period k of the third frequency band. ^{, M, k)} (kT) and the received signal R (m, k) corresponding to the transmitted signal S (m, k), and the received signal R (m, k) d received during the period k + 1. ^{, Phase Δθ (m, k, m + 1, k + 1)} (kT) at the start of the cycle of the beat signal Q (m, k) d generated from the transmission signal S (m + 1, k + 1) having the cycle k + 1 in the frequency band of the third m + 1. ) Is expressed by the following equation (10).

_{F m} + B / 2 in the equation (10) is equal to the center frequency h _m _{of the frequency band FC m.}
In order to ensure the continuity of the phase between the above two beat signals, the phase difference given by the equation (10) needs to be an integral multiple of 2π.

For the phase difference given by equation (10) is an integral multiple of 2π, the product of the center frequency _{_{h m (= f m + B}} / 2) and the chirp period length T is an integer, the transmission signal S _It _{is sufficient that the phases φ m, k} at the start of the chirp of the period k of _{m and the phases φ m + 1, k + 1} at the start of the chirp of the period k + 1 of the transmission signal S _{m + 1} are equal to each other.

In order to continuously ensure the continuity of the phase between the beat signals, the phase difference given by Eq. (10) must be an integral multiple of 2π between all frequency bands and all periods. There is.
Therefore, the control device 100, as described above, the phase _{_{φ 1, k ~ φ 3,}} k the same in all cycles of the modulation width B, a length T of the period, the transmission signal _S 1 ~ _{S 3} By specifying the start frequencies f ₁ to f ₃ _{and the first phases φ 1, k} to φ _{3, k} of each period of the transmission signals S ₁ to S ₃ , the value of equation (10), that is, the beat signal Control is performed so that the phase difference at the start of the cycle is an integral multiple of 2π.

By performing such control, the continuity of the phase between the above two beat signals can be continuously ensured, and the peak of the Fourier transform can be obtained even for a long-distance moving target in which the delay time of the received signal becomes long. High distance resolution can be achieved without causing distortion or splitting.

Further, as described with reference to FIGS. 6 (a) and 6 (b), the portion _{of the received signal in the mth} frequency band FC m that arrives with a delay in the next chapter cycle is the adjacent third m + 1 signal. since it is necessary to convert the beat signal is received by the frequency band _{FC m + 1,} of the signal converter 140, conversion unit corresponding to the frequency band _{FC m + 1,} as shown in FIG. 6 (a), the frequency band _{FC m + 1} Not only that, it is necessary to configure it so that it can process a signal in _{the frequency range FE m + 1} _{from the lower end of the frequency band FC m + 1} to a frequency further lower by the frequency width Bd. "Converting unit corresponding to the frequency band _{FC m + 1"} above, a conversion unit for generating a beat signal _{Q m + 1} receives a transmission signal _{S m + 1} of the frequency band _{FC m + 1,} m points to the conversion unit 142 as long as 1 If m is 2, it means the conversion unit 143.

Further, in the signal receiving device 130, the receiving unit corresponding to _{the frequency band FC m + 1} _{has the frequency range FE m + 1} as the receiving frequency band, and is configured to be capable of receiving processing for the signal in the _{frequency range FE m + 1.} There is a need. The above "receiving unit corresponding to the frequency band FC m _{+ 1"} is a receiving unit corresponding to the converter which corresponds to the frequency band FC m _{+ 1,} m points to the receiving unit 132 if 1, if m is 2 Refers to the receiving unit 133.
The receiving unit 131 corresponding to the frequency band FC1 suffices to set the frequency band FC1 itself as the receiving frequency band.
“Letting a certain frequency range or a certain frequency band as a reception frequency band” means that reception processing can be performed on a signal in the frequency range or the frequency band.
In order to distinguish it from the reception frequency band, the frequency bands FC ₁ to FC ₃ may be referred to as a transmission frequency band.

The frequency width Bd is predetermined to be equal to or higher than the maximum beat frequency Qmax.
The maximum beat frequency Qmax is given by the following equation (11).

In equation (11), τ _max is the delay time corresponding to the maximum distance measurement distance.

Furthermore, the product of the length T of the sampling frequency f _S and chirp period of the beat signal in the A / D converters 81 to 83 may be set to be an integer. In other words, A / D converters 81 to 83 may be configured to perform sampling in such a condition is satisfied sampling frequency f _S. Then, during the continuous period, the phase difference at the start of the period of the received signal in each frequency band obtained from the reflected wave at the target which is stationary or moving at a constant speed becomes constant.

Hereinafter, a method in which the target detection unit 152 calculates the distance to the target TG and the speed of the target TG based on the plurality of synthetic signals CS generated as described above will be described.

First, the first Fourier transform is performed on each of the combined signals CS to generate a power spectrum with respect to the distance. An example of the result of the Fourier transform on one composite signal is shown in FIG.
The horizontal axis in FIG. 7, the distance to a corresponding frequency, the power can be specified distance from the frequency f _p of the peak.
A result similar to that shown in FIG. 7 (Fourier transform result) is obtained for each composite signal.

The results of Fourier transform on a plurality of synthesized signals generated within a certain period, DS (i), DS (i + 1), DS (i + 3), ... Are arranged on the time axis. Specifically, the result of each Fourier transform is arranged at a time point corresponding to the start of the beat signal located at the beginning of the corresponding composite signal. The result of such an arrangement is shown in FIG. 8 (a).
When the target TG is moving, the phase of the peak in the result of the Fourier transform shown in FIG. 8 (a) changes as shown in FIG. 8 (b).

Next, Fourier transform is performed for each frequency bin (BIN) of the frequency spectra DS (i), DS (i + 1), ... Shown in FIG. 8 (a).

An example of the result of the second Fourier transform is shown in FIG.
As shown in the figure, in the result of the second Fourier transform, a peak appears in the frequency bin with respect to the Doppler frequency. The speed of the target TG can be specified from this Doppler frequency.

FIG. 10 shows a processing procedure after receiving the reflected wave by the radar device RD shown in FIG.
In step ST1, a beat signal is generated. The process of step ST1 is performed by the signal converter 140.
In step ST2, a composite signal is generated by connecting the beat signals. The process of step ST2 is performed by the signal synthesis unit 151.

In step ST3, each synthesized signal is Fourier transformed.
In step ST4, the results are arranged in the above Fourier transform, and the Fourier transform is performed in the arranged direction.
In step ST5, the peak is detected to obtain the distance and speed.
The processing of steps ST3 to ST5 is performed by the target detection unit 152.

Various modifications can be added to the above embodiments.
For example, in the above embodiment, the number M of the frequency band is 3, but M may be 2 or 4 or more. In short, M may be 2 or more.
Further, in the above configuration, the chirp signal is an up chirp signal, but the chirp signal may be a down chirp signal.

Further, the above signal transmitter has a plurality of transmitters, and each transmitter is composed of an amplifier, a transmission / reception switch, and an antenna. If a set of amplifiers, a transmission / reception switch, and an antenna can cover a plurality of frequency bands as a whole, a signal transmission device may be configured by such a set of amplifiers, a transmission / reception switch, and an antenna.

Further, the above signal receiving device has a plurality of receiving units, and each receiving unit is composed of an antenna, a transmission / reception switch, and an amplifier. If a set of antennas, a transmission / reception switch, and an amplifier can cover a plurality of frequency bands as a whole, such a set of antennas, a transmission / reception switch, and an amplifier may form a signal receiver.

Further, in the above embodiment, the modulation width B of the charp signal is fixed. The modulation width B may be specified by the control device 100. In that case, a DDS3 capable of generating a chirp signal having a specified modulation width B may be used.

In short, the radar device
The first to M chirp signals of the first to M (M is an integer of 2 or more) transmission frequency bands having equal bandwidths and adjacent to each other and having continuous frequency changes are synchronized with each chirp cycle. A signal generator (110) that is repeatedly generated in
A signal transmitter (120) that transmits a first to M transmission wave corresponding to the first to M chirp signals repeatedly generated by the signal generator (110), and a signal transmitter (120).
The reflected waves generated by the reflection of the first to M transmission waves transmitted by the signal transmission device (120) at the target are the first to first transmission waves corresponding to the first to M transmission frequency bands, respectively. A signal receiving device (130) that receives in the reception frequency band of M and generates the first to M received signals, and
The distance from the first to M chirp signals generated by the signal generator (110) and the first to M received signals generated by the signal receiving device (130) to the target. A signal converter (140) that generates first to Mth beat signals having frequency components according to
The signal synthesizer (151) that connects the first to M beat signals generated by the signal conversion device (140) to each other at the boundary between the chirp cycles to generate one composite signal for each chirp cycle. )When,
A target detection unit (152) that calculates the distance to the target and the target speed from the plurality of synthetic signals sequentially generated by the signal synthesis unit (151) may be provided.

It is preferable that the frequency at the end of the chirp of the mth chirp signal and the frequency at the start of the chirp of the m + 1 chirp signal are equal.

It is preferable that the phase at the end of the chirp of the mth chirp signal and the phase at the start of the chirp of the m + 1 chirp signal are continuous.

The signal synthesizing unit (151) determines the termination of the beat signal generated from the m (m is any of 1 to M-1 in this case) chirp signal of the first to M chirp signals. It is preferable that the beat signals are connected by connecting the beat signals generated from the m + 1th chirp signal.

When the chirp signal is an up chirp signal, it is preferable that the _{beat signals of the first} to _Mth frequency bands FC1 to FCM are connected in ascending order of the frequencies of the corresponding frequency bands.
When the chirp signal is a down chirp signal, it is preferable that the _{beat signals of the first} to _Mth frequency bands FC1 to FCM are connected in descending order of the frequencies of the corresponding frequency bands.

Is the product is an integer with a center frequency of each frequency band of the first to _{M (h m = f m +} B / 2) and the chirp period length (T), the chirp of the first to the chirp signal of the M It is preferable that the starting phases (φ _{m, k} ) are equal to each other and are the same to each other between the chirp periods (k) before and after the phase.

The nth (n is any of 2 to M) reception frequency bands of the first to M reception frequency bands are extended by the beat frequency corresponding to the maximum ranging distance with respect to the corresponding transmission frequency band. It is preferable to have a specified frequency range.

If the chirp signal is an up chirp signal, the above extension is an extension from the lower limit of the corresponding transmission frequency band to a frequency lower by the beat frequency corresponding to the maximum distance measurement distance, and the chirp signal is a down chirp signal. If so, the above extension is an extension from the upper limit of the corresponding transmission frequency band to a frequency higher by the beat frequency corresponding to the maximum distance measurement distance.

The signal conversion device (140) has first to M A / D conversion units that A / D convert the first to M beat signals, respectively, and the first to M A / Ds. in the conversion unit, the sampling frequency (f _S) of the first to beat signal of the M and the chirp length of the period (T) and the product is an integer become as the a / D conversion of the first through M The unit is configured so that the phase difference at the start of the cycle of the received signal in each frequency band obtained from the reflected wave at the target that is stationary or moving at a constant speed is constant between continuous cycles. It is preferable to do so.

A part or all of the part other than the antenna of the radar device may be composed of a processing circuit.
For example, the functions of each part of the radar device may be realized by separate processing circuits, or the functions of a plurality of parts may be collectively realized by one processing circuit.
The processing circuit may be composed of hardware or software, that is, a programmed computer.
Of the functions of each part of the radar device, some may be realized by hardware and the other part may be realized by software.

FIG. 11 shows the hardware configuration of the computer 90 that realizes a part or all the functions of the part other than the antenna of the radar device.
In the illustrated example, the computer 90 has a processor 91 and a memory 92.
The memory 92 stores a program for realizing the functions of each part other than the antenna of the radar device.

The processor 91 uses, for example, a CPU (Central Processing Unit), a microprocessor, a microcontroller, a DSP (Digital Signal Processor), or the like.

The memory 92 includes, for example, a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable Lead Only Memory), an EEPROM (Electrically Memory Memory, etc.) Alternatively, a photomagnetic disk or the like is used.

The processor 91 and the memory 92 may be realized by an LSI (Large Scale Integration) integrated with each other.

The processor 91 realizes the function of the radar device by executing the program stored in the memory 92.
The program may be provided over a network or may be recorded and provided on a recording medium, such as a non-temporary recording medium. That is, the program may be provided, for example, as a program product.

The computer of FIG. 11 includes a single processor, but may include two or more processors.

As described above, according to the radar device of the embodiment, the phase continuity between the beat signals is ensured even for the moving target, and the peak of the Fourier transform is not distorted or split, and the distance resolution is high. Can be realized.

3 DDS (digital direct synthesis oscillator), 4 high frequency signal generator, 11 to 13 mixer, 21 to 23 amplifier, 31 to 33 transmission / reception switch, 41 to 43 antenna, 51 to 53 amplifier, 61 to 63 mixer, 71 to 73 Amplifier, 81-83 A / D converter, 100 control device, 102 reference signal generator, 110 signal generator, 120 signal transmitter, 121-123 transmitter, 130 signal receiver, 131-133 receiver, 140 signal Conversion device, 141-143 conversion unit, 150 signal processing device, 151 signal synthesis unit, 152 target detection unit.

Claims

The first to M chirp signals of the first to M (M is an integer of 2 or more) transmission frequency bands having equal bandwidths and adjacent to each other and having continuous frequency changes are synchronized with each chirp cycle. A signal generator that repeatedly generates signals and
A signal transmitting device that transmits a first to M transmission wave corresponding to the first to M chirp signals repeatedly generated by the signal generating device, and a signal transmitting device.
Reception of the first to M corresponding to the first to M transmission frequency bands, respectively, of the reflected wave generated by the reflection of the first to M transmission waves transmitted by the signal transmission device at the target. A signal receiver that receives in the frequency band and generates the first to M received signals, and
From the first to M chirp signals generated by the signal generator and the first to M received signals generated by the signal receiving device, frequency components corresponding to the distance to the target are obtained. A signal conversion device that generates the first to Mth beat signals to have, and
A signal synthesizing unit that connects the first to Mth beat signals generated by the signal conversion device to each other at boundaries between the chirp periods to generate one composite signal for each chirp period.
A radar device including a target detection unit that calculates a distance to a target and a target speed from a plurality of synthetic signals sequentially generated by the signal synthesis unit.
The signal synthesizing unit includes the termination of the beat signal generated from the m (m is any of 1 to M-1 in this case) chirp signal of the first to M chirp signals, and the m + 1 th chirp signal. The radar device according to claim 1, wherein the beat signals are connected by connecting the beat signals generated from the chirp signals.
The radar device according to claim 2, wherein the frequency at the end of the chirp of the mth chirp signal and the frequency at the start of the chirp of the m + 1 chirp signal are equal to each other.
The radar device according to claim 2 or 3, wherein the phase at the end of the chirp of the mth chirp signal and the frequency at which the phase at the start of the chirp of the m + 1 chirp signal are continuous are equal.
The radar device according to any one of claims 2 to 4, wherein the chirp signal is an up chirp signal.
The radar device according to any one of claims 2 to 4, wherein the chirp signal is a down chirp signal.
The product of the center frequency of each of the first to M frequency bands and the length of the chirp period is an integer.
The radar device according to any one of claims 1 to 6, wherein the phases of the first to M chirp signals at the start of chirp are equal to each other and are the same to each other between the chirp periods before and after the phase.
The nth (n is any of 2 to M) reception frequency bands of the first to M reception frequency bands are extended by the beat frequency corresponding to the maximum ranging distance with respect to the corresponding transmission frequency band. The radar device according to any one of claims 1 to 7, which has a specified frequency range.
The signal conversion device is
Each has a first to Mth A / D conversion unit that A / D converts the first to Mth beat signals.
The first to M A / D in the first to M A / D converters so that the product of the sampling frequency of the first to M beat signals and the length of the chirp period is an integer. The radar device according to any one of claims 1 to 8, wherein the D conversion unit is configured.