Radar signal processing device, radar signal processing method, radar signal processing program, and recording medium

Abstract

This radar signal processing device is provided with: a target detection unit that, by using transmission waves transmitted in a time division manner from a plurality of transmission antennas and reception signals from a plurality of reception antennas that received reflection waves from a target, obtains the distance to and the arrival angle relative to the target and the velocity of the target; an angle measurement compensation processing unit that corrects a spatial signal by using a phase element that depends on the azimuth angle relative to the target without the influence of a phase element due to the velocity of the target, and obtains an angle-compensated spatial signal; a velocity estimation unit that determines the presence or absence of velocity aliasing by using a processing result obtained from the angle-compensated spatial signal and obtains an estimated velocity of the target; a velocity compensation processing unit that corrects the spatial signal by using a phase element that depends on the velocity of the target without the influence of a phase element due to the azimuth angle relative to the target, and obtains a velocity-compensated spatial signal; and an angle measurement unit that performs angle measurement signal processing on the velocity-compensated spatial signal and obtains the azimuth angle relative to the target.

Description

Radar signal processing device, radar signal processing method, radar signal processing program, and recording medium

[0001] The present disclosure relates to a radar signal processing device, a radar signal processing method, a radar signal processing program, and a recording medium for a TDM-MIMO (TDM: Time Division Multiplexing; MIMO: Multiple-Input Multiple-Output) radar device.

[0002] In recent years, TDM-MIMO radar devices have been adopted for applications such as automotive radar devices due to their wide frequency resource and simple hardware. However, one issue with TDM-MIMO radar devices is that because the TDM-MIMO radar device switches over time, the velocity measurement range (Nyquist frequency) that can be measured by the radar device is reduced. Therefore, aliasing (also known as velocity ambiguity; hereinafter referred to as velocity ambiguity) occurs for targets moving at speeds beyond the velocity measurement range, which can lead to inaccurate estimation of the target velocity.

[0003] Prior art literature that focuses on this issue is exemplified by Patent Document 1. Patent Document 1 discloses a method for estimating a velocity without aliasing, based on the assumption that when the velocity of the target is within the velocity measurement range, the ideal corrected virtual array signal Sc is a curve with a single peak in the angle FFT, whereas when the velocity of the target is outside the velocity measurement range, the erroneous virtual array signal Sc is likely to be a curve with two peaks in the angle FFT.

[0004] Special table 2019-522220 publication

[0005] The data reproduction device disclosed in Patent Document 1 has a problem in that it is difficult to obtain the target velocity and the azimuth angle to the target with high accuracy when there is velocity ambiguity.

[0006] The present disclosure is intended to solve the above-mentioned problems, and aims to provide a radar signal processing device that can obtain the target speed over an expanded speed measurement range and the azimuth angle to the target with high accuracy even when there is speed ambiguity.

[0007] A radar signal processing device according to the present disclosure includes a target detection unit that obtains a distance to the target, an angle of arrival, and a speed of the target using received signals corresponding to incoming waves from the multiple receiving antennas that receive the reflected waves from the target when the transmitted waves are reflected by the target, and transmitted signals corresponding to the transmitted waves from the multiple transmitting antennas; an angle measurement compensation processing unit that estimates a phase element that depends on an azimuth angle with respect to the target, which is not affected by a phase element due to the speed of the target, for a spatial signal obtained by a combination of the multiple transmitting antennas and the multiple receiving antennas, corrects the spatial signal using the phase element that depends on the azimuth angle, and obtains an angle-compensated spatial signal that is not affected by a phase element that depends on the azimuth angle with respect to the target; and a velocity estimation unit that performs fast Fourier transform processing on the angle-compensated spatial signal obtained by the fast Fourier transform processing, determines whether or not there is aliasing of the velocity obtained by the target detection unit using the processing result obtained by the fast Fourier transform processing, and obtains an estimated velocity of the target from the velocity of the target obtained by the target detection unit based on the result of the determination; a velocity compensation processing unit that estimates a phase element that depends on the velocity of the target for the spatial signal, which is not affected by a phase element due to the azimuth angle with respect to the target, corrects the spatial signal using the velocity-dependent phase element, and obtains a velocity-compensated spatial signal that is not affected by a phase element that depends on the velocity with respect to the target; and an angle measurement unit that performs angle measurement signal processing on the velocity-compensated spatial signal obtained by the velocity compensation processing unit, and obtains the azimuth angle with respect to the target.

[0008] According to the present disclosure, even when there is velocity ambiguity, it is possible to obtain the velocity of a target with an expanded velocity measurement range and a highly accurate azimuth angle to the target.

[0009] FIG. 1 is a configuration diagram showing a radar signal processing device according to a first embodiment; FIG. 2 is an explanatory diagram schematically showing the relationship between the transmission waves and reception waves of a target and the transmission antenna and receiving antenna of the radar device; FIG. 3 is a schematic diagram of time switching of the transmission signal of the radar device according to the first embodiment; FIG. 4 is a flowchart showing the operation of the radar signal processing device according to the first embodiment; FIG. 5 is a configuration diagram showing the hardware configuration of the radar signal processing device according to the first embodiment; FIG. 6 is a configuration diagram showing the radar signal processing device according to a second embodiment; FIG. 7 is a flowchart showing the operation of the radar signal processing device according to the second embodiment; FIG. 8 is a configuration diagram showing the radar signal processing device according to a third embodiment; FIG. 9 is a flowchart showing the operation of the radar signal processing device according to the third embodiment;

[0010] Embodiment 1 A radar signal processing device 1 according to embodiment 1 will be described with reference to Figures 1 to 4. The radar signal processing device 1 according to embodiment 1 is a radar signal processing device applied to an on-board TDM-MIMO radar device mounted on a moving body such as an automobile or indoor mobility. The TDM-MIMO radar device (hereinafter simply referred to as radar device) has N transmitting antennas 2 as shown in Figure 2. １ ~2 ３ and M receiving antennas 3 １ ~3 ４ In addition to the radar signal processing device 1 that forms part of the receiving device, the radar system also includes a transmitting device (not shown), a control unit (not shown) that controls the transmitting device and the receiving device, and an overall control unit (not shown) that controls the entire radar system.

[0011] Note that M and N are plural numbers, and in the radar device to which the first embodiment is applied, N is 3 and M is 4, for example. １ ~2 ３ 3 elements, receiving antenna 3 １ ~3 ４ However, the number is not limited to four, and the number of transmitting antennas is not limited to two. １ ~2 ３ and receiving antenna 3 １ ~3 ４ Both may be a plurality of elements.

[0012] The transmitter has a transmitting antenna 2１ ~2 ３ The transmitted signal is a transmission wave (radio wave) Tx in time division order. １ ~Tx ３ The transmitter is a transmitter used in a commonly known in-vehicle TDM-MIMO radar device, and a detailed description thereof will be omitted. １ ~2 ３ The transmission waves transmitted in a time-division manner in a time series manner from the receiving antenna 3 are reflected by a target 100, which is an object, and the reflected waves from the target 100 are received by the receiving antenna 3. １ ~3 ４ Arrival wave (received wave) from Rx １ ~Rx ４ A received signal is generated that includes digital information according to the received signal.

[0013] The transmitter uses a commonly known method such as FMCW (Frequency Modulated Continuous Wave), Fast-Chirp, or Pulse Doppler, and has two transmitting antennas. １ ~2 ３ From the transmission wave Tx １ ~Tx ３ The receiving device radiates a receiving antenna 3. １ ~3 ４ The receiver processes the received signal.

[0014] In the radar device to which the first embodiment is applied, an up-chirp fast-chirp method will be described as an example. １ ~2 ３ are respectively chirp signals Tx whose frequencies increase over time while being switched in a time series order by the transmitter, as shown in FIG. １ -1, Tx ２ -1, Tx3 -1, Tx １ -2, ..., Tx １ -Nc, Tx ２ -Nc, Tx3-Nc are transmitted. Nc is the transmit antenna 2. １ ~2 ３ The chirp numbers for each are shown.

[0015] Chirp signal Tx １ -1, Tx １ -2, ..., Tx １ -Nc is transmitting antenna 2 １ The chirp signal Tx is a first, second, ..., Ncth transmitted wave. ２ -1, ..., Tx ２ -Nc is transmitting antenna 2 ２ The chirp signal Tx is the first, ..., Ncth transmitted wave. ３ -1, ..., Tx ３ -Nc is transmitting antenna 2 ３ , Nc-th transmission waves are transmitted from

[0016] Transmitting antenna 2 １、 Transmitting antenna 2 ２、 Transmitting antenna 2 ３ In this order, a chirp signal Tx is transmitted at a time interval (signal transmission interval) Tc. １ -nc, chirp signal Tx ２ -nc, chirp signal Tx ３ -nc is transmitted. Note that nc ranges from 1 to Nc. Considering the entire radar device, the signal transmission interval for transmitting chirp signals is Tc, but the number of transmitting antennas is 2. １、 Transmitting antenna 2 ２、 Transmitting antenna 2 ３ The signal transmission interval between signals transmitted from the same transmitting element is NTx×Tc, where NTx is the number of transmitting antennas, and the radar device to which the first embodiment is applied has three elements, as an example.

[0017] Transmitting antenna 2 １ ~2 ３ The elements of the adjacent transmitting antennas are arranged in an array with an element spacing ΔdTx of equal intervals or unequal intervals. １ ~2 ３ to the target 100 １ ~Tx ３ The angle of transmission is shown as θ in Fig. 2. θ corresponds to the azimuth angle of the target in the radar device.

[0018] Receiving antenna 3 １ ~3 ４are the incoming waves Rx reflected by the target 100, respectively. １ ~Rx ４ Receives the signal from receiving antenna 3. １ ~3 ４ The adjacent receiving antennas are arranged in an array with an element spacing ΔdRx of equal or unequal spacing. However, the element spacing ΔdRx is set to a spacing that does not cause estimation errors due to grating lobes when performing DOA (Direction Of Arrival) estimation processing of radio waves. １ ~3 ４ The incoming wave Rx from the target 100 at １ ~Rx ４ The angle of arrival of the beam is shown as θ in FIG.

[0019] The angle of departure and the angle of arrival are θ, and the transmitted wave Tx １ ~Tx ３ and the incoming wave Rx １ ~Rx ４ It is assumed that the target 100 is approaching (approaching) the radar device at a speed V, or is moving away (leaving) from the radar device at a speed V, and that the speed V of the target 100 may exceed the speed measurement range of the radar device.

[0020] In a radar device to which the first embodiment is applied, the maximum velocity value Vmax in the velocity measurement range is expressed by the following equation (1): Vmax = λ / (4NTx × Tc) (1) In equation (1), λ is the wavelength of the transmission wave, NTx is the number of transmitting antennas, and Tc is the signal transmission interval. As is clear from equation (1), the velocity measurement range narrows in proportion to the number of elements NTx.

[0021] Furthermore, the speed V of the target 100 that exceeds the speed measurement range of the radar device is expressed by the following equation (2): |V|>Vmax (2) The speed V of the target 100 is either positive or negative because the target 100 approaches the radar device at speed V or moves away from the radar device at speed V, so an absolute value is given.

[0022] When the velocity V of the target 100 exceeds the maximum velocity value Vmax in the velocity measurement range, attempting to determine the Doppler velocity of the target by FFT processing in the chirp signal direction (= FFT in the slow time direction, FFT: Fast Fourier Transform) results in aliasing of the Doppler velocity because the signal exceeds the Nyquist frequency. In a TDM-MIMO radar device, due to time-division transmission, signals for the target 100 approaching the radar device at velocity V or moving away from the radar device at velocity V are received with their phase rotated by the signal transmission interval Tc, and therefore velocity compensation processing is required to perform MIMO signal processing such as angle measurement signal processing.

[0023] This velocity compensation process generally uses the detected Doppler velocity, so if velocity compensation is performed using a signal with velocity aliasing, the phase rotation is not canceled out, resulting in an erroneous angle measurement in the subsequent MIMO signal processing. Therefore, in a TDM-MIMO radar device, it is necessary to accurately estimate the velocity V of the target 100. The radar signal processing device 1 according to the first embodiment can accurately estimate the velocity V of the target 100, even when the velocity V of the target 100 exceeds the maximum velocity Vmax in the velocity measurement range, thereby suppressing the occurrence of erroneous angle measurement.

[0024] 1, the radar signal processing device 1 according to the first embodiment includes a target detection unit 11, an angle measurement compensation processing unit 12, a speed estimation unit 13, a speed compensation processing unit 14, and an angle measurement unit 15. The target detection unit 11 detects a target from a receiving antenna 3. １ ~3 ４ Arrival wave from Rx １ ~Rx ４ The received signal is received by the transmitting antenna 2 at each set observation period. １ ~2 ３ Transmitted wave Tx from １ ~Tx ３ The radar device calculates the relative distance between the radar device and the target 100, the relative speed with respect to the target 100, and the direction of the target 100 using a transmission signal consisting of digital information according to the above.

[0025] In the following description, the relative distance and the direction of the target 100 may be referred to as a signal indicating the position of the target 100, and the relative distance, direction and relative velocity may be referred to as a signal for the target 100. Furthermore, the relative distance and relative velocity may be simply referred to as the distance and velocity.

[0026] The position and velocity are measured by a plurality of transmitting antennas 2 at a signal transmission interval NTx×Tc. １ ~2 ３ and multiple receiving antennas 3 １ ~3 ４ The number of combinations of N×M, i.e., 3×4 in the first embodiment, is calculated. The velocity may include velocity ambiguity (aliasing) if the velocity V of the target 100 exceeds the maximum velocity Vmax of the velocity measurement range. The position and velocity may be calculated using a method for calculating position and velocity that is generally known in radar devices, and detailed description thereof will be omitted.

[0027] For example, in the case of a transmission signal and a reception signal of the up-chirp Fast-Chirp method, the position and velocity are calculated using a plurality of transmission antennas 2 １ ~2 ３ and multiple receiving antennas 3 １ ~3 ４ For each combination, 2D-FFT processing is performed, a range-Doppler map is created by incoherent integration, and then the position and velocity of the target 100 are detected by CFAR (Constant False Alarm Rate) signal processing. Note that even if a method other than the Fast-Chirp method is used, it is sufficient as long as a reflected signal from the target 100 is obtained under conditions that match the format of the radar signal.

[0028] The target detection unit 11 uses information indicating the position and velocity of the target 100 to extract information about the target 100 from the range-Doppler map, and transmits the target 100 to the transmitting antenna 2. １ ~2 ３ and receiving antenna 3 １ ~3 ４ In the first embodiment, the spatial signals S extracted by the target detection unit 11 are the signals from the transmitting antenna 2. １~2 ３ 3 elements, receiving antenna 3 １ ~3 ４ In the case of 4×3 MIMO using four elements, it is expressed in matrix form by the following equation (3).

[0029]

[0030] In the above equation (3), the columns indicate transmission and the rows indicate reception. Each element in M ​​rows and N columns corresponds to the nth transmitting element (transmitting antenna 2 ｎ ) and the mth receiving element (receiving antenna 3 ｍ ), where n ranges from 1 to N and m ranges from 1 to M.

[0031] In the above equation (3), Φmn is a distance / azimuth angle phase element based on the distance to the target 100 and the azimuth angle θ to the target 100 at the nth transmitting element and the mth receiving element, and is expressed by the following equation (4): Φmn=exp(i2πΔdmn Sin(θ) / λ) (4) In equation (4), Δdmn is the distance from the receiving antenna 3 １ ~3 ４ The reference element can be selected from any combination of antenna elements.

[0032] In the above equation (3), Φvn is a velocity phase element resulting from the velocity V of the target 100 corresponding to the n-th transmitting element, and is expressed by the following equation (5): Φvn=exp(i2π2(n−1)V Tc / λ) (5)

[0033] In short, the target detection unit 11 is １ ~3 ４ Arrival wave from Rx １ ~Rx ４ The received signal and the transmitting antenna 2 １ ~2 ３ Transmitted wave Tx from １ ~Tx ３and a second function of obtaining a spatial signal S represented in a matrix format, where columns indicate transmission and rows indicate reception, and each element in the matrix has a range / azimuth phase element and a velocity phase element.

[0034] When angle measurement is performed using the distance / azimuth phase element Φmn by compensating the velocity phase element Φvn term in the spatial signal S from the Doppler frequency (velocity) using the spatial signal S obtained by the above equation (3), if the velocity V of the target 100 exceeds the maximum velocity Vmax of the velocity measurement range, the velocity may contain velocity ambiguity (aliasing). Therefore, if the velocity has velocity ambiguity, the velocity phase element Φvn may not be compensated correctly, and correct MIMO signal processing for the angle measurement may not be possible.

[0035] Therefore, in the first embodiment, the angle measurement compensation processing unit 12 performs the following processing. The angle measurement compensation processing unit 12 has a third function of performing processing to estimate the direction of arrival (DOA estimation) from the spatial signal S obtained by the above equation (3) without being affected by the velocity of the target 100, and provisionally estimating the azimuth angle θ relative to the target 100, and a fourth function of performing processing to cancel the distance / azimuth phase element Φmn from the spatial signal S obtained by the above equation (3) and leave only the velocity phase element Φvn, thereby obtaining an angle-compensated spatial signal Scmp, using the provisionally estimated azimuth angle θ that is the result of the DOA estimation processing and the element spacing Δdmn relative to the reference element. The angle measurement compensation processing unit 12 has an azimuth angle estimating unit 12a and a spatial signal compensating unit 12b, with the azimuth angle estimating unit 12a performing the third function and the spatial signal compensating unit 12b performing the fourth function.

[0036] That is, by having the third and fourth functions, the angle measurement compensation processor 12 estimates a phase element that depends on the angle of arrival θ of the target 100 without being influenced by a phase element due to the velocity V of the target 100, and then corrects the spatial signal S obtained by the above equation (3) using the phase element that depends on the angle of arrival θ to obtain an angle-compensated spatial signal Scmp. In short, the angle measurement compensation processor 12 estimates the range / azimuth phase element Φmn and performs processing to cancel the range / azimuth phase element Φmn from the spatial signal S obtained by the above equation (3) and leave only the velocity phase element Φvn, thereby obtaining an angle-compensated spatial signal Scmp that is not influenced by the angle of arrival θ with respect to the target 100.

[0037] The third function of the angle measurement compensation processor 12 will now be described. The angle measurement compensation processor 12 obtains a reception correlation matrix R shown in the following equation (6) for the spatial signal S obtained by the above equation (3). This processing is for provisionally estimating a phase element that depends on the arrival angle θ of the target 100 without being affected by a phase element due to the velocity V of the target 100.

[0038]

[0039] As can be seen from equation (6) above, the velocity phase element Φvn is cancelled out during correlation matrix calculation, leaving only the range / azimuth phase element Φmn in the reception correlation matrix R. Therefore, regardless of the presence or absence of velocity ambiguity, the DOA estimation process can be performed using the reception correlation matrix R to provisionally obtain the azimuth angle θ relative to the target 100.

[0040] Therefore, the angle measurement compensation processing unit 12 uses the reception correlation matrix R to perform DOA estimation processing using a signal processing method such as DBF (digital beamforming), Capon's method, MUSIC (Multiple Signal Classification) method, or ESPRIT (Estimation of Signal Parameter via Rotational Invariance Techniques) method, and provisionally estimates the azimuth angle (arrival angle) θ with respect to the target 100. The provisionally estimated azimuth angle θ is calculated by the reception antenna 3. １ ~3 ４Since the direction of arrival is obtained by estimating the direction of arrival using the array, it is not affected by phase rotation due to the velocity V of the target 100, and therefore the direction (arrival angle θ) relative to the target 100 can be estimated with high accuracy.

[0041] The angle measurement compensation processor 12 may also obtain the azimuth angle θ with respect to the target 100 to be provisionally estimated by the following method. That is, the first column of the spatial signal S obtained by the above equation (3) contains only Φv1 as a velocity phase element, and the azimuth angle (arrival angle) θ with respect to the target 100 can be estimated using only the signal obtained by extracting only the first column, regardless of whether or not velocity ambiguity exists. Therefore, the angle measurement compensation processor 12 performs DOA estimation processing using the signal shown in the first column of the spatial signal S obtained by the above equation (3) and a signal processing method such as angle FFT, DBF, Capon's method, MUSIC method, or ESPRIT method, and provisionally estimates the result of the DOA estimation processing as the azimuth angle θ with respect to the target 100. The azimuth angle θ obtained by this method is also not affected by phase rotation due to the velocity V of the target 100, and therefore can be provisionally estimated as the direction (arrival angle θ) with high accuracy with respect to the target 100.

[0042] In short, as a third function, the angle measurement compensation processor 12 performs DOA estimation processing from the spatial signal S obtained by the above equation (3) without the influence of the velocity phase element Φvn, and tentatively estimates the azimuth angle θ relative to the target 100. The fourth function of the angle measurement compensation processor 12 is processed as follows: Using the azimuth angle θ estimated by the third function and the element spacing Δdmn with respect to the reference element, the angle measurement compensation processor 12 performs processing to cancel the distance / azimuth phase element Φmn from the spatial signal S obtained by the above equation (3) and leave only the velocity phase element Φvn, thereby obtaining an angle-compensated spatial signal Scmp that is not influenced by the azimuth angle θ relative to the target 100, as shown in the following equation (7), that is, an angle-compensated spatial signal Scmp that is not influenced by the phase element due to the azimuth angle relative to the target 100.

[0043]

[0044] In the above equation (7), when we look at the row direction, the signal transmitted from transmitting antenna 2 sampled at the signal transmission interval Tc is １ ~2 ３Since the velocity phase element Φvn is due to the velocity V of the target 100 corresponding to the velocity phase element Φvn, it is possible to estimate the phase rotation, including FFT processing. １ ~3 ４ Corresponds to.

[0045] The velocity estimation unit 13 estimates the velocity V of the target 100 using the angle-compensated spatial signal Scmp in which the range / azimuth phase element Φmn obtained from the angle measurement compensation processing unit 12 has been cancelled. The velocity estimation unit 13 performs FFT processing on the angle-compensated spatial signal Scmp in the transmitting antenna direction (row vector direction), thereby making it possible to calculate the maximum velocity Vmax_ex in the velocity measurement range of the radar device using the following equation (8).

[0046] That is, by using the angle-compensated spatial signal Scmp, the velocity estimation unit 13 can expand the estimation of the velocity V of the target 100 from the maximum velocity value Vmax of the velocity measurement range for the velocity Vamb of the target 100 calculated by the target detection unit 11 to the maximum velocity value Vmax_ex of the velocity measurement range, and further expand the resolution for estimating the velocity V of the target 100. Vmax_ex=λ / (4Tc) (8)

[0047] The velocity estimation unit 13 has a fifth function of performing FFT processing on the angle-compensated spatial signal Scmp in the direction of the transmitting antenna to obtain a maximum value Vp of the FFT processing result, and a sixth function of using the maximum value Vp of the FFT processing result to obtain an estimated velocity V. The velocity estimation unit 13 has an FFT processing unit 13a and an estimation unit 13b, with the FFT processing unit 13a performing the fifth function and the estimation unit 13b performing the sixth function.

[0048] The FFT processing by the fifth function in the velocity estimation unit 13 may calculate the maximum value Vp of the FFT processing result by performing FFT processing on velocity phase elements extracted from one row of the compensated spatial signal Scmp in the transmitting antenna direction, or may calculate the maximum value Vp of the FFT processing result by averaging each column of the angle-compensated spatial signal Scmp and performing FFT processing on the velocity phase elements in each averaged column in the transmitting antenna direction, or may further calculate the maximum value Vp of the FFT processing result by performing FFT processing on the velocity phase elements in each row of the angle-compensated spatial signal Scmp in the transmitting antenna direction and averaging the processed results.

[0049] The speed is estimated by FFT processing in the speed estimation unit 13. １ ~2 ３ Therefore, in the sixth function, the velocity estimation unit 13 uses the maximum value Vp of the FFT processing result obtained by the FFT processing by the fifth function to determine whether or not velocity aliasing occurs and whether the aliasing is positive or negative, and estimates the estimated velocity V of the target 100 using the velocity Vamb of the target 100 calculated by the target detection unit 11.

[0050] The velocity estimation unit 13 uses the maximum value Vp of the FFT processing result obtained by the fifth function to determine whether or not velocity aliasing occurs and whether the aliasing is positive or negative, using the following method. That is, the velocity estimation unit 13 determines that the maximum value Vp of the FFT processing result is in the direction of positive velocity aliasing if the relationship between the maximum value Vp of the FFT processing result, the maximum velocity Vmax (=λ / (4NTx×Tc)) of the velocity measurement range shown in the above equation (1) for the velocity Vamb of the target 100 calculated by the target detection unit 11, and the maximum velocity Vmax_ex (=λ / (4Tc)) of the velocity measurement range shown in the above equation (8) for the result of FFT processing of the angle-compensated spatial signal Scmp in the transmitting antenna direction satisfies the relationship shown in the following equation (9), determines that the maximum value Vp of the FFT processing result is in the direction of negative velocity aliasing if the relationship shown in the following equation (10) satisfies the relationship shown in the following equation (10), and determines that the maximum value Vp of the FFT processing result does not have positive or negative aliasing in the velocity if the relationship shown in the following equation (11) satisfies the relationship shown in the following equation (11).

[0051] That is, the velocity Vamb of the target 100 calculated by the target detection unit 11 is found within a velocity measurement range in which the maximum velocity value is the maximum velocity value Vmax. Therefore, the velocity estimation unit 13 can determine whether or not the velocity is aliasing and whether the aliasing is positive or negative depending on which of the following relational expressions (9) to (12) the maximum value Vp of the FFT processing result satisfies:

[0052] Vmax<Vp≦Vmax_ex (9) -Vmax_ex≦Vp<-Vmax (10) -Vmax<Vp<Vmax (11)

[0053] When the maximum value Vp of the FFT processing result satisfies the relationship of the above equation (9), the speed estimation unit 13 can calculate the estimated speed V of the target 100 using the following equation (12): V = Vamb + 2Vmax (12) In other words, the estimated speed V of the target 100 is calculated by adding twice the maximum speed Vmax of the speed measurement range for the speed Vamb to the speed Vamb of the target 100 calculated by the target detection unit 11.

[0054] When the maximum value Vp of the FFT processing result satisfies the relationship of the above equation (10), the speed estimation unit 13 can calculate the estimated speed V of the target 100 using the following equation (13): V = Vamb - 2Vmax (13) In other words, the estimated speed V of the target 100 is set to a value obtained by subtracting twice the maximum speed Vmax in the speed measurement range for the speed Vamb from the speed Vamb (negative value) of the target 100 calculated by the target detection unit 11.

[0055] When the maximum value Vp of the FFT processing result satisfies the relationship of the above equation (11), the speed estimation unit 13 can calculate the estimated speed V of the target 100 by the following equation (14): V=Vamb (14)

[0056] That is, the estimated speed V of the target 100 is set to the speed Vamb of the target 100 calculated by the target detection unit 11. When performing FFT processing on the angle-compensated spatial signal Scmp in the transmitting antenna direction, the speed estimation unit 13 may perform discriminative processing to interpolate the roughness of the FFT processing result and output it.

[0057] In short, the velocity estimation unit 13 performs FFT processing on the angle-compensated spatial signal Scmp, determines whether or not there is aliasing of the velocity Vamb obtained by the target detection unit 11 using the processing result Vp obtained by the FFT processing, and obtains an estimated velocity V of the target 100 from the velocity Vamb obtained by the target detection unit 11 based on the result of this determination. The estimated velocity V of the target 100 obtained by the velocity estimation unit 13 is output as the velocity V of the target.

[0058] The maximum value of the estimated velocity V of the target 100 is the maximum velocity value Vmax_ex in the velocity measurement range shown in the above equation (8) for the result of FFT processing of the angle-compensated spatial signal Scmp in the transmitting antenna direction, so the problem of velocity ambiguity is resolved.

[0059] The velocity compensation processing unit 14 estimates a phase element dependent on the velocity V of the target 100 without being affected by a phase element due to the arrival angle θ of the target 100, and then corrects the spatial signal S obtained by the above equation (3) using the phase element dependent on the velocity V to obtain a velocity-compensated spatial signal Svcmp. In the first embodiment, the estimated velocity V of the target 100 estimated by the velocity estimating unit 13 is used to compensate the velocity phase element Φvn for the spatial signal S obtained by the above equation (3), that is, a process is performed to cancel the velocity phase element Φvn from the spatial signal S and leave only the range / azimuth phase element Φmn, thereby obtaining a velocity-compensated spatial signal Svcmp shown in the following equation (15).

[0060] At this time, the velocity phase element Φvn for the spatial signal S is compensated using the estimated velocity V of the target 100 estimated by the velocity estimation unit 13, so that the velocity phase element Φvn of the spatial signal S can be correctly compensated and a velocity-compensated spatial signal Svcmp can be correctly obtained. The velocity compensation processing unit 14 compensates for phase rotation of the velocity Vamb of the target 100 obtained by the target detection unit 11 using the estimated velocity V of the target 100.

[0061]

[0062] In the above equation (15), the row direction is the signal transmitted from the transmitting antenna 2 sampled at the signal transmission interval Tc. １ ~2 ３The distance and azimuth phase elements Φmn are due to the distance and azimuth angle relative to the target 100 corresponding to the target 100, and the column direction is the receiving antenna 3 １ ~3 ４ As shown in the above equation (15), the velocity-compensated spatial signal Svcmp is a spatial signal that is not affected by the velocity V relative to the target 100 and that contains only the range / azimuth phase element Φmn, by canceling out the velocity phase element Φvn from the spatial signal S obtained by the above equation (3).

[0063] The angle measurement unit 15 estimates the azimuth angle θ of the target using the velocity-compensated spatial signal Svcmp in which the velocity phase element Φvn obtained from the velocity compensation processing unit 14 has been cancelled. The angle measurement unit 15 obtains a high-resolution angle measurement value, that is, the azimuth angle (arrival angle) θ with respect to the target 100, by MIMO signal processing of the velocity-compensated spatial signal Svcmp using an angle measurement signal processing method such as angle FFT, DBF, or a super-resolution signal processing method such as the MUSIC method. The azimuth angle θ with respect to the target 100 obtained by the angle measurement unit 15 is output as the azimuth angle θ of the target.

[0064] Next, the operation of the radar signal processing device 1 according to the first embodiment will be described with reference to the flowchart shown in FIG. １ ~3 ４ Arrival wave from Rx １ ~Rx ４ A received signal consisting of digital information corresponding to the received signal and a transmitting antenna 2 １ ~2 ３ Transmitted wave Tx from １ ~Tx ３ The distance and angle of arrival (azimuth angle) of the target 100 and the velocity of the target 100 are calculated using a transmission signal consisting of digital information according to the above.

[0065] Step ST1 is a target signal detection step for a signal for the target 100. In step ST1, the target detection unit 11 uses the calculated distance and angle of arrival (indicating the position of the target 100) for the target 100 and the velocity of the target 100 to obtain a spatial signal S shown in the above equation (3) which is expressed in a matrix format, with columns indicating transmission and rows indicating reception, and each element in the matrix having a range / azimuth phase element and a velocity phase element. Step ST1 is also a step for acquiring the spatial signal S for the target 100.

[0066] In step ST2, the azimuth angle estimating unit 12a in the angle measurement compensation processing unit 12 performs a direction of arrival (DOA estimation) process on a signal having a distance / azimuth angle phase element and a velocity phase element for the target 100, which is the spatial signal S in the first embodiment, without being affected by the velocity of the target 100, and provisionally estimates the azimuth angle θ for the target 100. １ ~3 ４ This is a DOA estimation processing step in which the azimuth angle θ relative to the target 100 is tentatively estimated using the array.

[0067] In step ST3, the spatial signal compensation unit 12b in the angle measurement compensation processing unit 12 obtains an angle-compensated spatial signal Scmp in which the range / azimuth angle phase element Φmn is canceled out using the azimuth angle θ obtained by the azimuth angle estimation unit 12a for the spatial signal S for the target 100. Step ST3 is a step for obtaining an angle-compensated spatial signal Scmp in which the range / azimuth angle phase element Φmn is canceled out. Steps ST2 and ST3 together constitute an angle-of-arrival compensation step in which the angle measurement compensation processing unit 12 obtains an angle-compensated signal in which the range / azimuth angle phase element Φmn is canceled out from a signal having the range / azimuth angle phase element Φmn and the velocity phase element Φvn.

[0068] In step ST4, the FFT processing unit 13a in the velocity estimation unit 13 performs FFT processing on the angle-compensated signal, in the first embodiment, the angle-compensated spatial signal Scmp, and the estimation unit 13b uses the FFT processing result to determine whether aliasing occurs with respect to the velocity Vamb of the target 100 calculated by the target detection unit 11. Step ST4 is an aliasing presence / absence determination step in which a determination is made as to whether aliasing occurs with respect to the velocity Vamb of the target 100 calculated by the target detection unit 11.

[0069] In step ST5, the estimation section 13b in the speed estimation section 13 obtains an estimated speed of the target 100 from the speed Vamb of the target 100 based on the determination of the presence or absence of a return, and outputs the estimated speed as the speed V of the target.

[0070] That is, if the processing result by the FFT processing unit 13a exceeds the positive value of the maximum velocity Vmax in the velocity measurement range for the velocity Vamb of the target 100, the estimation unit 13b determines that positive aliasing has occurred, and calculates a value obtained by adding twice the maximum velocity Vmax to the velocity Vamb of the target 100 as the estimated velocity V of the target 100; if the processing result by the FFT processing unit 13a is less than the negative value of the maximum velocity Vmaxb in the velocity measurement range for the velocity Vam of the target 100, the estimation unit 13b determines that negative aliasing has occurred, and calculates a value obtained by subtracting twice the maximum velocity Vmax from the velocity Vamb of the target 100 (negative value) as the estimated velocity V of the target 100; and if the processing result by the FFT processing unit 13a is between the positive and negative values ​​of the maximum velocity Vmax in the velocity measurement range for the velocity Vamb of the target 100, the estimation unit 13b determines that aliasing has not occurred, and sets the velocity Vamb of the target 100 as the estimated velocity V of the target 100.

[0071] Steps ST4 and ST5 together are a speed acquisition step for determining whether or not there is a return for the speed Vamb of the target 100, and for obtaining an estimated speed V of the target 100 from the speed Vamb of the target 100 based on the result of the determination.

[0072] In step ST6, the velocity compensation processing unit 14 obtains a velocity-compensated spatial signal Svcmp in which the velocity phase element Φvn is cancelled out from a signal having a range / azimuth phase element and a velocity phase element for the target 100, which is the spatial signal S in the first embodiment, using the estimated velocity V of the target 100 obtained by the velocity estimating unit 13. Step ST6 is a velocity compensation step in which the velocity compensation processing unit 14 obtains a velocity-compensated signal in which the velocity phase element Φvn is cancelled out from the signal having the range / azimuth phase element Φmn and the velocity phase element Φvn.

[0073] In step ST7, the angle measurement unit 15 obtains an azimuth angle (arrival angle) θ for the target 100 by MIMO signal processing using an angle measurement signal processing technique using the velocity compensated signal. Step ST7 is an angle measurement step for obtaining the azimuth angle θ for the target 100. The position of the target 100 is estimated based on the azimuth angle θ for the target 100 obtained in step ST7 and the distance to the target 100 obtained in step ST1, and the estimated position of the target 100 is output.

[0074] The radar signal processing device 1 according to the first embodiment, which includes a target detection unit 11, an angle measurement compensation processing unit 12, a velocity estimation unit 13, a velocity compensation processing unit 14, and an angle measurement unit 15, is realized by a hardware configuration using a computer, and as shown in FIG. 5 , includes a CPU (Central Processing Unit) 1A, a large-capacity semiconductor memory (RAM: Random Access Memory) 1B, a storage device (ROM: Read Only Memory) 1C such as a non-volatile storage device such as a hard disk device or an SSD device, an input interface unit 1D, an output interface unit 1E, and a signal path (bus) 1F.

[0075] The CPU 1A controls and manages the RAM 1B, the ROM 1C, the input interface section 1D, and the output interface section 1E. The CPU 1A loads programs stored in the ROM 1C into the RAM 1B, and executes various processes based on the programs loaded into the RAM.

[0076] The target detection unit 11, angle measurement compensation processing unit 12, velocity estimation unit 13, velocity compensation processing unit 14, and angle measurement unit 15 are components that represent functions executed by the CPU 1A based on programs stored in the ROM 1C and loaded into the RAM 1B. The signal path 1F is a bus that interconnects the CPU 1A, RAM 1B, ROM 1C, input interface unit 1D, and output interface unit 1E.

[0077] The programs stored in the ROM 19 and executed by the CPU 18 include a target signal detection procedure for acquiring the distance, angle of arrival, and velocity of the target using received signals corresponding to the incoming waves from the multiple receiving antennas that receive the reflected waves from the target when the transmitted waves transmitted in a time-division manner from the multiple transmitting antennas are reflected by the target, and transmitted signals corresponding to the transmitted waves from the multiple transmitting antennas; an angle of arrival compensation procedure for acquiring an angle-compensated signal in which the distance and azimuth phase elements are cancelled out from a signal having a distance and azimuth phase element and a velocity phase element obtained by combining the multiple transmitting antennas and the multiple receiving antennas; a velocity acquisition procedure for performing fast Fourier transform processing on the angle-compensated signal, determining whether or not the target velocity is aliased using the processing result obtained by the fast Fourier transform processing, and acquiring an estimated velocity of the target from the velocity of the target based on the determination result; a velocity compensation procedure for acquiring a velocity-compensated signal in which the velocity phase element is cancelled out from the signal having the distance and azimuth phase element and the velocity phase element; and an angle measurement procedure for performing signal angle measurement processing on the velocity-compensated signal to acquire the azimuth angle of the target.

[0078] In the radar signal processing device 1 according to the first embodiment, the velocity estimation unit performs fast Fourier transform processing on the angle-compensated spatial signal obtained by the angle measurement compensation processing unit, which is not affected by a phase element that depends on the azimuth angle relative to the target, determines whether or not there is velocity aliasing using the processing result obtained by the fast Fourier transform processing, and obtains an estimated velocity of the target from the velocity of the target based on the result of the determination. The angle measurement unit performs angle measurement signal processing on the velocity-compensated spatial signal obtained by the velocity compensation processing unit, which is not affected by a phase element that depends on the velocity relative to the target, to obtain the azimuth angle relative to the target. Therefore, even when there is velocity ambiguity, it is possible to obtain the velocity of the target with an expanded velocity measurement range and the azimuth angle relative to the target with high accuracy.

[0079] Embodiment 2 A radar signal processing device 1 according to embodiment 2 will be described with reference to Figures 6 and 7. The radar signal processing device 1 according to embodiment 2 is the same as the radar signal processing device 1 according to embodiment 1 except for the method of signal compensation in the angle measurement compensation processing unit 12. Therefore, the following description will focus on signal compensation in the angle measurement compensation processing unit 12A, which corresponds to the angle measurement compensation processing unit 12 in embodiment 1. Note that in Figures 6 and 7, the same reference numerals as those shown in Figures 1 to 5 indicate the same or corresponding parts.

[0080] The angle measurement compensation processing unit 12A has an azimuth angle estimating unit 12a and a signal compensating unit 12c. The azimuth angle estimating unit 12a performs the same function as the third function performed by the azimuth angle estimating unit 12a in the radar signal processing device 1 according to embodiment 1. The signal compensating unit 12c performs the same function as the fourth function performed by the spatial signal compensating unit 12b in the radar signal processing device 1 according to embodiment 1. In short, the angle measurement compensation processing unit 12A obtains an angle-compensated signal that is not affected by the arrival angle θ with respect to the target 100.

[0081] The signal compensation unit 12c calculates the azimuth angle θ obtained by the azimuth angle estimation unit 12a and the received signal from the receiving antenna 3 １ ~3 ４ The element spacing ΔdRx is used to determine the receiving antenna 3 １ ~3 ４The received signal for which phase compensation is performed is a signal having a distance / azimuth phase element Φmn corresponding to the distance to the target 100 and the velocity phase element Φvn, since the distance to the target 100 has been obtained by the target detection unit 11.

[0082] The signal corresponding to the distance to the target 100 is received by the receiving antenna 3 １ ~3 ４ Each signal has (Nc x NTx) elements. Nc is the number of transmitting antennas. １ ~2 ３ is the number of chirps for each transmit antenna, and NTx is the number of transmit antennas for each transmit antenna. １ ~2 ３ The angle compensation processing unit 12A obtains an angle-compensated signal from the entire received signal, that is, a signal having (Nc×NTx×NRx) elements, by the azimuth angle estimation unit 12a and the signal compensation unit 12c. NRx is the number of elements of the receiving antenna 3. １ ~3 ４ is the number of

[0083] The signal compensator 12c performs phase compensation processing on the extracted signal having the distance / azimuth phase element Φmn corresponding to the distance to the target 100 and the velocity phase element Φvn, using the estimated azimuth angle θ, which is the result of the DOA estimation processing obtained by the azimuth angle estimator 12a, to obtain an angle-compensated spatial signal. By using the signal extracted corresponding to the distance to the target 100, the signal compensation range of the phase compensation processing is expanded to include the signal extracted at the distance to the target 100.

[0084] The speed estimation unit 13 performs FFT processing on the signal angle-compensated by the angle measurement compensation processing unit 12A, and the estimation unit 13b uses the FFT processing result to determine whether or not the target 100 has a speed Vamb calculated by the target detection unit 11. The angle measurement compensation processing unit 12A performs phase compensation on the entire received signal, and the speed estimation unit 13 performs FFT processing on the entire phase-compensated received signal, so the speed measurement range is expanded by the signal transmission interval Tc at which the chirp signal is transmitted. １ ~2 ３The observation time increases to {(N+NTx-1)×Tc} by the number NTx of the frequencies, improving the frequency resolution.

[0085] In addition, transmitting antenna 2 １ ~2 ３ However, instead of being transmitted at equal intervals, a time period during which transmission stops may be provided after the transmission signal, or the transmission intervals may be unequal. In such cases, the Doppler frequency may be calculated by FFT processing or DFT (discrete Fourier transform) processing with zero padding according to the transmission interval of the transmission signal.

[0086] The estimated speed V of the target 100 obtained by the speed estimation unit 13 is output as the target speed V. The estimated speed V of the target 100 obtained by the speed estimation unit 13 is also used by the speed compensation processing unit 14, and the azimuth angle θ with respect to the target 100 obtained by the angle measurement unit 15 is output as the azimuth angle θ of the target.

[0087] Next, the operation of the radar signal processing device 1 according to embodiment 2 will be described with reference to the flowchart shown in Fig. 7. The target signal detection step ST1 and the DOA estimation processing step ST2 are the same as the target signal detection step ST1 and the DOA estimation processing step ST2 in the radar signal processing device 1 according to embodiment 1.

[0088] In step ST3a, the signal compensation unit 12c in the angle measurement compensation processing unit 12A calculates the azimuth angle θ obtained by the azimuth angle estimation unit 12a and the received signal from the receiving antenna 3 １ ~3 ４ The element spacing ΔdRx is used to determine the receiving antenna 3 １ ~3 ４ Step ST3a is a step of performing phase compensation on the entire received signal in accordance with the incoming waves from receiving antenna 3 to obtain an angle-compensated signal. Steps ST2 and ST3a are combined to form an angle-of-arrival compensation step in which angle compensation processing unit 12A obtains an angle-compensated signal from the entire received signal, that is, a signal having (Nc x NTx x NRx) elements. NRx is the number of elements of receiving antenna 3. １ ~3 ４ is the number of

[0089] In step ST4a, the FFT processing unit 13a in the velocity estimation unit 13 performs FFT processing on the angle-compensated signal in the transmitting antenna direction (row direction), and the estimation unit 13b uses the FFT processing result to determine whether aliasing occurs with respect to the velocity Vamb of the target 100 calculated by the target detection unit 11. Step ST4a is an aliasing presence / absence determination step in which a determination is made as to whether aliasing occurs with respect to the velocity Vamb of the target 100 calculated by the target detection unit 11.

[0090] In step ST3a, the entire received signal is phase-compensated, and in step ST4a, FFT processing is performed on the entire phase-compensated received signal, so the velocity measurement range is expanded by the signal transmission interval Tc at which the chirp signal is transmitted. １ ~2 ３ The observation time increases by the number NTx of the signals to {(N+NTx-1)×Tc}, improving the frequency resolution.

[0091] Step ST5, velocity compensation step ST6, and angle measurement step ST7 are the same as step ST5, velocity compensation step ST6, and angle measurement step ST7 in the radar signal processing device 1 according to embodiment 1. Step ST4a and step ST5 together constitute a velocity acquisition step for determining whether or not there is a return for the velocity Vamb of the target 100, and for obtaining an estimated velocity V of the target 100 from the velocity Vamb of the target 100 based on the determination result.

[0092] Similar to the radar signal processing device 1 according to the first embodiment, the hardware configuration of the radar signal processing device 1 according to the second embodiment is realized by a computer including a CPU 1A, a RAM 1B, a ROM 1C, an input interface unit 1D, an output interface unit 1E, and a signal path (bus) 1F, as shown in FIG. 5 .

[0093] As with the radar signal processing device 1 according to the first embodiment, the radar signal processing device 1 according to the second embodiment obtains the velocity V of the target 100 and the azimuth angle θ with respect to the target 100 with an expanded velocity measurement range by separately estimating a phase element that depends on the azimuth angle θ with respect to the target 100 and a phase element that depends on the velocity Vamb of the target 100. Therefore, even when there is velocity ambiguity, it is possible to obtain the velocity of the target with an expanded velocity measurement range and the azimuth angle with high accuracy with respect to the target.

[0094] Embodiment 3 A radar signal processing device 1 according to embodiment 3 will be described with reference to Figures 8 and 9. The radar signal processing device 1 according to embodiment 3 is the same as the radar signal processing device 1 according to embodiment 1 except that it includes a target number detection unit 16 that detects the number of targets 100. Therefore, the description will focus on the target number detection unit 16. Note that in Figures 8 and 9, the same reference numerals as those shown in Figures 1 to 5 indicate the same or corresponding parts.

[0095] The target number detection unit 16 has a reception correlation matrix processing unit 16 a, an eigenvalue decomposition unit 16 b, and a target number determination unit 16 c. The reception correlation matrix processing unit 16 a obtains the reception correlation matrix R shown in the above equation (6) using the spatial signal S obtained by the target detection unit 11 using the above equation (3), and performs spatial averaging processing on the reception correlation matrix R.

[0096] The reception correlation matrix processing unit 16a is a receiving antenna 3 １ ~3 ４ If the number of elements is more than three, the receiving antenna 3 １ ~3 ４Alternatively, a spatially averaged reception correlation matrix may be obtained by performing forward spatial averaging, which divides the signal order of the received signals into subarrays and calculates the average of multiple reception correlation matrices R created for each subarray, or by performing forward / backward (F / B) spatial averaging, which combines the average of correlation matrices in which the relationship between the signal order of the received signals and the angles of arrival (directions of arrival) of the received signals is inverted. By performing forward spatial averaging or forward / backward (F / B) spatial averaging, it is possible to restore the rank of a degenerate matrix even when the signal of the target 100 detected by the target detection unit 11 is a combination of coherent waves.

[0097] The eigenvalue decomposition unit 16b obtains eigenvalues ​​and corresponding eigenvectors in the spatially averaged reception correlation matrix whose rank has been restored. Since the spatially averaged reception correlation matrix has its rank restored, the eigenvalues ​​of the reception antennas 3 are １ ~3 ４ Even when coherent waves are incident on the eigenvalue, it is possible to obtain not only one eigenvalue and one eigenvector corresponding to that eigenvalue, but also two or more corresponding eigenvalues ​​and two or more eigenvectors corresponding to those eigenvalues.

[0098] The target number determination unit 16c determines the number of targets 100 based on the eigenvalues ​​obtained by using the reception correlation matrix that has been spatially averaged by the eigenvalue decomposition unit 16b. The eigenvalues ​​and eigenvectors obtained by performing eigenvalue decomposition by the eigenvalue decomposition unit 16b using the reception correlation matrix that has been spatially averaged are used to determine the number of targets 100 based on the eigenvalues ​​and eigenvectors of the reception antennas 3 used for the eigenvalue decomposition. １ ~3 ４ The number of elements is divided into those corresponding to the incoming waves and those corresponding to noise.

[0099] For example, assuming that the number of elements in the receiving antenna of the subarray is three and the number of arriving waves is two, two eigenvalues ​​correspond to the arriving waves and the remaining one corresponds to noise. The target number determination unit 16c determines the number of targets 100 based on the relationship between the magnitudes of the eigenvalues. For example, the number of arriving waves corresponding to the number of targets 100 can be determined by using the power of noise that has been investigated in advance as a threshold value and comparing it with the eigenvalues ​​to obtain the number of arriving waves, or by determining the number from the ratio between the eigenvalues.

[0100] The target number determination unit 16c branches the processing depending on whether the number of targets 100 obtained by the target number determination is one or two or more. If the target number determination unit 16c determines that the number of targets is one, it can separately calculate a phase element dependent on the azimuth angle θ with respect to the target 100 and a phase element dependent on the velocity Vamb of the target 100 for the spatial signal S, and therefore processing is performed by the angle measurement compensation processing unit 12, the velocity estimation unit 13, the velocity compensation processing unit 14, and the angle measurement unit 15. If the number of targets is two or more, the target number determination unit 16c causes the radar signal processing device 1 to suspend processing of the current signal and move on to processing of the received signal at the next time, for example.

[0101] In short, the target number detection unit 16 performs spatial averaging of the reception correlation matrix obtained using the spatial signal S, determines the number of targets 100 based on the eigenvalues ​​obtained using the spatially averaged reception correlation matrix, and if the number of targets 100 is one, executes subsequent processing, but if the number of targets 100 is two or more, interrupts subsequent processing.

[0102] Next, the operation of the radar signal processing device 1 according to embodiment 3 will be described with reference to the flowchart shown in Fig. 9. The target signal detection step ST1 is the same as the target signal detection step ST1 in the radar signal processing device 1 according to embodiment 1. In step ST11, the reception correlation matrix processing unit 16a in the target number detection unit 16 uses the spatial signal S obtained by the target detection unit 11 according to equation (3) above to obtain the reception correlation matrix R shown in equation (6) above, and performs spatial averaging of the reception correlation matrix R. Step ST11 is a reception correlation matrix acquisition step for obtaining the reception correlation matrix that has been subjected to spatial averaging.

[0103] In step ST12, the eigenvalue decomposition unit 16b in the target number detection unit 16 obtains eigenvalues ​​and corresponding eigenvectors in the spatially averaged reception correlation matrix. Step ST12 is an eigenvalue decomposition step for obtaining eigenvalues ​​and corresponding eigenvectors.

[0104] In step ST13, the target number determination unit 16c in the target number detection unit 16 determines the number of targets 100 based on the eigenvalue obtained by the eigenvalue decomposition unit 16b, and proceeds to step ST14. In step ST14, if the target number determination unit 16c determines that the number of targets 100 is 1, proceeds to step ST2.

[0105] The operations from step ST2 onwards are the same as those from step ST2 onwards in embodiment 1, and therefore will not be described further. On the other hand, in step ST14, if the target number determination unit 16c determines that the number of targets 100 is two or more, the processing of the current signal is suspended, and processing such as moving on to processing of the received signal at the next time is performed.

[0106] Similar to the radar signal processing device 1 according to the first embodiment, the hardware configuration of the radar signal processing device 1 according to the third embodiment is realized by a computer including a CPU 1A, a RAM 1B, a ROM 1C, an input interface unit 1D, an output interface unit 1E, and a signal path (bus) 1F, as shown in FIG. 5 .

[0107] The radar signal processing device 1 according to the third embodiment determines the number of targets 100 and determines in the target number detection unit 16 that the signal being handled is for one target 100. Then, as in the radar signal processing device according to the first embodiment, the radar signal processing device 1 separates and estimates a phase element that depends on the azimuth angle θ relative to the target 100 and a phase element that depends on the velocity Vamb of the target 100, thereby obtaining the velocity V of the target 100 with an expanded velocity measurement range and the azimuth angle θ relative to the target 100. Therefore, even when there is velocity ambiguity, it is possible to obtain the velocity of the target with an expanded velocity measurement range and the azimuth angle relative to the target with high accuracy.

[0108] The target number detection unit 16 shown in embodiment 3 may be included in the radar signal processing device 1 according to embodiment 2. When the radar signal processing device 1 according to embodiment 2 includes the target number detection unit 16 shown in embodiment 3, the radar signal processing device 1 according to embodiment 2 performs the processes of steps ST11 to ST14 shown in Fig. 9 after target signal detection step ST1 in the flow shown in Fig. 7 , and if the target number detection unit 16 determines in step ST14 that the number of targets 100 is 1, the process proceeds to step ST2, and performs the processes of steps ST2, ST3, ST4a, ST5, ST6, and ST7 shown in Fig. 7 .

[0109] It should be noted that the embodiments may be freely combined, or any of the components in each embodiment may be modified, or any of the components in each embodiment may be omitted.

[0110] The radar signal processing device according to the present disclosure is suitable for applications including an in-vehicle radar device.

[0111] 1 radar signal processing device, 2 １ ~2 ３ Transmitting antenna, 3 １ ~3 ４ Receiving antenna, 11 target detection unit, 12, 12A angle measurement compensation processing unit, 13 speed estimation unit, 14 speed compensation processing unit, 15 angle measurement unit, 16 target number detection unit, 100 target.

Claims

1. A target detection unit that obtains the distance, arrival angle, and speed of a target using a received signal corresponding to incident waves from a plurality of receiving antennas that receive reflected waves from the target, which are reflected by the target from transmission waves transmitted in time division from a plurality of transmitting antennas, and a transmission signal corresponding to the transmission waves from the plurality of transmitting antennas; an angle measurement compensation processing unit that estimates a phase element depending on the azimuth angle of the target that is not affected by the phase element due to the speed of the target for a spatial signal formed by a combination of the plurality of transmitting antennas and the plurality of receiving antennas obtained by the target detection unit, corrects the spatial signal using the phase element depending on the azimuth angle, and obtains an angle-compensated spatial signal that is not affected by the phase element depending on the azimuth angle of the target; a speed estimation unit that performs a fast Fourier transform process on the angle-compensated spatial signal obtained by the angle measurement compensation processing unit, determines the presence or absence of folding of the speed obtained by the target detection unit using the processing result obtained by the fast Fourier transform process, and obtains an estimated speed of the target from the speed of the target obtained by the target detection unit based on the determined result; a speed compensation processing unit that estimates a phase element depending on the speed of the target that is not affected by the phase element due to the azimuth angle of the target for the spatial signal, corrects the spatial signal using the phase element depending on the speed, and obtains a speed-compensated spatial signal that is not affected by the phase element depending on the speed of the target; and an angle measurement unit that performs angle measurement signal processing on the speed-compensated spatial signal obtained by the speed compensation processing unit to obtain the azimuth angle of the target. A radar signal processing apparatus comprising the above components.

2. The spatial signal is represented in matrix form, where columns indicate transmission and rows indicate reception, each element in the matrix has a distance / azimuth angle phase element and a speed phase element; the angle-compensated spatial signal obtained by the angle measurement compensation processing unit is obtained by a process of canceling the distance / azimuth angle phase element from the spatial signal and leaving only the speed phase element; the speed-compensated spatial signal obtained by the speed compensation processing unit is obtained by a process of canceling the speed phase element from the spatial signal and leaving only the distance / azimuth angle phase element. The radar signal processing apparatus according to claim 1.

3. The spatial signal is represented in matrix form, where columns indicate transmission and rows indicate reception. Each element in the matrix has a distance - azimuth phase element and a velocity phase element. The angle - compensated spatial signal obtained by the angle measurement compensation processing unit performs a DOA (Direction of Arrival) estimation process for the direction of arrival in a form not affected by the velocity of the target on the spatial signal, estimates the azimuth angle with respect to the target, and is obtained by a process of canceling the distance - azimuth phase element from the spatial signal and leaving the velocity phase element using the estimated azimuth angle which is the result of the DOA estimation process. The radar signal processing apparatus according to claim 1.

4. The spatial signal is represented in matrix form, where columns indicate transmission and rows indicate reception. Each element in the matrix has a distance - azimuth phase element and a velocity phase element. The angle - compensated spatial signal obtained by the angle measurement compensation processing unit performs a DOA (Direction of Arrival) estimation process for the direction of arrival in a form not affected by the velocity of the target on the spatial signal, estimates the azimuth angle with respect to the target, extracts a signal having the distance - azimuth phase element and the velocity phase element corresponding to the distance with respect to the target, expands the signal compensation range to the signal extracted by the distance with respect to the target, and performs a phase compensation process using the estimated azimuth angle which is the result of the DOA estimation process. The radar signal processing apparatus according to claim 1.

5. The estimated velocity of the target obtained by the velocity estimation unit is: when the determination result of the presence or absence of aliasing indicates a positive aliasing, it is a value obtained by adding twice the value of the maximum velocity of the velocity measurement range with respect to the velocity of the target obtained by the target detection unit to the velocity of the target obtained by the target detection unit; when the determination result of the presence or absence of aliasing indicates a negative aliasing, it is a value obtained by subtracting twice the value of the maximum velocity of the velocity measurement range with respect to the velocity of the target obtained by the target detection unit from the velocity of the target obtained by the target detection unit; when the determination result of the presence or absence of aliasing indicates no positive or negative aliasing, it is the velocity of the target obtained by the target detection unit. The radar signal processing apparatus according to any one of claims 1 to 4.

6. The phase element depending on the velocity of the target, which has no influence on the phase element due to the azimuth angle with respect to the target for the spatial signal in the velocity compensation processing unit, is the estimated velocity of the target obtained by the velocity estimation unit. The radar signal processing apparatus according to any one of claims 1 to 4.

7. A radar signal processing apparatus according to any one of claims 1 to 4, further comprising a target number detection unit that performs spatial averaging processing on a received correlation matrix obtained using the spatial signal, determines the number of targets based on eigenvalues obtained using the spatially averaged received correlation matrix, executes subsequent processing if the number of targets is one, and interrupts subsequent processing if the number of targets is two or more.

8. A radar signal processing method comprising: a target signal detection step in which a target detection unit uses a received signal corresponding to an incoming wave from a plurality of receiving antennas that receive a reflected wave from a target, the reflected wave being caused by a transmission wave transmitted from a plurality of transmission antennas in a time-division manner, and a transmission signal corresponding to the transmission wave from the plurality of transmission antennas to obtain a distance, an arrival angle, and a speed of the target; an arrival angle compensation step in which an angle compensation processing unit obtains an angle-compensated signal in which a distance / azimuth phase element is canceled out from a signal having a distance / azimuth phase element and a speed phase element formed by a combination of the plurality of transmission antennas and the plurality of receiving antennas; a speed acquisition step in which a speed estimation unit performs fast Fourier transform processing on the angle-compensated signal, determines the presence or absence of folding of the speed of the target using a processing result obtained by the fast Fourier transform processing, and obtains an estimated speed of the target from the speed of the target based on the determination result; a speed compensation step in which a speed compensation processing unit obtains a speed-compensated signal in which the speed phase element is canceled out from a signal having the distance / azimuth phase element and the speed phase element; and an angle measurement step in which an angle measurement unit performs angle measurement signal processing on the speed-compensated signal to obtain an azimuth angle of the target.

9. A target signal detection procedure for obtaining the distance, arrival angle, and velocity of a target by using a received signal corresponding to incident waves from a plurality of receiving antennas that receive reflected waves from the target, which are reflected by the target from transmission waves transmitted from a plurality of transmitting antennas in a time-division manner, and a transmission signal corresponding to the transmission waves from the plurality of transmitting antennas; an arrival angle compensation procedure for obtaining an angle-compensated signal in which the distance / azimuth phase element is canceled out from a signal having a distance / azimuth phase element and a velocity phase element formed by a combination of the plurality of transmitting antennas and the plurality of receiving antennas; a velocity acquisition procedure for performing a fast Fourier transform process on the angle-compensated signal, determining the presence or absence of velocity aliasing of the target by using the processing result obtained by the fast Fourier transform process, and obtaining an estimated velocity of the target based on the determined result; a velocity compensation procedure for obtaining a velocity-compensated signal in which the velocity phase element is canceled out from a signal having the distance / azimuth phase element and the velocity phase element; and an angle measurement procedure for performing angle measurement signal processing on the velocity-compensated signal to obtain the azimuth angle with respect to the target; a radar signal processing program for causing a computer to execute these procedures.

10. A target signal detection procedure for obtaining the distance, arrival angle, and speed of a target using a received signal corresponding to incident waves from a plurality of receiving antennas that receive reflected waves from the target, which are reflected by the target from transmitted waves transmitted in time division from a plurality of transmitting antennas, and a transmission signal corresponding to the transmitted waves from the plurality of transmitting antennas; an arrival angle compensation procedure for obtaining an angle-compensated signal in which the distance / azimuth phase element is canceled from a signal having a distance / azimuth phase element and a speed phase element formed by a combination of the plurality of transmitting antennas and the plurality of receiving antennas; a speed acquisition procedure for performing a fast Fourier transform process on the angle-compensated signal, determining the presence or absence of aliasing of the speed of the target using the processing result obtained by the fast Fourier transform process, and obtaining an estimated speed of the target from the speed of the target based on the determined result; a speed compensation procedure for obtaining a speed-compensated signal in which the speed phase element is canceled from a signal having the distance / azimuth phase element and the speed phase element; and an angle measurement procedure for performing angle measurement signal processing on the speed-compensated signal to obtain the azimuth angle with respect to the target. A recording medium storing a program for causing a computer to execute the procedures.

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