WO2025109663A1 - Radar signal processing device, radar signal processing method, radar signal processing program, and recording medium - Google Patents

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

This disclosure relates to a radar signal processing device, a radar signal processing method, a radar signal processing program, and a recording medium in a TDM-MIMO (TDM: Time Division Multiplexing; MIMO: Multiple-Input Multiple-Output) radar device.

In recent years, TDM-MIMO radar devices have been adopted for applications including vehicle-mounted radar devices due to their wide frequency resources and simple hardware.
However, one of the issues with the TDM-MIMO radar device is that because the TDM-MIMO radar device switches over time, the speed measurement range (Nyquist frequency) that can be measured by the radar device is reduced. As a result, aliasing (also known as speed ambiguity; hereafter referred to as speed ambiguity) occurs for targets moving at speeds that exceed the speed measurement range, and the target speed may be inaccurately estimated.

Patent Document 1 is an example of a prior art document that focuses on this issue.
Patent document 1 discloses a method for estimating a speed without aliasing, based on the premise that when the target speed is within the speed measurement range, an ideal corrected virtual array signal Sc will be a curve with a single peak in the angle FFT, whereas when the target speed is outside the speed measurement range, an erroneous virtual array signal Sc will likely be a curve with two peaks in the angle FFT.

Special table 2019-522220 publication

The data reproduction device shown in Patent Document 1 had the problem that it was difficult to obtain the target speed and the azimuth angle to the target with high accuracy when there was velocity ambiguity.

The present disclosure aims to solve the above problem by providing a radar signal processing device that can obtain the target speed and highly accurate azimuth angle to the target over an expanded speed measurement range even when there is speed ambiguity.

The radar signal processing device according to the present disclosure includes a target detection unit that obtains the distance and angle of arrival of the target and the speed of the target using received signals corresponding to the incoming waves from the multiple receiving antennas that receive the reflected waves from the target and transmitted signals corresponding to the transmitted waves from the multiple transmitting antennas when the transmitted waves are transmitted in a time-division manner from the multiple transmitting antennas and reflected waves from the target are reflected by the target, an angle measurement compensation processing unit that estimates a phase element that depends on the azimuth angle of the target and is not affected by a phase element due to the speed of the target for a spatial signal obtained by the 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 of the target, and an angle measurement compensation processing unit. a velocity estimation unit that performs fast Fourier transform processing on the angle-compensated spatial signal obtained by the speed compensation unit, 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 dependent on the velocity of the target that is not affected by a phase element due to the azimuth angle to the target for the spatial signal, corrects the spatial signal using the phase element dependent on the velocity, and obtains a velocity-compensated spatial signal that is not affected by a phase element dependent on the velocity 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 to the target.

According to this disclosure, even when there is velocity ambiguity, it is possible to obtain the target velocity and highly accurate azimuth angle to the target with an expanded velocity measurement range.

1 is a configuration diagram showing a radar signal processing device according to a first embodiment; 2 is an explanatory diagram showing a schematic diagram of the relationship between the transmitting antenna and the receiving antenna of the radar device and the transmitted waves and the received waves of a target. FIG. FIG. 4 is a schematic diagram of time switching of a transmission signal of the radar device according to the first embodiment. 4 is a flowchart showing an operation of the radar signal processing device according to the first embodiment; 1 is a configuration diagram showing a hardware configuration of a radar signal processing device according to a first embodiment; FIG. 11 is a configuration diagram showing a radar signal processing device according to a second embodiment. 10 is a flowchart showing an operation of the radar signal processing device according to the second embodiment; FIG. 11 is a configuration diagram showing a radar signal processing device according to a third embodiment. 13 is a flowchart showing an operation of the radar signal processing device according to the third embodiment;

Embodiment 1.
A radar signal processing device 1 according to a first embodiment will be described with reference to FIGS. 1 to 4. FIG.
A radar signal processing device 1 according to the first embodiment is a radar signal processing device applied to an on-board TDM-MIMO radar device mounted on a moving object such as an automobile or indoor mobility device.
As shown in FIG. 2, the TDM-MIMO radar device (hereinafter simply referred to as the radar device) has N transmitting antennas ₂₁ to ₂₃ and M receiving antennas ₃₁ to ₃₄ , and in addition to a radar signal processing device 1 which forms part of the receiving device, it also has a transmitting device (not shown), a control unit (not shown) which controls the transmitting device and the receiving device, and an overall control unit (not shown) which controls the entire radar device.

It should be noted 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.
That is, although the transmitting antennas 2 ₁ to 2 ₃ are shown as three elements and the receiving antennas 3 ₁ to 3 ₄ are shown as four elements, the numbers are not limited to these, and it is sufficient that each of the transmitting antennas 2 ₁ to 2 ₃ and the receiving antennas 3 ₁ to 3 ₄ has a plurality of elements.

The transmitting device radiates transmission waves (radio waves) Tx ₁ to Tx ₃ , which are transmission signals, from transmitting antennas 2 ₁ to 2 ₃ in a time-division manner in time series order.
The transmitting device is a commonly known transmitting device used in an on-vehicle TDM-MIMO radar device, and a detailed description thereof will be omitted.
The receiving device receives transmission waves transmitted in a time-series manner from transmitting antennas _2-1 to _2-3 in a time-division manner, which are reflected by a target 100, and generates receiving signals consisting of digital information corresponding to arriving waves (received waves) Rx _-1 to Rx- ₄ from receiving antennas _3-1 to _3-4 which receive the reflected waves from target 100.

The transmitting device radiates transmission waves Tx ₁ to Tx ₃ from transmitting antennas 2 ₁ to 2 ₃ using commonly known methods such as the FMCW (Frequency Modulated Continuous Wave) method, the Fast-Chirp method, or the Pulse Doppler method, and detailed description thereof will be omitted.
The receiving device processes signals received by the receiving antennas 3 ₁ to 3 ₄ .

In the radar device to which the first embodiment is applied, the up-chirp Fast-Chirp method will be described as an example.
The transmitting antennas _2.sub.1 to _2.sub.3 each transmit chirp signals _Tx.sub.1-1 , Tx.sub.2-1, Tx.sub.3-1, Tx.sub.1-2, ..., Tx.sub.1- _Nc , _Tx.sub.2 -Nc, and _Tx.sub.3 - _Nc whose frequencies increase over time as they are switched _sequentially in chronological order by a transmitting device, as _shown in FIG.
Nc indicates the number of chirps in each of the transmitting antennas 2 ₁ to 2 ₃ .

Chirp signals Tx ₁ -1, Tx ₁ -2, . . . , Tx ₁ -Nc represent the first, second, . . . , Nc-th transmission waves transmitted from the transmitting antenna _2-1 .
Chirp signals Tx ₂ -1, . . . , Tx ₂ -Nc indicate the _1st , .
Chirp signals Tx ₃ -1, . . . , Tx ₃ -Nc indicate _the 1st, .

Chirp signals Tx ₁ -nc, Tx 2 -nc, and Tx ₃ -nc are transmitted in this order at time intervals (signal transmission intervals) Tc from transmitting antenna 2 _{1 ,} transmitting antenna ₂ 2, and transmitting antenna 2 _3. Note that nc ranges from 1 to Nc.
Considering the entire radar device, the signal transmission interval for transmitting a chirp signal is Tc, but the signal transmission interval for signals transmitted from the same transmitting element of each of transmitting antennas _{2-1, 2-2, and 2-3} is NTx×Tc.
NTx is the number of transmitting antennas, and in the radar device to which the first embodiment is applied, the number of elements is 3, for example.

The transmitting antennas 2 ₁ to 2 ₃ are arranged in an array with element spacing ΔdTx between adjacent transmitting antennas being equal or unequal.
2, the angles of transmission of the transmission waves Tx ₁ to Tx ₃ from the transmitting antennas 2 ₁ to 2 ₃ to the target 100 are indicated as θ.
θ corresponds to the azimuth angle of the target in the radar device.

The receiving antennas 3 ₁ to 3 ₄ receive the incoming waves Rx ₁ to Rx ₄ reflected by the target 100, respectively.
The receiving antennas 3 ₁ to 3 ₄ are arranged in an array with element spacing ΔdRx between adjacent receiving antennas being equal or unequal.
However, the element spacing ΔdRx is set to a spacing that does not cause estimation errors due to grating lobes when performing processing to estimate the DOA (Direction Of Arrival) of radio waves.
2, the angles of arrival of the waves Rx ₁ to Rx ₄ from the target 100 at the receiving antennas 3 ₁ to 3 ₄ are indicated as θ.

It is assumed that the sending angle and the arriving angle are θ, and that the transmitting waves Tx ₁ to Tx ₃ and the arriving waves Rx ₁ to Rx ₄ do not take different paths, ie, are not so-called multipath waves.
In addition, the target 100 approaches the radar device at a speed V (approaching) or moves away from the radar device at a speed V (leaving), and the speed V of the target 100 may exceed the speed measurement range of the radar device.

In the 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.

Moreover, 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 velocity V of the target 100 approaches the radar device at velocity V or moves away from the radar device at velocity V, so it can be a positive or negative value, and therefore an absolute value is given.

When the velocity V of the target 100 exceeds the maximum velocity Vmax of the velocity measurement range, if an attempt is made to obtain the Doppler velocity of the target by FFT processing in the chirp signal direction (= FFT in the slow time direction, FFT: Fast Fourier Transform), aliasing of the Doppler velocity occurs because the signal exceeds the Nyquist frequency.
In a TDM-MIMO radar device, due to time division transmission, a signal for a target 100 approaching the radar device at a speed V or moving away from the radar device at a speed V is received with its phase rotated by the signal transmission interval Tc, so speed compensation processing is required to perform MIMO signal processing such as angle measurement signal processing.

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 offset, causing an erroneous measurement angle 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 embodiment 1 can estimate the velocity V of the target 100 with high accuracy even when the velocity V of the target 100 exceeds the maximum velocity value Vmax of the velocity measurement range, thereby preventing erroneous angle measurements from occurring.

As shown in FIG. 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 receives reception signals consisting of digital information corresponding to the incoming waves _Rx1 to _Rx4 from the receiving antennas ₃₁ to ₃₄ , and 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 the reception signals and transmission signals consisting of digital information corresponding to the transmission waves Tx1 to Tx3 from the transmitting antennas ₂₁ to ₂₃ for each set observation period.

In the following description, the relative distance and the direction of the target 100 may be combined to be referred to as a signal indicating the position of the target 100, and the relative distance, direction and relative speed may be combined to be referred to as a signal for the target 100.
Moreover, the relative distance and the relative velocity are simply referred to as the distance and the velocity.

The position and speed are calculated in the signal transmission interval NTx×Tc based on the number of combinations of the multiple transmitting antennas 2 ₁ to 2 ₃ and the multiple receiving antennas 3 ₁ to 3 ₄ , that is, N×M, or 3×4 in the first embodiment.
The velocity may include velocity ambiguity (foldback) if the velocity V of the target 100 exceeds the maximum velocity value Vmax of the velocity measurement range.
The position and velocity may be calculated by a method generally known in the art for calculating position and velocity in radar devices, and detailed description thereof will be omitted.

As an example, in the case of transmission signals and reception signals of the up-chirp Fast-Chirp method, the position and velocity are calculated by performing 2D-FFT processing for each combination of multiple transmission antennas ₂₁ to ₂₃ and multiple reception antennas ₃₁ to ₃₄ , creating a range-Doppler map by incoherent integration, and then detecting the position and velocity of the target 100 by CFAR (Constant False Alarm Rate) signal processing.
It should be noted that any method other than the Fast-Chirp method may be used as long as a reflected signal from the target 100 is obtained under conditions that match the format of the radar signal.

The target detection unit 11 uses information indicating the position and speed of the target 100 to extract information on the target 100 from the range-Doppler map, thereby taking out spatial signals S for the combinations of the transmitting antennas 2 ₁ to 2 ₃ and the receiving antennas 3 ₁ to 3 ₄ .
In the first embodiment, in the case of 4×3 MIMO using three elements as transmitting antennas 2 ₁ to 2 ₃ and four elements as receiving antennas 3 ₁ to 3 ₄ , the spatial signal S extracted by the target detection unit 11 is expressed in matrix form by the following equation (3).

In the above formula (3), columns indicate transmission and rows indicate reception. Each element in M rows and N columns represents a signal transmitted from the nth transmitting element (transmitting antenna 2 _n ) and received by the mth receiving element (receiving antenna 3 _m ). n ranges from 1 to N, and m ranges from 1 to M.

In addition, in the above equation (3), Φ mn is a distance/azimuth angle phase element due to 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 element spacing for a reference element selected from the receiving antennas 3 ₁ to 3 _4. The reference element can be selected from any combination of antenna elements.

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(i2π 2(n-1)V Tc/λ) (5)

In short, the target detection unit 11 has a first function of calculating the position of the target ₁₀₀ and the velocity of the target ₁₀₀ using received signals corresponding to the incoming waves _Rx1 to _Rx4 from the receiving antennas _{31 to 34} and transmitted signals corresponding to the transmitted waves Tx1 to _Tx3 from the transmitting antennas 21 to 23, and a second function of obtaining a spatial signal S expressed in a matrix format, with columns indicating transmission and rows indicating reception, and with each element in the matrix having distance/azimuth phase elements and velocity phase elements.

When measuring an angle 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 formula (3), if the velocity V of the target 100 exceeds the maximum velocity value Vmax of the velocity measurement range, the velocity may contain velocity ambiguity (folding). Therefore, if the velocity has velocity ambiguity, the velocity phase element Φvn may not be compensated correctly, and correct MIMO signal processing for the measured angle may not be possible.

Therefore, in the first embodiment, the following process is carried out.
The angle measurement compensation processor 12 has a third function of performing a process of estimating 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 with respect to the target 100, and a fourth function of performing a process of canceling the distance/azimuth phase element Φ from the spatial signal S obtained by the above equation (3) and leaving only the velocity phase element Φ, using the provisionally estimated azimuth angle θ as a result of the DOA estimation process and the element spacing Δd with respect to the reference element, to obtain an angle-compensated spatial signal S.
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 taking charge of the third function and the spatial signal compensating unit 12b taking charge of the fourth function.

That is, by having the third function and the fourth function, the angle measurement compensation processing unit 12 estimates a phase element that depends on the arrival angle θ of the target 100 without being influenced by the 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 arrival angle θ to obtain an angle-compensated spatial signal S cmp.
In short, the angle measurement compensation processing unit 12 estimates the distance/azimuth angle phase element Φmn, and performs processing to cancel the distance/azimuth angle phase element Φmn from the spatial signal S obtained by the above equation (3) while leaving only the velocity phase element Φvn, thereby obtaining an angle-compensated spatial signal Scmp that is not affected by the arrival angle θ with respect to the target 100.

The third function of the angle measurement compensation processing unit 12 will 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 process is for provisionally estimating a phase element that depends on the arrival angle θ of the target 100 without being affected by the phase element due to the velocity V of the target 100 .

As can be seen from equation (6) above, in the reception correlation matrix R, the velocity phase element Φvn is cancelled out during correlation matrix calculation, and only the range/azimuth phase element Φmn remains.
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 with respect to the target 100.

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), the Capon method, MUSIC (Multiple Signal Classification) method, or ESPRIT (Estimation of Signal Parameter via Rotational Invariance Techniques) method, and tentatively estimates the azimuth angle (arrival angle) θ with respect to the target 100.
The provisionally estimated azimuth angle θ is obtained by estimating the direction of arrival using the array of receiving antennas _3-1 to _3-4 , and is therefore not affected by phase rotation due to the speed V of the target 100, making it possible to estimate the direction (arrival angle θ) relative to the target 100 with high accuracy.

The angle measurement compensation processing unit 12 may tentatively estimate the azimuth angle θ with respect to the target 100 by the following method.
That is, the first column of the spatial signal S obtained by the above equation (3) contains only the velocity phase element Φv1, and the azimuth angle (arrival angle) θ with respect to the target 100 can be estimated using only the signal extracted from the first column, regardless of the presence or absence of velocity ambiguity.
Therefore, the angle measurement compensation processing unit 12 uses the signal shown in the first column of the spatial signal S obtained by the above equation (3) to perform DOA estimation processing using a signal processing method such as angle FFT, DBF, Capon method, MUSIC method, or ESPRIT method, and provisionally estimates the DOA estimation processing result 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) relative to the target 100 with high accuracy.

In short, as a third function, the angle measurement compensation processing unit 12 performs DOA estimation processing from the spatial signal S obtained by the above equation (3) without being influenced by the velocity phase element Φvn, and provisionally estimates the azimuth angle θ with respect to the target 100.
The fourth function of the angle measurement compensation processor 12 is processed as follows.
The angle measurement compensation processing unit 12 uses the azimuth angle θ estimated by the third function and the element spacing Δd with respect to the reference element to cancel the distance/azimuth phase element Φ from the spatial signal S obtained by the above equation (3) and leave only the velocity phase element Φ, thereby obtaining an angle-compensated spatial signal S cmp that is not influenced by the azimuth angle θ with respect to the target 100, as shown in the following equation (7), that is, an angle-compensated spatial signal S cmp that is not influenced by the phase element due to the azimuth angle with respect to the target 100.

In the above equation (7), when one focuses on the row direction, the velocity phase element Φvn is due to the velocity V of the target 100 corresponding to the transmitting antennas _2-1 to _2-3 sampled at the signal transmission interval Tc, so that it is possible to estimate the phase rotation using FFT processing and other processes.
In the above equation, the column direction corresponds to the receiving antennas 3 ₁ to 3 ₄ .

The velocity estimator 13 estimates the velocity V of the target 100 using the angle-compensated spatial signal Scmp obtained from the angle measurement compensation processor 12, in which the range/azimuth phase element Φmn is cancelled.
The speed 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 speed Vmax_ex in the speed measurement range of the radar device using the following equation (8).

In other words, 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)

The speed estimation unit 13 has a fifth function of performing FFT processing on the angle-compensated spatial signal Scmp in the transmitting antenna direction to obtain a maximum value Vp of the FFT processing result, and a sixth function of obtaining an estimated speed V using the maximum value Vp of the FFT processing result.
The speed estimation unit 13 has an FFT processing unit 13a and an estimation unit 13b, the FFT processing unit 13a is responsible for the fifth function, and the estimation unit 13b is responsible for the sixth function.

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 the 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.

The speed estimation unit 13 performs FFT processing to estimate the speed, which is based on the number of transmitting antennas 2 ₁ to 2 ₃ , and therefore the accuracy may be degraded.
Therefore, in the sixth function, the speed 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 there is speed folding and whether the folding direction is positive or negative, and estimates the estimated speed V of the target 100 using the speed Vamb of the target 100 calculated by the target detection unit 11.

The speed estimation unit 13 uses the maximum value Vp of the FFT processing result obtained by the fifth function to determine whether or not there is speed aliasing and whether the aliasing is positive or negative, by the method described below.
That is, the speed 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 of 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 of the following equation (10) satisfies the relationship of 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 of the following equation (11) satisfies the relationship of the following equation (11).

In other words, since the speed Vamb of the target 100 calculated by the target detection unit 11 is found within the speed measurement range in which the maximum speed value is the maximum speed value Vmax, the speed estimation unit 13 can determine whether the speed has folded over and whether it is positive or negative depending on which of the following equations (9) to (12) the maximum value Vp of the FFT processing result satisfies.

Vmax<Vp≦Vmax_ex (9)
-Vmax_ex≦Vp<-Vmax (10)
-Vmax<Vp<Vmax (11)

When the maximum value Vp of the FFT processing result satisfies the relationship of the above equation (9), the speed estimating unit 13 can obtain the estimated speed V of the target 100 by the following equation (12).
V=Vamb+2Vmax (12)
That is, the estimated speed V of the target 100 is set to a value obtained by adding twice the maximum speed Vmax in the speed measurement range for the speed Vamb to the speed Vamb of the target 100 calculated by the target detection unit 11.

When the maximum value Vp of the FFT processing result satisfies the relationship of the above equation (10), the speed estimation unit 13 can obtain the estimated speed V of the target 100 by the following equation (13).
V=Vamb-2Vmax (13)
That is, the estimated speed V of the target 100 is set to the speed Vamb (negative value) of the target 100 calculated by the target detection unit 11 minus twice the maximum speed Vmax of the speed measurement range for the speed Vamb.

When the maximum value Vp of the FFT processing result satisfies the relationship of the above equation (11), the speed estimating unit 13 can obtain the estimated speed V of the target 100 by the following equation (14).
V=Vamb (14)

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 discriminatory processing to interpolate the roughness of the FFT processing result and output it.

In short, the velocity estimation unit 13 performs FFT processing on the angle-compensated spatial signal Scmp, judges 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 judgment.
The estimated velocity V of the target 100 obtained by the velocity estimator 13 is output as the velocity V of the target.

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

The velocity compensation processing unit 14 estimates a phase element dependent on the velocity V of the target 100 without being influenced by the 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 estimator 13 is used to compensate for the velocity phase element Φvn of the spatial signal S obtained by the above equation (3). In other words, a process is performed to cancel the velocity phase element Φvn from the spatial signal S and leave only the distance/azimuth phase element Φmn, thereby obtaining a velocity-compensated spatial signal Svcmp shown in the following equation (15).

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 the 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 .

In the above equation (15), the row direction represents the distance/azimuth phase element Φmn resulting from the distance and azimuth to the target 100 corresponding to the transmitting antennas _2-1 to _2-3 sampled at the signal transmission interval Tc, and the column direction corresponds to the receiving antennas _3-1 to _3-4 .
As shown in the above equation (15), the velocity-compensated spatial signal S is a spatial signal that is not influenced by the velocity V with respect to the target 100 and that contains only the range/azimuth phase element Φ, by canceling out the velocity phase element Φ from the spatial signal S obtained by the above equation (3).

The angle measurement unit 15 estimates the azimuth angle θ of the target using the velocity-compensated spatial signal Svcmp obtained from the velocity compensation processing unit 14, in which the velocity phase element Φvn is cancelled.
The angle measurement unit 15 obtains a high-resolution angle measurement value, i.e., the azimuth angle (angle of arrival) 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 measuring unit 15 is output as the azimuth angle θ of the target.

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.
In step ST1, the target detection unit 11 calculates the distance and angle of arrival (azimuth) of the target ₁₀₀ and the speed of the target ₁₀₀ using received signals consisting of digital information corresponding to the incoming waves _Rx1 to _Rx4 from the receiving antennas ₃₁ to ₃₄ and transmitted signals consisting of digital information corresponding to the transmitted waves _Tx1 to _Tx3 from the transmitting antennas 21 to 23.

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 matrix form, with columns indicating transmission and rows indicating reception, and each element in the matrix having a distance/azimuth angle phase element and a velocity phase element.
Step ST1 is also a step of acquiring a spatial signal S for the target 100.

In step ST2, the azimuth angle estimation unit 12a in the angle measurement compensation processing unit 12 performs direction of arrival estimation (DOA estimation) processing on a signal having a distance/azimuth angle phase element and a velocity phase element for the target 100 (spatial signal S in embodiment 1) without being affected by the velocity of the target 100, and tentatively estimates the azimuth angle θ for the target 100.
Step ST2 is a DOA estimation process step for provisionally estimating the azimuth angle θ with respect to the target 100 performed by the array of receiving antennas 3 ₁ to 3 ₄ .

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 distance/azimuth phase element Φmn is cancelled out for the spatial signal S for the target 100 using the azimuth angle θ obtained by the azimuth angle estimation unit 12a.
Step ST3 is a step for obtaining an angle-compensated spatial signal S cmp in which the range/azimuth phase element Φ mn is cancelled.
Steps ST2 and ST3 together constitute an angle-of-arrival compensation step in which the angle measurement compensation processing unit 12 acquires an angle-compensated signal in which the distance/azimuth phase element Φmn is cancelled out from a signal having a distance/azimuth phase element Φmn and a velocity phase element Φvn.

In step ST4, the FFT processing unit 13a in the velocity estimation unit 13 performs FFT processing on the angle-compensated signal, that is, the angle-compensated spatial signal Scmp in the first embodiment, and the estimation unit 13b uses the FFT processing result to determine whether or not there is aliasing with respect to the velocity Vamb of the target 100 calculated by the target detection unit 11.
Step ST4 is a return presence/absence determination step for determining whether or not there is a return with respect to the velocity Vamb of the target 100 calculated by the target detection unit 11.

In step ST5, the estimation unit 13b in the speed estimation unit 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 turnaround, and outputs the estimated speed as the target speed V.

In other words, if the processing result by the FFT processing unit 13a exceeds the positive value of the maximum speed Vmax of the speed measurement range for the speed Vamb of the target 100, the estimation unit 13b determines that a positive wraparound exists and calculates a value obtained by adding twice the maximum speed Vmax to the speed Vamb of the target 100 as the estimated speed V of the target 100; if the processing result by the FFT processing unit 13a is less than the negative value of the maximum speed Vmaxb of the speed measurement range for the speed Vam of the target 100, the estimation unit 13b determines that a negative wraparound exists and calculates a value obtained by subtracting twice the maximum speed Vmax from the speed Vamb of the target 100 (negative value) as the estimated speed V of the target 100; if the processing result by the FFT processing unit 13a is between the positive and negative values of the maximum speed Vmax of the speed measurement range for the speed Vamb of the target 100, the estimation unit 13b determines that there is no wraparound and sets the speed Vamb of the target 100 as the estimated speed V of the target 100.

Steps ST4 and ST5 together are a speed acquisition step for determining whether or not there is a wraparound 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.

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 using the estimated velocity V of the target 100 obtained by the velocity estimation unit 13 for a signal having a range/azimuth phase element and a velocity phase element for the target 100 (in embodiment 1, the spatial signal S).
Step ST6 is a velocity compensation step in which the velocity compensation processor 14 acquires a velocity-compensated signal in which the velocity phase element Φvn is cancelled from a signal having the range/azimuth phase element Φmn and the velocity phase element Φvn.

In step ST7, the angle measurement unit 15 obtains an azimuth angle (arrival angle) θ with respect to 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 an azimuth angle θ with respect to 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.

The radar signal processing device 1 according to embodiment 1, which is equipped with 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, is realized by a computer hardware configuration, and as shown in FIG. 5, is equipped with 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 hard disk device or a non-volatile recording device such as an SSD device, an input interface unit 1D, an output interface unit 1E, and a signal path (bus) 1F.

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 the programs stored in the ROM 1C into the RAM 1B, and executes various processes based on the programs loaded into the RAM.

The target detection unit 11, the angle measurement compensation processing unit 12, the speed estimation unit 13, the speed compensation processing unit 14, and the angle measurement unit 15 are each a component that represents a function executed by the CPU 1A based on a program stored in the ROM 1C and loaded into the RAM 1B.
The signal path 1F is a bus which interconnects the CPU 1A, the RAM 1B, the ROM 1C, the input interface section 1D, and the output interface section 1E.

The program stored in ROM 19 and executed by CPU 18 includes a target signal detection procedure in which the transmission waves transmitted in a time-division manner from multiple transmitting antennas are reflected by the target, and the distance, angle of arrival, and speed of the target are obtained using received signals corresponding to the arrival waves from multiple receiving antennas that receive the reflected waves from the target and transmitted signals corresponding to the transmission waves from multiple transmitting antennas; an angle of arrival compensation procedure in which an angle-compensated signal in which the distance and azimuth phase elements are cancelled out from a signal having distance and azimuth phase elements and speed phase elements obtained by a combination of multiple transmitting antennas and multiple receiving antennas; a velocity acquisition procedure in which a fast Fourier transform is performed on the angle-compensated signal, the processing result obtained by the fast Fourier transform is used to determine whether or not the target speed is folded back, and an estimated speed of the target is obtained from the target speed based on the result of the determination; a velocity compensation procedure in which a velocity-compensated signal in which the speed phase elements are cancelled out from a signal having distance and azimuth phase elements and speed phase elements; and an angle measurement procedure in which an azimuth angle is obtained for the target by performing velocity-compensated signal angle measurement signal processing.

In the radar signal processing device 1 according to the first embodiment, the speed estimation unit performs fast Fourier transform processing on the angle-compensated spatial signal obtained by the angle compensation processing unit and free from the influence of phase elements dependent on the azimuth angle relative to the target, and determines whether or not there is velocity aliasing using the processing result obtained by the fast Fourier transform processing, and obtains an estimated speed of the target from the target's speed based on the result of the determination, and the angle measurement unit performs angle measurement signal processing on the velocity-compensated spatial signal obtained by the velocity compensation processing unit and free from the influence of phase elements dependent 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 speed of the target with an expanded speed measurement range and the azimuth angle relative to the target with high accuracy.

Embodiment 2.
Second Embodiment A radar signal processing device 1 according to a second embodiment will be described with reference to FIGS.
The radar signal processing device 1 according to the second embodiment is the same as the radar signal processing device 1 according to the first embodiment except for the method of signal compensation in the angle measurement compensation processor 12.
Therefore, the following mainly describes signal compensation in an angle measurement compensation processing unit 12A, which corresponds to the angle measurement compensation processing unit 12 in the first embodiment.
In addition, in Figs. 6 and 7, the same reference numerals as those shown in Figs. 1 to 5 designate the same or corresponding parts.

The angle measurement compensation processing unit 12A includes an azimuth angle estimation unit 12a and a signal compensation 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 the first embodiment.
The signal compensation unit 12c performs a function similar to the fourth function performed by the spatial signal compensation unit 12b in the radar signal processing device 1 according to the first embodiment.
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.

The signal compensation unit 12c performs phase compensation of the received signals corresponding to the waves arriving from the receiving antennas _3.sub.1 to _3.sub.4 using the azimuth angle .theta. obtained by the azimuth angle estimation unit 12a and the element spacing .DELTA.dRx of the receiving antennas _3.sub.1 to _3.sub.4 .
Since the distance to the target 100 is obtained by the target detection unit 11, the received signal for phase compensation at this time has a distance/azimuth phase element Φmn corresponding to the distance to the target 100 and the velocity phase element Φvn.

The signal corresponding to the distance to the target 100 is a signal having (Nc×NTx) elements for each of the receiving antennas 3 ₁ to 3 _4. Nc is the number of chirps in each of the transmitting antennas 2 ₁ to 2 ₃ , and NTx is the number of transmitting antennas 2 ₁ to 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, where NRx is the number of receiving antennas _3-1 to _3-4 .

The signal compensation unit 12c performs phase compensation processing on a signal having the extracted 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 estimation unit 12a, to obtain an angle-compensated spatial signal.
By using signals extracted corresponding to the range to the target 100 , the phase compensation process extends the signal compensation range to signals extracted at the range to the target 100 .

The speed estimation unit 13 performs FFT processing on the signal that has been angle compensated by the angle measurement compensation processing unit 12A, and an estimation unit 13b uses the result of the FFT processing to determine whether or not there is aliasing with respect to the speed Vamb of the target 100 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 that the speed measurement range is expanded by the signal transmission interval Tc at which the chirp signal is transmitted.
Furthermore, the observation time increases to {(N+NTx-1)×Tc} due to the signal transmission interval Tc and the number NTx of transmitting antennas 2 ₁ to 2 ₃ , improving the frequency resolution.

In this example, the transmission signals are transmitted from the transmitting antennas _2.sub.1 to _2.sub.3 at equal intervals. However, instead of being transmitted at equal intervals, a time may be provided after the transmission signal to stop transmission, or the transmission intervals may be unequal.
In such a case, the Doppler frequency can be obtained by FFT processing or DFT (discrete Fourier transform) processing with zero padding according to the transmission interval of the transmission signal.

The estimated velocity V of the target 100 obtained by the velocity estimator 13 is output as the velocity V of the target.
Further, the estimated velocity V of the target 100 obtained by the velocity estimation unit 13 is used by a velocity compensation processing unit 14, and the azimuth angle θ for the target 100 obtained by an angle measurement unit 15 is output as the azimuth angle θ of the target.

Next, the operation of the radar signal processing device 1 according to the second embodiment will be described with reference to the flowchart shown in FIG.
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 the first embodiment.

In step ST3a, the signal compensation unit 12c in the angle measurement compensation processing unit 12A performs phase compensation of the entire received signal corresponding to the arriving waves from the receiving antennas _3-1 to _3-4 using the azimuth angle θ obtained by the azimuth angle estimation unit 12a and the element spacing ΔdRx of the receiving antennas _3-1 to _3-4 .
Step ST3a is a step for performing phase compensation on the entire received signal to obtain an angle-compensated signal.
Steps ST2 and ST3a together constitute an angle-of-arrival compensation step in which the angle measurement compensation processor 12A obtains an angle-compensated signal from the entire received signal, that is, a signal having (Nc×NTx×NRx) elements, where NRx is the number of receiving antennas _3-1 to _3-4 .

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 or not there is aliasing with respect to the velocity Vamb of the target 100 calculated by the target detection unit 11.
Step ST4a is a return presence/absence determination step for determining whether or not there is a return with respect to the velocity Vamb of the target 100 calculated by the target detection unit 11.

Since the entire received signal is phase-compensated in step ST3a and the entire phase-compensated received signal is subjected to FFT processing in step ST4a, the velocity measurement range is expanded by the signal transmission interval Tc during which the chirp signal is transmitted.
Furthermore, the observation time increases to {(N+NTx-1)×Tc} due to the signal transmission interval Tc and the number NTx of transmitting antennas 2 ₁ to 2 ₃ , improving the frequency resolution.

Step ST5, speed compensation step ST6, and angle measurement step ST7 are the same as step ST5, speed compensation step ST6, and angle measurement step ST7 in the radar signal processing device 1 according to the first embodiment.
Steps ST4a and ST5 together constitute 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.

The hardware configuration of the radar signal processing device 1 according to the second embodiment is also 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, in the same manner as the radar signal processing device 1 according to the first embodiment.

The radar signal processing device 1 according to the second embodiment, like the radar signal processing device 1 according to the first embodiment, obtains the velocity V of the target 100 with an expanded velocity measurement range and the azimuth angle θ with respect to the target 100 by separately estimating 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, so that 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 respect to the target with high accuracy.

Embodiment 3.
A radar signal processing device 1 according to a third embodiment will be described with reference to FIGS.
The radar signal processing device 1 of embodiment 3 differs from the radar signal processing device 1 of embodiment 1 in that it includes a target number detection unit 16 that detects the number of targets 100, but is otherwise the same.
Therefore, the following description will focus on the target number detection unit 16.
In addition, in Figs. 8 and 9, the same reference numerals as those shown in Figs. 1 to 5 designate the same or corresponding parts.

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

When the number of receiving antennas _3-1 to _3-4 is greater than three elements, the receiving correlation matrix processing unit 16a may perform forward spatial averaging processing in which the receiving antennas _3-1 to _3-4 are divided into subarrays and a plurality of receiving correlation matrices R created for each subarray are averaged to obtain a spatially averaged receiving correlation matrix, or may perform forward/backward (F/B) spatial averaging processing in which an average of correlation matrices in which the relationship between the signal order of the received signals and the arrival angles (arrival directions) of the received signals is inverted to obtain a spatially averaged receiving correlation matrix.
By performing forward spatial averaging processing or forward/backward (F/B) spatial averaging processing, the rank of a degenerate matrix can be restored even when the signal of the target 100 detected by the target detection unit 11 is a combination of coherent waves.

The eigenvalue decomposition unit 16b obtains eigenvalues and corresponding eigenvectors in the spatially averaged reception correlation matrix with the rank of the matrix restored.
Since the rank of the receiving correlation matrix that has been subjected to spatial averaging processing is restored, even when coherent waves are incident on the receiving antennas _3-1 to _3-4 , 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.

The target number determination unit 16c determines the number of targets 100 based on eigenvalues obtained using the reception correlation matrix spatially averaged by the eigenvalue decomposition unit 16b.
The eigenvalues and eigenvectors obtained by performing eigenvalue decomposition using the spatially averaged reception correlation matrix by the eigenvalue decomposition unit 16b are separated into those corresponding to arriving waves and noise with respect to the number of elements of the reception antennas _3-1 to _3-4 used in the eigenvalue decomposition.

For example, assuming that the number of elements of 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 magnitude relationship of the eigenvalues. For example, the number of arriving waves corresponding to the number of targets 100 is determined by a method in which the power of noise previously checked is set as a threshold value and the number of arriving waves is obtained by comparing with the eigenvalue, or a method in which the number of arriving waves corresponding to the number of targets 100 is determined based on the ratio between the eigenvalues.

The target number determination unit 16c branches the process depending on whether the number of targets 100 obtained by the target number determination is one or two or more.
When the target number determination unit 16c determines that the number of targets is 1, it is possible to separate and calculate a phase element that depends on the azimuth angle θ with respect to the target 100 and a phase element due to 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, respectively.
If the number of targets is two or more, the target number determination unit 16c performs processing such as interrupting processing of the current signal in the radar signal processing device 1 and moving on to processing of the received signal at the next time.

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 from the eigenvalues obtained using the reception correlation matrix that has been subjected to spatial averaging, 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.

Next, the operation of the radar signal processing device 1 according to the third embodiment will be described with reference to the flowchart shown in FIG.
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 the first embodiment.
In step ST11, the reception correlation matrix processing unit 16a in the target number detection unit 16 obtains the reception correlation matrix R shown in the above equation (6) using the spatial signal S obtained by the target detection unit 11 according to the above equation (3), and performs spatial averaging processing of the reception correlation matrix R.
Step ST11 is a reception correlation matrix acquisition step for obtaining a reception correlation matrix that has been subjected to spatial averaging.

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

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 eigenvalues obtained by the eigenvalue decomposition unit 16b, and the process proceeds to step ST14.
In step ST14, if the target number determination unit 16c determines that the number of targets 100 is 1, the process proceeds to step ST2.

The operations after step ST2 are the same as those after step ST2 in the first embodiment, and therefore the description thereof will be omitted.
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, processing of the current signal is interrupted, and processing such as moving to processing of the received signal at the next time is performed.

The hardware configuration of the radar signal processing device 1 according to the third embodiment is also 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, in the same manner as the radar signal processing device 1 according to the first embodiment.

The radar signal processing device 1 according to the third embodiment determines the number of targets 100, and after determining in the target number detection unit 16 that the signal being handled is for one target 100, in the same manner as the radar signal processing device according to the first embodiment, it obtains the speed V of the target 100 with an expanded speed measurement range and the azimuth angle θ with respect to the target 100 by separating and estimating the phase element dependent on the azimuth angle θ with respect to the target 100 and the phase element dependent on the speed Vamb of the target 100, so that even when there is speed ambiguity, it is possible to obtain the speed of the target with an expanded speed measurement range and the azimuth angle with respect to the target with high accuracy.

The target number detection unit 16 shown in the third embodiment may be configured to be included in the radar signal processing device 1 according to the second embodiment.
When the radar signal processing device 1 according to the second embodiment is equipped with the target number detection unit 16 shown in the third embodiment, in the radar signal processing device 1 according to the second embodiment, in the flow shown in FIG. 7 , after the target signal detection step ST1, the target number detection unit 16 performs the processes of steps ST11 to ST14 shown in FIG. 9 . 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 the processes of steps ST2, ST3, ST4a, ST5, ST6, and ST7 shown in FIG. 7 are performed.

Furthermore, it is possible to freely combine the embodiments, modify any of the components in each embodiment, or omit any of the components in each embodiment.

The radar signal processing device disclosed herein is suitable for applications including automotive radar devices.

1 radar signal processing device, 2 ₁ to 2 ₃ transmitting antennas, 3 ₁ to 3 ₄ receiving antennas, 11 target detection section, 12, 12A angle measurement compensation processing section, 13 speed estimation section, 14 speed compensation processing section, 15 angle measurement section, 16 target number detection section, 100 target.

Claims (10)

a target detection unit that detects a distance to the target, an angle of arrival, and a speed of the target by using received signals corresponding to incoming waves from the multiple receiving antennas that receive the reflected waves from 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 is dependent on an azimuth angle with respect to the target and is not influenced 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 is dependent on the azimuth angle, and obtains an angle-compensated spatial signal that is not influenced by a phase element that is dependent on the azimuth angle with respect to 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, judges whether or not there is aliasing of the speed obtained by the target detection unit using a 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 judgment result;
a velocity compensation processing unit that estimates a phase element that is dependent on the velocity of the target and is not influenced by a phase element due to an azimuth angle to the target for the spatial signal, corrects the spatial signal using the phase element that is dependent on the velocity, and obtains a velocity-compensated spatial signal that is not influenced by a phase element that is dependent on the velocity to the target;
an angle measurement unit that performs angle measurement signal processing on the velocity-compensated spatial signal obtained by the velocity compensation processing unit to obtain an azimuth angle with respect to the target;
A radar signal processing device comprising: The spatial signal is represented in a matrix format, with columns representing transmissions and rows representing receptions, and each element in the matrix has a range/azimuth phase element and a velocity 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 phase element from the spatial signal and leaving only the velocity phase element,
The velocity-compensated spatial signal obtained by the velocity compensation processing unit is obtained by a process of canceling a velocity phase element from the spatial signal and leaving only a distance/azimuth phase element.
2. The radar signal processing device according to claim 1. The spatial signal is represented in a matrix format, with columns representing transmissions and rows representing receptions, and each element in the matrix has a range/azimuth phase element and a velocity phase element;
The angle-compensated spatial signal obtained by the angle measurement compensation processing unit is obtained by performing a DOA estimation process of the direction of arrival from the spatial signal without being affected by the speed of the target, estimating an azimuth angle to the target, and using the estimated azimuth angle resulting from the DOA estimation process, canceling the distance/azimuth phase element from the spatial signal and leaving a speed phase element.
2. The radar signal processing device according to claim 1. The spatial signal is represented in a matrix format, with columns representing transmissions and rows representing receptions, and each element in the matrix has a range/azimuth phase element and a velocity phase element;
The angle-compensated spatial signal obtained by the angle measurement compensation processing unit is obtained by performing a DOA estimation process of the direction of arrival from the spatial signal without being affected by the speed of the target, estimating an azimuth angle to the target, extracting a signal having the distance/azimuth angle phase element and the speed phase element corresponding to the distance to the target, expanding the signal compensation range to the signal extracted by the distance to the target, and performing a phase compensation process using the estimated azimuth angle that is a result of the DOA estimation process.
2. The radar signal processing device according to claim 1. The estimated velocity of the target obtained by the velocity estimation unit is
When the result of the determination of the presence or absence of a turnaround indicates a positive turnaround, a value obtained by adding a value twice the maximum speed value of a speed measurement range for the speed of the target obtained by the target detection unit to the speed of the target obtained by the target detection unit is determined;
When the result of the determination of the presence or absence of a turnaround indicates a negative turnaround, a value obtained by subtracting from the speed of the target obtained by the target detection unit a value twice the maximum speed value of a speed measurement range for the speed of the target obtained by the target detection unit is set as a value;
If the result of the determination of the presence or absence of aliasing indicates that there is no positive or negative aliasing, the velocity of the target obtained by the target detection unit is used.
The radar signal processing device according to any one of claims 1 to 4. The radar signal processing device according to any one of claims 1 to 4, wherein the phase element dependent on the target's speed, which is not affected by the phase element due to the azimuth angle to the target, for the spatial signal in the speed compensation processing unit, is the estimated speed of the target obtained by the speed estimation unit. The radar signal processing device according to any one of claims 1 to 4, further comprising a target number detection unit that performs spatial averaging of a reception correlation matrix obtained using the spatial signal, determines the number of targets based on an eigenvalue obtained using the reception correlation matrix that has been subjected to the spatial averaging process, and executes subsequent processing if the number of targets is one, and interrupts subsequent processing if the number of targets is two or more. a target signal detection step in which a target detection unit acquires 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 and transmitted signals corresponding to the transmitted waves from the multiple transmitting antennas;
an angle-of-arrival compensation step in which an angle measurement compensation processing unit acquires an angle-compensated signal in which the distance/azimuth angle phase elements are cancelled from a signal having a distance/azimuth angle phase element and a velocity phase element obtained by a combination of the plurality of transmitting antennas and the plurality of receiving antennas;
a velocity estimation step of performing a fast Fourier transform process on the angle-compensated signal, determining whether or not the velocity of the target is aliased using a processing result obtained by the fast Fourier transform process, and obtaining an estimated velocity of the target from the velocity of the target based on the result of the determination;
a velocity compensation step in which a velocity compensation processing unit obtains a velocity compensated signal in which the velocity phase element is cancelled from a signal having the range/azimuth phase element and the velocity phase element;
an angle measuring step in which an angle measuring unit performs signal processing of the velocity compensated signal angle measurement to obtain an azimuth angle with respect to the target;
A radar signal processing method comprising: a target signal detection step in which transmission waves transmitted in a time division manner from a plurality of transmitting antennas are reflected by a target, and a distance to the target, an angle of arrival, and a speed of the target are obtained using reception signals corresponding to the arrival waves from the plurality of receiving antennas which receive the reflected waves from the target, and transmission signals corresponding to the transmission waves from the plurality of transmitting antennas;
an angle-of-arrival compensation step for obtaining an angle-compensated signal in which the distance and azimuth phase elements are cancelled from a signal having distance and azimuth phase elements and a velocity phase element obtained by a combination of the plurality of transmitting antennas and the plurality of receiving antennas;
a velocity acquisition step of performing a fast Fourier transform process on the angle-compensated signal, determining whether or not there is aliasing in the velocity of the target using a processing result obtained by the fast Fourier transform process, and obtaining an estimated velocity of the target from the velocity of the target based on the result of the determination;
a velocity compensation step of obtaining a velocity compensated signal from the signal having the range-azimuth phase element and the velocity phase element, in which the velocity phase element is cancelled;
an angle measurement step of performing signal processing of the velocity compensated signal angle measurement to obtain an azimuth angle to the target;
A radar signal processing program that causes a computer to execute the above. a target signal detection step in which transmission waves transmitted in a time division manner from a plurality of transmitting antennas are reflected by a target, and a distance to the target, an angle of arrival, and a speed of the target are obtained using reception signals corresponding to the arrival waves from the plurality of receiving antennas which receive the reflected waves from the target, and transmission signals corresponding to the transmission waves from the plurality of transmitting antennas;
an angle-of-arrival compensation step for obtaining an angle-compensated signal in which the distance and azimuth phase elements are cancelled from a signal having distance and azimuth phase elements and a velocity phase element obtained by a combination of the plurality of transmitting antennas and the plurality of receiving antennas;
a velocity acquisition step of performing a fast Fourier transform process on the angle-compensated signal, determining whether or not there is aliasing in the velocity of the target using a processing result obtained by the fast Fourier transform process, and obtaining an estimated velocity of the target from the velocity of the target based on the result of the determination;
a velocity compensation step of obtaining a velocity compensated signal from the signal having the range-azimuth phase element and the velocity phase element, in which the velocity phase element is cancelled;
an angle measurement step of performing signal processing of the velocity compensated signal angle measurement to obtain an azimuth angle to the target;
A recording medium storing a program for causing a computer to execute the above.

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