WO2023218632A1

WO2023218632A1 - Radar device and target detection method

Info

Publication number: WO2023218632A1
Application number: PCT/JP2022/020185
Authority: WO
Inventors: 美裕中尾; 幸徳赤峰
Original assignee: 株式会社日立製作所
Priority date: 2022-05-13
Filing date: 2022-05-13
Publication date: 2023-11-16

Abstract

A radar device (1) comprises a plurality of antennas arranged two-dimensionally in a coordinate system having a first axis and a second axis as coordinate axes. The radar device (1) comprises a first axis direction estimation unit (35) that calculates, on the basis of received signals, a first peak value by scanning angles in the first axis direction in terms of a first spectrum intensity based on steering vectors of the antennas in the first axis direction. The radar device (1) also comprises a second axis direction estimation unit (37) that calculates, on the basis of received signals and the first peak value, a second peak value by scanning angles in the second axis direction in terms of a second spectrum intensity of the received signals based on steering vectors of the antennas in the second axis direction.

Description

Radar device and target detection method

The present invention relates to a radar device and a target object detection method.

For example, a millimeter wave radar mounted on a vehicle or the like can determine the distance, speed, and angle of a target by receiving the reflected waves of transmitted waves reflected by the target. Millimeter wave radar can calculate the horizontal angle if multiple receiving antennas are arranged horizontally, and can calculate the height of a target if multiple receiving antennas are arranged vertically (e.g. , see Patent Document 1). There is also a method of determining the horizontal angle and vertical angle by arranging a plurality of receiving antennas in a plane to generate a two-dimensional spectrum (for example, see Patent Document 2).

Japanese Patent Application Publication No. 9-288178 JP2017-58359

However, among the above-mentioned conventional techniques, in the method of estimating the estimated horizontal orientation and vertical orientation, respectively, as in Patent Document 1, when multiple targets are detected, multiple horizontal orientation estimation results and multiple vertical orientation estimation results are used. You need to combine the results correctly. If there is no other sensor information or large difference in signal level, there is a problem in that it is difficult to combine them correctly. In addition, while the method of generating a two-dimensional spectrum using multiple receiving antennas arranged in a plane can determine the correct combination of horizontal and vertical orientations of multiple targets, it is also difficult to generate a two-dimensional spectrum. There is a problem that peak search requires a huge amount of calculation.

The present invention has been made in consideration of the above points, and an object of the present invention is to accurately detect a target while suppressing the amount of calculation.

In order to solve the above-mentioned problems, one aspect of the present invention provides a radar device that estimates the direction of arrival of a received signal in which a reflected wave of a transmitted signal reflected by a target object is received via a plurality of antennas, a signal processing unit that processes a received signal to estimate the direction of arrival; the plurality of antennas are two-dimensionally arranged in a coordinate system having a first axis and a second axis as coordinate axes; , calculate a steering vector of the antenna in the first axis direction based on the received signal, and scan an angle in the first axis direction at a first spectral intensity of the received signal based on the steering vector to obtain a first steering vector. a first axis direction estimating unit that calculates a peak value of and performs processing for estimating the direction of arrival regarding the first axis based on the first peak value; and a first axis direction estimation unit that calculates a peak value of to calculate a steering vector of the antenna in the second axis direction, and calculate a second peak value by scanning an angle in the second axis direction at a second spectral intensity of the received signal based on the steering vector. , a second axis direction estimator that performs a process of estimating the direction of arrival regarding the second axis based on the second peak value.

According to the present invention, target detection can be performed with high accuracy while suppressing the amount of calculation.

1 is a diagram showing the configuration of a radar device according to a first embodiment; FIG. FIG. 3 is a diagram showing the angle of the reflected wave from the target with respect to the first axis and the angle of the reflected wave from the target with respect to the second axis according to the first embodiment. FIG. 6 is a diagram showing how to use two-dimensionally arranged receiving antennas in a second axis spatial averaging processing section and a first axis direction estimating section. It is a figure which shows the process in a scanning range limitation process part and a 2nd axis direction estimation part. It is a flowchart which shows the flow of processing from the second axis spatial averaging processing section to the second axis direction estimating section of the signal processing section. FIG. 3 is a diagram showing an example of antenna arrangement according to the first embodiment. It is a figure which shows an example of the calculation result of the one-dimensional angular spectrum intensity of a 1st axis direction. It is a figure which shows an example of the calculation result of the two-dimensional angular spectrum intensity of a 2nd axis direction. 7 is a diagram showing an example of antenna arrangement according to Embodiment 2. FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiments are examples for explaining the present invention, and are omitted and simplified as appropriate for clarity of explanation. The present invention can also be implemented in various other forms. Unless otherwise specified, each component may be singular or plural.

When there are multiple components that have the same or similar functions, they are distinguished by attaching different subscripts to the same reference numeral. If there is no need to distinguish between these multiple components, the subscripts may be omitted from the description.

In the embodiments, processes performed by executing a program may be described. Here, a computer executes a program using a processor (for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit)), and performs processing determined by the program while using storage resources (for example, a memory). Therefore, the main body of processing performed by executing a program may be a processor. The main body of the processing performed by executing the program may be an arithmetic unit, and may include a dedicated circuit that performs specific processing. Here, the dedicated circuit is, for example, an FPGA (Field Programmable Gate Array), an ASIC (Application Specific Integrated Circuit), or a CPLD (Complex Programmable Logic Device).

[Embodiment 1]
(Configuration of radar device 1 according to Embodiment 1)
FIG. 1 is a diagram showing the configuration of a radar device 1 according to the first embodiment. The radar device 1 is mounted, for example, on a vehicle such as a railroad or a car.

The radar device 1 is used to detect targets existing around or in front of the vehicle. The radar device 1 acquires target data by transmitting a transmitted wave that is reflected by a target object and receiving a reflected wave that returns to the radar device 1 . The data on the target includes the distance to the target, the relative speed of the target with respect to the radar device 1, the direction in which the target exists, and the like.

As shown in FIG. 1, the radar device 1 includes a transmitting section 10, a receiving section 20, a signal processing section 30, and a memory section 40.

The transmitter 10 includes an oscillator 11 and a transmitting antenna 12. In target object detection using millimeter wave radar, distance and speed information are calculated based on the results of transmitting and receiving a chirp signal whose frequency changes linearly depending on time, which is generally referred to as the FMCW (Frequency Modulated Continuous Wave) method. The oscillator 11 receives information about a signal to be transmitted from the signal control section 31 in the signal processing section 30 and generates a chirp signal. The generated chirp signal is transmitted as a transmission wave from the transmission antenna 12. The transmitted wave is reflected by a target object such as another vehicle, and becomes a reflected wave.

The receiving unit 20 includes a plurality of receiving antennas 21, a mixer 22 connected to each receiving antenna 21, and an A/D (Analog to Digital) converter 23. A part of the reflected wave reflected by the target object is received by the receiving antenna 21. The received signal that has received the reflected wave is input to the mixer 22 . The mixer 22 generates a beat signal by mixing the received signal and the transmitted signal (oscillation signal of the oscillator 11). The beat signal is converted into a digital signal by the A/D converter 23 and output to the signal processing section 30.

In the signal processing unit 30, the beat signal after A/D conversion is used to perform Fourier transform, distance/velocity calculation, first axis direction estimation, and second axis direction estimation.

The memory section 40 stores information necessary for the signal processing section 30, such as antenna coordinate information and information on modulation settings of the transmission signal. The antenna coordinate information is, for example, the distance d1 in the first axis direction and the distance d2 in the second axis direction of the two-dimensionally arranged receiving antennas 21 (described later with reference to FIG. 6). Further, the antenna coordinate information includes offset values d12, d13, . . . of other receiving antenna subarrays with respect to the receiving antenna subarray that is a reference for the receiving antenna 21 in the first axis direction. Similarly, the antenna coordinate information includes offset values d22, d23, . . . of other columns with respect to the reference column of the receiving antenna 21 in the second axis direction (described later with reference to FIG. 9).

The signal transmitted from the transmitting antenna 12 is received by the receiving antenna 21 through a route that is twice the distance to the target object. A delay time occurs between the time when a signal whose frequency changes depending on the time of day is transmitted and when it is reflected by a target object and reaches the receiving antenna 21, resulting in a frequency difference between the transmitted signal and the received signal. occurs. The longer the distance to the target, the greater the delay time and the greater the frequency difference between the transmitted and received signals. The beat signal after A/D conversion is Fourier transformed in the time direction, thereby determining the distance to the target based on the frequency difference.

The Fourier transform unit 32 performs two-dimensional FFT (Fast Fourier Transform) on the received signal input to the signal processing unit 30 as described above. A power spectrum of distance and velocity is obtained by FFT processing. The distance/velocity calculation unit 33 searches for a peak bin that is equal to or greater than a threshold value from the power spectrum of the distance/velocity obtained by the Fourier transform unit 32, thereby determining the distance and velocity of the detected target.

Since the Fourier transform unit 32 performs FFT processing on the signals received by each receiving antenna 21, it obtains the same number of distance and velocity spectra as the number of channels of the receiving antenna 21. Here, the obtained peak bin is the same for all receiving antennas 21, but the complex information of the amplitude and phase of the frequency spectrum at the peak bin differs for each receiving antenna 21. Since the way in which the complex information differs for each receiving antenna 21 is determined by the antenna arrangement and the target object direction, the direction of the target object is determined from the complex information obtained from each receiving antenna 21 and the antenna arrangement.

The subsequent processing of the distance/speed calculation unit 33 is performed for each calculated distance and speed bin. Hereinafter, the received signal refers to the complex signal at the peak bin of the distance and velocity spectra.

The processing after the second axis spatial averaging processing unit 34 is the processing for determining the direction of the target object.

FIG. 2 is a diagram showing the angle of the reflected wave from the target with respect to the first axis and the angle of the reflected wave from the target with respect to the second axis according to the first embodiment. In this embodiment, it is assumed that the receiving antenna has a two-dimensional arrangement with the first axis and the second axis, and the angle θ of the target with respect to the first axis is defined as shown in FIG. The angle φ of the target object is defined as shown in FIG. 2(b). For example, the first axis is the horizontal direction and the second axis is the vertical direction, but the invention is not limited thereto.

FIG. 3 is a diagram showing how to use the two-dimensionally arranged receiving antenna 21 in the second axis spatial averaging processing section and the first axis direction estimation section. The second axis spatial averaging processing unit 34 performs processing for using the two-dimensionally arranged receiving antennas 21 as one-dimensional antennas. Specifically, the received signals obtained by the two-dimensionally arranged receiving antennas 21 are grouped into each receiving antenna array 21A having the same second axis coordinates, the correlation matrix R of the received signals of each group is determined, and the correlation matrix R of the received signals of each group is calculated. Performs averaging processing of the correlation matrix. Details will be described later. The correlation matrix R of the received signal obtained here is regarded as the correlation matrix of the received signal by the one-dimensional antenna array parallel to the first axis.

The first axis direction estimation unit 35 uses the correlation matrix R obtained by the second axis spatial averaging processing unit 34 and the antenna coordinates regarded as one-dimensional to estimate the one-dimensional angular spectrum intensity P1(θ) regarding the angle θ. Do calculations. Then, the first axis direction estimating unit 35 estimates the angle θ indicating the direction in which the target exists with respect to the first axis by determining the angle θ at which the one-dimensional angular spectrum intensity P1(θ) is equal to or greater than the threshold value. For example, when the first axis is in the horizontal direction, the calculation is to find the horizontal angle. The direction is estimated using a known method such as Capon or MUSIC (Multiple Signal Classification).

FIG. 4 is a diagram showing processing in the scanning range limitation processing section 36 and the second axis direction estimation section 37. The scanning range limitation processing unit 36 determines the angular range of the first axis in which two-dimensional direction estimation is performed based on the result of the first axis direction estimation unit 35. The angular range of the first axis in which the two-dimensional direction estimation is performed is a predetermined range that includes the angle θ at which the one-dimensional angular spectrum intensity P1(θ) is equal to or greater than the threshold value in the first axial direction estimator 35.

The second axis direction estimating unit 37 limits the range of the angle θ determined by the scanning range limiting processing unit 36, calculates the two-dimensional angle spectrum intensity P2 (θ, φ) regarding the angle φ, and calculates the two-dimensional angle A second axis direction estimation is performed to obtain an angle φ at which the spectral intensity P2(θ, φ) is equal to or greater than a threshold value. By estimating the direction of the second axis, the angle φ indicating the direction in which the target exists with respect to the second axis is estimated, thereby determining the angle θ of the target with respect to the first axis and the angle φ with respect to the second axis.

Next, the second axis spatial averaging processing section 34, the first axis direction estimation section 35, the scanning range limitation processing section 36, and the second axis direction estimation section 37 will be explained. First, the antenna arrangement will be explained.

(Antenna arrangement example according to Embodiment 1)
FIG. 6 is a diagram showing an example of antenna arrangement according to the first embodiment. In this embodiment, the reception antenna array is composed of 18 elements of reception antennas Rx1 to Rx18 arranged in a grid with six columns in the first axis direction and three columns in the second axis direction. Let G1 be the receiving antenna subarray of Rx1 to Rx6, G2 be the receiving antenna subarray of Rx7 to Rx12, and G3 be the receiving antenna subarray of Rx13 to Rx18.

Let d1 be the interval between the six receiving antenna elements arranged parallel to the first axis in the receiving antenna subarrays G1, G2, G3, and the second axis coordinate difference ( interval) is set as d2. When a plurality of antennas arranged in a grid are divided by a plurality of parallel lines, a plurality of reception antenna subarrays G1, G2, and G3 are arranged in the second axis direction and are located at the same distance from the second axis. This is an example of a linear antenna subarray including the same number of elements.

Note that the receiving antennas Rx1 to Rx18 may be virtual antennas obtained by MIMO (Multiple-Input and Multiple-Output) or other extended signal processing. When using a virtual antenna, a virtual received signal at the virtual antenna may be generated before the second axis spatial averaging process.

(Processing of the second axis spatial averaging processing unit 34, first axis direction estimation unit 35, and second axis direction estimation unit 37)
FIG. 5 is a flowchart showing the flow of processing from the second axis spatial averaging processing unit 34 to the second axis direction estimation unit 37 of the signal processing unit 30.

First, in step S1, the second axis spatial averaging processing unit 34 groups antenna arrays having the same second axis coordinates as subarrays (one-dimensional antenna subarray generation process). Let G1 be the receiving antenna subarray of Rx1 to Rx6, G2 be the receiving antenna subarray of Rx7 to Rx12, and G3 be the receiving antenna subarray of Rx13 to Rx18.

Here, the received signals obtained by each receiving antenna Rx1 to Rx18 are assumed to be s1 to s18. Let the signal of receiving antenna subarray G1 be s(1)=[s1, s2, s3, s4, s5, s6]. Let the signal of receiving antenna subarray G2 be s(2)=[s7, s8, s9, s10, s11, s12]. It is assumed that the signal of receiving antenna subarray G3 is s(3)=[s13, s14, s15, s16, s17, s18].

Next, in step S2, the second axis spatial averaging processing unit 34 uses the received signals s(1), s(2), and s(3) obtained from each receiving antenna subarray to create correlation matrices R1, R2, Calculate R3 (subarray correlation matrix calculation process). Next, in step S3, the second axis spatial averaging processing unit 34 calculates three correlation matrices R1, R2 calculated from the received signals s(1), s(2), s(3) of each receiving antenna sub-array. , R3 is generated (correlation matrix averaging process).

The first axial direction estimation unit 35 calculates the one-dimensional angular spectrum intensity necessary for first axial direction estimation. In order to estimate the first axis direction, a one-dimensional steering vector is required when two-dimensionally arranged antennas are used as one-dimensional antennas. First, in step S4, the first axis direction estimation unit 35 generates a one-dimensional steering vector a1 (θ) based on the antenna coordinate information (first axis one-dimensional steering vector generation process). The one-dimensional steering vector a1(θ) is expressed as in equation (1) using the coordinates of the receiving antenna along the first axis. λ indicates wavelength. Further, θ is a value that changes depending on the direction of the desired spectrum.

Next, in step S5, the first axis direction estimation unit 35 uses the matrix Rmean obtained in step S3 and the one-dimensional steering vector a1(θ) generated in step S4 to determine the one-dimensional angular spectrum intensity in the first axis direction. P1(θ) is calculated (first axis one-dimensional direction spectrum calculation process). A method for calculating the one-dimensional angular spectrum intensity P1(θ) is expressed as in equation (2) when using the Capon method, for example.

The one-dimensional angular spectrum intensity P1(θ) in the first axis direction is calculated by scanning the angle θ in a predetermined range predetermined from the viewing angle of the antenna.

FIG. 7 shows an example of the one-dimensional angular spectrum intensity P1(θ) obtained when two targets with different first axis directions exist in the same distance/velocity bin. Calculation of the one-dimensional angular spectrum intensity P1 (θ) is not limited to Capon, and for example, DBF (Digital Beamforming), MUSIC, or the like may be used.

Next, in step S6, the first axial direction estimation unit 35 extracts the angle θ when the one-dimensional angular spectrum intensity P1(θ) exceeds a predetermined threshold (first axial direction peak extraction process). In this embodiment, it is assumed that θ=α1, α2 are extracted as the first axis directions.

Next, in step S7, the scanning range limitation processing unit 36 receives the first axis peak angles α1 and α2 extracted by the first axis direction estimation unit 35, and calculates the two-dimensional angle by the next second axis direction estimation unit 37. The calculation range of the angular spectrum intensity P2 (θ, φ) is determined and listed. For example, in the case of 1 degree increments within the ±1 degree range of each of α1 and α2, the second axis direction estimating unit 37 inputs (α1-1, α1, α1+1) and (α2-1, α2, α2+1) to θ. Output as the scan range. For example, this list may include only α1 and α2. If there is a sufficient number of antenna elements per group in the receiving antenna sub-array parallel to the first axis, and beam scanning for first axis direction estimation is performed in detail, the second axis direction estimation list only contains α1 and α2. However, sufficient accuracy can be obtained.

The second axis direction estimation unit 37 calculates the two-dimensional angular spectrum intensity P2 (θ, φ) necessary for second axis direction estimation. First, in step S8, the second axis direction estimation unit 37 generates an 18×18 correlation matrix R using the received signals s1 to s18 of the two-dimensionally arranged receiving antennas (full antenna array correlation matrix calculation process). .

In order to estimate the second axis direction, a two-dimensional steering vector of the two-dimensionally arranged receiving antenna 21 is required. Next, in step S9, the second axis direction estimation unit 37 generates a two-dimensional steering vector a2 (θ, φ) based on the antenna coordinate information (second axis two-dimensional steering vector calculation process). The two-dimensional steering vector a2 (θ, φ) is expressed as in equation (3). At this time, θ is changed by a value in a list determined by the scanning range limiting processing unit 36, and first, it is changed by a value in a list including α1.

Next, in step S10, the second axis direction estimating unit 37 calculates a two-dimensional angular spectrum intensity P2 for θ determined by the scanning range limiting processing unit 36 and φ in a predetermined range determined in advance from the viewing angle of the antenna. (θ, φ) (two-dimensional directional spectrum calculation process within a predetermined range). The two-dimensional angular spectrum intensity P2 (θ, φ) is calculated as shown in equation (4) using the two-dimensional steering vector a2 (θ, φ) and the correlation matrix R.

Finally, in step S11, the second axis direction estimation unit 37 extracts θ and φ when the two-dimensional angular spectrum intensity P2 (θ, φ) is equal to or greater than a predetermined threshold (direction peak extraction process within a predetermined range). . The second axis direction estimation unit 37 similarly performs the processing of steps S9 to S11 for the list including α2.

FIG. 8 is a diagram showing an example of the calculation result of the two-dimensional angular spectrum intensity P2 (θ, φ) in the second axis direction. FIG. 8 shows an example of the two-dimensional angular spectrum intensity P2 (θ, φ) obtained when there are two targets with the same distance and speed bin that are different in both the first and second axis directions. .

If there are multiple peaks obtained by the distance/velocity calculation unit 33, the processes of steps S1 to S11 are repeated for each distance/velocity bin.

In this embodiment, the receiving antenna 21 has a rectangular arrangement consisting of 18 elements in total, 6 elements in the first axis direction and 3 elements in the second axis direction, but they are arranged in the first axis direction and the second axis direction. The combination of the number of antenna elements is not limited to this. Furthermore, the number of targets to be detected is not limited to this.

(Effects of Embodiment 1)
In this embodiment, the receiving antennas are grouped into antenna arrays parallel to the first axis that are two-dimensionally arranged in a coordinate system having the first axis and the second axis as the coordinate axes. Then, a peak angle in the first axis direction at which the spectrum intensity of the received signal in the first axis direction reaches a peak value is calculated. Then, calculation of the peak angle in the second axis direction at which the spectrum intensity of the received signal in the second axis direction has a peak value is performed within a limited range based on the peak angle in the first axis direction.

Therefore, according to the present embodiment, the direction of arrival of the reflected wave of the transmitted signal reflected by the target object, that is, the angle of the position of the target object with respect to the two axes, can be determined with high precision while suppressing the amount of calculation. Further, it is possible to achieve high resolution in millimeter wave radar.

Furthermore, in this embodiment, the received signals are grouped for each antenna subarray, the received signals received through different antennas in the second axis direction are averaged, and the first Calculate the axial steering vector. Therefore, according to the present embodiment, it is possible to calculate a steering vector in the first axis direction based on the received signals of a plurality of receiving antennas having different coordinates of the second axis.

Furthermore, in the present embodiment, in the plurality of antennas, the number of elements lined up in the first axis direction is greater than or equal to the number of elements lined up in the second axis direction. If the number of elements aligned in the first axis direction is sufficiently larger than the number of elements aligned in the second axis direction, when calculating the peak value of the two-dimensional angular spectrum intensity P2 (θ, α), the angle θ in the first axis direction The scanning range can be made smaller. Furthermore, only the angle θ that gives the peak value of the one-dimensional angular spectrum intensity P1(θ) can be used. Therefore, the amount of calculation can be suppressed.

Additionally, in this embodiment, multiple antennas can be configured using virtual antennas.

(Modification of Embodiment 1)
If the number of antennas lined up in the second axis direction is sufficiently large compared to the number of targets with different second axis angles, after completing the processing up to step S11, the first and second axes are exchanged and steps S1 to The accuracy of the estimated angle may be confirmed by performing S11 again. In this case, the signals obtained by the two-dimensionally arranged receiving antennas 21 are grouped into receiving antenna arrays having the same first axis coordinates, such as Rx1, Rx7, and Rx13 in FIG. 6, for example. Then, the correlation matrix of the received signals of each group is determined, and the correlation matrices of all groups are averaged.

In the case of the antenna arrangement as shown in FIG. 6, the receiving antenna is composed of a group of six antenna subarrays. The correlation matrix of the received signal obtained here is regarded as the correlation matrix of the received signal by the one-dimensional antenna array parallel to the second axis.

Then, the angle φ indicating the direction in which the target exists with respect to the second axis is estimated using the correlation matrix after the averaging process and the antenna coordinates that are regarded as a one-dimensional array in the second axis direction. From the obtained second axis one-dimensional direction estimation information φ, an angular range of the second axis is determined for which the direction regarding the first direction is estimated using the two-dimensional steering vector. The direction of the target object with respect to the first axis is estimated within the angle range of the second axis for which direction estimation is performed, and the angle of the target object with respect to the first axis and the angle with respect to the second axis are determined.

In a modification of the first embodiment, after performing the process of estimating the direction of arrival regarding the first axis and the process of estimating the direction of arrival regarding the second axis, the first axis and the second axis are exchanged, and the first axis after the exchange is A process for estimating the direction of arrival regarding the axis and a process for estimating the direction of arrival regarding the second axis are performed. Therefore, by checking whether the estimated values of the angle in the first axis direction and the second axis direction match before and after the first axis and the second axis are exchanged, it is possible to guarantee the angle estimation accuracy while suppressing the amount of calculation.

[Embodiment 2]
In the antenna arrangement example of Embodiment 1 shown in FIG. 6, there are antenna arrays parallel to the first axis and antenna arrays parallel to the second axis, but antennas with different coordinates in the second axis direction are parallel to the second axis. They do not have to be parallel. In this embodiment, an antenna arrangement different from the antenna arrangement example of Embodiment 1 will be described.

(Antenna arrangement according to Embodiment 2)
FIG. 9 is a diagram showing an example of antenna arrangement according to the second embodiment. Also in this embodiment, the reception antenna array is composed of 18 elements of reception antennas Rx1 to Rx18 arranged in a grid with six rows in the first axis direction and three rows in the second axis direction. The receiving antenna sub-array of Rx1 to Rx6 is G11, the receiving antenna sub-array of Rx7 to Rx12 is G12, and the receiving antenna sub-array of Rx13 to Rx18 is G13.

In the receiving antenna subarrays G11, G12, and G13, the interval between the six receiving antenna elements arranged parallel to the first axis is d1, and the second axis coordinate difference (interval) of the antenna subarrays having different second axis coordinates is d2. . Let d12 be the difference (offset value) in the first axis coordinates between the receiving antenna subarray G11 and the receiving antenna subarray G12, and let d13 be the difference (offset value) in the first axis coordinates between the receiving antenna subarray G12 and the receiving antenna subarray G13. A plurality of reception antenna subarrays G11, G12, and G13 are arranged in the second axis direction when a plurality of antennas arranged in a grid are divided by a plurality of parallel lines, and each one is arranged at a different distance from the second axis. 1 is an example of a linear antenna subarray containing the same number of elements located in a row.

In this embodiment, the antenna arrangement is different from the first embodiment. On the other hand, the two-axis spatial averaging process (steps S1 to S3), the two-dimensional direction estimation process (steps S4 to S6), the scanning range limiting process (step S7), and the entire antenna array correlation matrix calculation process (step S8) are described in the first embodiment. It is similar to

In the second axis two-dimensional steering vector calculation process (step S9) of this embodiment, the two-dimensional steering vector a2 (θ, φ) of this embodiment is calculated as follows. That is, in equation (3) expressing the two-dimensional steering vector a2 (θ, φ) of the first embodiment, the first term d1·n (n=0, 1, . . . ) in the exponential function of the components of the receiving antenna subarray G12. , 5), substitute (d12+d1·n) (n=0, 1,..., 5). Also, in equation (3), instead of (d13+d1·n) (n=0, 1,...,5). Therefore, the two-dimensional steering vector a2 (θ, φ) in this embodiment is expressed as in equation (5). The subsequent steps S10 and S11 can be performed in the same manner as in the first embodiment using the two-dimensional steering vector a2(θ, φ) of Equation (5).

(Effects of Embodiment 2)
In this embodiment, a plurality of antennas arranged in a grid are divided by a plurality of parallel lines, and it is assumed that a plurality of linear antenna sub-arrays including the same number of elements are arranged in the second axis direction. In this case, the plurality of antenna subarrays are each located at a different distance from the second axis. Therefore, the receiving antenna can be arranged flexibly. Furthermore, the radar device can be mounted on vehicles in various forms.

[Other embodiments]
(1)
In the calculation of the two-dimensional angular spectrum intensity P2 (θ, φ) of the second axis direction estimation unit 37, the angle of the one-dimensional angle spectrum intensity calculation of the first axis angle θ is determined according to the result of the first axis direction estimation unit 35. In addition to the range, the angular scanning range and/or scanning interval of the two-dimensional angular spectrum intensity calculation of the second axis angle φ may be changed.

For example, assume that the first axis is horizontal and the second axis is vertical. If a target is detected and the first axis direction is estimated, and it is estimated that there is a target in the direction of travel of the vehicle, etc. to which the radar device 1 is attached, it is determined whether the target is in front of the collision. It is important to judge whether it is at the top where it will not collide. Since the second axis direction estimation in this case is important, it is necessary to obtain it more accurately.

On the other hand, if a target is detected and the first axis direction is estimated, and it is estimated that the target is located outside the direction of travel of the vehicle to which the radar device 1 is attached, the possibility of a collision is low; The importance of the second axis direction is low. In this case, the second axis direction estimation may be less accurate than the case where detection is performed in the traveling direction. For this reason, the scanning interval of the angle in the two-dimensional angle spectrum intensity calculation of the second axis may be increased or the scanning range may be narrowed.

For example, by linking track information for railway vehicles or map information for cars with target detection, it can be determined whether the detected target is in front of the collision, or in a location other than the front, such as on the top of the vehicle, where it will not collide. You can judge. As a result of the first axis direction estimation, if it is determined that the target object is located outside the course where it will not collide, such as at the top of a curve or tunnel, two-dimensional angular spectrum intensity calculation is performed when estimating the second axis direction. Increase the angular scanning interval or narrow the scanning range.

In this way, by changing the scanning range or scanning interval of the angle in the second axis direction when calculating the second peak value according to the result of the estimation process by the first axis direction estimator, calculation resources and calculations can be reduced. Time allocation can be made different for each area. Therefore, it is possible to suppress the amount of calculation, improve calculation speed, and improve target object detection accuracy.

(2)
If the antenna arrays parallel to the first axis are arranged at equal intervals, spatial Fourier transform is performed between the receiving antennas using the received signals in each antenna subarray before processing by the first axis direction estimator 35. In the calculation of the one-dimensional angular spectrum intensity by the first axial direction estimator 35, the first axis direction estimator 35 calculates the peak value of the one-dimensional angular spectrum intensity P1(θ) according to the result of the spatial Fourier transform between the receiving antennas. The scanning range and/or scanning interval of the uniaxial angle θ may be determined.

By performing spatial Fourier transform between receiving antennas, several spectral intensities can be obtained at coarse angular intervals with less processing. It is considered that the existence probability of the target object is high around the angle where the value of the spectral intensity is large, so the angular interval of the one-dimensional angular spectral intensity calculation in the first axial direction estimator 35 is made small. On the other hand, since the probability of the existence of a target object is considered to be low around angles where the value of the spectral intensity is small, the angular interval of the one-dimensional angular spectral intensity calculation in the first axis direction estimation unit 35 is increased or omitted. do.

In this way, the received signal is subjected to spatial Fourier transform between multiple antennas, and the angular scanning range or scanning interval in the first axis direction when calculating the first peak value is calculated using the spatial Fourier transform result. The direction of the target can be determined efficiently by changing the direction according to the .

Note that the inter-receiving antenna spatial Fourier transform may be processed as a three-dimensional Fourier transform together with the two-dimensional Fourier transform for determining distance and velocity in the Fourier transform unit 32.

In this way, the area where highly accurate target detection is required is identified in advance, and the spectrum is calculated at fine angles within this specific area to perform highly accurate target detection, while reducing the detection accuracy outside the specific area. This allows highly accurate target detection without increasing the calculation load.

The present invention is not limited to the above-described embodiments, but includes various modifications. For example, the above-described embodiments have been described in detail to explain the present invention in an easy-to-understand manner, and the present invention is not necessarily limited to having all the configurations described. In addition, combinations of embodiments and modifications such as replacing part of the configuration of one embodiment with the configuration of another embodiment or adding the configuration of another embodiment to the configuration of one embodiment are also possible as long as there is no contradiction. be. Furthermore, it is possible to add, delete, replace, integrate, or distribute a part of the configuration of each embodiment. Furthermore, the configurations and processes shown in the embodiments can be distributed, integrated, or replaced as appropriate based on processing efficiency or implementation efficiency.

1: radar device, 10: transmitter, 11: oscillator, 12: transmitter antenna, 20: receiver, 21: receiver antenna, 21A: receiver antenna array, 22: mixer, 23: converter, 30: signal processor, 31: Signal control section, 32: Fourier transform section, 33: Distance/velocity calculation section, 34: Second axis spatial averaging processing section, 35: First axis direction estimation section, 36: Scanning range limitation processing section, 37: Second axis direction estimation section, 40: Memory section

Claims

A radar device that estimates the direction of arrival of a received signal in which a reflected wave of a transmitted signal reflected by a target is received via a plurality of antennas,
a signal processing unit that processes the received signal to estimate the direction of arrival;
The plurality of antennas are two-dimensionally arranged in a coordinate system having a first axis and a second axis as coordinate axes,
The signal processing section includes:
A steering vector of the antenna in the first axis direction is calculated based on the received signal, and an angle is scanned in the first axis direction at a first spectral intensity of the received signal based on the steering vector, and a first a first axis direction estimation unit that calculates a peak value and performs a process of estimating the arrival direction regarding the first axis based on the first peak value;
A steering vector of the antenna in the second axis direction is calculated based on the received signal and the first peak value, and a steering vector is calculated in the second axis direction at a second spectral intensity of the received signal based on the steering vector. and a second axis direction estimator that calculates a second peak value by scanning an angle and performs a process of estimating the direction of arrival with respect to the second axis based on the second peak value. radar equipment.
The radar device according to claim 1,
The plurality of antennas are arranged in a grid,
When it is assumed that the plurality of antennas are divided by a plurality of parallel lines and a plurality of linear antenna subarrays including the same number of elements are arranged in the second axis direction,
The radar device characterized in that the plurality of antenna subarrays are located at the same distance or at different distances from the second axis.
The radar device according to claim 1,
an averaging processing unit that groups the received signals for each of the antenna subarrays and performs averaging processing of the received signals received via the antennas that are different in the second axis direction;
The first axial direction estimator includes:
A radar device characterized in that a steering vector in the first axis direction is calculated based on the received signal averaged by the averaging processing section.
The radar device according to claim 1,
The radar apparatus is characterized in that the number of elements of the plurality of antennas arranged in the first axis direction is greater than or equal to the number of elements arranged in the second axis direction.
The radar device according to claim 1,
A radar device characterized in that the plurality of antennas include a virtual antenna.
The radar device according to claim 1,
The second axial direction estimator includes:
The angular scanning range in the first axis direction is limited to a predetermined range including the first peak value, and the angular scanning range in the second axial direction is scanned to calculate the second peak value. Characteristic radar equipment.
The radar device according to claim 1,
The second axial direction estimator includes:
A radar characterized in that a scanning range or a scanning interval of the angle in the second axis direction when calculating the second peak value is determined according to the result of the estimation process by the first axis direction estimator. Device.
The radar device according to claim 1,
Performing a spatial Fourier transform between the plurality of antennas on the received signal,
A radar device characterized in that an angular scanning range or scanning interval in the first axis direction when calculating the first peak value is determined according to a result of the spatial Fourier transform.
The radar device according to claim 1,
After performing the process of estimating the direction of arrival regarding the first axis and the process of estimating the direction of arrival regarding the second axis, the first axis and the second axis are exchanged, and the first axis after the exchange is performed. A radar device characterized in that it performs a process of estimating the direction of arrival with respect to the second axis, and a process of estimating the direction of arrival with respect to the second axis.
A target object detection method performed by a radar device that estimates the direction of arrival of a received signal in which a reflected wave of a transmitted signal reflected by a target object is received via a plurality of antennas, the method comprising:
The radar device has a signal processing step of processing the received signal to estimate the direction of arrival,
The plurality of antennas are two-dimensionally arranged in a coordinate system having a first axis and a second axis as coordinate axes,
The signal processing step includes:
The radar device calculates a steering vector of the antenna in the first axis direction based on the received signal, and scans an angle in the first axis direction at a first spectral intensity of the received signal based on the steering vector. a first axis direction estimation step of calculating a first peak value and performing estimation processing of the arrival direction regarding the first axis based on the first peak value;
The radar device calculates a steering vector of the antenna in the second axis direction based on the received signal and the first peak value, and calculates the steering vector of the antenna in the second spectral intensity of the received signal based on the steering vector. a second axis direction estimation step of calculating a second peak value by scanning an angle in the second axis direction, and performing an estimation process of the arrival direction regarding the second axis based on the second peak value. A target object detection method characterized by the following.