JP2020186974A - Signal processing device, radar device, and signal processing method - Google Patents

Abstract

To achieve both the solution of phase fold-back problem and the improvement of accuracy of an azimuth that represents a radio wave arrival direction.SOLUTION: A signal processing device comprises an azimuth calculation unit 471, a first decomposition unit 472, and a first selection unit 473. The azimuth calculation unit 471 calculates the azimuth that represents a radio wave arrival direction separately for each azimuth without phase fold-back on the basis of received signals of three or more antennas included in a plurality of antennas. The first decomposition unit 472 decomposes the received signals of two or more antennas included in the plurality of antennas into a complex signal for each azimuth. The first selection unit 473 selects, for each azimuth, one from the phase difference of a plurality of complex signals obtained by decomposition by the first decomposition unit 472 and the phase fold-back of the phase difference on the basis of the calculation result of the azimuth calculation unit 471. The antenna interval of the antennas used in decomposition by the first decomposition unit 472 is wider than the antenna interval of the antennas used in calculation by the azimuth calculation unit 471.SELECTED DRAWING: Figure 4

Description

The present invention relates to a signal processing device, a radar device, and a signal processing method.

The radar device irradiates radio waves and receives radio waves (reflected waves) reflected from the target to estimate the direction of arrival of the reflected waves. The method of estimating the arrival direction is a method of calculating the arrival direction (angle) from information on the phase difference and amplitude difference of the received signals obtained by a plurality of receiving antennas that receive the reflected wave.

Japanese Unexamined Patent Publication No. 2006-329671

The receiving antenna interval is very important in calculating the arrival direction (angle), and greatly affects the angle accuracy and phase folding. There is a trade-off between angle accuracy and phase folding. Specifically, if the distance between the receiving antennas is wide, the angle accuracy of the target is improved, but phase folding is likely to occur, whereas if the distance between the receiving antennas is narrow, phase folding is unlikely to occur, but the angle accuracy of the target is accurate. Will get worse.

The incident angle estimation device disclosed in Patent Document 1 aims to solve the problem of phase folding and improve the accuracy of the direction indicating the arrival direction of the radio wave. However, the incident angle estimation device disclosed in Patent Document 1 has a problem that it cannot cope with the case where there are a plurality of directions representing the arrival directions of radio waves.

In view of the above problems, it is an object of the present invention to provide a technique capable of solving the problem of phase folding and improving the accuracy of the direction indicating the arrival direction of radio waves.

The signal processing device according to the present invention is a signal processing device that processes reception signals of a plurality of antennas, and is an orientation representing an arrival direction of radio waves based on reception signals of three or more antennas included in the plurality of antennas. A direction calculation unit that separates each of the directions and calculates without phase folding, a first decomposition unit that decomposes received signals of two or more antennas included in the plurality of antennas into complex signals for each direction, and the above. For each azimuth, the first selection unit selects one from the phase difference of the plurality of complex signals decomposed by the first decomposition unit and the phase folding of the phase difference based on the calculation result of the azimuth calculation unit. The antenna spacing in the antenna used for the disassembly in the first decomposition unit is wider than the antenna spacing in the antenna used for the calculation in the orientation calculation unit (first configuration).

In the signal processing device having the first configuration, the orientation calculation unit calculates the orientation indicating the arrival direction of the radio wave and the phase folding of the orientation based on the reception signals of the three or more antennas included in the plurality of antennas. A separation unit that separates each azimuth, a second decomposition unit that decomposes the received signals of two or more antennas included in the plurality of antennas into complex signals for each azimuth, and the second decomposition unit for each azimuth. A second selection unit for selecting one from the orientation and the phase folding of the orientation based on the decomposition result of the above, and the antenna interval in the antenna used for the separation at the separation unit is the second decomposition. The configuration may be wider than the antenna spacing of the antenna used for the disassembly in the unit and narrower than the antenna spacing of the antenna used for the disassembly in the first disassembly unit (second configuration).

In the signal processing device having the first or second configuration, the antenna spacing of the antennas used for the decomposition in the first decomposition section is the longest antenna spacing of the plurality of antennas (third configuration). You may.

In the signal processing device having any of the first to third configurations, the plurality of antennas are a plurality of virtual antennas generated by a combination of a plurality of transmitting antennas and a plurality of receiving antennas (fourth configuration). ) May be.

The radar device according to the present invention has a configuration (fifth configuration) including the signal processing device having any of the first to third configurations and the plurality of antennas.

The arrival direction estimation method according to the present invention is a signal processing method for processing reception signals of a plurality of antennas, and represents an arrival direction of radio waves based on reception signals of three or more antennas included in the plurality of antennas. An azimuth calculation step of separating azimuths for each azimuth and calculating without phase folding, a decomposition step of decomposing received signals of two or more antennas included in the plurality of antennas into complex signals for each azimuth, and the azimuth. Each includes a selection step of selecting one from the phase difference of the plurality of complex signals decomposed by the decomposition step and the phase folding of the phase difference based on the calculation result of the orientation calculation step. The antenna spacing in the antenna used for the disassembly in the disassembly step is wider than the antenna spacing in the antenna used for the calculation in the orientation calculation step (sixth configuration).

According to the present invention, it is possible to solve the problem of phase folding and improve the accuracy of the direction indicating the arrival direction of the radio wave.

Diagram showing the configuration of the radar device Diagram for explaining the antenna provided in the radar device The figure which shows the combination of the transmitting antenna and the receiving antenna which make up each virtual antenna Functional block diagram showing the first example of the direction calculation unit Flowchart showing the schematic operation of the radar device The figure which shows the relationship between the phase difference and the direction of the received signal for the antenna interval d in the direction calculation by the direction calculation part. The figure which shows the relationship between the phase difference and the direction of the complex signal obtained by the 1st decomposition part. The figure which shows the relationship between the azimuth which converted the phase difference of the complex signal obtained by the 1st decomposition part into the phase difference of antenna interval d. Functional block diagram showing a second example of the directional calculation unit A flowchart showing the processing contents of the direction calculation executed by the direction calculation unit in the second example. The figure which shows the relationship between the phase difference and the direction of the received signal for the antenna interval 2d in the direction separation in a separation part. The figure which shows the relationship between the phase difference and the direction of the complex signal obtained by the 2nd decomposition part The figure which shows the relationship between the phase difference of the received signal obtained by the separation part converted into the phase difference of the antenna interval d, and the orientation.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings.

<1. Radar device configuration>
FIG. 1 is a diagram showing a configuration of a radar device 1 according to an embodiment of the present invention. The radar device 1 can be mounted on a moving body such as a vehicle, a robot, an aircraft, or a ship. In this embodiment, the radar device 1 is mounted on a vehicle such as an automobile. Hereinafter, the vehicle on which the radar device 1 is mounted is referred to as a own vehicle.

The radar device 1 is used to detect targets existing around the own vehicle, such as other vehicles, signs, guardrails, and people. The target detection result is output to the storage device of the own vehicle, the vehicle ECU (Electronic Control Unit) 5 that controls the behavior of the own vehicle, and the like. The target detection result is used for vehicle control such as PCS (Pre-crash Safety System) and AEBS (Advanced Emergency Braking System).

As shown in FIG. 1, the radar device 1 includes a plurality of transmitting units 2, a plurality of receiving units 3, and a signal processing device 4. The radar device 1 further includes a plurality of transmitting antennas 23 and a plurality of receiving antennas 31.

The radar device 1 is a so-called MIMO (Multiple-Input and Multiple-Output) radar device. However, unlike the present embodiment, the radar device 1 may be changed to a configuration including a single transmitting antenna and a plurality of receiving antennas. Further, the radar device 1 is an FCM (Fast Chirp Modulation) type radar device. However, unlike the present embodiment, the radar device 1 may be changed to a radar device other than the FCM system such as the FMCW (Frequency Modulated Continuous Wave) system.

The transmission unit 2 includes a signal generation unit 21 and a transmitter 22. The signal generation unit 21 generates a modulated signal whose voltage changes in a sawtooth pattern and supplies it to the transmitter 22. The transmitter 22 generates a transmission signal, which is a chirp signal, based on the modulation signal generated by the signal generation unit 21, and outputs the transmission signal to the transmission antenna 23.

In this embodiment, the number of transmitting antennas 23 is three. The number of transmission units 3 is also three according to the number of transmission antennas 23. However, the number of transmitting antennas 23 may be other than three. The number of transmission units 3 may be changed according to the number of transmission antennas 23. Further, the number of transmitting antennas 23 and the number of transmitting units 2 do not necessarily have to match. For example, one transmitting unit 2 may be provided for each of the three transmitting antennas 23, and the connection between each transmitting antenna 23 and the transmitting unit 2 may be switched by a switch.

The three transmitting antennas 23 receive transmission signals from separate transmission units 2, convert the transmission signals into transmission wave TW, and output the transmission signals. The transmission signals output from each of the three transmission units 2 are signals (orthogonal signals) orthogonal to each other. Orthogonality means that they do not interfere with each other due to differences in time, phase, frequency, sign, etc., for example.

The receiving unit 3 includes a plurality of receiving antennas 31 and a plurality of individual receiving units 32. One individual receiving unit 32 is connected to each receiving antenna 31. Each receiving antenna 31 receives the reflected wave RW from the target, acquires a received signal, and outputs the received signal to each individual receiving unit 32. In the present embodiment, the receiving unit 3 includes two receiving antennas 31 and two individual receiving units 32. However, the number of receiving antennas 31 may be other than two. Further, the number of individual receiving units 32 may be smaller than the number of receiving antennas 31 by introducing a switch.

Each individual receiving unit 32 processes the received signal obtained by the corresponding receiving antenna 31. The individual receiving unit 32 includes a mixer 33 and an A / D converter 34. The received signal obtained by the receiving antenna 31 is amplified by a low noise amplifier (not shown) and then sent to the mixer 33. A transmission signal from each transmitter 22 of each transmission unit 2 is input to the mixer 33, and each transmission signal and a reception signal are mixed in the mixer 33. As a result, a beat signal having a beat frequency that is the difference between the frequency of each transmission signal and the frequency of the reception signal is generated. The beat signal generated by the mixer 33 is converted into a digital signal by the A / D converter 34 and then output to the signal processing device 4.

The signal processing device 4 executes various processes based on each beat signal captured via each A / D converter 34. The signal processing device 4 includes a microcomputer including a CPU (Central Processing Unit), a memory 41, and the like. The signal processing device 4 stores various data to be calculated in the memory 41 which is a storage device. The memory 41 is, for example, a RAM (Random Access Memory) or the like. The signal processing device 4 includes a transmission control unit 42, a conversion unit 43, and a data processing unit 44 as functions realized by software in a microcomputer. The transmission control unit 42 controls the signal generation unit 21 of each transmission unit 2.

Since the conversion unit 43 receives the reflected waves from a plurality of targets in an overlapping state at the receiving antenna 31, the frequency component based on the reflected waves of each target is generated from the beat signal generated based on the received signal. Is processed to separate. In the present embodiment, the transforming unit 43 separates frequency components by a fast Fourier transform (FFT) process. In the FFT process, reception level and phase information are calculated for each frequency point (sometimes called a frequency bin) set at a predetermined frequency interval. The conversion unit 43 outputs the result of the FFT processing to the data processing unit 44.

Specifically, the conversion unit 43 performs two-dimensional FFT processing on each beat signal output from each A / D conversion unit 34. By performing the first FFT process, a frequency spectrum in which a peak appears in a frequency bin (hereinafter, may be referred to as a distance bin) corresponding to the distance to the target can be obtained. By arranging the frequency spectra obtained by the first FFT process in chronological order and performing the second FFT process, a frequency spectrum in which a peak appears in the frequency bin (hereinafter, may be referred to as a velocity bin) with respect to the Doppler frequency. Is obtained. The transforming unit 43 obtains a two-dimensional power spectrum centered on the distance bin and the velocity bin by the two-dimensional FFT process.

The data processing unit 44 includes a peak extraction unit 45, a distance / relative velocity calculation unit 46, and a direction calculation unit 47.

The peak extraction unit 45 detects the peak from the result of the FFT process or the like in the conversion unit 43. In the present embodiment, the peak extraction unit 45 extracts a peak showing a power value equal to or higher than a predetermined value based on a two-dimensional power spectrum centered on a distance bin and a velocity bin obtained by the two-dimensional FFT process. Further, in the present embodiment, the peak extraction unit 45 classifies the peak extraction results into the results for each virtual antenna. The virtual antenna will be described later.

The distance / relative velocity calculation unit 46 derives the distance and relative velocity from the target based on the combination of the distance bin and the velocity bin specified by the peak extraction unit 45 as the existence of the peak.

The direction calculation unit 47 pays attention to the peaks of the same frequency bin extracted by the peak extraction unit 45 for each virtual antenna, and the direction in which the target exists based on the phase information of those peaks (direction indicating the arrival direction of the radio wave). ) Is estimated. When there are a plurality of peaks having different frequency bins, the direction calculation unit 47 estimates the direction for each peak. For orientation estimation, known methods such as MUSIC (Mutiple Signal Classification) and ESPRIT (Estimation of Signal Parameters via Rotational Invariance Techniques) are used. The details of the processing of the direction calculation unit 47 will be described later.

The target data including the distance to the target, the relative speed of the target, and the direction in which the target exists, which are obtained by the distance / relative speed calculation unit 46 and the direction calculation unit 47, are output to the vehicle ECU 5. ..

<2. Virtual antenna ＞
FIG. 2 is a diagram for explaining an antenna included in the radar device 1.

In the present embodiment, as shown in FIG. 2A, the three transmitting antennas 23 are arranged along the horizontal direction with the same antenna spacing of 2d. That is, the antenna spacing between the adjacent transmitting antenna Tx1 and the transmitting antenna Tx2 and the antenna spacing between the adjacent transmitting antenna Tx2 and the transmitting antenna Tx2 are both 2d. The antenna spacing of adjacent transmitting antennas 23 does not have to be exactly the same among a plurality of sets (two sets for three transmitting antennas 23), and after considering design errors and variations. It suffices if it can be regarded as the same among a plurality of sets.

In the present embodiment, as shown in FIG. 2B, the 32 receiving antennas 31 are arranged along the horizontal direction at an antenna spacing d. The antenna distance between the adjacent receiving antenna Rx1 and the receiving antenna Rx2 does not have to be exactly half of the antenna distance between the two adjacent transmitting antennas 23, and after considering design errors and variations. It suffices if it can be regarded as half of the antenna distance between two adjacent transmitting antennas 23.

The antenna interval d is the same as the half wavelength of the transmitted wave TW and the received wave RW. The antenna interval d does not have to be exactly the same as the half wavelength of the transmitted wave TW and the received wave RW, and is the same as the half wavelength of the transmitted wave TW and the received wave RW in consideration of design errors and variations. It suffices if it can be regarded as the same.

Further, the antenna spacing of the plurality of transmitting antennas 23 and the antenna spacing of the plurality of receiving antennas 31 shown in FIG. 2 are merely examples, and the antenna spacing may be appropriately changed.

The virtual array antenna shown in FIG. 2C is generated by the combination of the three transmitting antennas 23 shown in FIG. 2A and the two receiving antennas 31 shown in FIG. 2B. The virtual array antenna shown in FIG. 2C is composed of virtual antennas VRx1 to VRx6. The virtual antennas VRx1 to VRx6 are arranged along the horizontal direction with the same antenna spacing d. By applying MIMO technology, it is possible to obtain a virtual antenna that is three times the number of receiving antennas by simply increasing the number of transmitting antennas by two.

FIG. 3 is a diagram showing a combination of a transmitting antenna 23 and a receiving antenna 31 constituting each virtual antenna VRx1 to VRx6. As shown in FIG. 3, the virtual antenna VRx1 is generated by combining the transmitting antenna Tx1 and the receiving antenna Rx1. The virtual antenna VRx2 is generated by combining the transmitting antenna Tx1 and the receiving antenna Rx2. The virtual antenna VRx3 is generated by combining the transmitting antenna Tx2 and the receiving antenna Rx1. The virtual antenna VRx4 is generated by combining the transmitting antenna Tx2 and the receiving antenna Rx2. The virtual antenna VRx5 is generated by combining the transmitting antenna Tx3 and the receiving antenna Rx1. The virtual antenna VRx6 is generated by combining the transmitting antenna Tx3 and the receiving antenna Rx2.

That is, the reception signal of the reception antenna Rx1 includes the reception signal of the virtual antenna VRx1 orthogonal to each other, the reception signal of the virtual antenna VRx3, and the reception signal of the virtual antenna VRx5. The reception signal of the reception antenna Rx2 includes a reception signal of the virtual antenna VRx2 orthogonal to each other, a reception signal of the virtual antenna VRx4, and a reception signal of the virtual antenna VRx6. The signal processing device 4 processes the received signals of the plurality of virtual antennas VRx1 to VRx6 generated by the combination of the plurality of transmitting antennas 23 and the plurality of receiving antennas 31.

<3. First example of directional calculation unit>
FIG. 4 is a functional block diagram showing a first example of the direction calculation unit 47. In this example, the directional calculation unit 47 includes a directional calculation unit 471, a first decomposition unit 472, and a first selection unit 473. That is, the signal processing device 4 includes an orientation calculation unit 471, a first decomposition unit 472, and a first selection unit 473.

The direction calculation unit 471 separates the direction indicating the arrival direction of the radio wave for each direction based on the received signals of three or more antennas included in the plurality of antennas, and calculates without phase folding back. In this example, the direction calculation unit 471 separates the direction indicating the arrival direction of the radio wave for each direction based on the received signals of the three virtual antennas VRx1 to VRx3 and calculates without phase folding back. The details of the processing of the direction calculation unit 471 will be described later.

The first decomposition unit 472 decomposes the reception signals of two or more antennas included in the plurality of antennas into a complex signal for each direction calculated by the direction calculation unit 471. In this example, the first decomposition unit 472 decomposes the received signals of the virtual antennas VRx1 and VRx6 into complex signals for each direction calculated by the direction calculation unit 471. The complex signal includes phase information and amplitude information. Details of the processing of the first decomposition unit 472 will be described later.

The antenna spacing of the antenna used for the disassembly by the first decomposition unit 472 is wider than the antenna spacing of the antenna used for the calculation by the direction calculation unit 471. In this example, the antenna spacing in the antenna used for disassembly in the first disassembly section 472 is d, whereas the antenna spacing in the antenna used for disassembly in the first disassembly section 472 is 5d.

In this example, the antenna spacing in the antenna used for the disassembly in the first disassembly unit 472 is the longest antenna spacing 5d of the virtual antennas VRx1 to VRx6. By adopting the longest antenna spacing 5d of the virtual antennas VRx1 to VRx6 as the antenna spacing in the antenna used for the disassembly in the first decomposition section 472, the accuracy of the direction indicating the arrival direction of the radio wave can be improved to the maximum. .. However, the antenna spacing in the antenna used for the disassembly by the first disassembly unit 472 may be an antenna spacing other than the longest antenna spacing 5d of the virtual antennas VRx1 to VRx6, for example, 4d.

The first selection unit 473 determines the phase difference of a plurality of complex signals decomposed by the first decomposition unit 472 and the phase difference thereof for each direction calculated by the direction calculation unit 471 based on the calculation result of the direction calculation unit 471. Select one from the phase wraps. Details of the processing of the first selection unit 473 will be described later. The direction calculation unit 47 estimates that the direction obtained by converting the selection result of the first selection unit 473 is the direction in which the target exists (the direction representing the arrival direction of the radio wave).

The direction calculation unit 47 sets the selection criterion of the first selection unit 473 as the "calculation result of the direction calculation unit 471". As a result, the directional calculation unit 47 can solve the problem of phase folding back.

Further, the directional calculation unit 47 has a first selection unit 473 under the condition that the antenna spacing in the antenna used for the decomposition in the first decomposition unit 472 is wider than the antenna spacing in the antenna used for the calculation in the directional calculation unit 471. The selection target of is "the phase difference of a plurality of complex signals decomposed by the first decomposition unit 472 and the phase folding back of the phase difference". As a result, the direction calculation unit 47 can improve the accuracy of the direction indicating the arrival direction of the radio wave as compared with the case where the calculation result of the direction calculation unit 471 is used as it is as the direction indicating the arrival direction of the radio wave.

That is, the signal processing device 4 can both solve the problem of phase folding and improve the accuracy of the direction indicating the arrival direction of the radio wave.

FIG. 5 is a flowchart showing a schematic operation of the radar device 1. FIG. 5 mainly shows the processing by the direction calculation unit 47. That is, in FIG. 5, the process of obtaining the distance to the target and the relative speed is omitted. The radar device 1 periodically repeats the process shown in FIG. 5 at regular time intervals.

First, the transmitting antenna 23 outputs the transmitted wave TW (step S1). Next, the receiving antenna 31 receives the reflected wave RW reflected by the target and acquires the received signal (step S2). Next, the signal processing device 4 acquires a predetermined number of beat signals (step S3). Next, the FFT process is performed on the beat signal acquired by the conversion unit 43 (step S4).

Next, the peak extraction unit 45 performs peak extraction based on the result of the FFT process (step S5). The peak extraction unit 45 classifies the peak extraction results into the results for each of the virtual antennas VRx1 to VRx6.

Next, the direction calculation unit 471 separates the direction indicating the arrival direction of the radio wave for each direction based on the received signals of the virtual antennas VRx1 to VRx3, and calculates without phase folding back (step S6). The orientation calculation unit 471 calculates the correlation matrix Rxx represented by the following equation (1).
Rxx = E [X (t) X ^H (t)] ... (1)
here,
X (t) = [x ₁ (t), x ₂ (t), x ₃ (t)] ^T ... (2)
Is.

Note that X (t) is a received signal vector of the virtual antennas VRx1 to VRx3 at time t. E [・] indicates the expected value, H indicates the complex conjugate transpose, and T indicates the transpose matrix. x ₁ (t) is a reception signal of the virtual antenna VRx ₁ , x ₂ (t) is a reception signal of the virtual antenna VR x ₂ , and x ₃ (t) is a reception signal of the virtual antenna VR x ₃ .

The orientation calculation unit 471 calculates the orientation by using a known MUSIC, ESPRIT, or the like using the correlation matrix Rxx. Since the correlation matrix Rxx is generated from the received signals of the three virtual antennas VRx1 to VRx3, the direction calculation unit 471 obtains a maximum of two directions. Since the antenna spacing d of the three virtual antennas VRx1 to VRx3 is the same as the half wavelength of the transmission wave TW and the reception wave RW, phase folding does not occur in the direction calculation by the direction calculation unit 471.

Hereinafter, a case where the direction calculation unit 471 calculates the direction D1 and the direction D2 will be described. FIG. 6 is a diagram showing the relationship between the phase difference of the received signal for the antenna interval d in the directional calculation by the directional calculation unit 471 and the directional.

Returning to FIG. 5, when the direction is calculated by the direction calculation unit 471, the first decomposition unit 472 transmits the received signals of the virtual antennas VRx1 and VRx6 for each of the directions D1 and D2 based on the following equation (3). It is decomposed into a complex signal (step S7).
X (t) = AS (t) ... (3)
here,
A = [a (θ ₁ ), a (θ ₂ )] ... (4)
S (t) = [s ₁ (t), s ₂ (t)] ^T ... (5)
Is.

Note that a (θ ₁ ) is a mode vector of the direction D1. a (θ ₂ ) is a mode vector of the direction D2. θ ₁ is an angle representing the direction D1. θ ₂ is an angle representing the direction D2. The angle representing the azimuth becomes 0 [deg] when the target is located directly in front of the radar device 1, and becomes larger than 0 [deg] as the target shifts from the front to the right when viewed from the radar device 1. The mark becomes smaller than 0 [deg] as it shifts from the front to the left when viewed from the radar device 1. S (t) is a phase amplitude vector of radio waves. s ₁ (t) is a complex signal (phase amplitude signal) having the direction D1. s ₂ (t) is a complex signal (phase amplitude signal) of the direction D2.

Since the direction D1 and the direction D2 are calculated by the direction calculation unit 471, the matrix A in the equation (3) is known. The received signal vector X (t) in the equation (3) is also known. Therefore, the first decomposition unit 472 can obtain the phase amplitude vector S (t) based on the equation (3).

A complex signal of the azimuth D1 in virtual antennas VRX1 (phase amplitude _{signal) s 1VRx1 (t),} when obtaining a complex signal in the azimuth D2 in the virtual antennas VRX1 (phase amplitude _{signal) s 2VRx1 (t)} is first decomposed The unit 472 sets the reference antenna of the mode vectors a (θ ₁ ) and a (θ ₂ ) to the virtual antenna VRx1. Specifically, the first decomposition unit 472 substitutes the following values for the received signal vector X (t) and the mode vector a (θ _k ).
X (t) = [x _VRx1 (t), x _VRx6 (t)] ^T ... (6)
a (θ ₁ ) = [1, exp {-jΛ5dsin (θ ₁ )}] ^T ... (7)
a (θ ₂ ) = [1, exp {-jΛ5dsin (θ ₂ )}] ^T ... (8)
Λ = 2π / λ ・ ・ ・ (9)

Note that x _VRx1 (t) is a received signal of the virtual antenna VRx1 at time t. x _VRx6 (t) is a received signal at time t of the virtual antenna VRx6. λ is the wavelength of the transmitted wave TW and the received wave RW.

By the assignment, the complex signal of the azimuth D1 in virtual antennas VRX1 (phase amplitude _{signal) s 1VRx1 (t),} and is obtained complex signal of the azimuth D2 in the virtual antennas VRX1 (phase amplitude _{signal) s 2VRx1 (t).}

Further, the complex signal of the azimuth D1 in virtual antennas VRx6 (phase amplitude _{signal) s 1VRx6 (t),} when obtaining a complex signal in the azimuth D2 in the virtual antennas VRx6 (phase amplitude _{signal) s 2VRx6 (t)} is the 1 The decomposition unit 472 sets the reference antenna of the mode vectors a (θ ₁ ) and a (θ ₂ ) to the virtual antenna VRx6. Specifically, the first decomposition unit 472 substitutes the value of the above equation (6) into the received signal vector X (t), and substitutes the following value into the mode vector a (θ _k ).
a (θ ₁ ) = [exp {jΛ5dsin (θ ₁ )}, 1] ^T ... (10)
a (θ ₂ ) = [exp {jΛ5dsin (θ ₂ )}, 1] ^T ... (11)

By the assignment, the complex signal of the azimuth D1 in virtual antennas VRx6 (phase amplitude _{signal) s 1VRx6 (t),} and is obtained complex signal of the azimuth D2 in the virtual antennas VRx6 (phase amplitude _{signal) s 2VRx6 (t).}

FIG. 7 is a diagram showing the relationship between the phase difference and the orientation of the complex signal obtained by the first decomposition unit 472. In FIG. 7, the phase difference between the complex signal s _1VRx1 (t) of the direction D1 in the virtual antenna VRx1 and the complex signal s _1VRx6 (t) of the direction D1 in the virtual antenna VRx6 and the phase folding of the phase difference are shown by black circles. Further, in FIG. 7, the phase difference between the complex signal s _2VRx1 (t) of the direction D2 in the virtual antenna VRx1 and the complex signal s _2VRx6 (t) of the direction D2 in the virtual antenna VRx6 and the phase folding of the phase difference are shown by a black square. Shown. Since the antenna spacing between the virtual antenna VRx1 and the virtual antenna VRx6 is 5d, the phase difference in FIG. 7 is the phase difference corresponding to the antenna spacing of 5d.

Returning to FIG. 5, when the complex signal for each of the directions D1 and D2 is obtained by the first decomposition unit 472, the first selection unit 473 sets the first selection unit 473 for each of the directions D1 and D2 based on the calculation result of the direction calculation unit 471. 1 Select one from the phase difference of a plurality of complex signals decomposed by the decomposition unit 472 and the phase folding of the phase difference (step S8).

The first selection unit 473 converts the phase difference of the complex signal obtained by the first decomposition unit 472 into a phase difference equal to the antenna interval d in order to enable comparison with the calculation result of the direction calculation unit 471. FIG. 8 is a diagram showing the relationship between the direction and the phase difference of the complex signal obtained by the first decomposition unit 472 converted into the phase difference of the antenna interval d.

The first selection unit 473 compares the phase difference in FIG. 6 with the phase difference shown in FIG. 8, and selects the one whose phase difference is closest to the phase difference of the black circle shown in FIG. 6 from the black circles shown in FIG. Then, the direction D1'of the selected black circle is output. The direction D1'is the corresponding direction of the direction D1 and has a smaller error than the direction D1.

Further, the first selection unit 473 compares the phase difference in FIG. 6 with the phase difference shown in FIG. 8, and among the black squares shown in FIG. 8, the phase difference is the largest in the phase difference of the black square shown in FIG. Select the closest one and output the direction D2'of the selected black square. The direction D2'is the corresponding direction of the direction D2 and has a smaller error than the direction D2.

Returning to FIG. 5, when the selection by the first selection unit 473 is completed, the direction calculation unit 47 sets the directions D1'and D2' output from the first selection unit 473 to the directions in which the target exists (the arrival of radio waves). It is estimated that the direction is the direction), the estimation result is output (step S9), and the flow is terminated.

As is clear from FIGS. 6 and 8, the wider the angle of orientation (the larger the absolute value of the orientation), the smaller the rate of change of the phase difference with respect to the rate of change of the orientation, so that the error of the phase difference gives the error of the orientation. The impact will be greater. Therefore, the signal processing device 4 can greatly improve the accuracy of the direction in the wide-angle range of the direction.

When the directional calculation unit 471 uses a set of antennas in which the antenna interval d is wider than half the wavelength of the transmission wave TW and the reception wave RW, phase folding occurs. For example, the direction is calculated by combining VRx1, VRx3, and VRx5. At this time, there is a possibility that the direction D1 is not the direction calculated by the direction calculation unit 47, but another direction due to phase folding. The same applies to the direction D2. In this case, it is necessary to eliminate the phase fold and determine the direction before calculating the mode vector in the equations (7) and (8). Various known phase wrapping determination methods may be used to eliminate the phase wrapping. After eliminating the phase wrapping and determining the directions D1 and D2, it is preferable to substitute θ1 and θ2 into the equations (7) and (8) to calculate the mode vector.

<4. Second example of directional calculation unit>
FIG. 9 is a functional block diagram showing a second example of the direction calculation unit 47. In this example as well, the directional calculation unit 47 includes a directional calculation unit 471, a first decomposition unit 472, and a first selection unit 473, as in the first example. That is, the signal processing device 4 includes an orientation calculation unit 471, a first decomposition unit 472, and a first selection unit 473.

The orientation calculation unit 471 in this example differs from the orientation calculation unit 471 in the first example in that it includes a separation unit 471a, a second decomposition unit 471b, and a second selection unit 471c.

The separation unit 471a separates the direction representing the arrival direction of the radio wave and the phase folding of the direction for each direction based on the received signals of the three or more antennas included in the plurality of antennas. In this example, the separation unit 471a separates the direction indicating the arrival direction of the radio wave and the phase folding of the direction for each direction based on the received signals of the three virtual antennas VRx1, VRx3, and VRx5. Details of the processing of the separation unit 471a will be described later.

The second decomposition unit 471b decomposes the reception signals of two or more antennas included in the plurality of antennas into complex signals for each direction separated by the separation unit 471a. In this example, the second decomposition unit 471b decomposes the received signals of the virtual antennas VRx1 and VRx2 into complex signals for each direction separated by the separation unit 471a. Details of the processing of the second decomposition unit 471b will be described later.

In this example, the antenna spacing in the antenna used for separation in the separation section 471a is wider than the antenna spacing in the antenna used for decomposition in the second decomposition section 471b, and the antenna used for decomposition in the first decomposition section 472. Narrower than the antenna spacing in. In this example, the antenna spacing in the antenna used for separation in the separation section 471a is 2d, whereas the antenna spacing in the antenna used for decomposition in the second decomposition section 471b is d. Further, in this example, the antenna spacing in the antenna used for separation in the separation unit 471a is 2d, whereas the antenna spacing in the antenna used for decomposition in the first decomposition unit 472 is 5d.

The second selection unit 471c selects one from the orientations separated by the separation unit 471a and the phase folding of the orientations based on the decomposition result of the second decomposition unit 471b for each orientation separated by the separation unit 471a. To do. Details of the processing of the second selection unit 471c will be described later.

Even when the directional calculation unit 47 in this example is used, the flowchart showing the schematic operation of the radar device 1 is shown in FIG. 5, as in the case where the directional calculation unit 47 in the first example is used. However, when the direction calculation unit 47 in this example is used, the processing content of the direction calculation (step S6 in FIG. 5) is different from the case where the direction calculation unit 47 in the first example is used.

FIG. 10 is a flowchart showing the processing contents of the direction calculation executed by the direction calculation unit 47 in this example.

First, the separation unit 471a separates the direction indicating the arrival direction of the radio wave and the phase folding of the direction for each direction based on the received signals of the virtual antennas VRx1, VRx3, and VRx5 (step S61). The separation unit 471a calculates the correlation matrix Rxx'expressed by the following equation (12).
Rxx'= E [X (t) X ^H (t)] ... (12)
here,
X (t) = [x ₁ (t), x ₃ (t), x ₅ (t)] ^T ... (13)
Is.

x ₁ (t) is a reception signal of the virtual antenna VRx ₁ , x ₃ (t) is a reception signal of the virtual antenna VR x ₃ , and x ₅ (t) is a reception signal of the virtual antenna VR x ₅ .

The separation unit 471a separates the orientation by using a known MUSIC, ESPRIT, or the like using the correlation matrix Rxx'. Since the correlation matrix Rxx'is generated from the received signals of the three virtual antennas VRx1, VRx3, and VRx5, the separation unit 471a obtains a maximum of two directions. Since the antenna spacing 2d of the three virtual antennas VRx1, VRx3, and VRx5 is longer than half the wavelengths of the transmission wave TW and the reception wave RW, phase folding occurs in the directions separated by the separation unit 471a.

Hereinafter, a case where the separation unit 471a separates the arrival direction of the radio wave into the direction D1 and the direction D2 will be described. As described above, since the phase folding occurs in the second example, unlike the case of the first example, the direction D1 is not fixed as one direction. The same applies to the direction D2. FIG. 11 is a diagram showing the relationship between the phase difference and the orientation of the received signals for the antenna interval of 2d in the orientation separation at the separation unit 471a. As shown in the figure, there are a plurality of directions corresponding to the same phase difference, and the separation unit 471a calculates the direction of any one of the plurality of directions corresponding to the phase difference.

Returning to FIG. 10, when the directions are separated by the separation unit 471a, the second decomposition unit 471b transmits the received signals of the virtual antennas VRx1 and VRx2 to the complex for each of the directions D1 and D2 based on the following equation (14). It is decomposed into signals (step S62). The following equations (14) to (16) are the same as the above-mentioned equations (3) to (5).
X (t) = AS (t) ... (14)
here,
A = [a (θ ₁ ), a (θ ₂ )] ... (15)
S (t) = [s ₁ (t), s ₂ (t)] ^T ... (16)
Is.

Note that a (θ ₁ ) is a mode vector of the direction D1. a (θ ₂ ) is a mode vector of the direction D2. θ ₁ is an angle representing the direction D1. θ ₂ is an angle representing the direction D2. The angle representing the azimuth becomes 0 [deg] when the target is located directly in front of the radar device 1, and becomes larger than 0 [deg] as the target shifts from the front to the right when viewed from the radar device 1. The mark becomes smaller than 0 [deg] as it shifts from the front to the left when viewed from the radar device 1. S (t) is a phase amplitude vector of radio waves. s ₁ (t) is a complex signal (phase amplitude signal) having the direction D1. s ₂ (t) is a complex signal (phase amplitude signal) of the direction D2.

Since the direction D1 and the direction D2 are obtained by the separation unit 471a, the matrix A in the equation (14) is known. The received signal vector X (t) in the equation (14) is also known. Therefore, the second decomposition unit 471b can obtain the phase amplitude vector S (t) based on the equation (14).

A complex signal of the azimuth D1 in virtual antennas VRX1 (phase amplitude _{signal) s 1VRx1 (t),} when obtaining a complex signal in the azimuth D2 in the virtual antennas VRX1 (phase amplitude _{signal) s 2VRx1 (t)} is first decomposed The unit 472 sets the reference antenna of the mode vectors a (θ ₁ ) and a (θ ₂ ) to the virtual antenna VRx1. Specifically, the second decomposition unit 471b substitutes the following values for the received signal vector X (t) and the mode vector a (θ _k ).
X (t) = [x _VRx1 (t), x _VRx3 (t)] ^T ... (17)
a (θ ₁ ) = [1, exp {-2jΛdsin (θ ₁ )}] ^T ... (18)
a (θ ₂ ) = [1, exp {-2jΛdsin (θ ₂ )}] ^T ... (19)
Λ = 2π / λ ・ ・ ・ (20)

Note that x _VRx1 (t) is a received signal of the virtual antenna VRx1 at time t. x _VRx3 (t) is a received signal of the virtual antenna VRx3 at time t. λ is the wavelength of the transmitted wave TW and the received wave RW. In the first example described above, the phase wrapping is eliminated and the orientation is fixed to one before calculating the mode vector, but in the second example, this is not necessary. Therefore, when the signal vector X (t) and the mode vector a (θk) are generated, the virtual antenna is selected according to the antenna spacing used in the separation unit 471a. For example, in the above case, the virtual antenna VRx3 is selected for the virtual antenna VRx1 for which the complex signal is to be obtained according to the antenna spacing 2d used in the separation unit 471a.

At this time, the received signal vector X (t) generates the received signal of the selected virtual antenna as an element. Further, in the mode vector a (θ), the element corresponding to the reference antenna (virtual antenna VRx1 in the above) is set to 1, and the other elements are substituted with the ideal phase difference at the position of another corresponding virtual antenna. Generate.

By the assignment, the complex signal of the azimuth D1 in virtual antennas VRX1 (phase amplitude _{signal) s 1VRx1 (t),} and is obtained complex signal of the azimuth D2 in the virtual antennas VRX1 (phase amplitude _{signal) s 2VRx1 (t).}

Further, the complex signal of the azimuth D1 in virtual antennas VRX2 (phase amplitude _{signal) s 1VRx2 (t),} when obtaining a complex signal in the azimuth D2 in the virtual antennas VRX2 (phase amplitude _{signal) s 2VRx2 (t)} is the 2 The decomposition unit 471b sets the reference antenna of the mode vectors a (θ ₁ ) and a (θ ₂ ) to the virtual antenna VRx2. Specifically, the second decomposition unit 471b substitutes the following values for the received signal vector X (t) and the mode vector a (θ _k ). As described above, for the virtual antenna VRx2, the virtual antenna VRx4 having an antenna interval of 2d is selected.
X (t) = [x _VRx2 (t), x _VRx4 (t)] ^T ... (21)
a (θ ₁ ) = [1, exp {-2jΛdsin (θ ₁ )}] ^T ... (22)
a (θ ₂ ) = [1, exp {-2jΛdsin (θ ₂ )}] ^T ... (23)

By the assignment, the complex signal of the azimuth D1 in virtual antennas VRX2 (phase amplitude _{signal) s 1VRx2 (t),} and is obtained complex signal of the azimuth D2 in the virtual antennas VRX2 (phase amplitude _{signal) s 2VRx2 (t).}

FIG. 12 is a diagram showing the relationship between the phase difference and the orientation of the complex signal obtained by the second decomposition unit 471b. In FIG. 12, the phase difference between the complex signal s _1VRx1 (t) of the direction D1 in the virtual antenna VRx1 and the complex signal s _1VRx2 (t) of the direction D1 in the virtual antenna VRx2 and the phase folding of the phase difference are shown by black circles. Further, in FIG. 12, the phase difference between the complex signal s _2VRx1 (t) of the direction D2 in the virtual antenna VRx1 and the complex signal s _2VRx2 (t) of the direction D2 in the virtual antenna VRx2 and the phase folding of the phase difference are shown by a black square. Shown. Since the antenna distance between the virtual antenna VRx1 and the virtual antenna VRx2 is d, the phase difference in FIG. 12 is the phase difference corresponding to the antenna distance d.

Returning to FIG. 10, when the complex signal for each of the directions D1 and D2 is obtained by the second decomposition unit 471b, the second selection unit 471c is based on the decomposition result of the second decomposition unit 471b for each of the directions D1 and D2. One is selected from the orientations separated by the separation unit 471a and the phase folding of the orientations (step S63).

The second selection unit 471c converts the phase difference of the received signal obtained by the separation unit 471a into a phase difference equal to the antenna interval d in order to enable comparison with the decomposition result of the second decomposition unit 471b. FIG. 13 is a diagram showing the relationship between the orientation and the phase difference of the received signal obtained by the separation unit 471a converted into the phase difference of the antenna interval d.

The second selection unit 471c compares the phase difference in FIG. 11 with the phase difference shown in FIG. 13, and selects the one whose phase difference is closest to the phase difference of the black circle shown in FIG. 12 from the black circles shown in FIG. Then, the direction D1 of the selected black circle is output.

Further, the second selection unit 471c compares the phase difference in FIG. 11 with the phase difference shown in FIG. 13, and among the black squares shown in FIG. 13, the phase difference is the largest in the phase difference of the black square shown in FIG. The closest one is selected, and the direction D2 of the selected black square is output.

Returning to FIG. 10, when the selection by the second selection unit 471c is completed, the direction calculation unit 471 outputs the directions D1 and D2 output from the second selection unit 471c as the direction calculation result (step S64). End the flow.

When the directional calculation unit 47 in this example is used, the accuracy of the directional calculation calculated in step S6 in FIG. 5 is higher than that when the directional calculation unit 47 in the first example is used. Therefore, step S8 in FIG. It is possible to reduce the possibility of making an error in the selection in.

上記の式を用いることで、算出精度を向上することができる。 In equations (17) to (19), the complex signal was calculated using two virtual antennas, but the following values may be substituted using the three virtual antennas for calculation.

By using the above formula, the calculation accuracy can be improved.

上記の式を用いることで、算出精度を向上することができる。また、上記では３つとしたが、仮想アンテナの構成に応じ、３つ以上の仮想アンテナを用いて複素信号を算出してもよい。 Similarly, equations (21) to (23) may be calculated by substituting values as follows.

By using the above formula, the calculation accuracy can be improved. Further, although the number is three in the above, the complex signal may be calculated by using three or more virtual antennas depending on the configuration of the virtual antenna.

<5. Notes>
The configurations of the embodiments and examples in the present specification are merely examples of the present invention. The configurations of the embodiments and modifications may be appropriately changed without exceeding the technical idea of the present invention. In addition, a plurality of embodiments and modifications may be combined and implemented to the extent possible.

Although the in-vehicle radar device has been described above, the present invention may be applied to an infrastructure radar device, a ship surveillance radar device, an aircraft surveillance radar device, etc. installed on a road or the like.

All or part of the functions described above that are realized by software by executing the program may be realized by an electric hardware circuit. In addition, all or part of the functions described as being realized by the hardware circuit may be realized by software. Further, the function described as one block may be realized by the collaboration between software and hardware. In addition, each functional block is a conceptual component. The function executed by each functional block may be distributed to a plurality of functional blocks, or the functions of the plurality of functional blocks may be combined into one functional block.

1 Radar device 4 Signal processing device 23 Transmit antenna 31 Receive antenna 471 Direction calculation unit 471a Separation unit 471b Second decomposition unit 471c Second selection unit 472 First decomposition unit 473 First selection unit VRx1 to VRx6 Virtual antenna

Claims (6)

A signal processing device that processes the received signals of multiple antennas.
Based on the received signals of three or more antennas included in the plurality of antennas, a direction calculation unit that separates the directions representing the arrival directions of radio waves for each direction and calculates without phase folding back.
A first decomposition unit that decomposes the reception signals of two or more antennas included in the plurality of antennas into complex signals for each direction, and
For each direction, the first selection is to select one from the phase difference of the plurality of complex signals decomposed by the first decomposition unit and the phase folding of the phase difference based on the calculation result of the direction calculation unit. Department and
With
A signal processing device in which the antenna spacing in the antenna used for the decomposition in the first decomposition section is wider than the antenna spacing in the antenna used for the calculation in the direction calculation section. The direction calculation unit
Based on the received signals of three or more antennas included in the plurality of antennas, a separation unit that separates the direction indicating the arrival direction of the radio wave and the phase folding of the direction for each direction,
A second decomposition unit that decomposes the reception signals of two or more antennas included in the plurality of antennas into complex signals for each direction, and
For each of the directions, a second selection unit that selects one from the orientation and the phase folding of the orientation based on the decomposition result of the second decomposition unit, and
With
The antenna spacing in the antenna used for separation in the separation section is wider than the antenna spacing in the antenna used for decomposition in the second decomposition section, and the antenna spacing in the antenna used for decomposition in the first decomposition section. The signal processing apparatus according to claim 1, which is also narrow. The signal processing device according to claim 1 or 2, wherein the antenna spacing in the antenna used for the disassembly in the first decomposition section is the longest antenna spacing of the plurality of antennas. The signal processing device according to any one of claims 1 to 3, wherein the plurality of antennas are a plurality of virtual antennas generated by a combination of a plurality of transmitting antennas and a plurality of receiving antennas. The signal processing device according to any one of claims 1 to 4.
With the plurality of antennas
A radar device equipped with. It is a signal processing method that processes the received signals of multiple antennas.
Based on the received signals of three or more antennas included in the plurality of antennas, a direction calculation step of separating the directions representing the arrival directions of radio waves for each direction and calculating without phase folding back.
A decomposition step of decomposing the received signals of two or more antennas included in the plurality of antennas into complex signals for each direction, and
For each of the directions, a selection step of selecting one from the phase difference of the plurality of complex signals decomposed by the decomposition step and the phase folding of the phase difference based on the calculation result of the direction calculation step.
With
A signal processing method in which the antenna spacing in the antenna used for disassembly in the disassembly step is wider than the antenna spacing in the antenna used for the calculation in the direction calculation step.

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