Radar device and detection method

Abstract

A radar device and a detection method are provided that can suppress a decrease in the accuracy of detecting distance and speed due to radio wave interference. In a radar device using an FMCW (Frequency Modulated Continuous Wave) system that acquires distance information and velocity information based on a composite signal of a transmitted signal and a received signal, the transmitted signal is a plurality of chirp signals Ch that are linearly frequency modulated within a predetermined frequency range. i is included in one frame period. Multiple chirp signals Ch i The arrangement interval τ along the time axis i is defined by a non-uniform array that can generate a uniform array that is evenly spaced in the time axis direction by applying a predetermined extension process.

Description

[Technical Field]

[0001] The present invention relates to a radar device and a detection method. [Background technology]

[0002] In recent years, a technology has become known in which an FMCW (Frequency Modulated Continuous Wave) radar is installed in a vehicle to detect surrounding obstacles. As the number of vehicles equipped with such FMCW radar increases, concerns have arisen that detection accuracy may be reduced due to radio interference. A technology has been disclosed that suppresses a decrease in reliability of distance measurement caused by interference or external noise by randomly switching the sweep pattern of a chirp signal (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-232054 Summary of the Invention [Problem to be solved by the invention]

[0004] Generally, in FMCW radar, velocity information is obtained by acquiring the phase change of a chirp signal transmitted multiple times at regular intervals. In the above conventional technology, the sweep pattern of the chirp signal is randomly switched, making it difficult to apply this technology to a vehicle radar device that has a relative velocity between the radar and the target.

[0005] The present disclosure has been made in view of the above, and aims to provide a radar device and a detection method that can suppress a decrease in the accuracy of distance and speed detection caused by radio wave interference. [Means for solving the problem]

[0006] A radar device according to one aspect of the present disclosure is an FMCW (Frequency Modulated Continuous Wave) radar device, comprising: a transceiver unit that generates a composite signal of a transmission signal and a reception signal; a signal processing unit that acquires distance information and velocity information based on the composite signal; and a control unit that controls the transceiver unit and the signal processing unit, wherein the transmission signal includes a plurality of chirp signals that are linearly frequency-modulated within a predetermined frequency range within one frame period, and the arrangement intervals of the plurality of chirp signals in the time axis direction are defined by an unequally spaced array arrangement that can generate an equally spaced array arrangement in which signals are arranged at equal intervals in the time axis direction by applying a predetermined extension process.

[0007] In this configuration, the frequency of interference with other radar devices is reduced by arranging the chirp signals contained in one frame period at uneven intervals along the time axis, thereby suppressing the deterioration of detection accuracy due to radio wave interference.

[0008] Furthermore, by applying the extension process, a signal is obtained in which the frequency bin elements are arranged at equal intervals along the time axis, which makes it possible to perform velocity FFT processing and obtain distance information and velocity information.

[0009] A detection method according to one aspect of the present disclosure is a detection method for a radar device using an FMCW (Frequency Modulated Continuous Wave) system that acquires distance information and velocity information based on a composite signal of a transmitted signal and a received signal, wherein the transmitted signal includes, in one frame period, a plurality of chirp signals that are linearly frequency-modulated within a predetermined frequency range, and the arrangement intervals of the plurality of chirp signals in the time axis direction are defined by an unequally spaced array arrangement that can generate an equally spaced array arrangement in which signals are arranged at equal intervals in the time axis direction by applying a predetermined extension process.

[0010] In this configuration, the frequency of interference with other radar devices is reduced by arranging the chirp signals contained in one frame period at uneven intervals along the time axis, thereby suppressing the deterioration of detection accuracy due to radio wave interference.

[0011] Furthermore, by applying the extension process, a signal is obtained in which the frequency bin elements are arranged at equal intervals along the time axis, which makes it possible to perform velocity FFT processing and obtain distance information and velocity information. [Effects of the Invention]

[0012] According to the present disclosure, it is possible to realize a radar device and a detection method that can suppress a decrease in the accuracy of detecting distance and speed due to radio wave interference. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a block diagram showing a schematic configuration of a radar device according to an embodiment. [Figure 2] FIG. 2 is a conceptual diagram illustrating an example of a transmission signal of the radar device according to the embodiment. [Figure 3] FIG. 3 is a flowchart illustrating an example of an object detection process in the radar device according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, a radar device and a detection method according to an embodiment will be described in detail with reference to the drawings. However, the present disclosure is not limited to the embodiment.

[0015] 1 is a block diagram showing a schematic configuration of a radar device according to an embodiment. In the present disclosure, the radar device 1 is an on-board millimeter-wave radar employing an FMCW (Frequency Modulated Continuous Wave) system that is mounted on a moving body such as an automobile and detects detection targets (hereinafter simply referred to as "targets") such as obstacles and pedestrians around the vehicle. Since FMCW radars are well known, detailed description thereof may be omitted.

[0016] In the present disclosure, a radar device 1 includes a transmitter / receiver 2, a signal processor 3, and a controller 4.

[0017] The transmitter / receiver 2 transmits and receives radio waves in the millimeter wave band or microwave band, generates a composite signal (hereinafter also referred to as an "IF signal") of a transmission signal Tx and a reflection signal Rx, and outputs the composite signal to the signal processor 3. Fig. 2 is a conceptual diagram showing an example of a transmission signal of the radar device according to the embodiment.

[0018] In FIG. 2, the horizontal axis indicates the time axis direction, and the vertical axis indicates the frequency axis direction.

[0019] In the present disclosure, the transceiver 2 generates a chirp signal that is linearly frequency modulated from frequency f1 to frequency f2 as shown in Fig. 2. The transmission signal Tx is a plurality of chirp signals Ch within one frame period. i (i=1, 2, . . . , I, where I is the total number of chirp signals included in one frame period). The control unit 4 controls each chirp signal Ch i The slope of a i and chirp period τ' i The value multiplied by is the chirp signal Ch i The transmitter / receiver 2 is controlled so that the bandwidth becomes B.

[0020] The signal processing unit 3 acquires distance information and velocity information of the target object based on the IF signal generated by the signal processing unit 3. More specifically, the signal processing unit 3 performs AD conversion on the IF signal to generate a time domain signal s defined by coordinates on a complex plane. i(t) (t=0, 1, . . . , M-1, where M is the number of sampling points). i The sampling rate in the signal processing unit 3 is controlled so that the number of sampling points M for each signal is the same.

[0021] In this disclosure, each chirp signal Ch included in one frame period i The arrangement interval τ along the time axis i is defined as a non-uniformly spaced array (hereinafter also referred to as a "sparse array") that can generate a uniformly spaced array arranged at equal intervals in the time axis direction by applying a predetermined extension process, for example.

[0022] Each chirp signal Ch included in one frame period i The arrangement interval τ along the time axis i (Each chirp signal Ch i The spacing τ of the center frequencies of the chirp signals Chi in the time axis direction is, for example, defined by Minimum Redundancy Arrays (MRAs). i The sparse array arrangement defining the above is not limited to MRAs, but may be defined by, for example, MHAs (Minimum Hole Arrays), Co-Prime Arrays, Nested Arrays, etc.

[0023] The signal processor 3 outputs a chirp signal Ch i Time domain signal per s i Range-FFT (Fast Fourier Transform) processing (hereinafter also referred to as "distance FFT processing") is performed on (t) to obtain distance Bin(S i (f)=(x1, ,x M ), x m (m=1, ,M) are frequency bin elements). Then, the generated distance bins are arranged in the time axis direction, and by applying a method using, for example, KR (Khatri-Rao) product extension processing, each frequency bin element x is arranged at equal intervals in the time axis direction. mThis allows for Doppler-FFT processing (hereinafter also referred to as "velocity FFT processing") to be performed, and a Doppler heat map can be obtained that defines the distance and velocity information of the target object in coordinates on a two-dimensional plane in the distance and velocity directions.

[0024] For example, when multiple vehicles equipped with FMCW radar devices are present within each other's obstacle detection range, radio wave interference may reduce the obstacle detection accuracy of each radar device. Specifically, if the chirp signal modulation rates (tilts of the chirp signals) and chirp directions of the radar devices are different and the chirps cross each other on the time-frequency plane, the noise floor of the signal after distance FFT processing may rise. Alternatively, if the chirp signal modulation rates of the radar devices are the same, there is a possibility that non-existent objects (hereinafter also referred to as "ghosts") may be erroneously detected.

[0025] In the present disclosure, as described above, each chirp signal Ch included in one frame period i The arrangement interval τ along the time axis i By arranging the signals in a sparse array with uneven spacing, the frequency of interference with other radar devices is reduced, which makes it possible to suppress, for example, an increase in the noise floor of the signal after range FFT processing due to interference from chirp signals from other radar devices.

[0026] In addition, in this disclosure, each chirp signal Ch i The slope of a i and chirp period τ' i The value multiplied by each chirp signal Ch i The bandwidth B of the chirp signal Ch i By setting the number of sampling points M for each chirp signal Ch as shown in Figure 2, i The slope of a i This makes it possible to suppress false detection of ghosts due to interference from chirp signals from other radar devices, for example.

[0027] A specific example of the object detection process in the radar device 1 according to the embodiment will be described below. Fig. 3 is a flowchart showing an example of the object detection process in the radar device according to the embodiment.

[0028] In the object detection process shown in FIG. 3, the signal processing unit 3 resets the chirp number i (i=0, step S101), then increments the chirp number i (i=i+1, step S102), and generates the chirp signal Ch i Time domain signal per s i (t) magnitude (absolute value |s i It is determined whether (t)|) is less than a predetermined value (step S103).

[0029] Chirp signal Ch i Time domain signal per s i If the noise of (t) is less than the predetermined value (step S103; Yes), the signal processing unit 3 outputs the time domain signal s i (t) is subjected to distance FFT processing (step S105). i Time domain signal per s i If the noise of (t) is equal to or greater than the predetermined value (step S103; No), the signal processing unit 3 outputs the time domain signal s i A filter process is performed on (t) (step S104), and a distance FFT process is performed on the filtered time domain signal (step S105).

[0030] In step S104, the chirp signal Ch i Time domain signal per s i An example of a filter applied to (t) is an adaptive filter. Alternatively, instead of filter processing, a deep learning method such as a convolutional neural network (CNN) may be used.

[0031] Next, the signal processing unit 3 calculates the distance Bin(S i (f)=(x1, ,x M)) Each element x of frequency Bin m It is determined whether (m=1, . . . , M) is a normal value (step S106).

[0032] The process in step S106 is, for example, to calculate the distance Bin(S i (f)=(x1, ,x M )) Element x of each frequency Bin m |x in (m=1, ,M) m | 2 average value x m ave is calculated and the distance Bin(S i (f)=(x1, ,x M )) Frequency Bin element x m |x in (m=1, ,M) m | 2 is the average value x m If the value is more than twice the ave, the element x m is determined to be an abnormal value.

[0033] Distance Bin(S i (f)=(x1, ,x M )) Each element x of frequency Bin m If is a normal value (step S106; Yes), the signal processing unit 3 determines whether the chirp number i has reached the total number I of chirp signals included in one frame period (step S108), and repeats the processing from step S102 onwards until i=I (step S108; No).

[0034] Distance Bin(S i (f)=(x1, ,x M )) Each element x of frequency Bin m If any one or more of the distances Bin are abnormal values ​​(step S106; No), the signal processing unit 3 executes interpolation processing using each element of the other distance Bin (step S107), and proceeds to processing in step S108.

[0035] In the interpolation process in step S107, the element x that was found to be an abnormal value in step S106 ism , other distance Bin(S i (f)=(x1, ,x M )) Frequency Bin element x m An example of replacing

[0036] When i=I (step S108; Yes), a method using KR product extension processing is applied to the distance Bin within one frame period (step S109), velocity FFT processing is performed on the obtained signal (step S110), a Doppler heat map is obtained (step S111), and the processing from step S101 onwards is repeatedly performed.

[0037] In step S103 of the object detection process in the radar device 1 according to the above embodiment, the chirp signal Ch i Time domain signal per s i If it is determined that the noise in (t) is equal to or greater than a predetermined value (step S103; No), distance FFT processing is performed on the time domain signal after filtering in step S104 (step S105). This makes it possible to further suppress an increase in the noise floor of the signal after distance FFT processing due to interference from chirp signals from other radar devices, for example.

[0038] In step S106 of the object detection process in the radar device 1 according to the above embodiment, the distance Bin(S i (f)=(x1, ,x M )) Each element x of frequency Bin m If any one or more of these is determined to be an abnormal value (step S106; No), a method using KR product extension processing is applied to the distance Bin within one frame period after interpolation processing in step S107 (step S109), and velocity FFT processing is performed on the obtained signal (step S110). This makes it possible to further suppress false detection of ghosts due to interference of chirp signals from other radar devices, for example.

[0039] It should be noted that the above-described embodiments are intended to facilitate understanding of the present disclosure and are not intended to limit the present disclosure. The present disclosure may be modified or improved without departing from the spirit thereof, and equivalents thereof are also included in the present disclosure.

[0040] The present disclosure can have the following configurations as described above or instead of the above.

[0041] (1) A radar device using an FMCW (Frequency Modulated Continuous Wave) system, a transceiver unit that generates a composite signal of a transmission signal and a reception signal; a signal processing unit that acquires distance information and velocity information based on the composite signal; a control unit that controls the transceiver unit and the signal processing unit; Equipped with the transmission signal includes a plurality of chirp signals that are linearly frequency modulated within a predetermined frequency range within one frame period; the arrangement intervals of the plurality of chirp signals in the time axis direction are defined by a non-uniform array arrangement that can generate an equally-spaced array arrangement in which the chirp signals are arranged at equal intervals in the time axis direction by applying a predetermined extension process; Radar equipment. (2) The radar device according to (1), The extension process is a Khatri-Rao (KR) product extension process. Radar equipment. (3) The radar device according to (1) or (2), The non-uniformly spaced arrays are MRAs (Minimum Redundancy Arrays). Radar equipment. (4) The radar device according to (1) or (2), The non-uniformly spaced arrays are MHAs (Minimum Hole Arrays). Radar equipment. (5) The radar device according to (1) or (2) above, The non-uniformly spaced array sequences are Co-Prime Arrays. Radar equipment. (6) The radar device according to (1) or (2) above, The non-uniformly spaced array is a nested array. Radar equipment. (7) The radar device according to any one of (1) to (6) above, The control unit controlling the transceiver unit so that a value obtained by multiplying the slopes of the plurality of chirp signals by the chirp periods becomes a bandwidth of the chirp signals; controlling the signal processing unit so that the number of sampling points for each of the plurality of chirp signals is the same; Radar equipment. (8) The radar device according to any one of (1) to (7) above, The signal processing unit generating a time domain signal for each of the plurality of chirp signals, and if the noise of the time domain signal is equal to or greater than a predetermined value, performing a filtering process and then a distance FFT process; Radar equipment. (9) The radar device according to any one of (1) to (8) above, The signal processing unit If the data of the frequency bin of the distance bin after the distance FFT processing is an abnormal value, an interpolation process is performed using the data of the frequency bin of another distance bin, and then a velocity FFT process is performed. Radar equipment. (10) A detection method for a radar device using an FMCW (Frequency Modulated Continuous Wave) system that acquires distance information and speed information based on a composite signal of a transmission signal and a reception signal, comprising: the transmission signal includes a plurality of chirp signals that are linearly frequency modulated within a predetermined frequency range within one frame period; the arrangement intervals of the plurality of chirp signals in the time axis direction are defined by a non-uniform array arrangement that can generate an equally-spaced array arrangement in which the chirp signals are arranged at equal intervals in the time axis direction by applying a predetermined extension process; Detection method. (11) The detection method according to (10), The extension process is a Khatri-Rao (KR) product extension process. Detection method. (12) The detection method according to (10) or (11), The non-uniformly spaced arrays are MRAs (Minimum Redundancy Arrays). Detection method. (13) The detection method according to (10) or (11), The non-uniformly spaced arrays are MHAs (Minimum Hole Arrays). Detection method. (14) The detection method according to (10) or (11), The non-uniformly spaced array sequences are Co-Prime Arrays. Detection method. (15) The detection method according to (10) or (11), The non-uniformly spaced array is a nested array. Detection method.

[0042] The present disclosure makes it possible to realize a radar device and a detection method that can suppress a decrease in the accuracy of distance and speed detection caused by radio wave interference. [Explanation of symbols]

[0043] 1. Radar equipment 2 Transmitter / Receiver 3. Signal Processing Section 4. Control section

Claims

1. A radar device using an FMCW (Frequency Modulated Continuous Wave) system, a transceiver unit that generates a composite signal of a transmission signal and a reception signal; a signal processing unit that acquires distance information and velocity information based on the composite signal; a control unit that controls the transceiver unit and the signal processing unit; Equipped with the transmission signal includes a plurality of chirp signals that are linearly frequency modulated within a predetermined frequency range within one frame period; the arrangement intervals of the plurality of chirp signals in the time axis direction are defined by a non-uniform array arrangement that can generate an equally-spaced array arrangement in which the chirp signals are arranged at equal intervals in the time axis direction by applying a predetermined extension process; Radar equipment.

2. The radar device according to claim 1, The extension process is a Khatri-Rao (KR) product extension process. Radar equipment.

3. The radar device according to claim 2, The non-uniformly spaced arrays are MRAs (Minimum Redundancy Arrays). Radar equipment.

4. The radar device according to claim 2, The non-uniformly spaced array arrangement is MHAs (Minimum Hole Arrays). Radar equipment.

5. The radar device according to claim 2, The non-uniformly spaced array sequences are Co-Prime Arrays. Radar equipment.

6. The radar device according to claim 2, The non-uniformly spaced array is a nested array. Radar equipment.

7. The radar device according to any one of claims 1 to 6, The control unit controlling the transceiver unit so that a value obtained by multiplying the slopes of the plurality of chirp signals by the chirp periods becomes a bandwidth of the chirp signals; controlling the signal processing unit so that the number of sampling points for each of the plurality of chirp signals is the same; Radar equipment.

8. The radar device according to claim 7, The signal processing unit generating a time domain signal for each of the plurality of chirp signals, and if the noise of the time domain signal is equal to or greater than a predetermined value, performing a filtering process and then a distance FFT process; Radar equipment.

9. The radar device according to claim 7, The signal processing unit If the element of the frequency Bin of the distance Bin after the distance FFT processing is an abnormal value, an interpolation process is performed using the element of the frequency Bin of another distance Bin, and then a velocity FFT process is performed. Radar equipment.

10. A detection method for a radar device using an FMCW (Frequency Modulated Continuous Wave) system that acquires distance information and velocity information based on a composite signal of a transmission signal and a reception signal, comprising: the transmission signal includes a plurality of chirp signals that are linearly frequency modulated within a predetermined frequency range within one frame period; the arrangement intervals of the plurality of chirp signals in the time axis direction are defined by a non-uniform array arrangement that can generate an equally-spaced array arrangement in which the chirp signals are arranged at equal intervals in the time axis direction by applying a predetermined extension process; Detection method.

11. The detection method according to claim 10, The extension process is a Khatri-Rao (KR) product extension process. Detection method.

12. The detection method according to claim 11, The non-uniformly spaced arrays are MRAs (Minimum Redundancy Arrays). Detection method.

13. The detection method according to claim 11, The non-uniformly spaced array arrangement is MHAs (Minimum Hole Arrays). Detection method.

14. The detection method according to claim 11, The non-uniformly spaced array sequences are Co-Prime Arrays. Detection method.

15. The detection method according to claim 11, The non-uniformly spaced array is a nested array. Detection method.

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