Radar signal processing device, radar signal processing method, radar device, and vehicle-mounted device

Abstract

The radar signal processing device (22) includes: a distance and speed calculation unit (23) that repeatedly acquires a beat signal of a difference frequency between a frequency of a radar signal having a frequency that changes with the passage of time and a frequency of a reflected wave of the radar signal reflected by an observation target, repeatedly calculates a distance and a relative speed between the radar device (1) and the observation target using the acquired beat signal; an angle calculation unit (24) that calculates an incident angle at which the reflected wave is incident on the array antenna (17) using the acquired beat signal and a configuration interval of a plurality of reception antennas (17-1) to (17-N) included in the array antenna (17) that receives the reflected wave; and a determination unit (25) that determines whether the observation target is a detection target or a non-detection target due to electromagnetic noise based on the calculated incident angle, a plurality of distances, and a plurality of relative speeds.

Description

Technical Field

[0001] This disclosure relates to a radar signal processing apparatus and a radar signal processing method for calculating the distance between a radar device and an observed object, a radar device equipped with a radar signal processing apparatus, and a vehicle-mounted device equipped with a radar device. Background Technology

[0002] Among radar devices that calculate the distance between the radar device and the observed object, and the relative velocity between the radar device and the observed object, there are FMCW (Frequency Modulated Continuous Wave) radar devices that transmit radar signals with a frequency that changes over time. FMCW radar devices sometimes mistakenly detect objects that are not actually being detected, caused by electromagnetic noise, as the observed object.

[0003] Patent Document 1 discloses a radar device capable of preventing false detection of non-detectable objects caused by electromagnetic noise.

[0004] The radar signal transmitted by the radar device disclosed in Patent Document 1 includes a first transmitted wave whose frequency increases over time and a second transmitted wave whose frequency decreases over time. The radar device generates a first beat signal having a difference frequency between the frequency of the first transmitted wave and the frequency of the reflected wave (i.e., the first reflected wave) of the first transmitted wave reflected by the observed object. Furthermore, the radar device generates a second beat signal having a difference frequency between the frequency of the second transmitted wave and the frequency of the reflected wave (i.e., the second reflected wave) of the second transmitted wave reflected by the observed object.

[0005] The radar device extracts the frequency with the highest signal strength from the frequencies contained in the first beat signal as the first peak frequency. Furthermore, the radar device extracts the frequency with the highest signal strength from the frequencies contained in the second beat signal as the second peak frequency.

[0006] The radar device performs noise determination processing to determine whether the first peak frequency and the second peak frequency are caused by electromagnetic noise. In this noise determination processing, if the first peak frequency and the second peak frequency are approximately the same, it is determined that the first peak frequency and the second peak frequency are caused by electromagnetic noise.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2018-80938 Summary of the Invention

[0010] The problem the invention aims to solve

[0011] When performing noise determination processing on the radar device disclosed in Patent Document 1, a radar signal containing both a first transmitted wave and a second transmitted wave must be transmitted from the radar device.

[0012] Therefore, radar devices that transmit radar signals with only a first transmitted wave or only a second transmitted wave cannot perform this noise determination processing. Consequently, in radar devices that transmit radar signals with only a first transmitted wave or only a second transmitted wave, there is a problem where non-detectable objects caused by electromagnetic noise are sometimes mistakenly detected as observed objects.

[0013] This disclosure was made to solve the above-mentioned problems, and its purpose is to provide a radar signal processing apparatus and a radar signal processing method that can prevent false detection of non-detectable objects caused by electromagnetic noise, provided that the radar signal contains at least one of a transmitted wave whose frequency increases over time and a transmitted wave whose frequency decreases over time.

[0014] means for solving problems

[0015] The radar signal processing apparatus disclosed herein is characterized by comprising: a range-velocity calculation unit that repeatedly acquires a beat signal having a difference frequency between the frequency of a radar signal whose frequency varies with time and the frequency of a reflected wave of a radar signal reflected by an observed object; the range-velocity calculation unit repeatedly calculates at least one distance between the radar device and the observed object using the acquired beat signal, and repeatedly calculates at least one relative velocity between the radar device and the observed object using the acquired beat signal; and an angle calculation unit that uses the beat signal acquired by the range-velocity calculation unit and a plurality of receivers included in an array antenna for receiving reflected waves. The antenna configuration interval is set, and the incident angle of the reflected wave incident on the array antenna is calculated. The determination unit determines whether the observed object is a detection object or a non-detection object caused by electromagnetic noise based on the incident angle calculated by the angle calculation unit and multiple distances and multiple relative velocities calculated by the distance and velocity calculation unit. The determination unit performs determination processing based on multiple distances and multiple relative velocities calculated by the distance and velocity calculation unit to determine whether the observed object is a detection object or a non-detection object caused by electromagnetic noise only when the absolute value of the incident angle calculated by the angle calculation unit is below a first threshold corresponding to the resolution of the incident angle.

[0016] The effects of the invention

[0017] According to this disclosure, a radar signal processing apparatus is configured to include a determination unit that determines whether an observed object is a detection object or a non-detection object caused by electromagnetic noise based on an incident angle calculated by an angle calculation unit and multiple distances and multiple relative velocities calculated by a range-velocity calculation unit. Therefore, in the radar signal processing apparatus of this disclosure, as long as the radar signal contains at least one of a transmitted wave whose frequency increases over time and a transmitted wave whose frequency decreases over time, false detection of a non-detection object caused by electromagnetic noise can be prevented. Attached Figure Description

[0018] Figure 1 This is a structural diagram showing a vehicle-mounted device equipped with radar device 1 according to embodiment 1.

[0019] Figure 2 This is a structural diagram of a radar device 1 that includes the radar signal processing apparatus 22 of embodiment 1.

[0020] Figure 3 This is a hardware structure diagram showing the hardware of the radar signal processing device 22 according to Embodiment 1.

[0021] Figure 4 This is a hardware structure diagram of a computer when the radar signal processing device 22 is implemented by software or firmware.

[0022] Figure 5 This is a structural diagram showing the range and velocity calculation unit 23 of the radar signal processing device 22.

[0023] Figure 6 This is a structural diagram showing the angle calculation unit 24 of the radar signal processing device 22.

[0024] Figure 7 This is an explanatory diagram showing the signal processing of radar signals, received signals, beat signals, and the range and velocity calculation unit 23.

[0025] Figure 8 This is an explanatory diagram showing the radar signal, received signal, beat signal, and signal processing of the range and velocity calculation unit 23 when electromagnetic noise is input to the ADC21-n (n = 1, ..., N).

[0026] Figure 9 This is a flowchart illustrating the processing steps of the radar signal processing device 22, i.e., the radar signal processing method.

[0027] Figure 10 This is a flowchart showing the processing steps of the distance-velocity calculation unit 23.

[0028] Figure 11 This is a flowchart showing the processing steps of the angle calculation unit 24.

[0029] Figure 12 This is a flowchart showing the processing steps of the determination unit 25.

[0030] Figure 13 This is an explanatory diagram showing the signal processing of the angle calculation unit 24.

[0031] Figure 14 This is an explanatory diagram showing the incident angle θ of the reflected wave incident on the array antenna 17.

[0032] Figure 15 This is an explanatory diagram showing the range of the incident angle θ for noise determination processing performed by the determination unit 25.

[0033] Figure 16 This is a structural diagram of a radar device 1 that includes the radar signal processing apparatus 22 of embodiment 2.

[0034] Figure 17 This is a flowchart showing the processing steps of the determination unit 27.

[0035] Figure 18 This is an explanatory diagram showing the transmission time interval ΔT of the radar signal group radiated from radar device 1. Detailed Implementation

[0036] The following description, in order to illustrate the present disclosure in more detail, describes the manner in which the present disclosure is carried out with reference to the accompanying drawings.

[0037] Implementation method 1.

[0038] Figure 1 This is a structural diagram showing a vehicle-mounted device equipped with radar device 1 according to embodiment 1.

[0039] Figure 2 This is a structural diagram of a radar device 1 that includes the radar signal processing apparatus 22 of embodiment 1.

[0040] Figure 3 This is a hardware structure diagram showing the hardware of the radar signal processing device 22 according to Embodiment 1.

[0041] Vehicle-mounted devices are devices installed on vehicles such as cars, motorcycles, or bicycles. These devices include radar equipment to determine whether the observed object is a target for detection or a non-target caused by electromagnetic noise.

[0042] When radar device 1 is installed in a car, for example, the observed objects are other vehicles such as cars, pedestrians, or guardrails.

[0043] The radar device 1 includes a radar signal output unit 11, a transceiver unit 15, a beat signal generation unit 18, and a radar signal processing unit 22.

[0044] The radar signal output unit 11 includes an output control unit 12, a signal source 13, and a distributor 14.

[0045] The radar signal output unit 11 outputs a frequency modulation signal whose frequency changes over time as a radar signal to the transceiver unit 15 intermittently and repeatedly.

[0046] The output control unit 12 outputs a control signal indicating the output timing of the radar signal to the signal source 13 and the range and velocity calculation unit 23 (described later).

[0047] The signal source 13 outputs the frequency modulation signal as a radar signal to the distributor 14 intermittently and repeatedly according to the output timing indicated by the control signal output from the output control unit 12.

[0048] Distributor 14 divides the radar signals repeatedly output from signal source 13 into two parts.

[0049] The distributor 14 outputs the distributed radar signal of one party to the transmitting antenna 16 (described later) and outputs the distributed radar signal of the other party as a local oscillation signal to the frequency mixing unit 19 (described later).

[0050] The transceiver unit 15 is equipped with a transmitting antenna 16 and an array antenna 17.

[0051] The transceiver unit 15 sends various radar signals repeatedly output from the radar signal output unit 11 toward the observed object, and receives various radar signals reflected by the observed object as reflected waves.

[0052] The transceiver unit 15 outputs the received signals of each reflected wave to the beat signal generation unit 18.

[0053] The transmitting antenna 16 radiates various radar signals repeatedly output from the distributor 14 into space.

[0054] The array antenna 17 has multiple receiving antennas 17-1 to 17-N. N is an integer greater than or equal to 2.

[0055] The receiving antennas 17-n (n = 1, ..., N) receive the radar signals reflected by the observed object after the radar signals are radiated into space from the transmitting antenna 16, and output the received signals of the received reflected waves to the mixer 19-n of the frequency mixing unit 19.

[0056] exist Figure 2 In the transceiver unit 15 shown, the transmitting antenna 16 is directly connected to the distributor 14. However, this is just one example; an amplifier can also be connected between the distributor 14 and the transmitting antenna 16. The amplifier amplifies the radar signal output from the distributor 14 and outputs the amplified radar signal to the transmitting antenna 16.

[0057] In addition, Figure 2 In the transceiver unit 15 shown, the receiving antenna 17-n is directly connected to the frequency mixing unit 19. However, this is just one example. An amplifier can also be connected between the receiving antenna 17-n and the mixer 19-n. The amplifier amplifies the received signal output from the receiving antenna 17-n and outputs the amplified received signal to the mixer 19-n.

[0058] The beat signal generation unit 18 includes a frequency mixing unit 19, a filter unit 20, and an analog-to-digital converter 21.

[0059] The beat signal generation unit 18 generates a beat signal, which has a differential frequency between the frequency of each radar signal output from the radar signal output unit 11 and the frequency of each reflected wave received by the transceiver unit 15.

[0060] The beat signal generation unit 18 outputs the generated beat signals to the radar signal processing device 22.

[0061] The frequency mixing unit 19 includes multiple mixers 19-1 to 19-N.

[0062] Mixer 19-n (n = 1, ..., N) mixes the local oscillation signal output from distributor 14 with the received signal output from receiving antenna 17-n, thereby generating a beat signal having a differential frequency between the frequency of the local oscillation signal output from distributor 14 and the frequency of the received signal.

[0063] Mixer 19-n outputs the beat signal to the filtering processing unit 20-n, which will be described later.

[0064] The filter section 20 includes multiple filter processing sections 20-1 to 20-N.

[0065] The filtering processing unit 20-n (n = 1, ..., N) is implemented by LPF (Low Pass Filter) or BPF (Band Pass Filter), etc.

[0066] The filtering unit 20-n suppresses unwanted components such as spurious noise contained in the beat signal output from the mixer 19-n, and outputs the beat signal after suppressing unwanted components to the ADC (Analog to Digital Converter) 21-n, which will be described later.

[0067] The analog-to-digital converter 21 has multiple ADCs 21-1 to 21-N.

[0068] ADC21-n (n = 1, ..., N) converts the beat signal output from the filter processing unit 20-n into digital data and outputs the digital data to the distance and speed calculation unit 23, which will be described later.

[0069] The radar signal processing device 22 includes a range and velocity calculation unit 23, an angle calculation unit 24, a determination unit 25, and an observation object detection unit 26.

[0070] Distance and speed calculation unit 23, for example, is composed of Figure 3 The distance and speed calculation circuit 31 shown is implemented.

[0071] The distance and speed calculation unit 23 repeatedly acquires digital data output from ADC 21-n (n = 1, ..., N).

[0072] The distance and speed calculation unit 23 calculates composite data of N digital data by integrating the N digital data output from ADC 21-1 to 21-N.

[0073] The distance and velocity calculation unit 23 calculates the distance between the radar device 1 and the observed object each time it calculates the composite data, and also calculates the relative velocity between the radar device 1 and the observed object.

[0074] The distance between radar device 1 and the observed object is the distance between the transceiver unit 15 of radar device 1 and the observed object. Furthermore, the relative velocity between radar device 1 and the observed object is the relative velocity between the transceiver unit 15 of radar device 1 and the observed object.

[0075] The distance and velocity calculation unit 23 outputs the calculated distance and relative velocity to the determination unit 25 respectively.

[0076] Angle calculation unit 24, for example, is composed of Figure 3 The angle calculation circuit 32 shown is implemented.

[0077] The angle calculation unit 24 uses the digital data obtained by the distance and velocity calculation unit 23 and the configuration interval of the receiving antennas 17-1 to 17-N to calculate the incident angle of the reflected wave incident on the array antenna 17.

[0078] The angle calculation unit 24 outputs the incident angle to the determination unit 25.

[0079] For example, the determination unit 25 is composed of Figure 3 The determination circuit 33 shown is implemented.

[0080] The determination unit 25 determines whether the observed object is a detection object or a non-detection object caused by electromagnetic noise based on the incident angle calculated by the angle calculation unit 24 and multiple distances and multiple relative velocities calculated by the distance and velocity calculation unit 23.

[0081] That is, the determination unit 25 performs the following determination process only when the absolute value of the incident angle calculated by the angle calculation unit 24 is below the first threshold: based on multiple distances and multiple relative velocities calculated by the distance and velocity calculation unit 23, it determines whether the observed object is a detection object or a non-detection object caused by electromagnetic noise.

[0082] The determination unit 25 outputs the determination result, indicating whether the observed object is a detection object or a non-detection object caused by electromagnetic noise, to the observed object detection unit 26.

[0083] Electromagnetic noise is noise with a fixed frequency. However, electromagnetic noise is not limited to noise with a completely unchanged frequency; it also includes noise with minute frequency variations within a practically harmless range. As electromagnetic noise, we assume a continuous wave (CW) electromagnetic wave.

[0084] exist Figure 2 In the radar device 1 shown, regarding the noise source, it is assumed that the noise source exists outside the radar device 1. As a noise source, consider, for example, a wireless charging device used to charge electric vehicles.

[0085] The object detection unit 26, for example, is composed of Figure 3 The observed object detection circuit 34 is implemented as shown.

[0086] When the determination unit 25 determines that the observed object is the detection object, the observation object detection unit 26 outputs the distance and relative velocity calculated by the distance and velocity calculation unit 23, and the incident angle calculated by the angle calculation unit 24 as the detection result of the observed object to the outside of the radar device 1.

[0087] When the determination unit 25 determines that the observed object is a non-detectable object, the observation object detection unit 26 outputs information indicating that a non-detectable object caused by electromagnetic noise has been detected to the outside of the radar device 1.

[0088] exist Figure 2 In this context, it is assumed that the range and velocity calculation unit 23, angle calculation unit 24, determination unit 25, and observation object detection unit 26, which are structural elements of the radar signal processing device 22, are respectively composed of... Figure 3 The dedicated hardware implementation shown is as follows. That is, it is assumed that the radar signal processing device 22 is implemented by a range and velocity calculation circuit 31, an angle calculation circuit 32, a decision circuit 33, and an observed object detection circuit 34.

[0089] The distance and velocity calculation circuit 31, the angle calculation circuit 32, the determination circuit 33, and the observed object detection circuit 34 correspond, for example, to a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination thereof.

[0090] The structural elements of the radar signal processing device 22 are not limited to being implemented by dedicated hardware; the radar signal processing device 22 can also be implemented by software, firmware, or a combination of software and firmware.

[0091] Software or firmware is stored in the computer's memory in the form of a program. A computer is hardware that executes programs, such as CPU (Central Processing Unit), central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, processor, or DSP (Digital Signal Processor).

[0092] Figure 4 This is a hardware structure diagram of a computer when the radar signal processing device 22 is implemented by software or firmware.

[0093] When the radar signal processing device 22 is implemented by software or firmware, the program for causing the computer to execute each processing step in the range-velocity calculation unit 23, angle calculation unit 24, determination unit 25, and observed object detection unit 26 is stored in the memory 42. Then, the computer's processor 41 executes the program stored in the memory 42.

[0094] In addition, Figure 3 The diagram shows an example where the structural elements of the radar signal processing device 22 are implemented using dedicated hardware. Figure 4 The diagram shows an example of radar signal processing device 22 being implemented by software or firmware. However, this is only one example; it is also possible that some structural elements of radar signal processing device 22 are implemented by dedicated hardware, while the remaining structural elements are implemented by software or firmware.

[0095] Figure 5 This is a structural diagram showing the range and velocity calculation unit 23 of the radar signal processing device 22.

[0096] The distance and velocity calculation unit 23 includes a first spectrum calculation unit 51, a second spectrum calculation unit 52, and a distance and velocity calculation processing unit 53.

[0097] The first spectrum calculation unit 51 repeatedly acquires digital data output from ADC21-n (n=1, ..., N) in time with the output timing indicated by the control signal output from the output control unit 12.

[0098] The first spectrum calculation unit 51 performs a Fourier transform on each repeatedly acquired digital data in the distance direction, thereby repeatedly calculating the first spectrum fs. 1，a .

[0099] The first spectrum calculation unit 51 repeatedly calculates each first spectrum fs using the digital data output from ADC 21-n. 1，a Output to the second spectrum calculation unit 52.

[0100] The first spectrum calculation unit 51 adds the N digital data output from ADC21-1 to 21-N in time with the output timing indicated by the control signal output from the output control unit 12, thereby calculating the composite data of the N digital data.

[0101] The first spectrum calculation unit 51 performs a Fourier transform on the synthesized data in the distance direction each time it calculates the synthesized data, thereby calculating the first spectrum fs of the N receiving antennas 17-n. 1，b .

[0102] The first spectrum calculation unit 51 repeatedly calculates each first spectrum fs using the synthesized data. 1，b Output to the second spectrum calculation unit 52.

[0103] The second spectrum calculation unit 52 repeatedly obtains K (K is an integer greater than 2) first spectrum fs related to ADC21-n from the first spectrum calculation unit 51. 1，a .

[0104] The second spectrum calculation unit 52 acquires K first spectrum fs each time. 1，a At that time, for the K first-order spectrum fs 1，a Perform a Fourier transform in the Doppler direction to calculate the second spectrum fs. 2，a .

[0105] The second spectrum calculation unit 52 calculates the second spectrum fs related to ADC21-n. 2，a Output to angle calculation unit 24. The second spectrum fs output from the second spectrum calculation unit 52 to the angle calculation unit 24. 2，a Although it is not the relative velocity itself, it contains information related to the relative velocity. Therefore, the information related to the relative velocity is output from the second spectrum calculation unit 52 to the angle calculation unit 24.

[0106] The second spectrum calculation unit 52 pairs of K first-order spectra fs related to ADC21-n 1，aAccumulate the data, and then calculate the first spectrum fs after accumulation. 1，a Output to angle calculation unit 24. The first spectrum fs output from the second spectrum calculation unit 52 to the angle calculation unit 24 1，a Although it is not the distance itself, it contains information related to the distance. Therefore, the distance-related information is output from the second spectrum calculation unit 52 to the angle calculation unit 24.

[0107] The second spectrum calculation unit 52 repeatedly obtains K first-order spectra fs calculated using synthetic data from the first spectrum calculation unit 51. 1，b .

[0108] The second spectrum calculation unit 52 acquires K first spectrum fs each time. 1，b At that time, for the K first-order spectrum fs 1，b Perform a Fourier transform in the Doppler direction to calculate the second spectrum fs. 2，b .

[0109] The second spectrum calculation unit 52 calculates the second spectrum fs 2，b Output to the distance and speed calculation and processing unit 53.

[0110] The second spectrum calculation unit 52 pairs K first-order spectra fs 1，b Accumulate the data, and then calculate the first spectrum fs after accumulation. 1，b Output to the distance and speed calculation and processing unit 53.

[0111] Distance-velocity calculation processing unit 53 obtains the accumulated first spectrum fs from the second spectrum calculation unit 52. 1，b '.

[0112] The distance-velocity calculation and processing unit 53 obtains the first spectrum fs after each accumulation. 1，b At that time, the first spectrum fs after detection and accumulation 1，b The frequency corresponding to the peak value is the beat frequency.

[0113] The distance and velocity calculation and processing unit 53 calculates the distance between the radar device 1 and the observed object based on the detected beat frequency.

[0114] Distance-velocity calculation processing unit 53 obtains the second spectrum fs from the second spectrum calculation unit 52. 2，b .

[0115] Distance and velocity calculation processing unit 53 acquires the second spectrum fs each time. 2，b At that time, the detection and the second spectrum fs 2，b The frequency corresponding to the peak value is the Doppler frequency.

[0116] The distance and velocity calculation and processing unit 53 calculates the relative velocity between the radar device 1 and the observed object based on the detected Doppler frequency.

[0117] The distance and speed calculation processing unit 53 outputs the calculated distance and relative speed to the determination unit 25 each time it calculates the distance and relative speed.

[0118] Figure 6 This is a structural diagram showing the angle calculation unit 24 of the radar signal processing device 22.

[0119] The angle calculation unit 24 includes a third spectrum calculation unit 61 and an angle calculation processing unit 62.

[0120] The third spectrum calculation unit 61 obtains N first-order spectra fs from the second spectrum calculation unit 52 of the distance-velocity calculation unit 23. 1，a 'and N second-order spectrum fs 2，a .

[0121] The third spectrum calculation unit 61 generates N data points containing the first spectrum fs. 1，a 'and the second spectrum fs 2，a The third spectrum fs3 is calculated by performing a Fourier transform on the N distance Doppler maps.

[0122] The third spectrum calculation unit 61 outputs the third spectrum fs3 to the angle calculation processing unit 62.

[0123] The angle calculation processing unit 62 detects the frequency corresponding to the peak value of the third spectrum fs3 output from the third spectrum calculation unit 61.

[0124] The angle calculation processing unit 62 uses the frequency corresponding to the detected peak value and the configuration interval of the receiving antennas 17-1 to 17-N to calculate the incident angle of the reflected wave incident on the array antenna 17.

[0125] The angle calculation unit 24 outputs the incident angle to the determination unit 25.

[0126] Next, regarding Figure 2 The operation of the radar device 1 shown will be explained.

[0127] Figure 7 This is an explanatory diagram showing the signal processing of radar signals, received signals, beat signals, and the range and velocity calculation unit 23.

[0128] Figure 8 This is an explanatory diagram showing the radar signal, received signal, beat signal, and signal processing of the range and velocity calculation unit 23 when electromagnetic noise is input to the ADC21-n (n = 1, ..., N).

[0129] exist Figure 7 and Figure 8In the diagram, Tx(1), Tx(2), Tx(3), ..., Tx(K) represent radar signals, and Rx(1), Rx(2), Rx(3), ..., Rx(K) represent received signals.

[0130] The radar signal Tx(k) (k = 1, ..., K) is a frequency-modulated signal whose frequency decreases over time. T is the scan time of the radar signal Tx(k), which is in the microsecond range. BW is the bandwidth of the radar signal Tx(k).

[0131] exist Figure 7 and Figure 8 In this context, the radar signal Tx(k) is a frequency-modulated signal whose frequency decreases over time. However, this is just one example; the radar signal Tx(k) can also be a frequency-modulated signal whose frequency increases over time. Furthermore, the radar signal Tx(k) can also include both frequency-modulated signals whose frequency increases over time and frequency-modulated signals whose frequency decreases over time.

[0132] First, the output control unit 12 outputs a control signal representing the output timing of the radar signal Tx(k) to the signal source 13 and the range and velocity calculation unit 23, respectively.

[0133] like Figure 7 and Figure 8 As shown, the time interval for the output timing of the radar signal Tx(k) is longer than the scanning time T.

[0134] The signal source 13 repeatedly outputs the radar signal Tx(k) to the distributor 14 according to the output timing indicated by the control signal output from the output control unit 12.

[0135] Each time the distributor 14 receives a radar signal Tx(k) from the signal source 13, it divides the radar signal Tx(k) into two parts.

[0136] The distributor 14 outputs the distributed radar signal Tx(k) of one side to the transmitting antenna 16, and outputs the distributed radar signal Tx(k) of the other side as a local oscillation signal Lo(k) to the mixers 19-1 to 19-N in the frequency mixing section 19 respectively.

[0137] Each time the transmitting antenna 16 receives a radar signal Tx(k) from the distributor 14, it radiates the radar signal Tx(k) into space.

[0138] The receiving antenna 17-n (n = 1, ..., N) of the array antenna 17 receives the radar signal Tx(k) reflected by the observed object after the radar signal Tx(k) is radiated into space from the transmitting antenna 16, and outputs the received signal Rx(k) of the reflected wave to the mixer 19-n.

[0139] Mixer 19-n mixes the local oscillation signal Lo(k) with the received signal Rx(k) each time it receives the local oscillation signal Lo(k) from distributor 14 and the received signal Rx(k) from receiving antenna 17-n.

[0140] Mixer 19-n generates a beat signal with a differential frequency between the frequency of the local oscillation signal Lo(k) and the frequency of the received signal Rx(k) by mixing the local oscillation signal Lo(k) with the received signal Rx(k).

[0141] Each time a beat signal is generated, the mixer 19-n outputs the generated beat signal to the filter processing unit 20-n.

[0142] In addition, during the period when the mixer 19-n does not output the local oscillation signal Lo(k) from the distributor 14, it does not generate the beat signal and does not output the beat signal to the filter processing unit 20-n.

[0143] Each time the filter processing unit 20-n receives a beat signal from the mixer 19-n, it suppresses unwanted components such as spurious noise contained in the beat signal and outputs the beat signal after suppressing unwanted components to the ADC 21-n.

[0144] Each time the ADC21-n receives a beat signal from the filter processing unit 20-n, it converts the beat signal into digital data and outputs the digital data to the range and velocity calculation unit 23 of the radar signal processing device 22.

[0145] When electromagnetic noise is input to the ADC21, such as Figure 8 As shown, electromagnetic noise sometimes overlaps with beat signals.

[0146] The operation period of ADC21-n is equivalent to the period during which mixer 19-n outputs the beat signal to filter processing unit 20-n.

[0147] The operation of the radar signal processing device 22 will be explained below.

[0148] Figure 9 This is a flowchart illustrating the processing steps of the radar signal processing device 22, i.e., the radar signal processing method.

[0149] Figure 10 This is a flowchart showing the processing steps of the distance-velocity calculation unit 23.

[0150] Figure 11 This is a flowchart showing the processing steps of the angle calculation unit 24.

[0151] Figure 12 This is a flowchart showing the processing steps of the determination unit 25.

[0152] The distance and speed calculation unit 23 repeatedly acquires digital data output from ADC 21-n (n = 1, ..., N).

[0153] The distance and velocity calculation unit 23 calculates the distance between the radar device 1 and the observed object each time it acquires digital data from the ADC 21-n. Figure 9 Step ST1).

[0154] Furthermore, the distance-velocity calculation unit 23 uses this digital data to calculate the relative velocity between the radar device 1 and the observed object. Figure 9 Step ST1).

[0155] The distance and velocity calculation unit 23 outputs the calculated distance and relative velocity to the angle calculation unit 24 each time it calculates the distance and relative velocity separately.

[0156] The distance and velocity calculation unit 23 calculates composite data of multiple digital data output from ADCs 21-1 to 21-N.

[0157] The distance and velocity calculation unit 23 uses the composite data to calculate the distance between the radar device 1 and the observed object each time it calculates composite data. Figure 9 Step ST1).

[0158] Furthermore, the range and velocity calculation unit 23 uses this composite data to calculate the relative velocity between the radar device 1 and the observed object. Figure 9 Step ST1).

[0159] The distance and speed calculation unit 23 outputs the calculated distance and relative speed to the determination unit 25 each time it calculates the distance and relative speed.

[0160] The following is a detailed explanation of the calculation process of the distance and speed calculation unit 23.

[0161] The first spectrum calculation unit 51, in synchronization with the output timing indicated by the control signal output from the output control unit 12, repeatedly acquires digital data output from the ADC 21-n (n=1, ..., N) during the period when the local oscillation signal Lo(k) is output from the distributor 14.

[0162] Each time digital data is acquired from ADC21-n, the first spectrum calculation unit 51 performs a Fourier transform on the digital data in the distance direction, thereby calculating the first spectrum fs. 1，a ( Figure 10 Step ST11).

[0163] exist Figure 7 and Figure 8 In the figure, FFT(1) shows the Fourier transform of the distance direction performed by the first spectrum calculation unit 51.

[0164] By performing a Fourier transform on the digital data in the distance direction, the spectral values ​​of the received signal Rx(k) (k=1、…、K) of the reflected wave from the observed object are accumulated to the beat frequency F shown in the following equation (1). sb＿r .

[0165]

[0166] In equation (1), R is Figure 2 The distance between radar device 1 and the observed object is shown, where c is the speed of light.

[0167] Furthermore, by performing a Fourier transform on the digital data in the distance direction, the spectral values ​​of the electromagnetic noise are accumulated to the frequency F of the electromagnetic noise. n＿r .

[0168] The first spectrum calculation unit 51 calculates K first spectrum fs each time. 1，a At that time, the K first-order spectrum fs 1，a Output to the second spectrum calculation unit 52.

[0169] Furthermore, the first spectrum calculation unit 51 synchronously integrates the N digital data output from ADC21-1 to 21-N with the output timing indicated by the control signal output from the output control unit 12, thereby calculating the composite data of the N digital data.

[0170] The first spectrum calculation unit 51 performs a Fourier transform on the synthesized data in the distance direction each time it calculates the synthesized data, thereby calculating the first spectrum fs of the N receiving antennas 17-n. 1，b .

[0171] The first spectrum calculation unit 51 calculates K first spectrum fs each time. 1，b At that time, the K first-order spectrum fs 1，b Output to the second spectrum calculation unit 52.

[0172] The second spectrum calculation unit 52 repeatedly obtains K first-order spectrum fs related to ADC21-n from the first spectrum calculation unit 51. 1，a .

[0173] The second spectrum calculation unit 52 acquires K first spectrum fs each time. 1，a At that time, for the K first-order spectrum fs 1，a Perform a Fourier transform in the Doppler direction to calculate the second spectrum fs. 2，a ( Figure 10 Step ST12).

[0174] exist Figure 7 and Figure 8In the figure, FFT(2) shows the Fourier transform of the Doppler direction performed by the second spectrum calculation unit 52.

[0175] By analyzing the K first-order spectra fs 1，a Performing a Fourier transform in the Doppler direction, the spectral values ​​of the received signal Rx(k) from the reflected wave of the observed object are accumulated to... Figure 2 The Doppler frequency F corresponding to the relative velocity between the radar device 1 and the observed object is given by the following equation (2). sb＿v .

[0176]

[0177] In equation (2), f is the center frequency of the local oscillation signal Lo(k), and v is... Figure 2 The relative velocity between radar device 1 and the observed object is shown.

[0178] Furthermore, by analyzing the K first-order spectra fs 1，a Performing a Fourier transform in the Doppler direction, the spectral values ​​of the electromagnetic noise are accumulated to the following Doppler frequency F. n＿v The Doppler frequency F n＿v Corresponding to Figure 2 The phase difference between the radar device 1 and the noise source relative to each other, and the phase difference between the noise source and the radar signal, are the sum of these two phase differences.

[0179] The second spectrum calculation unit 52 calculates the second spectrum fs each time. 2，a At that time, the second spectrum fs 2，a Output to angle calculation unit 24.

[0180] In addition, the second spectrum calculation unit 52 accumulates K first spectrum fs 1，a The accumulated first spectrum fs 1，a Output to angle calculation unit 24.

[0181] The second spectrum calculation unit 52 repeatedly obtains K first-order spectra fs calculated using synthetic data from the first spectrum calculation unit 51. 1，b .

[0182] The second spectrum calculation unit 52 acquires K first spectrum fs each time. 1，b At that time, for the K first-order spectrum fs 1，b Perform a Fourier transform in the Doppler direction to calculate the second spectrum fs. 2，b .

[0183] The second spectrum calculation unit 52 calculates the second spectrum fs each time. 2，b At that time, the second spectrum fs 2，b Output to the distance and speed calculation and processing unit 53.

[0184] The second spectrum calculation unit 52 accumulates the K first-order spectrum fs calculated using the synthesized data. 1，b The accumulated first spectrum fs 1，b Output to the distance and speed calculation and processing unit 53.

[0185] exist Figure 2 In the radar device 1 shown, the second spectrum calculation unit 52 calculates K first spectra fs using synthetic data. 1，b The second spectrum fs is calculated by performing a Fourier transform in the Doppler direction. 2，b , will the second spectrum fs 2，b The distance and velocity calculation processing unit 53 outputs the signal. However, this is only one example; the second spectrum calculation unit 52 can also output the second spectrum fs to the angle calculation unit 24. 2，a The distance and velocity calculation processing unit 53 outputs the result. Furthermore, the second spectrum calculation unit 52 can also output the accumulated first spectrum fs from the angle calculation unit 24. 1，a Output to the distance and speed calculation and processing unit 53.

[0186] The distance-velocity calculation processing unit 53 receives the accumulated first spectrum fs from the second spectrum calculation unit 52 each time. 1，b At that time, the detection was related to the first spectrum fs 1，b The peak value corresponds to the beat frequency F. sb＿r .

[0187] Specifically, the distance-velocity calculation and processing unit 53 processes the first spectrum fs 1，b The multiple spectral values ​​included and the threshold Th used for beat frequency detection b Compare them.

[0188] The distance and velocity calculation and processing unit 53 detects multiple spectral values ​​that are higher than the threshold Th. b Large spectral values ​​are used as peak values. The threshold Th used for beat frequency detection. b It can be stored in the internal memory of the distance and speed calculation and processing unit 53, or it can be provided from the outside of the radar device 1.

[0189] When the distance-velocity calculation and processing unit 53 detects a peak value, it detects the first spectrum fs. 1，b The frequency corresponding to the peak value is taken as the beat frequency F. sb＿r .

[0190] Beat frequency F detected by distance and velocity calculation and processing unit 53 sb＿r It could be a frequency related to the observed object, but in the case of electromagnetic noise being input into the ADC21, it could also be the frequency F of the electromagnetic noise. n＿r .

[0191] The distance-velocity calculation processing unit 53 detects the first spectrum fs 1，b The peak value corresponds to the beat frequency F. sb＿r At that time, the shooting frequency F sb＿r Substitute into the following equation (3) to calculate. Figure 2 The distance R between the radar device 1 shown and the observed object is... Figure 10 Step ST13).

[0192]

[0193] The distance R calculated by the distance and velocity calculation and processing unit 53 may be the distance between the radar device 1 and the observed object, but if electromagnetic noise is input into the ADC21-n, it may also be a false detection distance based on electromagnetic noise.

[0194] Distance-velocity calculation processing unit 53 receives the second spectrum fs from the second spectrum calculation unit 52 each time. 2，b At that time, the detection and the second spectrum fs 2，b The peak value corresponds to the Doppler frequency F. sb＿v .

[0195] Specifically, the distance-velocity calculation and processing unit 53 processes the second spectrum fs. 2，b The included multiple spectral values ​​and the threshold Th used for Doppler frequency detection d Compare them.

[0196] The distance and velocity calculation and processing unit 53 detects multiple spectral values ​​that are higher than the threshold Th. d Large spectral values ​​are used as peak values. The threshold Th used for Doppler frequency detection. d It can be stored in the internal memory of the distance and speed calculation and processing unit 53, or it can be provided from the outside of the radar device 1.

[0197] When the distance-velocity calculation and processing unit 53 detects a peak value, it detects the second spectrum fs. 2，b The frequency corresponding to the peak value is the Doppler frequency F. sb＿v .

[0198] The Doppler frequency F detected by the distance and velocity calculation processing unit 53 sb＿v It could be a frequency related to the observed object, but in the case of electromagnetic noise being input into the ADC21-n, it could also be the Doppler frequency F of the electromagnetic noise. n＿v .

[0199] The distance-velocity calculation processing unit 53 detects the second spectrum fs 2，b The peak value corresponds to the Doppler frequency F. sb＿v At that time, the Doppler frequency F sb＿vSubstitute into the following equation (4) to calculate. Figure 2 The relative velocity v between the radar device 1 and the observed object shown is... Figure 10 Step ST13).

[0200]

[0201] The relative velocity v calculated by the range velocity calculation and processing unit 53 may be the relative velocity between the radar device 1 and the observed object, but in the case of electromagnetic noise being input into the ADC21-n, it may also be the relative velocity caused by electromagnetic noise.

[0202] The distance and velocity calculation processing unit 53 outputs the distance R and relative velocity v to the determination unit 25 each time it calculates the distance R and relative velocity v respectively.

[0203] Figure 13 This is an explanatory diagram showing the signal processing of the angle calculation unit 24.

[0204] The third spectrum calculation unit 61 of the angle calculation unit 24 obtains N first spectrum fs from the second spectrum calculation unit 52 of the distance and velocity calculation unit 23. 1，a 'and N second-order spectrum fs 2，a .

[0205] The third spectrum calculation unit 61 generates a range Doppler map (n) associated with ADC21-n, which contains N first-order spectrum fs. 1，a The first spectrum fs associated with ADC21-n in ' 1，a '(n) and N second-order spectrum fs 2，a The second spectrum fs associated with ADC21-n 2，a (n). The third spectrum calculation unit 61 generates a total of N distance Doppler maps (1) to (N).

[0206] The third spectrum calculation unit 61 calculates the spectrum by performing Fourier transform on the N range Doppler maps (1) to (N). Figure 13 The third spectrum fs3 shown Figure 11 Step ST21).

[0207] The third spectrum calculation unit 61 outputs the third spectrum fs3 to the angle calculation processing unit 62.

[0208] The angle calculation processing unit 62 obtains the third spectrum fs3 from the third spectrum calculation unit 61.

[0209] The angle calculation and processing unit 62 detects the frequency F corresponding to the peak value of the third spectrum fs3. sb＿θ .

[0210] As shown in equation (5) below, the angle calculation processing unit 62 uses the frequency F corresponding to the detected peak value. sb＿θ Given the configuration interval d of receiving antennas 17-1 to 17-N, calculate the incident angle θ of the reflected wave incident on array antenna 17. Figure 9 Step ST2 Figure 11 Step ST22).

[0211]

[0212] In equation (5), λ is the wavelength of the radar signal.

[0213] Figure 14 This is an explanatory diagram showing the incident angle θ of the reflected wave incident on the array antenna 17.

[0214] exist Figure 14 In the diagram, receiving antenna 17-1 is positioned at the origin of the xy coordinate system, and receiving antennas 17-1 to 17-N are positioned in a direction parallel to the y-axis.

[0215] The interval between receiving antenna 17-n and receiving antenna 17-(n+1) is d. n = 1, 2, ..., N-1.

[0216] The angle calculation unit 24 outputs the incident angle θ to the determination unit 25.

[0217] The angle θ calculated by the angle calculation processing unit 62 may be the incident angle of the reflected wave incident on the array antenna 17, but in the case of electromagnetic noise being input to the ADC21-n, it may also be the angle caused by electromagnetic noise.

[0218] The determination unit 25 determines whether the observed object is a detection object or a non-detection object caused by electromagnetic noise based on the incident angle θ calculated by the angle calculation unit 24 and multiple distances R and multiple relative velocities v calculated by the distance velocity calculation processing unit 53 of the distance velocity calculation unit 23.

[0219] The noise determination process of the determination unit 25 will be explained in detail below.

[0220] First, the determination unit 25 compares the absolute value of the incident angle θ with a first threshold Th1. The first threshold Th1 is, for example, a value that is half the resolution of the incident angle θ. The first threshold Th1 can be stored in the internal memory of the determination unit 25 or provided from outside the radar signal processing device 22.

[0221] If the absolute value of the incident angle θ is below the first threshold Th1 ( Figure 9 Step ST3: If yes, then the determination unit 25 performs the noise determination process shown below. Figure 9 Step ST4).

[0222] If the absolute value of the incident angle θ is greater than the first threshold Th1 ( Figure 9 If step ST3 is not performed, then the determination unit 25 will not perform the noise determination process shown below.

[0223] When electromagnetic noise is input to ADCs 21-1 to 21-N respectively, the signal wiring configuration of each ADC 21-n corresponding to receiving antennas 17-1 to 17-N is very short compared to the wavelength of the electromagnetic noise. Therefore, the noise caused by each signal wiring can be considered to be in phase. The state in which the output signals of ADCs 21-1 to 21-N are in phase is frequency F. sb＿θ =0, meaning the incident angle θ is 0 degrees. Therefore, false detections of non-detectable objects caused by electromagnetic noise occur when the incident angle θ is near 0 degrees. That is, false detections of non-detectable objects caused by electromagnetic noise occur when the absolute value of the incident angle θ is below the first threshold Th1. In other words, when the absolute value of the incident angle θ is greater than the first threshold Th1, the probability of false detections of non-detectable objects caused by electromagnetic noise is low.

[0224] Figure 15 This is an explanatory diagram showing the range of the incident angle θ for noise determination processing performed by the determination unit 25.

[0225] The range of the incident angle θ for noise determination processing is from -1st threshold Th1 to +1st threshold Th1.

[0226] The range of incident angle θ for detecting the observed object is wider than the range of incident angle θ for noise determination processing, and includes the range of incident angle θ for noise determination processing.

[0227] The determination unit 25 performs noise determination processing only when the absolute value of the incident angle θ is below the first threshold Th1, and only when the absolute value of the incident angle θ is greater than the first threshold Th1. Figure 9 Step ST3: If not, the noise determination process shown below is not performed. Therefore, it is possible to suppress the increase in processing load or storage associated with the noise determination process.

[0228] The determination unit 25 obtains M (M is an integer of 2 or more) distances R and M relative velocities v from the distance-velocity calculation and processing unit 53. Figure 12 Step ST31).

[0229] Here, for the sake of simplicity, it is assumed that the M distances R repeatedly calculated by the distance and velocity calculation and processing unit 53 are all the distances between the radar device 1 and the observed object or the false detection distances based on electromagnetic noise.

[0230] Furthermore, assume that all M relative velocities v repeatedly calculated by the distance and velocity calculation and processing unit 53 are the relative velocities between the radar device 1 and the observed object or the relative velocities caused by electromagnetic noise.

[0231] The decision unit 25 calculates the difference ΔR between the distance calculated in the first calculation and the distance calculated in the Mth calculation among the M distances R. M The absolute value of |ΔR M |

[0232] Decision section 25 pairs of differential ΔR M The absolute value of |ΔR M The value is compared with a second threshold Th2. The second threshold Th2 is, for example, the value of the resolution of the distance R calculated by the distance-velocity calculation unit 23 plus r. r is, for example, twice the resolution of the distance R. The second threshold Th2 can be stored in the internal memory of the determination unit 25 or provided externally to the radar signal processing device 22.

[0233] The frequency of the electromagnetic noise output from the noise source is a fixed frequency. Therefore, if the distance R calculated by the distance-velocity calculation unit 23 is a false detection distance based on electromagnetic noise, the change in the M distances R repeatedly calculated by the distance-velocity calculation unit 23 is very small, and the absolute value of the change in distance R is considered to be |ΔR|. M |Below the second threshold Th2.

[0234] For example, if the observed object is stationary, Figure 2 If the radar device 1 shown is moved, then Figure 2 The distance between the radar device 1 shown and the observed object changes. Consider a stationary observed object, such as a guardrail.

[0235] Therefore, when the object of observation is a stationary object, if Figure 2 When the radar device 1 shown moves, the absolute value of the change in M ​​distances R repeatedly calculated by the distance-velocity calculation unit 23, |ΔR|, is considered to be... M | Larger than the second threshold Th2.

[0236] For example, when the object being observed is equipped with Figure 2 In the case of oncoming vehicles of the vehicle shown in the radar device 1, if Figure 2 If the radar device 1 shown is moved, then Figure 2 The distance between the radar device 1 shown and the observed object varies greatly.

[0237] Therefore, when the observed objects are oncoming vehicles, if Figure 2 When the radar device 1 shown moves, the absolute value of the change in M ​​distances R repeatedly calculated by the distance-velocity calculation unit 23, |ΔR|, is considered to be...M is greater than the second threshold Th2.

[0238] For example, when the observed object is a preceding vehicle of a vehicle equipped with the Figure 2 radar device 1 shown, even if the Figure 2 radar device 1 shown moves, Figure 2 the distance between the radar device 1 shown and the observed object sometimes hardly changes. When the vehicle equipped with the Figure 2 radar device 1 shown travels in the same direction at substantially the same speed as the preceding vehicle, Figure 2 the distance between the radar device 1 shown and the observed object hardly changes.

[0239] Therefore, when the observed object is a preceding vehicle, even if the Figure 2 radar device 1 shown moves, the absolute value |ΔR M | of the change in the M distances R repeatedly calculated by the distance - speed calculation unit 23 is sometimes not greater than the second threshold Th2.

[0240] If the absolute value |ΔR M | of the difference ΔR M is greater than the second threshold Th2 ( Figure 12 in step ST32: Yes case), the determination unit 25 determines that the observed object is a detection object and not a noise source ( Figure 12 in step ST35).

[0241] Except for the case where the observed object is a stationary object such as a guardrail, in the case where the observed object is, for example, an oncoming vehicle, etc., the determination unit 25 also determines that "the observed object is not a noise source".

[0242] If the absolute value |ΔR M | of the difference ΔR M is less than or equal to the second threshold Th2 ( Figure 12 in step ST32: No case), the determination unit 25 compares the absolute value of the M relative speeds v with the third threshold Th3. As the third threshold Th3, for example, a speed of 1 km / h is used. However, this is just an example, and the third threshold Th3 can also be 2 km / h or 3 km / h, etc. The third threshold Th3 can be stored in the internal memory of the determination unit 25, or can be provided from outside the radar signal processing device 22.

[0243] The relative velocity v caused by electromagnetic noise varies not only according to the relative velocity change between radar device 1 and the noise source, but also according to the frequency of the electromagnetic noise, the scanning time of the radar signal, and the output timing of the radar signal. Therefore, the relative velocity v caused by electromagnetic noise is likely to be a value other than 0. Therefore, when the third threshold Th3 is much smaller than the maximum value of the relative velocity between radar device 1 and the observed object, if the relative velocity v calculated by the range velocity calculation unit 23 is the relative velocity caused by electromagnetic noise, then it is highly likely that the absolute values ​​of all M relative velocities v repeatedly calculated by the range velocity calculation unit 23 are greater than the third threshold.

[0244] For example, when the observed object is a vehicle moving forward, if the installation Figure 2 If the vehicle carrying radar device 1 is traveling in the same direction at approximately the same speed as the vehicle in front, then... Figure 2 The relative speed v between the radar device 1 and the vehicle in front is close to 0. Therefore, if the relative speed v calculated by the distance-speed calculation unit 23 is the relative speed between the radar device 1 and the vehicle in front, there is a high probability that one or more of the M relative speeds v repeatedly calculated by the distance-speed calculation unit 23 will be below the third threshold Th3.

[0245] If the absolute values ​​of all M relative velocities v are greater than the third threshold Th3 ( Figure 12 Step ST33: If yes, then the determination unit 25 determines that the observed object is not a detection object and is a noise source. Figure 12 Step ST34).

[0246] If more than one of the absolute values ​​of the M relative velocities v is below the third threshold Th3 ( Figure 12 Step ST33: If not, then the determination unit 25 determines that the observed object is the detected object and is not a noise source. Figure 12 Step ST35).

[0247] For example, if the object of observation is a moving vehicle, the determination unit 25 is likely to determine that "the object of observation is not electromagnetic noise".

[0248] When the determination unit 25 determines that the observed object is the detection object and not a noise source, Figure 9 Step ST5 (if not), output the M distances R, M relative velocities v, and incident angle θ to the object detection unit 26 respectively.

[0249] The object detection unit 26 outputs M distances R, M relative velocities v, and incident angle θ to the outside of the radar device 1 respectively. Figure 9 Step ST6).

[0250] When the determination unit 25 determines that the observed object is not the detected object and is a noise source ( Figure 9 Step ST5: If yes, discard the M distances R, M relative velocities v, and incident angle θ respectively.

[0251] When the determination unit 25 determines that the observed object is a non-detectable object, the observation object detection unit 26 outputs information indicating that a non-detectable object caused by electromagnetic noise has been detected to the outside of the radar device 1.

[0252] In addition, the object detection unit 26 can also output the false detection distance R based on electromagnetic noise, the relative velocity v caused by electromagnetic noise, and the incident angle θ to the outside of the radar device 1.

[0253] Here, for the sake of simplicity, we assume that the M distances R repeatedly calculated by the distance and velocity calculation unit 23 are all the distances between the radar device 1 and the observed object or the false detection distances based on electromagnetic noise.

[0254] Furthermore, assume that all M relative velocities v repeatedly calculated by the distance-velocity calculation unit 23 are the relative velocities between the radar device 1 and the observed object, or the relative velocities caused by electromagnetic noise.

[0255] However, when the reflected wave from the observed object is received by the receiving antenna 17-n at the correct timing, and electromagnetic noise from the noise source is input to the ADC 21-n, for example, if there is only one observed object, the range-velocity calculation unit 23 calculates two distances R in M ​​calculation processes. One of the two distances R is the distance R between the radar device 1 and the observed object, and the other distance R is the false detection distance R based on the electromagnetic noise. However, the range-velocity calculation unit 23 cannot determine which of the two calculated distances R is the distance R between the radar device 1 and the observed object, and which distance R is the false detection distance R based on the electromagnetic noise.

[0256] Furthermore, the range velocity calculation unit 23 calculates two relative velocities v in M ​​calculation processes. One of the relative velocities v is the relative velocity v between the radar device 1 and the observed object, and the other relative velocity v is the relative velocity v caused by electromagnetic noise. However, the range velocity calculation unit 23 cannot determine which of the two calculated relative velocities v is the relative velocity v between the radar device 1 and the observed object, and which relative velocity v is the relative velocity v caused by electromagnetic noise.

[0257] The determination unit 25 obtains (2×M) distances R and (2×M) relative velocities v from the distance and velocity calculation unit 23 as the processing result of M calculations.

[0258] When the determination unit 25 obtains (2×M) distances R from the distance-velocity calculation unit 23, it classifies the (2×M) distances R into groups related to the observed object and groups related to the noise source. Here, for ease of explanation, let the group related to the observed object be group (1) and the group related to the noise source be group (2).

[0259] Furthermore, when the determination unit 25 obtains (2×M) relative velocities v from the distance-velocity calculation unit 23, it classifies the (2×M) relative velocities v into a group (1) related to the observed object and a group (2) related to the noise source.

[0260] The process of classifying (2×M) distances R into two groups (1)(2) and the process of classifying (2×M) relative velocities v into two groups (1)(2) are known techniques, so detailed descriptions are omitted.

[0261] The determination unit 25 performs the above-described determination process on the two groups (1) and (2) respectively, thereby determining whether the observed object is a noise source. Figure 9 Step ST5).

[0262] By performing the above-described determination process, it is determined that group (1) is a group related to the observed object. Therefore, the determination unit 25 outputs the distance R belonging to group (1) as the distance R between the radar device 1 and the observed object to the observed object detection unit 26. In addition, the determination unit 25 outputs the relative velocity v belonging to group (1) as the relative velocity v between the radar device 1 and the observed object to the observed object detection unit 26. Furthermore, the determination unit 25 outputs the incident angle θ belonging to group (1) as the incident angle θ to the observed object detection unit 26.

[0263] By performing the above-described determination process, group (2) is determined to be a group related to a noise source. Therefore, the determination unit 25 discards the distance R belonging to group (2) as a false detection distance R based on electromagnetic noise. In addition, the determination unit 25 discards the relative velocity v belonging to group (2) as a relative velocity v caused by electromagnetic noise. Furthermore, the determination unit 25 discards the incident angle θ belonging to group (2).

[0264] In Embodiment 1 described above, the radar signal processing apparatus 22 includes: a range-velocity calculation unit 23, which repeatedly acquires a beat signal having a frequency difference between the frequency of a radar signal whose frequency changes over time and the frequency of the reflected wave of the radar signal reflected by the observed object; repeatedly calculates the distance between the radar device 1 and the observed object using the acquired beat signal; and repeatedly calculates the relative velocity between the radar device 1 and the observed object using the acquired beat signal; and an angle calculation unit 24, which calculates the incident angle of the reflected wave incident on the array antenna 17 using the beat signal acquired by the range-velocity calculation unit 23 and the arrangement interval of the plurality of receiving antennas 17-1 to 17-N included in the array antenna 17 for receiving the reflected wave. Furthermore, the radar signal processing apparatus 22 is configured to include a determination unit 25, which determines whether the observed object is a detection object or a non-detection object caused by electromagnetic noise based on the incident angle calculated by the angle calculation unit 24 and the plurality of distances and plurality of relative velocities calculated by the range-velocity calculation unit 23. Therefore, in the radar signal processing device 22, as long as the radar signal contains at least one of a transmitted wave whose frequency increases over time and a transmitted wave whose frequency decreases over time, it is possible to prevent false detection of non-detectable objects caused by electromagnetic noise.

[0265] exist Figure 2 In the radar signal processing apparatus 22 shown, the noise caused by the signal wiring within each ADC 21-n can be considered to be in phase. However, due to the difference in wiring length among the various signal wirings, the noise caused by each signal wiring can sometimes not be considered to be in phase. Furthermore, not only the receiving antennas 17-1 to 17-N, but also the transmitting antenna 16 has multiple antennas. Moreover, the radar apparatus 1 has a MIMO (Multiple Input Multiple Output) structure, and the phase is corrected during angle calculation; therefore, the angle caused by electromagnetic noise sometimes becomes related to the frequency F. sb＿θ =0 corresponds to a value near the correction value.

[0266] In these cases, instead of determining whether the absolute value of the incident angle θ is below the first threshold Th1, the determination unit 25 can also determine whether the absolute value of the incident angle θ is related to the frequency F. sb＿θ The correction value corresponding to 0 is below.

[0267] Implementation method 2.

[0268] In Embodiment 2, the radar signal processing apparatus 22 is described as follows: the determination unit 27 is based on the average value v of M relative velocities v. ave The transmission time interval ΔT and differential ΔR of the radar signal group required for one range and velocity calculation by the range and velocity calculation unit 23. MThe absolute value of |ΔR M |, to determine whether the observed object is a non-detected object caused by electromagnetic noise.

[0269] Figure 16 This is a structural diagram showing the radar device 1 including the radar signal processing apparatus 22 of Embodiment 2. Figure 16 In, with Figure 2 The same labels indicate the same or equivalent parts, so the description is omitted.

[0270] The hardware of the radar signal processing device 22 in Embodiment 2 is the same as that of the radar signal processing device 22 in Embodiment 1. Figure 3 This is a hardware structure diagram showing the hardware of the radar signal processing device 22 in Embodiment 2.

[0271] exist Figure 16 In the radar signal processing device 22 shown, the number of times the distance R is calculated by the distance velocity calculation unit 23 and the number of times the relative velocity v is calculated by the distance velocity calculation unit 23 are M (M is an integer greater than or equal to 2).

[0272] For example, the determination unit 27 is composed of Figure 3 The determination circuit 33 shown is implemented.

[0273] The determination unit 27 determines whether the observed object is a detection object or a non-detection object caused by electromagnetic noise based on the incident angle θ calculated by the angle calculation unit 24 and the M distances and M relative velocities calculated by the distance and velocity calculation unit 23.

[0274] That is, the determination unit 27 calculates the average value v of the M relative velocities v calculated by the distance-velocity calculation unit 23. ave .

[0275] The determination unit 27 calculates the average value v of the M relative velocities v. ave The transmission time interval ΔT of the radar signal group required for one range and velocity calculation by the range and velocity calculation unit 23 (refer to...) Figure 18 Multiply by (M-1), and a positive constant α less than 1. Figure 18 This is an explanatory diagram showing the transmission time interval ΔT of the radar signal group radiated from radar device 1.

[0276] If the average value v ave The product of the time interval ΔT, (M-1), and the constant α, G, is the difference ΔR. M The absolute value of |ΔR M If the above is true, then the determination unit 27 determines that the observed object is a non-detectable object caused by electromagnetic noise.

[0277] exist Figure 16In this context, it is assumed that the range-velocity calculation unit 23, angle calculation unit 24, determination unit 27, and observation object detection unit 26, which are structural elements of the radar signal processing device 22, are respectively composed of... Figure 3 The dedicated hardware implementation shown is as follows. That is, it is assumed that the radar signal processing device 22 is implemented by a range and velocity calculation circuit 31, an angle calculation circuit 32, a decision circuit 33, and an observed object detection circuit 34.

[0278] The structural elements of the radar signal processing device 22 are not limited to being implemented by dedicated hardware; the radar signal processing device 22 can also be implemented by software, firmware, or a combination of software and firmware.

[0279] When the radar signal processing device 22 is implemented by software or firmware, the program for causing the computer to execute each processing step in the range-velocity calculation unit 23, angle calculation unit 24, determination unit 27, and observed object detection unit 26 is stored in Figure 4 In the memory 42 shown. Then, Figure 4 The processor 41 shown executes the program stored in the memory 42.

[0280] Next, regarding Figure 16 The operation of the radar device 1 shown will be explained. Among them, the determination unit 27 and others... Figure 2 Since the radar device 1 shown is the same, only the operation of the determination unit 27 will be described here.

[0281] Figure 17 This is a flowchart showing the processing steps of the determination unit 27.

[0282] Judgment Department 27 and Figure 2 Similarly, the determination unit 25 shown compares the absolute value of the incident angle θ calculated by the angle calculation unit 24 with the first threshold Th1.

[0283] If the absolute value of the incident angle θ is below the first threshold Th1, the determination unit 27 obtains M distances R and M relative velocities v from the distance velocity calculation processing unit 53 of the distance velocity calculation unit 23. Figure 17 Step ST41).

[0284] Here, for the sake of simplicity, we assume that all M distances R repeatedly calculated by the distance-velocity calculation unit 23 are either the distance between the radar device 1 and the observed object or the false detection distance based on electromagnetic noise.

[0285] Furthermore, assume that all M relative velocities v repeatedly calculated by the distance-velocity calculation unit 23 are the relative velocities between the radar device 1 and the observed object, or the relative velocities caused by electromagnetic noise.

[0286] Next, the decision unit 27 calculates the average value v of the M relative velocities v.ave The average value v is calculated as shown in equation (6) below. ave The transmission time interval ΔT of the radar signal group, (M-1), and a positive constant α less than 1 are multiplied together to calculate G as the result of the multiplication.

[0287] G = v ave ×ΔT×(M-1)×α (6)

[0288] When the observed object is not a noise source, the difference ΔR represents the change in distance. M The absolute value of |ΔR M The distance change is represented by the product of velocity and time; therefore, the change in distance should be taken as the average value of the relative velocity v. ave The value equivalent to the product of the time required to transmit M radar signal groups, ΔT×(M-1).

[0289] On the other hand, when the observed object is a noise source, the distance R is nearly constant; therefore, the change in distance becomes significantly smaller than the average value of the relative velocity v. ave The value is the product of the time ΔT×(M-1) required to transmit M radar signal groups. Therefore, in equation (6), by setting α to an appropriate value less than 1, it is possible to determine whether the observed object is a non-detectable object caused by electromagnetic noise. For example, α = 1 / 2 can be used as the value of α. In addition, it is desirable to set the value of α based on the resolution of distance R, the resolution of relative velocity v, the change of relative velocity v, the deviation of the assumed frequency of electromagnetic noise, etc.

[0290] The decision unit 27 compares the multiplication result G with the difference ΔR. M The absolute value of |ΔR M | Compare.

[0291] If the product result G is the difference ΔR M The absolute value of |ΔR M |Above ( Figure 17 Step ST42: If yes, then the determination unit 27 determines that the observed object is not a detection object and is a noise source. Figure 17 Step ST43).

[0292] If the product result G is less than the difference ΔR M The absolute value of |ΔR M If one or more of the M relative velocities v are below the third threshold Th3, then the determination unit 27 determines that the observed object is the detected object and is not a noise source.

[0293] If the product result G is less than the difference ΔR M The absolute value of |ΔR MIf all M relative velocities v are greater than the third threshold Th3, then the determination unit 27 determines that the observed object is not a detected object and is a noise source.

[0294] In the above implementation method 2, Figure 16 The radar signal processing device 22 shown is configured such that if the product of the average value of M relative velocities calculated by the range-velocity calculation unit 23, the time interval of the radar signals radiated from the radar device 1, (M-1), and a positive constant less than 1 is greater than or equal to the absolute value of the difference between the distance calculated by the range-velocity calculation unit 23 in the first calculation and the distance calculated in the Mth calculation, then the determination unit 27 determines that the observed object is a non-detectable object caused by electromagnetic noise. Therefore, Figure 16 The radar signal processing device 22 shown is Figure 2 Similarly, the radar signal processing device 22 shown can prevent false detection of non-detectable objects caused by electromagnetic noise as long as the radar signal contains at least one of a transmitted wave whose frequency increases over time and a transmitted wave whose frequency decreases over time.

[0295] Furthermore, this disclosure allows for free combination of various embodiments or modification of any structural elements in various embodiments, or allows for the omission of any structural elements in various embodiments.

[0296] Industrial availability

[0297] This disclosure relates to a radar signal processing apparatus and a radar signal processing method for calculating the distance from a radar device to an observed object.

[0298] This disclosure is applicable to radar devices equipped with radar signal processing devices, as well as vehicle-mounted devices equipped with radar devices.

[0299] Explanation of reference numerals in the attached figures

[0300] 1 Radar device, 11 Radar signal output unit, 12 Output control unit, 13 Signal source, 14 Distributor, 15 Transceiver unit, 16 Transmitting antenna, 17 Array antenna, 17-1 to 17-N Receiving antenna, 18 Beat signal generation unit, 19 Frequency mixing unit, 19-1 to 19-N Mixer, 20 Filter unit, 20-1 to 20-N Filter processing unit, 21 Analog-to-Digital Converter, 21-1 to 21-N ADC, 22 Radar signal processing device, 23 Range and velocity calculation unit, 24 Angle calculation unit, 25, 27 Decision unit, 26 Observation object detection unit, 31 Range and velocity calculation circuit, 32 Angle calculation circuit, 33 Decision circuit, 34 Observation object detection circuit, 41 Processor, 42 Memory, 51 First spectrum calculation unit, 52 Second spectrum calculation unit, 53 Range and velocity calculation processing unit, 61 Third spectrum calculation unit, 62 Angle calculation processing unit.

Claims

1. A radar signal processing device, characterized in that, The radar signal processing device includes: The range and velocity calculation unit repeatedly acquires a beat signal, which has a differential frequency between the frequency of a radar signal whose frequency changes over time and the frequency of the reflected wave of the radar signal reflected by the observed object. The radar signal includes at least one of a transmitted wave whose frequency increases over time and a transmitted wave whose frequency decreases over time. The range and velocity calculation unit uses the acquired beat signal to repeatedly calculate at least one distance between the radar device and the observed object, and uses the acquired beat signal to repeatedly calculate at least one relative velocity between the radar device and the observed object. An angle calculation unit uses the beat signal obtained by the distance-velocity calculation unit and the configuration spacing of the plurality of receiving antennas included in the array antenna that receives the reflected wave to calculate the incident angle of the reflected wave incident on the array antenna. as well as The determination unit, based on the incident angle calculated by the angle calculation unit and multiple distances and multiple relative velocities calculated by the distance-velocity calculation unit, determines whether the observed object is a detection object or a non-detection object caused by electromagnetic noise. The determination unit performs a determination process based on multiple distances and multiple relative velocities calculated by the distance and velocity calculation unit to determine whether the observed object is a detection object or a non-detection object caused by electromagnetic noise only when the absolute value of the incident angle calculated by the angle calculation unit is below a first threshold corresponding to the resolution of the incident angle. If the absolute value of the incident angle calculated by the angle calculation unit is greater than the first threshold, the determination process is not performed. The first threshold is stored in the internal memory of the determination unit or is provided from outside the radar signal processing device.

2. The radar signal processing device according to claim 1, characterized in that, If the distance calculation unit performs distance calculations M times, the absolute value of the difference between the distance calculated by the distance and velocity calculation unit in the first calculation and the distance calculated in the Mth calculation is below the second threshold, and the absolute values ​​of all relative velocities calculated by the distance and velocity calculation unit are above the third threshold, then the determination unit determines that the observed object is a non-detectable object caused by electromagnetic noise, where M is an integer greater than or equal to 2.

3. The radar signal processing device according to claim 1, characterized in that, If the number of distance calculations and the number of relative velocity calculations performed by the distance-velocity calculation unit are both M, and the average value of the M relative velocities calculated by the distance-velocity calculation unit, the transmission time interval of the radar signal group required for one distance and velocity calculation by the distance-velocity calculation unit, (M-1), and the product of a positive constant less than 1 is greater than or equal to the absolute value of the difference between the distance calculated by the distance-velocity calculation unit for the first time and the distance calculated for the Mth time, then the determination unit determines that the observed object is a non-detectable object caused by electromagnetic noise, where M is an integer greater than or equal to 2.

4. The radar signal processing apparatus according to any one of claims 1 to 3, characterized in that, The radar signal processing device includes an observation object detection unit. When the determination unit determines that the observation object is a detection object, the observation object detection unit outputs the at least one distance and the at least one relative velocity calculated by the distance-velocity calculation unit, and the incident angle calculated by the angle calculation unit as the detection result of the observation object.

5. The radar signal processing apparatus according to claim 4, characterized in that, When the determination unit determines that the observed object is a non-detected object, the object detection unit outputs information indicating that a non-detected object caused by electromagnetic noise has been detected.

6. A radar signal processing method, wherein, The range-velocity calculation unit repeatedly acquires a beat signal, which has a differential frequency between the frequency of a radar signal whose frequency changes over time and the frequency of the reflected wave of the radar signal reflected by the observed object. The radar signal includes at least one of a transmitted wave whose frequency increases over time and a transmitted wave whose frequency decreases over time. The range-velocity calculation unit uses the acquired beat signal to repeatedly calculate at least one distance between the radar device and the observed object, and uses the acquired beat signal to repeatedly calculate at least one relative velocity between the radar device and the observed object. The angle calculation unit uses the beat signal obtained by the distance-velocity calculation unit and the configuration spacing of the multiple receiving antennas included in the array antenna receiving the reflected wave to calculate the incident angle of the reflected wave onto the array antenna. The determination unit determines, based on the incident angle calculated by the angle calculation unit and multiple distances and multiple relative velocities calculated by the distance-velocity calculation unit, whether the observed object is a detection object or a non-detection object caused by electromagnetic noise. The determination unit performs a determination process to determine whether the observed object is a detection object or a non-detection object caused by electromagnetic noise based on multiple distances and multiple relative velocities calculated by the distance and velocity calculation unit if the absolute value of the incident angle calculated by the angle calculation unit is below a first threshold corresponding to the resolution of the incident angle. If the absolute value of the incident angle calculated by the angle calculation unit is greater than the first threshold, the determination process is not performed. The first threshold is stored in the internal memory of the determination unit or is provided from outside the radar signal processing device.

7. A radar device, characterized in that, The radar device includes the radar signal processing apparatus according to any one of claims 1 to 5.

8. A vehicle-mounted device, characterized in that, The vehicle-mounted device includes the radar device as described in claim 7.

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