Radar device

Abstract

A radar device (1) includes a radar signal output section (11), a transceiver section (15), a beat signal generation section (18), and a signal processing section (22). The radar signal output section (11) outputs a first frequency modulation signal in which a frequency varies with a first chirp slope and repeats at a first chirp period, and a second frequency modulation signal in which a frequency varies with a second chirp slope different from the first chirp slope and repeats at the first chirp period. The signal processing section (22) determines a target in the first frequency modulation signal and a target in the second frequency modulation signal as a false target when a beat frequency of the target in the first frequency modulation signal coincides with a beat frequency of the target in the second frequency modulation signal, and a Doppler frequency of the target in the second frequency modulation signal coincides with a Doppler frequency of the target in the second frequency modulation signal.

Description

Technical Field

[0001] This disclosure relates to a radar device for calculating the distance to an object and the relative velocity with respect to the object. Background Technology

[0002] As a radar device for calculating the distance to and relative velocity to an object, there are FMCW (Frequency Modulated Continuous Wave) radar devices that transmit radar signals with a frequency that changes over time. These FMCW radar devices sometimes misdetect external radio waves or electromagnetic noise (hereinafter, electromagnetic noise) outside the radar signal band as false targets. Therefore, to suppress the influence of electromagnetic noise on the radar device, countermeasures based on hardware such as electromagnetic shielding are usually applied. However, this countermeasure not only increases the cost but also increases the overall weight and volume of the radar device.

[0003] To address this, a method for identifying and removing spurious targets generated by electromagnetic noise through radar signal processing, instead of using countermeasure components, has been disclosed. Patent Document 1 discloses a radar device having a first measurement mode that changes the frequency of a transmitted wave at a preset first rate of change, and a second measurement mode that changes the frequency of the transmitted wave at a second rate of change different from the first rate of change. In the radar device disclosed in Patent Document 1, if the peak signal components extracted during operation of the first measurement mode have at least approximately the same frequency as the peak signal components extracted during operation of the second measurement mode, it is determined that electromagnetic noise has been mixed in.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2013-96903 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] In FMCW radar, there is a method called FCM (Fast Chirp Modulation), in which frequency analysis is performed on the beat signal obtained by using radar signals that intermittently and repeatedly output frequency modulation signals, and the range and relative velocity are calculated based on the beat frequency corresponding to the range and the Doppler frequency corresponding to the relative velocity.

[0009] The FCM method has become increasingly popular in recent years due to its advantages in improving the accuracy of recognition relative to speed and its ability to identify targets in multi-target environments. However, if the detection results obtained by transmitting waves based on modulation patterns with different gradients are used to distinguish spurious targets generated by electromagnetic noise, the following problem exists in the FCM method: even if the transmitted waves are modulation patterns with different frequency change rates, the Doppler frequencies of the peak signal components caused by electromagnetic noise are sometimes inconsistent, and it is impossible to determine whether it is a spurious target generated by electromagnetic noise based solely on the consistency of the frequencies.

[0010] This disclosure is intended to solve the above-mentioned problems, and its purpose is to provide a radar device that, without introducing electromagnetic noise countermeasures based on electromagnetic shielding or the like, can perform the determination and removal of dummy targets generated by electromagnetic noise through radar signal processing.

[0011] means for solving problems

[0012] The radar device disclosed herein includes: a radar signal output unit that repeatedly outputs a frequency-modulated signal; a transceiver unit that transmits the frequency-modulated signal toward a target and receives reflected waves from the target; a beat signal generation unit that generates a beat signal having a difference frequency between the frequency of the frequency-modulated signal and the frequency of the reflected wave, and converts the beat signal into digital data; and a signal processing unit that uses the digital data to calculate the beat frequency corresponding to the distance from the target and the Doppler frequency corresponding to the relative velocity with respect to the target, and detects the distance to the target and... Regarding relative velocity, the radar signal output unit outputs a first frequency modulation signal, a second frequency modulation signal, and a third frequency modulation signal. The frequency of the first frequency modulation signal varies with a preset first chirp slope and repeats according to a preset first chirp period. The frequency of the second frequency modulation signal varies with a second chirp slope different from the first chirp slope and repeats according to the first chirp period. The frequency of the third frequency modulation signal varies with the second chirp slope and repeats according to the first chirp period. The frequency modulation signal repeats according to a second chirp period different from the first chirp period. When the relative velocity of the object in the first frequency modulation signal is the same as the relative velocity of the object in the second frequency modulation signal, and the distance of the object in the second frequency modulation signal is the same as the value obtained by multiplying the distance of the object in the first frequency modulation signal by the ratio of the first chirp slope to the second chirp slope, the signal processing unit compares the relative velocity of the object in the first frequency modulation signal with the relative velocity of the object in the second frequency modulation signal. If the object in the second frequency modulation signal is determined to be a spurious object, and among the objects determined to be spurious objects in the first and second frequency modulation signals, if the distance of the object in the second frequency modulation signal is the same as the distance of the object in the third frequency modulation signal, and the relative velocity of the object in the second frequency modulation signal is the same as the relative velocity of the object in the third frequency modulation signal, then the signal processing unit will determine the objects in the first and second frequency modulation signals that were determined to be spurious objects to be genuine objects.

[0013] The effects of the invention

[0014] According to this disclosure, for radar devices using the FCM method, without introducing electromagnetic noise countermeasures based on electromagnetic shielding or the like, it is possible to determine and remove dummy targets generated by electromagnetic noise through radar signal processing. Attached Figure Description

[0015] Figure 1 This is a structural diagram showing the radar device according to Embodiment 1.

[0016] Figure 2 This is a hardware structure diagram showing the hardware of the signal processing unit 22 in the radar device of Embodiment 1.

[0017] Figure 3 This is a hardware structure diagram of a computer when the signal processing unit 22 in the radar device of Embodiment 1 is implemented by software or firmware.

[0018] Figure 4 This is a structural diagram showing an example of the distance and speed calculation unit 23.

[0019] Figure 5 This is a flowchart showing the processing steps of the distance-velocity calculation unit 23.

[0020] Figure 6 This is an explanatory diagram showing the signal processing of the distance and velocity calculation unit 23 in the absence of electromagnetic noise.

[0021] Figure 7 This is an explanatory diagram showing the signal processing of the distance and velocity calculation unit 23 in the presence of electromagnetic noise.

[0022] Figure 8 This is a schematic diagram showing the relationship between the waveform of electromagnetic noise input to ADC21 and the waveform of electromagnetic noise input to distance and velocity calculation unit 23.

[0023] Figure 9 This is a flowchart illustrating the processing steps of the signal processing unit 22 in Embodiment 1.

[0024] Figure 10 This is a graph showing the radar signals used in the first and second measurement modes of Embodiment 1.

[0025] Figure 11 This is an explanatory diagram showing the distance-velocity calculation results when the chirp periods are the same in the first and second measurement modes.

[0026] Figure 12 This is an explanatory diagram showing the distance-velocity calculation results under different chirp periods in the first and second measurement modes.

[0027] Figure 13 This is a flowchart illustrating the processing steps of the signal processing unit 22 in Embodiment 2.

[0028] Figure 14 This is a graph showing the radar signals used in the first and second measurement modes of Embodiment 2.

[0029] Figure 15 This is a graph showing the radar signals used in the first measurement mode, the second measurement mode, and the third measurement mode of Embodiment 3.

[0030] Figure 16This is a flowchart illustrating the processing steps of the signal processing unit 22 in Embodiment 3.

[0031] Figure 17 This is a flowchart of the process for determining spurious targets generated by electromagnetic noise in Implementation Method 3.

[0032] Figure 18 This is an explanatory diagram showing the distance and velocity calculation processes for the second and third measurement modes of Embodiment 3.

[0033] Figure 19 This is a diagram showing the radar signals used in the first measurement mode, the second measurement mode, the third measurement mode, and the fourth measurement mode of the radar device in Embodiment 4.

[0034] Figure 20 This is a flowchart illustrating the processing steps of the signal processing unit 22 in Embodiment 4.

[0035] Figure 21 This is a flowchart of the process for determining spurious targets generated by electromagnetic noise in Implementation 4.

[0036] Figure 22 This is an explanatory diagram showing the distance and velocity calculation processes for the second and third measurement modes of Embodiment 4.

[0037] Figure 23 This is an explanatory diagram showing the distance and velocity calculation processes for the first and fourth measurement modes of Embodiment 4.

[0038] Figure 24 This is a flowchart illustrating the processing steps of the signal processing unit 22 in Embodiment 5.

[0039] Figure 25 This is a flowchart of the process for determining spurious targets generated by electromagnetic noise in Implementation 5.

[0040] Figure 26 This is a Venn diagram showing the conditions under which the spurious object can be correctly determined in Embodiment 1 and Embodiment 2.

[0041] Figure 27 This is a Venn diagram showing the conditions under which a spurious object can be correctly determined in Implementation 3.

[0042] Figure 28 This is a Venn diagram showing the conditions under which the spurious object can be correctly determined in embodiments 4 and 5. Detailed Implementation

[0043] Implementation method 1.

[0044] Figure 1 A structural diagram of the radar device according to this embodiment is shown.

[0045] exist Figure 1 In this system, radar device 1 consists of radar signal output unit 11, transceiver unit 15, beat signal generation unit 18, and signal processing unit 22.

[0046] The radar signal output unit 11 includes an output control unit 12, a signal source 13, and a distributor 14.

[0047] The output control unit 12 outputs the modulation command representing the frequency modulation signal and the control signal for output timing to the signal source 13.

[0048] The signal source 13 outputs the frequency modulation signal as a radar signal to the distributor 14 intermittently and repeatedly according to the modulation command and output timing represented by the control signal output from the output control unit 12.

[0049] The distributor 14 divides the radar signals repeatedly output from the signal source 13 into two. The distributor 14 outputs one of the divided radar signals to the transmitting antenna 16, and outputs the other divided radar signal as a local oscillation signal to the beat signal generation unit 18.

[0050] In this way, the radar signal output unit 11 intermittently and repeatedly outputs the frequency modulation signal, whose frequency changes with the passage of time, to the transceiver unit 15 as a radar signal.

[0051] The transceiver unit 15 is equipped with a transmitting antenna 16 and a receiving antenna 17. It transmits radar signals repeatedly output from the radar signal output unit 11 toward the target and receives each radar signal reflected by the target as reflected waves.

[0052] The transmitting antenna 16 radiates the various radar signals repeatedly output by the radar signal output unit 11 into space.

[0053] After the receiving antenna 17 radiates various radar signals into space from the transmitting antenna 16, it receives the various radar signals reflected by the target as reflected waves and outputs the received signals of the various reflected waves to the beat signal generation unit 18.

[0054] In addition, in this embodiment, the transceiver unit 15 that is directly connected to the transmitter antenna 16 and the distributor 14 is described, but this is only one example. It is also possible that an amplifier is connected between the distributor 14 and the transmitter antenna 16, and the amplifier amplifies the radar signal output from the distributor 14 and outputs the amplified radar signal to the transmitter antenna 16.

[0055] Furthermore, the transceiver unit 15, which is directly connected to the receiving antenna 17 and the frequency mixing unit 19, has also been described. However, this is only one example. Alternatively, an amplifier may be connected between the receiving antenna 17 and the frequency mixing unit 19. The amplifier amplifies the received signal output from the receiving antenna 17 and outputs the amplified received signal to the frequency mixing unit 19.

[0056] The beat signal generation unit 18 includes a frequency mixing unit 19, a filter unit 20, and an ADC (Analog to Digital Converter) 21.

[0057] The frequency mixing unit 19 generates a beat signal having a difference frequency between the frequency of the local oscillation signal output from the distributor 14 and the frequency of the received signal output from the receiving antenna 17 by mixing the local oscillation signal output from the distributor 14 with the received signal output from the receiving antenna 17, and outputs it to the filter unit 20.

[0058] The filter section 20 is implemented by an LPF (Low Pass Filter) or BPF (Band Pass Filter), etc., to suppress unwanted components such as spurious signals contained in the beat signal output from the frequency mixing section 19, and outputs the beat signal after suppressing unwanted components to the ADC 21.

[0059] The ADC21 converts the beat signal output from the filter section 20 into digital data and outputs the digital data to the signal processing section 22.

[0060] The signal processing unit 22 includes a distance and speed calculation unit 23, a determination unit 24, and a target detection unit 25.

[0061] The distance-velocity calculation unit 23 uses multiple digital data output from the ADC 21 of the beat signal generation unit 18 to calculate the beat frequency and Doppler frequency respectively, and further calculates the distance to the target and the relative velocity with respect to the target respectively.

[0062] The distance and velocity calculation unit 23 outputs the calculated values ​​of beat frequency, Doppler frequency, distance, and relative velocity to the determination unit 24.

[0063] Figure 4 An example of the distance and speed calculation unit 23 is shown.

[0064] exist Figure 4 In the diagram, 51 is the first spectrum calculation unit, 52 is the second spectrum calculation unit, and 53 is the distance and velocity calculation and processing unit.

[0065] The first spectrum calculation unit 51 repeatedly acquires digital data output from the ADC 21 in time with the output represented by the control signal output from the output control unit 12, performs Fourier transform on each digital data in the distance direction, and thereby repeatedly calculates the first spectrum.

[0066] Furthermore, the first spectrum calculation unit 51 outputs the repeatedly calculated first spectra to the second spectrum calculation unit 52.

[0067] The second spectrum calculation unit 52 repeatedly obtains K (K is an integer greater than 2) first spectra from the first spectrum calculation unit 51.

[0068] The second spectrum calculation unit 52 performs a Fourier transform on the K first spectra in the Doppler direction each time it acquires K first spectra, thereby calculating the second spectrum and outputting it to the distance and velocity calculation processing unit 53.

[0069] In addition, the second spectrum calculation unit 52 accumulates K first spectra and outputs the accumulated first spectra to the distance and velocity calculation processing unit 53.

[0070] The distance-velocity calculation processing unit 53 detects the frequency corresponding to the peak value of the first spectrum after accumulation output from the second spectrum calculation unit 52, i.e., the beat frequency, and calculates the distance to the target.

[0071] The distance-velocity calculation and processing unit 53 detects the frequency corresponding to the peak value of the second spectrum output from the second spectrum calculation unit 52, which is the Doppler frequency.

[0072] In addition, the distance-velocity calculation and processing unit 53 calculates the relative velocity to the target based on the detected Doppler frequency.

[0073] Finally, the distance and velocity calculation processing unit 53 outputs the calculated distance to the target and the relative velocity with the target to the determination unit 24.

[0074] The determination unit 24 determines whether the target is caused by electromagnetic noise with a fixed frequency based on the beat frequency calculated by the distance and velocity calculation unit 23 and the Doppler frequency calculated by the distance and velocity calculation unit 23.

[0075] Furthermore, electromagnetic noise with a fixed frequency is not limited to electromagnetic noise with a completely unchanged frequency, but also includes electromagnetic noise with a minute frequency variation within a range that is not practically problematic, such as electromagnetic waves assumed to be continuous waves (CW).

[0076] If the determination unit 24 determines that the object is not caused by electromagnetic noise, it outputs the distance and relative speed calculated by the distance and speed calculation unit 23 to the object detection unit 25.

[0077] The object detection unit 25 acquires the distance and relative speed output from the judgment unit 24.

[0078] The target detection unit 25 outputs the acquired distance and relative velocity as the target detection results to the outside of the radar device 1.

[0079] In this embodiment, it is assumed that the distance and velocity calculation unit 23, the determination unit 24, and the target detection unit 25, which are structural elements of the signal processing unit 22, are respectively composed of... Figure 2 The dedicated hardware implementation shown is assumed to be implemented by a distance-velocity calculation circuit 31, a decision circuit 32, and a target detection circuit 33.

[0080] Here, the distance and speed calculation circuit 31, the determination circuit 32, and the object detection circuit 33 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.

[0081] The structural elements of the signal processing unit 22 are not limited to being implemented by dedicated hardware; the signal processing unit 22 can also be implemented by software, firmware, or a combination of software and firmware.

[0082] Software or firmware is stored in the computer's memory in the form of a program. A computer refers to the 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).

[0083] Figure 3 This is a hardware structure diagram of a computer in the case where the signal processing unit 22 is implemented by software or firmware.

[0084] When the signal processing unit 22 is implemented by software or firmware, a program for causing the computer to execute the processing steps of the distance and speed calculation unit 23, the determination unit 24, and the target detection unit 25 is stored in the memory 41. Furthermore, the computer's processor 42 executes the program stored in the memory 41.

[0085] In addition, Figure 2 The diagram shows an example where the structural elements of the signal processing unit 22 are implemented by dedicated hardware. Figure 3The diagram shows an example where the signal processing unit 22 is implemented by software or firmware. However, this is just one example; it is also possible that some structural elements of the signal processing unit 22 are implemented by dedicated hardware, while the remaining structural elements are implemented by software or firmware.

[0086] Next, the operation of the radar device 1 in this embodiment and the generation of dummy targets based on electromagnetic noise will be explained. Furthermore, in this embodiment, dummy targets generated by inputting electromagnetic noise into the ADC 21 will be explained.

[0087] Figure 6 This is an explanatory diagram showing the signal processing of the radar signal, received signal, beat signal, and range and speed calculation unit 23 in a single operating mode. Figure 7 This is an explanatory diagram illustrating the signal processing of the radar signal, received signal, beat signal, and range / velocity calculation unit 23 when electromagnetic noise is input to the ADC21 in a single operating mode. Figure 6 and Figure 7 In, Tx(1), Tx(2), Tx(3), Tx(K) represents the radar signal, Rx(1), Rx(2), Rx(3) Rx(K) represents the received signal.

[0088] Radar signal Tx(k) (k=1, Tx(k) is a frequency-modulated signal whose frequency changes over time. Ts is the scan time of the radar signal Tx(k), which is on the order of microseconds. BW is the bandwidth of the radar signal Tx(k). The time rate of change of the radar signal frequency (chirp slope) S is represented by BW / Ts.

[0089] The output control unit 12 outputs the 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.

[0090] like Figure 6 and Figure 7 As shown, the output timing of the radar signal Tx(k) is a time interval (chirp period T) that is longer than the scan time Ts.

[0091] 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.

[0092] Each time the distributor 14 receives a radar signal Tx(k) from the signal source 13, it distributes the radar signal Tx(k) into two.

[0093] 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 frequency mixing unit 19.

[0094] 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.

[0095] After the receiving antenna 17 radiates the radar signal Tx(k) into space from the transmitting antenna 16, it receives the radar signal Tx(k) reflected by the target as a reflected wave and outputs the received signal Rx(k) of the reflected wave to the frequency mixing unit 19.

[0096] The frequency mixing unit 19 mixes the local oscillation signal Lo(k) with the received signal Rx(k) each time it receives the local oscillation signal Lo(k) from the distributor 14 and the received signal Rx(k) from the receiving antenna 17.

[0097] The frequency mixing unit 19 generates a beat signal having a difference 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) and the received signal Rx(k). Then, the frequency mixing unit 19 outputs the generated beat signal to the filter unit 20 each time it generates the beat signal.

[0098] Each time the filter unit 20 receives a beat signal from the frequency mixing unit 19, 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. Each time the ADC 21 receives a beat signal from the filter unit 20, it converts the beat signal into digital data and outputs the digital data to the distance and speed calculation unit 23. At this time, when electromagnetic noise is input to the ADC 21, such as... Figure 7 As shown, electromagnetic noise sometimes overlaps with the beat signal (overlap of electromagnetic noise). In addition, the operation period of ADC21 (ADC operation timing) corresponds to the period during which the frequency mixing unit 19 outputs the beat signal to the filter unit 20.

[0099] The distance-velocity calculation unit 23 uses multiple digital data repeatedly output from the ADC 21 to calculate the distance to the target and the relative velocity with the target. Then, the distance-velocity calculation unit 23 outputs the calculated distance and relative velocity to the determination unit 24.

[0100] use Figure 5 The flowchart explains the processing steps of the distance and velocity calculation unit 23.

[0101] In step ST11, the first spectrum calculation unit 51 synchronously acquires digital data output from the ADC21 during the period when the local oscillation signal Lo(k) is output from the distributor 14, in accordance with the output timing represented by the control signal output from the output control unit 12.

[0102] The first spectrum calculation unit 51 performs a Fourier transform on the digital data in the distance direction each time it acquires digital data from the ADC 21, thereby calculating the first spectrum.

[0103] This step ST11 is in Figure 6 and Figure 7 The part shown in the middle is "FFT(ST11)", which represents the high-speed Fourier transform (FFT) in the distance direction performed by the first spectrum calculation unit 51.

[0104] By performing a Fourier transform on the digital data in the distance direction, the received signal Rx(k) (k=1, ...) of the reflected wave from the target is transformed. The spectral values ​​of K are accumulated to the beat frequency F shown in the following equation (1). sb＿r .

[0105]

[0106] In equation (1), R is from Figure 1 The distance from radar device 1 to the target shown is c, where c is the speed of light.

[0107] Similarly, the spectral values ​​caused by electromagnetic noise are accumulated to the frequency F of the electromagnetic noise. n＿r When the frequency of electromagnetic noise is fixed, the spectral value of electromagnetic noise has a fixed value that does not depend on the chirp slope S.

[0108] Each time the first spectrum calculation unit 51 calculates K first spectra, it outputs K first spectra to the second spectrum calculation unit 52.

[0109] In step ST12, the second spectrum calculation unit 52 repeatedly obtains K first spectra from the first spectrum calculation unit 51.

[0110] The second spectrum calculation unit 52 performs a Fourier transform on the K first spectra in the Doppler direction each time it acquires K first spectra, thereby calculating the second spectrum.

[0111] This step ST12 is in Figure 6 and Figure 7 The part marked "FFT (ST12)" indicates the Fourier transform in the Doppler direction performed by the second spectrum calculation unit 52. By performing a Fourier transform on the K first spectra in the Doppler direction, the spectral values ​​of the received signal Rx(k) of the reflected wave from the target are accumulated together with... Figure 1The Doppler frequency F, corresponding to the relative velocity between the radar device 1 and the target, is given by the following equation (2). sb＿v .

[0112]

[0113] In equation (2), f is the center frequency of the local oscillation signal Lo(k), and v is... Figure 1 The relative velocity between radar device 1 and the target shown.

[0114] Furthermore, by performing a Fourier transform on the K first-order spectra in the Doppler direction, the spectral values ​​caused by electromagnetic noise are accumulated to the Doppler frequency F corresponding to the spurious targets generated by electromagnetic noise. n＿v .

[0115] Figure 8 A schematic diagram showing the relationship between the waveform of electromagnetic noise input to ADC21 and the waveform of electromagnetic noise input to distance and velocity calculation unit 23.

[0116] The electromagnetic noise input to ADC21 is input to the distance and velocity calculation unit 23 as a waveform captured during the operation timing of ADC21.

[0117] Figure 8 The upper part of the graph shows multiple digital data repeatedly output from the ADC21 and input to the distance and velocity calculation unit 23 (the horizontal axis is time and the vertical axis is frequency). Figure 8 The lower half of the graph shows the electromagnetic noise input to the ADC21 (horizontal axis is time, vertical axis is amplitude).

[0118] The waveform of electromagnetic noise is composed of Figure 8 The lower half of the chart is represented by a solid line. The dashed line in the middle represents the portion outside the ADC's operating timing; therefore, the distance and speed calculation unit 23 does not receive electromagnetic noise.

[0119] If the frequency of the electromagnetic noise is fixed, the K waveforms of the electromagnetic noise captured during the timing of the ADC21 operation will have a phase difference determined by the repetition period (chirp period) T of the radar signal and the frequency of the electromagnetic noise.

[0120] Therefore, the K first spectra calculated based on the electromagnetic noise input to the ADC21 each have a phase difference relative to their adjacent first spectra, which is determined by the chirp period and the frequency of the electromagnetic noise.

[0121] The Fourier transform in the Doppler direction corresponds to finding the phase difference between the K first-order frequencies. Therefore, the Doppler frequency F corresponding to the relative velocity of the spurious target generated by electromagnetic noise is... n＿v It is accumulated to a value determined by the frequency and chirp period T of the electromagnetic noise.

[0122] Therefore, if the frequency of electromagnetic noise is fixed, the Doppler frequency corresponding to the pseudo-object generated by electromagnetic noise can be uniquely determined by the chirp period T alone.

[0123] The second spectrum calculation unit 52 outputs the second spectrum to the distance and velocity calculation processing unit 53 each time it calculates the second spectrum.

[0124] In addition, the second spectrum calculation unit 52 accumulates K first spectra and outputs the accumulated first spectra to the distance and velocity calculation processing unit 53.

[0125] In step ST13, the distance-velocity calculation and processing unit 53 arranges the first spectrum and the second spectrum accumulated by the second spectrum calculation unit 52 into a two-dimensional spectrum and extracts the peak values ​​in the two-dimensional spectrum.

[0126] Then, the distance-velocity calculation processing unit 53 detects the beat frequency F corresponding to the peak value in the first spectrum. sb＿r And the Doppler frequency F corresponding to the peak in the second spectrum sb＿v .

[0127] Specifically, the range-velocity calculation and processing unit 53 compares multiple spectral values ​​contained in the two-dimensional spectrum composed of the first spectrum and the second spectrum with a peak detection threshold Th, and detects the spectral values ​​among the multiple spectral values ​​that are larger than the threshold Th as peak values. The peak detection threshold Th can be stored in the internal memory of the range-velocity calculation and processing unit 53, or it can be provided from outside the radar device 1.

[0128] The peak value detected in step ST13 is Figure 6 and Figure 7 The middle part is the location shown in the distance and velocity calculation results (ST13). Additionally, Figure 6 In the absence of electromagnetic noise, only the peak value of the object is indicated by a circular marker. Figure 7 The image not only shows the peak value of the target, but also uses triangular markers to show the peak value of the electromagnetic noise.

[0129] Furthermore, in this embodiment, beat frequency and Doppler frequency are used in the determination of spurious targets generated by electromagnetic noise. Therefore, in Figure 6 and Figure 7 In ST13, the vertical axis is set to the distance BIN corresponding to the beat frequency and the horizontal axis is set to the relative velocity BIN corresponding to the Doppler frequency, showing the results of the detected peak.

[0130] In the absence of electromagnetic noise input to ADC21, the peak detected by the distance-velocity calculation and processing unit 53 corresponds to the beat frequency F of the real target. sb＿r and Doppler frequency F sb＿v ( Figure 6(ST13), but when electromagnetic noise is input to ADC21, the peak detected by the distance and velocity calculation processing unit 53 includes the frequency F of the electromagnetic noise. n＿r and the Doppler frequency F corresponding to the spurious object generated by electromagnetic noise n＿v The corresponding peak ( Figure 7 (ST13).

[0131] Distance and velocity calculation processing unit 53 detects beat frequency F sb＿r At that time, the shooting frequency F sb＿r Substituting into the following equation (3), calculate from Figure 2 The distance R from the radar device 1 to the target shown.

[0132]

[0133] The distance and velocity calculation processing unit 53 detects the Doppler frequency F sb＿v At that time, the Doppler frequency F sb＿v Substitute into the following equation (4) to calculate. Figure 1 The relative velocity v between the radar device 1 and the target shown.

[0134]

[0135] When the distance and velocity calculation processing unit 53 calculates the distance R and relative velocity v respectively, it outputs the distance R and relative velocity v, as well as the beat frequency and Doppler frequency corresponding to them, to the determination unit 24.

[0136] Without processing to identify spurious targets caused by electromagnetic noise, the beat frequency F of genuine targets is not distinguished. sb＿r and the frequency F of electromagnetic noise n＿r And the Doppler frequency F of the real object sb＿v and the Doppler frequency F corresponding to the spurious object generated by electromagnetic noise n＿v Therefore, when electromagnetic noise is input to the ADC21, the output is a pseudo-object that has the ability to reflect the frequency F of the electromagnetic noise. n＿r Substituting the beat frequency F into equation (3) sb＿r The obtained distance value R, and the Doppler frequency F corresponding to the pseudo-object generated by electromagnetic noise, are... n＿v The relative velocity value v is obtained by substituting it into equation (4).

[0137] Next, use Figure 9 The flowchart shown illustrates the process for identifying and handling spurious targets generated by electromagnetic noise.

[0138] In this embodiment, radar signals of two measurement modes with different chirp slopes and the same chirp period are periodically transmitted and received alternately, and the spurious targets generated by electromagnetic noise are determined by comparing the signal processing results in each measurement mode.

[0139] Figure 10 These are radar signals from the two measurement modes used in this embodiment. Figure 10 In this measurement mode, the absolute value of the chirp slope S1 is larger than the absolute value of the chirp slope S2 in the second measurement mode, and the chirp periods of the first and second measurement modes have the same value T. A larger absolute value of the chirp slope results in higher range resolution; therefore, the first measurement mode is assigned to short-range measurement, and the second measurement mode is assigned to long-range measurement. The radar signal used in the first measurement mode is called the first frequency modulation signal, and the radar signal used in the second measurement mode is called the second frequency modulation signal.

[0140] Return to Figure 9 In step ST21, the signal processing unit 22 obtains digital data of the beat signal in the first measurement mode from the beat signal generation unit 18.

[0141] Next, in step ST22, the distance and velocity calculation unit 23 performs distance and velocity information calculation processing on the digital data obtained in the first measurement mode and stores the calculation results in the memory.

[0142] After the signal processing for the first measurement mode is completed, in step ST23, the signal processing unit 22 obtains the digital data of the beat signal in the second measurement mode from the beat signal generation unit 18.

[0143] Next, in ST24, the distance and speed calculation unit 23 performs distance and speed information calculation processing on the digital data obtained in the second measurement mode and stores the calculation results in the memory.

[0144] After signal processing for the second measurement mode is completed, in step ST25, the determination unit 24 retrieves the calculation results for the first and second measurement modes from the memory. Then, the determination unit 24 compares the beat frequency and Doppler frequency corresponding to the peak values ​​in the two-dimensional spectrum of each measurement mode to determine whether the object corresponding to each peak value is a spurious object generated by electromagnetic noise.

[0145] Specifically, in both measurement modes, targets with the same beat frequency and Doppler frequency are identified as spurious targets generated by electromagnetic noise.

[0146] Figure 11The diagram illustrates signal processing and the resulting two-dimensional spectrum in an environment where a real target 1 is located close to the radar device 1, a real target 2 is located at a distance far from the radar device 1, and spurious targets generated by electromagnetic noise coexist. In this figure, the horizontal axis represents the relative velocity BIN corresponding to the Doppler frequency, and the vertical axis represents the distance BIN corresponding to the beat frequency.

[0147] Since real target 1 is located at close range, it is detected in both the first and second measurement modes. However, due to the different chirp slopes in the first and second measurement modes, the distance BIN of real target 1 becomes a different value corresponding to the product of the chirp slope and the distance between radar device 1 and the target in each measurement mode. Furthermore, since real target 2 is located at a long distance, it is outside the detection range of the first measurement mode and is only observed in the second measurement mode.

[0148] On the other hand, since the frequency of electromagnetic noise corresponds to the beat frequency, spurious targets generated by electromagnetic noise have the same distance BIN in both the first and second measurement modes. Furthermore, since the chirp period is the same in both the first and second measurement modes, the Doppler frequency corresponding to the electromagnetic noise becomes the same value, and the relative velocity BIN also has the same value in both modes. That is, in both the first and second measurement modes, the targets that can be identified as corresponding to peaks with consistent distance BIN and relative velocity BIN are spurious targets generated by electromagnetic noise.

[0149] In comparison, Figure 12 The signal processing results are shown when the chirp periods of the first measurement mode and the second measurement mode are different.

[0150] exist Figure 12 In the case shown, regarding the spurious targets generated by electromagnetic noise, since the frequency of the electromagnetic noise corresponding to the beat frequency is the same, the distance BIN becomes the same value. However, the Doppler frequency corresponding to the electromagnetic noise becomes a value determined by the chirp period of each measurement mode and the frequency of the electromagnetic noise. Therefore, it may not be consistent between the two measurement modes.

[0151] That is, when the frequency of electromagnetic noise is unknown, the corresponding relationship of the Doppler frequencies of the spurious objects generated by electromagnetic noise in each measurement mode is also unknown, and it is impossible to specify the criteria for judging spurious objects generated by electromagnetic noise using beat frequency and Doppler frequency.

[0152] Furthermore, if false detections are identified solely based on the consistency of the beat frequency, it is impossible to distinguish the real object 2, which has the same beat frequency as the electromagnetic noise. This could lead to the real object 2 being mistakenly identified as a fake object generated by the electromagnetic noise.

[0153] Therefore, in order to identify spurious objects generated by electromagnetic noise, a measurement mode with the same chirp period must be used.

[0154] In step ST26, the determination unit 24 determines whether there is a spurious object generated by electromagnetic noise as the result of the determination process for spurious objects generated by electromagnetic noise. If there is no spurious object generated by electromagnetic noise, in step ST28, the object detection unit 25 generates and outputs object information using the signal processing results in the first measurement mode and the signal processing results in the second measurement mode.

[0155] Furthermore, if it is determined in step ST26 that there is a spurious object generated by electromagnetic noise, in step ST27, the information corresponding to the spurious object generated by electromagnetic noise is removed from the signal processing results of the first measurement mode and the second measurement mode. Then, in step ST28, the object detection unit 25 generates and outputs the object information.

[0156] Alternatively, in the processing of spurious objects generated by electromagnetic noise in step ST27, instead of removing the information corresponding to the spurious objects generated by electromagnetic noise, information such as low reliability can be assigned to objects determined to be spurious objects generated by electromagnetic noise.

[0157] Alternatively, if it is determined that there is a spurious object caused by electromagnetic noise, the object detection unit 25 may also output the information that electromagnetic noise is mixed in to the outside of the radar device 1.

[0158] As described above, in this embodiment, the radar device is configured to include a determination unit 24, which periodically and alternately transmits and receives radar signals of two measurement modes with different chirp slopes and the same chirp period, and in the signal processing results of each measurement mode, determines the target pair corresponding to the peak with the same beat frequency and Doppler frequency as a spurious target generated by electromagnetic noise.

[0159] Therefore, in radar devices using the FCM method, the following effect is achieved: without implementing hardware countermeasures such as electromagnetic shielding, it is possible to identify and remove dummy targets generated by electromagnetic noise solely through radar signal processing.

[0160] Implementation method 2.

[0161] In Embodiment 1, a radar device having a determination unit 24 is described, which determines, in the signal processing results of two measurement modes, the target pair corresponding to the peak with the same beat frequency and Doppler frequency as a spurious target generated by electromagnetic noise.

[0162] In this embodiment, a radar device is described in which the distance and relative velocity information output by the distance and velocity calculation unit 23 are used to determine the dummy target generated by electromagnetic noise in the determination unit 24.

[0163] The structural diagram of the radar device in this embodiment is similar to... Figure 1 The determination and processing methods for spurious targets generated by electromagnetic noise in the determination unit 24 of the signal processing unit 22 are the same, but different.

[0164] Figure 13 This is a flowchart illustrating the processing steps of the signal processing unit 22 of the radar device in this embodiment.

[0165] In addition, Figure 13 In, with Figure 9 The same labels indicate the same or equivalent parts, so the description is omitted.

[0166] In step ST85, after the determination unit 24 has completed the signal processing for the second measurement mode, it retrieves the calculation results of the first measurement mode and the second measurement mode from the memory.

[0167] Then, the distance R and relative velocity v corresponding to the peak values ​​in the two-dimensional spectrum of each measurement mode are compared to determine whether the objects corresponding to each peak value are spurious objects generated by electromagnetic noise.

[0168] Specifically, in the two measurement modes, targets with the same relative velocity values ​​are compared. Targets whose distance value R2 in the second measurement mode matches the distance value R1 in the first measurement mode multiplied by the ratio of the first chirp slope to the second chirp slope (S1 / S2) are determined to be spurious targets generated by electromagnetic noise.

[0169] Figure 14 The distance and velocity calculation processes and their results (range Doppler plots) are shown for a first measurement mode (left figure) and a second measurement mode (right figure) in an environment where a real object 1 is located close to the radar device 1, a real object 2 is located far away from the radar device 1, and a mixture of spurious objects generated by electromagnetic noise exists.

[0170] Since real object 1 is located at close range, it is detected in both the first and second measurement modes, and its distance and relative velocity values ​​are the same in both modes. Since real object 2 is located at a long distance, it is outside the detection range of the first measurement mode and is only observed in the second measurement mode.

[0171] Regarding the relative velocity value of the dummy target generated by electromagnetic noise, since the chirping period is the same in both the first and second measurement modes, the Doppler frequency corresponding to the electromagnetic noise becomes the same value, thus having the same value in both the first and second measurement modes.

[0172] On the other hand, the distance value of the dummy target generated by electromagnetic noise becomes the frequency F of the electromagnetic noise. n＿r Substituting the beat frequency F into equation (3) sb＿r The values ​​obtained are therefore different in the first and second measurement modes, which have different chirp slopes.

[0173] At the frequency F of electromagnetic noise n＿r Under fixed conditions, the chirping slope S1 of the first measurement mode and the chirping slope S2 of the second measurement mode are used to express the relationship between the distance value Rn1 of the dummy object generated by electromagnetic noise in the first measurement mode and the distance value Rn2 of the dummy object generated by electromagnetic noise in the second measurement mode according to the following formula (5).

[0174]

[0175] Therefore, in the first and second measurement modes, for objects with the same relative velocity values, objects whose distance values ​​in the second measurement mode are the same as the values ​​obtained by multiplying the distance values ​​of objects in the first measurement mode by S1 / S2 can be identified as spurious objects generated by electromagnetic noise.

[0176] As described above, in this embodiment, the radar device 1 is configured to include a determination unit 24, which periodically and alternately transmits and receives radar signals of two measurement modes with different chirp slopes and the same chirp period. In the signal processing results of each measurement mode, targets with the same relative velocity value are compared. Targets whose distance value of the second measurement mode matches the value obtained by multiplying the distance value of the first measurement mode by the ratio of the first chirp slope to the second chirp slope (S1 / S2) are determined to be spurious targets generated by electromagnetic noise.

[0177] This achieves the following effect: it enables the identification of spurious targets generated by electromagnetic noise using only the calculated distance and relative velocity results from each measurement mode.

[0178] Implementation method 3.

[0179] In Embodiment 2, the case with the first measurement mode and the second measurement mode was described, but in this embodiment, the radar device is described as follows: a third measurement mode is added to prevent misjudgment when different real targets have the relationship between distance and relative speed that accidentally meets the judgment condition of fake targets generated by electromagnetic noise.

[0180] In addition, the signal processing in each measurement mode is the same as in embodiments 1 and 2, so the description is omitted.

[0181] Figure 15 These are the radar signals for each measurement mode in this embodiment. In this embodiment, radar signals for the three measurement modes are periodically and repeatedly transmitted.

[0182] The relationship between the first measurement mode and the second measurement mode is the same as that in implementation methods 1 and 2. In the first measurement mode, the chirp slope is S1 and the chirp period is T1. In the second measurement mode, the chirp slope is S2, which is different from that in the first measurement mode, and the chirp period is T1, which is the same as that in the first measurement mode.

[0183] In the third measurement mode, the chirp slope is the same as S2 in the second measurement mode, and the chirp period is set to T2, which is different from the first and second measurement modes. The radar signal used in this third measurement mode is called the third frequency modulation signal.

[0184] Next, the determination and processing of spurious targets generated by electromagnetic noise in the signal processing unit 22 of this embodiment will be explained.

[0185] Figure 16 This is a flowchart illustrating the processing steps of the signal processing unit 22 of the radar device in this embodiment. Additionally, in Figure 16 In, with Figure 13 The same labels indicate the same or equivalent parts, so the description is omitted.

[0186] In step ST35, the signal processing unit 22 obtains digital data of the beat signal in the third measurement mode from the beat signal generation unit 18.

[0187] In step ST36, the distance and velocity calculation unit 23 performs distance and velocity information calculation on the digital data obtained in the third measurement mode and stores the calculation results in the memory.

[0188] In step ST37, after the determination unit 24 has completed the signal processing for the third measurement mode, it retrieves the calculation results of the first measurement mode, the second measurement mode, and the third measurement mode from the memory.

[0189] Then, the determination unit 24 compares the distance R and relative velocity v corresponding to the peak values ​​in the two-dimensional spectrum of each measurement mode, and determines whether the target corresponding to each peak value is a spurious target generated by electromagnetic noise.

[0190] The processing in step ST37 performed by the determination unit 24 will be explained in detail.

[0191] Figure 17 This is a flowchart of the process for determining spurious targets generated by electromagnetic noise, which is performed in step ST37.

[0192] The method for extracting spurious targets generated by electromagnetic noise is the same as in Implementation Method 2.

[0193] In step ST51, information about a target with consistent relative velocity values ​​is obtained in two measurement modes (the first measurement mode and the second measurement mode).

[0194] In step ST52, it is determined whether there is a target pair whose distance value R2 of the second measurement mode is consistent with the value obtained by multiplying the distance value R1 of the first measurement mode by the ratio of the first chirp slope to the second chirp slope (S1 / S2).

[0195] If all the targets are determined not to be spurious targets generated by electromagnetic noise, the process in step ST37 ends, and the process moves to... Figure 16 Step ST26.

[0196] On the other hand, in step ST53, if there is a pair of targets that satisfy the conditions of step ST52, the target of the second measurement mode in the target pair is extracted, and the information of the target corresponding to the peak in the two-dimensional spectrum of the third measurement mode is obtained.

[0197] Next, in step ST54, based on the information of the target corresponding to the peak in the two-dimensional spectrum of the third measurement mode obtained in step ST53, a comparison is made between the target of the second measurement mode and the target of the third measurement mode that satisfy the conditions of step ST52 to see if the distance value and relative velocity value are consistent.

[0198] Next, for the distance R2 and relative velocity v2 of the object in the second measurement mode, and the distance R3 and relative velocity v3 of the object in the third measurement mode, it is determined whether the object with R2 = R3 and v2 = v3 exists in the signal processing result of the third measurement mode.

[0199] In step ST55, if a target satisfying the condition of ST54 exists in the third measurement mode, the target pair that satisfies the condition of ST54 among the target pairs that were determined to be spurious targets generated by electromagnetic noise in ST52 will be excluded from the list of spurious targets generated by electromagnetic noise, and the remaining pairs will be determined to be spurious targets generated by electromagnetic noise.

[0200] In step ST56, if there are no objects that satisfy the conditions of ST54, all object pairs that satisfy the conditions of ST52 are determined to be pseudo objects generated by electromagnetic noise, and the process ends.

[0201] Figure 18The second measurement mode is shown, which includes a real target 1 located close to the radar device 1, a real target 2 located at a distance from the radar device 1, and a mixture of spurious targets generated by electromagnetic noise in an environment. Figure 18 (left side) and the third measurement mode ( Figure 18 The distance and velocity calculations and their results (distance Doppler plots) are shown on the right side of each plot.

[0202] In both the second and third measurement modes, genuine object 1, genuine object 2, and a spurious object generated by electromagnetic noise were detected.

[0203] For genuine targets, both distance and relative velocity values ​​are consistent across measurement modes. In contrast, for spurious targets generated by electromagnetic noise, only the chirp period differs between the second and third measurement modes, resulting in different accumulated Doppler frequencies. Only the relative velocity value differs between measurement modes. Therefore, for spurious targets identified as generated by electromagnetic noise in ST52, those corresponding to targets with consistent distance and relative velocity values ​​in both the second and third measurement modes are excluded from the list of spurious targets generated by electromagnetic noise. This prevents erroneous identification as spurious targets generated by electromagnetic noise when different genuine targets happen to meet the criteria.

[0204] As described above, in this embodiment, a third measurement mode with the same chirp slope as the second measurement mode but a different chirp period is added to embodiment 2.

[0205] Furthermore, the radar device 1 is configured to include a determination unit 24, which extracts the object of the second measurement mode from the spurious object pair generated by electromagnetic noise determined in the signal processing results of the first measurement mode and the second measurement mode. If an object with the same distance value and relative velocity value exists in the third measurement mode, the object pair of the first and second measurement modes containing that object is excluded from the determination objects of spurious objects generated by electromagnetic noise.

[0206] Therefore, in the first and second measurement modes, it is possible to prevent the erroneous determination that a real object is a fake object generated by electromagnetic noise when different real objects have a relationship between distance and relative velocity that accidentally satisfies the determination condition of a fake object generated by electromagnetic noise.

[0207] Implementation method 4.

[0208] In Embodiment 3, a radar device is described that adds a third measurement mode to the first measurement mode and the second measurement mode to prevent misjudgment when different real targets have a distance-relative velocity relationship that accidentally satisfies the judgment condition of a fake target generated by electromagnetic noise.

[0209] In this embodiment 4, the radar device is described as follows: a fourth measurement mode is added to prevent misjudgment when the real target overlaps with a fake target generated by electromagnetic noise.

[0210] In Implementation 3, there is a remaining situation where misjudgment occurs when a genuine object overlaps with a spurious object generated by electromagnetic noise. Implementation 4 eliminates this situation.

[0211] Furthermore, the signal processing in each measurement mode is the same as in Embodiments 1 and 2, so the explanation is omitted.

[0212] Figure 19 This is a diagram showing the radar signals used in the first measurement mode, second measurement mode, third measurement mode, and fourth measurement mode of the radar device in Embodiment 4. In Embodiment 4, radar signals for the four measurement modes are periodically and repeatedly transmitted.

[0213] The relationship between the first and second measurement modes is the same as in embodiments 1 and 2. In the first measurement mode, the chirp slope is S1 and the chirp period is T1. In the second measurement mode, the chirp slope is S2, which is different from that in the first measurement mode, and the chirp period is T1, which is the same as that in the first measurement mode.

[0214] The third measurement mode is the same as that of Implementation Mode 3, the chirp slope is the same as that of the second measurement mode S2, and the chirp period is different from that of the first and second measurement modes T2.

[0215] In the fourth measurement mode, the chirp slope is the same as S1 in the first measurement mode, and the chirp period is set to T2, the same as in the third measurement mode. The radar signal used in this fourth measurement mode is referred to as the fourth frequency modulation signal.

[0216] Next, the determination and processing of spurious targets generated by electromagnetic noise in the signal processing unit of this embodiment will be explained.

[0217] Figure 20 This is a flowchart illustrating the processing steps of the signal processing unit 22 of the radar device in this embodiment. Additionally, in Figure 20 In, with Figure 16 The same labels indicate the same or equivalent parts, so the description is omitted.

[0218] In step ST47, the signal processing unit 22 obtains digital data of the beat signal in the fourth measurement mode from the beat signal generation unit 18.

[0219] In step ST48, the distance-velocity calculation unit 23 performs distance-velocity information calculation processing on the digital data obtained in the fourth measurement mode, and stores the calculation results in the memory.

[0220] In step ST49, after the determination unit 24 has completed the signal processing for the fourth measurement mode, it retrieves the calculation results of the first measurement mode, the second measurement mode, the third measurement mode and the fourth measurement mode from the memory.

[0221] Then, the determination unit 24 compares the distance R and relative velocity v corresponding to the peak values ​​in the two-dimensional spectrum of each measurement mode, and determines whether the target corresponding to each peak value is a spurious target generated by electromagnetic noise.

[0222] The processing in step ST49 performed by the determination unit 24 is explained in detail.

[0223] Figure 21 This is a flowchart of the process for determining spurious targets generated by electromagnetic noise, performed in step ST49. The method for extracting spurious targets generated by electromagnetic noise is the same as in Embodiment 2. Additionally, in Figure 21 In, with Figure 17 The same labels indicate the same or equivalent parts, so the description is omitted.

[0224] In step ST67, information on spurious targets identified in step ST55 or ST56, as well as targets excluded from the spurious target identification list, is collected. Furthermore, information on targets satisfying the first measurement mode in the target pair of step ST52 is extracted, and information on targets corresponding to peak values ​​in the two-dimensional spectrum of the fourth measurement mode is obtained.

[0225] Next, in step ST68, for the information of the target corresponding to the peak in the two-dimensional spectrum of the fourth measurement mode obtained in step ST67, a comparison is made between the target of the first measurement mode and the target of the fourth measurement mode that satisfy step ST52 to see if the distance value and the relative velocity value are consistent.

[0226] That is, for the distance R1 and relative velocity v1 of the object in the first measurement mode, and the distance R4 and relative velocity v4 of the object in the fourth measurement mode, it is determined whether the object with R1 = R4 and v1 = v4 exists in the signal processing result of the fourth measurement mode.

[0227] In step ST69, if a target satisfying the conditions of step ST68 exists in the fourth measurement mode, the target satisfying the conditions of step ST68 in the first measurement mode that was determined to be a spurious target generated by electromagnetic noise in step ST55 or step ST56 is excluded from the spurious target determination objects, and the process ends.

[0228] In step ST70, if the object that satisfies the condition of step ST68 does not exist in the fourth measurement mode, the objects in the first measurement mode that are excluded from the object judgment objects generated by electromagnetic noise in step ST55 and do not satisfy the condition of step ST68 are re-judged as objects generated by electromagnetic noise, and the process ends.

[0229] Figure 22 The second measurement mode is shown, which includes a real target 1 located close to radar device 1, a real target 2 located at a distance from radar device 1, and a mixture of spurious targets generated by electromagnetic noise in an environment. Figure 22 (left side) and the third measurement mode ( Figure 22 The distance and velocity calculation results (distance Doppler plot) on the right side.

[0230] In both the second and third measurement modes, the true object 1 (circular marker), the true object 2 (circular marker), and the spurious object (triangular marker) generated by electromagnetic noise were detected in the distance Doppler image. Furthermore, in the second measurement mode, the true object 2 and the spurious object generated by electromagnetic noise overlapped.

[0231] For genuine targets, both distance and relative velocity values ​​are consistent across measurement modes. In contrast, for spurious targets generated by electromagnetic noise, only the chirp period differs between measurement modes 2 and 3. Therefore, the Doppler frequencies are accumulated to different values, resulting in different relative velocity values ​​between measurement modes. Consequently, for the genuine target 2 and the spurious target generated by electromagnetic noise overlapping in measurement mode 2, the relative velocity values ​​become different in measurement mode 3.

[0232] In this case, since the true object 2 exists, the condition of step ST54 is met. Therefore, the object of the second measurement mode that satisfies the state of overlap between the true object 2 and the pseudo object generated by electromagnetic noise, and the object of the first measurement mode (the pseudo object generated by electromagnetic noise) that is paired with it, are excluded from the determination objects of the pseudo objects generated by electromagnetic noise in step ST55.

[0233] Figure 23 Showing with Figure 22 The first measurement mode in the same environment ( Figure 23 (left side) and the 4th measurement mode ( Figure 23 The distance-velocity calculation results (distance Doppler plot) are shown on the right side. In both measurement modes 1 and 4, the true target 1 (circular marker) and the spurious target (triangular marker) generated by electromagnetic noise were detected. The range of detectable target distances in measurement modes 1 and 4 is small; therefore, the true target 2, located at a distance, was not detected.

[0234] The first measurement mode contains spurious objects generated by electromagnetic noise and Figure 22 In the second measurement mode, the pairs of spurious targets generated by electromagnetic noise are excluded from the list of spurious targets generated by electromagnetic noise through the processing in step ST55. In the structure of Embodiment 3, which ends with the processing up to step ST55, Figure 22 and Figure 23 Under certain conditions, namely, when the real object overlaps with the spurious object generated by electromagnetic noise in the second measurement mode, the spurious object generated by electromagnetic noise detected in the first measurement mode will be mistakenly identified as the real object.

[0235] Therefore, in Embodiment 4, a re-evaluation is performed in steps after ST67 to determine whether any objects incorrectly identified in the first measurement mode exist. For genuine objects, the distance and relative velocity values ​​are consistent across measurement modes. In contrast, for spurious objects generated by electromagnetic noise, only the chirping period differs between the first and fourth measurement modes, resulting in different accumulated Doppler frequencies and only different relative velocity values ​​across measurement modes. Therefore, even if a spurious object generated by electromagnetic noise is incorrectly identified as a genuine object in the first measurement mode in step ST55 or ST56 due to overlap between a genuine object and a spurious object generated by electromagnetic noise in the first or second measurement mode, a re-evaluation is performed to determine whether an object with the same distance and relative velocity values ​​as the object in the first measurement mode exists in the fourth measurement mode, thereby obtaining a correct determination result.

[0236] As described above, in Embodiment 4, a fourth measurement mode with the same chirp slope as the first measurement mode and the same chirp period as the third measurement mode is added to Embodiment 3. Furthermore, the radar device 1 in Embodiment 4 includes a determination unit 24. If, in the signal processing results of the second and third measurement modes, a target with the same range and relative velocity values ​​is determined to be a spurious target generated by electromagnetic noise, and this target does not exist in the fourth measurement mode, then the determination unit 24 excludes the target of the first measurement mode from the determination of spurious targets generated by electromagnetic noise. If, in the case that a target with the same range and relative velocity values ​​is excluded from the determination of spurious targets generated by electromagnetic noise, and this target does not exist in the fourth measurement mode, then the determination unit 24 re-determines the target of the first measurement mode as a spurious target generated by electromagnetic noise. This prevents the erroneous determination that a spurious target generated by electromagnetic noise is a genuine target when a genuine target overlaps with a spurious target generated by electromagnetic noise.

[0237] Implementation method 5.

[0238] In Embodiment 4, a radar device is described that further adds a fourth measurement mode to the first measurement mode, the second measurement mode, and the third measurement mode, and adds a step of re-judging using the detection results of the first measurement mode and the fourth measurement mode, thereby preventing misjudgment in the case of overlap between a real object and a fake object generated by electromagnetic noise.

[0239] In this embodiment, a radar device is described that prevents misjudgment when the detection results are repeatedly re-judged without using the first measurement mode, the second measurement mode, the third measurement mode, and the fourth measurement mode, in order to prevent the true object from overlapping with the false object generated by electromagnetic noise.

[0240] Furthermore, the signal processing in each measurement mode and the radar signal in each measurement mode are the same as in Implementation Method 4, so the description is omitted.

[0241] The determination and processing of spurious targets generated by electromagnetic noise in the signal processing unit 22 of Embodiment 5 will be described.

[0242] Figure 24 This is a flowchart illustrating the processing steps of the signal processing unit 22 of the radar device in Embodiment 5. Only the spurious object determination processing caused by electromagnetic noise in step ST50 is included. Figure 20 Different. Figure 24 In, with Figure 20 The same labels indicate the same or equivalent parts, so the description is omitted.

[0243] The processing in step ST50 performed by the determination unit 24 will be explained in detail.

[0244] Figure 25 Is Figure 24 The flowchart for the process of identifying spurious targets generated by electromagnetic noise, executed in step ST50. Figure 25 In, with Figure 21 The same labels indicate the same or equivalent parts, so the explanation is omitted. If there is a pair of targets that satisfy the conditions of step ST52, the pair is divided into targets for the first measurement mode and targets for the second measurement mode and processed in parallel.

[0245] First, the determination process for the first measurement mode that meets the conditions of step ST52 will be explained.

[0246] In step ST73, the object of the first measurement mode in the object pair that satisfies the conditions of step ST52 is extracted, and the information of the object corresponding to the peak in the two-dimensional spectrum of the fourth measurement mode is obtained.

[0247] Next, in step ST74, based on the information of the target corresponding to the peak in the two-dimensional spectrum of the fourth measurement mode obtained in step ST73, a comparison is made between the target of the first measurement mode and the target of the fourth measurement mode that satisfy the conditions of step ST52 to see if the distance value and the relative velocity value are consistent.

[0248] That is, for the distance R1 and relative velocity v1 of the object in the first measurement mode, and the distance R4 and relative velocity v4 of the object in the fourth measurement mode, it is determined whether the object with R1 = R4 and v1 = v4 exists in the signal processing result of the fourth measurement mode.

[0249] In step ST75, if a target that satisfies the conditions of step ST74 exists in the fourth measurement mode, the targets in the first measurement mode that satisfy the conditions of step ST74 and are determined to be pseudo targets generated by electromagnetic noise in step ST52 are excluded from the list of pseudo targets generated by electromagnetic noise, and the remaining targets are determined to be pseudo targets generated by electromagnetic noise.

[0250] In step ST76, if there are no objects that satisfy the conditions of step ST74, all objects in the first measurement mode that satisfy the conditions of step ST52 are determined to be spurious objects generated by electromagnetic noise.

[0251] Next, the determination process for the object in the second measurement mode that meets the conditions of step ST52 will be explained.

[0252] In step ST77, the object of the second measurement mode in the object pair that satisfies the conditions of step ST52 is extracted, and the information of the object corresponding to the peak in the two-dimensional spectrum of the third measurement mode is obtained.

[0253] Next, in step ST78, based on the information of the target corresponding to the peak in the two-dimensional spectrum of the fourth measurement mode obtained in step ST77, a comparison is made between the target of the second measurement mode and the target of the third measurement mode that satisfy the conditions of step ST52 to see if the distance value and the relative velocity value are consistent.

[0254] Next, for the distance R2 and relative velocity v2 of the object in the second measurement mode, and the distance R3 and relative velocity v3 of the object in the third measurement mode, it is determined whether the object with R2 = R3 and v2 = v3 exists in the signal processing result of the third measurement mode.

[0255] In step ST79, if a target satisfying the conditions of step ST78 exists in the third measurement mode, the targets in the second measurement mode that satisfy the conditions of step ST78 and are determined to be pseudo targets generated by electromagnetic noise in step ST52 are excluded from the list of pseudo targets generated by electromagnetic noise, and the remaining targets are determined to be pseudo targets generated by electromagnetic noise.

[0256] In step ST80, if there are no objects that meet the conditions of step ST78, all objects in the second measurement mode that meet the conditions of step ST52 are determined to be spurious objects generated by electromagnetic noise.

[0257] In step ST81, it is confirmed whether all targets satisfying the first and second measurement modes of step ST52 have been determined as spurious targets generated by electromagnetic noise. The process ends after the determination is confirmed.

[0258] As described above, in Embodiment 5, a fourth measurement mode with the same chirp slope as the first measurement mode and the same chirp period as the third measurement mode is added, similar to Embodiment 4. Furthermore, the radar device 1 in Embodiment 5 includes a determination unit 24. This determination unit 24 extracts the objects of the first measurement mode from the pair of spurious objects generated by electromagnetic noise determined using the signal processing results of the first and second measurement modes. If an object with both the same distance and relative velocity values ​​exists in the fourth measurement mode, the object of the first measurement mode is excluded from the list of spurious objects generated by electromagnetic noise. Additionally, it extracts the objects of the second measurement mode from the pair of spurious objects generated by electromagnetic noise determined using the signal processing results of the first and second measurement modes. If an object with both the same distance and relative velocity values ​​exists in the third measurement mode, the object of the second measurement mode is excluded from the list of spurious objects generated by electromagnetic noise.

[0259] Therefore, similar to Embodiment 4, it is possible to prevent the erroneous identification of a spurious object generated by electromagnetic noise as a genuine object when a genuine object overlaps with a spurious object generated by electromagnetic noise. Furthermore, since the spurious objects generated by electromagnetic noise in the first measurement mode and the spurious objects generated by electromagnetic noise in the second measurement mode are determined as genuine or false in independent processes, repeated re-determination can be suppressed, and the determination process can be parallelized.

[0260] Finally, the conditions under which the correct determination can be made in each implementation will be explained. Figures 26-28 This is a Venn diagram representing the conditions that can be correctly determined in each implementation. In each diagram, the shaded area of ​​the diagonal line represents the conditions that can be correctly determined.

[0261] Figure 26 This is a Venn diagram showing the conditions under which correct determination can be made in Embodiment 1 and Embodiment 2. A represents the condition that satisfies the determination condition for a spurious object generated by electromagnetic noise, equivalent to step ST52. B represents the condition that two different genuine objects satisfy the determination condition for a spurious object generated by electromagnetic noise, equivalent to step ST52. C represents the condition that a genuine object overlaps with a spurious object generated by electromagnetic noise. According to this diagram, in Embodiment 1 and Embodiment 2, even if condition A is satisfied, correct determination cannot be made under conditions B or C.

[0262] Figure 27 This is a Venn diagram representing the conditions that can be correctly determined in Implementation 3. In Implementation 3, it is possible to correctly determine the condition under condition B again, but under condition C, it is impossible to correctly determine the condition except for the condition B and C (the state where two different true objects satisfying A overlap with the false object).

[0263] Figure 28 This is a Venn diagram representing the conditions that can be correctly determined in Embodiments 4 and 5. In Embodiments 4 and 5, it is further possible to correctly determine all conditions under condition C, and to correctly determine all conditions under which condition A is satisfied.

[0264] Furthermore, it is possible to combine the various embodiments or modify any structural elements of each embodiment, or to omit any structural elements in each embodiment.

[0265] Industrial availability

[0266] The radar device disclosed herein can be used as a radar device in the FCM mode.

[0267] Explanation of reference numerals in the attached figures

[0268] 1 Radar device, 11 Radar signal output unit, 12 Output control unit, 13 Signal source, 14 Distributor, 15 Transceiver unit, 16 Transmitting antenna, 17 Receiving antenna, 18 Beat signal generation unit, 19 Frequency mixing unit, 20 Filter, 21 ADC, 22 Signal processing unit, 23 Range and velocity calculation unit, 24 Decision unit, 25 Object detection unit, 31 Range and velocity calculation circuit, 33 Decision circuit, 34 Object detection circuit, 41 Processor, 42 Memory, 51 First spectrum calculation unit, 52 Second spectrum calculation unit, 53 Third spectrum calculation unit.

Claims

1. A radar device, wherein, The radar device includes: The radar signal output unit repeatedly outputs frequency-modulated signals. The transceiver unit transmits the frequency modulation signal toward the target and receives reflected waves from the target; A beat signal generation unit generates a beat signal having a difference frequency between the frequency of the frequency modulation signal and the frequency of the reflected wave, and converts the beat signal into digital data; and The signal processing unit uses the digital data to calculate the beat frequency corresponding to the distance from the object and the Doppler frequency corresponding to the relative velocity with respect to the object, and detects the distance and relative velocity of the object. The radar signal output unit outputs a first frequency modulation signal, a second frequency modulation signal, and a third frequency modulation signal. The frequency of the first frequency modulation signal varies with a preset first chirp slope and repeats according to a preset first chirp period. The frequency of the second frequency modulation signal varies with a second chirp slope different from the first chirp slope and repeats according to the first chirp period. The frequency of the third frequency modulation signal varies with the second chirp slope and repeats according to a second chirp period different from the first chirp period. If the relative velocity of the object in the first frequency modulation signal is the same as the relative velocity of the object in the second frequency modulation signal, and the distance of the object in the second frequency modulation signal is the same as the value obtained by multiplying the distance of the object in the first frequency modulation signal by the ratio of the first chirp slope to the second chirp slope, then the signal processing unit determines that the object in the first frequency modulation signal and the object in the second frequency modulation signal are spurious objects. If, among the objects identified as spurious objects in the first frequency modulation signal and the second frequency modulation signal, the distance between the object in the second frequency modulation signal and the distance between the object in the third frequency modulation signal are the same, and the relative velocity of the object in the second frequency modulation signal is the same as the relative velocity of the object in the third frequency modulation signal, then the signal processing unit determines the objects in the first frequency modulation signal and the second frequency modulation signal that were identified as spurious objects as genuine objects.

2. The radar device according to claim 1, wherein, The radar signal output unit outputs a fourth frequency modulation signal, the frequency of which varies with the first chirp slope, and the fourth frequency modulation signal repeats with the second chirp period. If, among the objects in the first frequency modulation signal that are determined to be genuine objects, the distance between the objects in the first frequency modulation signal and the distance between the objects in the fourth frequency modulation signal are not the same, and the relative velocity between the objects in the first frequency modulation signal and the relative velocity between the objects in the fourth frequency modulation signal are the same, then the signal processing unit determines the objects in the first frequency modulation signal that are determined to be genuine objects to be fake objects generated by electromagnetic noise. If, among the objects in the first frequency modulation signal that are determined to be spurious objects, the distance of the object in the first frequency modulation signal is the same as the distance of the object in the fourth frequency modulation signal, and the relative velocity of the object in the first frequency modulation signal is the same as the relative velocity of the object in the fourth frequency modulation signal, then the signal processing unit determines the object in the first frequency modulation signal that is determined to be spurious objects to be a genuine object.

3. The radar device according to claim 1, wherein, The radar signal output unit outputs the third frequency modulation signal and the fourth frequency modulation signal. The frequency of the third frequency modulation signal varies with the second chirp slope and repeats according to the second chirp period, which is different from the first chirp period. The frequency of the fourth frequency modulation signal varies with the first chirp slope and repeats according to the second chirp period. Among the objects identified as spurious objects in the first and second frequency modulation signals, if the distance of the object in the first frequency modulation signal is the same as the distance of the object in the fourth frequency modulation signal, and the relative velocity of the object in the first frequency modulation signal is the same as the relative velocity of the object in the fourth frequency modulation signal, then the signal processing unit will determine the object in the first frequency modulation signal that was identified as a spurious object to be a genuine object. If, among the objects identified as spurious objects in the first frequency modulation signal and the second frequency modulation signal, the distance of the object in the second frequency modulation signal is the same as the distance of the object in the third frequency modulation signal, and the relative velocity of the object in the second frequency modulation signal is the same as the relative velocity of the object in the third frequency modulation signal, then the signal processing unit determines the object in the second frequency modulation signal that was identified as a spurious object as a genuine object.

Images