JP2019074424A - Radar device and signal processing method - Google Patents

Abstract

To provide a radar device with which it is possible to improve the accuracy of detecting an actually existing target.SOLUTION: The radar device comprises a transmit unit, a receive unit and a determination unit. The transmit unit transmits a transmit wave of first system for detecting a Doppler shift as a phase change between a plurality of modulating signals and a transmit wave of second system for detecting the Doppler shift as the frequency of a beat signal. The receive unit receives a reflected wave generated as the transmit wave of first system is reflected by a target as a first received signal, and receives a reflected wave generated as the transmit wave of second system is reflected by the target as a second received signal. The determination unit derives, on the basis of the first received signal, an actual target with which a speed difference with the own vehicle almost does not occur and derives, on the basis of the second received signal, an actual target with which a speed difference with the own vehicle does occur, thereby discriminating a real target that is an actually existing target and a periodic noise.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a radar device and a signal processing method for detecting a target.

FMCW (Frequency Modulated Continuous Wave) as a radar device for detecting a target
Radar systems are known. The FMCW radar apparatus transmits a frequency-modulated transmission wave so that the frequency repeats rising and falling, receives a reflection wave from a target for the transmission wave, and transmits the frequency of the transmission wave and the frequency of the reflection wave. Generate a beat signal that is a deviation from the frequency. Then, the radar device performs FFT (Fast Fourier Transform) on the beat signal to obtain a frequency spectrum, detects the maximum peak of the frequency spectrum, and obtains the beat frequency, and the relative distance to the target and the object Calculate the relative velocity of the mark.

  Moreover, there is patent document 1 as a document explaining the technology related to the present invention.

JP, 2014-119353, A

  In the FMCW method, the relative velocity of the target is the frequency fu of the beat signal in the up interval (interval in which the frequency of the transmission wave rises) and the frequency fd of the beat signal in the down interval (the interval in which the frequency of the transmission wave falls). Calculated from the difference. When there is a speed difference between a vehicle equipped with a radar device (hereinafter referred to as the subject vehicle) and a target (for example, when the relative speed is other than 0 km / h and there is a relative speed), the beat frequency fu of the up section and the down section In the case where the beat frequency fd does not match and the speed difference between the vehicle and the target does not substantially occur (for example, when the relative speed is 0 km / h), the beat frequency fu of the up section and the beat frequency fd of the down section are Match Then, when periodic noise is superimposed on the beat signal in a state in which no target actually exists, similar periodic noise is superimposed on the up interval and the down interval, so the beat of the up interval is The frequency fu and the beat frequency fd in the down section coincide with each other. The periodic noise includes, for example, switching noise of a switching power supply that supplies power to the radar device, but is not limited thereto. For example, a noise source unrelated to the operation of the radar device is in the vicinity of the radar device. It may be periodic noise that exists and is output from the noise source.

  Therefore, in the FMCW method, it is only possible to distinguish between an actually existing target causing a speed difference with the host vehicle and an actually existing target and periodic noise in which the speed difference with the host vehicle substantially does not occur. The That is, in the FMCW method, it is not possible to distinguish between an actually existing target and a periodic noise in which a speed difference with the host vehicle does not substantially occur, and a periodic noise causes a speed difference with the host vehicle. There was a risk that it would be misidentified as an actually existing target.

  An object of the present invention is to provide a radar apparatus and a signal processing method capable of improving the detection accuracy of an actually existing target in view of the above-mentioned problems.

  A radar apparatus according to the present invention comprises: a transmission wave of a first system that detects Doppler shift as a phase change among a plurality of modulated signals; and a transmission wave of a second system that detects the Doppler shift as a frequency of a beat signal. A transmitting unit for transmitting, and a reflected wave generated by reflecting the transmission wave of the first system on a target is received as a first reception signal, and a transmission wave of the second mode is reflected on the target Receiver that receives the reflected wave generated as a second reception signal, and a real target, which is a target that actually exists, and periodic noise based on the first reception signal and the second reception signal And a determination unit for determining the second target signal based on the first reception signal, the second identification signal, and the second target signal. Deriving the actual target on which the speed difference with the host vehicle is generated. It is formed (first configuration).

  In the radar device of the first configuration, the determination unit calculates a phase change between the plurality of modulated signals from the first received signal, and the self-determination unit determines the self on the basis of the phase change among the plurality of modulated signals. The above-mentioned actual target that hardly generates a speed difference with a vehicle, the actual target which generates a speed difference with the host vehicle, and the periodic noise are discriminated, and the above-mentioned target does not generate a speed difference with the host vehicle The real target is derived, the frequency of the beat signal is calculated from the second received signal, and the real target and the periodic noise that cause a speed difference with the host vehicle based on the frequency of the beat signal To determine the speed difference with the subject vehicle and derive the real target, and in the determination process based on the phase change among the plurality of modulated signals, the real target with substantially no speed difference with the subject vehicle For the judgment target that was judged to be present, The determination process based on the frequency of the serial beat signal may be configured not executed (second configuration).

  In the radar device of the first configuration, the determination unit calculates the frequency of the beat signal from the second received signal, and the speed difference with the host vehicle is generated based on the frequency of the beat signal. The real target and the periodic noise that cause substantially no speed difference between the real target and the host vehicle are determined, and the real target causing the speed difference with the host vehicle is derived, and the first reception is performed. The phase change between the plurality of modulated signals is calculated from the signal, and based on the phase change among the plurality of modulated signals, the real target and the periodic noise that cause substantially no speed difference with the host vehicle It discriminate | determines and the said real target which a speed difference with the said vehicle does not produce substantially is derived | led-out, and it discriminate | determined that it was the said actual target which the speed difference with the said vehicle produces in the discrimination processing based on the frequency of the said beat signal. For the target, The determination process based on the phase change may be configured not performed (a third configuration) between tone signal.

  In the radar device having any one of the first to third configurations, the first method is a fast-chirp modulation (FCM) method, and an FFT (Fast Fourier Transform) between a plurality of chirp signals in the FCM method. (4) A configuration (fourth configuration) may further be provided, which further includes a period setting unit that makes the lengths of periods during which processing is not performed irregular.

  A signal processing method according to the present invention comprises: a transmission wave of a first system that detects Doppler shift as a phase change among a plurality of modulated signals; and a transmission wave of a second system that detects the Doppler shift as a frequency of a beat signal. Transmitting, and receiving a reflected wave generated by reflecting the transmission wave of the first method on the target as a first received signal, and transmitting the transmission wave of the second mode on the target Receiving the reflected wave generated as a second received signal as a second received signal, and based on the first received signal and the second received signal, a real target which is actually present and a periodic target And a discrimination step of discriminating from noise, wherein the discrimination step derives the actual target with substantially no speed difference with the host vehicle based on the first reception signal, and the second reception signal. The speed difference with the host vehicle is Jill is configured to derive the real target (fifth configuration).

  According to the radar apparatus and the signal processing method according to the present invention, an actually existing target that hardly generates a speed difference with the vehicle and an actually existing target that generates a speed difference with the vehicle, and periodic noise And can be determined, so that the detection accuracy of the actually existing target can be improved.

The figure which shows the structure of the radar apparatus which concerns on 1st Embodiment. Diagram showing frequency modulation applied to transmission signal Flow chart showing the operation of the signal processing device according to the first embodiment Diagram showing the result of Fourier transform processing in the range bin direction Diagram showing the result of Fourier transform processing in the velocity bin direction The figure which shows the other structural example of the radar apparatus which concerns on 2nd Embodiment. Diagram showing frequency modulation applied to transmission signal

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

<1. First embodiment>
<1-1. Configuration of radar device>
FIG. 1 is a view showing the configuration of a radar device 1 according to the present embodiment. The radar device 1 is mounted, for example, on a vehicle such as a car. Hereinafter, a vehicle on which the radar device 1 is mounted is referred to as a "vehicle". In addition, a direction in which the host vehicle travels straight ahead, which is directed from the driver's seat to steering, is referred to as "forward". In addition, a direction in which the host vehicle travels straight and is directed from the steering to the driver's seat is referred to as “rearward”. In addition, a direction perpendicular to the straight traveling direction of the vehicle and the vertical line, that is, a direction from the right to the left of the driver facing the front is referred to as “left direction”. Further, a direction perpendicular to the straight traveling direction of the vehicle and the vertical line, that is, a direction from the left to the right of the driver facing the front is referred to as “right direction”.

  When the radar device 1 is mounted at the front end of the host vehicle, the radar device 1 acquires target data relating to a target present ahead of the host vehicle using a transmission wave.

  The radar device 1 is a distance until the reflected wave reflected from the target is received by the receiving antenna of the radar device 1 (hereinafter referred to as “longitudinal distance”) [m], relative velocity of the target relative to the vehicle [km / H] Target data having parameters such as the distance of the target in the lateral direction of the vehicle (hereinafter referred to as "lateral position") [m] is derived. The vertical position is, for example, a position at which the radar device 1 of the host vehicle is mounted as an origin O, and is represented by a positive value in front of the host vehicle and a negative value behind the host vehicle. The lateral position is represented by, for example, a position at which the radar device 1 of the host vehicle is mounted as an origin O, a positive value on the right side of the host vehicle, and a negative value on the left side of the host vehicle.

  The radar device 1 not only detects the target in the above-described FMCW method, but also detects the target in the FCM (Fast Chirp Modulation) method. Since the FCM method does not require pairing processing of up peak and down peak necessary in the FMCW method, the problem of misrecognition of the target due to mispairing does not occur, and more accurate target detection can be expected. .

  Here, a method of calculating the distance and the relative velocity in the FCM method will be briefly described. In the FCM method, one waveform of a transmission wave whose frequency changes in a sawtooth wave is taken as one chirp, multiple chirps are transmitted with a shorter period compared to the FMCW method, and a reflected wave from a target is received as a received signal. The beat signal is obtained by taking the difference between the reception signal and the transmission wave, and the distance to the target and the relative velocity are obtained by performing two-dimensional FFT on this beat signal. Specifically, the frequency of the beat signal is proportional to the distance since the time delay of the received signal increases with the distance of the target relative to the transmission wave. Therefore, by performing the FFT processing on the beat signal, a peak appears at the position of the frequency corresponding to the distance of the target. Since FFT is used to extract reception level and phase information for each frequency point (hereinafter sometimes referred to as a range bin) set at a predetermined frequency interval, it is possible to use the range bin of the frequency corresponding to the distance of the target exactly A peak appears. Therefore, the distance to the target can be obtained by detecting the peak frequency. The FFT processing for obtaining this distance is repeated for the number of beat signals, ie, the number of chirps, in order to perform for each beat signal.

  Next, in the calculation of relative velocity, in the FCM method, when the relative velocity of the target is not 0 km / h, the Doppler frequency is detected using the fact that the change of the phase according to the Doppler frequency appears between the beat signals. The relative speed is calculated. That is, if there is substantially no speed difference between the host vehicle and the target (for example, when the relative speed is 0 km / h), no Doppler component is generated in the received signal, so the phase of the received signal for each chirp Are all the same. However, if there is a velocity difference with the target (for example, if the relative velocity is other than 0 km / h and there is a relative velocity), the phase change according to the Doppler frequency between the received signals for each chirp Will occur. Since the peak information obtained by subjecting the beat signal to FFT processing includes this phase information, if the peak information of the same target obtained from each beat signal is arranged in time series and the second FFT processing is performed The Doppler frequency is determined from the phase information, and a peak appears at that frequency position. This peak frequency corresponds to the relative velocity.

  Thus, distance and relative velocity can be calculated by performing two-dimensional FFT on the beat signal. Since the FFT processing for obtaining the relative velocity is performed for each range bin for the result of the first FFT processing, it is repeated by the number of range bins.

  As shown in FIG. 1, the radar device 1 mainly includes a transmitter 2, a receiver 3, and a signal processor 4.

  The transmitter 2 includes a signal generator 21 and a transmitter 22. The signal generation unit 21 reduces the voltage at a constant rate as the time passes from the reference value, reaches a minimum value, and then immediately returns to the reference value with a first modulation signal in which a plurality of one waveform (one chirp) continues. , And alternately generate a second modulation signal whose voltage changes in a triangular wave shape, and supplies it to the transmitter 22. The period for two triangular wave voltages may be, for example, 50 msec, and the period of one chirp may be, for example, several tens of microseconds. The transmitter 22 frequency-modulates the continuous wave signal based on the modulation signal generated by the signal generation unit 21, generates a transmission signal whose frequency changes as time passes, and outputs the transmission signal to the transmission antenna 23.

  The transmission antenna 23 outputs the transmission wave TW to the front of the host vehicle based on the transmission signal from the transmitter 22. In the transmission wave TW output from the transmission antenna 23, as shown in FIG. 2, the FCM period in which the frequency is changed by the first modulation signal, the FMCW period in which the frequency is changed by the second modulation signal, and the frequency are constant. A certain frequency fixed period is repeated in order. In the FCM period, a free running time t1 which is a period in which the TFT processing is not performed is provided between the respective chirps. The transmission wave TW transmitted to the front of the host vehicle from the transmission antenna 23 is reflected by an object such as a person or another vehicle to become a reflected wave RW.

  The receiving unit 3 includes a plurality of receiving antennas 31 forming an array antenna, and a plurality of individual receiving units 32 connected to the plurality of receiving antennas 31. In the present embodiment, the receiving unit 3 includes, for example, four receiving antennas 31 and four individual receiving units 32. The four individual reception units 32 correspond to the four reception antennas 31 respectively. Each receiving antenna 31 receives the reflected wave RW from the object and obtains a received signal, and each individual receiving unit 32 processes the received signal obtained by the corresponding receiving antenna 31.

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

  The signal processing device 4 includes a microcomputer including a CPU (Central Processing Unit), a memory 41, and the like. The signal processing device 4 stores various data to be operated on in the memory 41 which is a storage device. The memory 41 is, for example, a random access memory (RAM). The signal processing device 4 includes a transmission control unit 42, a Fourier transform unit 43, and a data processing unit 44 as functions implemented as software by a microcomputer. The transmission control unit 42 controls the signal generation unit 21 of the transmission unit 2.

  The Fourier transform unit 43 performs fast Fourier transform (FFT) on beat signals output from each of the plurality of individual reception units 32. Thereby, the Fourier transform unit 43 transforms the beat signal related to the reception signal of each of the plurality of reception antennas 31 into a frequency spectrum which is data in the frequency domain. The frequency spectrum obtained by the Fourier transform unit 43 is input to the data processing unit 44.

  The data processing unit 44 executes target data acquisition processing, and acquires target data relating to a target in front of the host vehicle based on the frequency spectrum of each of the plurality of receiving antennas 31. Further, the data processing unit 44 outputs the target data to the vehicle control ECU 51 or the like.

  As shown in FIG. 1, the data processing unit 44 has a target data derivation unit 45, a target data processing unit 46, and a target data output unit 47 as main functions.

  The target data derivation unit 45 derives target data concerning the target based on the frequency spectrum obtained by the Fourier transform unit 43. The target data derivation unit 45 includes a determination unit 45a. Details of the process executed by the determination unit 45a will be described later.

  The target data processing unit 46 performs various processing such as filtering on the derived target data. The target data output unit 47 outputs target data to the vehicle control ECU 51 and the like. Thus, the vehicle control ECU 51 or the like can use the target data for, for example, ACC (Adaptive Cruise Control) or PCS (Pre-crash Safety System).

<1-2. Signal processor operation>
Next, the operation of the signal processing device 4 will be described. FIG. 3 is a flowchart showing the operation of the signal processing device 4. The signal processing device 4 periodically repeats the process shown in FIG. 3 at regular intervals.

  The signal processing device 4 acquires a plurality of first beat signals corresponding to one FCM period (step S10). Next, the Fourier transform unit 43 performs a two-dimensional FFT on the first beat signal (step S20).

  By FFT processing the first beat signal, a peak appears at the position of the frequency corresponding to the distance of the target. In the FFT, the reception level and phase information are extracted for each range bin set at a predetermined frequency interval, so that a peak appears in the range bin of the frequency corresponding to the distance of the target. Therefore, the distance to the target can be obtained by detecting the peak frequency. The FFT processing for obtaining this distance is repeated for the number of first beat signals, that is, the number of chirps, in order to perform for each first beat signal. FIG. 4 shows the results of this FFT processing arranged in the range bin direction, and the results of the first beat signals are arranged in the direction orthogonal to the range bins in a matrix, and the values of each processing result in the height direction (Spectrum [dB] It is an example which showed). FIG. 4 shows an example in which two peaks 61 and 62 occur.

  Next, the relative velocity is calculated, but in the FCM method, if the relative velocity of the target is not 0 km / h, Doppler is used to make use of the fact that a change in phase according to the Doppler frequency appears between the first beat signals. The relative velocity is calculated by detecting the frequency. That is, if the relative velocity is 0 km / h, no Doppler component occurs in the received signal, so that the phase of the received signal for each chirp is the same. However, if there is a relative velocity with the target, a phase change corresponding to the Doppler frequency occurs between the received signals for each chirp. Since the peak information obtained by subjecting the first beat signal to FFT processing includes this phase information, the peak information of the same target obtained from each first beat signal is arranged in time series and the second time When the FFT processing of is performed, the Doppler frequency is determined from the phase information, and a peak appears at that frequency position. In this FFT processing, phase information is extracted for each velocity bin set at a predetermined frequency interval according to the velocity resolution, so a peak appears in the velocity bin of the frequency corresponding to the relative velocity of the target. Therefore, the relative velocity with the target can be determined by detecting the peak frequency. FIG. 5 shows the results of the second FFT processing arranged in the velocity bin direction, and the results of the second FFT processing are arranged in the range bin direction for each frequency point of the distance in a matrix, and each processing result in the height direction It is an example which showed a value (Spectrum [dB]). FIG. 5 shows an example in which two peaks 63 and 64 occur.

  Returning to FIG. 3, in step S30 following step S20, the target data derivation unit 45 extracts a peak from the result of the two-dimensional FFT. Furthermore, the target data derivation unit 45 calculates the vertical distance and the relative velocity of the target from the range bin and velocity bin of the peak extracted in step S30 (step S40).

  The target obtained from the peak extraction may not only be a target actually present (hereinafter also referred to as a real target), but also may be periodic noise. Therefore, in the process after step S50, the target obtained from the peak extraction is determined to be a real target or a periodic noise. Moreover, the process of step S50-S140 is implemented separately by each discrimination | determination object.

  In step S50 following step S40, the determination unit 45a determines whether or not there is substantially a speed difference between the determination target and the host vehicle. For example, the determination unit 45a determines whether the relative velocity to be determined is 0 km / h, using the relative velocity calculated in step S40.

  In the FCM method, it is possible to distinguish between a real target that hardly generates a speed difference with the host vehicle, a real target that causes a speed difference with the host vehicle and periodic noise. Therefore, when the speed difference between the determination target and the own vehicle does not substantially occur, the determination unit 45a determines that the determination target is a real target in which the speed difference from the own vehicle does not substantially occur (step S60). After the process of step S60, the process proceeds to step S150 described later.

  Here, in the FCM method, the reason why it is possible to distinguish between a real target with almost no speed difference with the host vehicle, a real target with which the speed difference with the host vehicle is generated, and periodic noise will be described. .

  In the case of the FMCW method, only frequency peaks related to the distance of the target are detected. The relative velocity is detected by the frequency difference. In other words, in the FMCW method, the phase difference is not used in detection of the relative velocity. In this case, in the case of periodic noise, peaks are detected at almost the same frequency (the same BIN) in the FFT results of the up section and the down section.

  On the other hand, in the case of the FCM method, the frequency peak of the distance related to the target is detected, and the relative velocity is detected by the phase difference between the plurality of peaks in the same BIN. Specifically, when the phase difference between the peaks of the same BIN is calculated among the peaks detected for each chirp, the case where the speed difference with the vehicle is substantially not generated (the relative speed is 0 km / h In the case of), there is no phase difference. That is, the beginning of the phase of each chirp will be the same (starting with the same phase). On the other hand, in the case of periodic noise, a phase difference of peaks in the same BIN of each chirp occurs. That is, the beginning of the phase of each chirp is different (starting with a different phase). As described above, it is only a real target that hardly causes a speed difference with the host vehicle that a phase difference of peaks in the same BIN of each chirp does not occur.

  Therefore, in the case of the FMCW method, when the frequency peaks of the up section and the down section to be paired are the same BIN, it is determined whether it is a periodic target or a real target with almost no speed difference with the vehicle. Although it becomes difficult, in the case of a different BIN, it can be determined as a real target that causes a speed difference with the host vehicle. Moreover, in the case of the FCM method, when there is a phase difference of the same BIN peak among a plurality of chirps, it becomes difficult to determine whether it is a periodic target or a real target causing a speed difference with the vehicle. When there is not, it can be judged as a real target that hardly causes a speed difference with the host vehicle.

  Returning to FIG. 3, when it is determined in step S50 that there is a speed difference between the determination target and the vehicle, the signal processing device 4 generates a second beat signal corresponding to one FMCW period. It acquires (step S70). Next, the Fourier transform unit 43 performs FFT on the second beat signal (step S80). In addition, since the receiver 3 outputs the second beat signal corresponding to one FMCW period to the signal processing device 4 immediately after outputting the first beat signal corresponding to one FCM period. After the process of step S10, the processes of step S70 and subsequent steps may be performed in parallel with steps S20 to S50, and a second beat signal corresponding to one FMCW period may be stored in, for example, the memory 41. After the processing of steps S20 to S50 is completed as described above, the processing of step S70 and subsequent steps may be performed. When the processes of step S70 and the subsequent steps are performed after the processes of steps S20 to S50 are performed as illustrated in the flowchart, for example, the first beat signal corresponding to one FCM period is also stored in the memory 41, for example. All of the flow operations shown in FIG. 3 may be performed during a fixed frequency period in FIG.

  In step S90 following step S80, the target data derivation unit 45 extracts peak frequencies for the frequency spectrum obtained by the FFT in step S80 (step S90). The target data deriving unit 45 extracts, as a peak frequency, a frequency at which a peak having a power exceeding a predetermined threshold appears in the frequency spectrum.

  Next, the target data derivation unit 45 associates the section data of the up section with the section data of the down section. The target data derivation unit 45 uses, for example, an operation using the Mahalanobis distance, and has two similar parameters (peak frequency, peak angle which is an angle estimated by azimuth operation processing, and signal power). Section data are associated (step S100).

  The target data derivation unit 45 further derives pair data based on the two interval data, when the two interval data of the up interval and the down interval can be associated with each other. The target data derivation unit 45 uses the parameters of the two section data of the up section and the down section that are the source of the pair data for each of the derived pair data, to obtain the parameters of the pair data (longitudinal distance and relative velocity ) Is derived (step S110).

  In step S120 following step S110, the determination unit 45a determines whether the beat frequency of the up interval to be determined and the beat frequency of the down interval to be determined substantially match.

  As described above, in the FMCW method, it is possible to distinguish between a real target causing a speed difference with the host vehicle and a real target and periodic noise with substantially no speed difference with the host vehicle. Therefore, when the beat frequency of the up interval of the determination target substantially matches the beat frequency of the down interval of the determination target, the determination unit 45a determines that the determination target is noise (step S130). After the process of step S130, the flow operation ends.

  On the other hand, when the beat frequency of the up interval of the determination target and the beat frequency of the down interval of the determination target do not match, the determination unit 45a determines that the determination target is a real target causing a speed difference with the own vehicle. (Step S140). After the process of step S140, the process proceeds to step S150 described later.

  The parameters of the target data obtained by the FCM method with respect to the target judged to be a real target (including the vertical distance, the relative velocity, and the horizontal position), the target data processing unit from the target data derivation unit 45 It is output to 46.

  In step S150, the target data processing unit 46 performs filtering to smooth the parameters of the target data (longitudinal distance, relative velocity, and horizontal position) in the time axis direction. Target data after such filtering is also referred to as "filter data" for instantaneous values.

  Next, based on the parameters (longitudinal distance, relative velocity, and horizontal position) of the target data, the target data processing unit 46 estimates a plurality of target data that can be estimated as target data related to the same object. Group together (step S160).

  Finally, the target data output unit 47 sends the target data thus processed to the vehicle control ECU 51 or the like. The target data output unit 47 selects a predetermined number (for example, 10) of target data from the grouped target data as an output target (step S170). The target data output unit 47 preferentially selects target data related to a target close to the host vehicle, in consideration of the vertical distance and the horizontal position of the target data.

  The target data selected as the output target in the above processing is stored in the memory 41, and is used as past target data in the target data acquisition process from the next time onward.

  By the flow operation shown in FIG. 3 described above, the radar device 1 can discriminate between a real target in which a speed difference with the vehicle does not substantially occur and a real target in which a speed difference with the vehicle is generated and periodic noise. . Thus, the radar device 1 can prevent the periodic noise from being erroneously recognized as a real target, so that the detection accuracy of the real target can be improved.

  In the flow operation shown in FIG. 3 described above, based on the first beat signal, the determination unit 45a determines whether the speed difference between the actual target and the host vehicle causes substantially no speed difference with the host vehicle or not. Noise (step S50) to derive a real target that hardly causes a speed difference with the host vehicle, and based on the second beat signal, a real target and a periodic target with a speed difference with the host vehicle Noise (step S120) to derive a real target that causes a speed difference with the vehicle.

  In addition, since the process of step S120, which is wasteful, is not performed for the determination target subjected to the process of step S60, efficient signal processing can be realized.

  However, unlike the present embodiment, based on the second beat signal, it discriminates between a real target that causes a speed difference with the host vehicle and a real target that generates substantially no speed difference between the host vehicle and periodic noise. To derive a real target that causes a speed difference with the host vehicle, and, based on the first beat signal, discriminates a real target and a periodic noise in which the speed difference with the host vehicle is substantially not generated. You may make it derive | lead-out a real target in which a speed difference with it does not arise substantially. In this case, in the discrimination process based on the frequency of the beat signal, the discrimination process based on the phase change among the plurality of chirps should not be performed on the discrimination target that is discriminated as the real target causing the speed difference with the vehicle. Efficient signal processing can be realized.

<2. Second embodiment>
FIG. 6 is a view showing the configuration of the radar device 1 according to the present embodiment. The radar device 1 according to the present embodiment differs from the radar device 1 according to the first embodiment in that the transmission control unit 42 includes a period setting unit 42a.

  The period setting unit 42a makes the lengths of periods (free running time) in which the FFT processing is not performed between a plurality of chirp signals in the FCM method irregular in one FCM period. Specifically, as shown in FIG. 6, the free running times t1_1, t1_2,..., T1_n in one FCM period are set to different lengths.

  In the first embodiment, when the beat frequency of the periodic noise happens to coincide with the beat frequency of the actual target at which the speed difference with the vehicle does not substantially occur, the radar device 1 proceeds to step S50 in FIG. By the processing of and S60, the periodic noise is erroneously recognized as a real target in which a speed difference with the vehicle does not substantially occur.

  On the other hand, in the present embodiment, by making the free running times t1_1, t1_2,..., T1_n different from each other, as shown in FIG. 7, the phase of each chirp changes with periodic noise. It was made to do. As a result, the relative speed of the periodic noise disappears at 0 km / h, and the radar device 1 does not generate a speed difference with the host vehicle substantially due to the process of steps S50 and S60 in FIG. It will not misunderstand that it is a standard.

  On the other hand, in the case of a real target in which the speed difference with the host vehicle does not substantially occur, the distance between the host vehicle and the real target does not substantially change, so the free running times t1_1, t1_2,. Even at different lengths, the phase at the start of each chirp will be the same. Therefore, as shown in FIG. 7, the phase of each chirp does not change in a real target in which a speed difference with the vehicle does not substantially occur.

  The radar device 1 according to the present embodiment can automatically generate periodic noise even when the beat frequency of the periodic noise accidentally matches the beat frequency of the actual target at which the speed difference with the vehicle does not substantially occur. Since the speed difference with the vehicle is not erroneously recognized as a real target which hardly generates, the detection accuracy of the real target can be further improved.

<3. Other>
Various technical features disclosed in the present specification can be modified in various ways without departing from the spirit of the technical creation in addition to the above embodiment. In addition, the plurality of embodiments and modifications shown in the present specification may be implemented in combination as far as possible.

  For example, instead of the FCM method that detects Doppler shift not as the frequency of beat signal but as phase change among multiple chirp signals, another method that detects Doppler shift as not phase of beat signal but as phase change among multiple modulation signals It may be adopted. As another method of detecting the Doppler shift not as the frequency of the beat signal but as the phase change between the plurality of modulation signals, for example, a pulse Doppler method which detects Doppler shift as the phase change among the plurality of pulse signals instead of the frequency of the beat signal Be That is, the “modulated signal” in the method of detecting the Doppler shift as a phase change between a plurality of modulated signals is a signal including a “chirp signal” or a “pulse signal”.

  For example, in the second embodiment, although the free running times t1_1, t1_2,..., T1_n in one FCM period are different from each other, each free running time t1_1 in one FCM period is different. Some of t1_2, ..., t1_n may have the same length. Even when a part of each free running time t1_1, t1_2,..., T1_n in one FCM period is made to have the same length, the same effect as the second embodiment can be obtained.

  Also, for example, in the second embodiment, steps S70 to S140 may not be performed. In this case, although it becomes impossible to distinguish between a real target causing a speed difference with the host vehicle and periodic noise, it is prevented that a periodic noise is erroneously recognized as a real target with almost no speed difference with the host vehicle. can do. Therefore, in the first embodiment, the detection accuracy of the target can be improved as compared with the case where steps S70 to S140 are not performed.

Reference Signs List 1 radar device 2 transmission unit 3 reception unit 4 signal processing device 42a period setting unit 45a determination unit

Claims (5)

A transmitter configured to transmit a transmission wave of a first system that detects Doppler shift as a phase change among a plurality of modulation signals, and a transmission wave of a second system that detects the Doppler shift as a frequency of a beat signal;
A reflected wave generated by reflecting the transmission wave of the first method to the target is received as a first reception signal, and a reflected wave generated by reflecting the transmission wave of the second method to the target A receiver for receiving as a second received signal;
A determination unit that determines, based on the first received signal and the second received signal, a real target that is actually present and periodic noise;
Equipped with
The determination unit derives the actual target in which the speed difference with the vehicle does not substantially occur based on the first received signal, and the speed difference with the vehicle is calculated based on the second received signal. A radar device for deriving the actual target to be generated. The determination unit
A phase change between the plurality of modulated signals is calculated from the first received signal, and based on the phase change between the plurality of modulated signals, the real target and the self Determining the real target that causes a speed difference with a vehicle and the periodic noise to derive the real target that hardly generates a speed difference with the host vehicle;
The frequency of the beat signal is calculated from the second received signal, and based on the frequency of the beat signal, the real target causing the speed difference with the host vehicle and the periodic noise are determined, Deriving the real target that causes a speed difference with the host vehicle,
The determination process based on the frequency of the beat signal is not performed for the determination target determined to be the real target in which the speed difference with the vehicle does not substantially occur in the determination process based on the phase change among the plurality of modulation signals. The radar apparatus according to claim 1. The determination unit
The frequency of the beat signal is calculated from the second received signal, and based on the frequency of the beat signal, the speed difference between the actual vehicle and the vehicle that causes a speed difference with the vehicle does not substantially occur. Determining the actual target and the periodic noise, and deriving the actual target that causes a speed difference with the host vehicle;
A phase change between the plurality of modulated signals is calculated from the first received signal, and the actual target and the period in which a speed difference with the host vehicle does not substantially occur based on the phase change among the plurality of modulated signals. To determine the real target from which almost no speed difference with the vehicle occurs.
The discrimination process based on the phase change among the plurality of modulation signals is not performed on the discrimination target that is discriminated as the real target in which the speed difference with the own vehicle occurs in the discrimination process based on the frequency of the beat signal. The radar apparatus of claim 1. The first method is an FCM (Fast-Chirp Modulation) method, and
The radar according to any one of claims 1 to 3, further comprising: a period setting unit that makes the lengths of periods during which FFT (Fast Fourier Transform) processing is not performed between a plurality of chirp signals in the FCM method irregular. apparatus. A transmission step of transmitting a transmission wave of a first system for detecting Doppler shift as a phase change between a plurality of modulated signals, and a transmission wave of a second system for detecting the Doppler shift as a frequency of a beat signal;
A reflected wave generated by reflecting the transmission wave of the first method to the target is received as a first reception signal, and a reflected wave generated by reflecting the transmission wave of the second method to the target Receiving as a second received signal;
A step of determining, based on the first received signal and the second received signal, a real target which is a target that actually exists and periodic noise;
Equipped with
The determining step derives the actual target in which the speed difference with the vehicle does not substantially occur based on the first received signal, and the speed difference with the vehicle is calculated based on the second received signal. Signal processing method to derive the resulting real target.