JP2019158797A - Radar device, and radar device control method - Google Patents

Abstract

To provide a radar device and radar device control method that can prevent throughput from increasing.SOLUTION: A radar device according to an embodiment comprises: a reception unit; a FET processing unit; and a peak extraction unit. The reception unit is configured to receive a reflection wave in which a transmission wave having a frequency successively changed is reflected by a target by a plurality of reception antennas. The FET processing unit is configured to, when conducting two-dimensional FFT processing to a beat signal based on the reflection wave received by an arbitrary reception antenna of the plurality of reception antennas, conduct a two-dimension-th FET processing thereto in a first range. The peak extraction unit is configured to extract a peak corresponding to a target from the frequency spectrum serving a processing result of the FFT processing unit. Further, the FFT processing unit is configured to, when conducting the two-dimensional FFT processing for other reception antenna other than the arbitrary reception antenna, conduct the two-dimension-th FET processing in a second range limiting the first range on the basis of a position of the peak extracted by the peak extraction unit.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a radar apparatus and a radar apparatus control method.

  Conventionally, as a radar device that detects a target, an FCM (Fast Chirp Modulation) type radar device that outputs a transmission wave whose frequency changes continuously and detects a distance, a relative speed, and an angle with the target has been proposed. ing.

  Specifically, the radar apparatus performs a two-dimensional fast Fourier transform process on each beat signal obtained by receiving reflected waves of a transmission wave target with a plurality of receiving antennas. The above-described distance, relative speed, and angle are detected (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 2006-3873

  However, in the conventional technique, for example, when there are a plurality of receiving antennas, the processing amount may increase because the two-dimensional FFT processing is performed for each receiving antenna.

  The present invention has been made in view of the above, and an object of the present invention is to provide a radar apparatus and a radar apparatus control method capable of preventing an increase in processing amount.

  In order to solve the above-described problems and achieve the object, a radar apparatus according to the present invention includes a reception unit, an FFT processing unit, and a peak extraction unit. The receiving unit receives a reflected wave obtained by reflecting a transmission wave having a continuously changing frequency by a target with a plurality of receiving antennas. The FFT processing unit performs the second-dimensional FFT processing when the two-dimensional FFT processing is performed on the beat signal based on the reflected wave received by an arbitrary receiving antenna among the plurality of receiving antennas. Do in range. The peak extraction unit extracts a peak corresponding to the target from a frequency spectrum that is a processing result of the FFT processing unit. In addition, when performing the two-dimensional FFT processing on the reception antenna other than the arbitrary reception antenna, the FFT processing unit calculates the first range based on the position of the peak extracted by the peak extraction unit. The second-dimensional FFT processing is performed within the limited second range.

  According to the present invention, it is possible to prevent the processing amount from increasing.

FIG. 1A is a diagram illustrating an example of a positional relationship between a radar device mounted on a vehicle and a target. FIG. 1B is a diagram illustrating an outline of a control method of the radar apparatus according to the embodiment. FIG. 2 is a block diagram of the radar apparatus. FIG. 3 is a diagram illustrating an example of a relationship among a transmission frequency, a reception frequency, and a beat frequency. FIG. 4 is a diagram illustrating a result of performing the distance FFT process on the beat signal. FIG. 5 is a diagram illustrating processing contents of the second processing unit. FIG. 6 is a diagram illustrating a processing amount in the two-dimensional FFT processing. FIG. 7 is a flowchart showing a target detection processing procedure executed by the radar apparatus. FIG. 8 is a diagram illustrating a method for controlling a radar apparatus according to a modification. FIG. 9 is a diagram illustrating a processing amount in the two-dimensional FFT processing according to the modification.

  Hereinafter, embodiments of a radar apparatus and a radar apparatus control method disclosed in the present application will be described in detail with reference to the accompanying drawings. In addition, this invention is not limited by this embodiment.

  First, an outline of a control method of a radar apparatus according to the embodiment will be described with reference to FIGS. 1A and 1B. FIG. 1A is a diagram illustrating an example of a positional relationship between a radar device mounted on a vehicle and a target. FIG. 1B is a diagram illustrating an outline of a control method of the radar apparatus according to the embodiment.

  As shown in FIG. 1A, the radar apparatus 1 according to the embodiment is provided at a front end portion of a vehicle MC and includes four reception antennas 21a to 21d (hereinafter may be referred to as reception antennas 21). I will do it. Note that the number of the receiving antennas 21a to 21d may be three or less or five or more as long as it is plural. Further, the mounting position of the radar apparatus 1 is not limited to the front end portion of the vehicle MC, and may be a side surface or a rear end portion of the vehicle MC.

  A radar apparatus 1 shown in FIG. 1A is, for example, an FCM (Fast Chirp Modulation) type radar apparatus. The FCM method is a method of detecting a distance and relative velocity with respect to each target P existing in a detection range by outputting a transmission wave in which a plurality of chirp waves whose frequencies change continuously are repeated.

  Specifically, in the FCM method, a reflected wave in which a transmission wave is reflected by a target P is received by a plurality of reception antennas 21a to 21d, and a beat signal generated from the received reflected wave and the transmission wave is received. A two-dimensional fast Fourier transform process (hereinafter sometimes referred to as a two-dimensional FFT process) is performed to detect the distance and relative velocity with respect to the target P.

  The two-dimensional FFT process is performed by performing two FFT processes, a distance FFT process in the distance direction corresponding to the distance to the target P and a speed FFT process in the speed direction corresponding to the speed of the target P. is there.

  Here, since the conventional radar apparatus performs the distance FFT process and the speed FFT process in the entire predetermined range, many calculations are required for calculating the target information (distance and relative speed). In addition, when the two-dimensional FFT processing is performed for each of the plurality of receiving antennas, the amount of calculation further increases, and the amount of processing increases. For this reason, for example, if the processing time of the two-dimensional FFT process becomes long, there is a possibility that the request for shortening the update cycle of the target information cannot be satisfied.

  Therefore, in the control method of the radar apparatus 1 according to the embodiment, first, among the plurality of reception antennas 21a to 21d, two-dimensional FFT processing is performed on an arbitrary reception antenna 21, and 2 in other reception antennas 21 is determined based on the processing result. The range of the dimensional FFT processing is limited.

  FIG. 1B shows a plurality of squares arranged two-dimensionally, and a two-dimensional FFT process is performed for each square. Specifically, such squares are arranged in the horizontal direction by the number of chirp waves (or beat signals) in the transmission wave and in the vertical direction by the number of distance bins (frequency) corresponding to the distance from the target P. Are lined up.

  The radar apparatus 1 according to the embodiment first performs a normal two-dimensional FFT process on the beat signals B1 to Bn generated for each chirp wave with respect to the reception antenna 21a. In the example shown in FIG. 1B, first, the radar apparatus 1 performs distance FFT processing (vertical direction shown in FIG. 1B) for each beat signal B1 to Bn as the first dimension. Specifically, the radar apparatus 1 performs distance FFT processing on all the beat signals B1 to Bn. In the middle diagram (left diagram) of FIG. 1B, it is assumed that, as a result of the distance FFT processing, a peak having a power value equal to or greater than a predetermined value appears in the distance bin fr10 in each beat signal B1 to Bn.

  Subsequently, the radar apparatus 1 according to the embodiment performs speed FFT processing for each distance bin fr as second-dimensional FFT processing. Specifically, the radar apparatus 1 performs speed FFT processing (lateral direction shown in FIG. 1B) on all distance bins fr. That is, the range (first range) in the second-dimensional FFT processing is the distance bin fr1 to the distance bin frm. The first range is not limited to all the distance bins fr1 to frm. For example, among the distance bins fr1 to frm, only the distance bin fr at the peak position of the target P at the previous time is the first range. It is good also as 1 range. In the lower diagram (left diagram) of FIG. 1B, it is assumed that a peak appears in the velocity bin fv5 as a result of the velocity FFT process.

  When the two-dimensional FFT processing is performed on the receiving antennas 21b to 21d other than the receiving antenna 21a, the radar apparatus 1 according to the embodiment is the second range that limits the above-described first range and the second dimension. FFT processing is performed. Specifically, as shown in the middle diagram (right diagram) of FIG. 1B, the radar apparatus 1 first performs the first-dimensional FFT processing in the entire range (lateral direction) from the beat signals B1 to Bn. . That is, the first-dimensional FFT processing range is the same as that of the reception antenna 21a.

  The radar apparatus 1 according to the embodiment limits the range based on the peak position extracted as a result of the two-dimensional FFT process of the receiving antenna 21a when performing the second-dimensional FFT process.

  For example, as illustrated in the lower diagram (right diagram) of FIG. 1B, the radar apparatus 1 according to the embodiment performs only the second distance bin fr10 corresponding to the peak position in the range from the distance bin fr1 to the distance bin frm. As a range, the second-dimensional FFT processing is performed. That is, the other receiving antennas 21b to 21d perform the second-dimensional FFT processing in the second range that is narrower than the first range.

  In the example shown in FIG. 1B, the second range in the second-dimensional FFT processing is limited to the distance bin fr10 that is the peak position. However, for example, the distance including the distance bin fr10 A range from the bin fr9 to the distance bin fr11 may be set as the second range. In other words, the range includes the distance bin fr10 and may be a range in which the first range from the distance bin fr1 to the distance bin frm is limited.

  As described above, by using the processing result of the two-dimensional FFT of the receiving antenna 21a, by limiting the range of the second-dimensional FFT processing for the other receiving antennas 21b to 21d, unnecessary FFT processing calculation is omitted. be able to. Therefore, according to the radar apparatus 1 according to the embodiment, it is possible to reduce the calculation amount in the two-dimensional FFT processing, and thus it is possible to prevent the processing amount from increasing. Note that the calculation reduction amount of the two-dimensional FFT processing will be described later in detail with reference to FIG.

  In the example shown in FIG. 1B, the speed FFT processing is performed after the distance FFT processing is performed for the two-dimensional FFT processing, but the processing order may be changed. That is, the distance FFT process may be performed after the speed FFT process, which will be described later with reference to FIGS.

  Next, the configuration of the radar apparatus 1 according to the embodiment will be described with reference to FIG. FIG. 2 is a block diagram of the radar apparatus 1. As shown in FIG. 2, the radar device 1 is connected to a vehicle control device 2.

  The vehicle control device 2 performs vehicle control such as PCS (Pre-crash Safety System) and AEB (Advanced Emergency Braking System) based on the detection result of the target P by the radar device 1. The radar device 1 may be used for various purposes other than the on-vehicle radar device (for example, monitoring of an airplane or a ship).

  The radar apparatus 1 includes a transmission unit 10, a reception unit 20, and a processing unit 30. The transmission unit 10 includes a signal generation unit 11, an oscillator 12, and a transmission antenna 13. The signal generator 11 generates a modulated signal whose voltage changes in a sawtooth waveform and supplies the modulated signal to the oscillator 12. The oscillator 12 generates a chirp signal ST based on the modulation signal generated by the signal generation unit 11 and outputs the chirp signal ST to the transmission antenna 13.

  The transmission antenna 13 converts the chirp signal ST input from the oscillator 12 into a transmission wave SW, and outputs the transmission wave SW to the outside of the vehicle MC. The transmission wave SW output from the transmission antenna 13 is a waveform in which a plurality of chirp waves are repeated. The transmission wave SW transmitted from the transmission antenna 13 to the front of the vehicle MC is reflected by the target P and becomes a reflected wave.

  The receiving unit 20 includes a plurality of receiving antennas 21a to 21d, mixers 22a to 22d, and A / D converters 23a to 23d that form an array antenna. Each receiving antenna 21 receives a reflected wave from the target P as a received wave RW, converts the received wave RW into a received signal SR, and outputs the received signal RW to a mixer 22 provided for each receiving antenna 21. The number of receiving antennas 21 shown in FIG. 2 is four, but it may be three or less or five or more.

  The reception signal SR output from each reception antenna 21 is amplified by an amplifier (not shown) (for example, a low noise amplifier) and then input to the mixer 22. The mixer 22 mixes a part of the chirp signal ST and the reception signal SR, removes unnecessary signal components, generates a beat signal SB, and outputs the beat signal SB to the A / D converter 23.

As a result, the beat frequency f _SB (which is the difference between the frequency f _ST of the chirp signal ST (hereinafter referred to as the transmission frequency f _ST ) and the frequency f _SR of the reception signal _SR (hereinafter referred to as the reception frequency f _SR ). = F _ST −f _SR ) is generated. The beat signal SB generated by the mixer 22 is converted to a digital signal by the A / D converter 23 and then output to the processing unit 30.

FIG. 3 is a diagram illustrating an example of the relationship among the transmission frequency _fST , the reception frequency _fSR, and the beat frequency _fSB . As shown in FIG. 3, the beat signal SB is generated for each chirp wave. Here, the beat signal SB obtained by the first chirp wave is “B1”, the beat signal SB obtained by the second chirp wave is “B2”, and the beat signal SB obtained by the nth chirp wave is “B2”. Is “Bn”.

Further, in the example shown in FIG. 3, the transmission frequency _{f ST,} for each chirp wave, along with the reference frequency f0 time increases at a gradient θ (= (f1-f0) / Tm), reaching the maximum frequency f1 A saw-tooth wave shape (so-called up-chirp) that returns to the reference frequency f0 in a short time. The transmission frequency _{f ST} is reached in a short time from the reference frequency f0 to the maximum frequency f1 for each chirp wave, decreases with a slope with the take up frequency f1 in the time θ (= (f0-f1) / Tm) Sawtooth wave shape (so-called down chirp) may be used.

  Returning to the description of FIG. 2, the processing unit 30 will be described. The processing unit 30 includes a transmission control unit 31 and a signal processing unit 32. The signal processing unit 32 includes a first processing unit 33, a second processing unit 34, a peak extraction unit 35, a calculation unit 36, and an output unit 37.

  The processing unit 30 is a microcomputer including, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an input / output port, and the like, and controls the entire radar apparatus 1.

  The CPU of the microcomputer functions as the transmission control unit 31 and the signal processing unit 32 by reading and executing the program stored in the ROM. Note that at least a part or all of the transmission control unit 31 and the signal processing unit 32 can be configured by hardware such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array).

  The transmission control unit 31 controls the signal generation unit 11 of the transmission unit 10 and causes the signal generation unit 11 to output a modulation signal whose voltage changes in a sawtooth shape to the oscillator 12. As a result, a chirp signal ST whose frequency changes with the passage of time is output from the oscillator 12 to the transmitting antenna 13.

  The signal processing unit 32 performs two-dimensional FFT processing (distance FFT processing and velocity FFT processing) on the beat signal SB output from each A / D converter 23, and based on the result of the two-dimensional FFT processing. The distance, relative speed (relative speed in the vertical direction and relative speed in the horizontal direction) and direction of the target P are calculated. Hereinafter, processing of each unit of the signal processing unit 32 will be described.

  The first processing unit 33 (an example of the FFT processing unit) of the signal processing unit 32 performs a frequency FFT process on each beat signal SB output from each A / D converter 23 to thereby generate a frequency for each reception antenna 21. Generate a spectrum. Specifically, the first processing unit 33 performs distance FFT processing on each distance bin fr (fr1 to frm) for each beat signal SB. Here, the result of the distance FFT process will be specifically described with reference to FIG.

  FIG. 4 is a diagram illustrating a result of performing the distance FFT process on the beat signal SB. FIG. 4 shows a frequency spectrum that is a result of the distance FFT process for the beat signal B5. In the frequency spectrum shown in FIG. 4, the horizontal axis represents frequency (that is, distance bin), and the vertical axis represents power magnitude (peak magnitude). In the example shown in FIG. 4, it is assumed that a peak appears only in the distance bin fr10.

  Here, the frequency of the beat signal SB increases or decreases in proportion to the distance between the target P and the radar apparatus 1. For this reason, the first processing unit 33 performs a distance FFT process on the beat signal SB, whereby a peak appearing in the distance bin fr corresponding to the distance from the target P (power is equal to or greater than a predetermined value) is detected as the distance FFT. Get as a result of processing.

  That is, in the example illustrated in FIG. 4, the first processing unit 33 acquires information indicating that a peak appears in the distance bin fr10 as a result of the distance FFT process in one beat signal B5.

  The first processing unit 33 may perform distance FFT processing on the beat signals SB of the four receiving antennas 21a to 21d when receiving the beat signal SB from the four receiving antennas 21a to 21d, or The distance FFT process may be performed only on the beat signal SB of the receiving antenna 21a. When the distance FFT process is performed only on the beat signal SB of the reception antenna 21a, the distance FFT process is performed on the other three reception antennas 21b to 21d after receiving the extraction result of the peak extraction unit 35 described later.

  The first processing unit 33 outputs a frequency spectrum that is a result of the distance FFT processing to the second processing unit 34.

  The second processing unit 34 performs a speed FFT process on the result of the distance FFT process in the first processing unit 33. The speed FFT process is to perform the second FFT process for each speed bin fv for each distance bin fr of the frequency spectrum that is the result of the distance FFT process. Thereby, as a result of the speed FFT process, a peak appears in the speed bin fv corresponding to the relative speed of the target P.

  Specifically, the second processing unit 34 uses a Doppler component of the reception signal SR that is generated when the relative speed of the target P is not zero. More specifically, the second processing unit 34 detects a change in peak phase in the frequency spectrum of the beat signal SB. Here, the processing content of the 2nd process part 34 is demonstrated concretely using FIG.

  FIG. 5 is a diagram illustrating processing contents of the second processing unit 34. In FIG. 5, the frequency spectrum of any one of the plurality of receiving antennas 21 is shown in time series. Further, FIG. 5 shows an example of the result of the distance FFT processing of the beat signals B1 to B8 that are temporally continuous and the peak phase change between the beat signals B1 to B8. In the example shown in FIG. 5, the distance bin fr10 of each of the beat signals B1 to B8 has a peak, and the phase of the peak changes.

  Here, when the relative speed between the target P and the radar apparatus 1 is not zero, a phase change corresponding to the Doppler frequency is present at the peak of the distance bin fr10 corresponding to the same target P between the beat signals B1 to B8. Appear.

  The second processing unit 34 obtains a frequency spectrum in which a peak appears in a frequency bin (speed bin) with respect to the Doppler frequency by arranging the frequency spectrum obtained by performing the distance FFT process in time series and performing the speed FFT process.

  As shown in FIG. 5, the second processing unit 34 performs the speed FFT processing for each distance bin fr in the entire range from the distance bin fr1 to the distance bin frm for the reception antenna 21a. And the 2nd processing part 34 limits the range which performs a speed FFT process based on the position of the peak extracted by the below-mentioned peak extraction part 35 about other three receiving antennas 21b-21d.

  For example, as illustrated in FIG. 5, when a peak is extracted in the distance bin fr10 by the peak extraction unit 35, the second processing unit 34 performs the speed FFT process only on the distance bin fr10. That is, the second processing unit 34 does not perform the speed FFT processing on the distance bins fr other than the peak distance bin fr10 extracted by the peak extraction unit 35. Thereby, the processing amount in the two-dimensional FFT processing can be minimized.

  Returning to FIG. 2, the peak extraction unit 35 will be described. The peak extraction unit 35 extracts a peak whose power is equal to or greater than a predetermined threshold from the frequency spectrum that is a result of the speed FFT process in the second processing unit 34. Such a threshold value may be a predetermined fixed value or may be dynamically changed.

  When the extracted peak is the peak of the frequency spectrum corresponding to the reception antenna 21a, the peak extraction unit 35 outputs information on the peak to the second processing unit 34. Moreover, the peak extraction part 35 outputs the information regarding this peak to the calculating part 36, when it can confirm that the peak has appeared in the same position in the peak extraction result of all the receiving antennas 21a-21d. .

  Note that the peak extraction unit 35 may prohibit the output to the calculation unit 36 when, for example, at least one of all the peak extraction results does not appear at the same position. Thereby, since a peak with low reliability can be removed, erroneous detection of the target P can be prevented.

  The calculation unit 36 calculates the distance, relative speed, and angle (azimuth) with the target P based on the peak extracted by the peak extraction unit 35.

  Specifically, the calculation unit 36 derives the distance and relative velocity with respect to the target P based on the combination of the peak distance bin fr and the velocity bin fv extracted by the peak extraction unit 35.

  In addition, the calculation unit 36 estimates an angle at which the target P exists by a predetermined angle calculation process. Specifically, the calculation unit 36 determines the angle of the target P by the difference in the phase of the peak of the same distance bin fr of each of the frequency spectra of the four beat signals SB based on the reception signals SR of the four reception antennas 21a to 21d. presume. If it is detected that there are a plurality of targets P in the same distance bin due to the difference in the phase of the peak of the same distance bin fr, angle estimation is performed for each of the plurality of targets P.

  The angle estimation in the calculation unit 36 is performed using a predetermined estimation method such as ESPRIT (Estimation of Signal Parameters via Rotational Invariance Techniques), DBF (Digital Beam Forming), or MUSIC (Multiple Signal Classification). Is called.

  The output unit 37 outputs various information to the vehicle control device 2. For example, the output unit 37 outputs target information regarding the detected target P to the vehicle control device 2. The target information includes the distance, relative speed, and angle of the target P.

  Here, the processing amount in the two-dimensional FFT processing will be described with reference to FIG. FIG. 6 is a diagram illustrating a processing amount in the two-dimensional FFT processing. “1 normal FCM” shown in FIG. 6 indicates a processing amount when the distance FFT processing and the speed FFT processing are performed in all ranges, and “2 improved FCM” indicates the speed FFT processing that is the second dimension. The processing amount when performed in a limited range (second range) is shown.

  In FIG. 6, the number of distance FFT bins (distance bins fr1 to frm) is 1024, the number of chirps (number of beat signals SB) is 64, and the number of peaks extracted by the peak extraction unit 35 is 10 It is assumed that the number of receiving antennas 21 is four. Also, “complex number of multiplications” and “complex number of additions / subtractions” shown in FIG. 6 indicate the number of multiplications and additions / subtractions of complex numbers in the butterfly operation in each FFT process. Specifically, the distance FFT is represented by α = P / 2 × LOG (P, 2) × N, where α is the number of complex multiplications, P is the number of distance FFT bins, and N is the number of chirps. When the number of additions / subtractions is β, β = P × LOG (P, 2) × N. The speed FFT processing is represented by α = P / 2 × LOG (P, 2) × N, where α is the number of complex multiplications, P is the number of chirps, and N is the number of distance FFT bins. Is represented by β = P × LOG (P, 2) × N.

  As shown in FIG. 6, when “1 normal FCM” and “2 improved FCM” are compared, the processing amounts (C and D in the figure) of the distance FFT processing performed by the first processing unit 33 are the same. In addition, the processing amount (E, F in the figure) for one channel of the receiving antenna 21 in the speed FFT processing performed by the second processing unit 34 is also the same.

  On the other hand, for the 3ch of the other receiving antenna 21 in the speed FFT process performed by the second processing unit 34, “2 improved FCM” (G / 100 × 3ch) is more than “1 normal FCM” (G × 3ch). The amount of processing is also small. This is because the 3ch receiving antenna 21 performs the speed FFT process only on the distance bin fr corresponding to the peak.

  Thereby, as shown in FIG. 6, “2 improved FCM” can be suppressed to about 70% (72%) of the processing amount of “1 normal FCM”. Note that the “distance FFT bin number”, “chirp number”, “peak number”, and “reception antenna number” shown in FIG. 6 are examples, and arbitrary values may be set.

  Next, a processing procedure executed by the radar apparatus 1 according to the embodiment will be described with reference to FIG. FIG. 7 is a flowchart showing the target detection processing procedure executed by the radar apparatus 1. 7 is repeatedly executed by the radar apparatus 1.

  As shown in FIG. 7, first, the transmitter 10 outputs a transmission wave SW including n chirp waves (step S101). Subsequently, the receiving unit 20 generates n beat signals SB from the received signal SR and the chirp signal ST corresponding to the reflected wave of the transmitted wave SW by the target P (step S102).

  Subsequently, the first processing unit 33 performs distance FFT processing on each of the n beat signals SB (step S103). Subsequently, the second processing unit 34 performs a speed FFT process on the result of the distance FFT process of any one of the plurality of reception antennas 21 (step S104).

  Subsequently, the peak extraction unit 35 extracts a peak whose power is equal to or greater than a predetermined threshold from the frequency spectrum as a result of the speed FFT process (step 105). Subsequently, the second processing unit 34 performs the speed FFT process on the other receiving antennas 21 only at the positions of the peaks extracted by the peak extracting unit 35 (step S106).

  Subsequently, the calculation unit 36 performs a calculation process of calculating the distance, relative speed, and angle with the target P based on the peak extracted by the peak extraction unit 35 (step S107). Subsequently, the output unit 37 outputs the target information including the distance, relative speed, and angle calculated by the calculation unit 36 to the vehicle control device 2 (step S108), and ends the process.

  As described above, the radar apparatus 1 according to the embodiment includes the receiving unit 20, the FFT processing unit (for example, the first processing unit 33 and the second processing unit 34), and the peak extraction unit 35. The receiving unit 20 receives a reflected wave, which is a reflected wave reflected by the target P, with a plurality of receiving antennas 21. When performing a two-dimensional FFT process on the beat signal SB based on the reflected wave received by an arbitrary reception antenna 21 among the plurality of reception antennas 21, the FFT processing unit performs the second-dimensional FFT process on the first dimension. Do in range. The peak extraction unit 35 extracts a peak corresponding to the target P from the frequency spectrum that is the processing result of the FFT processing unit. In addition, when performing the two-dimensional FFT processing on the other receiving antennas 21 other than the arbitrary receiving antenna 21, the FFT processing unit limits the first range based on the peak position extracted by the peak extracting unit 35. The second-dimensional FFT processing is performed in the range of. Thereby, it can prevent that processing amount increases.

  In the above-described embodiment, the speed FFT process is performed after the distance FFT process is performed on the beat signal SB. However, the processing order of the two-dimensional FFT process may be reversed. That is, the radar apparatus 1 may perform the distance FFT process after performing the speed FFT process on the beat signal SB. Even if the processing order is changed, the number of peaks obtained after the two-dimensional FFT processing and the position of the peaks are not changed. Here, a case where the processing order of the two-dimensional FFT processing is changed will be described with reference to FIG.

  FIG. 8 is a diagram illustrating a control method of the radar apparatus 1 according to the modification. As shown in FIG. 8, the radar apparatus 1 may change the processing order of the two-dimensional FFT processing for all the receiving antennas 21a to 21d. Specifically, first, the second processing unit 34 performs speed FFT processing for each distance bin fr in the range of distance bins fr1 to frm for all beat signals SB in the reception antenna 21a. At this stage, no peak specifying the velocity bin fv is obtained in the frequency spectrum obtained as a result of the FFT processing.

  Subsequently, the first processing unit 33 performs distance FFT processing for each beat signal SB on the frequency spectrum generated by the second processing unit 34 in the range of all beat signals B1 to Bn. As a result, a peak corresponding to the target P is obtained in the specific distance bin fr10 and the velocity bin fv5. That is, in the above-described embodiment, the second-dimensional FFT process is the speed FFT process, but in the modification, the second-dimensional FFT process is the distance FFT process. That is, in the modification, the range of all beat signals B1 to Bn that is the range of the distance FFT processing is the first range.

  Subsequently, the second processing unit 34 performs speed FFT processing for each distance bin fr in the range of distance bins fr1 to frm for all beat signals SB in the other receiving antennas 21b to 21d.

  Subsequently, the first processing unit 33 performs a distance FFT process on the frequency spectrum generated by the second processing unit 34 in a second range in which the first range is limited. In the example illustrated in FIG. 8, the first processing unit 33 performs the distance FFT process using only the extracted peak velocity bin fv5 as the second range. Thereby, even if it is a case where the processing order of a two-dimensional FFT process is replaced, it can prevent that processing amount increases.

  Note that the processing order of the two-dimensional FFT processing in the other receiving antennas 21b to 21d may be determined based on the number of peaks extracted by the receiving antenna 21a. This point will be described with reference to FIG.

  FIG. 9 is a diagram illustrating a processing amount in the two-dimensional FFT processing according to the modification. “1 normal FCM” and “2 improved FCM” illustrated in FIG. 9 are processing orders in which the speed FFT processing is performed after the distance FFT processing. “3 improved FCM” is a processing order in which the distance FFT processing is performed after the speed FFT processing. FIG. 9 shows a case where the number of peaks extracted by the peak extraction unit 35 is 10 and a case where the number is 60.

  As shown in FIG. 9, when the number of peaks is 10, “3 improved FCM” has the smallest processing amount. On the other hand, when the number of peaks is 60, “2 improved FCM” has the smallest processing amount. This is due to the processing amount of the “second FFT processing (for other 3 channels)”.

  Specifically, the increase in the processing amount with respect to the increase in the number of peaks is larger in the “3 improved FCM” than in the “2 improved FCM”.

  That is, if the number of peaks is less than the predetermined number, the processing amount of “3 improved FCM” is smaller than that of “2 improved FCM”, but “2 improved FCM” and “3 improved FCM” as the number of peaks approaches the predetermined number. ”Is reduced.

  When the number of peaks is equal to or larger than the predetermined number, the processing amount of “3 improved FCM” is larger than that of “2 improved FCM”. That is, the processing amount is reversed.

  In other words, when the number of peaks extracted by the peak extraction unit 35 is less than a predetermined number, the first processing unit 33 and the second processing unit 34 perform a two-dimensional FFT process in the order of “3 improved FCM”. .

  On the other hand, when the number of peaks extracted by the peak extraction unit 35 is equal to or greater than a predetermined number, the first processing unit 33 and the second processing unit 34 perform the two-dimensional FFT processing in the processing order of “2 improved FCM”.

  In this manner, the first processing unit 33 and the second processing unit 34 always suppress the processing amount to the minimum by determining the processing order of the two-dimensional FFT processing depending on whether or not the number of peaks is equal to or greater than a predetermined number. Can do.

  Note that the predetermined number is determined based on, for example, “distance FFT bin number”, “chirp number”, and “receive antenna number” shown in FIG.

  FIG. 9 shows the processing amount of the two-dimensional FFT processing when the “distance FFT bin number” is 1024 and the “chirp number” is 64. For example, the “distance FFT bin number” is 64, When the “number of chirps” is 1024, the processing amount shown in FIG. 9 is reversed.

  That is, when the “distance FFT bin number” is 64 and the “chirp number” is 1024, and when the number of peaks is 10, “2 improved FCM” has the smallest processing amount, while the peak number is In the case of 60, “3 improved FCM” has the smallest processing amount.

  Further effects and modifications can be easily derived by those skilled in the art. Thus, the broader aspects of the present invention are not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications can be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

DESCRIPTION OF SYMBOLS 1 Radar apparatus 2 Vehicle control apparatus 10 Transmission part 11 Signal generation part 12 Oscillator 13 Transmission antenna 20 Reception part 21,21a-21d Reception antenna 22,22a-22d Mixer 23,23a-23d A / D converter 30 Processing part 31 Transmission Control unit 32 Signal processing unit 33 First processing unit 34 Second processing unit 35 Peak extraction unit 36 Calculation unit 37 Output unit 100 Radar device MC Vehicle P Target

Claims (4)

A receiving unit that receives a reflected wave, which is a reflected wave reflected by a target, with a plurality of receiving antennas, and a transmission wave whose frequency continuously changes,
An FFT processing unit that performs a second-dimensional FFT process in a first range when performing a two-dimensional FFT process on a beat signal based on the reflected wave received by an arbitrary receive antenna among the plurality of receive antennas When,
A peak extraction unit that extracts a peak corresponding to the target from a frequency spectrum that is a processing result by the FFT processing unit,
The FFT processing unit
When the two-dimensional FFT processing is performed for the other receiving antennas other than the arbitrary receiving antenna, the second range that limits the first range based on the peak position extracted by the peak extracting unit is used. A radar apparatus characterized by performing a second-dimensional FFT process. The FFT processing unit
2. The radar apparatus according to claim 1, wherein the second-dimensional FFT processing is performed using only the peak position as the second range. The two-dimensional FFT process is a process in which the processing order of the first process in the distance direction corresponding to the distance to the target and the second process in the speed direction corresponding to the relative speed of the target can be switched. There,
The FFT processing unit
3. The radar according to claim 1, wherein when the two-dimensional FFT processing is performed on the other receiving antenna, the processing order is determined based on the number of the peaks extracted by the peak extraction unit. apparatus. A reception process in which a transmission wave whose frequency is continuously changed is reflected by a plurality of receiving antennas and is reflected by a target;
FFT processing step of performing second-dimensional FFT processing in a first range when performing two-dimensional FFT processing on a beat signal based on the reflected wave received by an arbitrary receiving antenna among the plurality of receiving antennas When,
A peak extraction step of extracting a peak corresponding to the target from a frequency spectrum that is a processing result of the FFT processing step,
The FFT processing step includes
When the two-dimensional FFT processing is performed for the other receiving antennas other than the arbitrary receiving antenna, the second range is defined by limiting the first range based on the peak position extracted by the peak extracting step. A radar apparatus control method, characterized by performing a second-dimensional FFT process.

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