JP7127998B2 - radar equipment - Google Patents

Description

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

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

Specifically, the radar apparatus performs two-dimensional Fast Fourier Transform processing on each beat signal obtained by receiving the reflected wave of the transmitted wave from the target with a plurality of receiving antennas. , the above distance, relative velocity and angle are detected (see, for example, Patent Document 1).

JP 2016-3873 A

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

SUMMARY OF THE INVENTION It is an object of the present invention to provide a radar device and a radar device control method that can prevent an increase in the amount of processing.

In order to solve the above-described problems and achieve the object, a radar device according to the present invention includes a receiver, an FFT processor, and a peak extractor. The receiving section receives, with a plurality of receiving antennas, reflected waves of transmitted waves whose frequencies continuously change and which are reflected by a target. 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, the FFT processing unit performs second-dimensional FFT processing on a first do it in range. The peak extraction unit extracts a peak corresponding to the target from the frequency spectrum that is the result of processing by the FFT processing unit. Further, when the FFT processing unit performs the two-dimensional FFT processing for the receiving antenna other than the arbitrary receiving antenna, the FFT processing unit determines the first range based on the position of the peak extracted by the peak extracting unit. The second-dimensional FFT processing is performed in the limited second range.

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

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

Embodiments of a radar device and a radar device control method disclosed in the present application will be described in detail below with reference to the accompanying drawings. It should be noted that the present invention is not limited by this embodiment.

First, an outline of a control method for a radar device according to an embodiment will be described with reference to FIGS. 1A and 1B. FIG. 1A is a diagram showing an example of the 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 for a radar device according to the embodiment;

As shown in FIG. 1A, a radar device 1 according to the embodiment is provided at the front end of a vehicle MC, and includes four receiving antennas 21a to 21d (hereinafter sometimes referred to as receiving antennas 21). It is assumed that The number of receiving antennas 21a to 21d may be three or less or five or more as long as the number is plural. Further, the mounting position of the radar device 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.

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

Specifically, in the FCM method, a transmitted wave reflected by a target P is received by a plurality of receiving antennas 21a to 21d, and a beat signal generated from the received reflected wave and the transmitted wave is Two-dimensional Fast Fourier Transform processing (hereinafter sometimes referred to as two-dimensional FFT processing) is performed to detect the distance to the target P and the relative speed.

Note that the two-dimensional FFT processing is performed by performing two FFT processing, a distance FFT processing in the distance direction corresponding to the distance to the target P and a speed FFT processing in the speed direction corresponding to the speed of the target P. be.

Here, since the conventional radar device performs distance FFT processing and speed FFT processing in the entire predetermined range, calculation of target object information (distance and relative speed) requires many calculations. Moreover, if two-dimensional FFT processing is performed for each of a plurality of receiving antennas, the amount of calculation becomes even more enormous, resulting in an increase in the amount of processing. For this reason, for example, if the processing time of the two-dimensional FFT processing becomes long, there is a possibility that the demand for shortening the target information update cycle may not be met.

Therefore, in the control method of the radar apparatus 1 according to the embodiment, first, two-dimensional FFT processing is performed on an arbitrary receiving antenna 21 among the plurality of receiving antennas 21a to 21d, and the two-dimensional FFT processing on the other receiving antennas 21 is performed based on the processing result. Limit the scope of the dimensional FFT process.

FIG. 1B shows a plurality of squares arranged two-dimensionally, and two-dimensional FFT processing is performed for each such square. Specifically, such squares are arranged horizontally by the number of chirp waves (or beat signals) in the transmitted wave, and vertically by the number of distance bins (frequency) corresponding to the distance to 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 receiving antenna 21a. In the example shown in FIG. 1B, first, the radar device 1 performs distance FFT processing (vertical direction shown in FIG. 1B) for each of the beat signals B1 to Bn as the first dimension. Specifically, the radar device 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 of the beat signals B1 to Bn.

Subsequently, the radar device 1 according to the embodiment performs velocity FFT processing for each distance bin fr as second-dimensional FFT processing. Specifically, the radar device 1 performs velocity FFT processing (horizontal direction shown in FIG. 1B) for all distance bins fr. That is, the range (first range) in the second-dimensional FFT processing is from the distance bin fr1 to the distance bin frm. Note that the first range is not limited to all the distance bins fr1 to frm. It may be in the range of 1. In the lower diagram (left diagram) of FIG. 1B, it is assumed that a peak appears in velocity bin fv5 as a result of velocity FFT processing.

Then, when performing two-dimensional FFT processing on the receiving antennas 21b to 21d other than the receiving antenna 21a, the radar device 1 according to the embodiment performs the second range in the second range obtained by limiting the first range. FFT processing is performed. Specifically, as shown in the middle diagram (right diagram) of FIG. 1B, the radar device 1 first performs the first-dimensional FFT processing in the entire range (horizontal direction) of the beat signals B1 to Bn. . That is, the range of the first-dimensional FFT processing is the same range as that of the receiving antenna 21a described above.

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

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

The example shown in FIG. 1B shows the case where the second range in the second-dimensional FFT processing is limited to only the distance bin fr10, which is the position of the peak. The second range may be the range from bin fr9 to distance bin fr11. In other words, it is sufficient that the range includes the distance bin fr10 and limits the first range from the distance bin fr1 to the distance bin frm.

In this way, by using the two-dimensional FFT processing result of the receiving antenna 21a and limiting the range of the second-dimensional FFT processing for the other receiving antennas 21b to 21d, unnecessary FFT processing calculations are omitted. be able to. Therefore, according to the radar device 1 according to the embodiment, it is possible to reduce the amount of calculation in the two-dimensional FFT processing, thereby preventing an increase in the amount of processing. Note that the calculation reduction amount of the two-dimensional FFT processing will be described later in detail with reference to FIG.

In addition, in the example shown in FIG. 1B, for the two-dimensional FFT processing, the distance FFT processing is performed and then the speed FFT processing is performed, but the processing order may be changed. In other words, the distance FFT process may be performed after the velocity FFT process, but this point will be described later with reference to FIGS. 8 and 9. FIG.

Next, the configuration of the radar device 1 according to the embodiment will be described using FIG. FIG. 2 is a block diagram of the radar device 1. As shown in FIG. 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 . Note that the radar device 1 may be used for various purposes other than the vehicle-mounted radar device (for example, monitoring of airplanes and ships, etc.).

The radar device 1 includes a transmitter 10 , a receiver 20 and a processor 30 . The transmitter 10 includes a signal generator 11 , an oscillator 12 and a transmission antenna 13 . The signal generator 11 generates a modulated signal whose voltage changes like a sawtooth wave, and supplies the modulated signal to the oscillator 12 . The oscillator 12 generates a chirp signal ST based on the modulated signal generated by the signal generator 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 has a waveform in which a plurality of chirp waves are repeated. A transmission wave SW transmitted forward of the vehicle MC from the transmission antenna 13 is reflected by the target P and becomes a reflected wave.

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

A received signal SR output from each receiving antenna 21 is input to the mixer 22 after being amplified by an amplifier (for example, a low noise amplifier) not shown. The mixer 22 mixes a part of the chirp signal ST and the received signal SR to remove 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} ( = f _ST −f _SR ) is generated. The beat signal SB generated by the mixer 22 is output to the processing section 30 after being converted into a digital signal by the A/D converter 23 .

FIG. 3 is a diagram showing an example of the relationship among the transmission frequency f _ST , the reception frequency f _SR , and the beat frequency f _SB . 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 defined as "B1", the beat signal SB obtained by the second chirp wave is defined as "B2", and the beat signal SB obtained by the n-th chirp wave. is "Bn".

In the example shown in FIG. 3, the transmission frequency f _ST increases with time from the reference frequency f0 with a slope θ (=(f1−f0)/Tm) for each chirp wave, and reaches the maximum frequency f1. It is a sawtooth wave (so-called up-chirp) that returns to the reference frequency f0 in a short period of time. The transmission frequency _fST reaches the maximum frequency f1 from the reference frequency f0 for each chirp wave in a short time, and decreases with time from the maximum frequency f1 with a slope θ (=(f0−f1)/Tm). A sawtooth wave (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 section 32 includes a first processing section 33 , a second processing section 34 , a peak extraction section 35 , a calculation section 36 and an output section 37 .

The processing unit 30 is, for example, a microcomputer including a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), input/output ports, etc., and controls the radar device 1 as a whole.

The CPU of such a microcomputer functions as a transmission control section 31 and a signal processing section 32 by reading and executing programs stored in the ROM. 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 ASIC (Application Specific Integrated Circuit) or 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 to the oscillator 12 a modulated signal whose voltage changes in a sawtooth pattern. As a result, a chirp signal ST whose frequency changes over 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 speed FFT processing) on each 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 bearing of the target P are calculated. Processing of each unit of the signal processing unit 32 will be described below.

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

FIG. 4 is a diagram showing the result of performing distance FFT processing on the beat signal SB. FIG. 4 shows the frequency spectrum, which is the result of distance FFT processing on the beat signal B5. In the frequency spectrum shown in FIG. 4, the horizontal axis is frequency (that is, distance bin), and the vertical axis is 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 device 1. FIG. For this reason, the first processing unit 33 performs distance FFT processing on the beat signal SB, so that peaks (with power equal to or greater than a predetermined value) that appear in the distance bin fr corresponding to the distance to the target P are detected by distance FFT processing. Acquired as a result of processing.

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

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

The first processing unit 33 outputs the frequency spectrum resulting from the distance FFT processing to the second processing unit 34 .

The second processing unit 34 performs velocity FFT processing on the result of the distance FFT processing in the first processing unit 33 . The speed FFT processing is to perform the second FFT processing for each speed bin fv for each distance bin fr of the frequency spectrum resulting from the distance FFT processing. As a result of the velocity FFT processing, a peak appears in the velocity bin fv corresponding to the relative velocity of the target P. FIG.

Specifically, the second processing unit 34 uses the Doppler component of the received signal SR that occurs when the relative velocity of the target P is not zero. More specifically, the second processing section 34 detects a change in phase of peaks in the frequency spectrum of the beat signal SB. Here, the processing contents of the second processing unit 34 will be specifically described with reference to FIG.

FIG. 5 is a diagram showing the processing contents of the second processing unit 34. As shown in FIG. In FIG. 5 , the frequency spectrum of any one receiving antenna 21 out of the plurality of receiving antennas 21 is arranged in chronological order. FIG. 5 also shows an example of the results of distance FFT processing of temporally continuous beat signals B1 to B8 and phase changes of peaks between the beat signals B1 to B8. In the example shown in FIG. 5, there is a peak in the distance bin fr10 of each of the beat signals B1 to B8, and the phase of the peak changes.

Here, when the relative velocity between the target P and the radar device 1 is not zero, there is a phase change according to the Doppler frequency at the peak of the distance bin fr10 corresponding to the same target P among the beat signals B1 to B8. appear.

The second processing unit 34 arranges the frequency spectrum obtained by performing the distance FFT processing in time series and performs velocity FFT processing, thereby obtaining a frequency spectrum in which a peak appears in the frequency bin (velocity bin) for the Doppler frequency.

Further, as shown in FIG. 5, the second processing unit 34 performs velocity FFT processing for each distance bin fr over the entire range from distance bin fr1 to distance bin frm for the receiving antenna 21a. Then, for the other three receiving antennas 21b to 21d, the second processing unit 34 limits the range in which velocity FFT processing is performed based on the positions of peaks extracted by the peak extracting unit 35, which will be described later.

For example, as shown in FIG. 5, when the peak extraction unit 35 extracts a peak in the distance bin fr10, the second processing unit 34 performs the speed FFT processing limited to the distance bin fr10. That is, the second processing unit 34 does not perform velocity FFT processing on distance bins fr other than the peak distance bin fr10 extracted by the peak extraction unit 35 . This can minimize the amount of processing in the two-dimensional FFT processing.

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

If the extracted peak is the peak of the frequency spectrum corresponding to the receiving antenna 21a, the peak extractor 35 outputs information about the peak to the second processor 34. FIG. Further, when it is confirmed that peaks appear at the same position in the peak extraction results of all of the plurality of receiving antennas 21a to 21d, the peak extraction unit 35 outputs information about such peaks to the calculation unit 36. .

Note that the peak extraction unit 35 may prohibit output to the calculation unit 36, for example, when a peak does not appear at the same position in at least one of all peak extraction results. As a result, unreliable peaks can be removed, and erroneous detection of the target P can be prevented.

The calculator 36 calculates the distance, relative speed, and angle (azimuth) to the target P based on the peaks extracted by the peak extractor 35 .

Specifically, the calculator 36 derives the distance and the relative velocity to the target P based on the combination of the peak distance bin fr and velocity bin fv extracted by the peak extractor 35 .

Further, the calculation unit 36 estimates the angle at which the target P exists by performing predetermined angle calculation processing. Specifically, the calculator 36 calculates the angle of the target P based on the phase difference of the peaks of the same distance bin fr 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. When it is detected that a plurality of targets P are present in the same distance bin fr due to the difference in phase of the peaks of the same distance bin fr, angle estimation is performed for each of the plurality of targets P. FIG.

Note that the estimation of the angle 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). will be

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 amount of processing in the two-dimensional FFT processing will be explained using FIG. FIG. 6 is a diagram showing the amount of processing in two-dimensional FFT processing. "1 normal FCM" shown in FIG. 6 indicates the processing amount when distance FFT processing and velocity FFT processing are performed in all ranges, The amount of processing in the case of performing within 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 (the number of beat signals SB) is 64, and the number of peaks extracted by the peak extraction unit 35 is 10. , and the number of receiving antennas 21 is assumed to be four. Also, "the number of complex number multiplications" and "the number of complex number additions and subtractions" shown in FIG. Specifically, for the distance FFT, 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 times of addition and subtraction is β, β=P×LOG(P, 2)×N. Regarding the velocity FFT processing, when the number of complex number multiplications is α, the number of chirps is P, and the number of distance FFT bins is N, α = P/2 × LOG (P, 2) × N, and the number of complex additions and subtractions is 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 amount of processing (C and D in the figure) of distance FFT processing performed by the first processing unit 33 is the same. Also, the amount of processing (E and F in the figure) for one channel of the receiving antenna 21 in the velocity FFT processing performed by the second processing unit 34 is the same.

On the other hand, for the 3 channels of the other receiving antenna 21 in the velocity FFT processing performed by the second processing unit 34, "2 improved FCM" (G/100×3 ch) is higher than "1 normal FCM" (G×3 ch). Also, the amount of processing is small. This is because for the 3ch receiving antenna 21, only the distance bin fr corresponding to the peak is subjected to velocity FFT processing.

As a result, as shown in FIG. 6, the processing amount of "2 improved FCM" can be suppressed to about 70% (72%) of the processing amount of "1 normal FCM". Note that the "number of distance FFT bins", "number of chirps", "number of peaks", and "number of reception antennas" shown in FIG. 6 are examples, and arbitrary values may be set.

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

As shown in FIG. 7, the transmitter 10 first outputs a transmission wave SW including n chirp waves (step S101). Subsequently, the receiver 20 generates n beat signals SB from the chirp signal ST and the received signal SR corresponding to the reflected wave of the transmitted wave SW from 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 velocity FFT processing on the result of the distance FFT processing of any one of the plurality of receiving antennas 21 (step S104).

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

Subsequently, the calculation unit 36 performs calculation processing for calculating the distance, relative speed, and angle to the target P based on the peaks extracted by the peak extraction unit 35 (step S107). Subsequently, the output unit 37 outputs target object 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 device 1 according to the embodiment includes the receiving section 20, the FFT processing section (for example, the first processing section 33 and the second processing section 34), and the peak extraction section 35. The receiving unit 20 receives the reflected waves, which are the transmission waves whose frequencies continuously change and are reflected by the target P, with the plurality of receiving antennas 21 . When the FFT processing unit performs two-dimensional FFT processing on the beat signal SB based on the reflected wave received by an arbitrary receiving antenna 21 among the plurality of receiving antennas 21, the second-dimensional FFT processing is performed by the first do it in range. A peak extraction unit 35 extracts a peak corresponding to the target P from the frequency spectrum that is the result of processing by the FFT processing unit. Further, when the FFT processing unit performs two-dimensional FFT processing on the receiving antennas 21 other than the arbitrary receiving antenna 21, the second Second-dimensional FFT processing is performed in the range of . This can prevent the processing amount from increasing.

In the above-described embodiment, the speed FFT processing is performed after performing the distance FFT processing on the beat signal SB, but the processing order of the two-dimensional FFT processing may be reversed. That is, the radar device 1 may perform distance FFT processing after performing velocity FFT processing on the beat signal SB. Note that even if the order of processing is changed, the number of peaks obtained after the two-dimensional FFT processing and the positions of the peaks do not change. 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 showing a control method for the radar device 1 according to the modification. As shown in FIG. 8, the radar device 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 velocity FFT processing for each distance bin fr within the range of all distance bins fr1 to frm for the beat signal SB in the receiving antenna 21a. At this stage, the frequency spectrum resulting from the FFT processing does not have peaks identifying the velocity bins fv.

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 within the range of all beat signals B1 to Bn. As a result, a peak corresponding to the target P is obtained at a particular range bin fr10 and velocity bin fv5. That is, in the above-described embodiment, the second-dimensional FFT processing is velocity FFT processing, whereas in the modified example, the second-dimensional FFT processing is distance FFT processing. That is, in the modified example, the range of all beat signals B1 to Bn, which is the range of distance FFT processing, is the first range.

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

Subsequently, the first processing unit 33 performs distance FFT processing on the frequency spectrum generated by the second processing unit 34 in a second range obtained by limiting the first range. In the example shown in FIG. 8, the first processing unit 33 performs distance FFT processing using only the extracted peak velocity bin fv5 as the second range. As a result, it is possible to prevent the processing amount from increasing even when the processing order of the two-dimensional FFT processing is changed.

Regarding the processing order of the two-dimensional FFT processing in the other receiving antennas 21b to 21d, which processing order to adopt 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 showing the amount of processing in two-dimensional FFT processing according to the modification. '1 normal FCM' and '2 improved FCM' shown in FIG. 9 are processing orders in which velocity FFT processing is performed after distance FFT processing. "3 improved FCM" is a processing order in which distance FFT processing is performed after velocity FFT processing. FIG. 9 also shows a case where the number of peaks extracted by the peak extraction unit 35 is 10 and a case where the number of peaks is 60. As shown in FIG.

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

Specifically, this is because the increase in the amount of processing with respect to the increase in the number of peaks is greater in the "3-improved FCM" than in the "2-improved FCM."

In other words, if the number of peaks is less than a predetermined number, "3 improved FCM" has less throughput than "2 improved FCM", but as the number of peaks approaches the predetermined number, "2 improved FCM" and "3 improved FCM" ” becomes smaller.

Then, when the number of peaks is equal to or greater than a predetermined number, the "3-improved FCM" requires more processing than the "2-improved FCM". That is, the throughput 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 two-dimensional FFT processing in the processing 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 the predetermined number, the first processing unit 33 and the second processing unit 34 perform two-dimensional FFT processing in the processing order of "2 improved FCM".

In this way, the first processing unit 33 and the second processing unit 34 determine the processing order of the two-dimensional FFT processing depending on whether the number of peaks is equal to or greater than a predetermined number, thereby always minimizing the amount of processing. can be done.

The predetermined number described above is determined, for example, based on the "number of distance FFT bins", "number of chirps" and "number of reception antennas" shown in FIG.

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

That is, when the "number of distance FFT bins" is 64, the "number of chirps" is 1024, and the number of peaks is 10, the "2-improved FCM" requires the least amount of processing. In the case of 60, "3 improved FCM" has the lowest throughput.

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

Reference Signs List 1 radar device 2 vehicle control device 10 transmission unit 11 signal generation unit 12 oscillator 13 transmission antenna 20 reception unit 21, 21a to 21d reception antenna 22, 22a to 22d mixer 23, 23a to 23d A/D converter 30 processing unit 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 (2)

a receiving unit for receiving reflected waves of a transmission wave whose frequency continuously changes by a plurality of receiving antennas, which are reflected by a target;
a first-dimensional FFT processing unit for performing first-dimensional FFT processing in two-dimensional FFT processing on beat signals based on the reflected waves received by the plurality of receiving antennas;
An arbitrary second dimension in which second-dimensional FFT processing in the two-dimensional FFT processing is performed on a beat signal based on the reflected wave received by an arbitrary receiving antenna among the plurality of receiving antennas, in a first range of frequencies. an FFT processing unit;
a peak extraction unit for extracting a peak corresponding to the target from the frequency spectrum that is the result of processing by the arbitrary second-dimensional FFT processing unit;
For the receiving antennas other than the arbitrary receiving antenna, the second-dimensional FFT processing is performed on frequencies in a second range obtained by limiting the first range based on the position of the peak extracted by the peak extraction unit. and a second-dimensional FFT processing unit that performs
In the two-dimensional FFT processing, the processing order of the first processing in the distance direction corresponding to the distance to the target and the second processing in the speed direction corresponding to the relative speed of the target can be interchanged. There is
The first-dimensional FFT processing unit and the other second-dimensional FFT processing unit,
determining the processing order based on the number of the peaks extracted by the peak extraction unit when performing the two-dimensional FFT processing for the other receiving antenna;
A radar device characterized by: The other second-dimensional FFT processing unit,
2. The radar device according to claim 1, wherein said second FFT processing is performed with only said peak position as said second range.

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