JP2015049074A - Radar and object detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radar configured to separate/detect each object even when a sidelobe level of correlation characteristics is high, and an object detection method.SOLUTION: A speed/distance detection unit 35 detects a speed V and a distance R to an object, on the basis of a reflection wave sampled by a detection data acquisition unit 31. A subtraction signal generation unit 36 generates a subtraction signal formed by integrating a phase term including the speed V and the distance R in a complex amplitude A(V, R), on the basis of the detected speed V and distance R. A subtraction processing unit 37 subtracts the generated subtraction signal from the reflection wave sampled by the detection data acquisition unit 31. The speed/distance detection unit 35 detects a speed V and a distance R by using the reflection wave formed by subtracting the subtraction signal, as a new reflection wave. A sidelobe of the correlation characteristics is reduced, and interference between signals corresponding to each of the objects is reduced, thereby clarifying the signals to detect a smaller signal with high accuracy.

Description

  The present invention relates to a radar and an object detection method.

  A direct sequence spread spectrum (DS-SS) type radar has been proposed. As shown in FIG. 9, in a DS-SS radar, a transmission signal modulated by a code having a predetermined period of a predetermined sequence (for example, M sequence in FIG. 10) is repeatedly transmitted from the transmission unit 2. The detection data acquisition unit 3 acquires a sampling signal by performing equivalent time sampling with respect to each reflected wave of the transmission signal reflected by the object at a sampling period (N + 1) Tw. As shown in FIG. 11, in the multiplication unit 4, for the sampling signals in the code direction h = 0 to N−1 and the distance direction k = 0 to N−1 after the equivalent time sampling of the sampling period (N + 1) Tw, For each delay time (distance) k, compensation is performed with the same code using a complex conjugate product with the modulation code as a reference function. In the FFT unit 5, Fourier transformation is performed in the code direction for each distance k. Thereby, the speed / distance detection unit 6 obtains the speed (relative speed) V of the object for each distance R.

  For example, in Patent Document 1, means for transmitting a transmission signal including a predetermined code sequence to one or more target bodies, means for receiving a signal reflected by one or more target bodies, and received signals obtained at different times A DS-SS radar having means for calculating the sum and difference of the signals and calculating the Doppler frequency shift of the target object from the phase difference between the sum signal and the difference signal is disclosed.

JP 2008-232668 A

  However, in the above technique, when there are a plurality of targets having different velocities, there is a problem that the side lobe level of the correlation characteristic is high and interference between signals related to individual objects occurs, and improvement is desired.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a radar and an object detection method that can separate and detect individual objects even when the side lobe level of the correlation characteristic is high.

  The present invention relates to a transmission unit that repeatedly transmits a transmission signal modulated with a code, a detection data acquisition unit that samples a reflected wave of a transmission signal reflected by an object at a predetermined sampling period, and a detection data acquisition unit that performs sampling. Based on the reflected wave, a detection unit that detects the relative speed and distance from the object, and a phase term composed of the relative speed and distance in the complex amplitude is integrated based on the relative speed and distance detected by the detection unit. A subtracting signal generating unit that generates a subtracted signal, and a subtracting processing unit that subtracts the subtracted signal generated by the subtracting signal generating unit from the reflected wave sampled by the detection data acquiring unit. The radar detects a relative speed and a distance using a reflected wave obtained by subtracting a subtracted signal as a new reflected wave.

  According to this configuration, the transmission unit repeatedly transmits a transmission signal modulated with a code. The data acquisition unit for detection samples the reflected wave of the transmission signal reflected by the object at a predetermined sampling period. The detection unit detects a relative speed and a distance from the object based on the reflected wave sampled by the detection data acquisition unit. Thereby, an object can be detected. In addition, the subtraction signal generation unit generates a subtraction signal in which the phase term composed of the relative speed and the distance in the complex amplitude is integrated based on the relative speed and the distance detected by the detection unit. The subtraction processing unit subtracts the subtraction signal generated by the subtraction signal generation unit from the reflected wave sampled by the detection data acquisition unit. The detection unit detects the relative speed and the distance using the reflected wave obtained by subtracting the subtraction signal by the subtraction processing unit as a new reflected wave. As a result, the side lobe level of the correlation characteristic can be reduced, the interference between signals related to individual objects can be reduced, individual signals can be made clearer, and smaller signals can be detected with high accuracy.

  In this case, it is preferable that the detection unit detects the relative velocity and the distance based on a Fourier transform of a sample of the reflected wave sampled by the detection data acquisition unit and a code restored.

  According to this configuration, the detection unit detects the relative velocity and the distance of the object based on the Fourier transform of the reflected wave sample sampled by the detection data acquisition unit and the code restored. As a result, it is possible to obtain a true peak of the signal by performing frequency decomposition.

  In this case, the detection data acquisition unit acquires, as speed detection data for detecting the relative speed, data obtained by repeatedly sampling two or more locations of one code of each reflected wave of the transmission signal reflected by the object, The detection unit detects a relative speed based on the speed detection data acquired by the detection data acquisition unit, and the detection data acquisition unit transmits the reflected light to the object as distance detection data for detecting the distance. Distance detection data acquired by the detection data acquisition unit based on the relative velocity detected based on the velocity detection data, obtained by sampling the reflected wave of the signal with a sampling period that can restore the code The Doppler shift is compensated, the distance is detected based on the distance detection data compensated for the Doppler shift, and the subtraction signal generator is detected by the detector. Based on the relative speed and distance, a subtraction signal in which the phase term composed of the relative speed and distance is integrated in the complex amplitude is generated, and the subtraction processing unit acquires the subtraction signal generated by the subtraction signal generation unit as detection data. It is preferable to subtract from the distance detection data sampled by the unit, and the detection unit detects the distance using the distance detection data obtained by subtracting the subtraction signal by the subtraction processing unit as new distance detection data.

  According to this configuration, the detection data acquisition unit repeatedly samples two or more locations of one sign of each reflected wave of the transmission signal reflected on the object as speed detection data for detecting the relative speed. The detection unit acquires the relative speed based on the speed detection data acquired by the detection data acquisition unit. Thus, by increasing the number of samples, the S / N ratio can be improved and a smaller signal can be detected even if the same noise is included. Therefore, the detection unit detects the relative speed of the object based on the reflected wave sampled by the detection data acquisition unit, so that the relative speed of the farther object can be detected with higher accuracy.

  In addition, the detection data acquisition unit acquires, as distance detection data for detecting the distance, a sample of the reflected wave of the transmission signal reflected from the object sampled at a sampling period that can restore the code. Based on the relative speed detected based on the detection data, the Doppler shift of the distance detection data acquired by the detection data acquisition unit is compensated, and the distance is detected based on the distance detection data compensated for the Doppler shift. To do. Accordingly, the distance to the object can be detected based on the distance detection data that has been subjected to Doppler compensation at the relative speed detected with higher accuracy.

  Further, the subtraction signal generation unit generates a subtraction signal in which the phase term composed of the relative speed and the distance in the complex amplitude is integrated based on the relative speed and the distance detected by the detection unit. The subtraction signal generated by the signal generation unit is subtracted from the distance detection data sampled by the detection data acquisition unit, and the detection unit uses the distance detection data obtained by subtracting the subtraction signal by the subtraction processing unit as new distance detection data. As the distance is detected. As a result, the side lobe level of the correlation characteristic can be reduced, the interference between signals related to individual objects can be reduced, individual signals can be made clearer, and smaller signals can be detected with high accuracy.

  The present invention also provides a transmission step of repeatedly transmitting a transmission signal modulated with a code, a detection data acquisition step of sampling a reflected wave of a transmission signal reflected by an object at a predetermined sampling period, and a detection data acquisition step Based on the reflected wave sampled in step 1, the detection step detects the relative speed and distance to the object, and based on the relative speed and distance detected in the detection step, the phase term consisting of the relative speed and distance is integrated in the complex amplitude A subtracting signal generating step for generating a subtracted signal, and a subtracting step for subtracting the subtracted signal generated in the subtracting signal generating step from the reflected wave sampled in the detection data acquiring step. This is an object detection method for detecting a relative speed and a distance using a reflected wave obtained by subtracting a subtraction signal in a process as a new reflected wave.

  In this case, in the detection step, it is preferable to detect the relative speed and distance based on the Fourier transform of the reflected wave sample sampled by the detection data acquisition step.

  Further, in the detection data acquisition step, the data for detecting the relative speed is obtained by repeatedly sampling two or more locations of one sign of each reflected wave of the transmission signal reflected on the object and detecting it. In the process, the relative speed is detected based on the speed detection data acquired in the detection data acquisition process, and in the detection data acquisition process, the transmission reflected on the object is used as the distance detection data for detecting the distance. The distance detection data acquired in the detection data acquisition step is acquired based on the relative speed detected based on the speed detection data in the detection step by acquiring the reflected wave of the signal sampled at a sampling period that can restore the code. The Doppler shift is compensated, and the distance is detected based on the distance detection data compensated for the Doppler shift. Then, based on the relative velocity and distance detected in the detection step, a subtraction signal in which the phase term composed of the relative velocity and the distance is integrated in the complex amplitude is generated. In the subtraction processing step, the subtraction signal is generated in the subtraction signal generation step. The subtraction signal is subtracted from the distance detection data sampled in the detection data acquisition step. In the detection step, the distance detection data obtained by subtracting the subtraction signal in the subtraction processing step is used as new distance detection data to detect the distance. Is preferred.

  According to the radar and the object detection method of the present invention, individual objects can be separated and detected even when the side lobe level of the correlation characteristic is high.

It is a block diagram which shows the DS-SS radar of 1st Embodiment. It is a figure which shows the sampling timing of the reflected wave according to the distance of the object of 1st Embodiment. (A) to (f) show the results of the simulation of the DS-SS radar of the first embodiment, (a) shows the speed bin and distance bin before the subtraction process, and (b) shows the speed before the subtraction process. (C) shows the detection result of the distance before the subtraction process, (d) shows the speed bin and the distance bin after the subtraction process, and (e) shows the detection result of the speed after the subtraction process. , (F) shows the distance detection result after the subtraction process. It is a block diagram which shows the DS-SS radar of 2nd Embodiment. It is a figure which shows the signal processing of DS-SS radar of 2nd Embodiment. It is a figure which shows the subtraction process of DS-SS radar of 2nd Embodiment. It is a figure which shows the subtraction signal according to the distance of the object in 2nd Embodiment. (A)-(d) shows the result of the simulation of the DS-SS radar of the second embodiment, (a) shows the detection result of the distance of the target 1 before the subtraction process, and (b) shows the result before the subtraction process. The detection result of the distance of the target 2 is shown, (c) shows the detection result of the distance of the target 1 after the subtraction process, and (d) shows the detection result of the distance of the target 2 after the subtraction process. It is a block diagram which shows the conventional DS-SS radar. It is a figure which shows the signal transmitted with DS-SS radar. It is a figure which shows the signal processing of the conventional DS-SS radar. (A)-(d) is a graph which shows the signal processing result about one target without noise, (a) (b) shows a speed characteristic, (c) (d) shows a distance characteristic. It is a graph which shows the frequency spectrum of the transmission signal in code length N = 127, and the received signal after a Doppler shift. It is a table | surface which shows the parameter of the short-distance mode and the expected performance of the radar in the simulation of the conventional DS-SS radar. It is a table | surface which shows the conditions and result of the simulation of the conventional DS-SS radar. Condition No. 1 in FIG. 2 is a graph showing the results of 1 simulation. (A)-(d) shows condition No. of FIG. (A) shows the speed bin for target 1; (b) shows the distance bin for target 1; (c) shows the speed bin for target 2; (D) shows the distance bin for target 2. It is a graph which shows the reception power before A / D sampling.

  An example of a radar and an object detection method according to an embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, the DS-SS radar 10 of the first embodiment of the present invention includes a transmission unit 21, a detection data acquisition unit 31, a multiplication unit 32, an FFT unit 33, a peak search DFT unit 34, a speed / distance. A detection unit 35, a subtraction signal generation unit 36, and a subtraction processing unit 37 are provided.

  As shown in FIG. 10, the transmission unit 21 continuously and repeatedly transmits a signal whose phase is code-modulated with an M-sequence code for each chip. The chip width of one chip of the signal is Tw, the code length of codes n = 0 to N−1 included in the signal is N, and the period m = 0 to M−1 with respect to the observation time Tc required for one signal processing Let M be the number.

  As shown in FIG. 11, the detection data acquisition unit 31 performs sampling by performing equivalent time sampling with respect to each reflected wave of the transmission signal reflected on each target object at a sampling period (N + 1) Tw. A signal is acquired.

  As shown in FIG. 11, the multiplier 32 performs the sampling signal of the code direction h = 0 to N−1 and the distance direction k = 0 to N−1 after sampling the equivalent time of the sampling period (N + 1) Tw. For each delay time (distance) k, compensation is performed with the same code using a complex conjugate product with the modulation code as a reference function.

  The FFT unit 33 performs a Fourier transform in the code direction for each distance k.

  The peak search DFT unit 34 performs DFT on the range of 1 bin before and after the peak frequency number of the Doppler frequency detected from the FFT speed estimation result in order to reduce the target speed estimation error when performing the subtraction process. The target speed V is estimated.

  Accordingly, the speed / distance detection unit 35 obtains the speed (relative speed) V and the complex amplitude A (V, R) of the object for each distance R. As shown in FIG. 2, the sampling timing of measurement differs according to the target distance.

Based on the velocity V and the distance R detected by the velocity / distance detector 35, the subtraction signal generator 36 calculates the complex amplitude A (V, R) from the velocity V and the distance R based on the following equation (1). A subtraction signal in which the phase term is integrated is generated. As a result, reception signals from the individual targets detected in a pseudo manner are generated.

  The subtraction processing unit 37 subtracts the subtraction signal generated by the subtraction signal generation unit 36 from the original signal acquired by the detection data acquisition unit 31, and uses the subtracted signal as the next input. The multiplication unit 32, the FFT unit 33, the peak search DFT unit 34, and the speed / distance detection unit 35 use the reflected wave obtained by subtracting the subtraction signal by the subtraction processing unit as the next new reflected wave, and the other target velocity V and The distance R is detected.

  In the present embodiment, the transmission unit 21 repeatedly transmits a transmission signal modulated with a code. The detection data acquisition unit 31 samples the reflected wave of the transmission signal reflected by the object at a predetermined sampling period. The FFT unit 33, the peak search DFT unit 34, and the speed / distance detection unit 35 detect the velocity V and the distance R with the object based on the reflected wave sampled by the detection data acquisition unit 31. Thereby, an object can be detected. Further, the subtraction signal generator 36 integrates the phase term composed of the speed V and the distance R in the complex amplitude A (V, R) based on the speed V and the distance R detected by the speed / distance detector 35. Generate a subtraction signal. The subtraction processing unit 37 subtracts the subtraction signal generated by the subtraction signal generation unit 36 from the reflected wave sampled by the detection data acquisition unit 31. The FFT unit 33, the peak search DFT unit 34, and the speed / distance detection unit 35 detect the velocity V and the distance R using the reflected wave obtained by subtracting the subtraction signal by the subtraction processing unit 37 as a new reflected wave. As a result, the side lobe level of the correlation characteristic can be reduced, the interference between signals related to individual objects can be reduced, individual signals can be made clearer, and smaller signals can be detected with high accuracy.

  In addition, according to the present embodiment, the FFT unit 33, the peak search DFT unit 34, and the speed / distance detection unit 35 perform a Fourier transform of the reflected wave sample sampled by the detection data acquisition unit 31. Based on the converted data, the speed V and the distance R of the object are detected. As a result, it is possible to obtain a true peak of the signal by performing frequency decomposition.

  Hereinafter, a second embodiment of the present invention will be described. The DS-SS radar 100 of this embodiment includes a transmission unit 121, a speed detection data acquisition unit 131, an FFT unit 132, a sample direction non-coherent addition unit 133, a peak search DFT unit 134, a speed detection unit 135, and distance detection data. An acquisition unit 141, a Doppler compensation unit 142, a multiplication unit 143, a code direction coherent addition unit 144, a distance detection unit 145, a subtraction signal generation unit 146, and a subtraction processing unit 147 are provided.

  As in the first embodiment, the transmitter 121 continuously and repeatedly transmits a signal whose phase is modulated with an M-sequence code for each chip as shown in FIG. As described above, the chip width of one chip of the signal is Tw, the code length of codes n = 0 to N−1 included in the signal is N, and the period m = 0 to the observation time Tc required for one signal processing. Let M be the number of cycles of M-1.

As shown in FIG. 5, the speed detection data acquisition unit 131 responds to the reflected wave of the transmission signal reflected by the object, as shown in FIG. Equivalent time sampling is performed on the received signal in the interval of (1), with sp interval samples (where the code length is smaller than N, and sp is preferably a power of 2). As a result, sp pieces of sampling data having the same code at the sampling interval N are obtained. That is, in this embodiment, in order to improve the S / N, a plurality of sampling data with the same code at the sampling interval N is obtained by repeatedly sampling two or more locations of one code of the reflected wave. With respect to one code, sampling data of at least 2 chips is obtained, and sampling data of all chips is obtained at most. Here, since the code length of the M-sequence code is not a power of 2 ⁿ −1 and 2, when performing equivalent time sampling, it is preferable to delay the sampling acquisition timing by one chip for each period.

  As shown in FIG. 5, the FFT unit 132 performs discrete Fourier transform in the direction of the number of periods m for the sampling data of the same code after the equivalent time sampling, and obtains speed estimation results for the number of samples.

  As shown in FIG. 5, the sample direction non-coherent addition unit 133 performs addition of each power, that is, non-coherent addition, on the speed estimation result for the number of samples after the discrete Fourier transform in the period m direction.

  The peak search DFT unit 134 calculates the Doppler frequency peak frequency number detected from the velocity estimation result after non-coherent addition in the sample direction in order to reduce the estimation error of the relative velocity of the object when performing Doppler compensation in the distance estimation. The relative velocity of the object is estimated by discrete Fourier transform for the front and rear 1 bin range.

  The velocity detection unit 135 outputs the relative velocity of the object estimated by the discrete Fourier transform, and transmits the relative velocity to the Doppler compensation unit 42. In the present embodiment, when the speed detection unit 135 uses the complex amplitude of the speed estimation section to generate the subtraction signal as described later, the speed detection unit 135 determines the relative speed of the object estimated by the subtraction signal generation unit 146. Send.

  As shown in FIG. 5, the distance detection data deriving unit 141 is equivalent to the received signal in the interval of the distance estimation interval observation time Tc_R and the period Mr (= N), as shown in FIG. Time sampling is performed with N + 1 interval samples to obtain sampling data in the code direction.

  The reception signal of equivalent time sampling is influenced by the Doppler shift, and the phase becomes discontinuous in the time direction. Therefore, as shown in FIG. 5, the Doppler compensation unit 142 performs Doppler compensation using information on the target speed obtained by the speed detection unit 135.

  As shown in FIG. 5, the multiplication unit 143 multiplies the received signal after Doppler compensation by multiplying the M-sequence code, which is a reference function of the transmission signal, by shifting the distance delay by one chip, and performs code compensation.

  As shown in FIG. 5, the code direction coherent addition unit 144 performs coherent addition of the number of samples Mr in the code direction on the received signal after multiplication.

  The distance detection unit 145 outputs the distance of the object obtained by the coherent addition in the code direction. As will be described later, when the complex amplitude of the speed estimation section is used for generation of the subtraction signal, the distance detection unit 145 transmits the estimated relative speed of the object to the subtraction signal generation unit 146.

The subtraction signal generation unit 146 is based on the velocity V obtained from the velocity detection unit 135, the distance R obtained from the distance detection unit 145, and the complex amplitude A (R) after the distance estimation as shown in FIG. As shown in the following equation (2), a subtracted signal in which the phase term composed of the velocity V and the distance R is integrated in the complex amplitude A (R) is generated. As a result, reception signals from the individual targets detected in a pseudo manner are generated.

Alternatively, in the present embodiment, the subtraction signal generation unit 146 uses the velocity V, the distance R, and the complex amplitude A (V) after the velocity estimation to calculate the velocity in the complex amplitude A (V) as shown in the following equation (3). A subtraction signal in which a phase term composed of V and distance R is integrated is generated. As a result, reception signals from the individual targets detected in a pseudo manner are generated.

  As shown in FIG. 6, the subtraction processing unit 147 performs distance estimation processing similar to the above-described conventional DS-SS system for the detected target number K speeds obtained from the speed estimation result, and corresponds to the distance. All targets whose distances are detected are collectively subtracted, and distance estimation is performed again using the subtracted distance detection data as the next new distance detection data.

  According to the present embodiment, the speed detection data acquisition unit 131 repeatedly samples two or more portions of one code of the reflected wave of each transmission signal reflected on the object as speed detection data for detecting the relative speed. The sample direction non-coherent addition unit 133, the peak search DFT unit 134, and the speed detection unit 135 detect the relative speed based on the speed detection data acquired by the speed detection data acquisition unit 131. Thus, by increasing the number of samples, the S / N ratio can be improved and a smaller signal can be detected even if the same noise is included. Therefore, the speed detection unit 135 can detect the relative speed of a farther object with higher accuracy by detecting the relative speed of the object based on the reflected wave sampled by the speed detection data acquisition unit 131. it can.

  Further, the distance detection data acquisition unit 141 acquires, as distance detection data for detecting the distance, a sample of the reflected wave of the transmission signal reflected from the object sampled at a sampling period capable of restoring the code, and a Doppler compensation unit 142, the code direction coherent addition unit 144 and the distance detection unit 145 compensate the Doppler shift of the distance detection data acquired by the distance detection data acquisition unit 141 based on the relative speed detected based on the speed detection data. The distance is detected based on the distance detection data compensated for the Doppler shift. Accordingly, the distance to the object can be detected based on the distance detection data that has been subjected to Doppler compensation at the relative speed detected with higher accuracy.

  Further, the subtraction signal generation unit 146 generates a subtraction signal in which the phase term composed of the relative speed and the distance is integrated in the complex amplitude based on the relative speed and the distance detected by the speed detection unit 135 and the distance detection unit 145. Then, the subtraction processing unit 147 subtracts the subtraction signal generated by the subtraction signal generation unit 146 from the distance detection data sampled by the distance detection data acquisition unit 141, and the code direction non-coherent addition unit 144 and the distance detection unit 145 The distance is detected using the distance detection data obtained by subtracting the subtraction signal by the subtraction processing unit 147 as new distance detection data. As a result, the side lobe level of the correlation characteristic can be reduced, the interference between signals related to individual objects can be reduced, individual signals can be made clearer, and smaller signals can be detected with high accuracy.

  Hereinafter, simulation results for the DS-SS radar 10 of the first embodiment shown in FIG. 1 will be shown. As an example of the processing result, the simulation results when the signal power difference between the two targets is about 30 dB are shown in FIGS. In this simulation, target 1 distance R1 = 10 m, target 1 speed V1 = 30 km / h, target 2 distance R2 = 50 m, target 2 speed V2 = 40 km / h, signal power difference between target 1 and target 2 S1 / S2 = 30 dB and no noise.

  In order to verify the improvement of the floor level by the subtraction processing, the detection target error Rerror = 0 m, Verr = 0 km / h, and the loss of the amplitude was also made lossless. It can be seen that the floor level before subtraction is about 31 dB, and after the subtraction process, the side lobe level of the correlation characteristic is improved by about 61 dB corresponding to the two target signal power differences S1 / S2.

  Moreover, the simulation result about DS-SS radar 100 of 2nd Embodiment shown in FIG. 4 is shown. As an example of the processing result, the simulation results when the signal power difference between the two targets is about 40 dB are shown in FIGS. In this simulation, target 1 distance R1 = 10 m, target 1 speed V1 = 30 km / h, target 2 distance R2 = 100 m, target 2 speed V2 = 60 km / h, signal power difference between target 1 and target 2 S1 / S2 = 40 dB and no noise. By performing the subtraction process, it can be seen that the floor level for the target 2 whose signal power is 40 dB smaller is improved to about 62 dB and the target is detected.

  Next, for comparison, simulation results for the conventional DS-SS radar 1 shown in FIG. 9 are shown. First, FIG. 12A to FIG. 12D show the processing results under the condition that one target object without noise exists. The code length N = 127. As shown in FIGS. 12A to 12D, the floor is lowered in the speed bin corresponding to the target distance / speed and the distance bin, and the side lobe level of the correlation characteristic is obtained at the distance / speed where the target does not exist. It is confirmed that 10 log (127) ≈21 dB depending on the code length is high. As these factors, since the phase after multiplication becomes discontinuous at a distance where the target does not exist, it is conceivable that the target Doppler component is diffused as noise in the distance where the target does not exist.

  FIG. 13 shows the result of discrete Fourier transform of the transmission signal at the code length N = 127 and the reception signal after Doppler shift. FIG. 13 shows that the transmission signal has a filter characteristic that lowers only frequency number 0, and the frequency spectrum after Doppler shift of frequency number 10 has only frequency number 10 lowered. From this, it can be considered that the target Doppler component diffuses as noise even at a speed where the target does not exist. The S / N improvement capability in this method depends on the S / N improvement gain by FFT, and is expected to be 10 log (N) (about 33 dB when the code length N = 2047).

  Next, a simulation for detecting two objects was performed in the conventional DS-SS radar 1. The radar parameters and expected performance are shown in FIG. 14, and the simulation conditions are shown in FIG. In the simulation of the conventional DS-SS radar 1, two targets are arranged at a distance of 10 m and a distance of 100 m, respectively, and simulation was performed with and without consideration of distance attenuation (−40 dB). . The noise was SNR = 0 dB, −10 dB, and −20 dB. FIG. 15 shows the results of S / N improvement under each simulation condition. The threshold for target detection was set to S / Nmin = 13 dB, which is the minimum S / N for target detection, and an object exceeding this threshold was detected. For reference, simulation condition no. The results of 5 are shown in FIGS. 16 and 17A to 17D. From FIG. 15, it is difficult for the DS-SS radar 10 of the present embodiment to detect the distance, but the target detection is performed under the condition that the possible distance attenuation is considered (−40 dB). It turns out that even target detection is difficult.

  The received power before A / D sampling in the conventional DS-SS radar 1 is shown in FIG. At this time, the gain of the transmission / reception antenna, the radar reflection cross-sectional area RCS between the vehicle and the human, and the signal processing gain were the same values as in the maximum detection distance calculation in the conventional DS-SS radar 1 described above. In addition, the isolation of transmission wave leakage was set to 50 dB. FIG. 18 shows that the target signal is buried below the noise at a distance that is less than or equal to the intersection of the reflected power of the car or human and the noise power after signal processing. Further, since the side lobe level of the correlation characteristic of the conventional DS-SS radar 1 is 33 dB, in a multi-target environment with a target power difference larger than this, a weak signal is present in the side lobe of the target correlation characteristic of the strong signal. May be buried.

  In addition, this invention is not limited to the said embodiment, A various deformation | transformation aspect is possible.

  DESCRIPTION OF SYMBOLS 1 ... DS-SS radar, 2 ... Transmission part, 3 ... Data acquisition part for detection, 4 ... Multiplication part, 5 ... FFT part, 6 ... Speed / distance detection part, 10 ... DS-SS radar, 21 ... Transmission part, 31 ... Data acquisition unit for detection, 32 ... Multiplication unit, 33 ... FFT unit, 34 ... Peak search DFT unit, 35 ... Speed / distance detection unit, 36 ... Subtraction signal generation unit, 37 ... Subtraction processing unit, 100 ... DS- SS radar, 121 ... transmission unit, 131 ... speed detection data acquisition unit, 132 ... FFT unit, 133 ... sample direction non-coherent addition unit, 134 ... peak search DFT unit, 135 ... speed detection unit, 141 ... distance detection data Acquisition unit, 142 ... Doppler compensation unit, 143 ... multiplication unit, 144 ... code direction coherent addition unit, 145 ... distance detection unit, 146 ... subtraction signal generation unit, 147 ... subtraction processing unit.

Claims (6)

A transmitter that repeatedly transmits a transmission signal modulated by a code;
A data acquisition unit for detection that samples a reflected wave of the transmission signal reflected by an object at a predetermined sampling period;
Based on the reflected wave sampled by the detection data acquisition unit, a detection unit that detects a relative speed and distance from the object;
A subtraction signal generation unit that generates a subtraction signal in which a phase term composed of the relative speed and the distance is integrated in a complex amplitude based on the relative speed and the distance detected by the detection unit;
A subtraction processing unit that subtracts the subtraction signal generated by the subtraction signal generation unit from the reflected wave sampled by the detection data acquisition unit;
With
The radar is a radar that detects the relative speed and the distance using the reflected wave obtained by subtracting the subtraction signal by the subtraction processing unit as the new reflected wave.   The detection unit detects the relative velocity and the distance based on a Fourier transform of a sample of the reflected wave sampled by the detection data acquisition unit and the code restored. The radar described in 1. The detection data acquisition unit acquires, as velocity detection data for detecting the relative velocity, a sample obtained by repeatedly sampling two or more locations of one of the reflected waves of each of the transmission signals reflected on the object. And
The detection unit detects the relative speed based on the speed detection data acquired by the detection data acquisition unit,
The detection data acquisition unit acquires, as distance detection data for detecting the distance, a sample obtained by sampling the reflected wave of the transmission signal reflected by the object at a sampling period capable of restoring the code,
The detection unit compensates for the Doppler shift of the distance detection data acquired by the detection data acquisition unit based on the relative speed detected based on the speed detection data, and the Doppler shift is compensated for Based on the distance detection data, the distance is detected,
The subtraction signal generation unit generates a subtraction signal in which a phase term composed of the relative speed and the distance is integrated in a complex amplitude based on the relative speed and the distance detected by the detection unit,
The subtraction processing unit subtracts the subtraction signal generated by the subtraction signal generation unit from the distance detection data sampled by the detection data acquisition unit,
The radar according to claim 1 or 2, wherein the detection unit detects the distance using the distance detection data obtained by subtracting the subtraction signal by the subtraction processing unit as new distance detection data. A transmission step of repeatedly transmitting a transmission signal modulated with a code;
A detection data acquisition step of sampling a reflected wave of the transmission signal reflected by an object at a predetermined sampling period;
A detection step of detecting a relative speed and distance from the object based on the reflected wave sampled in the detection data acquisition step;
A subtraction signal generating step for generating a subtraction signal in which phase terms composed of the relative velocity and the distance are integrated in a complex amplitude based on the relative velocity and the distance detected in the detection step;
A subtraction processing step of subtracting the subtraction signal generated in the subtraction signal generation step from the reflected wave sampled in the detection data acquisition step;
With
In the detection step, the relative velocity and the distance are detected by using the reflected wave obtained by subtracting the subtraction signal in the subtraction processing step as the new reflected wave.   5. The detection step detects the relative velocity and the distance based on a Fourier transform of a sample of the reflected wave sampled by the detection data acquisition step and the code restored. The object detection method described in 1. In the detection data acquisition step, as the speed detection data for detecting the relative speed, data obtained by repeatedly sampling two or more locations of one of the reflected waves of each of the transmission signals reflected on the object is acquired. And
In the detection step, the relative speed is detected based on the speed detection data acquired in the detection data acquisition step,
In the detection data acquisition step, the distance detection data for detecting the distance is acquired by sampling the reflected wave of the transmission signal reflected by the object with a sampling period that can restore the code,
In the detection step, based on the relative speed detected based on the speed detection data, the Doppler shift of the distance detection data acquired in the detection data acquisition step is compensated, and the Doppler shift is compensated for Based on the distance detection data, the distance is detected,
In the subtraction signal generation step, based on the relative speed and the distance detected in the detection step, a subtraction signal in which a phase term composed of the relative speed and the distance is integrated in a complex amplitude is generated,
In the subtraction processing step, the subtraction signal generated in the subtraction signal generation step is subtracted from the distance detection data sampled in the detection data acquisition step,
The object detection method according to claim 4 or 5, wherein, in the detection step, the distance is detected using the distance detection data obtained by subtracting the subtraction signal in the subtraction processing step as new distance detection data.