Millimeter wave traffic radar weak target DBF enhancement detection method

Abstract

The invention discloses a millimeter wave traffic radar weak target DBF enhancement detection method. The method comprises the following steps: determining the number of DBF times, the angle of each DBF and the angle range independently covered by DBF beams corresponding to different DBF angles according to a to-be-enhanced detection area and DBF beam width; acquiring detection matrixes corresponding to different DBF beams from the adc data corresponding to each DBF channel according to the detection area needing to be enhanced, the number of DBF times and the angle of each DBF; performing target detection and screening on the detection matrixes corresponding to the different DBF beams according to angle ranges independently covered by the DBF beams corresponding to the different DBF angles; carrying out target detection on other detection areas except the detection area needing to be enhanced through other detection methods; and carrying out combination and parameter estimation on the targets detected by the detection matrix corresponding to each DBF beam and the targets detected by other detection algorithms except for the detection area needing to be enhanced. According to the method, the detection probability of a target with relatively weak echo signals can be obviously improved.

Description

Technical Field

[0001] The present invention relates to the technical field of millimeter wave radars, and in particular to a method for enhancing DBF detection of weak targets by millimeter wave traffic radars. Background Art

[0002] Millimeter wave radar plays an extremely important role in the field of intelligent transportation. It transmits frequency modulated continuous wave (FMCW) signals and receives and processes the target's reflected echo signals to obtain the target's distance, speed, and angle information.

[0003] In the existing millimeter wave radar technology, the radar uses multiple transmitters (TX) and multiple receivers (RX) to form a multiple input multiple output (MIMO) array. Each TX transmits multiple chirp signals, and each chirp signal includes multiple sampling points to form a 2D signal. When processing the signal, the mixed signal of the received signal and the transmitted signal is first processed by a 2D fast Fourier transform (FFT) to complete the range-Doppler (RD) focusing and obtain the RD spectrum of the signal. Then, the multi-channel RD spectrum is non-coherently accumulated, and finally the non-coherently accumulated spectrum is used for CFAR detection to achieve the purpose of detecting the target.

[0004] However, in the current methods of target detection in RD spectrum, the target signal-to-noise ratio has not been improved to the maximum extent. In particular, weak targets at long distances are easily missed because the signal-to-noise ratio does not reach the detection threshold, resulting in a reduction in the overall detection power. For this reason, Texas Instruments (TI) officially proposed a method to further increase the angle dimension FFT on the basis of RD to improve the target signal-to-noise ratio. However, this method has a huge amount of calculations, which will cause serious time consumption for ordinary signal processors, thereby reducing system performance.

[0005] The information disclosed in this background technology section is only intended to deepen the understanding of the overall background technology of the present invention, and should not be regarded as acknowledging or suggesting in any form that the information constitutes the prior art already known to those skilled in the art. Summary of the invention

[0006] In view of the problems existing in the prior art, the purpose of the present invention is to provide a DBF enhanced detection method for weak targets of millimeter-wave traffic radar. The method is applied to a millimeter-wave radar comprising a multiple-input multiple-output (MIMO) array consisting of multiple transmitters (TX) and multiple receivers (RX). The method can effectively overcome the defects of traditional RD spectrum non-coherent accumulation detection, maximize the detectability-to-noise ratio of the target, and effectively improve the detection capability of long-distance weak targets. In addition, compared with the 3DFFT detection algorithm officially introduced by TI, the method provided by the present invention effectively saves the amount of calculation.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for DBF enhanced detection of weak targets by millimeter wave traffic radar, the method comprising the following steps:

[0009] S1: Determine the number of DBFs, the angle of each DBF, and the angle range covered by the DBF beams corresponding to different DBF angles according to the detection area to be enhanced and the DBF beam width;

[0010] S2: according to the detection area to be enhanced, the number of DBFs and the angle of each DBF, the detection matrix corresponding to different DBF beams is obtained from the adc data corresponding to each DBF channel;

[0011] S3: performing target detection and screening on the detection matrices corresponding to the different DBF beams according to the angle ranges individually covered by the DBF beams corresponding to the different DBF angles;

[0012] S4: performing target detection on other detection areas except the detection area to be enhanced by other detection methods;

[0013] S5: Merge and estimate parameters of the targets detected by the detection matrix corresponding to each DBF beam and the targets detected by other detection algorithms except the detection area that needs to be enhanced.

[0014] Further, the specific implementation method of step S1 is as follows:

[0015] S11: Determine the full angle range of the required DBF coverage according to the lateral left boundary, lateral right boundary, and longitudinal closest distance boundary of the detection area to be enhanced in the radar coordinate system;

[0016] S12: Determine the number of DBFs, the angle of each DBF, and the angle range covered by each DBF according to the total angle range covered by the required DBF and the width of each DBF beam.

[0017] Furthermore, the radar coordinate system refers to a rectangular coordinate system established with the radar as the origin, the radar illumination normal as the vertical axis, the radar illumination direction as the positive direction of the vertical axis, the radar section as the horizontal axis, and the right direction of the section as the positive direction of the horizontal axis.

[0018] Further, the specific implementation method of step S2 is as follows:

[0019] S21: performing fast Fourier transform processing on the ADC data corresponding to each DBF channel in the range dimension and the Doppler dimension respectively to obtain the range-Doppler spectrum corresponding to each DBF channel;

[0020] S22: Calculate the RD spectrum distance unit range to be enhanced by each DBF according to the detection area to be enhanced;

[0021] S23: obtaining a steering vector for each DBF according to the position of each DBF channel relative to the reference channel and the angle of each DBF;

[0022] S24: Determine the value of the detection matrix corresponding to each DBF beam at each distance unit and each Doppler unit within the range of the distance unit in the RD spectrum to be enhanced by each DBF according to the RD spectrum corresponding to each DBF channel, the steering vector of each DBF, and the amplitude and phase calibration factors of each DBF channel, and obtain the detection matrix corresponding to each DBF.

[0023] Further, the DBF channel refers to a channel used for DBF enhancement, including a uniform array or a sparse array consisting of all or part of the receiving channels of the system, all or part of the transmitting channels of the system, and all or part of the virtual channels of the system;

[0024] The reference channel is any transmitting channel, receiving channel or virtual channel;

[0025] The RD spectrum corresponding to each DBF channel refers to a two-dimensional matrix including the distance dimension and the Doppler dimension obtained by performing FFT of the distance dimension and the Doppler dimension on the adc data of each DBF channel in sequence; the adc data of each channel includes N chirp Chirp signals, each chirp signal contains Nadc sampling points;

[0026] The distance dimension refers to the dimension of the fast time signal formed by the N adc sampling points of each chirp in the adc data, and the Doppler dimension refers to N chirp The dimension of the slow-time signal composed of the sampling points at the same position in the chirp signal.

[0027] Further, the specific implementation method of step S3 is as follows:

[0028] S31: performing target detection on the detection matrix corresponding to each DBF beam respectively, and the detection algorithms include unit average constant false alarm detection (CA-CFAR) and ordered statistical constant false alarm detection (OS-CFAR);

[0029] S32: performing angle estimation for each target detected by the detection matrix corresponding to each DBF beam;

[0030] S33: Target screening is performed according to the angle estimation result of each target detected in the detection matrix corresponding to each DBF beam and the angle range individually covered by the DBF beam corresponding to each DBF angle; if the angle estimation result of the target is within the angle range individually covered by the beam corresponding to the corresponding DBF detection matrix, the target is retained, otherwise the target is deleted.

[0031] Furthermore, the parameter estimation in step S5 includes target distance estimation, target speed estimation, target angle estimation, and target coordinate estimation in the radar coordinate system.

[0032] By adopting the above technical solution, the present invention has the following beneficial effects:

[0033] (1) Compared with the traditional 2DFFT detection scheme, the present invention can significantly improve the detection probability of targets with relatively weak echo signals. Whether the problem of weak target signals is caused by the small radar cross-section (RCS) of the target itself or the design defects of radar hardware, the technical solution of the present invention can be used to improve its detection signal-to-noise ratio, effectively improve the detection probability, improve the continuity of the trace, and make it easier for the subsequent tracking module to achieve stable tracking of the target.

[0034] (2) Compared with the 3DFFT detection solution officially provided by TI, the technical solution provided by the present invention significantly reduces the amount of processing operations and effectively saves processing time. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0036] Figure 1 The present invention provides a flow chart of a method for DBF enhanced detection of weak targets by millimeter-wave traffic radar.

[0037] Figure 2 The figure is a comparison diagram of the detection point trace effects of the DBF enhanced detection method for weak targets of a millimeter-wave traffic radar described in the present invention and the traditional 2DFFT detection method. DETAILED DESCRIPTION

[0038] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0040] Combination Figure 1FIG. 1 is a flow chart of a method for DBF enhanced detection of weak targets by a millimeter-wave traffic radar proposed by the present invention, which specifically includes the following steps:

[0041] Step S1: Determine the number of DBFs, the angle of each DBF, and the angle range covered by the DBF beams corresponding to different DBF angles according to the detection area to be enhanced and the DBF beam width, which specifically includes the following steps:

[0042] Step S11: Determine the angle range [θmin, θmax] required for DBF coverage according to the left boundary abscissa, right boundary abscissa, and nearest boundary ordinate of the detection area to be enhanced in the radar coordinate system: θmin=atand(Xmin / Ymin) is the minimum value of the angle range required for DBF coverage, and θmax=atand(Xmax / Ymin) is the maximum value of the angle range required for DBF coverage, wherein Xmin represents the abscissa of the left boundary of the detection area to be enhanced in the radar coordinate system, Xmax represents the abscissa of the right boundary of the detection area to be enhanced in the radar coordinate system, and Ymin represents the ordinate of the nearest boundary of the detection area to be enhanced in the radar coordinate system;

[0043] Step S12: Determine the DBF times NDBF, the angle of each DBF, and the angle range of the beam coverage corresponding to different DBF angles according to the required DBF coverage angle range [θmin, θmax] and the width θw of each DBF beam: The DBF times can be expressed as in represents rounding up; the angle θi of the i-th DBF can be expressed as θ i =θ min +θ w / 2+(i-1)·θ w , the range of the beam corresponding to the DBF angle θi is [θ min +(i-1)·θ w ,θ min +i·θ w ], where i = 1, 2,…, N.

[0044] After determining the number of DBFs, the angle of each DBF, and the angle range covered by the beams corresponding to different DBF angles, step S2 can be performed: according to the area, number of DBFs, and angle of each DBF that need to be enhanced, the detection matrix corresponding to different DBF beams is obtained from the ADC data corresponding to each DBF channel. The specific acquisition steps are as follows:

[0045] Step S21: performing fast Fourier transform (FFT) processing on the adc data of each DBF channel in the range dimension and the Doppler dimension respectively to obtain a range-Doppler (RD) spectrum corresponding to each DBF channel;

[0046] Step S22: Calculate the minimum value I of the RD spectrum distance unit range to be enhanced by DBF each time according to the detection area to be enhanced. R_min and the maximum value I R_max :I R_min =round(R min / R res ), I R_max =round(R max / R res ), where Rmin and Rmax represent the nearest and farthest radial distances of the detection area to be enhanced, respectively.

[0047] Step S23: Obtain the steering vector of each DBF according to the position of each DBF channel relative to the reference channel and the angle of each DBF. For example, the DBF angle is θi (i=1, 2, ..., N DBF ) is the DBF steering vector A i =[A i,1 ,A i,2 ,...,A i,Nch ], where A i,k =exp[j2πD k / λ·sinθ i ],k=1,2,...,N ch , D k (k=1,2,...Nch) represents the position of the kth DBF channel relative to the reference channel, N ch Indicates the number of DBF channels. DBF A total of N DBF angles are generated DBF A steering vector.

[0048] Step S24: Determine the value of the detection matrix corresponding to each DBF beam at each distance unit and each Doppler unit within the range of the distance unit in the RD spectrum to be enhanced by each DBF according to the RD spectrum corresponding to each DBF channel, the steering vector of each DBF, and the amplitude and phase calibration factors of each DBF channel, and obtain the detection matrix corresponding to each DBF. The specific method is as follows: for distance unit I r (I r ∈[I R_min ,I R_max ]), Doppler unit I d (I d=1,2,…,Ndop), it is necessary to extract the RD spectrum of each DBF channel in the distance unit I r , Doppler unit I d The corresponding complex value is calibrated with amplitude and phase to form a vector B = [B 1 ,B 2 ,...,B Nch ], where B k Indicates that from the kth (k=1,2,...,N ch ) distance unit I extracted from the RD spectrum of the DBF channel r , Doppler unit I d The corresponding complex value; when the DBF angle is θi (i=1,2,...,N DBF ), the corresponding DBF steering vector A i When A i Multiply with the conjugate of vector B (or A i The conjugate of is multiplied with the conjugate of vector B) and summed to get C i After the modulus is calculated, other numerical operations can be performed, and the result is used as the DBF angle θi (i=1,2,...,N DBF ) corresponds to the distance unit I in the DBF detection matrix r -I R_min +1. Doppler unit I d The value at the position; all distance units and Doppler units are processed according to the above method, and N is obtained. DBF N corresponding to the angle DBF A DBF detection matrix.

[0049] The DBF channel refers to a channel used for DBF enhancement, including but not limited to a uniform array or a sparse array consisting of all or part of the system's receiving channels, all or part of the system's transmitting channels, all or part of the system's virtual channels, etc.

[0050] The reference channel may be any transmitting channel, receiving channel or virtual channel.

[0051] It should be noted that the RD spectrum of each channel refers to a two-dimensional matrix including the distance dimension and the Doppler dimension obtained by performing FFT of the adc data of each channel in sequence. chirp Chirp signals, each chirp signal contains Nadc sampling points. The distance dimension refers to the dimension of the fast time signal formed by the Nadc sampling points of each chirp in the adc data, and the Doppler dimension refers to N chirpThe dimension of the slow-time signal composed of the sampling points at the same position in the chirp signal.

[0052] After obtaining the detection matrix corresponding to each DBF beam, step S3 can be performed: according to the angle range covered by the DBF beams corresponding to the different DBF angles, target detection and screening are performed on the detection matrix corresponding to each DBF beam. Specifically, it includes:

[0053] Step S31: DBF The detection matrices corresponding to the DBF beams are used to detect targets respectively. The detection algorithms include but are not limited to unit average constant false alarm detection (CA-CFAR), ordered statistical constant false alarm detection (OS-CFAR), etc.

[0054] Step S32: Angle estimation is performed for each target detected by the detection matrix corresponding to each DBF beam. Specifically, it can be divided into two steps: (1) When performing angle estimation, it is necessary to first extract the complex value of the target in the RD spectrum corresponding to each angle measurement channel according to the distance of the target in the detection matrix and the Doppler unit to obtain the angle measurement input signal; (2) An angle measurement algorithm is then used to perform angle estimation on the angle measurement input signal. The angle measurement algorithm includes but is not limited to DBF algorithm, angle-dimensional FFT algorithm, MUSIC super-resolution algorithm, etc. The angle measurement channel includes but is not limited to a uniform array or a sparse array composed of all or part of the system's receiving channels, all or part of the system's transmitting channels, all or part of the system's virtual channels, etc.

[0055] Step S33: Target screening is performed based on the angle estimation result of each target detected by the detection matrix corresponding to each DBF beam and the beam coverage angle range of the corresponding DBF detection matrix. The specific method is as follows: When the DBF angle is θ i (i=1,2,...,N DBF ), the corresponding DBF beam coverage angle range can be obtained from step S1 as [θ min +(i-1)·θ w ,θ min +i·θ w ], for the DBF angle θi (i=1,2,...,N DBF ) when the detection matrix detects the target, if its angle estimation result θ est In the interval [θ min +(i-1)·θ w ,θ min +i·θ w ], the target will be retained, otherwise it will be deleted.

[0056] In addition to performing the above-mentioned detection steps on the detection area to be enhanced, optionally, step S4 can also be performed: performing target detection on other detection areas by other detection methods, and the other detection areas include all detection areas except the detection area to be enhanced, and the other detection methods may be all possible detection methods except the detection methods given in the technical solution of the present invention.

[0057] After completing the target detection in the above steps, step S5 can be performed: merging the targets detected by each DBF detection matrix with the targets in other areas detected by other detection algorithms and performing parameter estimation, including distance estimation, speed estimation, etc., which will not be described in detail here.

[0058] Attached Figure 2 The comparison chart of the results of using the technical solution of the present invention and the existing 2DFFT detection technical solution to process the same set of radar raw ADC data in actual scenes is given. Figure 2 (a) shows the actual scene, Figure 2 (b) is the detection point trace diagram using the existing 2DFFT detection scheme; Figure 2 (c) is a detection point trace diagram using the technical solution of the present invention; by comparing the attached Figure 2 (b) and Figure 2 (c) The results show that, in the 800m-1000m distance range, the target points detected by the technical solution of the present invention are significantly higher than those of the existing 2DFFT detection solution.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for DBF enhanced detection of weak targets by millimeter wave traffic radar, characterized in that: The method comprises the following steps: S1: Determine the number of DBFs, the angle of each DBF, and the angle range covered by the DBF beams corresponding to different DBF angles according to the detection area to be enhanced and the DBF beam width; S2: according to the detection area to be enhanced, the number of DBFs and the angle of each DBF, the detection matrix corresponding to different DBF beams is obtained from the adc data corresponding to each DBF channel; S3: performing target detection and screening on the detection matrices corresponding to the different DBF beams according to the angle ranges individually covered by the DBF beams corresponding to the different DBF angles; S4: performing target detection on other detection areas except the detection area to be enhanced by other detection methods; S5: Merge and estimate parameters of the targets detected by the detection matrix corresponding to each DBF beam and the targets detected by other detection algorithms except the detection area that needs to be enhanced.

2. The method for DBF enhanced detection of weak targets by millimeter wave traffic radar according to claim 1, characterized in that: The specific implementation method of step S1 is as follows: S11: Determine the full angle range of the required DBF coverage according to the lateral left boundary, lateral right boundary, and longitudinal closest distance boundary of the detection area to be enhanced in the radar coordinate system; S12: Determine the number of DBFs, the angle of each DBF, and the angle range covered by each DBF according to the total angle range covered by the required DBF and the width of each DBF beam.

3. The method for DBF enhanced detection of weak targets by millimeter wave traffic radar according to claim 2 is characterized in that: The radar coordinate system refers to a rectangular coordinate system established with the radar as the origin, the radar illumination normal as the vertical axis, the radar illumination direction as the positive direction of the vertical axis, the radar section as the horizontal axis, and the right direction of the section as the positive direction of the horizontal axis.

4. The method for DBF enhanced detection of weak targets by millimeter wave traffic radar according to claim 1, characterized in that: The specific implementation method of step S2 is as follows: S21: performing fast Fourier transform processing on the ADC data corresponding to each DBF channel in the range dimension and the Doppler dimension respectively to obtain the range-Doppler spectrum corresponding to each DBF channel; S22: Calculate the RD spectrum distance unit range to be enhanced by each DBF according to the detection area to be enhanced; S23: obtaining a steering vector for each DBF according to the position of each DBF channel relative to the reference channel and the angle of each DBF; S24: Determine the value of the detection matrix corresponding to each DBF beam at each distance unit and each Doppler unit within the range of the distance unit in the RD spectrum to be enhanced by each DBF according to the RD spectrum corresponding to each DBF channel, the steering vector of each DBF, and the amplitude and phase calibration factors of each DBF channel, and obtain the detection matrix corresponding to each DBF.

5. The method for DBF enhanced detection of weak targets by millimeter wave traffic radar according to claim 4, characterized in that: The DBF channel refers to a channel used for DBF enhancement, including a uniform array or a sparse array consisting of all or part of the receiving channels of the system, all or part of the transmitting channels of the system, and all or part of the virtual channels of the system; The reference channel is any transmitting channel, receiving channel or virtual channel; The RD spectrum corresponding to each DBF channel refers to a two-dimensional matrix including the distance dimension and the Doppler dimension obtained by performing FFT of the distance dimension and the Doppler dimension on the adc data of each DBF channel in sequence; the adc data of each channel includes N chirp Chirp signals, each chirp signal contains Nadc sampling points; The distance dimension refers to the dimension of the fast time signal formed by the N adc sampling points of each chirp in the adc data, and the Doppler dimension refers to the N chirp The dimension of the slow-time signal composed of the sampling points at the same position in the chirp signal.

6. The method for DBF enhanced detection of weak targets by millimeter wave traffic radar according to claim 1, characterized in that: The specific implementation method of step S3 is as follows: S31: performing target detection on the detection matrix corresponding to each DBF beam respectively, and the detection algorithms include unit average constant false alarm detection (CA-CFAR) and ordered statistical constant false alarm detection (OS-CFAR); S32: performing angle estimation for each target detected by the detection matrix corresponding to each DBF beam; S33: Target screening is performed according to the angle estimation result of each target detected in the detection matrix corresponding to each DBF beam and the angle range individually covered by the DBF beam corresponding to each DBF angle; If the angle estimation result of the target is within the angle range covered by the beam corresponding to the corresponding DBF detection matrix, the target is retained, otherwise the target is deleted.

7. The method for DBF enhanced detection of weak targets by millimeter wave traffic radar according to claim 1, characterized in that: The parameter estimation in step S5 includes target distance estimation, target speed estimation, target angle estimation, and target coordinate estimation in the radar coordinate system.

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