Radar signal processing method and apparatus based on chirp redundant ddm waveform, and medium

Abstract

The application discloses a radar signal processing method and system based on a chirp redundant DDM waveform, and a storage medium. The method comprises the following steps: transmitting a chirp redundant DDM waveform in a parity sequence corresponding to a chirp sequence, receiving and obtaining an intermediate frequency signal according to a return signal and a reference signal; determining a first 2D FFT result of a sampling signal of the intermediate frequency signal and a second 2D FFT result of the parity sequence, performing CFAR detection on the first 2D FFT result to obtain a target detection result; based on the target detection result, resolving velocity ambiguity according to a phase difference between transmission phases of the odd sequence segment and the even sequence segment; obtaining target attribute information according to the 2D FFT result in the spatial dimension; and converting an index number corresponding to the target detection result into target distance information, target velocity information and target angle information according to the target attribute information. The application introduces the chirp redundant DDM waveform to realize target detection, and improves the efficiency of channel separation in the process of target detection by the MIMO radar.

Description

Technical Field

[0001] This application relates to, but is not limited to, the field of MIMO radar target detection technology, and in particular to a radar signal processing method, system, and storage medium based on chirp redundant DDM waveforms. Background Technology

[0002] MIMO radar utilizes multiple antennas to transmit and receive signals, processing multi-dimensional information to expand the radar's effective aperture, thereby achieving high-precision target detection and tracking. During target detection and tracking using MIMO radar, different antennas occupy different Doppler frequency bands, leading to frequency band aliasing as velocity changes. This results in an unpredictable frequency band order occupied by the transmitting antennas, necessitating channel separation. Currently, a common channel separation method involves using DDM modulation to create a gap in the signal to locate one of the transmitting antennas. However, detecting this gap requires cyclic band correlation detection for each detected target, resulting in a large computational load. Furthermore, the extra Doppler frequency band occupied by the gap reduces utilization, thus affecting the efficiency of channel separation. Summary of the Invention

[0003] This application provides a radar signal processing method, apparatus, and medium based on chirp redundant DDM waveforms, which can effectively improve the efficiency of channel separation during the detection and tracking of targets by MIMO radar.

[0004] In a first aspect, embodiments of this application provide a radar signal processing method based on chirp redundant DDM waveforms, including:

[0005] Obtain the chirp sequence and divide the chirp sequence into odd and even sequences. The delay time length between each sequence segment of the odd and even sequences is determined according to a preset speed defuzzification rule.

[0006] Chirp redundant DDM waveforms are transmitted in different sequence segments respectively, the echo signals of the chirp redundant DDM waveforms are received, and the echo signals and a preset reference signal are frequency-modulated to obtain an intermediate frequency signal.

[0007] Perform a fast time-dimensional Fourier transform on the sampled signal corresponding to the intermediate frequency signal to obtain the first 2dFFT result;

[0008] Slow-time Fourier transforms are performed on the odd sequence segments and even sequence segments in the odd-even sequence respectively to obtain the second 2dFFT result;

[0009] The first 2dFFT result is noncoherently accumulated according to the receiving channel and CFAR detection is performed to obtain the target detection result. The first 2dFFT result is the 2dFFT result of single antenna transmission.

[0010] Based on the target detection results, the first emission phase of the second 2dFFT result corresponding to the odd sequence segment is determined, and the second emission phase of the second 2dFFT result corresponding to the even sequence segment is determined. The velocity ambiguity is then resolved based on the phase difference between the first emission phase and the second emission phase.

[0011] Based on the Doppler index number corresponding to each target object in the target detection result, the third transmit phase of the corresponding receiving channel is determined in the first 2dFFT result, and the antenna position information corresponding to the first 2dFFT result is determined.

[0012] Based on the third transmission phase and the antenna position information, the data corresponding to the target object in the first 2dFFT result are rearranged and subjected to angular Fourier transform to obtain the spatial spectrum of the target object;

[0013] CFAR detection is performed on the 2dFFT results of the spatial dimension to obtain target attribute information;

[0014] Based on the target attribute information, the index number corresponding to the target detection result is converted into target distance information, target speed information, and target angle information.

[0015] In some embodiments, the target detection result includes a target cell index number, which is obtained according to the following steps:

[0016] In each of the cells to be detected in the second 2dFFT result, a preset number of protection cells are skipped and a reference background region range is determined from the cells to be detected;

[0017] The statistical characteristics of the background noise are calculated using the reference cells corresponding to the reference background region, and the approximate distribution of the background noise is obtained based on the statistical characteristics of the background noise.

[0018] The threshold value of the current reference unit is determined based on the approximate distribution of the background noise and the preset false alarm rate. The threshold value is compared with the reference signal value corresponding to the current reference unit. The reference unit corresponding to the reference signal value that is higher than the threshold value is determined as the target unit.

[0019] The index number corresponding to the target unit is determined as the target unit index number.

[0020] In some embodiments, the method further includes:

[0021] Obtain the first reference index number of each target object in the second 2dFFT result;

[0022] The difference between each receiving channel is calculated based on the first reference index number and the phase relationship of DDM modulation.

[0023] Calculate the target index number corresponding to each transmitting antenna based on the difference between the various receiving channels;

[0024] Calculate the peak point corresponding to each of the target index numbers.

[0025] In some embodiments, the chirp redundancy DDM waveform includes a first redundant chirp waveform and a second redundant chirp waveform. The first redundant chirp waveform is a redundant chirp waveform transmitted individually using a single transmit antenna, and the second redundant chirp waveform is a chirp waveform transmitted simultaneously by all transmit antennas according to the DDM modulation rules. The expression for the second redundant chirp waveform is:

[0026]

[0027] Among them, S m Let f be the transmitted waveform of the m-th transmitting antenna, t be the transmission time, n be the number of pulses transmitted at the moment, and f be the transmitted waveform of the m-th transmitting antenna. c T is the carrier frequency. c Where k is the MIMO pulse repetition time, and k is the sweep slope. This represents the transmission start phase corresponding to the m-th transmitting antenna. The DDM phase modulated by the m-th transmitting antenna. The expression is:

[0028]

[0029] Where, N Tx This represents the total number of transmitting antennas.

[0030] In some embodiments, the expression for the phase difference between the first transmission phase and the second transmission phase is:

[0031]

[0032] in, The phase of the second 2dFFT result corresponding to the odd sequence segment at position (i, j) is the first emission phase. The second 2dFFT result corresponding to the even sequence segment is the phase at position (i, j), i.e., the second emission phase, where v is the target's true velocity, and t is the phase of the second 2dFFT result at position (i, j). d f is the additional delay length between the redundant chirp waveform and the DDMchirp waveform. c T is the carrier frequency. r The period of a single pulse.

[0033] In some embodiments, the expression for the target's true velocity v is:

[0034] v = v amb +qv max ;

[0035] Among them, v amb The blur velocity is obtained by detecting the index number using CFAR, where q is the reference blur factor, and v is the blur velocity. max The maximum unambiguous velocity, v, is determined by the MIMO pulse repetition period. max The expression is:

[0036]

[0037] Where λ is the carrier wavelength, c is the speed of light, and f c For carrier frequency.

[0038] In some embodiments, the target attribute information includes an estimated target velocity ambiguity factor, which is obtained according to the following formula:

[0039]

[0040] in, This is an estimate of the fuzzy multiple of the target velocity. This is the phase difference value after winding. The following formula is used to obtain:

[0041]

[0042] Among them, v amb The blur rate is obtained by detecting the index number using CFAR.

[0043] In some embodiments, the expression for the Doppler index number is:

[0044]

[0045] Where, N d N represents the Doppler FFT points. Tx The number of transmitting antennas, The value is an integer.

[0046] Secondly, embodiments of this application provide a radar signal processing system based on chirp redundant DDM waveforms, including: a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the radar signal processing method based on chirp redundant DDM waveforms as described in the first aspect.

[0047] Thirdly, embodiments of this application also provide a computer-readable storage medium storing computer-executable instructions for performing the radar signal processing method based on chirp redundant DDM waveforms as described in the first aspect.

[0048] This application provides a radar signal processing method, system, and storage medium based on chirp redundant DDM waveforms. The method includes: acquiring a chirp sequence; dividing the chirp sequence into odd and even sequences, wherein the delay time length between each sequence segment of the odd and even sequences is determined according to a preset velocity deambiguity rule; transmitting chirp redundant DDM waveforms in each different sequence segment; receiving the echo signals of the chirp redundant DDM waveforms; and performing frequency modulation processing on the echo signals and a preset reference signal to obtain an intermediate frequency (IF) signal; performing a fast time-dimensional Fourier transform on the sampled signal corresponding to the IF signal to obtain a first 2dFFT result; performing a slow time-dimensional Fourier transform on the odd and even sequence segments of the odd and even sequences to obtain a second 2dFFT result; performing incoherent accumulation of the first 2dFFT result according to the receiving channel and performing CFAR detection to obtain a target detection result; and based on the target... The target detection results are used to determine the first transmission phase of the second 2dFFT result corresponding to the odd sequence segment and the second transmission phase of the second 2dFFT result corresponding to the even sequence segment. Velocity ambiguity is resolved based on the phase difference between the first and second transmission phases. Based on the Doppler index number corresponding to each target object in the target detection results, the third transmission phase of the corresponding receiving channel is determined in the first 2dFFT result, and the antenna position information corresponding to the first 2dFFT result is determined. According to the third transmission phase and the antenna position information, the data corresponding to the target object in the first 2dFFT result is rearranged and subjected to an angle-dimensional Fourier transform to obtain the spatial spectrum of the target object. CFAR detection is performed on the 2dFFT result in the spatial dimension to obtain target attribute information. Based on the target attribute information, the index number corresponding to the target detection result is converted into target range information, target velocity information, and target angle information. This embodiment of the application achieves target detection by introducing chirp redundant DDM waveforms, which can effectively improve the efficiency of channel separation during the detection and tracking of targets by MIMO radar. Attached Figure Description

[0049] Figure 1 This is a flowchart of the steps of a radar signal processing method based on chirp redundant DDM waveform provided in one embodiment of this application;

[0050] Figure 2 This is a flowchart of the steps for obtaining the target unit index number provided in another embodiment of this application;

[0051] Figure 3 This is a flowchart of the channel separation method provided in another embodiment of this application;

[0052] Figure 4 This is a flowchart of the steps for resolving velocity ambiguity provided in another embodiment of this application;

[0053] Figure 5 This is a structural diagram of a radar signal processing system based on chirp redundant DDM waveforms provided in another embodiment of this application;

[0054] Figure 6 This is a schematic diagram of a multi-antenna transmission waveform provided in another embodiment of this application;

[0055] Figure 7 This is a schematic diagram of a second 2dFFT result provided in another embodiment of this application, where the coordinates are distance and velocity;

[0056] Figure 8 This is a schematic diagram of the first 2dFFT result provided in another embodiment of this application, with coordinates representing distance and velocity;

[0057] Figure 9 This is a schematic diagram of a second 2dFFT result provided in another embodiment of this application, where the coordinates are distance and velocity index numbers;

[0058] Figure 10 This is a schematic diagram of the first 2dFFT result provided in another embodiment of this application, with coordinates representing distance and velocity index numbers;

[0059] Figure 11 This is a channel phase diagram rearranged by coordinates after channel separation, provided in another embodiment of this application;

[0060] Figure 12 This is a schematic diagram of the angle-dimensional FFT result provided in another embodiment of this application;

[0061] Figure 13 This is a schematic diagram of a second 2dFFT result provided in another embodiment of this application, where the coordinates are distance and velocity;

[0062] Figure 14 This is a schematic diagram of the first 2dFFT result provided in another embodiment of this application, with coordinates representing distance and velocity;

[0063] Figure 15 This is a schematic diagram of a second 2dFFT result provided in another embodiment of this application, where the coordinates are distance and velocity index numbers;

[0064] Figure 16This is a schematic diagram of the first 2dFFT result provided in another embodiment of this application, with coordinates representing distance and velocity index numbers;

[0065] Figure 17 This is a channel phase diagram rearranged by coordinates after channel separation, provided in another embodiment of this application;

[0066] Figure 18 This is a schematic diagram of the angle-dimensional FFT result provided in another embodiment of this application. Detailed Implementation

[0067] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0068] It is understandable that although functional modules are divided in the device schematic diagram and a logical order is shown in the flowchart, in some cases, the steps shown or described may be performed in a different order than the module division in the device or the order in the flowchart. The terms "first," "second," etc., in the specification, claims, or the aforementioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0069] Currently, MIMO radar utilizes multiple antennas to transmit and receive signals, processing multi-dimensional information to expand the radar's effective aperture, thereby achieving high-precision target detection and tracking. During target detection and tracking using MIMO radar, different antennas occupy different Doppler frequency bands, leading to frequency band aliasing as velocity changes. This results in an unpredictable frequency band order occupied by the transmitting antennas, necessitating channel separation. A commonly used channel separation method is to create a gap in the signal using DDM modulation to locate one of the transmitting antennas. However, detecting this gap requires cyclic band correlation detection for each detected target, resulting in a large computational load. Furthermore, the extra space occupied by the gap reduces Doppler frequency band utilization, thus affecting the efficiency of channel separation.

[0070] To address the aforementioned problems, this application provides a radar signal processing method, system, and storage medium based on chirp redundant DDM waveforms. The method includes: acquiring a chirp sequence; dividing the chirp sequence into odd and even sequences, wherein the delay time length between each sequence segment of the odd and even sequences is determined according to a preset velocity deambiguity rule; transmitting chirp redundant DDM waveforms in each different sequence segment; receiving the echo signals of the chirp redundant DDM waveforms; and performing frequency modulation processing on the echo signals and a preset reference signal to obtain an intermediate frequency (IF) signal; performing a fast time-dimensional Fourier transform on the sampled signal corresponding to the IF signal to obtain a first 2dFFT result; performing a slow time-dimensional Fourier transform on the odd and even sequence segments of the odd and even sequences to obtain a second 2dFFT result; and performing incoherent accumulation of the first 2dFFT result according to the receiving channel and performing CFAR detection to obtain a target detection result. Based on the target detection results, the first transmission phase of the second 2dFFT result corresponding to the odd sequence segment is determined, and the second transmission phase of the second 2dFFT result corresponding to the even sequence segment is determined. Velocity ambiguity is resolved based on the phase difference between the first and second transmission phases. Based on the Doppler index number corresponding to each target object in the target detection results, the third transmission phase of the corresponding receiving channel is determined in the first 2dFFT result, and the antenna position information corresponding to the first 2dFFT result is determined. Based on the third transmission phase and the antenna position information, the data corresponding to the target object in the first 2dFFT result is rearranged and subjected to an angle-dimensional Fourier transform to obtain the spatial spectrum of the target object. CFAR detection is performed on the 2dFFT result in the spatial dimension to obtain target attribute information. Based on the target attribute information, the index number corresponding to the target detection result is converted into target range information, target velocity information, and target angle information. This embodiment of the application achieves target detection by introducing chirp redundant DDM waveforms, which can effectively improve the efficiency of channel separation during the detection and tracking of targets by MIMO radar.

[0071] The embodiments of this application will be further described below with reference to the accompanying drawings.

[0072] like Figure 1 As shown, Figure 1 This is a flowchart illustrating the steps of a radar signal processing method based on a chirp-redundant DDM waveform according to an embodiment of this application. This application provides a radar signal processing method based on a chirp-redundant DDM waveform, which includes, but is not limited to, the following steps:

[0073] Step S101: Obtain the chirp sequence and divide the chirp sequence into odd and even sequences. The delay time length between each sequence segment of the odd and even sequences is determined according to the preset speed defuzzification rule.

[0074] Step S102: Transmit chirp redundant DDM waveforms in different sequence segments, receive echo signals of chirp redundant DDM waveforms, and perform frequency modulation processing on the echo signals and preset reference signals to obtain intermediate frequency signals.

[0075] Step S103: Perform a fast time-dimensional Fourier transform on the sampled signal corresponding to the intermediate frequency signal to obtain the first 2dFFT result;

[0076] Step S104: Perform slow-time Fourier transform on the odd sequence segment and the even sequence segment in the odd-even sequence respectively to obtain the second 2dFFT result;

[0077] Step S105: The first 2dFFT result is noncoherently accumulated according to the receiving channel and CFAR detection is performed to obtain the target detection result. The first 2dFFT result is the 2dFFT result of single antenna transmission.

[0078] Step S106: Based on the target detection results, determine the first emission phase of the second 2dFFT result corresponding to the odd sequence segment, and determine the second emission phase of the second 2dFFT result corresponding to the even sequence segment, and perform velocity ambiguity resolution based on the phase difference between the first emission phase and the second emission phase.

[0079] Step S107: Based on the Doppler index number corresponding to each target object in the target detection result, determine the third transmission phase of the corresponding receiving channel in the first 2dFFT result, and determine the antenna position information corresponding to the first 2dFFT result;

[0080] Step S108: Based on the third transmission phase and antenna position information, rearrange the data corresponding to the target object in the first 2dFFT result and perform an angle-dimensional Fourier transform to obtain the spatial spectrum of the target object.

[0081] Step S109: Perform CFAR detection on the 2dFFT result of the spatial dimension to obtain the target attribute information;

[0082] Step S110: Convert the index number corresponding to the target detection result into target distance information, target velocity information, and target angle information based on the target attribute information.

[0083] It should be noted that the chirp redundancy DDM waveform in the embodiments of this application includes a first redundant chirp waveform and a second redundant chirp waveform. The first redundant chirp waveform is a redundant chirp waveform transmitted individually using a single transmit antenna, and the second redundant chirp waveform is a chirp waveform transmitted simultaneously by all transmit antennas according to the DDM modulation rules. The expression for the second redundant chirp waveform is:

[0084]

[0085] Among them, S m Let f be the transmitted waveform of the m-th transmitting antenna, t be the transmission time, n be the number of pulses transmitted so far, and f be the transmitted waveform of the m-th transmitting antenna. c T is the carrier frequency. c Where k is the MIMO pulse repetition time, and k is the sweep slope. This represents the transmission start phase corresponding to the m-th transmitting antenna. The DDM phase modulated by the m-th transmitting antenna. The expression is:

[0086]

[0087] Where, N Tx This represents the total number of transmitting antennas.

[0088] It should be noted that, in some embodiments, the expression for the phase difference between the first transmission phase and the second transmission phase is:

[0089]

[0090] in, Let (i,j) be the phase of the second 2dFFT result corresponding to the odd sequence segment at position (i,j), i.e., the first emission phase. The phase of the second 2dFFT result corresponding to the even sequence segment at position (i,j), i.e., the second emission phase, t d f is the additional delay length between the redundant chirp waveform and the DDMchirp waveform. c T is the carrier frequency. r Let v be the period of a single pulse, and v be the target's true velocity. The expression for v is:

[0091] v = v amb +qv max ;

[0092] Among them, v amb The blur velocity is obtained by detecting the index number using CFAR, where q is the reference blur factor, and v is the blur velocity. max The maximum unambiguous velocity, v, is determined by the MIMO pulse repetition period.max The expression is:

[0093]

[0094] Where λ is the carrier wavelength, c is the speed of light, and f c For carrier frequency.

[0095] It should be noted that the embodiments of this application do not limit the specific content of the target attribute information, and may include an estimated value of the target velocity ambiguity factor, which is obtained according to the following formula:

[0096]

[0097] in, The target velocity fuzzy factor estimate. This is the phase difference value after winding. The following formula is used to obtain:

[0098]

[0099] Among them, v amb The blur rate is obtained by detecting the index number using CFAR.

[0100] In addition, the target attribute information in the embodiments of this application may also include the target object's distance information, speed information, azimuth information, pitch index information, and speed ambiguity factor, which can be determined by those skilled in the art according to the actual situation.

[0101] It should be noted that the reference signal in this embodiment is a waveform signal without DDM modulation, and the signal bandwidth, rise time, fall time, and other parameters of this waveform signal are the same as those of the transmitted signal. Furthermore, in the slow-time Fourier transform, the two transmitted waveforms need to be FFTed separately. For the redundant chirp waveform transmitted by a single antenna, its 2dFFT result only contains the target peak value corresponding to that transmitting antenna. For the DDM-modulated chirp waveform transmitted by multiple antennas, its 2dFFT result contains the target peak values ​​corresponding to all transmitting antennas, with the peak values ​​of different transmitting antennas occupying different Doppler frequency bands.

[0102] It is understood that the radar signal processing method based on chirp redundant DDM waveforms in this application includes acquiring a chirp sequence, dividing the chirp sequence into odd and even sequences, and determining the delay time length between each sequence segment of the odd and even sequences according to a preset velocity deambiguity rule; transmitting chirp redundant DDM waveforms in each different sequence segment, receiving the echo signals of the chirp redundant DDM waveforms, and performing frequency modulation processing on the echo signals and a preset reference signal to obtain an intermediate frequency signal; performing a fast time-dimensional Fourier transform on the sampled signal corresponding to the intermediate frequency signal to obtain a first 2dFFT result; performing a slow time-dimensional Fourier transform on the odd sequence segment and the even sequence segment in the odd and even sequences respectively to obtain a second 2dFFT result; performing incoherent accumulation of the first 2dFFT result according to the receiving channel, and performing CFAR detection to obtain a target detection result. The first 2dFFT result is the 2dFFT result of a single antenna transmission. The FFT results are used to determine the first transmit phase of the second 2dFFT result corresponding to the odd sequence segment and the second transmit phase of the second 2dFFT result corresponding to the even sequence segment. Velocity ambiguity is then resolved based on the phase difference between the first and second transmit phases. Based on the Doppler index number corresponding to each target object in the target detection results, the third transmit phase of the corresponding receiving channel is determined in the first 2dFFT result, and the antenna position information corresponding to the first 2dFFT result is also determined. Based on the third transmit phase and antenna position information, the data corresponding to the target object in the first 2dFFT result is rearranged and subjected to an angle-dimensional Fourier transform to obtain the spatial spectrum of the target object. CFAR detection is performed on the spatial dimension 2dFFT result to obtain target attribute information. Based on the target attribute information, the index number corresponding to the target detection result is converted into target range information, target velocity information, and target angle information. This application embodiment achieves target detection by introducing chirp redundant DDM waveforms. Compared with existing TDM waveforms, chirp redundant DDM waveforms can significantly improve the velocity measurement range and have good orthogonality between channels. Compared with the empty band positioning channel separation method of DDM waveforms, it has lower computational load and higher Doppler bandwidth utilization, thereby effectively improving the efficiency of channel separation and target detection in the process of MIMO radar detecting and tracking targets.

[0103] Additionally, in some embodiments, the target detection result includes the target unit index number, as referenced. Figure 2 Obtaining the target cell index number includes, but is not limited to, the following steps:

[0104] Step S210: In each cell to be detected in the second 2dFFT result, skip a preset number of guard cells and determine the range of the reference background region from the cells to be detected.

[0105] Step S220: Calculate the statistical characteristics of the background noise using the reference cells corresponding to the reference background region range, and obtain the approximate distribution of the background noise based on the statistical characteristics of the background noise.

[0106] Step S230: Determine the threshold value of the current reference unit based on the approximate distribution of background noise and the preset false alarm rate; compare the threshold value with the reference signal value corresponding to the current reference unit; and determine the reference unit corresponding to the reference signal value that is higher than the threshold value as the target unit.

[0107] Step S240: Determine the index number corresponding to the target unit as the target unit index number.

[0108] It is understandable that performing CFAR detection to obtain target detection results refers to selecting the 2dFFT results of redundant single-transmit antennas, i.e., the second 2dFFT result. First, in each unit to be detected in the second 2dFFT result, a preset number of guard units are skipped, and a reference background region is determined from the units to be detected. The reference background region can be a cross-shaped window or a rectangular window. The statistical characteristics of the background noise are calculated using the reference units corresponding to the reference background region, i.e., the average (CA-CFAR) / median (OS-CFAR) / maximum and second-largest values ​​(GO-CFAR) of N reference units, thus obtaining an approximate distribution of the background noise. Based on the approximate distribution of the background noise and a preset false alarm rate, a threshold value for the current reference unit is determined. The threshold value is compared with the reference signal value corresponding to the current reference unit, and the reference unit corresponding to the reference signal value higher than the threshold value is determined as the target unit. The index number of the CFAR detection result on the redundant chirp is the location of the real target, and the index number corresponding to the target unit is determined as the target unit index number.

[0109] Additionally, refer to Figure 3 This application also provides a channel separation method, which includes, but is not limited to, the following steps:

[0110] Step S310: Obtain the first reference index number of each target object in the second 2dFFT result;

[0111] Step S320: Calculate the difference between each receiving channel based on the first reference index number and the phase relationship of DDM modulation;

[0112] Step S330: Calculate the target index number corresponding to each transmitting antenna based on the difference between each receiving channel;

[0113] Step S340: Calculate the peak point corresponding to each target index number.

[0114] It is understandable that, since the first reference index number corresponds to the second 2dFFT result, the parity sequence of the chirp sequence corresponding to the second 2dFFT result introduces redundant chirp waveforms. Detection on this chirp waveform can accurately locate the position of a single transmit antenna, and then the index number of other transmit antennas can be calculated through the modulation relationship of DDM. Channel separation is achieved with a low computational load, thereby improving the efficiency of channel separation.

[0115] Additionally, refer to Figure 4 This application also provides a method for resolving velocity ambiguity, which includes, but is not limited to, the following steps:

[0116] Step S410: Obtain the second reference index number of each target object in the first 2dFFT result;

[0117] Step S420: Obtain the first 2dFFT result and the second 2dFFT result corresponding to the second reference index number, and determine the fourth transmission phase and the fifth transmission phase. The fourth transmission phase is the transmission phase of the first 2dFFT result corresponding to the second reference index number, and the fifth transmission phase is the transmission phase of the second 2dFFT result corresponding to the second reference index number.

[0118] Step S430: Calculate the fuzzy Doppler phase based on the second reference index number, and calculate the reference difference between the fourth transmission phase, the fifth transmission phase, and the fuzzy Doppler phase. Determine the target velocity fuzziness factor estimate based on the reference difference.

[0119] It is understandable that by obtaining the second reference index number of each target object in the first 2dFFT result, obtaining the first 2dFFT result and the second 2dFFT result corresponding to the second reference index number, and determining the fourth and fifth transmission phases, the fourth transmission phase is the transmission phase of the first 2dFFT result corresponding to the second reference index number, and the fifth transmission phase is the transmission phase of the second 2dFFT result corresponding to the second reference index number, calculating the fuzzy Doppler phase based on the second reference index number, and calculating the reference difference between the fourth transmission phase, the fifth transmission phase, and the fuzzy Doppler phase, the target velocity fuzziness multiple estimate is determined based on the reference difference, so as to achieve velocity fuzziness resolution and obtain a larger velocity measurement range.

[0120] Additionally, in some embodiments, when the target object's distance information is 50m, velocity information is -30m / s, azimuth angle is -30°, the target object's transmitted waveform bandwidth is 64MHz, rise time is 5.12us, fall time is 4.26us, and the delay time length t between each sequence segment of the odd / even sequence is... dThe value is 0. A four-transmit, four-receive multi-antenna configuration is selected, with the receiving antenna spacing being half a wavelength and the transmitting antenna spacing being twice the wavelength. The MIMO radar has 16 channels in the horizontal direction, 256 fast-time sampling points, and 512 pulses transmitted by the redundant chirp. Both the redundant chirp and DDMchirp have 256 pulses. The Fourier transform result corresponding to an azimuth angle of -30° is as follows: Figure 12 As shown, this embodiment is performed after channel separation. In this embodiment, the unambiguous velocity range is [-51.9204 m / s, 51.9204 m / s], and the target does not exhibit velocity ambiguity. The transmission waveform of this embodiment is as follows: Figure 6 As shown, in the chirp of the nth DDM transmission, the modulation phases of the transmitting antennas Tx1-Tx4 are respectively: 0, Two-dimensional Fourier transforms were performed on the two chirps. The 2dFFT results of the redundant chirp are as follows: Figure 7 As shown, it can be seen that the simulation target set at its peak position is consistent with that of the target. Figure 8 In the 2dFFT results of the DDM waveform shown, different emissions are separated in the velocity dimension, as follows: Figure 9 As shown, CFAR detection on the redundant chirp yields a peak rangebin of i = 22 and a dopplerbin of j = 183 for Tx1. In this embodiment, since t d Choosing 0 eliminates the need for velocity deblurring. The calculation of the Doppler frequency shift causing different Tx intervals on the Doppler spectrum is as follows: Calculate the Doppler index number corresponding to the four Tx values ​​as follows:

[0121]

[0122] Thus, the index numbers corresponding to Tx1, Tx2, Tx3, and Tx4 are 183, 247, 55, and 119, respectively. In... Figure 10 The 2dFFT results shown indicate that peaks appeared at all four locations. Extracting these peaks and arranging them in channel order yields the channel phases as follows: Figure 11 As shown, the channel phase changes linearly. A Fourier transform of the rearranged data yields the following result: Figure 8 The spatial spectrum shown.

[0123] In another embodiment, the target object's distance information is 50m, its velocity information is 60m / s, and its azimuth angle is 15°; the target object's transmitted waveform bandwidth is 64MHz, its rise time is 5.12us, its fall time is 4.26us, and the delay time length t between each sequence segment of the odd and even sequences is... dFor a time interval of 1µs, a multi-antenna system with four transmitters and four receivers is selected. The spacing between the receiving antennas is half a wavelength, and the spacing between the transmitting antennas is twice the wavelength. The MIMO radar has a total of 16 channels in the horizontal direction, with 256 fast-time sampling points. The total number of pulses transmitted, including redundant chirps, is 512. The number of pulses for both redundant chirps and DDMchirps is 256. The Fourier transform result corresponding to an azimuth angle of 15° is as follows: Figure 18 As shown. In this embodiment, the unambiguous velocity range is [-49.2928m / s, 49.2928m / s], but the target velocity is ambiguous. The transmission waveform of this embodiment is as follows. Figure 6 As shown, in Figure 13 In the redundant chirp 2dFFT results, the target peak distance is correct, but velocity ambiguity appears at -38.51 m / s. (The remaining text appears to be incomplete and requires further context.) Figure 15 In the results, the target's rangebin is i = 23, and the dopplerbin is j = 157. The peak phase is denoted as... In such Figure 16 Extract the peak phase at the same position from the results The expression for calculating the blurred Doppler phase using the blur index j is:

[0124]

[0125] And calculate the difference between the three phases mentioned above.

[0126]

[0127] Calculate the fuzziness factor using the following formula.

[0128]

[0129] In this embodiment, if q = 1 is calculated, then the measured target velocity is: v = v amb +qv max = 60.0756 m / s.

[0130] Furthermore, the index numbers corresponding to the transmission lines Tx1, Tx2, Tx3, and Tx4 in this embodiment are 29, 93, 157, and 221, respectively. Figure 16 The 2dFFT results shown indicate that peaks appeared at all four locations. Extracting these peaks and arranging them in channel order yields the channel phases as follows: Figure 17 As shown, the channel phase changes linearly. A Fourier transform of the rearranged data yields the following result: Figure 14 The spatial spectrum shown.

[0131] It is important to note that t dThe introduction of this divides the 2π phase into multiple regions, namely The velocity ambiguity exhibits periodicity as q changes. Therefore, when the velocity is sufficiently high, the Doppler phase change between the two chirps exceeding 2π will still cause velocity ambiguity, and the multiple for resolving velocity ambiguity has a maximum value.

[0132]

[0133] Here The function represents the floor function, and gcd(A,B) represents finding the greatest common divisor of A and B. In this embodiment, the largest fuzzy factor that can be solved is N. q =19. Furthermore, the defuzzification range can be set arbitrarily, that is, within (q... min ,q min +N q Find a q value that meets the conditions within the range of ).

[0134] Additionally, it should be noted that t d The choice cannot make N q Too large, once N q If the value is too large, the grid points within the 2π range will be too dense, leading to decreased robustness in noisy conditions. In another embodiment, T is selected. r =10us,t d When N = 6us, q =13, which has good performance in solving fuzzy problems at a fast rate.

[0135] Additionally, refer to Figure 5 , Figure 5 This is a structural diagram of a radar signal processing system based on chirp redundant DDM waveforms provided in another embodiment of this application. An embodiment of this application also provides a radar signal processing system 500 based on chirp redundant DDM waveforms. The radar signal processing system 500 based on chirp redundant DDM waveforms includes: a memory 510, a processor 520, and a computer program stored in the memory 510 and executable on the processor 520.

[0136] The processor 520 and memory 510 can be connected via a bus or other means.

[0137] The non-transient software program and instructions required to implement the radar signal processing method based on chirp redundancy DDM waveforms in the above embodiments are stored in memory 510. When executed by processor 520, the radar signal processing method based on chirp redundancy DDM waveforms applied to the imaging system 500 based on MIMO radar target cluster detection in the above embodiments is executed. For example, the above-described radar signal processing method is executed. Figure 1 Method steps S101 to S110, Figure 2 Method steps S210 to S240 and Figure 3 Method steps S310 to S340.

[0138] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0139] Furthermore, one embodiment of this application provides a computer-readable storage medium storing computer-executable instructions that are executed by a processor or controller, for example, by a processor 520 in the above-described embodiment of the imaging system 500 for MIMO-based radar target cluster detection. The processor 520 can then execute the chirp-redundant DDM waveform-based radar signal processing method applied to the imaging system 500 for MIMO-based radar target cluster detection as described above, for example, performing the above-described... Figure 1 Method steps S101 to S110, Figure 2 Method steps S210 to S240 and Figure 3 The method steps S310 to S340 are described above. Those skilled in the art will understand that all or some of the steps and systems disclosed in the above methods can be implemented as software, firmware, hardware, or suitable combinations thereof. Some or all physical components can be implemented as software executed by a processor, such as a central processing unit, digital signal processor, or microprocessor, or as hardware, or as an integrated circuit, such as an application-specific integrated circuit. Such software can be distributed on a computer-readable medium, which can include computer storage media (or non-transitory media) and communication media (or transient media). As is known to those skilled in the art, the term computer storage media includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information (such as computer-readable instructions, data structures, program modules, or other data). Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technologies, CD-ROM, digital versatile disc (DVD) or other optical disc storage, magnetic cartridges, magnetic tape, disk storage or other magnetic storage devices, or any other medium that can be used to store desired information and is accessible to a computer. Furthermore, as is known to those skilled in the art, communication media typically contain computer-readable instructions, data structures, program modules, or other data in modulated data signals such as carrier waves or other transmission mechanisms, and may include any information delivery medium.

Claims

1. A radar signal processing method based on chirp redundant DDM waveforms, characterized in that, include: Obtain the chirp sequence and divide the chirp sequence into odd and even sequences. The delay time length between each sequence segment of the odd and even sequences is determined according to a preset speed defuzzification rule. Chirp redundant DDM waveforms are transmitted in different sequence segments respectively, the echo signals of the chirp redundant DDM waveforms are received, and the echo signals and a preset reference signal are frequency-modulated to obtain an intermediate frequency signal. Perform a fast time-dimensional Fourier transform on the sampled signal corresponding to the intermediate frequency signal to obtain the first 2dFFT result; Slow-time Fourier transforms are performed on the odd sequence segments and even sequence segments in the odd-even sequence respectively to obtain the second 2dFFT result; The first 2dFFT result is noncoherently accumulated according to the receiving channel, and CFAR detection is performed to obtain the target detection result; Based on the target detection results, the first emission phase of the second 2dFFT result corresponding to the odd sequence segment is determined, and the second emission phase of the second 2dFFT result corresponding to the even sequence segment is determined. The velocity ambiguity is then resolved based on the phase difference between the first emission phase and the second emission phase. Based on the Doppler index number corresponding to each target object in the target detection result, the third transmit phase of the corresponding receiving channel is determined in the first 2dFFT result, and the antenna position information corresponding to the first 2dFFT result is determined. Based on the third transmission phase and the antenna position information, the data corresponding to the target object in the first 2dFFT result are rearranged and subjected to angular Fourier transform to obtain the spatial spectrum of the target object; CFAR detection is performed on the 2dFFT results in the spatial dimension to obtain target attribute information; Based on the target attribute information, the index number corresponding to the target detection result is converted into target distance information, target speed information, and target angle information.

2. The radar signal processing method based on chirp redundancy DDM waveform according to claim 1, characterized in that, The target detection result includes a target unit index number, which is obtained according to the following steps: In each of the cells to be detected in the second 2dFFT result, a preset number of protection cells are skipped and a reference background region range is determined from the cells to be detected; The statistical characteristics of the background noise are calculated using the reference cells corresponding to the reference background region, and the approximate distribution of the background noise is obtained based on the statistical characteristics of the background noise. The threshold value of the current reference unit is determined based on the approximate distribution of the background noise and the preset false alarm rate. The threshold value is compared with the reference signal value corresponding to the current reference unit. The reference unit corresponding to the reference signal value that is higher than the threshold value is determined as the target unit. The index number corresponding to the target unit is determined as the target unit index number.

3. The radar signal processing method based on chirp redundancy DDM waveform according to claim 1, characterized in that, The method further includes: Obtain the first reference index number of each target object in the second 2dFFT result; The difference between each receiving channel is calculated based on the first reference index number and the phase relationship of DDM modulation; Calculate the target index number corresponding to each transmitting antenna based on the difference between the various receiving channels; Calculate the peak point corresponding to each of the target index numbers.

4. The radar signal processing method based on chirp redundancy DDM waveform according to claim 1, characterized in that, The chirp redundancy DDM waveform includes a first redundant chirp waveform and a second redundant chirp waveform. The first redundant chirp waveform is a redundant chirp waveform transmitted individually using a single transmit antenna. The second redundant chirp waveform is a chirp waveform transmitted simultaneously by all transmit antennas according to the DDM modulation rules. The expression for the second redundant chirp waveform is: ； in, For the first m The transmitted waveform of the aforementioned transmitting antenna, For launch time, This represents the number of pulses currently transmitted. For carrier frequency, This refers to the MIMO pulse repetition time. The sweep slope, For the first m The transmission start phase corresponding to each of the aforementioned transmitting antennas. The DDM phase modulated by the m-th transmitting antenna. The expression is: ； in, This represents the total number of transmitting antennas.

5. The radar signal processing method based on chirp redundancy DDM waveform according to claim 1, characterized in that, The expression for the phase difference between the first transmission phase and the second transmission phase is: in, The phase of the second 2dFFT result corresponding to the odd sequence segment at position (i,j) is the first emission phase. The phase of the second 2dFFT result corresponding to the even sequence segment at position (i,j) is the second emission phase. For the target's true speed, This is the additional delay length between the redundant chirp waveform and the DDMchirp waveform. For carrier frequency, The period of a single pulse.

6. The radar signal processing method based on chirp redundancy DDM waveform according to claim 5, characterized in that, The target's true speed The expression is: in, The blur rate obtained by detecting the index number using CFAR. For reference fuzzy factor, The maximum unambiguous velocity is determined by the MIMO pulse repetition period. The expression is: in, For carrier wavelength, At the speed of light, For carrier frequency.

7. The radar signal processing method based on chirp redundancy DDM waveform according to claim 6, characterized in that, The target attribute information includes an estimated target velocity ambiguity factor, which is obtained according to the following formula: in, This is an estimate of the fuzzy multiple of the target velocity. This is the phase difference value after winding. The following formula is used to obtain: in, The blur rate is obtained by detecting the index number using CFAR.

8. The radar signal processing method based on chirp redundancy DDM waveform according to claim 1, characterized in that, The expression for the Doppler index number is: in, For Doppler FFT points, The number of transmitting antennas, The value is an integer.

9. A radar signal processing system based on chirp redundant DDM waveforms, comprising: A memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, when the processor executes the computer program, it implements the radar signal processing method based on chirp redundant DDM waveforms as described in any one of claims 1 to 8.

10. A computer-readable storage medium storing computer-executable instructions for performing the radar signal processing method based on chirp redundant DDM waveforms as described in any one of claims 1 to 8.

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