A multi-target positioning detection method and device of a MIMO radar

Abstract

The application relates to the technical field of radar positioning, in particular to a multi-target positioning and detection method and device of a MIMO radar, which comprises the following steps: after a MIMO radar transmits a pulse signal to multiple targets, receiving echo signals of each receiving end; performing multi-path separation on each echo signal, analyzing the influence degree of multi-path effect to determine the optimal weight when each path is combined, obtaining a combined signal of the same receiving end; and positioning and detecting the multiple targets based on the combined signals of all receiving ends. The application aims to improve the accuracy of the MIMO radar when positioning multiple targets.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of radar positioning, in particular to a multi-target positioning and detection method and device of MIMO radar. BACKGROUND

[0002] MIMO (Multiple-Input Multiple-Output) radar, namely multi-input multi-output radar, is a radar equipped with multiple transmitting antennas and multiple receiving antennas. In operation, multiple transmitting antennas simultaneously transmit mutually orthogonal waveform signals, which propagate in space and are reflected after encountering a target. The reflected echo is received by multiple receiving antennas, and the receiving end can distinguish the echo corresponding to different transmitting antennas according to a unique coding manner, thereby obtaining more information about the target. It is a key sensing device for realizing all-weather, all-time accurate identification of environmental threats and abnormal behaviors, effectively improving the safety protection efficiency in complex scenarios, and ensuring the safety of key facilities and personnel.

[0003] When using MIMO radar for multi-target positioning, multiple transmitting antennas and receiving antennas exist, and in the process of radar signal transmission and reception, the phenomenon of simultaneous existence of multipath effect and noise interference will occur, which will cause the received radar signal to be a signal received by each receiving antenna after the mixed signal of interference signal and echo signal after the multipath effect. MIMO radar usually uses spatial diversity technology to reduce the interference caused by multipath effect. In order to maximize the diversity gain, it is necessary to ensure that the correlation between the signal copies received by each receiving path remains at a low level. If the correlation between the signal copies is too high, the diversity effect will be seriously affected, and even the performance improvement will be limited or the opposite effect will be obtained. However, the current spatial diversity technology ignores the fact that the noise interference received by different receiving antennas is inconsistent. When combining signal copies to suppress multipath effect, the real echo signal will be overwhelmed by noise, resulting in errors in the positioning results of multi-targets. SUMMARY

[0004] In order to solve the above technical problems, the present application provides a multi-target positioning and detection method and device of MIMO radar, and the technical solution adopted is as follows:

[0005] In the first aspect, one embodiment of the present application provides a multi-target positioning and detection method of MIMO radar, which comprises the following steps:

[0006] Step one: transmitting pulse signals to multiple targets by using MIMO radar and receiving echo signals of each receiving end;

[0007] Step two: multi-path separation is performed on each echo signal, and the influence degree of multi-path effect is analyzed to determine the optimal weight when each path is combined, and a combined signal of the same receiving end is obtained;

[0008] 2.1, generating the suppression coefficient of the complex gain of each path based on the phase angle correlation between paths;

[0009] 2.2, calculating the distance loss of signal transmission when each target is positioned, and combining the proportion of path propagation distance in the minimum path propagation distance to apply distance compensation to each path;

[0010] 2.3, based on the DOA difference of the interference signal in the echo signal received at adjacent time of the same receiving end, determining the interference degree of each pulse signal transmitted by the MIMO radar;

[0011] 2.4, combining the suppression coefficient of the complex gain of each path, the distance compensation, and the interference degree of all transmitted pulse signals, to generate the optimal weight when each path in the same echo signal is combined for signal combination;

[0012] Step three: positioning and detecting multiple targets based on the combined signals of all receiving ends.

[0013] Preferably, the calculation method of the suppression coefficient of the complex gain of each path is:

[0014] Calculate the correlation coefficient between each path and any path;

[0015] The mean value of the absolute value of the correlation coefficient between each path and all other paths is taken as the suppression coefficient of the complex gain of each path.

[0016] Preferably, the correlation coefficient is determined by the cosine value of the phase angle difference between two paths.

[0017] Preferably, the expression for applying distance compensation to each path is:

[0018]

[0019] In the formula, denotes the distance compensation of the jth path, denotes the exponential function with the natural constant as the base, , denote the propagation distance of the jth path and the minimum value in the propagation distance of all paths, respectively, is the mean value of the distance loss of signal transmission when all targets are positioned.

[0020] Preferably, the distance loss is determined according to the deviation of the target distance from the MIMO radar relative to the effective detection distance of the MIMO radar.

[0021] Preferably, the method for determining the interference degree of each pulse signal is:

[0022]

[0023] wherein, is the interference degree of the pth pulse signal, N is the number of receiving antennas, Q is the number of echo signals received by the receiving antennas, , and are the DOAs of the interference signals in the qth and q-1th echo signals received by the nth receiving antenna, respectively.

[0024] Preferably, the generating expression of the maximum weight when the paths are combined is:

[0025]

[0026] wherein, is the maximum weight when the jth path is combined, is the complex gain of the jth path is the complex conjugate of the complex gain of the jth path, is the suppression coefficient of the complex gain of the jth path, is the distance compensation of the jth path, and P is the number of pulse signals transmitted by the MIMO radar, is the interference degree of the pth pulse signal.

[0027] Preferably, the signal combination using the maximum weight comprises:

[0028] multiplying the signal of the jth path by to obtain the received signal after the phase difference of the jth path is eliminated, wherein, is the phase angle of the complex gain of the jth path, and e is the natural constant;

[0029] linearly weighting and combining the received signals processed by the MRC technology on all paths in the same echo signal to obtain the positioning signal of the same echo signal.

[0030] Preferably, the positioning and detection of multiple targets based on the combined signals of all receiving ends comprises:

[0031] performing echo signal separation on the combined signal of each receiving end, and extracting the distance, speed and angle information of all targets through the constant false alarm rate detection, non-coherent accumulation and Doppler FFT steps.

[0032] In a second aspect, another embodiment of the present application provides a multi-target positioning and detection device of a MIMO radar, comprising:

[0033] M transmit antennas for transmitting waveforms, and N receive antennas for receiving signals;

[0034] The M transmit antennas are uniformly spaced in space by a distance d1, and the N receive antennas are uniformly spaced in space by a distance d2, and the uniform spacing d2 is greater than half a signal wavelength;

[0035] A signal receiving module configured to receive echo signals from each receive end after transmitting pulse signals to multiple targets by the MIMO radar;

[0036] A signal processing module configured to analyze the influence of multipath effects on the echo signals received by each receive antenna to obtain a combined signal of the same receive end;

[0037] A positioning and detection module configured to perform positioning and detection on the multiple targets based on the combined signals of all receive ends.

[0038] The present application has at least the following beneficial effects:

[0039] In the present application, when considering multiple target positioning, the path weight is adaptively adjusted by considering multipath separation, multipath effect suppression, and distance compensation, and the distance between different paths, different targets, and the DOA of the interference source around the multiple targets to the path weight in traditional combination, thereby avoiding the problem that the far distance target signal is drowned by noise and the echo signal of the near distance target is affected by multipath effect interference, and the signal amplitude and noise power of the signal on the path are only considered. By optimizing the path weight in the MRC combination technology, the post-combination signal energy is the sum of the path energies, the noise is non-coherent superposition, the SNR is significantly improved, and the accuracy of the MIMO radar in multiple target positioning is improved. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 A step flowchart of a multiple target positioning and detection method of a MIMO radar according to an embodiment of the present application. DETAILED DESCRIPTION

[0041] Embodiment 1

[0042] In the present application, the multiple target positioning and detection device of the MIMO radar includes M transmit antennas for transmitting waveforms, and N receive antennas for receiving signals, the M transmit antennas are uniformly spaced in space by a distance d1, and the N receive antennas are also uniformly spaced in space by a distance d2, and the uniform spacing d2 is at least greater than half a signal wavelength, i.e. , a signal wavelength, so as to ensure sufficient spatial correlation difference between the received signals and prevent resolution ambiguity between the received signals, and the present application does not make special limitations thereon, and the number of positioning and detection targets is K.

[0043] In addition, the device further comprises a signal receiving module, a signal processing module and a positioning detection module.

[0044] The signal receiving module is configured to receive echo signals of each receiving end after transmitting pulse signals to multiple targets by the MIMO radar.

[0045] The signal processing module is configured to analyze the influence degree of multipath effect on the echo signals received by each receiving antenna to obtain a combined signal of the same receiving end.

[0046] The positioning detection module is configured to perform positioning detection on the multiple targets based on the combined signals of all receiving ends.

[0047] Embodiment 2

[0048] The present application provides a multi-target positioning detection method of MIMO radar, and a step flow chart of the method is shown in FIG. 1. Figure 1 The signal receiving module, the signal processing module and the positioning detection module in the multi-target positioning detection device of the MIMO radar are implemented as follows.

[0049] Step 1: receiving echo signals of each receiving end after transmitting pulse signals to multiple targets by the MIMO radar.

[0050] In the MIMO radar, multiple transmitters simultaneously send independent signals, which propagate in space and interact with targets, and are captured by a receiver array. By analyzing the phase and amplitude information of these signals, accurate positioning and imaging of targets can be achieved.

[0051] Specifically, when positioning K targets, P orthogonal pulse signals S are simultaneously transmitted by M transmitting antennas, and after reaching the K targets, the echo signals reflected by the targets are received by N receiving antennas, and the propagation path of each echo signal is obtained.

[0052] Step 2: performing multi-path separation on each echo signal, analyzing the influence degree of multipath effect to determine the optimal weight of each path when combined, and obtaining a combined signal of the same receiving end.

[0053] In the process of multi-target positioning detection in MIMO radar, due to the orthogonality of channel vectors, the low complexity of maximum combination ratio MRC makes MRC become the optimal algorithm in linear combination technology, which can maximize the signal-to-noise ratio of the output signal under a given number. MRC adjusts the signals of all branches in phase, and also needs to weight each branch. However, when MIMO radar is used for multi-target positioning, due to the existence of multipath effect, the influence degree of multipath effect on the signal of each branch is different. When positioning multiple targets, the distance of multiple targets from the radar is not fixed. However, the traditional weighting coefficient usually considers the signal amplitude and noise power of the signal on the path, which may cause the signal of the far distance target to be submerged by noise, and the echo signal of the near distance target is more affected by the multipath effect interference.

[0054] 2.1, generating a suppression coefficient of the complex gain of each path based on the phase angle correlation between paths.

[0055] Since the signal experiences different attenuation and phase shift on each path during multipath propagation, the path complex gain is a parameter used to describe this change. The path complex gain is a complex number, and its modulus represents the attenuation degree of the signal on the path, and the phase represents the phase shift of the signal. The greater the modulus of the estimated complex gain of each path, the lower the attenuation degree of the signal on the path, and the greater the weight in subsequent fusion; the smaller the modulus of the complex gain, the greater the influence of interference and attenuation on the received signal on the path, and the smaller the weight in subsequent fusion.

[0056] Firstly, the echo signal under each pulse received by the same receiving end is separated by a multipath separation technology to obtain L separated paths, and signal estimation is performed to obtain the path delay and complex gain of each path, the complex gain including amplitude and phase angle. The multipath separation technology is a well-known technology in the field of signal processing, and the specific process will not be described here.

[0057] Secondly, the distances of K positioning targets from the antenna are different. Compared with the far distance target, the time delay expansion of the near distance target with a smaller distance from the radar under the multipath effect is more significant, resulting in a higher distortion degree of the signal phase than the echo signal phase reflected by the far distance target. This is because the relative time difference between the direct signal and the reflected signal increases due to the short distance, resulting in more significant time delay expansion effect. The more significant the time delay expansion effect on the path, the greater the difference between the signals on the path even if the path is disturbed by the same noise source, and the lower the correlation between the paths. Therefore, the application considers using the correlation degree between the paths to determine the suppression degree of the complex gain of the path.

[0058] For any one path of each echo signal, taking the first path as an example, the first path is used as an example, and the first path is used as an example. ​The higher the correlation between the first path and the other paths, the more likely the first path is to be related to the others. The less interference the signal experiences on a given path, the lower the noise component in the echo signal on that path. Therefore, the noise level should be reduced on the first path. The degree of suppression when merging the first path; conversely, the degree of suppression when merging the second path. The lower the correlation between the distance of the first path and the other paths, the lower the correlation between the distance of the second path and the distance of the third path. The more noise components in the signal along a path, the lower the value should be. The complex gain on the nth path is suppressed to a greater extent. The nth path's complex gain is then... The suppression coefficient of the complex gain of each path is expressed as: :

[0059]

[0060]

[0061] In the formula, Indicates the first The path and the first The correlation coefficient between the paths It is the phase angle difference between the two paths. It is a cosine function; Indicates the first The mean of the absolute values ​​of the correlation coefficients between the L-1 paths and the remaining L-1 paths.

[0062] 2.2 Calculate the signal transmission distance loss when locating each target, and apply distance compensation to each path based on the ratio of the path propagation distance to the minimum path propagation distance.

[0063] On the other hand, since the signal propagation distance varies along each path, the echo signal from the same target traveling along a shorter path will not only have a shorter time delay to reach the receiving antenna compared to a longer path, but the signal attenuation will also be more severe over longer distances, leading to a lower signal-to-noise ratio. External interference (such as electromagnetic interference and thermal noise) will have a more significant impact on the signal, making the echo signal from targets farther from the receiving antenna more susceptible to being overwhelmed by noise. Therefore, this application considers determining path distance compensation based on the distance between the target and the antenna, as well as the transmission distance along each path.

[0064] Based on the above analysis, distance compensation is calculated for each path during target localization. This distance compensation reduces signal attenuation caused by the transmission of echo signals from distant targets. The distance compensation for the j-th path is expressed as... :

[0065]

[0066]

[0067] In the formula, represents the distance loss of the kth target positioning signal transmission, represents the distance of the kth target MIMO radar, is equal to the average of the straight-line distance between the kth target and the M transmitting antennas and the N receiving antennas, is the effective detection distance of the MIMO radar, is a preset path loss exponent, with a value range of 1.6-6.5, and here taking propagation in free space as an example, the size of is set to 2;

[0068] represents an exponential function with a natural constant as the base, , respectively represent the propagation distance of the jth path and the minimum value in the propagation distances of all paths, is the average of the distance losses of all target positioning signal transmissions. Wherein, all paths are all paths obtained after multi-path decomposition of the same echo signal.

[0069] It should be noted that, controls the speed at which the compensation result decreases as the path distance deviates from the shortest distance. The smaller the value of is, the closer the overall distribution of the K targets positioned is to the distance between the receiving antennas and the transmitting antennas, and the weight of the path with a short transmission distance in subsequent fusion should be increased, and the suppression of long paths is stronger. The greater the value of is, the farther the overall distribution of the K targets positioned is from the distance between the receiving antennas and the transmitting antennas, and the distance compensation of long distance paths needs to be increased.

[0070] 2.3, based on the DOA difference of the interference signals in the echo signals received at adjacent times by the same receiving end, determine the interference degree of each pulse signal transmitted by the MIMO radar.

[0071] First, the DOA of the interference signal in the echo signal received by each receiving antenna is obtained by using the trained interference DOA estimation model, and the estimation model is a deep belief network (DBN) model, including the following two steps:

[0072] 1. Obtain the spatial spectrum of the echo signal received by each receiving antenna using the MUSIC algorithm, and extract the spectral peak in the spatial spectrum;

[0073] 2. Obtain the DOA of the interference signal by using the trained DBN model.

[0074] Further, the severity of the interference on each receiving antenna when receiving the echo signal of the multi-target is evaluated based on the DOA of the interference signal in all the pulse signals received by each receiving antenna. When the target generates the echo signal, the reflection coefficient of the target is constant, so the greater the difference between the overlapping angle interval between the DOA corresponding to different interference signals of each receiving antenna and the DOA of the target, the closer the interference source is to the target, and the stronger the randomness of the interference on different pulse signals, the greater the influence on the accuracy of the positioning result, and the smaller the weight should have when merging subsequently; while the more similar the overlapping angle interval between the DOA of different interference signals and the DOA of the target, the farther the interference source is from the target, and the smaller the interference on the echo signal reflected by the target.

[0075] Here, the interference degree of each pulse signal is determined by the receiving antenna receiving the signal, and the interference degree of the pth pulse signal is represented as

[0076]

[0077] In the formula, N is the number of receiving antennas, Q is the number of echo signals received by the receiving antenna, , and is the DOA of the interference signal in the qth and q-1th echo signals received by the nth receiving antenna.

[0078] 2.4, the suppression coefficient of the complex gain of each path, the distance compensation, and the interference degree of all the transmitted pulse signals are integrated to generate the maximum weight when merging each path in the same echo signal, so as to perform signal merging.

[0079] First, the suppression coefficient of the complex gain of the above path, the distance compensation, and the interference degree of all the transmitted pulse signals are integrated to generate the maximum weight when merging multiple paths in the same echo signal, and the maximum weight when merging the jth path is represented as

[0080]

[0081] In the formula, is the maximum weight when merging the jth path, is the complex conjugate of the complex gain of the jth path, is the suppression coefficient of the complex gain of the jth path, is the distance compensation of the jth path, and P is the number of pulse signals transmitted by the MIMO radar, is the interference degree of the pth pulse signal.

[0082] After that, the signal of the jth path is multiplied by​​​​ , to obtain the received signal after the phase difference of the jth path is eliminated, wherein, is the phase angle of the complex gain of the jth path, and e is a natural constant.

[0083] The received signals processed by the MRC technology for all paths in the same echo signal are linearly weighted and combined to obtain a positioning signal of the same echo signal, so that the energy of the combined signal is the sum of the energies of the paths, the noise is non-coherent superposition, and the SNR is significantly improved. The MRC technology is a known technology, and the specific process will not be described again.

[0084] Step three: based on the combined signals of all receiving ends, a multi-target is positioned and detected.

[0085] First, the combined signal of each receiving end is subjected to echo signal separation, and the separated signal is subjected to CFAR (constant false alarm rate detection), non-coherent accumulation, Doppler FFT and other steps to extract the distance, speed and angle information of K targets.

[0086] Using radar echo signals to obtain target positioning results is a prior art, including but not limited to sparse decomposition positioning method, least square method, and the specific process will not be described again.

[0087] Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. It is intended that the application cover any variations, uses or adaptive changes of the application following the general principles thereof and including such departures from the present disclosure as come within known use or custom in the art to which the application pertains.

[0088] It should be understood that the application is not limited to the precise construction that has been described above and illustrated in the accompanying drawings, and that various modifications and changes can be made by those skilled in the art without departing from the scope thereof.

Claims

1. A multi-target localization and detection method for MIMO radar, characterized in that, The method includes: Step 1: After transmitting pulse signals to multiple targets using MIMO radar, receive the echo signals from each receiver. Step 2: Perform multipath separation on each echo signal, analyze the degree of multipath effect to determine the final weight when merging each path, and obtain the merged signal at the same receiver. 2.1, Based on the phase angle correlation between paths, the suppression coefficient of the complex gain of each path is generated; 2.2 Calculate the signal transmission distance loss during the positioning of each target, and apply distance compensation to each path based on the ratio of the path propagation distance to the minimum path propagation distance; 2.

3. Based on the difference in DOA of the interference signal in the echo signals received at adjacent times by the same receiver, determine the degree of interference of each pulse signal transmitted by the MIMO radar; 2.

4. By combining the suppression coefficient of the complex gain of each path, the distance compensation, and the interference level of all transmitted pulse signals, the final weight for merging the paths in the same echo signal is generated for signal merging. Step 3: Locate and detect multiple targets based on the merged signals from all receivers.

2. The multi-target localization and detection method for MIMO radar according to claim 1, characterized in that the method for calculating the suppression coefficient of the complex gain of each path is as follows: Calculate the correlation coefficient between each path and any other path; The mean of the absolute values ​​of the correlation coefficients between each path and all other paths is used as the suppression coefficient of the complex gain of each path.

3. The multi-target localization and detection method of MIMO radar according to claim 2, characterized in that, The correlation coefficient is determined by the cosine of the phase angle difference between the two paths.

4. A multi-target localization and detection method for MIMO radar according to claim 1 or 2, characterized in that, The expression for applying distance compensation to each path is: ； In the formula, This represents the distance compensation for the j-th path. This represents an exponential function with the natural constant as its base. , Let represent the propagation distance of the j-th path and the minimum propagation distance among all paths, respectively. It is the average distance loss of signal transmission when all targets are located.

5. The multi-target localization and detection method of MIMO radar according to claim 4, characterized in that, The range loss is determined based on the degree of deviation of the target's distance from the MIMO radar relative to the effective detection range of the MIMO radar.

6. The multi-target localization and detection method of MIMO radar according to claim 1, characterized in that, The method for determining the degree of interference of each pulse signal is as follows: ； In the formula, represents the interference level of the p-th pulse signal, N is the number of receiving antennas, and Q is the number of echo signals received by the receiving antennas. , These are the DOAs of the interference signals in the q-th and (q-1)-th echo signals received by the n-th receiving antenna, respectively.

7. The multi-target localization and detection method of MIMO radar according to claim 1, characterized in that, The expression for generating the final weight when merging the various paths is: ； In the formula, It is the final weight when merging the j-th path. It is the complex gain of the j-th path. The complex conjugate, It is the suppression coefficient of the complex gain of the j-th path. This represents the distance compensation for the j-th path, and P is the number of pulse signals transmitted by the MIMO radar. It represents the degree of interference of the p-th pulse signal.

8. The multi-target localization and detection method of MIMO radar according to claim 7, characterized in that, Signal merging using the final weights includes: Multiply the signal of the j-th path by The received signal after phase difference elimination for the j-th path is obtained, where, is the phase angle of the complex gain of the j-th path, and e is the natural constant; The MRC technique is used to linearly weight and combine the received signals after processing all paths in the same echo signal to obtain the positioning signal of the same echo signal.

9. A multi-target localization and detection method for MIMO radar according to claim 1, characterized in that, The method of locating and detecting multiple targets based on the merged signals from all receivers includes: The combined signal from each receiver is separated into echo signals. The separated signals are then processed through constant false alarm rate detection, noncoherent accumulation, and Doppler FFT steps to extract the range, velocity, and angle information of all targets.

10. A multi-target localization and detection device for MIMO radar, characterized in that, include: M transmitting antennas for transmitting waveforms, and N receiving antennas for receiving signals; The M transmitting antennas are spaced uniformly with a spacing d1, and the N receiving antennas are spaced uniformly with a spacing d2, where the uniform spacing d2 is greater than half the signal wavelength. The signal receiving module is used to receive the echo signal from each receiver after transmitting pulse signals to multiple targets using MIMO radar, thereby realizing step one of the multi-target positioning and detection method of MIMO radar as described in claim 1. The signal processing module is used to analyze the degree of multipath effect on the echo signal received by each receiving antenna in order to obtain the combined signal at the same receiving end, thereby realizing step two in the multi-target positioning and detection method of MIMO radar as described in claim 1. The positioning and detection module is used to locate and detect multiple targets based on the merged signals from all receivers, thereby implementing step three of the multi-target positioning and detection method for MIMO radar as described in claim 1.

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