Target localization method based on distributed fusion algorithm of step-by-step search broadband synthesis

Abstract

The present invention discloses a target positioning method based on a distributed fusion algorithm of step search broadband synthesis, comprising the following steps: constructing a distributed radar system, the system comprising a plurality of transceiver nodes, i.e., a plurality of array elements, which are distributed in an arbitrary regular pattern; the nodes respectively transmit a group of step linear frequency modulation continuous wave pulse signals and receive echo signals at the same time; the echo signals of each node are mixed with the transmission signals thereof, and low-pass filtered to obtain the mixed signals; based on the mixed signals, the estimated distances of each node to the target are obtained by FFT; the search is performed within the range of the distance resolution with a certain step length based on the estimated distances of each node as the center, and the calibration broadband synthesis is performed, and FFT is performed after the synthesis to obtain the precise positions of the targets corresponding to each node; the precise positions of the targets obtained by all nodes are weightedly fused to obtain the final target positions. The algorithm of the present invention has higher positioning accuracy, stronger anti-noise performance, and lower requirements on the signal-to-noise ratio.

Description

Technical Field

[0001] The invention belongs to the technical field of radar signal processing, in particular to a novel distributed fusion algorithm based on step-by-step search broadband synthesis. Background Art

[0002] Distributed multiple-input multiple-output (MIMO) radars are usually composed of multiple transmitting and receiving nodes that are far apart from each other. Each node has a different working frequency band, working bandwidth, transmitting waveform and antenna polarization mode. The spatial diversity gain and spatial multiplexing gain of target detection are achieved through multi-node information fusion. Due to the excellent performance and huge application value of distributed radars, many scholars have contributed to the research of distributed MIMO radars. Recent research work has mainly focused on two aspects: one is the joint beamforming technology of distributed radars. The other is the resource allocation problem of distributed radars under limited resources. However, the research on fusion algorithms still needs to be improved. Signal fusion includes two main methods: data-level fusion and signal-level fusion. Data-level fusion refers to preprocessing the echo data at the node, and only sending the processed information to the fusion center for fusion processing to obtain the final detection result. The current data-level fusion algorithm is mainly based on weighted average. Signal-level fusion means that the node does not directly process the echo signal, but sends the echo signal to the fusion center for comprehensive processing by the fusion algorithm. At present, the signal-level fusion algorithm is still mainly based on the coherent accumulation method. However, this study mainly improves the detection probability and detection distance, but does not improve the positioning accuracy. There is a great demand for signal-level fusion algorithms with higher positioning accuracy. Summary of the invention

[0003] The purpose of the present invention is to provide a target positioning method based on a distributed fusion algorithm of step search broadband synthesis to address the problems existing in the prior art, so as to realize signal level fusion of distributed radar and high-precision positioning of the target.

[0004] The technical solution to achieve the purpose of the present invention is: a target positioning method based on a distributed fusion algorithm of step search broadband synthesis, the method comprising the following steps:

[0005] Step 1, constructing a distributed radar system, the system includes multiple transceiver nodes, i.e., multiple array elements, which are distributed in an arbitrary regular pattern;

[0006] Step 2, the nodes simultaneously transmit a set of stepped linear frequency modulation continuous wave pulse signals and receive echo signals;

[0007] Step 3, mixing the echo signal of each node with its transmission signal, and performing low-pass filtering to obtain a mixed signal;

[0008] Step 4, based on the mixed signal, obtain the estimated value of the distance from each node to the target through fast Fourier transform FFT;

[0009] Step 5: Search with a certain step length within the range of distance resolution with the estimated distance value of each node as the center, and perform calibration broadband synthesis. After synthesis, perform FFT to obtain the precise position of the target corresponding to each node;

[0010] Step 6: Perform weighted fusion on the precise positions of the target obtained by all nodes to obtain the final target position.

[0011] Furthermore, step 3 specifically includes:

[0012] Step 3-1, low-pass filter the signal obtained by mixing the node echo signal and its transmission signal:

[0013]

[0014] In the formula, sl m (t) is the signal after filtering by array element m, f min is the starting frequency, ΔB is the step bandwidth, k is the frequency modulation slope, T p is the pulse width, τ m is the delay of array element m, R m is the distance of the target to the array element m, c is the speed of light;

[0015] Step 3-2, sample the filtered signal to obtain a mixed signal:

[0016]

[0017] Where N is the number of sampling points, T s is the sampling interval, satisfying: NT S =T p .

[0018] Furthermore, the step 5 is to search within the range of distance resolution with a certain step length based on the estimated distance value of each node, and perform calibration broadband synthesis, specifically including:

[0019] Step 5-1, preset a search step value sd;

[0020] Step 5-2, for each node, in the interval The distance estimate obtained in step 4 is Search for the center and step value sd to obtain c / (2B·sd)+1 possible accurate distance values;

[0021] Step 5-3, combine the possible exact distance values ​​of all nodes to obtain [c / (2B·sd)+1] M Combination of

[0022] Step 5-4, for each node, calibrate the broadband synthesis for each combination, and then perform FFT to obtain the precise position of the target corresponding to each node.

[0023] Furthermore, step 5-4 specifically includes:

[0024] Step 5-4-1, let the ath array element E a is the reference array element, 1≤a≤M, M is the number of array elements;

[0025] Step 5-4-2, processing the mixed signals of the remaining array elements except the a-th array element:

[0026] (1) The mixed signal sampled after low-pass filtering in step 4-2 is transformed into:

[0027]

[0028] in

[0029]

[0030] ψ ma [n] = 2πk(2τ m -2τ a )nT s

[0031] In the formula, τ a is the delay of array element a;

[0032] (2) Further transforming the expression in (1) above, we get:

[0033]

[0034] Step 5-4-3, performing frequency reduction correction and phase shift correction on the mixed signal processed in step 5-4-2;

[0035] Step 5-4-4, delay the signal processed in step 5-4-3 Points;

[0036] Step 5-4-5, synthesize the signals of all array elements after the above processing in the time domain:

[0037]

[0038] Step 5-4-6, perform FFT on the signal synthesized in step 5-4-5 and record the peak height;

[0039] Step 5-4-7, for each combination, repeat steps 5-4-2 to 5-4-6 to obtain the spectral peak height corresponding to each combination;

[0040] Step 5-4-8, extract the synthesized signal corresponding to the maximum spectrum peak height, perform fast Fourier transform FFT on it, obtain the estimated value of the distance from the a-th array element to the target, and further obtain the precise position of the target corresponding to the array element;

[0041] Step 5-4-9, repeat steps 5-4-1 to 5-4-8 for other array elements to obtain the precise position of the target corresponding to each array element, i.e., each node.

[0042] Compared with the prior art, the present invention has the following significant advantages:

[0043] (1) The present invention applies the idea of ​​broadband synthesis to distributed positioning, and the positioning accuracy is greatly improved compared with traditional algorithms.

[0044] (2) The distributed radar system of the present invention has no special requirements for the node arrangement and the number of antennas. Compared with other radars, it has a wider range of applications and is easier to install.

[0045] (3) The broadband synthetic distributed positioning fusion method proposed in this invention has higher noise resistance than traditional algorithms.

[0046] (4) The present invention performs frequency offset and phase error correction on the received SLFM pulse signal and uses a step search method during broadband synthesis, thereby greatly improving the positioning performance of the system.

[0047] The present invention is further described in detail below in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is a schematic diagram of the distributed radar system structure and targets.

[0049] Figure 2 It is a schematic diagram of nodes and generated targets.

[0050] Figure 3 It is a schematic diagram of simulation results.

[0051] Figure 4 This is the signal-to-noise ratio simulation result diagram. DETAILED DESCRIPTION

[0052] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0053] It should be noted that if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0054] In one embodiment, a target positioning method based on a distributed fusion algorithm of step search broadband synthesis is provided, the method comprising the following steps:

[0055] Step 1: Build a distributed radar system, which includes multiple transceiver nodes, i.e., multiple array elements, distributed in an arbitrary pattern. Figure 1 , M array elements E1, E2, …, E M Irregularly distributed, their coordinates are (x1, y1, z1), (x2, y2, z2),.., (xM, yM, zM).

[0056] Step 2, the nodes simultaneously transmit a set of stepped linear frequency modulation continuous wave pulse signals and receive echo signals;

[0057] The signal sent by the mth array element is s m (t):

[0058]

[0059] Among them, f min is the starting frequency, ΔB is the step bandwidth, k is the frequency modulation slope, T p is the pulse width;

[0060] Assume a target is located at (xt, yt, zt), and define the pitch angle and distance of the target with respect to array element m as θ m and R m The echo signal received by the array element is:

[0061]

[0062] where τ m is the delay of array element m, x is the transmitting array element index, and

[0063]

[0064] Where c is the speed of light.

[0065] Step 3, mixing the echo signal of each node with its transmission signal, and performing low-pass filtering to obtain a mixed signal; specifically comprising:

[0066] Step 3-1, low-pass filter the signal obtained by mixing the node echo signal and its transmission signal:

[0067]

[0068] In the formula, sl m (t) is the signal after filtering by array element m, f min is the starting frequency, ΔB is the step bandwidth, k is the frequency modulation slope, T p is the pulse width, τ m is the delay of array element m, R m is the distance of the target to the array element m, c is the speed of light;

[0069] Step 3-2, sample the filtered signal to obtain a mixed signal:

[0070]

[0071] Where N is the number of sampling points, T s is the sampling interval, satisfying: NT S =T p .

[0072] Step 4, based on the mixed signal, obtain the estimated value of the distance from each node to the target through fast Fourier transform FFT;

[0073] Step 5: Search with a certain step length within the range of distance resolution with the estimated distance value of each node as the center, and perform calibration broadband synthesis. After synthesis, perform FFT to obtain the precise position of the target corresponding to each node; specifically, it includes:

[0074] Step 5-1, preset a search step value sd;

[0075] Step 5-2, for each node, in the interval The distance estimate obtained in step 4 is Search for the center and step value sd to obtain c / (2B·sd)+1 possible accurate distance values;

[0076] Step 5-3, combine the possible exact distance values ​​of all nodes to obtain [c / (2B·sd)+1] M Combination of

[0077] Step 5-4, for each node, calibrate the broadband synthesis for each combination, and then perform FFT to obtain the precise position of the target corresponding to each node.

[0078] Step 6: weighted fusion is performed on the precise positions of the target obtained by all nodes to obtain the final target position. Preferably, weighted average fusion is adopted.

[0079] Further, in one embodiment, step 5-4 specifically includes:

[0080] Step 5-4-1, let the ath array element E a is the reference array element, 1≤a≤M, M is the number of array elements;

[0081] Step 5-4-2, processing the mixed signals of the remaining array elements except the a-th array element:

[0082] (1) The mixed signal sampled after low-pass filtering in step 4-2 is transformed into:

[0083]

[0084] in

[0085]

[0086] ψ ma [n] = 2πk(2τ m -2τ a )nT s

[0087] In the formula, τ a is the delay of array element a;

[0088] (2) Further transforming the expression in (1) above, we get:

[0089]

[0090] Step 5-4-3, performing frequency reduction correction and phase shift correction on the mixed signal processed in step 5-4-2;

[0091] Here, preferably, the frequency reduction correction is implemented by multiplying the mixed signal processed in step 5-4-2 by its conjugate value.

[0092] Step 5-4-4, delay the signal processed in step 5-4-3 points (system parameters should be reasonably set to integers to achieve the best performance, if not integers, they should be rounded off);

[0093] Step 5-4-5, synthesize the signals of all array elements after the above processing in the time domain:

[0094]

[0095] Step 5-4-6, perform FFT on the signal synthesized in step 5-4-5 and record the peak height;

[0096] Step 5-4-7, for each combination, repeat steps 5-4-2 to 5-4-6 to obtain the spectral peak height corresponding to each combination;

[0097] Step 5-4-8, extract the synthesized signal corresponding to the maximum spectrum peak height, perform fast Fourier transform FFT on it, obtain the estimated value of the distance from the a-th array element to the target, and further obtain the precise position of the target corresponding to the array element;

[0098] Step 5-4-9, repeat steps 5-4-1 to 5-4-8 for other array elements to obtain the precise position of the target corresponding to each array element, i.e., each node.

[0099] In one embodiment, a target positioning system based on a distributed fusion algorithm of step search broadband synthesis is provided, the system comprising:

[0100] The first module is used to realize that multiple nodes of the distributed radar system respectively transmit a set of stepped linear frequency modulation continuous wave pulse signals and receive echo signals simultaneously;

[0101] The second module is used to mix the echo signal of each node with its transmission signal and perform low-pass filtering to obtain a mixed signal;

[0102] The third module is used to obtain the estimated distance from each node to the target through fast Fourier transform FFT based on the mixed signal;

[0103] The fourth module is used to realize the search with a certain step length within the range of distance resolution with the distance estimation value of each node as the center, and perform calibration broadband synthesis, and perform FFT after synthesis to obtain the precise position of the target corresponding to each node;

[0104] The fifth module is used to perform weighted fusion on the precise positions of the targets obtained by all nodes to obtain the final target position.

[0105] For the specific definition of the target positioning system based on the distributed fusion algorithm of step search broadband synthesis, please refer to the definition of the target positioning method based on the distributed fusion algorithm of step search broadband synthesis in the above text, which will not be repeated here. Each module in the high-fidelity image reconstruction system of the above-mentioned super-resolution structured light illumination microscope can be implemented in whole or in part by software, hardware and their combination. The above-mentioned modules can be embedded in or independent of the processor in the computer device in the form of hardware, or can be stored in the memory of the computer device in the form of software, so that the processor can call and execute the operations corresponding to the above modules.

[0106] In one embodiment, a computer device is provided, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the following steps when executing the computer program:

[0107] Step 1, constructing a distributed radar system, the system includes multiple transceiver nodes, i.e., multiple array elements, which are distributed in an arbitrary regular pattern;

[0108] Step 2, the nodes simultaneously transmit a set of stepped linear frequency modulation continuous wave pulse signals and receive echo signals;

[0109] Step 3, mixing the echo signal of each node with its transmission signal, and performing low-pass filtering to obtain a mixed signal;

[0110] Step 4, based on the mixed signal, obtain the estimated value of the distance from each node to the target through fast Fourier transform FFT;

[0111] Step 5: Search with a certain step length within the range of distance resolution with the estimated distance value of each node as the center, and perform calibration broadband synthesis. After synthesis, perform FFT to obtain the precise position of the target corresponding to each node;

[0112] Step 6: Perform weighted fusion on the precise positions of the target obtained by all nodes to obtain the final target position.

[0113] For the specific limitations of each step, please refer to the limitations of the target positioning method based on the distributed fusion algorithm of step search broadband synthesis in the above text, which will not be repeated here.

[0114] In one embodiment, a computer readable storage medium is provided, on which a computer program is stored, and when the computer program is executed by a processor, the following steps are implemented:

[0115] Step 1, constructing a distributed radar system, the system includes multiple transceiver nodes, i.e., multiple array elements, which are distributed in an arbitrary regular pattern;

[0116] Step 2, the nodes simultaneously transmit a set of stepped linear frequency modulation continuous wave pulse signals and receive echo signals;

[0117] Step 3, mixing the echo signal of each node with its transmission signal, and performing low-pass filtering to obtain a mixed signal;

[0118] Step 4, based on the mixed signal, obtain the estimated value of the distance from each node to the target through fast Fourier transform FFT;

[0119] Step 5: Search with a certain step length within the range of distance resolution with the estimated distance value of each node as the center, and perform calibration broadband synthesis. After synthesis, perform FFT to obtain the precise position of the target corresponding to each node;

[0120] Step 6: Perform weighted fusion on the precise positions of the target obtained by all nodes to obtain the final target position.

[0121] For the specific limitations of each step, please refer to the limitations of the target positioning method based on the distributed fusion algorithm of step search broadband synthesis in the above text, which will not be repeated here.

[0122] As a specific example, in one of the embodiments, the present invention is simulated and verified. In the distributed radar system, the bandwidth B and the step bandwidth ΔB are set to 100 MHz. The initial frequency f min The frequency is set to 2GHz, the pulse width is set to 250us, the sampling rate is set to 10MHz, and the stepping is set to 0.05m, 0.1m, 0.3m.

[0123] The root mean square error (RMSE) is used to evaluate the performance of the system. It is defined as:

[0124]

[0125] in, is the result of the jth Monte Carlo simulation, (x t ,y t ,z t ) is the true value of the target position.

[0126] like Figure 2 As shown, suppose there are three array elements, and their coordinates are A target is generated at a random position each time, and the echo signal-to-noise ratio is set to 20 dB. Monte Carlo simulation is used, and the number of Monte Carlo simulations Nm=100.

[0127] The traditional distributed positioning algorithm without the step search synthesis algorithm and the algorithm proposed in this invention are used for simulation respectively, and the average RMSE of the results is compared. The simulation results are shown in Figure 3As shown. It can be found that the result obtained after synthesis using the roughly estimated distance parameters is even more inaccurate. This is because the roughly estimated parameters deviate greatly from the true parameters, resulting in poor continuity of the synthesized phase, and ultimately poor synthesis effect. However, after applying the step search synthesis algorithm of the present invention, the positioning accuracy of the target is greatly improved, and as the step size decreases, the effect of the algorithm is further improved, approaching the ideal situation. In other words, the ideal situation is the limit of the algorithm's performance.

[0128] Figure 4 The simulation results of the ideal synthesis algorithm and the traditional algorithm when the echo SNR is -20 to 20dB are shown. It can be seen from the results that the algorithm proposed in the present invention not only has higher positioning accuracy than the traditional algorithm, but also has stronger anti-noise performance and lower requirements on the signal-to-noise ratio.

[0129] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A target positioning method based on a distributed fusion algorithm of step search broadband synthesis, characterized in that: The method comprises the following steps: Step 1, constructing a distributed radar system, the system includes multiple transceiver nodes, i.e., multiple array elements, which are distributed in an arbitrary regular pattern; Step 2, the nodes simultaneously transmit a set of stepped linear frequency modulation continuous wave pulse signals and receive echo signals; Step 3, mixing the echo signal of each node with its transmission signal, and performing low-pass filtering to obtain a mixed signal; Step 4, based on the mixed signal, obtain the estimated value of the distance from each node to the target through fast Fourier transform FFT; Step 5: Search with a certain step length within the range of distance resolution with the estimated distance value of each node as the center, and perform calibration broadband synthesis. After synthesis, perform FFT to obtain the precise position of the target corresponding to each node; Step 6: weighted fusion of the precise positions of the target obtained by all nodes to obtain the final target position; Step 3 specifically includes: Step 3-1, low-pass filter the signal obtained by mixing the node echo signal and its transmission signal: In the formula, sl m (t) is the signal after filtering by array element m, f min is the starting frequency, ΔB is the step bandwidth, k is the frequency modulation slope, T p is the pulse width, τ m is the delay of array element m, R m is the distance of the target to the array element m, c is the speed of light; Step 3-2, sample the filtered signal to obtain a mixed signal: Where N is the number of sampling points, T s is the sampling interval, satisfying: NT S =T p ; In step 5, the search is performed within the range of the distance resolution with a certain step length based on the estimated distance value of each node, and the calibration broadband synthesis is performed, which specifically includes: Step 5-1, preset a search step value sd; Step 5-2, for each node, in the interval The distance estimate obtained in step 4 is Search for the center and step value sd to obtain c / (2B·sd)+1 possible accurate distance values; Step 5-3, combine the possible exact distance values ​​of all nodes to obtain [c / (2B·sd)+1] M Combination of Step 5-4, for each node, calibrate the broadband synthesis for each combination, and then perform FFT to obtain the precise position of the target corresponding to each node; Step 5-4 specifically includes: Step 5-4-1, let the ath array element E a is the reference array element, 1≤a≤M, M is the number of array elements; Step 5-4-2, processing the mixed signals of the remaining array elements except the a-th array element: (1) The mixed signal sampled after low-pass filtering in step 4-2 is transformed into: in ψ ma [n]=2πk(2τ m -2t a )nT s In the formula, τ a is the delay of array element a; (2) Further transforming the expression in (1) above, we get: Step 5-4-3, performing frequency reduction correction and phase shift correction on the mixed signal processed in step 5-4-2; Step 5-4-4, delay the signal processed in step 5-4-3 Points; Step 5-4-5, synthesize the signals of all array elements after the above processing in the time domain: Step 5-4-6, perform FFT on the signal synthesized in step 5-4-5 and record the peak height; Step 5-4-7, for each combination, repeat steps 5-4-2 to 5-4-6 to obtain the spectral peak height corresponding to each combination; Step 5-4-8, extract the synthesized signal corresponding to the maximum spectrum peak height, perform fast Fourier transform FFT on it, obtain the estimated value of the distance from the ath array element to the target, and further obtain the precise position of the target corresponding to the array element; Step 5-4-9, repeat steps 5-4-1 to 5-4-8 for other array elements to obtain the precise position of the target corresponding to each array element, i.e., each node.

2. The target positioning method based on the distributed fusion algorithm of step search broadband synthesis according to claim 1 is characterized in that: The down-conversion correction in step 5-4-4 is implemented by multiplying the mixed signal processed in step 5-4-2 by its conjugate value.

3. A target positioning system based on a distributed fusion algorithm of step search broadband synthesis according to the method of any one of claims 1 to 2, characterized in that: The system comprises: The first module is used to realize that multiple nodes of the distributed radar system respectively transmit a set of stepped linear frequency modulation continuous wave pulse signals and receive echo signals simultaneously; The second module is used to mix the echo signal of each node with its transmission signal and perform low-pass filtering to obtain a mixed signal; The third module is used to obtain the estimated distance from each node to the target through fast Fourier transform FFT based on the mixed signal; The fourth module is used to realize the search with a certain step length within the range of distance resolution with the distance estimation value of each node as the center, and perform calibration broadband synthesis, and perform FFT after synthesis to obtain the precise position of the target corresponding to each node; The fifth module is used to perform weighted fusion on the precise positions of the targets obtained by all nodes to obtain the final target position.

4. A computer device 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, the steps of the method according to any one of claims 1 to 2 are implemented.

5. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 2 are implemented.

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