Distributed multi-radar space-time-frequency domain cooperative multi-main-lobe intermittent sampling interference resisting method

Abstract

The invention discloses a distributed multi-radar space-time-frequency domain cooperative multi-main-lobe intermittent sampling interference resisting method, which comprises the following steps of: firstly, setting radar signal parameters, transmitting and processing radar signals to obtain an R-D plane graph, and then performing interference identification and elimination by utilizing an echo processing result of each sub-pulse signal based on the R-D plane graph. And finally, performing plot condensation on the processed R-D planar graph by adopting DBSCAN to obtain distance and speed information of the target, and realizing detection of the target. According to the method provided by the invention, interference elimination can be carried out through multi-radar emission of multiple sub-pulses to avoid interference sampling and cooperative signal processing of a receiving end under the condition of no interference prior information, target detection can be realized in various interference environments, and the method has good main lobe intermittent sampling interference resistance.

Description

Technical Field

[0001] The present invention belongs to the technical field of signal processing, and in particular relates to a distributed multi-radar space-time-frequency domain collaborative anti-multi-main-lobe intermittent sampling interference method. Background Art

[0002] In recent years, with the continuous development of information technology, the living environment of radar has become more and more complex. How to ensure that radar can work normally in a complex electronic environment has become particularly important. Faced with the current high-intensity, multi-style complex electromagnetic interference environment, in order to achieve this goal, modern radars have adopted various anti-interference methods, such as sidelobe blanking, sidelobe cancellation, low sidelobe, etc. However, when interference enters the radar antenna from the main lobe, the sidelobe anti-interference method is almost ineffective. The use of these methods often leads to problems such as mainlobe beam distortion and mainlobe direction deviation. Therefore, solving the mainlobe interference problem of radar has significant research value.

[0003] Due to the characteristics of intermittent sampling and forwarding interference, the interference sampling process only exists in a part of the time domain. Consider using multiple sites to intermittently transmit sub-pulse signals with different pulse widths to piece together a cooperative signal in the form of a continuous wave in the time domain. Under this cooperative strategy, the jammer's sampling cannot guarantee that every sub-pulse signal is sampled, and the sampling length of the sampled sub-pulse signal is also uncertain.

[0004] The reference "W.Xiong, G.Zhang and W.Liu.'Efficient filter design againstinterrupted sampling repeater jamming for wideband radar'EURASIP Journal onAdvances in Signal Processing, 2017(1):1-12, 2017" designed a filter based on the difference in time-frequency characteristics between the target echo and ISRJ, effectively filtering out the interference signal while maintaining the integrity of the target echo. The reference "B.Fan, X.Du and W.Hu.'False targets suppression of integral power frequency modulated waveform for countering interrupted sampling repeater jamming'.IEEEGeoscience and Remote Sensing Letters, 20:1-5, 2023" derived the fuzzy function of the integral power frequency modulated waveform, analyzed the time-frequency characteristics of ISRJ in the range Doppler plane, and proposed an improved Doppler filter processing method to suppress the interference of false targets. The above signal processing anti-interference technology focuses on suppressing interference at the radar receiving end, which is a passive anti-interference technology and does not effectively utilize the freedom of the radar system transmitting end. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a distributed multi-radar space-time-frequency domain collaborative anti-multi-mainlobe intermittent sampling interference method, which can use the echo processing results of each sub-pulse signal to perform data fusion, identify and eliminate interference, and ultimately achieve target detection.

[0006] The technical solution adopted by the present invention is: a distributed multi-radar space-time-frequency domain collaborative anti-multi-mainlobe intermittent sampling interference method, the specific steps are as follows:

[0007] S1. Set radar signal parameters and transmit radar signal;

[0008] S2, processing the signal obtained in step S1 to obtain an RD plane graph;

[0009] S3, performing interference identification and elimination based on the RD plane diagram obtained in step S2;

[0010] After the inter-pulse accumulation in step S2, interference identification and elimination are performed on the accumulation results. A threshold value ψ is set. The area in the RD result that exceeds the threshold value ψ is assigned a value of 1, and the area that does not exceed the threshold value ψ is assigned a value of 0. Then, data fusion is performed on the RD results of all sub-pulses: a logical "AND" operation is performed on all areas of each RD result to obtain the area where the real target exists.

[0011] S4, using DBSCAN to perform point condensation on the RD plane map after processing in step S3 to obtain the distance and speed information of the target;

[0012] The DBSCAN algorithm includes two important parameters: neighborhood radius and minimum point count threshold. The two parameters are used to explain the definition of dense in dense areas: when the number of points within the neighborhood radius of a point is greater than the minimum point count threshold, it is considered to be dense.

[0013] When the DBSCAN algorithm scans the samples, it divides the sample points into three categories: core points, boundary points, and noise points:

[0014] 1) The core point is the sample point whose number of sample points within the neighborhood radius is greater than the minimum point count threshold;

[0015] 2) Boundary points are sample points that are non-core points in the neighborhood of a core point;

[0016] 3) Sample points that are not core points or boundary points are noise points.

[0017] Furthermore, the step S1 is specifically as follows:

[0018] Assuming that there are M sub-pulses in one pulse, and the sub-pulse signals transmitted by each station are linear frequency modulation signals with orthogonal frequencies, the expression of the multi-sub-pulse structure signal x(t) is as follows:

[0019]

[0020] Where t represents the pulse emission time, x m (t) represents the mth sub-pulse signal, represents the emission time of the mth sub-pulse, T m represents the duration of the mth sub-pulse. m (t) The specific expression is as follows:

[0021]

[0022] Among them, f m represents the carrier frequency of the mth sub-pulse, It represents the baseband signal form of the mth sub-pulse. The specific expression is as follows:

[0023]

[0024] Among them, μ m =B / T m represents the linear frequency modulation slope of the mth sub-pulse, and B represents the bandwidth of each sub-pulse.

[0025] In a PRT, the transmission signals of multiple transmission sites are spliced ​​into a long pulse; in a CPI, the pulse width, timing and bandwidth of the transmission signals of each site are kept unchanged, and the expression of a single pulse x(t) is as follows:

[0026]

[0027] Assuming that there are N pulses in 1 CPI, the expression of the transmitted signal s(t) in one CPI is as follows:

[0028]

[0029] Among them, t n =(n-1)T, where T represents the duration of a single pulse.

[0030] Furthermore, the step S2 is specifically as follows:

[0031] S21, obtaining an echo signal;

[0032] The transmitted signal s(t) is a narrowband signal. The target distance remains unchanged during the target detection process. Considering the case of a single point target, the expression of the echo signal y(t) is as follows:

[0033]

[0034] Among them, c represents the speed of light, R represents the target distance, v represents the radial velocity and is much smaller than the speed of light, and the time delay is approximately τ = 2R / c.

[0035] Since the carrier frequencies of each sub-pulse are different, the wavelength and Doppler shift are also different. The wavelength λ corresponding to each sub-pulse is m and Doppler shift The expressions are as follows:

[0036]

[0037] S22, multi-channel pulse compression, that is, using each sub-pulse transmission signal as a different mismatch filter to perform mismatch separation with the echo;

[0038] There are M sub-pulses in a pulse. M mismatch filters h are designed according to the M sub-pulses. m ,m=1,2,...,M, use different mismatch filters and echoes to perform mismatch separation.

[0039] The echo signal obtained in step S21 is y(t), which is converted into a fast and slow time dimension discrete matrix Y after sampling. Y(n,h) represents the hth sampling point of the nth pulse signal. Then the nth pulse signal of the echo passes through the output Z of the mth filter. m The expression of (n,τ) is as follows:

[0040]

[0041] S23, time domain shifting, that is, aligning the envelope of each mismatch separation result by time domain shifting for subsequent accumulation;

[0042] According to the emission time of different sub-pulses, the Z m (n,τ) is cyclically shifted K m units, and truncate the signal at time 0 to obtain the result Z′ of mismatch separation after time domain shifting m (n,τ).

[0043] in, k i Represents the length of each sub-pulse after discretization.

[0044] S24, accumulating the same sub-pulses between different pulses, i.e., accumulating each sub-result using non-uniform discrete Fourier transform (NUDFT) to obtain a sub-RD graph;

[0045] For the mth sub-pulse, set the maximum unambiguous velocity to v max , uniformly sample Q points in the unambiguous speed range and obtain the sequence v Q =[v1,v2,…,v Q ], define the row vector h m,q , the expression is as follows:

[0046]

[0047] Among them, v q =-v max +(q-1)(2v max / Q), q=1,2,…,Q.

[0048] Then construct the NUDFT transformation matrix The specific expression is as follows:

[0049]

[0050] in,() T represents the transpose of a matrix, Then the mismatch separation result Z′ of the mth sub-pulse after time domain shifting is mThe NUDFT processing expression of (n,τ) is as follows:

[0051] β m (v,τ)=H m Z′ m

[0052] Among them, β m (v,τ) is the RD diagram of the mth sub-pulse.

[0053] Furthermore, the step S4 is specifically as follows:

[0054] S41, identifying core points;

[0055] For each sample point of the RD plane graph after processing in step S3, if the number of samples within its neighborhood radius (including itself) reaches or exceeds the preset minimum number of points, then this sample point is identified as a core point; then, this core point and all points within the neighborhood radius are combined into a preliminary temporary cluster;

[0056] S42, expansion of temporary clusters;

[0057] For the temporary cluster formed in step S41, all sample points are checked. If some points are found to be core points, all points in the neighborhood radius of these points are also added to the current temporary cluster. Repeat the expansion until no new core points can be added. At this time, the preliminary cluster is transformed into a complete cluster.

[0058] S43, repeat step S42 to expand all temporary clusters until each point is already part of a cluster or is not in the neighborhood radius of any core point. At this time, all temporary clusters are converted into independent clusters. Finally, all sample points are in a cluster or are identified as noise points.

[0059] S44. Get target information:

[0060] Based on steps S41-S43, the average values ​​of the horizontal and vertical coordinates of all core points in each cluster are output to complete point condensation and obtain the distance and speed information of the target;

[0061] Among them, the average value of the horizontal and vertical coordinates of all core points in the cluster is the distance and speed information of the target corresponding to the cluster.

[0062] Beneficial effects of the present invention: The method of the present invention first sets radar signal parameters, transmits and processes radar signals to obtain an RD plane map, and then based on the RD plane map, uses the echo processing results of each sub-pulse signal to perform interference identification and elimination, and finally uses DBSCAN to perform point condensation on the processed RD plane map to obtain the distance and speed information of the target, thereby realizing the detection of the target. The method of the present invention can eliminate interference by transmitting multiple sub-pulses by multiple radars to avoid interference sampling and cooperative signal processing at the receiving end in the absence of interference prior information, and can realize the detection of targets in various interference environments, and has good anti-main lobe intermittent sampling interference performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 The present invention is a flow chart of a distributed multi-radar space-time-frequency domain collaborative anti-multi-mainlobe intermittent sampling interference method.

[0064] Figure 2 This is a time domain / frequency domain diagram of collaborative signals in a simulation scenario of space-time-frequency domain collaborative resistance to single random interference in an embodiment of the present invention.

[0065] Figure 3 This is a comparison chart of the mismatch filtering results of different transmitted signals in the space-time-frequency domain collaborative anti-single random interference simulation scenario in an embodiment of the present invention.

[0066] Figure 4 This is a comparison diagram of different transmission signal RD in the space-time-frequency domain collaborative anti-single random interference simulation scenario in an embodiment of the present invention.

[0067] Figure 5 This is a comparison chart of different transmission signal threshold decision results in the space-time-frequency domain collaborative anti-single random interference simulation scenario in an embodiment of the present invention.

[0068] Figure 6 This is a comparison chart of interference elimination results of different transmitted signals in a simulation scenario of collaborative anti-single random interference in the space-time-frequency domain in an embodiment of the present invention.

[0069] Figure 7 This is a comparison chart of the condensation results of different transmitted signal points in the space-time-frequency domain collaborative anti-single random interference simulation scenario in an embodiment of the present invention.

[0070] Figure 8 This is a time domain / frequency domain diagram of collaborative signals in a simulation scenario of space-time-frequency domain collaborative resistance to multiple random interferences in an embodiment of the present invention.

[0071] Fig. 9 This is a comparison chart of mismatch filtering results of different transmitted signals in a simulation scenario of collaborative anti-multiple random interferences in the space-time-frequency domain in an embodiment of the present invention.

[0072] Fig.10Comparison diagram of RD of different transmitted signals in the simulation scenario of space-time-frequency domain collaborative anti-multiple random interferences in an embodiment of the present invention.

[0073] Fig.11 Comparison diagram of different transmission signal threshold decision results in space-time-frequency domain collaborative anti-multiple random interference simulation scenarios in an embodiment of the present invention.

[0074] Fig.12 A comparison diagram of interference elimination results of different transmitted signals in a simulation scenario of collaborative anti-multiple random interferences in the space-time-frequency domain in an embodiment of the present invention.

[0075] Fig.13 A comparison diagram of the condensation results of different transmitted signal traces in the simulation scenario of collaborative anti-multiple random interferences in the space-time-frequency domain in an embodiment of the present invention.

[0076] Fig.14 This is a time domain / frequency domain diagram of the collaborative signal in the space-time-frequency domain collaborative anti-single cut-1-to-1 interference simulation scenario in an embodiment of the present invention.

[0077] Fig.15 This is a comparison chart of mismatch filtering results of different transmitted signals in a simulation scenario of collaborative anti-single cut-1-to-1 interference in the space-time-frequency domain in an embodiment of the present invention.

[0078] Fig.16 This is a comparison diagram of different transmission signal RDs in a simulation scenario of space-time-frequency domain collaborative anti-single cut-1-to-1 interference in an embodiment of the present invention.

[0079] Fig.17 This is a comparison chart of different transmission signal threshold decision results in the space-time-frequency domain collaborative anti-single cut-1-to-1 interference simulation scenario in an embodiment of the present invention.

[0080] Fig.18 This is a comparison chart of interference elimination results of different transmitted signals in the space-time-frequency domain collaborative anti-single cut-1-to-1 interference simulation scenario in an embodiment of the present invention.

[0081] Fig.19 This is a comparison chart of the condensation results of different transmission signal points in the space-time-frequency domain collaborative anti-single cut-1-to-1 interference simulation scenario in an embodiment of the present invention. DETAILED DESCRIPTION

[0082] The method of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0083] like Figure 1 As shown, a flow chart of a distributed multi-radar space-time-frequency domain collaborative anti-multi-main-lobe intermittent sampling interference method of the present invention is shown, and the specific steps are as follows:

[0084] S1. Set radar signal parameters and transmit radar signal;

[0085] S2, processing the signal obtained in step S1 to obtain an RD plane graph;

[0086] S3, performing interference identification and elimination based on the RD plane diagram obtained in step S2;

[0087] After the inter-pulse accumulation in step S2, interference identification and elimination are performed on the accumulation results. A threshold value ψ is set. The area in the RD result that exceeds the threshold value ψ is assigned a value of 1, and the area that does not exceed the threshold value ψ is assigned a value of 0. Then, data fusion is performed on the RD results of all sub-pulses: a logical "AND" operation is performed on all areas of each RD result to obtain the area where the real target exists.

[0088] S4, using DBSCAN to perform point condensation on the RD plane map after processing in step S3 to obtain the distance and speed information of the target;

[0089] The DBSCAN algorithm includes two important parameters: neighborhood radius and minimum point count threshold. The two parameters are used to explain the definition of dense in dense areas: when the number of points within the neighborhood radius of a point is greater than the minimum point count threshold, it is considered to be dense.

[0090] When the DBSCAN algorithm scans the samples, it divides the sample points into three categories: core points, boundary points, and noise points:

[0091] 1) The core point is the sample point whose number of sample points within the neighborhood radius is greater than the minimum point count threshold;

[0092] 2) Boundary points are sample points that are non-core points in the neighborhood of a core point;

[0093] 3) Sample points that are not core points or boundary points are noise points.

[0094] In this embodiment, the step S1 is specifically as follows:

[0095] Assuming that there are M sub-pulses in one pulse, and the sub-pulse signals transmitted by each station are linear frequency modulation signals with orthogonal frequencies, the expression of the multi-sub-pulse structure signal x(t) is as follows:

[0096]

[0097] Where t represents the pulse emission time, x m (t) represents the mth sub-pulse signal, represents the emission time of the mth sub-pulse, T m represents the duration of the mth sub-pulse. m (t) The specific expression is as follows:

[0098]

[0099] Among them, f m represents the carrier frequency of the mth sub-pulse, It represents the baseband signal form of the mth sub-pulse. The specific expression is as follows:

[0100]

[0101] Among them, μ m =B / T m represents the linear frequency modulation slope of the mth sub-pulse, and B represents the bandwidth of each sub-pulse.

[0102] In a PRT, the transmission signals of multiple transmission sites are spliced ​​into a long pulse; in a CPI, the pulse width, timing and bandwidth of the transmission signals of each site are kept unchanged, and the expression of a single pulse x(t) is as follows:

[0103]

[0104] Assuming that there are N pulses in 1 CPI, the expression of the transmitted signal s(t) in one CPI is as follows:

[0105]

[0106] Among them, t n =(n-1)T, where T represents the duration of a single pulse.

[0107] In this embodiment, step S2 is specifically as follows:

[0108] S21, obtaining an echo signal;

[0109] The transmitted signal s(t) is a narrowband signal. The target distance remains unchanged during the target detection process. Considering the case of a single point target, the expression of the echo signal y(t) is as follows:

[0110]

[0111] Among them, c represents the speed of light, R represents the target distance, v represents the radial velocity and is much smaller than the speed of light, and the time delay is approximately τ = 2R / c.

[0112] Since the carrier frequencies of each sub-pulse are different, the wavelength and Doppler shift are also different. The wavelength λ corresponding to each sub-pulse is m and Doppler shift The expressions are as follows:

[0113]

[0114] S22, multi-channel pulse compression, that is, using each sub-pulse transmission signal as a different mismatch filter to perform mismatch separation with the echo;

[0115] There are M sub-pulses in a pulse. M mismatch filters h are designed according to the M sub-pulses. m ,m=1,2,...,M, use different mismatch filters and echoes to perform mismatch separation.

[0116] The echo signal obtained in step S21 is y(t), which is converted into a fast and slow time dimension discrete matrix Y after sampling. Y(n,h) represents the hth sampling point of the nth pulse signal. Then the nth pulse signal of the echo passes through the output Z of the mth filter. m The expression of (n,τ) is as follows:

[0117]

[0118] S23, time domain shifting, that is, aligning the envelope of each mismatch separation result by time domain shifting for subsequent accumulation;

[0119] According to the emission time of different sub-pulses, the Z m (n,τ) is cyclically shifted K m units, and truncate the signal at time 0 to obtain the result Z′ of mismatch separation after time domain shifting m (n,τ).

[0120] in, k i Represents the length of each sub-pulse after discretization.

[0121] S24, accumulating the same sub-pulses between different pulses, i.e., accumulating each sub-result using non-uniform discrete Fourier transform (NUDFT) to obtain a sub-RD graph;

[0122] For the mth sub-pulse, set the maximum unambiguous velocity to v max , uniformly sample Q points in the unambiguous speed range and obtain the sequence v Q =[v1,v2,…,v Q ], define the row vector h m,q , the expression is as follows:

[0123]

[0124] Among them, v q =-v max +(q-1)(2v max / Q), q=1,2,…,Q;

[0125] Then construct the NUDFT transformation matrix The specific expression is as follows:

[0126]

[0127] in,() T represents the transpose of a matrix, Then the mismatch separation result Z′ of the mth sub-pulse after time domain shifting is m The NUDFT processing expression of (n,τ) is as follows:

[0128] β m (v,τ)=H m Z′ m

[0129] Among them, β m (v,τ) is the RD diagram of the mth sub-pulse.

[0130] In this embodiment, step S4 is specifically as follows:

[0131] S41, identifying core points;

[0132] For each sample point of the RD plane graph after processing in step S3, if the number of samples within its neighborhood radius (including itself) reaches or exceeds the preset minimum number of points, then this sample point is identified as a core point; then, this core point and all points within the neighborhood radius are combined into a preliminary temporary cluster;

[0133] S42, expansion of temporary clusters;

[0134] For the temporary cluster formed in step S41, all sample points are checked. If some points are found to be core points, all points in the neighborhood radius of these points are also added to the current temporary cluster. Repeat the expansion until no new core points can be added. At this time, the preliminary cluster is transformed into a complete cluster.

[0135] S43, repeat step S42 to expand all temporary clusters until each point is already part of a cluster or is not in the neighborhood radius of any core point. At this time, all temporary clusters are converted into independent clusters. Finally, all sample points are in a cluster or are identified as noise points.

[0136] S44. Get target information:

[0137] Based on steps S41-S43, the average values ​​of the horizontal and vertical coordinates of all core points in each cluster are output to complete point condensation and obtain the distance and speed information of the target;

[0138] Among them, the average value of the horizontal and vertical coordinates of all core points in the cluster is the distance and speed information of the target corresponding to the cluster.

[0139] This embodiment further performs simulation verification and analysis, including: space-time-frequency domain collaborative resistance to single random interference, space-time-frequency domain collaborative resistance to multiple random interferences, and space-time-frequency domain collaborative resistance to single cut-1-to-1 interference, as follows:

[0140] (1) Space-time-frequency domain collaboration to resist single random interference;

[0141] The simulation parameters of this embodiment are as follows: the target distance and speed are set to 160km and 200m / s, and the space-time-frequency domain anti-interference detection parameters are set as follows: the radar carrier frequency is 3GHz, and the available bandwidth of the cooperative signal is B s =800MHz, cooperative signal pulse repetition time T p′ =100μs, the number of repeated pulses in CPI is 64, the pulse width range of the sub-pulse at a single site is [5μs, 20μs], the first frequency point of the sub-pulse signal f1 = 40MHz, the frequency point spacing of the sub-pulse signal Δf = 80MHz, and the bandwidth of the sub-pulse signal B p =20MHz, SNR = 0dB, JNR = 15dB. Compare with the conventional LFM signal with a time width of 100μs, a bandwidth of 20MHz and a carrier frequency of 3GHz.

[0142] After receiving the signal, the adversary jammer samples and forwards the received signal with random interference sampling duration and interference sampling period within a certain range, and there is a random interference generation interval, that is, when the interference generation time at the current moment reaches the interference sampling interval, another interference signal is randomly generated, and the signal style of each interference generation is randomly selected between ISDRJ, ISPRJ and ISCRJ. The interference-related parameters of the adversary jammer are set as follows: the interference sampling duration is randomly selected between [2μs, 5μs], the interference sampling period is randomly selected between [10μs, 20μs], and the interference generation interval is randomly selected between [80μs, 150μs].

[0143] Simulation analysis: Figure 2 As shown, Figure 2 (a) is the time domain diagram of the cooperative signal. Figure 2 (b) is the frequency domain diagram of the cooperative signal. The cooperative signal in the time domain is composed of multiple sub-pulse signals spliced ​​into a long pulse, and the frequencies of each sub-pulse signal are orthogonal to each other. When the jammer receives the cooperative signal, it cannot make a judgment in the time domain and frequency domain to perform specific interference. It samples the signal from the first moment it receives the signal to perform intermittent sampling and forwarding interference.

[0144] like Figure 3 As shown, Figure 3 (a) is the cooperative signal mismatch filtering result, Figure 3 (b) is the traditional LFM signal mismatch filtering result. Figure 3(a) It can be seen that when transmitting the space-time-frequency domain coordinated signal, since the sub-pulse signal is sampled by interference, false target information appears in the mismatch filtering result. However, since the sampled sub-pulse signals are different, the interference in each filtering result is manifested in a different form, and the interference can be identified and processed based on this. Figure 3 (b) It can be seen that when transmitting the traditional existing LFM signal, the mismatch filtering result is greatly affected by the interference signal.

[0145] like Figure 4 As shown, Figure 4 (a), (b), and (c) are the 1st, 2nd, and 3rd sub-pulses RD of the cooperative signal, respectively. Figure 4 (d) is the traditional LFM signal RD, from Figure 4 (a), (b), and (c) show that the jammer can sample the sub-pulse signal and reflect it as false target information on the RD diagram. When transmitting the space-time-frequency domain cooperative signal, the sub-pulse signal corresponding to certain moments will be severely sampled, resulting in a large amount of interference information in the result of sub-pulse signal processing, such as Figure 4 (b); At the same time, there are also cases where only a small part of some sub-pulse signals are sampled by interference, and the interference component in the RD diagram result is weakened compared with other results, such as Figure 4 (a) Subsequently, each RD graph is judged and processed, and the interference with lower amplitude is first eliminated, and then the interference is identified and eliminated according to each judgment result.

[0146] like Figure 5 As shown, Figure 5 (a), (b), and (c) are the threshold decision results of the 1st, 2nd, and 3rd sub-pulses of the coordinated signal, respectively. Figure 5 (d) is the traditional LFM signal threshold decision result. Figure 5 (a), (b), and (c) show that when transmitting space-time-frequency domain cooperative signals, the results of each RD diagram after threshold judgment are different, but they all have values ​​near the target parameter position (distance 160km, speed 200m / s). Therefore, interference identification and elimination can be performed based on all judgment results, that is, the positions where all judgment results have values ​​are regarded as having targets, and the rest are interference, thereby eliminating the interference at different positions.

[0147] like Figure 6 As shown, Figure 6 (a) is the result of cooperative signal interference elimination, Figure 6 (b) is the result of traditional LFM signal interference elimination. Figure 6(a) It can be seen that when transmitting space-time-frequency domain coordinated signals, after the interference is eliminated, the interference items on the threshold decision result are cleared, and detection results only exist at 160km, 200m / s and a small range nearby. The space-time-frequency domain anti-interference detection task is basically successful, and the influence of intermittent sampling forwarding interference is successfully suppressed.

[0148] like Figure 7 As shown, Figure 7 (a) is the result of collaborative signal point aggregation. Figure 7 (b) is the result of traditional LFM signal trace aggregation. Figure 7 (a) It can be seen that when transmitting space-time-frequency domain cooperative signals, after the point traces are condensed, the condensed result shows that there is a point target at 160km and 200m / s, which is consistent with the simulation parameter settings, verifying the effectiveness of the method of the present invention.

[0149] It can be seen from Figures 4(d), 5(d), 6(b), and 7(b) that the target position cannot be correctly obtained when the traditional LFM signal is transmitted.

[0150] (2) Space-time-frequency domain collaboration to resist multiple random interferences;

[0151] The simulation parameters of this embodiment are as follows: the target distance and speed are set to 100km and 150m / s, and the space-time-frequency domain anti-interference detection parameters are set as follows: the radar carrier frequency is 3GHz, and the available bandwidth of the cooperative signal is B s =800MHz, cooperative signal pulse repetition time T p′ =100μs, the number of repeated pulses in CPI is 64, the pulse width range of the sub-pulse at a single site is [5μs, 20μs], the first frequency point of the sub-pulse signal f1 = 40MHz, the frequency point spacing of the sub-pulse signal Δf = 80MHz, and the bandwidth of the sub-pulse signal B p =20MHz, SNR = 0dB, JNR = 15dB. Compare with the conventional LFM signal with a time width of 100μs, a bandwidth of 20MHz and a carrier frequency of 3GHz.

[0152] Considering that the adversary has three jammers, and each jammer works independently, after receiving the signal, the adversary jammer samples and forwards the received signal with a random interference sampling duration and interference sampling period within a certain range, and there is a random interference generation interval, that is, when the interference generation time at the current moment reaches the interference sampling interval, another interference signal is randomly generated, and the signal style of each interference generation is randomly selected between ISDRJ, ISPRJ and ISCRJ. The interference-related parameters of the adversary jammer are set as follows: the interference sampling duration is randomly selected between [2μs, 5μs], the interference sampling period is randomly selected between [10μs, 20μs], and the interference generation interval is randomly selected between [80μs, 150μs].

[0153] Simulation analysis: Figure 8 As shown, Figure 8 (a) is the time domain diagram of the cooperative signal. Figure 8 (b) is the frequency domain diagram of the cooperative signal. The cooperative signal in the time domain is composed of multiple sub-pulse signals spliced ​​into a long pulse, and the frequencies of each sub-pulse signal are orthogonal to each other. When the jammer receives the cooperative signal, it cannot make a judgment in the time domain and frequency domain to perform specific interference. It samples the signal from the first moment it receives the signal to perform intermittent sampling and forwarding interference.

[0154] like Fig. 9 As shown, Fig. 9 (a) is the cooperative signal mismatch filtering result, Fig. 9 (b) is the traditional LFM signal mismatch filtering result. Fig. 9 (a) It can be seen that when transmitting the space-time-frequency domain cooperative signal, since the sub-pulse signal is sampled by interference, false target information appears in the mismatch filtering result. Compared with the single interference case, in the case of multiple interferences, more false target information caused by interference signals appears in the mismatch filtering result; Fig. 9 (b) It can be seen that when transmitting a traditional LFM signal, the mismatch filtering result is greatly affected by the interference signal.

[0155] like Fig.10 As shown, Fig.10 (a), (b), and (c) are the 1st, 2nd, and 3rd sub-pulses RD of the cooperative signal, respectively. Fig.10 (d) is the traditional LFM signal RD, from Fig.10 (a), (b), and (c) show that the jammer can sample the sub-pulse signal and reflect it as false target information on the RD diagram. When transmitting coordinated signals in the space-time-frequency domain, the sub-pulse signal corresponding to certain moments will be severely sampled, resulting in a large amount of interference information in the sub-pulse signal processing results.

[0156] like Fig.11 As shown, Fig.11 (a), (b), and (c) are the threshold decision results of the 1st, 2nd, and 3rd sub-pulses of the coordinated signal, respectively. Fig.11 (d) is the traditional LFM signal threshold decision result. Fig.11 (a), (b), and (c) show that when transmitting space-time-frequency domain cooperative signals, the results of each RD diagram after threshold judgment are different. Compared with the single interference case, in the multiple interference case, more false target information caused by interference signals appears in the RD diagram, but all of them have values ​​near the target parameter position (distance 100km, speed 150m / s). Therefore, interference identification and elimination can be performed based on all judgment results, that is, the positions where all judgment results have values ​​are considered to have targets, and the rest are interference, thereby eliminating interference at different positions.

[0157] like Fig.12 As shown, Fig.12 (a) is the result of cooperative signal interference elimination, Fig.12 (b) is the result of traditional LFM signal interference elimination. Fig.12 (a) It can be seen that when transmitting space-time-frequency domain cooperative signals, after the interference is eliminated, the interference items on the threshold decision result are cleared, and detection results only exist at 100km, 150m / s and a small range nearby. The space-time-frequency domain anti-interference detection task is basically successful, and the influence of intermittent sampling forwarding interference is successfully suppressed.

[0158] like Fig.13 As shown, Fig.13 (a) is the result of collaborative signal point aggregation. Fig.13 (b) is the result of traditional LFM signal trace aggregation. Fig.13 (a) It can be seen that when transmitting space-time-frequency domain cooperative signals, after the point traces are condensed, the condensed result shows that there is a point target at 99.9997km and 150m / s, which is consistent with the simulation parameter settings, verifying the effectiveness of the method of the present invention.

[0159] from Fig.10 (d), 11(d), 12(b), and 13(b), it can be seen that the target position cannot be correctly obtained when the traditional LFM signal is transmitted.

[0160] (3) Space-time-frequency domain collaboration to resist single cut-1-to-1 interference;

[0161] The simulation parameters of this embodiment are as follows: the target distance and speed are set to 100 km and 100 m / s, and the space-time-frequency domain anti-interference detection parameters are set as follows: the radar carrier frequency is 3 GHz, and the available bandwidth of the cooperative signal is B s =800MHz, cooperative signal pulse repetition time T p′=100μs, the number of repeated pulses in CPI is 64, the pulse width range of the sub-pulse at a single site is [5μs, 20μs], the first frequency point of the sub-pulse signal f1 = 40MHz, the frequency point spacing of the sub-pulse signal Δf = 80MHz, and the bandwidth of the sub-pulse signal B p =20MHz, SNR = 0dB, JNR = 15dB. Compare with the conventional LFM signal with a time width of 100μs, a bandwidth of 20MHz and a carrier frequency of 3GHz.

[0162] The known working limit of the current jammer is to sample 1μs and then immediately forward the sampled 1μs length slice. Therefore, after the adversary jammer receives the signal, it samples and forwards the received signal in the working mode of "cut 1μs to 1μs".

[0163] Simulation analysis: Fig.14 As shown, Fig.14 (a) is the time domain diagram of the cooperative signal. Fig.14 (b) is the frequency domain diagram of the cooperative signal. The cooperative signal in the time domain is composed of multiple sub-pulse signals spliced ​​into a long pulse, and the frequencies of each sub-pulse signal are orthogonal to each other. When the jammer receives the cooperative signal, it cannot make a judgment in the time domain and frequency domain to perform specific interference. It samples the signal from the first moment it receives the signal to perform intermittent sampling and forwarding interference.

[0164] like Fig.15 As shown, Fig.15 (a) is the cooperative signal mismatch filtering result, Fig.15 (b) is the result of traditional LFM signal mismatch filtering; Fig.16 As shown, Fig.16 (a), (b), and (c) are the 1st, 2nd, and 3rd sub-pulses RD of the cooperative signal, respectively. Fig.16 (d) is the traditional LFM signal RD; Fig.17 As shown, Fig.17 (a), (b), and (c) are the threshold decision results of the 1st, 2nd, and 3rd sub-pulses of the cooperative signal, respectively. Fig.17 (d) is the traditional LFM signal threshold decision result.

[0165] from Fig.15 (a), 16(a), (b), (c), 17(a), (b), (c), it can be seen that when the jammer speeds up the sampling rhythm, the probability of the sub-pulse signal being sampled increases, making it difficult to obtain the target information in the intermediate process of signal processing.

[0166] like Fig.18 As shown, Fig.18 (a) is the result of cooperative signal interference elimination, Fig.18 (b) is the result of traditional LFM signal interference elimination; Fig.19 As shown, Fig.19 (a) is the result of collaborative signal point aggregation. Fig.19 (b) is the result of traditional LFM signal point aggregation.

[0167] from Fig.18 (a) and 19(a) show that after the interference is eliminated and the traces are condensed, the condensed result shows that there is a point target at 100.15km and 100m / s, which is consistent with the simulation parameter settings, verifying the effectiveness of the method of the present invention. Although the jammer speeds up the sampling rhythm, which affects the probability of each sub-pulse being sampled and the signal processing result of the sub-pulse, the real target information can still be obtained through the subsequent collaborative signal processing of the collaborative strategy.

[0168] from Fig.15 (b), 16(d), 17(d), 18(b), and 19(b), it can be seen that the target position cannot be correctly obtained when the traditional LFM signal is transmitted.

[0169] In summary, compared with the traditional LFM signal, the distributed multi-radar space-time-frequency domain collaborative anti-multi-mainlobe intermittent sampling interference method proposed by the method of the present invention can avoid interference sampling by multi-radar transmitting multiple sub-pulses and perform collaborative signal processing at the receiving end in the absence of interference prior information. It can detect targets in various interference environments and has good anti-mainlobe intermittent sampling interference performance.

[0170] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific variations and combinations that do not deviate from the essence of the present invention based on the technical revelations disclosed by the present invention, and these variations and combinations are still within the protection scope of the present invention.

Claims

1. A distributed multi-radar space-time-frequency domain collaborative anti-multi-mainlobe intermittent sampling interference method, the specific steps are as follows: S1. Set radar signal parameters and transmit radar signal; S2, processing the signal obtained in step S1 to obtain an RD plane graph; S3, performing interference identification and elimination based on the RD plane diagram obtained in step S2; Step S2: After the pulse-to-pulse accumulation, the accumulated results are subjected to interference identification and elimination. A threshold value ψ is set. The area in the RD result that exceeds the threshold value ψ is assigned a value of 1, and the area that does not exceed the threshold value ψ is assigned a value of 0. Then, the RD results of all sub-pulses are subjected to data fusion: all areas of each RD result are subjected to a logical "AND" operation to obtain the area where the real target exists. S4, using DBSCAN to perform point condensation on the RD plane map after processing in step S3 to obtain the distance and speed information of the target; The DBSCAN algorithm includes two important parameters: neighborhood radius and minimum point count threshold. The two parameters are used to explain the definition of dense in dense areas: when the number of points within the neighborhood radius of a point is greater than the minimum point count threshold, it is considered to be dense. When the DBSCAN algorithm scans the samples, it divides the sample points into three categories: core points, boundary points, and noise points: 1) The core point is the sample point whose number of sample points within the neighborhood radius is greater than the minimum point count threshold; 2) Boundary points are sample points that are non-core points in the neighborhood of a core point; 3) Sample points that are not core points or boundary points are noise points.

2. According to claim 1, a distributed multi-radar space-time-frequency domain collaborative anti-multi-mainlobe intermittent sampling interference method is characterized in that: The step S1 is specifically as follows: Assuming that there are M sub-pulses in one pulse, and the sub-pulse signals transmitted by each station are linear frequency modulation signals with orthogonal frequencies, the expression of the multi-sub-pulse structure signal x(t) is as follows: Where t represents the pulse emission time, x m (t) represents the mth sub-pulse signal, represents the emission time of the mth sub-pulse, T m represents the duration of the mth sub-pulse; x m (t) The specific expression is as follows: Among them, f m represents the carrier frequency of the mth sub-pulse, It represents the baseband signal form of the mth sub-pulse. The specific expression is as follows: Among them, μ m =B / T m represents the linear frequency modulation slope of the mth sub-pulse, and B represents the bandwidth of each sub-pulse; In a PRT, the transmission signals of multiple transmission sites are spliced ​​into a long pulse; in a CPI, the pulse width, timing and bandwidth of the transmission signals of each site are kept unchanged, and the expression of a single pulse x(t) is as follows: Assuming that there are N pulses in 1 CPI, the expression of the transmitted signal s(t) in one CPI is as follows: Among them, t n =(n-1)T, where T represents the duration of a single pulse.

3. The distributed multi-radar space-time-frequency domain collaborative anti-multi-mainlobe intermittent sampling interference method according to claim 1 is characterized in that: The step S2 is specifically as follows: S21, obtaining an echo signal; The transmitted signal s(t) is a narrowband signal. The target distance is assumed to remain unchanged during the target detection process. Considering the case of a single point target, the expression of the echo signal y(t) is as follows: Where c represents the speed of light, R represents the target distance, v represents the radial velocity and is much smaller than the speed of light, and the time delay is approximately τ = 2R / c; Since the carrier frequencies of each sub-pulse are different, the wavelength and Doppler shift are also different. The wavelength λ corresponding to each sub-pulse is m and Doppler shift The expressions are as follows: S22, multi-channel pulse compression, that is, using each sub-pulse transmission signal as a different mismatch filter to perform mismatch separation with the echo; There are M sub-pulses in a pulse. M mismatch filters h are designed according to the M sub-pulses. m ,m=1,2,...,M, use different mismatch filters and echoes for mismatch separation; The echo signal obtained in step S21 is y(t), which is converted into a fast and slow time dimension discrete matrix Y after sampling. Y(n,h) represents the hth sampling point of the nth pulse signal. Then the nth pulse signal of the echo passes through the output Z of the mth filter. m The expression of (n,τ) is as follows: S23, time domain shifting, that is, aligning the envelope of each mismatch separation result by time domain shifting for subsequent accumulation; According to the emission time of different sub-pulses, the Z m (n,τ) is cyclically shifted K m units, and truncate the signal at time 0 to obtain the result Z′ of mismatch separation after time domain shifting m (n,τ); in, k i represents the length of each sub-pulse after discretization; S24, accumulating the same sub-pulses between different pulses, i.e., accumulating each sub-result using non-uniform discrete Fourier transform (NUDFT) to obtain a sub-RD graph; For the mth sub-pulse, set the maximum unambiguous velocity to v max , uniformly sample Q points in the unambiguous speed range and obtain the sequence v Q =[v1,v2,…,v Q ], define the row vector h m,q , the expression is as follows: Among them, v q =-v max +(q-1)(2v max / Q), q=1,2,…,Q; Then construct the NUDFT transformation matrix The specific expression is as follows: in,() T represents the transpose of a matrix, Then the mismatch separation result Z′ of the mth sub-pulse after time domain shifting is m The NUDFT processing expression of (n,τ) is as follows: β m (v,τ)=H m Z′ m Among them, β m (v,τ) is the RD diagram of the mth sub-pulse.

4. The distributed multi-radar space-time-frequency domain collaborative anti-multi-mainlobe intermittent sampling interference method according to claim 1 is characterized in that: The step S4 is specifically as follows: S41, identifying core points; For each sample point of the RD plane graph after processing in step S3, if the number of samples within its neighborhood radius reaches or exceeds the preset minimum number of points, then this sample point is identified as a core point; then, this core point and all points within the neighborhood radius are combined into a preliminary temporary cluster; S42, expansion of temporary clusters; For the temporary cluster formed in step S41, all sample points are checked. If some points are found to be core points, all points in the neighborhood radius of these points are also added to the current temporary cluster. Repeat the expansion until no new core points can be added. At this time, the preliminary cluster is transformed into a complete cluster. S43, repeat step S42 to expand all temporary clusters until each point is already part of a cluster or is not in the neighborhood radius of any core point. At this time, all temporary clusters are converted into independent clusters. Finally, all sample points are in a cluster or are identified as noise points. S44. Get target information: Based on steps S41-S43, the average values ​​of the horizontal and vertical coordinates of all core points in each cluster are output to complete point condensation and obtain the distance and speed information of the target; Among them, the average value of the horizontal and vertical coordinates of all core points in the cluster is the distance and speed information of the target corresponding to the cluster.

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