An anti-dense false target jamming method based on complex empirical mode decomposition

Abstract

This invention discloses a method for resisting dense false target interference based on complex empirical mode decomposition, comprising the following steps: S1: detecting false targets; S2: performing CEMD decomposition on each group of pulse echoes in the false targets to obtain several intrinsic mode functions (IMFs); S3: solving for the centroid IMF based on the IMFs and the phase projection direction. ZX The projections in all directions are averaged, and the centroid IMF is calculated. ZX S4: Recover the intrinsic mode function (IMF); S5: Solve the centroid IMF of each pulse echo. ZX The intrinsic mode function (IMF) components with high correlation to the transmitted signal are retained, while those with poor correlation are removed, resulting in a multi-pulse signal after interference suppression. The purpose of this invention is to suppress the dense false target deception interference suffered by traditional radar systems.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of radar anti-dense false target jamming, and particularly relates to a method for anti-dense false target jamming based on complex empirical mode decomposition. BACKGROUND

[0002] The final purpose of deception jamming suppression is to better detect targets. When deception jamming occurs, it will cause tracking of false targets or loss of tracking of targets. Therefore, for typical dense false target jamming, the application intends to adopt complex empirical mode decomposition (CEMD) phase interference suppression technology to perform frequency screening on the deception jamming in the frequency domain, eliminate frequency components other than targets, complete interference suppression, and then improve the SINR through phase comparison.

[0003] The dense false target deception jamming transmits a plurality of deception jamming signals according to a series of time intervals and modulation rules in advance, can produce deception effects on radars, and can consume radar resources by using a large number of jamming signals to make the radars work in a saturated state. When the radar receives a time domain waveform, due to the distance false target jamming, the time domain parts of a plurality of LFM signals with similar parameters are superimposed, and at this time, it is difficult to see the characteristics of the LFM signals in the time domain. If the distance false target jamming in the received signal is not suppressed in advance, the AGC of the radar receiver will automatically adjust the gain to adapt to the distance false target, and the false target jamming will be treated as a real target. For a tracking radar, it is more likely to track the false target and lose the real target, which will cause great threat and damage to the radar.

[0004] When the radar transmitted signal is a linear frequency modulation (LFM) signal, the dense false target has the same expression as the transmitted signal, and the difference lies in that the time delay of each pulse is different, thereby giving the radar false distance and speed information to achieve the purpose of jamming and deception. By using digital radio frequency storage technology, the jammer can quickly sample and store the radar signal, then modulate the time delay and amplitude of the signal and other parameters, and then retransmit the signal to the radar, so that a large number of false target jamming exists in the electromagnetic space. After the radar receiver is jammed by the dense false target, it cannot accurately distinguish the real target echo, which affects the working state of the radar. The existing technology has limited suppression effect on the dense false target jamming, so it is necessary to study the radar anti-dense false target jamming technology. SUMMARY

[0005] The purpose of this invention is to suppress the interference from dense enemy decoys when traditional radar detects targets in the airspace. After performing CEMD decomposition on the echo signal in the time domain, the centroid intrinsic mode function (IMF) is used to correlate with the transmitted signal to find the IMF component where the dense decoy interference is located. Then, multi-pulse echo deception interference is eliminated. After eliminating the interference, the multi-pulse is coherently accumulated to achieve suppression of dense decoy interference and improvement of SINR.

[0006] The specific technical solution of the present invention is as follows:

[0007] A method for resisting dense false target interference based on complex empirical mode decomposition includes the following steps:

[0008] S1: Detect false targets;

[0009] S2: Perform CEMD decomposition on each group of pulse echoes in the dummy target to obtain several intrinsic mode functions (IMFs);

[0010] The CEMD decomposition formula is as follows:

[0011]

[0012] In the formula, the number of false targets in the dense false target jamming is N, T is the pulse width of the transmitted signal, and t r It is the time delay corresponding to the distance between the target and the radar; while t ji ,i=1,…,N represent the deception jamming delay added by the jammer to deceive the radar, f c f is the carrier frequency of the echo signal. d It is the Doppler frequency of the real target, f dj ,j=1,...,N represent the Doppler frequencies of the dense decoy interference in the spectrum; A ji These represent the amplitudes of the dense decoy target deception interference in the time domain, and the amplitudes are summed and accumulated.

[0013] S3: According to the intrinsic mode function (IMF), the phase projection direction is... Solving for the centroid IMF ZX The projections in all directions are averaged, and the centroid IMF is calculated. ZX Recovery is performed using the intrinsic mode function (IMF).

[0014] S4: The centroid IMF obtained from each pulse echo. ZX The intrinsic mode function (IMF) components with high correlation to the transmitted signal are retained, while those with poor correlation are removed, resulting in a multi-pulse signal with interference suppression.

[0015] S5: Perform coherent accumulation of the multi-pulse signal after interference suppression, and verify the position of the real target by comparing the time-frequency diagram and the pulse compression diagram. Then, plot the time domain, frequency domain, and Doppler domain information of the suppressed signal to complete the suppression of dense false target interference.

[0016] Preferably, S1 includes the following sub-steps:

[0017] S11: Create time-domain and frequency-domain images of the obtained pulse signals;

[0018] S12: Fast time-dimensional pulse compression is performed on the transmitted signal in the range domain to obtain a mixed pulse compression map of the false target and the real target, and the characteristics of the false target are consistent with those of the real target.

[0019] Preferably, S2 includes the following sub-steps:

[0020] S21: The zero-mean component is extracted by progressively obtaining the maximum and minimum envelopes;

[0021] S22: Decompose the signal step by step into intrinsic eigenfunctions (IMFs).

[0022] in Represents each IMF of the signal decomposition, r n (t) represents the residual after decomposition, and n represents the number of modes obtained from the decomposition.

[0023] S23: Since the signal rotates in the Z-domain, to prevent abrupt changes in the signal rotation at a certain moment, and to realize the projection of the complex signal in a certain direction on the rotation plane when rotating, the centroid of the "pipeline" of the intrinsic mode function (IMF) obtained after CEMD decomposition is calculated. Its calculation formula is: IMF ZX = (c1(t) + c2(t) + ... + c n (t)) / n.

[0024] Preferably, in S3, by recovering the centroid IMF from the intrinsic IMF, the phase and amplitude characteristics of the "pipeline" centroid IMF are made to correspond to the intrinsic IMF obtained by direct decomposition of CEMD.

[0025] Preferably, S4 includes the following sub-steps:

[0026] S41: Solve for the centroid IMF of each set of pulse echoes. ZX Perform a correlation test with the transmitted signal;

[0027] S42: The centroid IMF, which has a high correlation with the transmitted signal. ZX Component retention, centroid IMF with poor correlation ZX Components are removed.

[0028] Preferably, the correlation test is the Pearson correlation coefficient method; its formula is:

[0029]

[0030] Where Cov(·) represents the covariance matrix operation, Var(·) represents the variance operation, and r s This represents a reference signal.

[0031] The beneficial effects of this invention are as follows:

[0032] 1. The purpose of this invention is to suppress the interference from dense false targets encountered by traditional radar during air detection. After performing CEMD decomposition on the echo signal in the time domain, the centroid of the complex signal rotation "pipe" is obtained, and the intrinsic mode function (IMF) of the interfering target is removed in the time domain. Then, the suppressed signal is coherently accumulated to complete the reconstruction and recovery of the real target signal, thereby suppressing the interference from dense false targets.

[0033] 2. This invention utilizes the complex empirical mode decomposition method to eliminate false targets without disrupting the transmitted signal spectrum. Attached Figure Description

[0034] Figure 1 This is a flowchart of the present invention.

[0035] Figure 2 This is a comparison diagram of the coherent accumulation spectrum before and after anti-interference of the 128-pulse unit of the present invention.

[0036] Figure 3 is a comparison diagram of coherent accumulation delay-Doppler before and after anti-interference of the 128-pulse unit of the present invention. Detailed Implementation

[0037] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0038] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0039] like Figure 1 As shown, a shock resistance method based on period estimation in clutter backgrounds includes the following steps:

[0040] Step 1: False Target Detection. First, the obtained pulse signals are plotted in the time and frequency domains. Then, fast time-dimensional pulse compression is performed on the transmitted signal in the range domain to obtain a mixed pulse compression map of false and real targets. The characteristics of the false targets are almost identical to those of the real targets, thus false target detection can be achieved.

[0041] Step 2: Interference Component Removal. Each group of pulse echoes is decomposed into several Intrinsic Mode Functions (IMFs) using CEMD. The main method involves progressively obtaining the maximum and minimum envelopes to extract the zero-mean component, gradually decomposing the signal under study into IMFs. Then, the centroid of the "pipeline" of the IMFs obtained after CEMD decomposition is determined. The centroid IMFs are then recovered from the IMFs, and the correlation between the centroid IMFs obtained from each group of pulse echoes and the transmitted signal is checked. IMF components with high correlation to the transmitted signal are retained, while those with poor correlation are removed.

[0042] Step 3: False Target Suppression. The suppressed multi-pulse signal is coherently accumulated. Based on the comparison between the time-frequency plot and the pulse compression plot, the position of the real target is verified. The time domain, frequency domain, and Doppler domain information of the suppressed signal are plotted, thus completing the suppression of dense false target interference.

[0043] Taking a set of simulation data as an example, the simulation data pulse dimension has 128 pulse units (or slow time sampling units), and a single pulse includes 10,000 distance units.

[0044] In step one: the echo data detected each time is a group of simulated pulse data. The grouping method is as follows: the original matrix is ​​grouped along the distance dimension, with a group of 10,000 distance units, which are then input into the false target detection pulse compression response function.

[0045] In step one, when detecting false target interference, fast time-dimensional pulse compression is performed on the transmitted signal in the range domain to obtain the pulse compression maps of the false target and the real target. The characteristics of the false target are almost identical to those of the real target, so false target detection can be achieved; the time position of the main lobe pulse compression peak is recorded.

[0046] In step two, using the number and location of the false target interference obtained, the maximum and minimum envelopes are obtained step by step to extract the zero-mean component, and the signal under study is decomposed into intrinsic functions (IMFs) step by step. The centroid IMFs obtained from each set of pulse echoes are then compared with the transmitted signal for correlation testing. IMF components with high correlation with the transmitted signal are retained, while IMF components with poor correlation are removed.

[0047] In step three, the multi-pulse signal after interference suppression is coherently accumulated. Based on the comparison of the time-frequency diagram and pulse compression diagram before and after interference suppression, the position of the real target is verified, and the time domain, frequency domain, and Doppler domain information of the suppressed signal are plotted, thus completing the suppression of dense false target interference. Figure 2 As can be seen, when suppressing false target interference, only the frequency components of the false targets are removed, and the spectrum of the transmitted signal is almost preserved. This not only removes the false target interference but also maintains the integrity of the original transmitted signal spectrum. Figures 3(a) and 3(b) show the coherent accumulation delay-Doppler plots before and after the 128-pulse unit anti-interference, and the arrows indicate the locations where the real targets appear.

[0048] Compared to the moving target detection MTI method, the dense false target interference suppression method based on complex empirical mode decomposition can effectively suppress false target interference and has better suppression performance.

[0049] In summary, the beneficial effects of this invention are that it uses a dense false target interference suppression method based on complex empirical mode decomposition with low computational complexity, which can suppress dense false target interference in traditional radar systems, effectively improving the false target suppression performance under interference backgrounds. Furthermore, by utilizing the echo signal reconstruction method, interference frequency components are eliminated without disrupting the transmitted signal spectrum, and the SINR can be improved by 45.8579 dB after coherence.

[0050] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for resisting dense false target interference based on complex empirical mode decomposition, characterized in that, Includes the following steps: S1: Detect false targets; S2: Perform CEMD decomposition on each group of pulse echoes in the dummy target to obtain several intrinsic mode functions (IMFs); the pulse echoes of the dummy target are: ， In the formula, the number of false targets in the dense false target interference is: indivual, It is the pulse width of the transmitted signal. It is the sampling moment in the fast time dimension. It is the time delay corresponding to the distance between the target and the radar; and These represent the deception jamming delay added by the jammer to deceive the radar. For the echo signal carrier frequency, It is the Doppler frequency of the real target. These represent the Doppler frequencies of dense decoy interference in the spectrum; These represent the amplitudes of the dense decoy target deception interference in the time domain, and the amplitudes are summed and accumulated. The CEMD decomposition formula is as follows: ， in, Representing each IMF in the signal decomposition, The remainder after decomposition, where n represents the number of modes obtained from the decomposition; S3: According to the intrinsic mode function (IMF), the phase projection direction is... Solve for the center of mass. The projections from all directions are averaged, and the centroid is... Recovery is performed using the intrinsic mode function (IMF). S4: The centroids obtained from each pulse echo. The intrinsic mode function (IMF) components with high correlation to the transmitted signal are retained, while those with poor correlation are removed, resulting in a multi-pulse signal with interference suppression. S5: Perform coherent accumulation of the multi-pulse signal after interference suppression, and verify the position of the real target by comparing the time-frequency diagram and the pulse compression diagram. Then, plot the time domain, frequency domain, and Doppler domain information of the suppressed signal to complete the suppression of dense false target interference.

2. The method for resisting dense false target interference based on complex empirical mode decomposition according to claim 1, characterized in that, S1 includes the following sub-steps: S11: Create time-domain and frequency-domain images of the obtained pulse signals; S12: Fast time-dimensional pulse compression is performed on the transmitted signal in the range domain to obtain a mixed pulse compression map of the false target and the real target, and the characteristics of the false target are consistent with those of the real target.

3. The method for resisting dense false target interference based on complex empirical mode decomposition according to claim 1, characterized in that, S2 includes the following sub-steps: S21: The zero-mean component is extracted by progressively obtaining the maximum and minimum envelopes; S22: Decompose the signal step by step into intrinsic eigenfunctions (IMFs). , in, Representing each IMF in the signal decomposition, The remainder after decomposition, where n represents the number of modes obtained from the decomposition; S23: Since the signal rotates in the Z-domain, to prevent abrupt changes in the signal rotation at a certain moment, and to realize the projection of the complex signal in a certain direction on the rotation plane when rotating, the centroid of the pipe of the intrinsic mode function (IMF) obtained after CEMD decomposition is calculated. The calculation formula is as follows: .

4. The method for resisting dense false target interference based on complex empirical mode decomposition according to claim 1, characterized in that, In step S3, by recovering the centroid IMF from the intrinsic IMF, the phase and amplitude characteristics of the pipeline centroid IMF are made to correspond with the intrinsic IMF obtained by direct decomposition of CEMD.

5. The method for resisting dense false target interference based on complex empirical mode decomposition according to claim 1, characterized in that, S4 includes the following sub-steps: S41: The centroid obtained from each set of pulse echoes Perform a correlation test with the transmitted signal; S42: The centroid with high correlation to the transmitted signal... Component retention, centroids with poor correlation Components are removed.

6. The method for resisting dense false target interference based on complex empirical mode decomposition according to claim 5, characterized in that, The correlation test is the Pearson correlation coefficient method; The formula is: ， in, Represents the operation of the covariance matrix. Represents variance calculation. This represents a reference signal.

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