CN118244210B - Intermittent sampling forwarding interference active countermeasure method, device and system - Google Patents

Abstract

The invention relates to an intermittent sampling forwarding interference active countermeasure method, device and system. The method mainly comprises the following steps: designing a transmitting waveform of a transmitting signal, wherein the transmitting waveform comprises a plurality of sub-pulses, the central frequency and the frequency modulation slope of the sub-pulses are adopted to be changed rapidly, and time delay is inserted between adjacent sub-pulses; dividing an echo signal into a plurality of slices according to the pulse width of a transmitting signal sub-pulse, and setting zero for signals in echo slices at corresponding positions according to the time delay positions inserted between the transmitting signal sub-pulses; identifying each other echo slice except the zero echo slice, and judging whether the echo slice is an interfered echo slice or a non-interference echo slice; constructing a sparse matrix of a fractional order domain, and reconstructing a target and interference in the interfered echo slice by using a compressed sensing algorithm; and constructing a time domain narrow-band filter by using the undisturbed echo slice, and further filtering the echo pulse pressure output after target reconstruction. The invention can reduce the range side lobe caused by residual interference.

Description

Intermittent sampling forwarding interference active countermeasure method, device and system

Technical Field

The present invention relates to the field of electronic countermeasure technologies, and in particular, to an intermittent sampling forwarding interference active countermeasure method, device, and system.

Background

Since the advent of radar, there have been significant challenges from interfering parties. In particular, with the continued development of electronic technology, the various interferences generated based on digital radio frequency memory technology (Digital Radio Frequency Memory, abbreviated as DRFM) worsen the electromagnetic environment in which the radar is located. Wherein intermittent sampled SAMPLING REPEATER Jamming (abbreviated as ISRJ) is a type of spoofing interference that the DRFM system transmits signals, stores and forwards through the sampled portion. ISRJ, due to the correlation with the radar emission signal, can form a false target with strong energy at a low power cost, which affects radar detection. In addition, ISRJ can be applied to a small-sized jammer platform for assembling a transceiving time-sharing antenna due to an intermittent sampling mechanism, and a great threat is brought to a radar side.

In recent years, radar target detection and anti-interference means are endless. ISRJ is an intra-pulse disturbance, so that conventional inter-pulse waveform agility, frequency agility, etc. techniques are not effective. Also ISRJ is often favored as self-defense interference by the interfering party, which results in an undesirable suppression effect of the spatial domain method. In recent years, many scholars have developed related studies with respect to ISRJ against the challenge problem. The literature relevant for interference rejection can be largely divided into two categories. One is a receiving end signal processing method, and the other is an anti-interference method based on a transmitting waveform design.

For the signal processing method at the receiving end, the signal transmitted by the radar is a linear frequency modulation (linear frequency modulation, abbreviated as LFM) signal. In documents [Yuan,H.;Wang,C.;Li,X.;An,L. A Method against Interrupted-Sampling Repeater Jamming Based on Energy Function Detection and Band-Pass Filtering. International Journal of Antennas and Propagation 2017,2017,6759169,doi：10.1155/2017/6759169.]、[Chen,J.;Wu,W.;Xu,S.;Chen,Z.;Zou,J. Band pass filter design against interrupted-sampling repeater jamming based on time-frequency analysis. IET Radar,Sonar&Navigation 2019,13,1646-1654,doi：10.1049/iet-rsn.2018.5658.]、[Wang,Z.;Li,J.;Yu,W.;Luo,Y.;Zhao,Y.;Yu,Z. Energy function-guided histogram analysis for interrupted sampling repeater jamming suppression. Electronics Letters 2023,59,doi：10.1049/ell2.12778.] and [Shaoqi,Y.;Bo,T.;Ruizhao,Z. ECCM against Interrupted Sampling Repeater Jamming based on Time-frequency Analysis. JOURNAL OF SIGNAL PROCESSING 2016,32,1244-1251,doi：10.16798/j.issn.1003-0530.2016.10.14.], authors design bandpass filters to suppress interference according to the distribution characteristics of the echo signals in the time-frequency domain. Literature [Pengcheng,W.;Weixiong,B.;Xiaolong,F. Fractional Fourier Transform-based LFM Radars for Countering Interrupted-sampling Repeater Jamming. Fire Control&Command Control 2018,43,35-39.] transforms the echo signal to the fractional domain, nulling the interfering main lobe to suppress the interfering energy. Literature [Jianzhong,Z.;Heqiang,M.;Shuliang,W.;Yanbing,L.;Hongwei,G. Anti-Intermittent Sampling Repeater Jamming Method Based on LFM Segmented Pulse Compression. Journal of Electronics&Information Technology 2019,41,1712-1720,doi：10.11999/JEIT180851.] determines the interfered echo band by means of segmented pulse pressure, and then discards the interfered echo band in the time domain to suppress interference. The method can eliminate interference and influence the integrity of the target signal, so that the target energy is greatly lost. The documents [Zhou,C.;Liu,Q.;Chen,X. Parameter estimation and suppression for DRFM-based interrupted sampling repeater jammer.IET Radar,Sonar&Navigation 2018,12,56-63,doi：10.1049/iet-rsn.2017.0114.]、[Chao,Z.;Quanhua,L.;Cheng,H. Time-frequency analysis techniques for recognition and suppression of interrupted sampling repeater jamming. Journal of Radars 2019,8,100-106,doi：10.12000/JR18080.] and [Lu,L.;Gao,M. An Improved Sliding Matched Filter Method for Interrupted Sampling Repeater Jamming Suppression Based on Jamming Reconstruction. IEEE Sensors Journal 2022,22,9675-9684,doi：10.1109/jsen.2022.3159561.] adopt interference reconstruction and time domain cancellation to inhibit interference, however, the methods need to judge interference patterns, estimate a plurality of parameters such as interference sampling duration, sampling period and the like, and have high requirements on estimation accuracy of the parameters.

Compared with a receiving end signal processing method, the method for combining the transmitting waveform design and the signal processing has the initiative of interference resistance. Literature [Kai,Z.;Feng,H.;Yi,S. Fast algorithm for joint waveform and filter design against interrupted sampling repeater jamming. Journal of Radars 2022,11,264–277,doi：10.12000/JR22015.]、[Zhou,K.;Li,D.;Su,Y.;Liu,T. Joint Design of Transmit Waveform and Mismatch Filter in the Presence of Interrupted Sampling Repeater Jamming. IEEE Signal Processing Letters 2020,27,1610-1614,doi：10.1109/LSP.2020.3021667.] and [Wang,F.;Li,N.;Pang,C.;Li,C.;Li,Y.;Xuesong,W. Complementary Sequences and Receiving Filters Design for Suppressing Interrupted Sampling Repeater Jamming. IEEE Geoscience and Remote Sensing Letters 2022,19,doi：10.1109/LGRS.2022.3156164.] combine the transmit waveform and the receiver filter by suppressing ISRJ with the receiver filter pulse pressure output energy and the target range side lobe, and literature [TAO,Y.;Zhengchun,Z.;Xiaoyong,D.;Qinglong,B.;Yuan,H. An Anti-Interrupted Sampling Repeater Jamming Method Based on Complete Complementary Code Waveform Design. Journal of Electronics&Information Technology 2023,45,3896-3905,doi：10.11999/JEIT230331.] designs a fully complementary code waveform. But such methods involve complex waveform optimization and require prediction of parameters of the disturbance. Literature [Jianzhong,Z.;Huqiang,M.;Shuliang,W.;Yanbing,L. Anti interrupted-sampling repeater jamming method based on stepped LFM waveform. Systems Engineering and Electronics 2019,41,1013-1020,doi：10.3969/j.issn.1001-506X.2019.05.12.] proposes a method for intra-pulse step frequency signal impedance ISRJ, and a target is obtained by extracting and accumulating interference-free signal segments through energy difference after pulse pressure. But when the interference duty is relatively large, the target energy loss is also large. The literature [Siyu,D.;Zhixing,L.;Yaojun,W.;Minghui,S.;Yinghui,Q. Frequency agility waveform combined with time-frequency filter to suppress interrupted-sampling repeater jamming. Systems Engineering and Electronics 2023,45,3819-3827,doi：10.12305/j.issn.1001-506X.2023.12.11.]、[Shuxian,D.;Yaojun,W.;Wen,F.;Yinghui,Q. Anti-interrupted sampling repeater jamming method based on frequency-agile radar joint fuzzy C-means. Journal of Radars 2022,11,289–300,doi：10.12000/JR21205.] and [Zhixing,L.;Siyu,D.;Yaojun,W.;Minghui,S.;Mengdao,X.;Yinghui,Q. Anti-interrupted sampling repeater jamming method for interpulse and intrapulse frequency-agile radar. Journal of Radars 2022,11,301-312,doi：10.12000/JR22001.] propose methods for suppressing ISRJ on the basis of intra-pulse frequency-coded signals, which first classify echo slices by energy differences. The interference is then suppressed in the time, frequency or fractional domain. However, when there are more interference slices, the target in the partial echo slice is highly coupled with the interference, resulting in interference that is difficult to reject. In order to solve the problem, literature [Wang,X.;Li,B.;Liu,W.;Chen,H.;Zhu,Y.;Ni,M. Anti-interrupted Sampling Repeater Jamming Based on Intra-pulse Frequency Modulation Slope Agile Radar Waveform Joint FrFT. Digital Signal Processing 2024,104418,doi：10.1016/j.dsp.2024.104418.] designs a transmission waveform with rapid pulse frequency modulation slope, and energy focusing performance of a chirp signal by using fractional Fourier transform (fractional fourier transform, abbreviated as FrFT) improves the separability of a target and interference in an interfered echo slice, and then interference is effectively restrained by fractional domain filtering. However, the pulse frequency modulation slope agile signal designed by the method has higher distance sidelobes after pulse pressure, and is easy to cause distance blurring during target detection.

In view of this, how to overcome the defects existing in the prior art and solve at least some of the above technical problems is a problem to be solved in the art.

Disclosure of Invention

Aiming at the defects or improvement demands in the prior art, the invention provides an intermittent sampling forwarding interference active countermeasure method, an intermittent sampling forwarding interference active countermeasure device and an intermittent sampling forwarding interference active countermeasure system, and provides a ISRJ suppression method based on intra-pulse frequency coding combined frequency modulation slope agility waveforms. The designed transmitting waveform is composed of a plurality of sub-pulses, the central frequency and the frequency modulation slope are agile in the sub-pulses, and time delay is inserted between adjacent sub-pulses. The method comprises the steps of firstly carrying out time domain primary filtering on echo signals by utilizing time domain discontinuity of transmitted signals, classifying echo slices in a fractional order domain, then constructing a target-interference combined dictionary to reconstruct targets and interference in the interfered echo slices, and finally constructing a time domain narrow-band filter by utilizing non-interference echo slices to further filter echo pulse pressure output after interference suppression so as to reduce distance side lobes caused by residual interference.

The invention adopts the following technical scheme:

in a first aspect, the present invention provides an intermittent sampling forwarding interference active countermeasure method, including:

Designing a transmitting waveform of a transmitting signal, wherein the transmitting waveform comprises a plurality of sub-pulses, the central frequency and the frequency modulation slope of the sub-pulses are adopted to be changed rapidly, and time delay is inserted between adjacent sub-pulses;

dividing an echo signal into a plurality of slices according to the pulse width of a transmitting signal sub-pulse, and setting zero for signals in echo slices at corresponding positions according to the time delay positions inserted between the transmitting signal sub-pulses;

identifying each other echo slice except the zero echo slice, and judging whether the echo slice is an interfered echo slice or a non-interference echo slice;

constructing a sparse matrix of a fractional order domain, and reconstructing a target and interference in the interfered echo slice by using a compressed sensing algorithm;

And constructing a time domain narrow-band filter by using the undisturbed echo slice, further filtering echo pulse pressure output after target reconstruction, and reducing a distance side lobe caused by residual interference.

In a preferred embodiment, the identifying each of the remaining echo slices to determine whether it is an interfered echo slice or a non-interfered echo slice specifically includes:

Traversing the FrFT of the echo slice on fractional order, finding out the transformation order when the output of the FrFT of the echo slice takes the maximum value, and comparing the transformation order with the optimal transformation order of the sub-pulse corresponding to the transmitting signal;

when the error is greater than the decision threshold, the echo slice is determined to be a disturbed echo slice; and when the error is less than or equal to the decision threshold, the echo slice is determined to be a non-interfering echo slice.

In a preferred embodiment, the set of echo slices to be identified is recorded as. Setting the traversing range of fractional orders to be 0-2, and setting the step length to be; Performing order traversal on the FrFT of each echo slice, searching for the corresponding fractional order when the FrFT output of the echo slice reaches the maximum value, and obtaining the optimal order set of the echo slice；

Recording the optimal conversion order set of the transmitting sub-pulses as; The obtained optimal order set of echo slicesAnd (3) withComparing; setting the threshold value as，; When (when)When the echo slice is judged to only contain the target, namely the undisturbed echo slice; when (when)And when the echo slice is interfered, judging that the echo slice is the interfered echo slice.

In a preferred embodiment, the constructing a sparse matrix of fractional order domain, and reconstructing the target and the interference in the interfered echo slice by using a compressed sensing algorithm specifically includes:

Target-interference joint dictionary construction: constructing a sparse matrix by adopting a Pei type discrete FrFT algorithm; the structured target-interference joint dictionary is ; Wherein the sparse matrixes corresponding to the interference and the target are respectivelyAnd；

Observing the disturbed echo slices: constructing an observation matrixAnd (2) andIs a Gaussian random matrix which is independently and uniformly distributed; the observed signal vector obtained by measuring the ith echo slice is; In the method, in the process of the invention,For the target-interference joint sparse vector,As a result of the sparse vector of the target,Is an interference sparse vector; In the event of a noise occurrence, An observation vector that is noise;

The solution of (2) is as follows: ; wherein, Is a constant related to noise;

The target signal in the reconstructed ith slice is: 。

In a preferred embodiment, the target and the interference in each disturbed echo slice are reconstructed, and finally the echo signal after the reconstruction of the target is obtained.

In a preferred embodiment, the constructing a time-domain narrow-band filter by using the undisturbed echo slice, and the further filtering the echo pulse pressure output after the target reconstruction specifically includes:

Convolving the non-interfering echo slices with the transmit signal, thereby constructing a normalized time-domain filter;

Convolving the echo signal after target reconstruction with the transmitting signal to obtain pulse pressure output of the echo signal after target reconstruction;

and the pulse pressure output of the echo signal after target reconstruction is further subjected to a normalized time domain filter to obtain the final pulse pressure output after time domain filtering.

In a preferred embodiment, the transmit waveform comprises an intra-pulse frequency encoded joint chirp rate agile waveform; wherein:

assume that the pulse width of the radar transmit signal is The sub pulse width isThe time delay length of adjacent sub-pulse insertion is; The number of sub-pulses included in the transmit pulse is，Representation rounding; the bandwidth range of the sub-pulse is [ B _min,B_max ]; the bandwidth of the nth sub-pulse is，Is the minimum interval of the sub-pulse bandwidth; encodes a sequence for sub-pulse bandwidth, an In the time-course of which the first and second contact surfaces,; The adjacent sub-pulses adopt positive and negative modulation slopes, and the modulation slope of the nth sub-pulse is; The center frequency of the nth sub-pulse is，Representing the initial carrier frequency of the radar transmit pulse,For the minimum interval of sub-pulse carrier frequencies,Maximum interval of sub-pulse carrier frequency; encodes a sequence for a sub-pulse frequency, an In the time-course of which the first and second contact surfaces,；

The intra-pulse frequency coding joint frequency modulation slope agility signal transmitted by the radar is:

；

In the method, in the process of the invention, For the nth sub-pulse of the transmit pulse,；

Is a rectangular window function.

In a second aspect, the present invention further provides an intermittent sampling forwarding interference active countermeasure device, configured to implement the intermittent sampling forwarding interference active countermeasure method in the first aspect, where the device includes:

at least one processor; and a memory communicatively coupled to the at least one processor; wherein the memory stores instructions executable by the at least one processor for performing the intermittent sample forwarding interference initiative countermeasure method of the first aspect.

In a third aspect, the present invention further provides an intermittent sampling forwarding interference active countermeasure system, applying the intermittent sampling forwarding interference active countermeasure method according to the first aspect, where the system includes a transmit waveform design module, a slice division module, a slice identification module, a reconstruction module, and a filtering module; wherein:

The transmitting waveform design module is used for designing a transmitting waveform of a transmitting signal, the transmitting waveform comprises a plurality of sub-pulses, center frequency and frequency modulation slope are adopted in the sub-pulses, and time delay is inserted between adjacent sub-pulses;

The slice dividing module is used for dividing the echo signals into a plurality of slices according to the pulse width of the transmitting signals, and setting the signals in the echo slices at the corresponding positions to zero according to the time delay positions inserted among the transmitting signal sub-pulses;

The slice identification module is used for identifying each echo slice except the zero echo slice and judging whether the echo slice is an interfered echo slice or a non-interference echo slice;

The reconstruction module is used for constructing a sparse matrix of a fractional order domain and reconstructing a target and interference in the interfered echo slice by using a compressed sensing algorithm;

The filtering module is used for constructing a time domain narrow-band filter by utilizing the undisturbed echo slice, further filtering the echo pulse pressure output after target reconstruction, and reducing a distance side lobe caused by residual interference.

In a fourth aspect, the present invention also provides a non-volatile computer storage medium storing computer executable instructions for execution by one or more processors to perform the intermittent sample forwarding interference initiative countermeasure method of the first aspect.

Compared with the prior art, the invention has the beneficial effects that:

(1) A novel intra-pulse frequency-coding joint frequency modulation slope agility waveform is designed. The correlation between the sub-pulses is reduced by adopting double-parameter agility in the sub-pulses. The time delay is inserted between adjacent sub-pulses, and engineering requirements of parameter updating and logic resetting during waveform generation are considered. The fuzzy function graph of the transmit waveform approximates an ideal thumbtack type.

(2) The method makes full use of echo data. The target and interference in the interfered echo slice are reconstructed by compressed sensing, the target energy loss is reduced, the distance sidelobe in echo pulse pressure output is further suppressed by using the time domain narrow band filter constructed by the undisturbed echo slice, and the anti-interference performance under high JSR is improved.

(3) The method has good inhibition effect on ISRJ formed by synchronous sampling and asynchronous sampling of the jammer on an application scene.

Drawings

In order to more clearly illustrate the technical solution of the embodiments of the present invention, the drawings that are required to be used in the embodiments of the present invention will be briefly described below. It is evident that the drawings described below are only some embodiments of the present invention and that other drawings may be obtained from these drawings without inventive effort for a person of ordinary skill in the art.

Fig. 1 is a flowchart of an intermittent sampling forwarding interference active countermeasure method provided in embodiment 1 of the present invention;

FIG. 2 is a time-frequency diagram of the intra-pulse frequency coding joint frequency modulation slope agility waveform according to embodiment 2 of the present invention;

fig. 3 is a schematic diagram illustrating a process of generating ISRJ by an jammer according to embodiment 2 of the present invention;

fig. 4 is a schematic diagram of a matched filter output of a transmit waveform according to embodiment 3 of the present invention;

FIG. 5 is a fuzzy function diagram of the frequency-coded joint frequency modulation slope agile signal in accordance with embodiment 3 of the present invention;

Fig. 6 is a flowchart of an interference countermeasure method according to embodiment 4 of the present invention;

FIG. 7 is a schematic diagram of ISDRJ inhibition results provided in example 5 of the present invention;

FIG. 8 is a schematic diagram of ISPRJ inhibition results provided in example 5 of the present invention;

FIG. 9 is a schematic diagram of ISCRJ inhibition results provided in example 5 of the present invention;

Fig. 10 is a schematic diagram of classification accuracy of an interfered echo slice under different SNR and JSR according to the SOOC and TDB methods provided in embodiment 5 of the present invention;

fig. 11 is a schematic diagram of an echo signal TDP of ISDRJ interference after interference suppression provided in embodiment 5 of the present invention;

fig. 12 is a schematic diagram of an echo signal TDP of ISPRJ interference after interference suppression provided in embodiment 5 of the present invention;

fig. 13 is a schematic diagram of an echo signal TDP of ISCRJ interference after interference suppression provided in embodiment 5 of the present invention;

FIG. 14 is a schematic diagram showing ISDRJ inhibition results provided in example 5 of the present invention;

FIG. 15 is a schematic diagram showing ISPRJ inhibition results provided in example 5 of the present invention;

FIG. 16 is a schematic diagram showing ISCRJ inhibition results provided in example 5 of the present invention;

FIG. 17 is a diagram showing the relationship between the normalized amplitude of the post-interference suppression target and the sampling delay of the jammer according to embodiment 5 of the present invention;

Fig. 18 is a schematic block diagram of an intermittent sampling forwarding interference active countermeasure system according to embodiment 6 of the present invention;

fig. 19 is a schematic structural diagram of an active countermeasure device for intermittent sampling forwarding interference according to embodiment 6 of the present invention.

Detailed Description

The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the present invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications could be made by those skilled in the art without departing from the inventive concept. These are all within the scope of the present invention.

The present application will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present application more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the application.

It should be noted that, if not in conflict, the features of the embodiments of the present application may be combined with each other, which is within the protection scope of the present application. In addition, while functional block division is performed in a device diagram and logical order is shown in a flowchart, in some cases, the steps shown or described may be performed differently than block division in a device, or order in a flowchart.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In addition, the technical features of the embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.

Intermittent sample-and-forward Interference (ISRJ) is widely applied to the field of electronic countermeasure, and the generated false target has both deceptive and suppressing properties, so that the radar has a great challenge. ISRJ antagonism is one of the challenges in current radar anti-interference. The embodiment of the invention provides ISRJ countermeasure technology based on intra-pulse frequency coding combined frequency modulation slope agility waveforms. By transmitting the time delay inserted between the sub-pulses and the central frequency and the frequency modulation slope in the sub-pulses, the designed signal is convenient for engineering realization, and the fuzzy function diagram of the signal approximates to an ideal thumbtack type. Using ISRJ time domain discontinuities and FrFT focusing on the chirp signal we classify the echo slices in the fractional order domain. And then reconstructing a target and interference in the interfered echo slice through compressed sensing to inhibit interference, and finally constructing a time domain filter by utilizing the non-interference echo slice to reduce a distance side lobe caused by residual interference after interference inhibition. Simulation results show that the method can effectively resist three typical ISRJ interferences. When the interference signal ratio (JSR) =50 dB, the target detection probability after interference suppression is 90% or more.

The invention will be described in detail below with reference to the drawings and examples.

Example 1:

As shown in fig. 1, an embodiment of the present invention provides an intermittent sampling forwarding interference active countermeasure method, which includes the following steps.

Step 100: and designing a transmitting waveform of a transmitting signal, wherein the transmitting waveform comprises a plurality of sub-pulses, the central frequency and the frequency modulation slope of the sub-pulses are adopted to be changed rapidly, and time delay is inserted between adjacent sub-pulses. The transmitted waveform in this step is a novel intra-pulse frequency-coded joint frequency modulation slope agility waveform designed in accordance with embodiments of the present invention.

Step 200: dividing the echo signal into a plurality of slices according to the pulse width of the transmitting signal, and setting the signal in the echo slice at the corresponding position according to the time delay position inserted between the transmitting signal sub-pulses.

Step 300: and identifying each other echo slice except the zero echo slices, and judging whether the echo slices are the interfered echo slices or the undisturbed echo slices. Specifically, the FrFT of the echo slice may be traversed in fractional order, the transformation order when the output of the FrFT of the echo slice takes the maximum value is found, and then compared with the optimal transformation order of the sub-pulse corresponding to the transmission signal; when the error is greater than the decision threshold, the echo slice is determined to be a disturbed echo slice; and when the error is less than or equal to the decision threshold, the echo slice is determined to be a non-interfering echo slice.

Step 400: constructing a sparse matrix of a fractional order domain, and reconstructing a target and interference in the interfered echo slice by using a compressed sensing algorithm.

Step 500: and constructing a time domain narrow-band filter by using the undisturbed echo slice, further filtering echo pulse pressure output after target reconstruction, and reducing a distance side lobe caused by residual interference.

In a preferred embodiment, the steps 300 are expandable to: recording the set of echo slices to be identified as. Setting the traversing range of fractional orders to be 0-2, and setting the step length to be; Performing order traversal on the FrFT of each echo slice, searching for the corresponding fractional order when the FrFT output of the echo slice reaches the maximum value, and obtaining the optimal order set of the echo slice; Recording the optimal conversion order set of the transmitting sub-pulses as; The obtained optimal order set of echo slicesAnd (3) withComparing; setting the threshold value as，; When (when)When the echo slice is judged to only contain the target, namely the undisturbed echo slice; when (when)And when the echo slice is interfered, judging that the echo slice is the interfered echo slice.

In a preferred embodiment, the steps 400 are expandable to: constructing a target-interference joint dictionary, and constructing a sparse matrix by adopting a Pei type discrete FrFT algorithm; the structured target-interference joint dictionary is; Wherein the sparse matrixes corresponding to the interference and the target are respectivelyAnd; Observing the disturbed echo slices: constructing an observation matrixAnd (2) andIs a Gaussian random matrix which is independently and uniformly distributed; the observed signal vector obtained by measuring the ith echo slice is; In the method, in the process of the invention,For the target-interference joint sparse vector,As a result of the sparse vector of the target,Is an interference sparse vector; In the event of a noise occurrence, An observation vector that is noise; The solution of (2) is as follows: ; wherein, Is a constant related to noise; the target signal in the reconstructed ith slice is: . And then reconstructing the target and the interference in each interfered echo slice, and finally obtaining the echo signal after target reconstruction.

In a preferred embodiment, for step 500, it is scalable to: convolving the non-interfering echo slices with the transmit signal, thereby constructing a normalized time-domain filter; convolving the echo signal after target reconstruction with the transmitting signal to obtain pulse pressure output of the echo signal after target reconstruction; and the pulse pressure output of the echo signal after target reconstruction is further subjected to a normalized time domain filter to obtain the final pulse pressure output after time domain filtering.

In summary, the embodiments of the present invention provide an intermittent sampling forwarding interference active countermeasure method, which includes the following advantages: (1) A novel intra-pulse frequency-coding joint frequency modulation slope agility waveform is designed. The correlation between the sub-pulses is reduced by adopting double-parameter agility in the sub-pulses. The time delay is inserted between adjacent sub-pulses, and engineering requirements of parameter updating and logic resetting during waveform generation are considered. The fuzzy function graph of the transmit waveform approximates an ideal thumbtack type. The method (2) makes full use of echo data. The target and interference in the interfered echo slice are reconstructed by compressed sensing, the target energy loss is reduced, the distance sidelobe in echo pulse pressure output is further suppressed by using the time domain narrow band filter constructed by the undisturbed echo slice, and the anti-interference performance under high JSR is improved. (3) The method has good inhibition effect on ISRJ formed by synchronous sampling and asynchronous sampling of the jammer on an application scene.

Example 2:

On the basis of the intermittent sampling forwarding interference active countermeasure method provided in the above embodiment 1, embodiment 2 of the present invention describes in detail a signal model adopted.

(1) The intra-pulse frequency coding combines a frequency modulation slope agility waveform.

The time-frequency diagram of the intra-pulse frequency coding combined frequency modulation slope agility waveform designed by the embodiment of the invention is shown in fig. 2.

As can be seen from fig. 2, the radar transmit pulse is made up of a plurality of sub-pulses. The pulse widths of the sub-pulses are the same and are all linear frequency modulated, except that each sub-pulse has a different center frequency and bandwidth. In addition, the frequency modulation slope polarities of adjacent sub-pulses are alternately changed according to positive and negative, and time delay is inserted between the adjacent sub-pulses in consideration of the mutual shielding of the sub-pulses and the actual engineering requirements.

Assume that the pulse width of the radar transmit signal isThe sub pulse width isThe time delay length of adjacent sub-pulse insertion is; The number of sub-pulses included in the transmit pulse is，Representation rounding; the bandwidth range of the sub-pulse is [ B _min,B_max ]; the bandwidth of the nth sub-pulse is，Is the minimum interval of the sub-pulse bandwidth; encodes a sequence for sub-pulse bandwidth, an In the time-course of which the first and second contact surfaces,; The adjacent sub-pulses adopt positive and negative modulation slopes, and the modulation slope of the nth sub-pulse is; The center frequency of the nth sub-pulse is，Representing the initial carrier frequency of the radar transmit pulse,For the minimum interval of sub-pulse carrier frequencies,Maximum interval of sub-pulse carrier frequency; the value of (2) should be larger in order to reduce the correlation of adjacent pulses; encodes a sequence for a sub-pulse frequency, an In the time-course of which the first and second contact surfaces,。

The intra-pulse frequency coding joint frequency modulation slope agility signal transmitted by the radar is:

(1)

In the method, in the process of the invention, For the nth sub-pulse of the transmit pulse,；

Is a rectangular window function.

(2) ISRJ model.

ISRJ can be classified into three types according to the number of forwarding times and forwarding modes: intermittent sample direct forwarding interference (interupted SAMPLING DIRECT REPEATER Jamming, abbreviated: ISDRJ), intermittent sample repeat forwarding interference (Interrupted Sampling Periodic Repeater Jamming, abbreviated: ISPRJ), and intermittent sample cyclic forwarding interference (interupted SAMPLING CYCLIC REPEATER Jamming, abbreviated: ISCRJ). The process of jammer generation ISRJ is shown in fig. 3. As can be seen from fig. 3, the jammer forwards the sampled partial pulse once to form ISDRJ and the sampled partial pulse multiple times to form ISPRJ. ISCRJ are formed by the jammer forwarding the current and past stored pulses.

Sampling pulse string with jammerIs a series of bursts with a rectangular envelope, defined as follows:

(2)

In the method, in the process of the invention, Is the sampling time delay of the jammer,Is the pulse width of the sampling pulse,Is the repetition period of the sampling pulse,Is the number of the sampling pulses which are to be counted,Representing a convolution.

Intermittent sampling of the radar transmit signal by the jammer is equivalent to the product of the radar transmit signal and the sampling pulse train, so the intermittently sampled signal can be expressed as:

(3)

And the jammer obtains three typical ISRJ as follows by controlling time delay, forwarding times and forwarding modes:

(4)

(5)

(6)

Wherein, ，AndISDRJ, ISPRJ and ISCRJ are shown, respectively.Representing the magnitude of the disturbance,Number of repeated forwarding of ISPRJ, and。Number of repeated forwarding of ISCRJ, and。The representation takes the minimum value of the value,Representing a rounding down.

(3) Echo signal model.

Assume that a point target exists in a radar observation scene, and the distance between the point target and the radar isCorresponding time delay isThe target echo signal is:

(7)

Wherein, Representing the magnitude of the target.

Will transmit a signalSubstituting into formulas (4) - (6), specific expressions of ISDRJ, ISPRJ and ISCRJ can be obtained. For convenience of presentation, the different ISRJ are unifiedRepresenting, then the jammer generated ISRJ received by the radar may be represented as。

The radar-received echo signal may be expressed as

(8)

Wherein,Representing gaussian white noise.

Example 3:

On the basis of the intermittent sampling forwarding interference active countermeasure method provided in the above embodiment, embodiment 3 of the present invention expands the analysis on the necessity of intra-pulse frequency coding combined frequency modulation slope agility.

And (3) analyzing the characteristics of the double-parameter agile waveform:

The frequency modulation slope agility signal in the pulse designed in literature [Wang,X.;Li,B.;Liu,W.;Chen,H.;Zhu,Y.;Ni,M. Anti-interrupted Sampling Repeater Jamming Based on Intra-pulse Frequency Modulation Slope Agile Radar Waveform Joint FrFT. Digital Signal Processing 2024,104418,doi：10.1016/j.dsp.2024.104418.] enables targets and interferences in the same time period to be different in frequency modulation slope through agility of frequency modulation slope agility of pulse sub-pulses, and then the characteristics of separating chirp signals with different frequency modulation slopes by utilizing FrFT can be utilized to filter the interferences in fractional order domain, so that a good inhibition effect is achieved. However, from a waveform design perspective, there are two drawbacks to the intra-pulse single parameter (chirp rate) agile signal. Firstly, the correlation of adjacent sub-pulses is strong, the matching output of the intra-pulse frequency modulation slope agile signal has a side lobe with higher amplitude, the distance is easy to blur, and the target detection is not facilitated. Secondly, the instantaneous change in magnitude and polarity of adjacent sub-pulses' chirp rate is difficult to achieve in engineering because direct digital frequency synthesis (DIRECT DIGITAL Frequency Synthesis, abbreviated as DDS) requires time for logic reset and parameter update when forming different waveforms. Based on this, this embodiment designs a transmission waveform with intra-pulse frequency coding and joint frequency modulation slope agility. The problem of difficult engineering realization is solved by inserting time delay between adjacent sub-pulses, and the sidelobes of the transmitted signal after pulse pressure are reduced by double parameters (center frequency and frequency modulation slope) of the sub-pulses. The characteristics of the dual-parameter agile waveform of this embodiment are analyzed from the matched filter output and the fuzzy function diagram of the transmit waveform, respectively.

The parameters of the following simulation experiments were set as follows:μs， Mu s, the bandwidth range of the sub-pulse is 2-10 MHz, ，The sampling frequency is 20 MHz. The sub-pulse bandwidth coding sequence a= [10,7,2,1,9,5,6,8,3,4]. The sub-pulse frequency coding sequence b= [4,9,1,8,2,7,3,6,5, 10].

Fig. 4 (a) simulates the time-frequency distribution of an intra-pulse frequency-coding joint chirp-agile signal, and fig. 4 (b) simulates the time-frequency distribution of an intra-pulse frequency-coding joint chirp-agile signal. As can be seen from the figure, the signal designed by the embodiment enhances the discrimination between the sub-pulses through the agility of the center frequency and the frequency modulation slope of the sub-pulses, and improves the mutual shielding capability of the sub-pulses. Fig. 4 (c) simulates the matched filtered output of two transmit signals. In contrast, the dual-parameter agile signal designed in this embodiment has lower side lobes than the intra-pulse frequency modulation slope agile signal, and is more favorable for detecting the target after signal processing.

Fig. 5 simulates a fuzzy function diagram of the designed signal. Wherein (a) in fig. 5 is a blur function diagram; fig. 5 (b) is a contour diagram of a blur function; fig. 5 (c) is a distance blur function diagram; fig. 5 (d) is a velocity blur function chart. From fig. 5 (a), fig. 5 (b) shows that the blur function diagram of the intra-pulse frequency coding joint chirp rate agility signal is approximately "pin-type". In fig. 5 (c), in fig. 5 (d), the zero doppler slice and the zero delay slice of the blur function are narrow at the main cusp at the origin, indicating that the designed signal has a higher distance and velocity resolution.

Example 4:

based on the intermittent sampling forwarding interference active countermeasure method provided in the above embodiment, the suppression method of ISRJ is further described in embodiment 4 of the present invention from two aspects of interference echo segment identification and interference suppression.

Referring to fig. 6, it can be summarized as: echo signals; echo slice segmentation; preliminary time domain filtering; fractional order searching and comparison; constructing an undisturbed echo slice extraction/target interference joint dictionary; target and interference reconstruction; time domain filtering; echo signals after interference suppression.

(1) FrFT-based disturbed echo slice identification.

FrFT is a generalized Fourier transform with good focusing on chirp signals. The principle of identification of the disturbed echo slices is explained below from the point of view of energy focusing.

Assuming chirp signalsWherein, the method comprises the steps of, wherein,In the form of a pulse width,Is the frequency modulation slope.The fractional fourier transform of (a) is:

(9)

Wherein, To change angle and，For the transform order.As a transformation kernel function, the expression is:

(10)

When (when) At this timeIs the optimal transformation angle and is noted as. Optimal transformation angleThe corresponding order is called the optimal transform order. Optimal transformation angleThe expression of (2) is:

(11)

At the position of The following formula (9) may be further expressed as:

(12)

In general Much greater than 1, so that the approximate relationship of formula (11) can be obtained: And . Substituting it into formula (12) to obtain:

(13)

From equation (13), the chirp signal is expressed in The lower FrFT output envelope is a sine function, and the energy of the FrFT output envelope is mainly concentrated on the main lobe of the sine function, so that the good energy focusing property of the FrFT on the chirp signal is reflected.

In the radar transmit waveform of this embodiment, ISRJ in the disturbed return band and the target have different chirp rates due to the time domain discontinuity of ISRJ. Assuming that the interference and target chirp rates are respectivelyAndThen at the corresponding optimal transformation angleAndThe interference and target FrFT are respectively:

(14)

(15)

In the method, in the process of the invention, AndThe bandwidths of the target and the interference respectively,Is the length of the disturbed echo band.

Since the interference energy is typically much larger than the target, in the interfered echo band, the corresponding order when the FrFT output of the echo signal takes maximum value is the optimal transformed order of the interference due to the energy suppression of the interference. When the echo slice contains only the target, the FrFT output of the slice takes a maximum value at the optimal transformation order of the target. According to the characteristic, the FrFT of the echo slice can be traversed on fractional order, the transformation order when the output of the FrFT of the echo slice reaches the maximum value is found, and then the transformation order is compared with the optimal transformation order of the corresponding sub-pulse of the transmitting signal. When the error is greater than the decision threshold, the echo slice is determined to be a disturbed echo slice, and when the error is less than or equal to the decision threshold, the echo slice is determined to be a non-disturbed echo slice.

(2) Interference suppression based on signal reconstruction in combination with time domain filtering.

The designed radar emission waveform is discontinuous in time domain, and the inserted time delay can be used as an interference trap. Since the target and the fractional domain of the interference in the disturbed echo slice exhibit an approximate sparsity at the respective optimal transformation orders, the interference and the target can be reconstructed in the fractional domain by compressed sensing. In addition, the undisturbed echo slice can be extracted to construct a time domain dimension filter, and the echo pulse pressure output after target reconstruction is further subjected to time domain filtering, so that the range side lobe is reduced. In summary, the present embodiment proposes an interference suppression method based on signal reconstruction and time domain filtering. For ease of analysis, the present embodiment only considers the inserted delay lengthEqual to the sub-pulse widthIs the case in (a). The method comprises the following specific steps.

Step 1: and (5) performing time domain preliminary filtering. Echo signal to transmit signal sub-pulse widthDividing the echo signals into a plurality of slices, and setting the zero of the signals in the echo slices at the corresponding positions according to the time delay positions inserted between the sub-pulses of the transmission signals.

Step 2: and identifying each other echo slice except the zero echo slices, and judging whether the echo slices are the interfered echo slices or the undisturbed echo slices. The specific steps are as follows.

Step 2.1: the set of echo slices to be identified is. Setting the traversing range of fractional orders to be 0-2, and setting the step length to be. Performing order traversal on the FrFT of each echo slice, and searching for a corresponding fractional order when the FrFT output of the echo slice reaches the maximum value. The pseudo code of the specific algorithm is as follows:

Algorithm 1：Fractional Order Search；

Input： echo slice set，number of slices，upper and lower bounds for order traversal D；

step size；

Output： optimal fractional order set of echo slices；

Initialize：；；

1：for (i =1 to) do；

2：for (p = 0 to 2 with step size) do；

3：Compute the FrFT ofat order p according to Eq. (9)；

4：end for；

5：Search for the maximum value of the FrFT ofin the traversal range；

6：；//is the FrFT operator at order p；

7：end for；

8：return。

Step 2.2: the fractional order optimal transformation order corresponding to the sub-pulses of the radar transmit signal is known as a priori information, noting that the set of optimal transformation orders of the transmit sub-pulses is . The optimal order set of echo slices obtained in the step 2.1 is obtainedAnd (3) withComparison was performed. Setting the threshold value as，. When (when)When the echo slice is judged to contain only the targetWhen the echo slice is disturbed, the echo slice is judged.

Step 3: and (5) reconstructing a signal. After step 2, we can know the optimal transformation order of the interference and target in the interfered echo slice. According to the energy focusing property of the FrFT on the chirp signal, the fractional order domains of the target and the interference signal under the respective optimal transformation orders are approximately sparse, so that a sparse matrix of the fractional order domains can be constructed, and the target and the interference can be reconstructed by using a compressed sensing algorithm (Compressed Sensing, abbreviated as CS). The specific steps are as follows.

Step 3.1: target-interference joint dictionary construction. Here, a sparse matrix is constructed using the Pei-type discrete FrFT algorithm. By chirp signalsFor example, a sparse matrix construction. For a pair ofThe time domain signal and the fractional order domain signal are sampled, and the sampling intervals are respectively set asAndThe obtained sampling signals are respectivelyAndWherein，，AndAre integers.AndThe number of sampling points is the time domain and the fractional order domain respectively.

The discrete FrFT matrix corresponding to equation (9) can be expressed as:

(16)

(17)

(18)

Wherein, Is thatThe elements of the order discrete FrFT matrix are as follows:

(19)

In the method, in the process of the invention, Is associated withAre integers of prime numbers to each other.

Order theFor the followingFormula (19) may be further written as:

(20)

the embodiment adopts an orthogonal base dictionary, namely, a command Thereby can obtainThe base dictionary of the fractional order domain under the order is:

(21)

Let i-th echo slice be the disturbed echo slice. From step 2, the optimal transformation order of the interference in the ith echo slice is The optimal transformation order of the target is. So that the sparse matrix corresponding to the interference and the target are respectivelyAnd. The target-interference joint dictionary is thus constructed as:

(22)。

Step 3.2: the disturbed echo slices are observed. Constructing an observation matrix of dimension Q× (2W+1) (where Q is much smaller than 2W+1) And (2) andIs a Gaussian random matrix which is independently and uniformly distributed. The observed signal vector obtained by measuring the ith echo slice is:

(23)

In the method, in the process of the invention, A joint sparse vector for target-interference;

As a result of the sparse vector of the target, Is an interference sparse vector.In the event of a noise occurrence,Is an observation vector of noise.

Step 3.3: the solution of (c) can be converted into the following The problem of norm optimisation, i.e

(24)

Wherein,Is a constant related to noise.

The target signal in the reconstructed ith slice is

(25)。

Step 4: the target and the disturbance in each disturbed echo slice are reconstructed. Finally obtaining the echo signal after target reconstruction。

Step 5: and (5) time domain filtering. Extracting and marking the undisturbed echo slices identified in the step 2 as. Will beConvolving with the transmit signal, thereby constructing a normalized time domain filter as:

(26)

Will be Convolving the target reconstructed echo signal with the emission signal to obtain pulse pressure output of the target reconstructed echo signal, namely:

(27)

Will be Further pass throughObtaining the final pulse pressure output after time domain filtering：

(28)。

Example 5:

On the basis of the intermittent sampling forwarding interference active countermeasure method provided in the above embodiment, embodiment 5 of the present invention describes a simulation result, and mainly includes an interference suppression effect and an algorithm performance analysis.

The validity of the method is verified through simulation experiments. It should be noted that the pulse width of the pwm signal is equal to or smaller than the sampling pulse width of the jammer in order to exert the active anti-jamming advantage. The embodiment assumes that the radar has acquired the interference parameter during the environmental awareness process, and the generated sub-pulse width is less than or equal to the jammer sampling pulse width. Meanwhile, in order to facilitate analysis, only the condition that the two are equal is considered in the simulation experiment. The radar transmit waveforms and interference related parameters in the simulation are shown in table 1.

Table 1 parameter settings for simulation experiments

(1) Interference suppression effect.

Assume that an jammer synchronously samples a radar transmission signal, i.e. sampling delay. The interference suppression results for the three exemplary ISRJ are shown in fig. 7, 8, and 9, respectively.

In fig. 7, fig. 7 (a) is a time-frequency diagram of an echo signal interfered by ISDRJ; fig. 7 (b) is a time-frequency diagram of the echo signal after target reconstruction; fig. 7 (c) shows pulse pressure results before and after the proposed method is anti-interference; fig. 7 (d) shows a comparison of pulse pressure results of different interference suppression methods, and in fig. 7 (d), the line corresponding to fractional domain filtering is overlapped with the line corresponding to time domain discarding, and is covered, so that the line is not shown; the pulse pressure output filtering is overlapped with the corresponding line of the method and covered, so the pulse pressure output filtering is not shown. In fig. 8, fig. 8 (a) is a time-frequency diagram of an echo signal interfered by ISPRJ; fig. 8 (b) is a time-frequency diagram of the echo signal after target reconstruction; fig. 8 (c) shows pulse pressure results before and after the proposed method is anti-interference; fig. 8 (d) is a comparison of pulse pressure results for different interference suppression methods. In fig. 9, fig. 9 (a) is a time-frequency diagram of an echo signal interfered by ISCRJ; fig. 9 (b) is a time-frequency diagram of the echo signal after target reconstruction; fig. 9 (c) shows pulse pressure results before and after the proposed method is anti-interference; fig. 9 (d) is a comparison of pulse pressure results for different interference suppression methods; in fig. 9 (d), the line corresponding to the fractional domain filtering coincides with the line corresponding to the time domain discarding, and is covered, so it is not shown; the pulse pressure output filtering is covered by most of the coincidence of the line corresponding to the method.

Fig. 7 (a), fig. 8 (a) and fig. 9 (a) are time-frequency diagrams when the transmission signal designed in this embodiment is subjected to three types ISRJ, respectively. It can be seen that the time-lapse slice inserted between transmit sub-pulses has two effects in combating interference. Firstly, when the jammer intermittently samples, the transmitting sub-pulse is shielded, so that the jammer cannot sample all the sub-pulses. And secondly, when the jammer intermittently forwards, part of interference falls into a time delay slice and cannot interfere with a target signal. In fig. 7 (a) and fig. 9 (a), the interference in the echo signal falls in the time delay slice, so that the interference can be completely suppressed by setting the time delay slice to zero during the time domain preliminary filtering, and no energy loss is caused. In fig. 8 (a), some of the sub-pulses of the echo signal disturbed by ISPRJ are disturbed, so that further interference suppression is required after the time-domain preliminary filtering. Fig. 7 (b), fig. 8 (b) and fig. 9 (b) are time-frequency diagrams of echo signals after target reconstruction, wherein the targets in fig. 7 (b) and fig. 9 (b) are lossless targets. The reconstructed object can be found by comparing the object in the partial slice in fig. 8 (b), and the object signal can be effectively reconstructed in the fractional domain by compressed sensing. Then, pulse pressure output comparison results of the anti-interference pre-and post-echo signals are obtained through matched filtering and further time domain filtering, and are shown in (c) of fig. 7, (c) of fig. 8 and (c) of fig. 9, so that three typical ISRJ can be effectively restrained by the method in the embodiment. fig. 7 (d), fig. 8 (d), and fig. 9 (d) are comparison results of pulse pressure post-filtering, fractional domain interference suppression, interference slice rejection, and echo pulse pressure output after three ISRJ suppression by the proposed method, respectively, under the transmission signal designed in this embodiment. For echo signals interfered by ISDRJ and ISCRJ, the interference falls on the time delay slice, so that after the pulse pressures of different processing methods are subjected to time domain preliminary filtering, no target energy loss exists, but the method of the document [Siyu,D.;Zhixing,L.;Yaojun,W.;Minghui,S.;Yinghui,Q. Frequency agility waveform combined with time-frequency filter to suppress interrupted-sampling repeater jamming. Systems Engineering and Electronics 2023,45,3819-3827,doi：10.12305/j.issn.1001-506X.2023.12.11.] and the method of the embodiment have lower range side lobes. When the echo signal is ISPRJ, part of the sub-pulses are interfered, and at the moment, the identified interfered echo slices are removed by the method of literature [Jianzhong,Z.;Heqiang,M.;Shuliang,W.;Yanbing,L.;Hongwei,G. Anti-Intermittent Sampling Repeater Jamming Method Based on LFM Segmented Pulse Compression. Journal of Electronics&Information Technology 2019,41,1712-1720,doi：10.11999/JEIT180851.], so that larger target energy loss is caused. Literature [Siyu,D.;Zhixing,L.;Yaojun,W.;Minghui,S.;Yinghui,Q. Frequency agility waveform combined with time-frequency filter to suppress interrupted-sampling repeater jamming. Systems Engineering and Electronics 2023,45,3819-3827,doi：10.12305/j.issn.1001-506X.2023.12.11.] extracts a time domain filter with a non-interference section structure through time-frequency analysis to directly filter echo pulse pressure output, so that signal energy in a target distance unit is reserved, but for strong false targets in other distance units, a small peak can be formed after suppression, and radar detection is affected. Literature [Pengcheng,W.;Weixiong,B.;Xiaolong,F. Fractional Fourier Transform-based LFM Radars for Countering Interrupted-sampling Repeater Jamming. Fire Control&Command Control 2018,43,35-39.] suppresses the interference spectrum peaks in the fractional domain, but while most of the interference signals are suppressed, the remaining interference results in higher range sidelobes. In contrast, the method provided by the embodiment reserves the target and suppresses interference through fractional domain signal reconstruction, and in addition, the method utilizes the identified undisturbed echo slice information to construct a time domain filter to further filter the pulse pressure output after target reconstruction, so that distance side lobes are reduced. In combination, the method according to the embodiment is more advantageous.

(2) Method performance analysis.

In this embodiment, the signal recovery in the disturbed echo slice and the construction of the time filter are both dependent on the exact classification of the echo slice. Therefore, the present embodiment adopts the classification accuracy (Classification Accuracy, abbreviated as CA) of the interfered echo slices as an evaluation criterion. CA is the average ratio of the correctly classified disturbed echo slices and is expressed as follows:

；

Wherein, Representing the number of monte carlo experiments,Representing the actual number of disturbed echo slices,Representing a measure of the classification of the j-th disturbed echo slice in the i-th monte carlo experiment. When the jth disturbed return band is correctly identified,And the value of (2) is 1, otherwise 0.

In order to explore the classification accuracy of the method on the interfered echo slices, the SNR variation range is set to be-10 dB, the JSR values are respectively 5 dB, 10 dB, 15 dB and 20 dB, and the Monte Carlo experiment number is 200. The accuracy of classification of the disturbed echo band by the slice order optimizing and comparing method (Slice Order Optimizing and Comparison, abbreviated as SOOC) and the Time-domain Blanking method (TDB) is shown in FIG. 10. Fig. 10 is a graph of accuracy of classification of disturbed echo slices at different SNR and JSR for the SOOC and TDB methods. Wherein (a) in fig. 10 is an echo disturbed by ISDRJ; fig. 10 (b) shows an echo disturbed by ISPRJ; fig. 10 (c) shows an echo disturbed by ISCRJ.

The TDB method classifies echo slices by the difference of energy of the interfered echo plate and the undisturbed echo slices in the time domain, and has good classification performance under higher JSR. However, when SNR and JSR are low, the main component in the echo is noise. The amplitude of the noise now covers the target and the disturbance, which makes it difficult for the TDB method to accurately classify the echo slices. In contrast, the proposed SOOC method exploits the energy focusing of the chirp signal by FrFT to improve the classification ability of echo slices at low SNR. As shown in fig. 10, under the same SNR and JSR conditions. The classification accuracy of the SOOC method on the interfered echo slices is higher than that of the TDB method, and the classification accuracy under the condition of low SNR is higher than 90%, so that the SOOC method has strong anti-noise performance.

The target detection probability (target detection probability, abbreviated as TDP) is adopted as a performance evaluation standard of the interference suppression method, and the TDP is defined as follows:

；

Wherein, Representing an accurate measure of target detection in the ith monte carlo experiment. Peak value searching is carried out on pulse pressure output of echo signals after interference suppression, and if the coordinates of peak points are consistent with the target positionsEqual to 1, otherwise 0.

The number of monte carlo experiments was set to 200. The method, the intra-pulse frequency modulation slope agile signal joint fractional order filtering method (ISASFF), the energy function detection joint bandpass filtering method (EFDBF) and the frequency coding signal joint fractional order filtering method (FCSFF) are adopted to carry out interference suppression on the interfered echo. The TDP versus SNR and JSR curves of the echo signal pulse pressure output after interference suppression are shown in fig. 11, 12 and 13 for different ISRJ. Fig. 11 is a schematic diagram of an echo signal TDP of ISDRJ interference after interference suppression, where (a) in fig. 11 is snr= -10dB; fig. 11 (b) shows snr= -5dB; fig. 11 (c) shows snr=0 dB. Fig. 12 is a schematic diagram of an echo signal TDP of ISPRJ interference after interference suppression, where (a) in fig. 12 is snr= -10dB; fig. 12 (b) shows snr= -5dB; fig. 12 (c) shows snr=0 dB. Fig. 13 is a schematic diagram of an echo signal TDP of ISCRJ interference after interference suppression, where (a) in fig. 13 is snr= -10dB; fig. 13 (b) shows snr= -5dB; fig. 13 (c) shows snr=0 dB.

In fig. 11, fig. 12 and fig. 13, TDP after interference suppression by the four methods is higher at a lower JSR, which indicates that the four methods can effectively suppress interference. As JSR increases, the TDP of all four methods drops to different extents. If the critical value of JSR is used as a measure of the anti-interference performance of different methods when TDP is more than or equal to 90%, the JSR tolerance of the four methods against different ISRJ under different SNR is shown in Table 2.

TABLE 2 JSR fault tolerance (dB) at different signal-to-noise ratios for different methods

As can be seen from table 2, as the SNR increases, the JSR margin for the different methods increases. Under the same conditions, the interference-to-signal ratio tolerance of the method of the embodiment is higher than that of the other three methods. When jsr=50 dB, the TDP after interference resistance in the method of this embodiment is still greater than or equal to 90%. In addition, compared with other three methods, the method of the embodiment is not affected by the interference types, and still can keep stable anti-interference performance under different ISRJ.

(3) The influence of sampling time delay of the jammer.

The simulation experiments are all carried out under synchronous sampling of the jammer. The anti-jamming situation when the jammer is sampling asynchronously is analyzed as follows. Let the sampling delay be 2 mus, jsr=25 db, snr=0 dB. The results of the method of this example for suppressing 3 ISRJ species respectively are shown in fig. 14, 15 and 16. Fig. 14 is a schematic diagram of ISDRJ suppression results (τd=2μs), where (a) in fig. 14 is an echo signal time-frequency diagram; fig. 14 (b) is a time-frequency diagram of the echo signal after signal reconstruction; fig. 14 (c) shows the pulse compression result of the proposed method after interference suppression. Fig. 15 is a schematic diagram of ISPRJ suppression results (τd=2μs), where (a) in fig. 15 is an echo signal time-frequency diagram; fig. 15 (b) is a time-frequency diagram of the echo signal after signal reconstruction; fig. 15 (c) shows the pulse compression result of the proposed method after interference suppression. Fig. 16 is a schematic diagram of ISCRJ suppression results (τd=2μs), where (a) in fig. 16 is an echo signal time-frequency diagram; fig. 16 (b) is a time-frequency diagram of the echo signal after signal reconstruction; fig. 16 (c) shows the pulse compression result of the proposed method after interference suppression.

As can be seen from fig. 14 and 16, when the jammer delays sampling, the jammer generated ISDRJ and ISCRJ interference slices still fall into the echo signal delay slices, so that the interference can be suppressed by the time domain preliminary filtering, and the target energy after the interference suppression is almost not lost. In fig. 15, when the echo signal is disturbed by ISPRJ, it can be seen from comparing fig. 15 (a) with fig. 8 (a) that the number of disturbed echo slices in the echo increases. And then, interference is restrained by adopting a mode of interference cancellation after signal reconstruction. As shown in fig. 15 (b), after interference cancellation, most of the interference is suppressed, but some strong scattering points still exist. Fig. 15 (c) shows a target range profile obtained by performing time-domain narrowband filtering on the pulse pressure output after interference cancellation, and thus, range side lobes generated by residual interference can be effectively suppressed.

FIG. 17 further simulatesThe value of the pulse pressure output is 0-1, the Monte Carlo experiment time is 100, and the target normalized amplitude of the pulse pressure output after the interference resistance of the method is carried out is along with the following conditions of other parametersIs a change curve of (a). In fig. 17, for ISDRJ and ISCRJ, the post-interference-suppression target normalized amplitude is approximately 1, since the interference slices all fall within the delay slices, and thus there is little loss of post-interference-suppression target energy. For ISPRJ, the sampling delay of the jammer increases the number of disturbed echo slices in the echo, thus increasing the target energy loss. In general, withThe normalized amplitude fluctuation degree of the target after interference suppression is not large, which indicates that the method of the embodiment is insensitive to the sampling time delay of the jammer.

In summary, for self-defense ISRJ, the present embodiment provides an anti-interference method based on intra-pulse parameter agile waveforms. Compared with the pulse frequency modulation slope agility signal, the embodiment introduces the frequency agility of the center of the sub-pulse above the frequency agility signal, and inserts a time delay slice between adjacent sub-pulses, thereby reducing the distance sidelobes after transmitting waveform pulse pressure and the engineering realization difficulty. The fuzzy function diagram of the designed waveform is similar to a thumbtack type, and has better distance and speed resolution capability. Echo slice classification takes advantage of the energy focusing of the FrFT on the chirp signal and achieves more robust performance. And during interference suppression, echo signal data are fully utilized, wherein the signal reconstruction of fractional order domain is carried out on the interfered echo slice, the target energy is reserved, a narrow-band filter is constructed on the time domain of the undisturbed echo slice, and the influence of distance side lobes generated by residual interference is reduced. The TDP of the method is more than or equal to 90 percent when JSR=50 dB, and the anti-interference capability of the radar is effectively improved.

Example 6:

On the basis of the intermittent sampling forwarding interference active countermeasure method provided in the above embodiment 1, embodiment 6 of the present invention further provides an intermittent sampling forwarding interference active countermeasure system, as shown in fig. 18, where the system includes a transmit waveform design module, a slice division module, a slice identification module, a reconstruction module, and a filtering module; wherein: the transmitting waveform design module is used for designing a transmitting waveform of a transmitting signal, the transmitting waveform comprises a plurality of sub-pulses, center frequency and frequency modulation slope are adopted in the sub-pulses, and time delay is inserted between adjacent sub-pulses; the slice dividing module is used for dividing the echo signals into a plurality of slices according to the pulse width of the transmitting signals, and setting the signals in the echo slices at the corresponding positions to zero according to the time delay positions inserted among the transmitting signal sub-pulses; the slice identification module is used for identifying each echo slice except the zero echo slice and judging whether the echo slice is an interfered echo slice or a non-interference echo slice; the reconstruction module is used for constructing a sparse matrix of a fractional order domain and reconstructing a target and interference in the interfered echo slice by using a compressed sensing algorithm; the filtering module is used for constructing a time domain narrow-band filter by utilizing the undisturbed echo slice, further filtering the echo pulse pressure output after target reconstruction, and reducing a distance side lobe caused by residual interference.

The specific functions of the modules of the above system are mapped to the descriptions of the method steps in embodiment 1, and will not be described herein.

In addition, on the basis of the intermittent sampling forwarding interference active countermeasure method provided in the above embodiment 1, the present invention further provides an intermittent sampling forwarding interference active countermeasure device that can be used to implement the above method and system, as shown in fig. 19, which is a schematic diagram of a device architecture in an embodiment of the present invention. The intermittent sampling forwarding interference active countermeasure device of the present embodiment includes one or more processors 21 and a memory 22. In fig. 19, a processor 21 is taken as an example.

The processor 21 and the memory 22 may be connected by a bus or otherwise, which is illustrated in fig. 19 as a bus connection.

The memory 22 serves as a non-volatile computer readable storage medium for storing non-volatile software programs, non-volatile computer executable programs and modules, such as the intermittent sample forwarding interference active countermeasure method of example 1. The processor 21 executes various functional applications and data processing of the intermittent sample forwarding interference active countermeasure device by running nonvolatile software programs, instructions, and modules stored in the memory 22, that is, implements the intermittent sample forwarding interference active countermeasure method of embodiment 1.

The memory 22 may include high-speed random access memory, and may also include non-volatile memory, such as at least one magnetic disk storage device, flash memory device, or other non-volatile solid-state storage device. In some embodiments, memory 22 may optionally include memory located remotely from processor 21, which may be connected to processor 21 via a network. Examples of such networks include, but are not limited to, the internet, intranets, local area networks, mobile communication networks, and combinations thereof.

The program instructions/modules are stored in the memory 22 and when executed by the one or more processors 21 perform the intermittent sample forwarding interference initiative countermeasure method of embodiment 1 described above, for example, performing the steps shown in fig. 1 described above.

The product can execute the method provided by the embodiment of the application, and has the corresponding functional modules and beneficial effects of the execution method. Technical details not described in detail in this embodiment may be found in the methods provided in the embodiments of the present application.

It should be noted that the above-described apparatus embodiments are merely illustrative, and the units described as separate units may or may not be physically separate, and units shown as units may or may not be physical units, may be located in one place, or may be distributed over a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

From the above description of embodiments, it will be apparent to those skilled in the art that the embodiments may be implemented by means of software plus a general purpose hardware platform, or may be implemented by hardware. Those skilled in the art will appreciate that all or part of the processes implementing the methods of the above embodiments may be implemented by a computer program for instructing relevant hardware, where the program may be stored in a computer readable storage medium, and the program may include processes of the embodiments of the methods described above when executed. The storage medium may be a magnetic disk, an optical disk, a Read Only Memory (ROM), a random access Memory (Random Access Memory, RAM), or the like.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; the technical features of the above embodiments or in the different embodiments may also be combined within the idea of the invention, the steps may be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in details for the sake of brevity; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.

Claims (8)

1. An intermittent sampling forwarding interference active countermeasure method, comprising:

designing a transmitting waveform of a transmitting signal, wherein the transmitting waveform comprises a plurality of sub-pulses, the central frequency and the frequency modulation slope of the sub-pulses are adopted to be changed rapidly, and time delay is inserted between adjacent sub-pulses; the transmitting waveform comprises an intra-pulse frequency coding combined frequency modulation slope agility waveform; wherein: assume that the pulse width of the radar transmit signal is The sub pulse width isThe time delay length of adjacent sub-pulse insertion is，≥; The number of sub-pulses included in the transmit pulse is，Representation rounding; the bandwidth range of the sub-pulse is [ B _min,B_max ]; the bandwidth of the nth sub-pulse is，Is the minimum interval of the sub-pulse bandwidth; encodes a sequence for sub-pulse bandwidth, an In the time-course of which the first and second contact surfaces,; The adjacent sub-pulses adopt positive and negative modulation slopes, and the modulation slope of the nth sub-pulse is; The center frequency of the nth sub-pulse is，Representing the initial carrier frequency of the radar transmit pulse,For the minimum interval of sub-pulse carrier frequencies,Maximum interval of sub-pulse carrier frequency; encodes a sequence for a sub-pulse frequency, an In the time-course of which the first and second contact surfaces,; The intra-pulse frequency coding joint frequency modulation slope agility signal transmitted by the radar is:

；

In the method, in the process of the invention, For the nth sub-pulse of the transmit pulse,；

Is a rectangular window function;

dividing an echo signal into a plurality of slices according to the pulse width of a transmitting signal sub-pulse, and setting zero for signals in echo slices at corresponding positions according to the time delay positions inserted between the transmitting signal sub-pulses;

identifying each other echo slice except the zero echo slice, and judging whether the echo slice is an interfered echo slice or a non-interference echo slice;

Constructing a sparse matrix of a fractional order domain, and reconstructing a target and interference in the interfered echo slice by using a compressed sensing algorithm; the method specifically comprises the following steps: target-interference joint dictionary construction: constructing a sparse matrix by adopting a Pei type discrete FrFT algorithm; the structured target-interference joint dictionary is ; Wherein the sparse matrixes corresponding to the interference and the target are respectivelyAnd; Observing the disturbed echo slices: constructing an observation matrixAnd (2) andIs a Gaussian random matrix which is independently and uniformly distributed; the observed signal vector obtained by measuring the ith echo slice is; In the method, in the process of the invention,For the target-interference joint sparse vector,As a result of the sparse vector of the target,Is an interference sparse vector; In the event of a noise occurrence, An observation vector that is noise; The solution of (2) is as follows: ; wherein, Is a constant related to noise; the target signal in the reconstructed ith slice is:；

And constructing a time domain narrow-band filter by using the undisturbed echo slice, further filtering pulse pressure output of the echo signal after target reconstruction, and reducing a distance side lobe caused by residual interference.

2. The intermittent sampling forwarding interference active countermeasure method according to claim 1, wherein the identifying each remaining echo slice to determine whether it is an interfered echo slice or a non-interfered echo slice specifically includes:

Traversing the FrFT of the echo slice on fractional order, finding out the transformation order when the output of the FrFT of the echo slice takes the maximum value, and comparing the transformation order with the optimal transformation order of the sub-pulse corresponding to the transmitting signal;

when the error is greater than the decision threshold, the echo slice is determined to be a disturbed echo slice; and when the error is less than or equal to the decision threshold, the echo slice is determined to be a non-interfering echo slice.

3. The intermittent sampling forwarding interference active countermeasure method of claim 2, wherein the set of echo slices to be identified is; Setting the traversing range of fractional orders to be 0-2, and setting the step length to be; Performing order traversal on the FrFT of each echo slice, searching for the corresponding fractional order when the FrFT output of the echo slice reaches the maximum value, and obtaining the optimal order set of the echo slice；

Recording the optimal conversion order set of the transmitting sub-pulses as; The obtained optimal order set of echo slicesAnd (3) withComparing; setting the threshold value as，; When (when)When the echo slice is judged to only contain the target, namely the undisturbed echo slice; when (when)And when the echo slice is interfered, judging that the echo slice is the interfered echo slice.

4. The intermittent sampling forwarding interference active countermeasure method according to claim 1, wherein the target and the interference in each interfered echo slice are reconstructed, and finally an echo signal after the reconstruction of the target is obtained.

5. The intermittent sampling forwarding interference active countermeasure method according to any one of claims 1 to 4, wherein the constructing a time-domain narrow-band filter by using the non-interference echo slice, and the filtering the pulse pressure output of the echo signal after the target reconstruction further specifically includes:

Convolving the non-interfering echo slices with the transmit signal, thereby constructing a normalized time-domain filter;

Convolving the echo signal after target reconstruction with the transmitting signal to obtain pulse pressure output of the echo signal after target reconstruction;

and the pulse pressure output of the echo signal after target reconstruction is further subjected to a normalized time domain filter to obtain the final pulse pressure output after time domain filtering.

6. An intermittent sampling forwarding interference active countermeasure device for implementing the intermittent sampling forwarding interference active countermeasure method according to any one of claims 1 to 5, characterized in that the device includes:

at least one processor; and a memory communicatively coupled to the at least one processor; wherein the memory stores instructions executable by the at least one processor for performing the intermittent sample forwarding interference initiative countermeasure method of the first aspect.

7. An intermittent sampling forwarding interference active countermeasure system, applying the intermittent sampling forwarding interference active countermeasure method according to any one of claims 1 to 5, characterized in that the system comprises a transmit waveform design module, a slice division module, a slice identification module, a reconstruction module and a filtering module; wherein:

The transmitting waveform design module is used for designing a transmitting waveform of a transmitting signal, the transmitting waveform comprises a plurality of sub-pulses, center frequency and frequency modulation slope are adopted in the sub-pulses, and time delay is inserted between adjacent sub-pulses;

The slice dividing module is used for dividing the echo signals into a plurality of slices according to the pulse width of the transmitting signals, and setting the signals in the echo slices at the corresponding positions to zero according to the time delay positions inserted among the transmitting signal sub-pulses;

The slice identification module is used for identifying each echo slice except the zero echo slice and judging whether the echo slice is an interfered echo slice or a non-interference echo slice;

The reconstruction module is used for constructing a sparse matrix of a fractional order domain and reconstructing a target and interference in the interfered echo slice by using a compressed sensing algorithm;

The filtering module is used for constructing a time domain narrow-band filter by utilizing the undisturbed echo slice, further filtering the echo pulse pressure output after target reconstruction, and reducing a distance side lobe caused by residual interference.

8. A non-transitory computer storage medium storing computer-executable instructions for execution by one or more processors to perform the intermittent sample-and-repeat interference initiative countermeasure method of any of claims 1-5.