Research On Radar Countermeasures For Interrupted Sampling Repeater Jamming In Time And Frequency Domain

A digital radio frequency memory(DRFM)beased interrupted sampling repeater jamming can achieve certain gain in radar signal processing,which greatly improves the jamming efficiency.The jamming can also be easily hold on the target to form a main lobe jamming,posing a great threat to the radar.Currently,array signal processing is the main anti-jamming technology.However,when dealing with interrupted sampling repeater jamming,such methods may face the problems of estimation of pure jamming covariance matrix,mainlobe distortion,increasing of system scale,et al.Many key technologies have yet to be broken.Therefore,as a support and complement to the array signal processing based anti-jamming technologies,the dissertation tries to form a dynamic anti-jamming strategy consisting of jamming perception,jamming suppression and adaptive transmitting under a single-channel radar.The main contents and achievements of the paper are as follows:(1)The mechanism of interrupted sampling repeater jamming is studied.With pulse compression,the jamming will appear as multiple range false targets(groups)and seriously affect the radar detection.The three main strategies of interrupted sampling direct jamming(ISDJ),interrupted sampling repeater jamming(ISRJ)and interrupted sampling cyclic jamming(ISCJ)are mainly studied in this paper.The jamming signal model is established and the analytical expression of pulse compression results are deduced,with which the cause of the false targets(groups)is theoretically explained.Then,the relatinship between jamming parameters and jamming characteristics(such as false targets distribution,false targets number,false targets peak amplitude,et al)is built.The correctness of conclusions and the jamming performance are verified and analysised with simulations,providing a theoretical basis for the subsequent jamming perception and suppression studies.(2)The interrupted sampling repeater jamming perception methods are researched.Based on the characteristeritics analysis of autocorrelation and cross-correlation functions of jamming envelope,a general jamming perception method is designed for linear frequency modulation(LFM)and phase coded(PC)waveforms.Then,for LFM signal,a jamming recognition and parameter estimation method based on time-frequency analysis and deconvolution processing is proposed,which effectively improves the jamming slice width estimation accuracy.The feasibility and performance of the two methods are verified and compared through simulation and experimental data analysis.The results show that the proposed methods can effectively identify the jamming stratergy and estimate the key parameters,providing the necessary prior information for the subsequent jamming suppression and adaptive waveform design.(3)The interrupted sampling repeater jamming suppression technologies are studied.Two jamming suppression methods of adaptive "reconstruction & cancellation" and spectral envelope compensation are proposed for both LFM and PC waveforms.The former reconstructs the jamming with the results of jamming recognition and parameters estimation,and implements jamming cancellation with adaptive CLEAN method;and the latter achieves jamming suppression through spectrum correction.Futhrermore,a time-frequency filtering method and a wide-narrow-band alternate transmitting method are proposed for LFM signal.The time-frequency filtering method constructs a filter to suppress the jamming on the basis of jamming identification.While the wide-narrow-band alternate transmitting method recognizes and removes the false targets according to the relationship between the jamming peak distribution and the transmitting signal bandwidth.The feasibility and performance of the algorithms are verified and analyzed with simulation and experiments.The implementation difficulty,performance and applications of the four jamming suppression methods are campared,providing a reference to the choice of optimal anti-jamming method for different scenarios.(4)The adaptive confrontation technology for interrupted sampling repeater jamming is researched.For the changing jamming strategies,a dynamic confrontation technology based on adaptive transmitting is studied.The operator matrix of interrupted sampling repeater jamming is established.Then,with matrix decomposition theory,the eigenvectors corresponding to zero eigenvalues,which are time discontinuous,are used as transmission to achieve jamming suppression.Considering that the jammer will stop sampling when detects the falling edge of the pulse,some carefully designed protection pulses are inserted at the discontinuities of the eigenvectors.Thus a dynamic anti-jamming flow based on the adaptive transmitting design can be formed.The feasibility and jamming suppression performance of the method are verified and quantitative evaluated with simulations in typical scenarios.