Intermittent Sampling Forwarding Jamming Identification And Countermeasure Technology Research

Traditional suppressive jamming and deceptive jamming are difficult to form effective effects due to their low efficiency and slow response speed.Interrupted sampling repeater jamming(ISRJ)based on digital radio frequency memory(DRFM)intermittently sample and forward radar transmission signals at a low rate,which greatly improves the response rate of the jammer and forms a series of realistic and coherent false target groups in the victim radar.Starting from the characteristics of interrupted sampling repeater jamming,this paper conducts research on the identification and countermeasures of interrupted sampling repeater jamming.The main work of this paper is as follows:1.Deduction and simulation verify the jamming characteristics of interrupted sampling repeater jamming.Using the definition of ambiguity function,the influence of interrupted sampling repeater jamming on the signal processing of linear frequency modulation system and phase coding system radar is derived.Then the models of three common retransmission modes are given,and the effects of the three retransmission modes on the linear frequency modulation system and phase coding system radar signal processing are analyzed through simulation.2.Based on the support vector machine,the identification of interrupted sampling repeater jamming is realized.The algorithm uses three characteristics: the spectrum information entropy extracted from echo signal samples,the ratio of interrupted sampling period to slice width,and the ratio of slice signal forwarding period to slice width,and the support vector machine is trained to complete the construction of the classifier model.After the echo signals in different retransmission modes are input to the classifier,the echo signals are automatically classified into the pre-classified space,so as to achieve the purpose of jamming identification.Simulation shows that the algorithm can accurately identify jamming when the signal-to-noise ratio is above 0d B3.An orthogonal waveform design algorithm based on protection pulses is proposed to resist interrupted sampling repeater jamming.The algorithm first derives the constraint relationship between the jammer parameters of interrupted sampling repeater jamming and the optimal waveform.For the optimal waveform,the jamming is orthogonal to the target echo,so the jamming can be suppressed by pulse compression.Then use the minimum p-norm algorithm based on L-BFGS to design the orthogonal arbitrary phase encoding signal based on the protection pulse,and then further improve the anti-jamming performance of the waveform through the design of the mismatch filter.The simulation shows that the waveform designed by this algorithm can suppress the jamming of the three forwarding modes after being compressed by 5-10 d B than the waveform designed by the genetic algorithm.4.Designed anti-interrupted sampling repeater jamming algorithm based on positive and negative slope linear frequency modulation(LFM)signal cancellation.This algorithm utilizes the simultaneous multi-beam transmission capability of the digital array radar,using two beams pointing at the same time to simultaneously transmit LFM signals with positive and negative chirp rate.After receiving the echo signal,performing positive and negative slope signal separation and frequency phase compensation on the separated signal,and then subtract and eliminate jamming to obtain an anti-jamming signal.This algorithm avoids the estimation of jammer parameters.Simulations show that this algorithm can suppress jamming by 27.8d B in an environment with a jamming-to-signal ratio of 20 d B.