Research On SAR Anti-jamming Technology Based On Waveform Diversity

Active coherent jamming represented by digital radio frequency memory(DRFM)in modern electronic warfare has strong coherence with SAR echo signal.Compared with ordinary noise interference,this interference can obtain the range-direction compression gain at the SAR receiver,which puts forward higher requirements for the anti-jamming ability of SAR system.In this paper,focusing on the suppression of typical active coherent jamming,based on waveform diversity,the following studies are mainly completed:1.The working principle of the DRFM jammer is studied.The characteristics of the transmission pulse and the radar pulse are lagging,and the feasibility of the waveform diversity anti-interference method is pointed out.The generation mechanism and mathematical model of two typical active coherent jamming,false target jamming and random frequency shift jamming,are also studied.The effects of two active coherent interferences on SAR imaging are simulated and analyzed.In order to restrain active coherent jamming,three kinds of anti-interference waveform sets are studied from the perspective of waveform diversity.2.Aiming at the problem that synthetic aperture radar is difficult to suppress active coherent interference,the anti-interference method for fine-tuning the inter-pulse frequency modulation slope is analyzed.By fine-tuning the frequency modulation slope of LFM signal at different slow times,the interference signal cannot fully obtain the compression gain of SAR processor in the distance direction,and the signal-to-jamming ratio is improved.The simulation verifies the good anti-interference performance of the method.3.A design method based on phase-perturbed chirp signal(PPLFM)is studied.Compared with the traditional LFM signal,the complexity of the waveform is increased,and the anti-interference ability can be effectively improved.Firstly,the design method of PPLFM signal is given,and its disturbance amplitude matrix is optimized.Then the anti-interference performance and imaging performance of PPLFM signal are analyzed.Finally,the anti-false target interference and frequency shift interference ability are compared with LFM signal.The simulation results show that compared with the traditional LFM signal,the new PPLFM signal can effectively suppress the active coherent jamming.4.The anti-jamming waveform design method based on Orthogonal Frequency Division Multiplexing(OFDM)technology is studied.The design method of OFDM-S AR signal is given.The influence of subcarrier weighting and Barker code modulation on the resolution of OFDM signal is analyzed.The ability of resisting false target interference and frequency shift interference is compared with that of LFM signal.The simulation results show that the OFDM-SAR signal has good anti-false target jamming and anti-random frequency shift jamming performance.