Research On SAR Anti-jamming Technique Based On LFM-PC Waveform Design

Synthetic Aperture Radar(SAR)is an active microwave remote sensing system.It has been applied extensively for its characteristic of all-time and all-weather working compared with optical imaging.Deception jamming has been the research emphasis of jamming technology for its ability to generate false targets with less transmitting power.To suppress the deception jamming,anti-jamming methods,including alteration of the transmitted signal or its parameters at every position of the synthetic aperture,are proposed.LFM signal has a poor anti-jamming performance for its simple form.Phase coded signals and chaotic signals have good anti-jamming performance,but they are sensitive to Doppler.Based on the above background,the main research contents of this thesis are as follows:(1)We get a new compound modulation signal—LFM-PC signal by modulating the LFM signal using phase coded signal.The range resolution,Doppler tolerance and orthogonal performance of the signal is studied.Sequential quadratic programming(SQP)method is introduced to numerically optimize the ambiguity function of LFM-PC signal for its Doppler sensitive problem.We discuss the feasibility of polar format algorithm based on LFM-PC signal.(2)We propose an anti-jamming method based on orthogonal LFM-PC waveform agility.By transmitting orthogonal LFM-PC signals agilely,the range pulse compression gain can't be obtained by the jam.SQP method is employed to optimize the orthogonal LFM-PC waveform,and we establish the optimization model based on minimizing the peak side-lobe energy criterion.Simulation shows that the optimized LFM-PC signal has a good orthogonality and the anti-jamming method mentioned above has a good anti-jamming performance.(3)We propose n anti-jamming method based on adaptive initial phase.Conjugate gradient method is used to solve the problem of minimizing the interference amplitude among the region of the real target.Finally,we combine the above methods for better anti-jamming performance.Firstly,orthogonal LFM-PC waveform agility is used to make the jam unable to gain the range pulse compression gain.Then,the adaptive initial phase is designed to minimize the interference amplitude of the real target region.Simulation shows that the proposed method has a good anti-jamming performance.