Research On SAR Anti-deception-jamming Imaging Based On Random Modulated Signal

In recent years,with the development of Digital Radio Frequency Memory(DRFM)technology,the repeater interference based on DRFM has become an important type of active decoys interference.In this paper,we focus on SAR anti-jamming imaging technology against DRFM repeater interference based on random modulated signals.In the second chapter,the geometric model and theoretical basis of SAR imaging are introduced,and the SAR imaging processes based on the theory of pulse compression and Compressed Sensing(CS)are respectively described.This chapter provides an overview of the types of random modulation signal and its application in terms of interference,and focuses on some typical types of random modulation such as chirp slope varying,chirp slope polarity agility,and carrier frequency agility between pulses,and characteristics of each application in terms of radar interference.Finally,the theoretical basis of SAR anti-jamming imaging is analyzed,which is based on the theory of compressed sensing and signal modulation.In the third chapter,SAR anti-jamming method for one-dimension imaging with high resolution is proposed based on the slope-varying signal and the CS theory.By utilizing the signal slope agility,the true target and the false target echo signals differ in chirp slope.Under the theoretical background of compressed sensing and sparse signal recovery theory,different sparse dictionaries of the real target echo and jamming false target signal can be constructed and we can build a joint sparse dictionary of those to achieve the separation of the true target and false target.High resolution range imaging of the real targets can be achieved through this algorithm,in the inhibition of false targets at the same time.Theoretically,the method utilizes the advantages of signal separation theory,and can reconstruct the true target echo signal accurately,which has better anti-jamming effect.Simulation results also show that the proposed algorithm has better imaging performance and interference suppression effect compared to the traditional imaging method,especially in the false target interference enhancement or false target number increase,which has a more obvious anti-jamming advantage.The fourth chapter proposed a multiple modulation form of radar signal for the two-dimensional interference SAR imaging,combing slope polarity agility and the carrier frequency agility.By utilizing slope polarity agility,the false target jamming signal and the real echo signal are same in numerical value and opposite in polarity.After the matched filtering processing of range domain,false targets signal can be largely suppressed false targets.The research shows that the slope polarity agility signal has better anti-jamming effect than the slope varying signal,while avoiding the image resolution changes and other issues caused by the change of bandwidth in radar system.By utilizing the inter-pulse carrier frequency agile signal,combined with compressed sensing as the imaging method,we can further suppress interference in azimuth domain.The results show that the multiple modulation signals can achieve good interference suppression effect in the 2-D SAR imaging process.In the fifth chapter,the research contents are summarized,and the breakthrough point and the existing problems are analyzed.Based on this,the main contents and research directions of the following work are put forward.