| Synthetic Aperture Radar(SAR)can obtain clear radar images of surface targets allday and all-weather which is one of the commonly used means in military reconnaissance.At the same time,in modern electronic countermeasures,SAR faces a complex electromagnetic environment,which is susceptible to various jamming and affects information acquisition.Among them,interrupted sampling repeater jamming(ISRJ)can quickly and flexibly produce suppression or deception effect in SAR images with small power by sampling and forwarding multiple times in one pulse time,and is not affected by traditional anti-jamming methods such as waveform agility,so it has great value and current significance for the research of anti-jamming methods.The signal model and characteristics of interrupted sampling repeater jamming,jamming detection method,jamming parameter estimation and suppression method are the core elements of anti-interrupted sampling repeater jamming.In this thesis,theoretical analysis,anti-interference method research and simulation experiments are carried out for the above research content,and the specific contents are as follows:1.The signal model of interrupted sampling repeater jamming is established,its principle and characteristics are analyzed,and the principle and effect of interrupted sampling repeater jamming on distance direction and distance & azimuth joint in SAR are discussed.2.The jamming characteristics of interrupted sampling repeater jamming in the signal domain and image domain are studied,and the mechanism of the influence of different sampling period and sampling duration on the jamming effect is analyzed,which lays a theoretical foundation for the research of anti-interrupted sampling repeater jamming method.3.An interference suppression method based on time-frequency analysis to construct a non-matched filter is proposed.The time-frequency characteristics of the jamming signal are analyzed.The sampling period,sampling duration and sampling start time are estimated,and a filter is constructed according to the estimated parameters,so as to realize the ISRJ suppression of SAR from the signal domain.4.A jamming identification method based on image domain features is proposed,and the feature information of interrupted sampling repeater jamming imaging results is used to directly identify jamming false targets from images,and the SAR image dataset of ISRJ is constructed.Finally,the identification performance of the proposed method for false targets of different intensities is analyzed.Based on the results of jamming identification,the jamming false target is directly eliminated from the image and the jamming suppression effect is evaluated.The results of this thesis,which have been achieved through theoretical analysis and simulation verification of the aforementioned jamming models and anti-jamming methods,demonstrate that the proposed method is capable of effectively suppressing the ISRJ in SAR. |
