Study On The Imaging Techniques For Bistatic Forward-looking FOPEN SAR Systems

As bistatic synthetic aperture radar(BiSAR)has the characteristics that its transmitter is separated to its receiver and the imaging geometry can be configured flexibly,it can implement high resolution imaging of the scene in the forward direction of the radar carrying platform with the appropriate geometry layout.At the same time,the problem of imaging dead zone in the forward direction in the traditional SAR can be solved effectively in the BiSAR platform.Therefore,it is of great applicable importance in the aspects such as the guidance of aircraft landing,the military reconnaissance and the precise guidance of the missile.In this dissertation,the spatial resolution characteristic,time-domain imaging algorithms and the imaging techniques in the spotlight mode of the foliage penetration(FOPEN)low frequency ultra-wideband bistatic forward-looking SAR(BFSAR)are studied.The main content of this dissertation is summarized as follows:1.The spatial resolution characteristic of the bistatic forward-looking FOPEN SAR is studied,and the general expression of the spatial resolution in different imaging geometries is derived.Because of the complicated imaging geometry and the large fractional signal bandwidth of the bistatic forward-looking FOPEN SAR,the traditional methods of spatial resolutions analysis in bistatic SAR are not appropriate any more.To solve this problem,the spatial resolution analysis method based on the spectrum is proposed.This method can help obtain more accurate descriptions of the spatial resolutions in bistatic forward-looking FOPEN SAR.2.The time-domain imaging algorithms of the bistatic forward-looking FOPEN SAR are studied.To improve the imaging quality of the bistatic forward-looking FOPEN SAR,the back projection(BP)algorithm is introduced here.To solve the problem of the low efficiency of BP algorithm,the local back projection(LBP)algorithm and the fast factorized back projection(FFBP)algorithm with the modified expression of phase error control are proposed.The validity of the studied approaches is proved by some simulated experiments.3.The imaging techniques in the spotlight mode of the bistatic forward-looking FOPEN SAR are studied.To implement the continuous surveillance to the scene in the forward direction,the spotlight bistatic forward-looking SAR and video SAR are introduced,and the simulation results prove the feasibility of the proposed approach.