Study Of High Resolution Imaging Techniques For One-Stationary Low Frequency Bistatic SAR

One-stationary low frequency bistatic synthetic aperture radar(OS LF BSAR)refers to a kind of new radar system,which has a receiver(or transmitter)located at the stationary flatform,while a transmitter(or receiver)placed at the moving flatform,and works in the low frequency(<1GHz).This system has several advantages,such as the high operational flexibility,low-cost system design,increased reliability,remarkable foliage penetrability,obtaining more information and so on,thus it has gained wide attention and becomes a promising technology with the great potential.This dissertation is referred to three BSAR systems with different configurations,i.e.,the OS LF BSAR working in stripmap mode,one-stationary low frequency bistatic circular SAR(OS LF BCSAR),and one-stationary low frequency bistatic forward-looking SAR(OS LF BFSAR).Combining with the engineering application in practice,this paper focuses on the high-resolution imaging techniques for these above-motioned OS LF BSAR systems,and several valuable research results have been achieved.The main content of this dissertation is summarized as follows:1.The characteristics of the OS LF BSAR system are analyzed,mainly including the spatial variance of the bistatic slant range,the coupling of the echo signal and the spatial resolution,which can provide a theory basis for the following study.The resoluts shows that the bistatic slant range is both range and azimuth variant,and its variance increases by reducing the center frequency;the coupling of the echo signal is very serious,and the coupling increases by reducing the center frequency;the spatial resolution is much related to the center frequency,fractional signal bandwidth,the integration angle and side-glance angle of the moving radar,and so on.2.The fast echo signal simulation is studied for the OS LF BSAR system.For the OS LF BSAR system with the linear track,the fast echo signal simulation method based on the equivalent scatterer and fast Fourier transform(FFT)operation is proposed,which can fast generate the high-precision OS LF BSAR echo signal.For the OS LF BSAR system with the nonlinear track,the fast echo signal simulation method based on the equivalent scatterer and nonuniform FFT(NUFFT)operation is proposed.This method considers the radar motion errors,which can simulate the OS LF BSAR echo signal with the high precision and efficiency.3.The fast time domain imaging approach is studied for the OS LF BSAR system.For the OS LF BSAR system with the linear track,the bistatic fast factorized backprojection algorithm(BFFBPA)based on the elliptical polar coordinate is proposed.This method can not only keep the accuracy of the backprojection algorithm(BPA),but also significantly improve the imaging efficiency.For the OS LF BSAR system with the nonlinear track,the BFFBPA integrating the motion compensation is proposed.This method considers radar motion errors,which can implement the OS LF BSAR imaging with the high precision and efficiency.4.The fast time domain imaging approach is studied for the OS LF BSAR systems with the special configurations.For the OS LF BCSAR system,improving the BFFBPA based on the elliptical polar coordinate,the BFFBPA suitable for the OS LF BCSAR imaging is proposed,which can implement the OS LF BCSAR imaging with the high precision and efficiency.For the OS LF BFSAR system,improving the BFFBPA based on the polar coordinate,the BFFBPA suitable for the OS LF BFSAR imaging is proposed,which can implement the OS LF BFSAR imaging with the high precision and efficiency.In this dissertation,the abundant simulated data is used to carry out the simulated experiment,which proves the correctness of the theory analysis and the validity of the proposed method.Consequently,the achieved research results have great theory signification and potentially applicable value in practice.