Research On High Resolution Imaging Technology Of FMCW SAR

Frequency modulated continuous wave synthetic aperture radar(FMCW SAR)is a system of the miniaturization of SAR.It has the advantages of small size,simple structure,low cost,and high resolution imaging.However,FMCW SAR system also has some problems to be solved,such as the frequency non-linearities exsit in the transmit signal,which will seriously deteriorate the imaging range resolution.This problem will limiting the application and development of FMCW SAR.In addition,with the growing demand for practical applications,the research of FMCW SAR system needs to be more miniaturization,higher resolution requirements,and better anti-interception,etc.The research of multi-channel FMCW SAR has widely attracted people's attention.Meanwhile,the amplitude and phase errors of multi-channels is a problem that can not be ignored.In view of the above problems,this paper mainly completed the following three aspects.First,a signal model of FMCW SAR is established.Based on the model of FMCW SAR,the paper studied the range-Doppler(Range-Doppler,R-D)algorithm of the side-looking FMCW SAR in depth.The detail realizing diagram of the algorithm is provided,and simulation tests show that the algorithm performs favorably with validity.The second is simulated and analyzed two non-linearity correction methods of FMCW SAR.One method is selected preferentially,which the non-linearity error is truncated by neglecting the high-order terms,and the feasibility of this approximation is demonstrated.An improved range-Doppler algorithm is proposed.It combines the non-linearity correction and the conventional range-Doppler algorithm.The range migration and Doppler shift induced by the continuous motion are also considered in the proposed algorithm.With the characters of high processing precision,it is very suitable for short distance detection.Third,simulated and analyzed the model of amplitude and phase error of single channel FMCW SAR in four different situations.The echo signal model is established of single channel FMCW SAR,which contained the amplitude and phase error.A method of amplitude and phase error correction is studied by simulation and analysis.In addition,a method based on the signals which are spatially and temporally disjoint with the separation angle known is presented to estimate the amplitude and phase error of multi-channel FMCW SAR without knowing the absolute directions of the signals.The efficiency of the method is verified with simulation.