Research On High Resolution Imaging Technology Of FMCW SAR

Frequency modulated continuous wave synthetic aperture radar(SAR)has attracted more and more attention because of its small size,light weight and high reliability.It is the combination of FMCW technology and synthetic aperture technology.It can not only achieve high-resolution imaging,but also realize the miniaturization of synthetic aperture radar.It meets the requirements of UAV and other small flight platforms for radar.It has great market value and is widely used in resource exploration,environmental monitoring,disaster relief and so on.Different from the traditional pulse SAR,the continuous motion of FMCW SAR during transmitting signal can not be ignored,and the "stop go stop" assumption is not tenable,so the traditional pulse SAR imaging algorithm is no longer applicable.Based on the characteristics of FMCW SAR,the imaging algorithm in monostatic and bistatic mode is studied,The main work is as follows:Firstly,the basic principle of FMCW SAR is introduced.Based on the analysis of the principle of synthetic aperture and dechirp technology,the echo signal of FMCW SAR is derived based on the geometric model of FMCW SAR,and the signal characteristics after dechirp processing are analyzed,which lays the foundation for the design of imaging algorithm of continuous wave SAR.Secondly,an improved algorithm is proposed for continuous Doppler signal distortion caused by fmrd during SAR transmission.At the same time,in order to expand the application of the improved algorithm,the improved Rd algorithm is applied to squint FMCW SAR imaging,and the high-resolution imaging effect is obtained through simulation.Secondly,the two-dimensional frequency domain imaging algorithm of FMCW SAR is studied.Due to the existence of Stolt interpolation in the traditional wavenumber domain algorithm,it not only introduces additional error,but also reduces the efficiency of the algorithm.Based on the improved algorithm,this paper proposes a wavenumber domain algorithm of FMCW SAR Based on squint.The correctness and effectiveness are verified by MATLAB simulation.The improved wavenumber domain algorithm proposed in this paper avoids interpolation and improves the processing efficiency and resolution.Finally,the imaging problem of FMCW SAR in bistatic mode is studied.Bistatic SAR is more flexible than monostatic SAR in obtaining information,but its slant range model of double root sign increases the complexity of algorithm processing.According to the characteristics of FMCW SAR echo signal,the series inversion method is introduced into the imaging processing of bistatic FMCW SAR,and a two-dimensional frequency-domain algorithm of bistatic FMCW SAR is proposed.The processing flow of the algorithm is simple,the interpolation operation is avoided,and the algorithm efficiency is greatly improved.The correctness and effectiveness of the algorithm are verified by MATLAB simulation.