Research On Complex Motion SAR Echo Model And Imaging Method

Synthetic Aperture Radar(SAR)enables high-resolution microwave images of observed scenes under all lighting/weather conditions.The complex motion platform SAR is based on the fighter aircraft.The traditional imaging algorithm is no longer applicable because the trajectory is a three-dimensional curve due to the deviation from the ideal motion state.Therefore,how to realize high-resolution imaging of the observation scene by complex motion platform SAR is needed to study.In this thesis,a complex motion platform SAR model is established.The difference between the complex motion SAR and the ideal motion SAR is analyzed in detail,the algorithms suitable for complex motion imaging with small and larger motion errors.The main content is divided into the following three parts:Firstly,this thesis analyzes the difference between complex motion SAR and ideal motion SAR from four aspects: motion error,phase error,Doppler parameter and azimuth resolution.In the motion error,the azimuth echo signal is a non-linear FM signal,and if it is not motion compensated,it will result in non-uniform sampling of azimuth.The influence of phase error of different order on echo signal is analyzed in phase error.The azimuthal resolution of the azimuthal resolution is redefined: the azimuthal echo signal is compressed and the main lobe is-3dB wide.In the Doppler parameter,the variability of the Doppler bandwidth of the complex motion SAR under different motion models is analyzed.The variability of the complex motion Doppler process is analyzed.It is concluded that the complex motion SAR needs to adopt the BP algorithm Scene for point-by-point imaging.Then this thesis introduces a complex motion imaging algorithm for small motion error cases:BP algorithm based on IMU measured data.Firstly,the Legendre orthogonal polynomial is obtained from the imaging index.The optimal basis function of the algorithm is obtained.Then,the acceleration,velocity and position error tolerance of the algorithm are obtained.This algorithm is only suitable for small measurement Error situation,when the measurement error is large need to take based on the echo data parameter estimation BP algorithm.Finally,this thesis introduces a complex motion imaging algorithm suitable for large motion error situations: A BP Algorithm for Phase Tracking of strong signal information based on Anti-Legendre coefficient.The influence of the signal-to-phase tracking algorithm is studied,and the influence of the number and the geometric distribution on the radar position is analyzed.Then,by setting the appropriate signal-to-noise ratio and the number of strong points using the Legendre coefficients,the phase compensation history of the radar platform is obtained,and the phase compensation factor of the BP algorithm is constructed and applied to the BP algorithm to verify the effectiveness of the algorithm.