Study Of Imaging Method Of Video Sar Movintg Target

Synthetic aperture radar(SAR),as the all-weather,24-hour,multi-frequency remote sensing method,has now become an important tool for microwave remote sensing.As a new type of radar system,the video synthetic aperture radar(video SAR)is able to observe the target area continuously and present the images of target area via video.Video SAR shares great advantages in military operations such as real-time attack,target tracking and observation.Therefore,video SAR has attracted wide attention and become a research hotspot as soon as it is proposed.This thesis mainly studies single-channel video SAR moving target imaging methods and image quality assessment methods for moving targets and scene targets.The main content covers the following parts:Firstly,the basic principles and imaging algorithms of video SAR imaging are described.The influence of parameters such as transmitted frequency and fighter speed on the imaging frame rate of video SAR are analyzed.With the established target echo signal model of moving targets in orthogonal mode,the influence of the moving target on Doppler center frequency,Doppler FM rate and the influence on SAR imaging are analyzed.The final simulation verification is accomplished.Secondly,the circular model of the moving target imaging in the single-channel circular mode is studied.With the established moving target echo model that based on Vector Forms,the characteristics of the subaperture imaging and moving target imaging characteristics in the circular mode are analyzed.Based on the geometrical relationship and velocity vector relationship between image point and target point on the subaperture,the position-velocity motion parameter equation is established for the uniform linear motion target and solved by two subaperture images.For the uniform acceleration linear motion target,the parameter equation is established by estimating the target Doppler frequency.The stability of the solution of equation is analyzed via the condition number of the simultaneous equation of Newton solution.The simulation analysis of the parameter estimation effect is performed.Thirdly,the Doppler frequency estimation method based on the minimum entropy criterion of image is studied.The evaluation method of the moving target blur degree and focusing effect is proposed.The main lobe expansion coefficient assessment method is proposed for the disadvantage that the minimum entropy cannot compare the focusing degree of multiple pictures.The concept of coherent correlation function(CCF)is introduced to overcome the following disadvantages: the difficulty of extracting point targets from images;the shortcoming of being susceptible to noise interference.The significance of CCF is described and the pulse echo response of point target,scene target,stationary target and moving target are estimated via CCF.The image quality parameters are obtained and the effects of motion on parameters such as target peak and main lobe width are analyzed.The CCF is used to evaluate the degree and focusing effect of the moving point target and the surface target.The effectiveness and universality of the evaluation method are verified by simulation.Finally,this thesis summarizes the relative works and points out the shortcomings and possible solutions of the motion parameter estimation method proposed in this thesis.