Study On Fast Time-domain Imaging And Moving Target Indication Algorithm For Airborne SAR

The conventional time-domain imaging algorithm has the disadvantage of large calculation,it is necessary to accelerate the imaging speed through sub-aperture division and image fusion.However,most of the researches on fast time-domain imaging algorithm are used for the spotlight SAR mode.There are still some problems when applying the FFBP algorithm to the stripmap mode.When detecting moving targets in SAR images under high-speed maneuvering flight conditions,there is a problem of mismatch between views in the commonly used symmetric Doppler view cancellation method.In view of the above problems,this paper mainly studies the FFBP algorithm in the strip SAR mode and the complex image domain moving target indication algorithm in high-speed maneuvering flight conditionsWe introduces the conventional BP imaging algorithm as well as the improved algorithm,such as FBP algorithm and FFBP algorithm.By comparing calculation and processing results,FFBP algorithm is selected for imaging as a better choice,aiming at stripmap SAR processing.Firstly,the signal model of stripmap SAR is given,and the problems existing when FFBP algorithm is directly applied to stripe SAR are analyzed,including the effect of invalid integration and the increasing calculation caused by oversampling in the angular domain.To solve these problems,the FFBP algorithm in the strip SAR mode is realized by the integrated aperture selection and the image overlapping method,respectively.The relationship between the partial SAR image and the full-aperture image is analyzed from the perspective of wavenumber domain,and the appropriate sub-aperture processing length is given.This method take advantage of FFBP algorithm's computational efficiency while ensuring the integrity of the pixel integral aperture.Finally,the effectiveness of this method is verified by simulation experiments.The time-domain imaging algorithm focuses stationary targets,while moving targets in the scene are also worth studying.This paper studies at the moving target indication method in the complex image domain in SC-SAR system,and propose a wavenumber-domain adaptive processing method based on symmetric Doppler cancellation.Compared with the existing joint pixel adaptive processing(SDP)method,it can greatly improve the operation efficiency while ensuring the performance of moving target extraction.This chapter first studies the moving target signal model,introduces the basic principles of the symmetric Doppler view cancellation method,and analyzes in detail the image matching problems of the method under high-speed maneuvering flight conditions.Using the SDP method instead of the view cancellation method can avoid the influence of pixel errors on the extraction effect of moving targets.In order to solve the shortcomings of the SDP method with too much calculation,this paper proposes a new wavenumber domain adaptive processing method,which is more efficient than the SDP method and is suitable for different image mismatch scenarios.After theoretical analysis and multiple experiments,the performance advantages of this method over the SDP method are verified.