A refined three-step focusing algorithm based on spatial variation characteristic of spaceborne sliding spotlight SAR

This paper deals with the problem of azimuth imaging worsening when three-step focusing algorithm fulfills imaging requirements of sliding spotlight SAR with wide azimuth swath. This is caused by spaceborne sliding spotlight SAR spatial variation characteristic: single point target´s relatively large range cell migration and azimuth point targets´ different Doppler experiences at different azimuth locations. To solve this problem phase error introduced by the equivalent strabismus model is compensated and the reference Doppler rate in the first step of TSFA is modified. A comparison of the imaging results to one azimuth 15km swath scene between refined TSFA and original TSFA is exhibited through simulations. The results prove that refined TSFA is able to get consistent good azimuth imaging quality of wide swath scene.