An improved step transform algorithm for high squint angle SAR imaging

Step-transform algorithm had been proposed for SAR imaging. However, it is difficult to be used directly in high squint angle SAR. High squint angle SAR imaging suffers from the large range cell migration and the non-negligible cubic phase term. In this paper, an improved step-transform algorithm called time-varying step-transform algorithm is proposed. It uses varying chirp rates to deramp the signal in different subapertures to eliminate the focus range problem. The steps between subapertures are also varied according the deramping chirp rate. The non-negligible cubic phase is compensated in each subaperture. The performance of the algorithm is demonstrated by computer simulation