An Improved Range Doppler Algorithm Based on Squint FMCW SAR Imaging

The existing range-Doppler algorithms for SAR imaging are affected by a fast-time Doppler effect so they cannot be directly applied to FMCW SAR. Moreover, range migration is more evident in squint mode. To reveal the influence of the continuous motion of FMCW SAR in the squint mode on the echo signal and optimize the imaging process, an improved range-Doppler algorithm is based on squint FMCW SAR imaging is proposed in this paper. Firstly, the imaging geometry model and echo signal model of FMCW SAR are analyzed and deduced. The problem of Doppler center offset under squint mode is eliminated by linearly correcting the echo signal. By dealing with the range migration in the frequency domain, the processing process can be simplified. Finally, the effectiveness and feasibility of the algorithm are verified by simulation. The results are as follows: (1) The image quality is improved by correcting the linear motion in squint mode. (2) The peak sidelobe ratio (PSLR) and the integral sidelobe ratio (ISLR) of the imaging index of the improved algorithm are close to the theoretical values. Therefore, the improved range-Doppler algorithm can effectively perform high-efficiency imaging in the case of squint.