A Subaperture Imaging Algorithm to Highly Squinted TOPS SAR Based on SPECAN and Deramping

As the azimuth beam sweeps at high squint angles, the real difficulty in processing high squinted terrain observation by progressive scans (TOPS) data is the azimuth spectrum aliasing of received signal and azimuth time aliasing after range cell migration correction (RCMC). For these problems, a subaperture imaging algorithm based on SPECAN and Deramping is proposed in this paper. Echo data is properly divided into subapertues so that azimuth spectrum without aliasing can be obtained; then the modified range migration algorithm (RMA), which can deal with the high squint case with low interpolation load, is used to perform RCMC; finally, the azimuth signal is focused in the Doppler domain by SPECAN and Deramping. To minimize the computation load of the proposed algorithm, the parameters used for SPECAN and Deramping should be accurately calculated. Point simulated SAR data in squinted TOPS mode are used to validate the effectiveness of the proposed algorithm.