Improved DBF algorithm for multichannel SAR with highly nonuniform sampling

The next generation of space-borne synthetic aperture radar (SAR) systems will emphasize on high-resolution and wide-swath imaging. For these design purposes, multichannel technology in azimuth is a promising candidate. In the multichannel SAR system, the nonuniform azimuth signal needs to be reconstructed when the pulse repetition frequency (PRF) deviates from a specific one. The traditional digital beamforming (DBF) algorithm works well just in the cases of uniform sampling and moderately nonuniform sampling. If there is highly nonuniform sampling or coinciding sampling, this method may fail. In this paper, a new method to handle the cases of highly nonuniform sampling is proposed. The proposed method is based on an equivalent sampling strategy and the minimum mean square error (MMSE) criterion. It is robust over a wide range of PRF. Compared to the conventional algorithms, this method dramatically improves the SNR, which is validated by simulation experiments.