Range-Variant Channel Errors Calibration Algorithm for Multichannel HRWS SAR Imaging

Azimuth multichannel SAR system can realize high-resolution and wide-swath (HRWS) SAR imaging, which has attracted intensive research interests. The azimuth ambiguities of multichannel SAR can be suppressed by digital beamforming (DBF) techniques. However, the presence of inevitable channel errors deteriorates the performance of ambiguity suppression. In this paper, we focus on the research of range-variant channel phase errors. We analyze the effect of radial position errors by using the second order Taylor series to expand the azimuth phase history. It indicates that the radial position errors can be regarded as range-variant phase errors. We divide the raw data into several blocks along range direction. Then we use the azimuth cross-correlation technique to estimate the phase errors of each block data. Compared with the subspace-based calibration techniques, the azimuth crosscorrelation technique does not use the information of azimuth ambiguities. Afterwards, the fitting process is employed to estimate the range-variant channel phase errors. Finally, the experiments on real data processing validate the effectiveness of our proposed method.