Robust Channel Mismatch Estimation in Multichannel HRWS SAR Based on Range Spectrum Analysis

Abstract

In multichannel High-Resolution and Wide-Swath (HRWS) Synthetic Aperture Radar (SAR) systems, channel amplitude and phase mismatches would degrade the performance of azimuth ambiguity suppression as well as range sampling mismatches. To address this problem, a robust estimation method based on range spectrum analysis is proposed in this letter. The method includes two steps: firstly, by exploiting the interferometric phases between the range spectrums of adjacent channels, the proposed method can robustly estimate range sampling mismatches by the combination of phase unwrapping and a weighted least squares fitting. Secondly, based on the theory of spatial cross correlation, an accurate Doppler centroid and phase mismatches could be obtained from constant phases between adjacent channels. Compared with traditional methods, the proposed method overcomes the effect of phase wraps and jumps on polynomial coefficient estimation. It not only improves the robustness of parameter estimation but also can simultaneously obtain the Doppler centroid and phase mismatches. Experimental results based on airborne real data and simulated data validate its effectiveness of the proposed method.