Motion-Adaptive Digital Beamforming Technique for Multichannel SAR Systems

Abstract

This work introduces an innovative motion-adaptive algorithm for synthetic aperture radar (SAR) airborne systems implementing digital beamforming (DBF) techniques in the along-track direction. The inherent challenges posed by temporal variations in antenna phase centers, resulting from irregular across-track baselines and attitude angles, critically affect the quality of SAR image formation due to azimuth ambiguities. A novel multichannel relative motion compensation (RelMoCo) approach is proposed to efficiently correct residual phase errors arising from these temporal variations, particularly in scenarios involving aliased azimuth spectra. Additionally, the algorithm utilizes small 2D block processing to effectively accommodate relative differences between the antenna patterns of each receiver across three dimensions: squint, off-nadir, and frequency. The performance of this approach is evaluated using real airborne SAR data collected from the DBFSAR system of the German Aerospace Center (DLR). Furthermore, the potential application of this technique in spaceborne distributed SAR systems with varying across-track baselines is discussed.