Undesired Signal Suppression for Hybrid-Baseline Multichannel SAR

The performance of conventional algorithms for along-track baseline multichannel synthetic aperture radar (SAR), which deals with azimuth ambiguities, ground moving target indication (GMTI), or interference, degrades severely for hybrid-baseline multichannel SAR. Space-variant interferometric phase, due to terrain elevation and hybrid baseline, destroys the consistency among the Doppler spectrum, which is the foundation of these algorithms. An image-domain signal suppression method designed for hybrid-baseline multichannel SAR is presented in this letter. With prior knowledge about the digital elevation model (DEM), the proposed method recognizes the desired signal on each pixel stack and suppresses others by image-domain digital beamforming (DBF), which gives out a reconstructed image. Signal classification is achieved by pixelwise direction of arrival (DOA) estimation in the image domain. Error in DEM is also considered and analyzed, which guides the signal classification. Simulation with ambiguities and two types of interference are presented, verifying the proposed method.