Cascaded Digital Beamforming on Receive With the ROSE-L Multichannel SAR System for Along-Track Deformation Retrieval

The upcoming ROSE-L synthetic aperture radar (SAR) mission employs a large array antenna with multiple azimuth channels on receive, enabling the usage of different beamforming algorithms on ground. Recent analyses have shown the feasibility of retrieving along-track deformation with the ROSE-L system using two-look ScanSAR, however with limited accuracy towards the burst edges due to reduced antenna gain and increased azimuth ambiguities. With beamforming being a state-of-the-art technique to adapt the characteristics of antenna arrays, this letter presents and analyses a cascaded beamforming approach to improve the retrieval performance. It therefore analyses azimuth ambiguities and system noise and their impact on the performance. It is shown that the increased SNR leads to an increased interferometric coherence for scenes with low SNR, thus improving the accuracy of the retrieved along-track deformation in this case.