Multichannel Staggered SAR for High-Resolution Wide-Swath Imaging

Abstract

In the context of state-of-the-art and next-generation spaceborne Synthetic Aperture Radar (SAR) imaging systems, such as the German Tandem-L mission proposal, a short revisit time coupled with high resolution presents itself as a requirement for the observation of numerous Earth dynamic processes in various scientific and environmental applications. This poses contradicting and demanding requirements on system design for whose realization digital beamforming techniques play a crucial role, in order to enable next-generation systems to significantly outperform current state-of-the-art systems and fulfil the increasingly stringent needs of applications. Multichannel SAR systems with digital beamforming in azimuth have been proposed as an option for coping with these challenging requirements in order to achieve high-resolution wide-swath (HRWS) imaging capabilities. These systems tend however to require a very long antenna to image wide swaths. As an alternative, the use of digital beamforming in elevation, in conjunction with a varying pulse repetition interval (PRI) for the SAR system radar pulses (Staggered SAR), has been proposed. The best azimuth resolution in this case is nevertheless limited by the antenna dimensions. The thesis focuses on the development of new SAR techniques and corresponding processing methodologies which allow the combination of the advantages of the multichannel system architectures in azimuth with those of staggered SAR. This introduces new and potentially highly flexible modes of operation, enabling HRWS imaging with a compact antenna and contributing to the new developments in the field of digital beamforming techniques. The thesis includes the proposal of novel algorithms for the resampling of multichannel staggered SAR data and examples of high-performance HRWS systems designed to make use of the technique. In addition, a proof-of-concept with experimental data from a ground-based radar system and a discussion of the possible effects of errors for the implementation of this new class of spaceborne imaging systems are presented.