E-SAR Upgrade to Stepped-Frequency Mode: System Description and Data Processing Approach

Abstract

A common way to enhance the range resolution of imaging radars is to adopt stepped frequency waveforms. This paper discusses in detail stepped-frequency processing possibilities on raw and processed data level, focussing on the compensation steps required to obtain high quality results. At the same time, software changes to an established SAR processor are kept at a minimum. The paper starts with a description of associated hardware extensions performed to the front-end of the E-SAR system of DLR to accommodate the stepped frequency mode in X-band. Two alternating channels, each of 100 MHz bandwidth have been implemented, which lead to a best case range resolution of 80cm corresponding to an improvement of up to 80% compared to the standard imaging mode. The performance of the complete system (including hardware and processing concept) is investigated using real data acquired with different spectral overlap between the sub-bands.