The Frequency Scaling Algorithm and interferometric Spotlight SAR processing

Abstract

Synthetic Aperture Radar (SAR) is a well-established technique for air- and spaceborne high resolution imaging. This paper demonstrates the phase preservation of the new Frequency Scaling Algorithm for Spotlight SAR data processing and investigates differences between Stripmap and Spotlight illumination. The algorithm performs the range cell migration correction for non-chirped raw data without interpolation by using a novel frequency scaling operation. The azimuth processing is based on a spectral analysis approach that is made highly accurate by azimuth scaling. In almost all processing stages, a subaperture approach is introduced for efficient azimuth processing. The maximum scene size for air- and spaceborne spotlight parameter examples is estimated. A method is proposed, which shows how to process Stripmap mode raw data in the Spotlight mode. Point target simulations and real raw data processing, including the generation of Spotlight interferograms prove the phase preservation of the Frequency Scaling Algorithm. The same SAR Stripmap raw data set of DLR's airborne system is processed in Stripmap and in Spotlight mode and the resulting detected images and interferograms are compared to each other. The differences due to the different range of squint angles used for the azimuth focusing are discussed.