A Full-Aperture Frequency Scaling Algorithm for Processing Dechirped Sliding Spotlight SAR Data

This paper proposes a full-aperture method for processing sliding spotlight synthetic aperture radar (SAR) data with dechirp-on-receive. The frequency scaling algorithm (FSA) efficiently processes the dechirped signals because the range cell migration correction (RCMC) process involves removing the residual video phase. However, the conventional FSA combined with the sub-aperture method is unsuitable for processing sliding mode data because the azimuth extent of the SAR image is limited by the system pulse repetition frequency. In addition, the azimuth compression performance deteriorates as the range displacement increases from the center of the SAR image. To address these problems, we developed a modified full-aperture FSA for sliding mode data processing. A complete signal model of the azimuth convoluted sliding mode data with the dechirp-on-receive is newly derived. Based on the signal model, the frequency scaling factor and azimuth-matched filter have been modified to accurately perform RCMC and azimuth compression. Point target simulations demonstrated two advantages of the proposed algorithm over the conventional sub-aperture approach; One is accurate and consistent azimuth compression performance regardless of range displacements, and the other is wide observable azimuth extent. The practicality of the proposed method is further verified through actual SAR raw data experiments. In addition, it is analyzed that the proposed algorithm is specialized in processing dechirped sliding mode data through a characteristic comparison with various traditional sliding spotlight processing methods.