Deramp Chirp Scaling algorithm for high-resolution spaceborne spotlight SAR imaging

Based on Two-Step processing approach and Chirp Scaling algorithm, a Deramp Chirp Scaling (DCS) algorithm for high-resolution spaceborne spotlight synthetic aperture radar (SAR) imaging was presented. The algorithm combined the advantages of SPECAN algorithm and Chirp Scaling algorithm. Firstly, the azimuthal coarse focusing was achieved via a deramp processing with constant Doppler rate, and the azimuthal spectral folding phenomenon, which was typical for spaceborne spotlight SAR, was overcome. Secondly, the precise range focusing was achieved by Chirp Scaling principle, and the residual azimuth phase error was compensated, so the refined azimuthal focusing was acquired. Based on the squinted equivalent range model that was fitter for spaceborne geometrical relation than the broadside range model, the complete derivation of the algorithm was presented and the realizing approach was given. The whole algorithm could be implemented by complex multiplication and fast Fourier transform (FFT) without any interpolation of the data. The algorithm was suitable for wide range swath high-resolution spaceborne spotlight SAR imaging. Finally, the computer simulation showed the validity of the algorithm.