Chirp Z-Transform Based SPECAN Approach for Phase-Preserving ScanSAR Image Generation

The scan mode synthetic aperture radar (ScanSAR) image impulse response is derived in the time domain, and particular attention is given to the analysis of the phase, which is important for several applications, and especially in interferometric ScanSAR systems. A new algorithm for phase-preserving azimuth focusing of ScanSAR data, that extends the basic SPECAN procedure, is presented. The proposed algorithm avoids the interpolation step needed to achieve constant azimuth pixel spacing by replacing the standard Fourier transform used in the SPECAN procedure with an appropriate chirp z-transform. The relationship between the modified SPECAN algorithm and the standard range-Doppler approach is also discussed. Experiments on real and simulated data are carried out to validate the theory.