On the Phase Compensation of Short ScanSAR Burst Focused by Long Matched Filter for Interferometric Processing

Scanning synthetic aperture radar (ScanSAR) uses a burst technique to image very large swaths and is widely used in spaceborne SARs. Many algorithms have been proposed to focus ScanSAR burst with its phase preserved so that the focused burst can be used in interferometry to acquire large scale geophysical information, such as land deformation and digital elevation model. However, nearly all of the algorithms leave the focused burst with an additional quadratic phase term that will affect subsequent interferometric processing in the case of short burst. With this phase term, the spectrum of the focused burst is altered according to the principle of stationary phase. Therefore, some processing, such as bandpass filtering, cannot produce desired results if routinely performed. To avoid the effects of the phase term and the nonstationary azimuth spectrum of the burst, a phase compensation scheme is suggested, combining with current focusing algorithms. Simulation experiments are designed to show the effects of the phase term on bandpass filtering. These effects are further verified by a few experiments using real SAR data in unsynchronized signal removal that is frequently required in repeat-pass ScanSAR interferometry. The new phase compensation scheme is tested in real SAR data experiments and works well.