Location and imaging of elevated moving target using multi-frequency velocity SAR with cross-track interferometry

Synthetic aperture radar (SAR) location and imaging of moving targets in clutter have attracted much attention in recent years. Locations of moving targets in SAR images are determined not only by their geometric locations but also by their velocities that cause their SAR images de-focused, smeared, and mis-located. With a linear antenna array, velocity synthetic aperture radar (VSAR) can detect, focus, and locate slowly moving targets well. However, it may mis-locate fast moving targets in the azimuth (cross-range) direction, and sometimes even in the ground range direction if the targets are elevated above the ground. Although multiple frequency antenna array SAR (MFAASAR for short) can solve the azimuth mis-location, it still leaves the ground range migration of elevated targets unsolved. We propose an antenna array approach with cross-track interferometry, in which multiple wavelength signals are transmitted. We then propose a robust Chinese remainder theorem (CRT) based phase unwrapping algorithm. The proposed robust CRT-based phase unwrapping algorithm is robust to signal noise, which is different from the the conventional CRT-based phase unwrapping algorithm that is highly sensitive to signal noise and nonrobust. It is shown that our proposed multiple frequency interferometric velocity SAR (MFIn-VSAR) by applying our proposed robust phase unwrapping algorithm can locate both slowly and fast moving elevated targets correctly. An integrated MFIn-VSAR algorithm for moving target imaging is also presented.