Chinese Remainder Theorem Based Phase Unwrapping Integrated with Ground Distance Matching for Multi-Baseline Radar Altimeter

The radar altimeter is an important aviation device for aircraft to obtain ground altitude information. Comparing with single radar altimeter, multi-baseline (MB) radar altimeter has adaptable capability for achieving large range observation with high accuracy which presents significant potential in various applications. However, for the compacted-size platform applications, the limited length of baseline causes small phase differences among complex radar images and the current Chinese remainder theorem (CRT) phase unwrapping (PU) algorithms are highly sensitive to the noise. To address this problem, an improved CRTbased PU integrated with ground distance matching (GDM) is proposed for MB radar altimeter, which is referred to as CRTGDM. By exploring the phase property of MB radar altimeter, CRT-GDM introduces ground distance conditions on the basis of CRT and constrains the phase folding integer into a small searching interval, which can dramatically reduce the noise effects and significantly improve the accuracy and the robustness of CRT algorithm in small length baseline applications. Both multi-point and surface-point simulations are conducted and analyzed to validate the high performance of the proposed algorithm.