Research On Key Technique For Interferometric Synthetic Aperture Radar Measurement

The Interferometric synthetic aperture radar (InSAR) is a new radar imagingtechnology that based on synthetic aperture radar (SAR). InSAR can obtain the heightof the targts from phase differences of the two synthetic aperture radar (SAR) images,and it can get digital elevation model (DEM) of the nominated target in all weather andall time effectively. In military, the construction of national economy and scientificresearch field, InSAR has a wide range of applications, thus the research of the InSARhas been highly regarded both here and abroad.The interference imaging technology of spaceborne-InSAR as the research objectdeveloped here, the development of the InSAR technology, applications and InSARImaging principle are introduced, each step in interference imaging technology of theInSAR have been researched deeply.Since the differences of measured phase is wrapped into (-π,π], the phaseunwrapping is a key steps in interference synthetic aperture radar(InSAR) signalprocessing. However, since the presence of different error such as noise or undersampled, the real phase cannot be retrieved straightforwardly, there need to developphase unwrapping algorithms to deal with this problem. So in this thesis phaseunwrapping problem is developed, and to improve the utilization of Interferometric dataand the precision of DEM, multiple baseline InSAR phase unwrapping technique isdiscussed that based on single baseline phase unwrapping. The content of the thesis is asfollows:1. How to establish branch-cut is very important to Path following method, the shorterthe length of the branch-cut, the better the result of phase unwrapping. Therefore, theimproved genetic algorithms for optimizing the length of the branch-cut is presentedbased on Goldstein algorithm, which has already been successfully applied to find theshortest path in the traveling salesman problem (TSP) theory. The method can minimizethe length of the branch-cut and avoid the "isolated island phenomenon" of unwrappingprocess effectively, and the precision of the phase unwrapping has been improved inhigh residue regions.2. The global method of phase unwrapping developed here, a robust method forunwrapping2D phase by using mesh-less method under least-squares theory isproposed. Mesh-less function is obtained by radial point interpolation method and phaseunwrapping process is implemented by estimating the local optimal approximate value under an efficient least-squares solution. As the proposed method takes advantage bothfrom least-squares and mesh-less method, it cannot only unwrap the unreliable areascorrectly, but also can forbid error accumulate to the whole image.3. A hybrid phase unwrapping method that combines the quality guided method andB-spline surface-fitting method is proposed in this thesis. The proposed method utilizesdifferent methods at different quality regions to realize the phase unwrapping, it usesquality guided method to unwrap the phases in high quality regions, and uses B-splinesurface-fitting method to obtain the surface of the unwrapped phase in low qualityregions. The wrapped phase can be unwrapped from high quality region to low qualityregion which can reduce the error accumulate and improve the robustness of phaseunwrapping.4. Multi-Baseline InSAR is expand of the tradition Single-SAR, according to therelationship of the long and the short baseline, the wrapped phase can be unwrappedsimply. The Multi-Baseline InSAR developed here, and a phase unwrapping methodbased on a generalized robust Chinese Remainder Theorem is proposed with detailderivation, this method can use the relationship of the long and the short baseline toobtain the nterferometric phase, realize the phase unwrapping by solving the congruenceequation. The impact of the phase noise to the unwrapping was analyzed; the range ofthe maximum tolerable phase noise resolve the correct ambiguity was given.