The Study Of Channel Errors Calibration And Clutter Cancellation Based On Low-frequency Multi-channel SAR/GMTI System

Ground moving target detection with airborne SAR plays an important role in the martial field . This dissertation focuses on two key techniques , i.e. error correction of channels and ground clutter suppression , which are practical problems to be solved for SAR/GMTI. The major work is as follows:First , several airborne SAR/GMTI systems are introduced .Then the study status of SAR/GMTI is reviewed and the difference between Low-frequency SAR and High-Band SAR systems as well as the major work are also specified.After the modeling of moving targets'echoes , the motion-induced changes of Doppler frequency and range cell migration(RCM) are discussed in detail ,together with their impact for SAR image data. It's also analyzed and simulated what influences the changes have on the conventional SAR imaging.The next part analyses a variety of SAR error sources and their impact on imaging data in practical application, presents a complex image registration error correction method based on clutter correlation coefficients an a gain-phase error calibration method based on largest eigenvalue eigenvector . It's proved to be feasible and effective for measured data.As for the existence of interference in measured data of ATI, this paper analyzes its formation and the impact on ATI, and demonstrates the interference by exhibiting the interfergram. According to statistical features of ATI phase, two cases are discussed. We estimate and search the amplitude and phase values of the interference from statistical ATI data, and then suppress this interference. This method is verified to be effective and accurate for estimating and searching the best amplitude and phase values by measured data experiments.The most commonly used method of clutter suppression in practice , the DPCA method , is briefly introduced as well as its disadvantages. Combined with the idea of space-time adaptive processing in image domain , this dissertation deduces the signal expression of moving target , proposes the spatial steering vector of moving targets for united pixel adaptive processing method .At last , experimental simulation verifies that the united pixel adaptive processing method is more effective than the DPCA method in clutter suppression , while measured data proves that this method is effective in engineering practice.