Study On The Prior Filtering And Oversampling Of INSAR Images

This article begins with the introduction of the spectral characteristics of single look complex (SLC) images and interferogram. After a comprehensive analysis of the geometry decorrelation and the inconsistent focalization of SLC images as well as the aliasing in interferogram, the article puts its emphasis on the prior filtering of azimuth and range spectra, the oversampling and the downsampling of interferogram.The main tasks accomplished are listed as follows:1. The spectral offset which is caused by the geometry decorrelation of master and slave images is discussed, and the basic relationship among which and the base line, the terrain slope is deduced.2. By detecting the maximum of range spectrum the spectral offset is obtained, then the article designs the prior filtering function for range spectral.3. The reason why the Doppler central frequency of the azimuth spectra of spaceborne SAR image is inconsistent and its influence are analyzed, after that the author proposes a way to calculate the central frequency using correlative coefficient. Further more by averaging the spectrum of master and slave image, the influence to interferogram introduced by the inconsistent focalization of original images is eliminated successfully.4. The author makes a study on the possible aliasing in the interferogram's spectrum, and develops a way of oversampling by enlarging the bandwidth of the empty band in original image's spectrum. By this mean the aliasing in the interferogram is removed successfully.5. The relationship between the weighting function of SLC image and the interferogram's spectrum is proved, based on which the author proposes a way to lowpass the interferogram with the help of the convolution of original images' weighting functions. Test results show that this method can not only reduce the size of interferogram but also improve its quality remarkably.6. The prior filtering, oversampling and downsampling theories are tested with ERS satellite images, and the results are analyzed and evaluated.