Electromagnetic Characteristic Analysis And Feature Extraction For High-Resolution SAR Targets

With the uninterrupted improvement of SAR resolution, more and more information related to the target's geometry and structure is involved in high-resolution SAR data. Therefore, how to effectively mining these information from high-resolution SAR data for targets recognition and classification has become a problem desired to solve. In this paper, it is studied by two directions: 4D representation based on the time-frequency analysis and the bistatic three-dimensional scattering model method for dihedral, around the issue about electromagnetic characteristic analysis and feature extraction for high-resolution SAR targets.How to analyze the high-resolution SAR data and calculate the target pixel's spectrogram by the way of using the time-frequency analysis method is introduced firstly. Four deal canonical spectrograms are analyzed as well as associated with the actual target structure. Since the complexity of algorithm that analyze the highresolution SAR data based time-frequency analysis is so high, this paper proposes three kinds of optimization algorithm. And the corresponding experimental results show that the proposed algorithm can achieve almost the same as the original algorithm accuracy while computational efficiency has been greatly improved.Secondly, the bistatic three-dimensional scattering model for a rectangular plate centered in the XY plane is derived. And experiments validate the accuracy and efficiency of this model. These support to build bistatic three-dimensional scattering model for complex objects. Therefore, this paper continues to derive a bistatic three-dimensional scattering model for right-angle dihedral. To calculate the dihedral's second-order scattering term, the illumination cases corresponding to the angle of the incident electromagnetic wave are analyzed in detail. And the analysis of completeness are done for the existed six illumination cases. The range of the transmit aspect angle corresponding to each illumination case is also offered. Six sets of experiments corresponding to six illumination cases have been done to verify the correctness of this model.Finally, by introducing internal angle to extend the bistatic three-dimensional scattering model for a right-angle dihedral, a bistatic three-dimensional scattering model for obtuse dihedral is derived. The existence of second-order scattering term and the corresponding illumination case are analyzed first. And then necessary and sufficient conditions corresponding to each illumination case are also given. Experimental results show that the extension model will be back to a bistatic three-dimensional scattering model for a right-angle dihedral when the internal angle is 90o. Experiments validate the correctness and efficiency of this model.