Multiple-view Radar Imaging Enhancement Technology

Resolution is a key performance indicator in radar imaging.We usually enhance range resolution by broadening signal bandwidth and improve azimuth resolution through widening aperture.Synthetic aperture radar(SAR)is widely employed on account of its superior performance in obtaining large aperture,which is also called wideangle/multiple-view imaging.Circular SAR(CSAR)is one of the most important platform for multiple-view imaging due to its omni-directional target detection and high resolution.The main problem of multiple-view imaging is the dependence of scattering behavior on azimuth angle,termed anisotropy.The anisotropic scattering information is mapped on the 2D image during the imaging procedure,which degrades imaging quality and causes information loss.Therefore,it is necessary to extract anisotropic scattering information for further analysis,fusion,and finally enhance imaging.The anisotropic feature extraction methods are classified into parametric and nonparametric methods.Nonparametric methods are more often applied and easier to realize.Subaperture method is a classic nonparametric method which causes low resolution at the same time.Image Fusion is an approach of enhancing imaging after obtaining the azimuthal image.Sparse decomposition is widely used in signal and image processing because it could characterize a signal with a few feature parameters.Utilizing these parameters to research targets is another method of enhancing imaging.In order to realize the above two methods,the major work is embodied as following four aspects:Firstly,an anisotropic feature extraction method based on space-wavenumber distribution is proposed,which acquires higher image resolution than subaperture method;Secondly,three criterions of SAR image fusion based on pixel level are proposed,and the results of measured data validate its efficiency;Thirdly,aiming at the low efficiency of matching pursuit algorithm in sparse decomposition,an improved matching pursuit algorithm based on classification and quadratic search is proposed;Finally,the feature parameters of the target are extracted by sparse decomposition,which is used to decompose the target and achieve the purpose of enhancing imaging.