ISAR Imaging Method Based On Parametric Analysis Of Targets Electromagnetic Scattering Characteristic

Inverse Synthetic Aperture Radar(ISAR)imaging technology has been widely used in military and civilian fields thanks to its capacity of full-day,all-weather and far-acting distance observation and high-resolution imaging.ISAR imaging is the process of reconstructing and inverting the structure and electromagnetic scattering characteristics of the target.Therefore,the research on the target electromagnetic scattering characteristic analysis and modeling method is a hot issue in ISAR imaging field.The traditional ISAR imaging is usually based on the point scattering model.Although the model is simple,it is difficult to accurately describe the anisotropy and frequency dependence of the scattering center,and there is a large limitation in the practical application.However,the attribute scattering center model is more accurate for the electromagnetic scattering description.Therefore,this paper will concentrate on the extracting of attribute scattering centers and three-dimensional geometry reconstruction method in ISAR images under different scenes.The main work of this paper is as follows: 1.We introduce several commonly used target electromagnetic scattering parameter models and analyze the relationship between them.The basic principles of ISAR imaging are introduced,including the turntable model of ISAR imaging,and the common methods of envelope alignment and phase correction in translational motion compensation.2.The method of extracting the attribute scattering center in ISAR image is studied.To tackle with the difficulty in estimating rich parameters of attributed scattering centers,we introduce the estimation methods based on the image segmentation and Orthogonal Matching Pursuit(OMP),respectively.Then,the characteristics of different methods are analyzed.The experimental results of simulation data and the MSTAR data validate the effectiveness of the above two methods.3.Aiming at high computation burden of the attributed scattering centers extraction and the fact that ISAR echoes are not continuous in the sparse frequency band or observation angle,novel attribute scattering center extraction and ISAR imaging methods based on compressed sensing are studied.Firstly,the principle of compressed sensing is introduced,as well as the mathematical model of compressed sensing,the design of observation matrix and the reconstruction methods.Then,based on the characteristics of ISAR echoes,the dictionary matrix and the observation matrix are constructed.The parameters of the attribute scattering center are estimated by OMP method,and the target ISAR image is reconstructed by using the estimated attribute scattering center parameters.Finally,the validity of this method is verified by the experimental results.4.Aiming at the problem that the three-dimensional ISAR imaging method based on point scattering model cannot accurately reconstruct the three-dimensional structure of the target,the three-dimensional ISAR imaging technique based on attribute scattering center is studied.Firstly,the three-dimensional ISAR observation and imaging model is introduced,and the projection relationship between the target three-dimensional position and the two-dimensional positions of the scattering centers is analyzed,and the three-dimensional attribute scattering center model is constructed.Then,the trajectory association method of attributed scattering centers is proposed by using the rich parameters of attribute scattering center.Then we study the reconstruction methods of three-dimensional position with and without prior radar observation angle respectively.Finally,The 3D position,length,orientation angle and frequency dependence factor of the scattering center are obtained by combining the extracted two-dimensional scattering center parameters to realize 3D ISAR imaging.The experimental results show the effectiveness of the proposed method.