Research And Application Of Integral Equation Broadband Electromagnetic Scattering Calculation Method

Broadband electromagnetic scattering of targets plays an important role in identification,tracking and imaging applications.The traditional integral equation methods,such as the method of moment,the multilevel fast multipole algorithm,and the popular fast direct solution method in recent years,can accurately calculate the electromagnetic scattering of targets,but these calculations are limited to a single frequency.For the broadband electromagnetic scattering problem that needs to solve multiple frequency points,it can only be done one by one,which makes the fast algorithm very inefficient in broadband caluation.In this thesis,the best uniform approximation method is used for the broadband calculation.Contrast with the common broadband methods,such as the model-based parameter estimation method and the asymptotic waveform evaluation method,the best uniform approximation method based on the Chebyshev interpolation polynomial does not need to store the reduced-order matrix,and the selection of sampling points is also very simple,so it has been widely used in the broadband caluation.In addition,the best uniform approximation method can be easily combined with various fast algorithms,which can improve the broadband scattering caluation capability of electrically large targets.Firstly,this thesis studys methods for solving broadband electromagnetic scattering based on the method of moment.The asymptotic waveform evaluation method and model-based parameter estimation method are introduced,and their characteristics are analysed.Then,the solution principle of the best uniform approximation method is introduced in detail,the solution process is briefly described,and the three broadband methods are compared to analyze their ability to calculate complex targets.Then,the best uniform approximation method and the method of moment are combined for broadband calculation,and the ability of this method to calculate the broadband scattering of metal targets is verified.Then,to expand the broadband calculation ability,the multilevel fast multipole algorithm and the best uniform approximation method are combined.The basic principle of the multilevel fast multipole algorithm is introduced.The numerical calculation process after combining the best uniform approximation method is described.The numerical examples of metal targets are used to verify the effect of this method in calculating the broadband scattering of electrically large targets.Finally,the best uniform approximation method is introduced into the strong admissibility skeletonization factorization method,which realizes the fast calculation of the wideband and wide-angle scattering problem.The principle of the strong admissibility skeletonization factorization method is introduced.The horizontal and longitudinal processes in the wideband and wide-angle scattering calculation are described in detail,and the main points of these two processes are introduced.Through several numerical examples of metal targets,the effectiveness of this method for calculating wideband and wide-angle scattering is verified.