Research Of Characteristic Mode Theory And Its Fast Algorithm

The characteristic mode theory has received extensive attention since it was put forward.Because the characteristic mode theory does not consider external excitation,but only considers the inherent attributes of the target object,such as the structure,size and position of the target object,it is very suitable for antenna design and target electromagnetic scattering characteristic analysis.The characteristic mode theory not only retains the advantage of the clear physical concept of the traditional eigenmode,but also combined with the Method of Moment in the electromagnetic numerical calculation method,it can deal with the targets with irregular shapes.The characteristic mode theory divides the object surface current into real mode currents.According to the eigenvalue,each mode can be divided into different states.This paper mainly studies the application of characteristic mode method in target radar scattering problem.Firstly,the electric field integral equation derived from scattering problem is solved by moment method.The induced current is caused by incident wave,which can be weighted by RWG basis function,and the impedance matrix is discretized by Method of Moment.Then take out the real part matrix and imaginary part matrix of the impedance matrix to construct the weighted generalized eigenvalue equation,and then solve the generalized eigenvalue equation to obtain the eigenvalue and characteristic current.At the same time,the calculation of characteristic mode parameters such as mode weighting coefficient and characteristic angle is studied.Then,how to calculate and analyze the radar cross section of electromagnetic scattering based on the characteristic mode theory is studied.According to the orthogonal characteristic currents under different modes obtained by solving the generalized eigenvalue equation,it is used as the basis function to expand the real surface current.After recovering the real surface current,the radar cross section parameters can be effectively extracted.The schematic diagrams of characteristic current,characteristic far field and characteristic value of target simulation model are given.In addition,a fast algorithm for solving the generalized eigenvalue equation in eigenmode theory-implicit restart Arnoldi algorithm is studied.Because the impedance matrix obtained by the discrete integral operator of the method of moments is a dense matrix,the computational resources consumed in calculating the generalized eigenvalue equation are very high,and it is difficult to analyze large-scale problems.Implicit restart Arnoldi algorithm reduces the time and memory requirements of solving eigenvalue equations by using iterative operation,but it still consumes a lot of computer resources because it deals with dense matrices.In this regard,the adaptive cross approximation algorithm is introduced to sparse the dense matrix by using the low rank property of the matrix,which greatly alleviates the requirements of computing time and memory.Finally,through the analysis of electromagnetic scattering characteristics of different targets,the correctness and effectiveness of the method studied in this paper are verified.