The Research On Degenerated Modes Decoupling Algorithm In Wideband Characteristic Modes Analysis

After its humble beginnings in the 1970 s,characteristic modes analysis(CMA)has been considered as a key theory of future antenna design and has gained a recent resurgence of interest in the field of antenna design and optimization.Characteristic modes tracking is a necessary process for any serious wideband characteristic mode analysis of structures.However,it is still a challenge to track the modes when their eigenvalues are in close proximity,which leads to a set of degenerated modes whose surface current distributions couple with each other and have a highly unstable evolution.In this thesis,a decoupling method with high decoupling performance for arbitrary dimensional degenerated modes has been proposed through the application of eigenspace decomposition theory and Givens Rotations model in wideband characteristic modes tracking algorithm,and the problem of degenerated modes has been solved.This thesis is organized in four parts as follows.The first chapter is the overview chapter.The second chapter is about the background knowledge and theory of degenerated modes.The detailed introduction of proposed decoupling method is presented in the third chapter.From the two dimensional case,through the application of Givens Rotations model in wideband characteristic modes tracking,the decoupling method is generalized into the arbitrary dimensional cases,and the decoupling problem is transferred into an optimization problem,which is accomplished by gradient descent method and backtracking line search.Furthermore,an automated decoupling control system with high accuracy is demonstrated.In the last chapter,the performance of modal assurance criterion method with decoupling function is analyzed in detail,including the decoupling performance in the decoupling frequency band with narrow frequency step,the wideband decoupling performance with normal frequency step and the robustness on meshes.The unique advantages of the proposed wideband characteristic modes tracking algorithm with arbitrary dimensional degenerated modes decoupling function include: applicability for degenerated modes decoupling in arbitrary dimension for arbitrary conducting structures,perfect decoupling results,fast computation,robustness to different meshes of the same object,and high portability.