The Extraction For Effective Electromagnetic Parameters Of Inhomogeneous Metamaterial Structures

Metamaterial has been a famous research area in electromagnetics and material science in recent years. Reseachers in the worldwide are interested in the unusual electromagnetic properties of metamaterials and these novel structures can be potentially applied in communication, areospace and electromagnetic compatibility. As an important research branch, the extraction method of effective electromagnetic parameters for metamaterials provides a simple and convenient way to represent the metamaterial according to effective medium theory. In this thesis, the accurate and efficitent methods of retrieving effective electromagnetic parameters for metamaterial were studied, especially for asymmetric metamaterial structures. The contents in this thesis include following several parts:First, the overview of metamaterial was described in brief, and their unusual electromagnetic properties were introduced, including negative refraction, negative group velocity, reversal Dopplor shift, reversal Cherenkov radiation,, reversal Goos-H?nchen shift, cloak, etc.Then, the metamaterials with negative permittivity, negative permeability, and both of negative permittivity and permeability were discussed in detail, respectively. Specifically, the structure with negative permittivity was designed by period metal wire array; the structure with negative permeability was designed by period metallic cylinders with “split ring”; and the effective procedure of electromagnetic parameters was deduced.In the following, methods to extract the effetictive parameters of symmetry metamaterials structure using scattering parameters was introduced. Firstly, The Smith method based on transmission matrix was used to obtain the effective electromagnetic parameters of SRR-Wire structure. Then, A method based on Kramers-Kronig relationship was discussed. Finally, An extracted method using unwrapping technology was derived to extract the effective electromagnetic parameters for multiple SRR-Wire layers with high efficiency.Next, an extraction method was developed for two-layer asymmetry metamaterial structures and three type of models including medium-medium model, medium-structure model and structure-structure model were used to validate the proposed method. And an error analysis caused by iterations in the proposed method was given. As an alternative solution way, a solution function called fsolve in Matlab was used to obtain the effective electromagnetic parameters and the numerical examples are given to show the feasibility of the proposed method.Finally, the methods using recursion of scattering parameters and electromagnetic fields respectively were developed to obtain the effective electromagnetic parameters for multilayer asymmetry metamaterial structures. A function named fsolve in Matlab was used to solve the effective electromagnetic parameters and feasibility was verified by some numerical examples.