Application Of Finite Element –Boundary Integral Method In The Microwave Passive Componnents

In order to solve various problems in computational electromagnetic, different numerical simulation methods have been the focus of the study. In numerous numerical methods, the Finite Element Method(FEM) is widely used in solving the problems of radiation and scattering and cavity. In practical applications, many problems of electromagnetic scattering and radiation involve infinite region, then the finite element method need to setting boundary conditions within the appropriate position away from the target, thus result in increasing the amount of calculation. Although the boundary integral method based on integral equation can be directly analyzing these problems, it requires higher requirements for the computer’s memory because it generates a full rank matrix. In order to apply these two numerical simulation methods, develop finite element- boundary integral method. This method introduces a fictitious boundary, using Finite Element Method(FEM) inside the boundary and the boundary integral method outside the boundary, and creates the final matrix according to the continuity of field coupling. The Finite Element Method – Boundary Internal Method has obvious advantages to handle large infinite domain problem, so it is necessary to carry out the research.In this thesis, analysis of the Finite Element Method(FEM) firstly, and deepen the understanding of the Finite Element Method(FEM) through the analysis of the eigenmode of resonant cavity. In the process, through discreting the grid, adding the interpolation function, imposing boundary conditions, storaging sparse matrix and solving the final matrix, get the final eigenvalues. At last, after comparing with exact analytical solution and calculating the error, highlight the advantage of finite element.Then, use the Vector Finite Element Method analysis excited waveguide discontinuity problems through adding absorbing boundary conditions of the first order, and calculate the S-parameters of the waveguide structure. In the phase of verificating results, compare the waveguide cloud with HFSS, and then prepare the basis for proofing the fact that Finite Element–Boundary Internal Method has more precision.Finally, solve S parameters of the waveguide through the Finite Element–Boundary Integral Method. And cut off the front opening of cavity by an imaginary surface, the Finite Element Method(FEM) using in the internal place of the imaginary surface, and Boundary Integral Method in the external. And solve the equation set after two equation sets are coupled. Then get S parameters and compare with the results getted by Finite Element Method(FEM) adding absorbing boundary conditions of the first order. According to the conclusion previously, find out the fact that Finite Element–Boundary Internal Method has more precision than using Finite Element Method(FEM) lonely.