Pml Absorbing Boundary Conditions In The Waveguide Discontinuity Problems

With the guide of the research group in Microwave tube three-dimensional CAD software "Microwave tube simulator suite", this paper is to research the applications of PML absorption boundary condition in microwave devices. It is important to use appropriate mesh truncation schemes and accurate absorbing boundary conditions on the truncation surfaces to achieve reliable computational results while solving electromagnetic field problems in unbounded regions. Waveguide devices with the medium or structure discontinuity obtain a wide range of applications in a variety of microwave devices, such as phase shifters, power splitters, filters, circulators and so on. Therefore, the paper is to analyze waveguide discontinuity with PML absorption boundary condition.First of all, this paper is to analyze waveguide discontinuity with analytic excitation by using vector finite-element method and PML absorption boundary condition. The computational domain is cut off with PML absorption boundary condition to decrease memory consumption. S parameter is calculated by using mode orthogonality to obtain accurate solution. In the stage of result verification, PML parameter, PML thickness, dielectric discontinuity and structure discontinuity in waveguides are analyzed. According to the comparison with the calculation results from references and HFSS software, the accuracy with the analysis of waveguide discontinuity has been verified by using PML absorption boundary condition of vector finite-element method.This paper is to analyze waveguide discontinuity of various port structures by using mode expansion method with numerical excitation. PML absorption boundary condition is to absorb electromagnetic wave which is caused of non-physical reasons by cutting of computational domain. Numerical excitation in the Waveguide port is implemented by mode field superposition. The coefficient of mode field is normalized mode voltage and mode current. Mode expansion method is the generalized scattering matrix method based on the weak form of Helmholtz equation. The setting method of PML absorption boundary condition parameter is to use the result in analysis of waveguide discontinuity with analytic excitation by using vector finite-element method. In the stage of numerical result verification, it is to calculate two-dimensional intrinsic field of dielectric loaded waveguide and double ridge waveguide. Then, Lossless, lossy and anisotropic dielectric discontinuity in waveguide is analyzed. According to the comparison with the calculation results from HFSS software, the accuracy with the analysis of waveguide discontinuity with various port structures has been verified by using PML absorption boundary condition in the mode expansion method.