Vector Finite Element Method S-parameters Of Microwave Multiport Network

Microwave wave tub is one of the most important equipments, which is one kind of high power, high gain and broad-band microwave millimeter wave amplifiers. They are widely used in communication, radar system and electronic warfare, taking an irreplaceable role in modern military electronic equipments and communication. The subject of "CAD technology research of Wide Band Power TWT" is independently put forward by China which is a long-term high-technology subject. "CAD technology research of Wide Band Power TWT" is the key step from the design to manufacture for TWT. In 2003, the UESTC took in hand the research of the five most important modules including UESTC_Gun module, UESTC_Helix module, UESTC_BWT module, UESTC_MDC module and UESTC_fPPM module. With the guide of the research group in "CAD technology research of Wide Band Power TWT", the paper did some research in the S parameter and eigenvalue simulation which based on vector finite element method. The goal is to achieve arbitrary cross-section multi-port network S parameters simulation.Chapter I briefly introduced the development of microwave tube CAD and application of finite element in microwave CAD.Chapter II introduced the vector finite element method theory and the simulation of the arbitrary shaped waveguide filled with anisotropic dielectric and the calculation of the three-dimensional resonant cavity eigenvalue. The latter part of the chapter describes the perfectly matched anisotropic layer which is assumed to realize the unlimited boundary cut-off. Finally, this chapter described the wave port boundary condition which is widely used in S parameter simulation.Chapter III analyzed the weak form of Helmholtz equation and the port mode match method in S parameter simulation which contains the Galerkin weighted residual method, the generalized scattering matrix method and the Jin-Fa Lee method. Latter parts of this chapter introduced the GSM formulation discretization.Chapter IV briefly introduced meshing, edge labeling and matrix solving.Chapter V emphasized on the analysis of the results about the algorithms which includes two-dimension and three-dimension eigenvalue computation module and S parameters computation module. In the two-dimension eigenvalue problems, the propagation constant, the dispersion and the electromagnetic field distribution of different modes in waveguide were calculated and analyzed in different mesh density. Also, the eigen frequency of trough structure resonant cavity and anisotropic media loaded resonant cavity was calculated. In the S parameters computation module, generalized scattering matrix method was used. Through the computation of the normalized admittance matrix with the normalized voltage and the normalized current, the microwave network S-parameter matrix can be got easily. According to the comparison with the calculation result from HFSS, the accuracy of such algorithms mentioned in this paper has been verified.Chapter VI summarized and concluded the whole dissertation. Further research issues and possible research directions were pointed out.