Mode-Matching Analysis Of Microwave Waveguide Components

The modal analysis method is an accurate and efficient full-wave method based the field theories. The numerical efficiency of this method allows the advanced sophisticated synthesis procedures with the advanced optimization algorithms and the computer aided design of the waveguide circuits even the other microwave or millimeter-wave circuits performed on personal computer. The utilization of the modal analysis in computer aided analysis (CAA) of microwave and millimeter-wave waveguide passive circuits is studied in this dissertation.Generalized admittance matrix (GAM) and its characterization, cascading and computing are studied. The multimode network representations for a series of waveguide discontinuities are described in terms of generalized admittance multimode matrices. Another multimode network representation: generalized scattering matrix formulation is also introduced.We studied the multimode coupling matrix of the key waveguide discontinuity, waveguide step, with the modal fields expansions in waveguides. And obtained the relations with the multimode coupling matrix, the generalized admittance matrices and the generalized scattering matrices. We have compiled some subroutines in Fortran 95 programming language to compute the multimode coupling matrix, admittance matrices, scattering matrices and their operates with each other.Five programs have been developed with the subroutines mentioned above. These programs are used to analyze rectangular waveguide inductive iris filters, rectangular waveguide E-plane metal-insert filters, H-plane rectangular waveguide right corners, H-plane rectangular waveguide T-junctions and waveguide diplexers, respectively. Comparisons between these analysis results and the data of reference or simulations by the commercial software package, Ansoft HFSS, are presented, indicating the approach proposed accurate and computationally very efficient and the computer programs all right. The convergent properties of the multimode method are discussed.Finally a diplexer employing H-plane T-junction and preassigned E-plane metal-insert branching filters is given. And the scattering parameters of the un-optimized diplexer were obtained by the computer program.