Computer-aided design of passive microwave components nonstandard rectangular waveguide technology.

摘要

Continued advancement in microwave telecommunications generates an ever increasing need for the further development of computer-aided analysis and design tools. The objective of this thesis is to develop computer-aided design algorithms for the construction of original and innovative components in an all-metal nonstandard rectangular waveguide technology, and to do so employing accurate electromagnetic field analysis. Nevertheless, the principles derived from this relatively narrow field of research are applicable to other waveguide technologies.;Through the examination of a variety of ways to accomplish this, a mode matching method is found best suited to this purpose. A building block approach, involving the separate analysis of smaller discrete discontinuities leading to the cascading and combining of them through the Generalized S-matrix Method, is selected as having the greatest potential for universal application. Two nonstandard discontinuities are selected for further pursuit: as an example of two-port discontinuities, the T-septum waveguide; and, as an example of multi-ports, the discontinuity-distorted T-junction. To facilitate the discussion of these nonstandard discontinuities, mode-matching is reviewed by solving a double-plane step and a simple E-plane T-Junction.;The first objective, when applying mode-matching to nonstandard rectangular waveguide discontinuities, is to determine the propagation characteristics or eigenmodes of each subregion of the discontinuity. The standing wave formulation in conjunction with a minimum singular value decomposition algorithm is employed to determine the cut-off frequencies of a T-septum waveguide. The results are them employed in the application of mode-matching to a rectangular-to-T-septum waveguide discontinuity. The discontinuity is shown to be advantageous in the design of evanescent-mode filters, transformers, and diplexers. Two prototypes, a bandpass filter and a diplexer, were built and tested. With the exception of poor insertion loss performance attributable an unanticipated poor level of conductivity in material coupled with an additional loss resulting from the abrupt conjunction of the miniaturized T-septum filter segments with the larger input/output waveguides, the measurements compared well to calculated responses.;The theoretical and numerical analysis of nonstandard two-port theory is expanded to include multi-ports. The formulation produces the generalized scattering matrix of a discontinuity-distorted T-junction by applying superposition to the non-homogeneous boundary conditions toward a solution of the Helmholtz equation in determining the eigenmodes of the resonator region. The waveguide corner, being a special case of the T-junction, is used to demonstrate the accuracy of the formulation through its high level of agreement with known measurements and calculated results of mitered 90;The formulations presented in this thesis have proven to be accurate and successful in all of the applications presented here and promise to be of substantial benefit in the area of component design in the future.