Rigorous network representation of microwave components by the use of indirect mode matching

This paper presents a new method for the analysis of a wide variety of microwave components like posts, circular junctions, or corners in rectangular waveguides. The method gives the impedance or admittance matrix of the microwave component by applying discrimination between the localized and accessible modes in the indirect mode matching (IMM) formulation. In this way, the method is more simple and versatile than previous modeling techniques where IMM is involved, since no use of a Green´s function is required for the coupling between different ports. Furthermore, additional obstacles, like posts at the center of a circular junction, can be considered as different terminations of the corresponding transmission lines. The formulation is given for a two-port as well as a multiport system, and in the present paper numerical demonstration is provided for an abrupt and a step H-plane transition from a rectangular to a radial waveguide, a centrally located H-plane circular post in a rectangular waveguide, and a two-port circular junction between rectangular waveguides. The results are compared with the High Frequency Structure Simulator. In all of the aforementioned cases, the method proved to be fast, very accurate, and easy to implement.