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IEEE Transactions on Microwave Theory and Techniques
Volume 48 Number 10, October 2000

Table of Contents for this issue

Complete paper in PDF format

Determination of Simple Equivalent Circuits of Interacting Discontinuities in Waveguides or Transmission Lines

Ralph Levy Life Fellow, IEEE

Page 1712.

Abstract:

It is well known that the generalized scattering matrix (GSM) of a microwave network, which includes one or more ports supporting evanescent modes, is nonunitary. This has hindered the formation of equivalent circuits since it has not been evident how to form the impedance or admittance matrix. This paper describes how the problem has been overcome, resulting in a method for the formation of simple equivalent circuits of interacting closely spaced discontinuities in a waveguide. The N-port immittance matrix corresponding to the nonunitary GSM is formed by normalizing the immittance matrix to real or imaginary portal impedances. As an example,an equivalent circuit for the even mode of a waveguide short-slot coupler is presented, and the effect of the evanescent TE30 mode in the coupling region is clearly expressed by an evanescent-mode waveguide in parallel with one supporting the dominant propagating mode. The method should find wide applications to problems involving interactions in waveguides.

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