An approximate equivalent-circuit of a truncated nonradiative dielectric waveguide

Nonradiative dielectric waveguides provide the basis for the realization of numerous circuit components. Truncation of the dielectric strip, which is the guiding element of the structure, is a fundamental reactive element of many nonradiative dielectric waveguide circuits, including filters and couplers. The equivalent circuit representation of the truncated nonradiative dielectric waveguide is considered in this article. Variational formulations and dominant-field approximations are used to obtain simple expressions for the terminal reactance and susceptance of the truncation. Accuracy limits of these formulas are determined through comparison with more rigorous calculations and measured data. Related components, such as rectangular resonators and gaps in the nonradiator dielectric waveguide, are also characterized on the basis of the same approach. (C) 1997 John Wiley & Sons, Inc.