Trapped Mode Phenomena in a Weakly Overmoded Waveguiding Structure of Rectangular Cross Section

Authors: Soekmadji, H.; Liao, S.L.; Vernon, R.J.

Source: Journal of Electromagnetic Waves and Applications, Volume 22, Number 1, 2008 , pp. 143-157(15)

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Abstract:

A general formula of the transmission coefficient derived from the Scattering Matrix Method (SMM) for reciprocal, lossless or lossy trapped mode structures is presented. Verifications of the theory by means of experiment and computer simulations (HFSS and Cascade) of the transmission coefficient are also presented. The rectangular cross section waveguide structure we considered consists of an uptaper, a straight uniform section, and a downtaper. The dominant TE₁₀ mode can propagate through the structure whereas the TE₃₀ mode is trapped within the center region of the structure. It is also shown that our formula reduces to that given by King and Marcatili for the reciprocal and lossless case. The first five resonant frequencies and the transmission coefficient for the trapped mode structure have been calculated and compared to the results from the experiment and the computer simulations. At the resonant frequencies of the trapped mode, the transmitted power of the dominant TE₁₀ mode may be reduced significantly, depending on the ohmic wall loss as well as the integrated coupling between the TE₁₀ mode and the trapped TE₃₀ mode. The effects of various waveguide aperture misalignments on the transmission coefficient are also discussed in this paper.

Document Type: Research article

DOI: http://dx.doi.org/10.1163/156939308783122706

Affiliations: 1: Department of Electrical and Computer Engineering, University of Wisconsin, Madison 1415 Engineering Drive, Madison, Wisconsin 53706, USA

Publication date: 2008-01-01