Mode-matching analysis of a shielded rectangular dielectric-rod waveguide

Abstract

Rectangular cross-section dielectric waveguides are widely used at millimeter wavelengths. In addition, shielded dielectric resonators having a square cross-section are often used as filter elements, however there is almost no information available on the effect of the shield. Rectangular or square dielectric waveguide is notoriously difficult to analyze, because of the singular behaviour of the fields at the corners. Most published analyses are for materials with a low dielectric constant, and do not include the effects of a shield. This paper describes a numerically efficient mode matching method for the analysis of shielded dielectric rod waveguide, which is applicable to both low and high dielectric constant materials. The effect of the shield on the propagation behaviour is studied. The shield dimensions may be selected such that the shield has a negligible effect, so that results can be compared with free space data. The results are verified by comparison with several sets of published data, and have been confirmed by measurement for a nominal 'e' r of 37.4.