Effects of Wall Perturbations on TM Modes in Arbitrarily-Shaped Cylindrical Wave Guides

It is shown that any reduction in cross-sectional area of an arbitrarily-shaped homogeneously-filled cylindrical wave guide must increase the cutoff frequency of the TM (transverse magnetic) modes. This result is proven mathematically and is demonstrated by comparing data for rectangular, circular, polygonal, and ridge conducting wave guides. This result is not true for all TE (transverse electric) modes. This result can be useful for waveguide component design