A New Analytical Method for Calculating the Cutoff Frequencies of an Eccentrically Dielectric-Loaded Circular Waveguide

This letter provides an analytical method to calculate the cutoff frequencies and waveguide modes of conducting circular waveguide eccentrically loaded with a dielectric material based on bipolar coordinate system (BCS). A circular waveguide partially filled with an eccentric dielectric cylinder supports hybrid electric (HE) and hybrid magnetic (EH) modes with nonzero longitudinal electric and magnetic fields, respectively. The cutoff frequencies of the HE and EH modes have been calculated and compared to benchmark results. An analytical expression for the electromagnetic fields has been also proposed and the validity range of the solution has been discussed. An excellent agreement between the calculated cutoff frequencies with those obtained by more rigorous numerical methods has been observed. Our analytical method provides better physical intuition and is fast, accurate, and easy to implement.