Modal solutions in dual-depth longitudinally corrugated hard waveguide

A longitudinally corrugated circular waveguide with dielectric-filled grooves of alternating depths is considered. The dispersion equation for determining the waveguide eigenmode parameters is derived for the small corrugation period. The waveguide is shown to support two quasi-transversal electromagnetic (TEM) modes, associated with each of the two frequencies at which the TEM condition is realised. Some features of these quasi-TEM modes are revealed. The potential performance of a dual-band conical horn is presented, and some future studies are discussed here.