Characteristics of quad-ridged coaxial waveguides for dual-band horn applications

Circular coaxial quad-ridged waveguides find application in the design of broadband diplexers for the dielectrically loaded, ultrawide dual-band horn. The three basic structures where the four ridges are placed symmetrically on the inner conductor, on the outer conductor or on both conductors of the coaxial waveguide, are analysed using a modified Ritz-Galerkin method. To find the optimum configuration, the cutoff wavenumbers of the first two (effective) dominant modes for each of these structures, from which we deduce the bandwidth characteristics, are calculated and compared. The aim is to obtain the preferred coaxial ridged structure in terms of broad bandwidth and ease of fabrication