Experimental Verification of Degenerate Band Edge Dispersion in Metallic Waveguides

The degenerate band edge (DBE) is a fourth order degeneracy occurring in a periodic structure at which four Bloch modes, both propagation and evanescent, coalesce. We experimentally demonstrate here for the first time the DBE dispersion in loaded metallic waveguides at microwave frequencies. The proposed waveguide in which DBE is observed here is designed by periodically-loading a circular waveguide with misaligned elliptical metallic rings. We validate the existence of the DBE in the presented waveguide using measurements and we report good agreement with full-wave simulations of the waveguide near the DBE; taking into account metallic losses. We correlate our finding to theoretical and simulation results utilizing various techniques including dispersion synthesis. The proposed waveguide, and other metallic slow-wave structures supporting the DBE can be used for a variety of applications including pulse compression and high power microwave generation.