PROPERTIES OF NRD-GUIDE AND H-GUIDE HIGHER-ORDER MODES - PHYSICAL ANDNONPHYSICAL RANGES

New, interesting modal properties are presented for the waveguiding st ructure consisting of a rectangular-section dielectric rod sandwiched between parallel conducting plates, which can represent either a nonra diative dielectric (NRD) guide or an H guide. A rigorous quantitative analysis of the dispersion properties, making use of both wavenumber a nd steepest-descent plots, indicates that higher-order modes can show different anomalous behaviors, as geometrical and electromagnetic para meters vary. A discussion of the physical nature of the waves related to complex wavenumbers allows us to illuminate the performance differe nces between NRD and H guides, as regards certain previously unexplore d leakage effects.