Bandwidth enhancement of substrate integrated waveguide tunnels by longitudinal resonances

A new method to achieve wide pass-band characteristics on Substrate Integrated Waveguide (SIW) tunnel section is presented. It will be shown that three in-band longitudinal resonant-modes can be excited from the waveguide-feed interaction due to the frequency dispersive nature of the effective permittivity in a waveguide. Such modes correspond to the Epsilon Near Zero (ENZ) mode, a half-wavelength mode, and one-wavelength mode. In this paper theoretical and experimental results are presented to validate the concept.