Two-Material Ridge Substrate Integrated Waveguide for Ultra-Wideband Applications

A novel ridge substrate integrated waveguide (RSIW) with extended single-mode bandwidth is presented in this paper. The proposed structure is based on a substrate integrated waveguide including two dielectric layers with different permittivity. The ridge is implemented by a row of partial height metal vias, connected at the bottom by a metal strip. An RSIW with cutoff frequency of the fundamental mode at 2.5 GHz and of the second mode at 12 GHz is proposed, thus achieving a bandwidth of almost 5:1. This structure is suitable for applications covering the entire ultra-wideband. The proposed RSIW has been fabricated and tested to verify experimentally the electromagnetic properties of the fundamental and second mode. Finally, the role of the metal strip connecting the bottom of the ridge vias is discussed, showing through numerical and experimental results that the strip plays a fundamental role in avoiding the bandgap in the frequency response of the RSIW.