Investigations on propagation and the band broadening effect of ridged rectangular waveguide integrated in a multilayer dielectric substrate

To improve the bandwidth of the substrate-integrated waveguide (SIW), a ridged substrate-integrated waveguide (RSIW) with a centre ridge of cylindrical posts is proposed. A 37% bandwidth enhancement is achieved in this study. Wider bandwidths are still possible. Theoretical design formulas are derived. In the derivation, the TE modes are made equivalent to those of a transmission line cavity, across the transverse plane, and the cavity is loaded by a ridge of capacitive posts. Good agreements are observed between the theoretical formulas, numerical simulations and a hardware experiment. The study ends by pointing out that the ohmic loss of a RSIW is just as low as that of an SIW and of a regular waveguide of solid wall.