Integrated DC-isolated wideband coupling of half-mode SIW and half-mode buried-corrugated SIW

An integrated wideband coupler for DC-isolation between half-mode SIW (HMSIW) and half-mode buried corrugated SIW (HMBCSIW) is described. The coupler uses an array of quarter-wave open-circuit stubs series-connected between the top wall of the HMSIW and the top wall of the HMBCSIW. The top wall of the HMBCSIW is floating allowing direct connection of active devices and application of DC bias. The structure requires three metal layers separated by a core substrate and a thin-film dielectric. The core substrate, along with the waveguide width, primarily determines the propagation properties, and the thin-film dielectric layer ensures that the HMBCSIW has identical propagation properties to the HMSIW as well as broad-band coupling. Simulations and measurements of a waveguide structure, with a TE0.5,0 cut-off frequency of 3 GHz, fabricated on a FR4 core substrate with a polyethylene thin-film, demonstrate the feasibility.