Fabrication and performance evaluation of micromachined cavity-backed co-planar waveguide to rectangular waveguide transition at Y-band frequencies

In this study, we propose a cavity-backed CPW (CBCPW) to rectangular waveguide transition compatible with silicon microfabrication techniques that does not require multiple parts and assemblies. In this approach, the complexity associated with fabrication of suspended probe is eliminated and a compact and wideband transition is achieved using a novel two-pole resonant matching network. The transition is composed of a shorted CPW line over a reduced height short-circuited waveguide segment that is followed by an E-plane step discontinuity to a standard height waveguide. Since the structure is simple with the features aligned with the Cartesian coordinate surfaces, it is highly compatible with microfabrication processes and can be fabricated using multi-stage deep reactive ion etching of silicon. A scaled model of this transition at Ka-band was fabricated using the standard machining tools, and its performance validated experimentally. In this paper, the same structure is considered for fabrication using silicon micromachining for operation at Y-band (240 GHz) frequencies.