Fully micromachined finite-ground coplanar line-to-waveguide transitions for W-band applications

A fully micromachined finite-ground coplanar (FGC) line-to-waveguide transition for W-band applications has been designed, fabricated, and tested. The transition utilizes a printed E-plane probe, inserted into the broad sidewall of a micromachined waveguide. This type of transition plays an important role in many applications where coupling between the popular FGC line and a waveguide is required. Excellent performance across the entire W-band of such a transition is presented in this paper. The investigated waveguide, micromachined in silicon using the deep reactive ion etching technique, demonstrates its potential as an alternative to costly conventional waveguides at high frequencies. A similar transition with a micromachined waveguide formed via bulk micromachining using a wet etchant is also demonstrated. The free-standing probe utilized in this second transition proves the potential of such transitions to be applicable well into the submillimeter and terahertz range.