A D-Band Rectangular Waveguide-to-Coplanar Waveguide Transition Using Metal Ridge

This paper presents a rectangular waveguide-to-coplanar waveguide (CPW) transition using metal ridge at D-band (110–170 GHz). The proposed transition is useful in particular for packaging circuits with large dimensions. A CPW with extended ground traces is designed on a quartz substrate and its performance is compared with a conventional CPW. Besides, an absorber layer is added underneath for restricting parasitic modes. As the critical part of the transition, the metal ridge is described in detail. The proposed rectangular waveguide-to-CPW transition using metal ridge is designed, fabricated, and measured in a back-to-back configuration. The electric field distribution as well as the assembly of the proposed transition is illustrated. For the fabricated transition prototype in a back-to-back configuration, the measured return loss remains better than 12.5 dB at D-band which corresponds to a bandwidth of 60 GHz. From 122.5 GHz to 156.5 GHz, the measured insertion loss is less than 3 dB while it increases to 4 dB at the maximum. Thus, each fabricated transition contributes less than 2 dB insertion loss at D-band.