Broadband, Via-less Grounded Coplanar Waveguide-to-Microstrip Transition in D-band

An innovative, via-less grounded coplanar waveguide (GCPW)-to-microstrip (MS) transition is presented for use in broadband applications in the 110 to 170 GHz frequency range. The transition uses open-circuit quarter-wavelength microstrip stubs in the ground plane of the GCPW transmission line, to form a corrugated ground plane structure, resulting in a virtual electric wall. This significantly improves the insertion loss of the transition. A reduction of up to 3.8 dB in the insertion loss of the transition, in comparison with a non-corrugated GCPW-to-MS transition, was measured. Samples were manufactured by laser structuring an alumina substrate, and a back-to-back structure of the corrugated GCPW (CGCPW)-to-MS transition was measured. The average measured insertion loss per transition is 0.9 dB over 110 to 170 GHz, and the minimum insertion loss per transition is 0.35 dB, at 150 GHz. The transition presented here is compact, with a total size of $0.27 \lambda \times 0.16 \lambda$, at 140 GHz.