On-wafer measurement of microstrip-based circuits with a broadband vialess transition

A broadband vialess coplanar waveguide (CPW)-to-microstrip transition for on-wafer measurements has been developed. The electrical connection between the top ground of the CPW and the bottom ground of the microstrip is realized by electromagnetic coupling, thus no substrate via holes are required. In this paper, simulation and measurement results of the transition are given, the optimal design rules are discussed, and the utilization of the transition for de-embedding microstrip benchmark structures is presented. The measured insertion loss of two transitions in a back-to-back configuration is less than 0.5 dB from 2.5 to 11.8 GHz, and the measured return loss is better than 20 dB from 3 to 11 GHz.