We hereby present a new equivalent circuit model including both lumped and distributed elements for GCPW-MS transitions (GCPW for Grounded Coplanar Waveguide and MS for Microstrip). In order validating the modelling results, such transitions have been fabricated on a 20 µm-thick BCB (Benzocyclobutene resin) substrate using grounding pads including via-holes of different diameters. The study focuses on the impact of the via-hole design on the performance of the transition and more specifically on its bandwidth. The transitions were made using a simple technological process based on photosensitive polymer. ADS simulation data of the new equivalent circuit model were in very good agreement with measured S-parameters. Both theoretical and experimental results show that the bandwidth of such a transition can reach up to 100 GHz bandwidth using via-holes of 900 µm diameter.
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