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International Journal of Antennas and Propagation
Volume 2015, Article ID 481768, 7 pages
Research Article

A Comparative Study between Via-Hole and Via-Free Grounded Coplanar Waveguide to Microstrip Transitions on Thin Polymer Substrate

IETR Site de Nantes, Université de Nantes Angers Le Mans (UNAM), UMR CNRS 6164, 2 rue de la Houssinière, BP 92208, 44322 Nantes Cedex 3, France

Received 27 August 2015; Revised 3 November 2015; Accepted 6 December 2015

Academic Editor: Shih Yuan Chen

Copyright © 2015 Mohammed El Gibari and HongWu Li. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


A comparative study between via-holed and via-free back-to-back GCPW-MS-GCPW (Grounded Coplanar Waveguide-Microstrip lines) transitions is reported in this paper. According to simulation results, both via-holed and via-free transitions on commercial benzocyclobutene polymer 20 µm film show a bandwidth over 57 GHz. Bandwidth of optimized via-holed transitions increases with the via-hole diameter, up to 75 GHz with 300 μm via-hole diameter. The via-hole free transition achieves experimentally an ultrabroadband from 2 GHz to 78 GHz with an insertion loss of only 0.5 dB thanks to the copper metallization thickness of 2 μm. In addition, these measurement results are in perfect agreement with the simulation results. These via-free and via-holes transitions are very useful and requested in component packaging, on-wafer measurements of microstrip based microwave integrated circuits, and also the interconnections in hybrid circuits including both microstrip and coplanar structures.