Broadband characterization of planar transmission line substrate permittivity up to 67 GHz

In this paper, it is shown how different planar transmission lines (TL) such as microstrip (MS), coplanar waveguide (CPW) and grounded CPW (GCPW) can be used to characterize substrate permittivity using on-wafer probes and a thru-reflect-line (TRL) calibration. From measured S-Parameters, the effective permittivity ε_{r, eff} can be extracted and fast and precisely mapped to the physical value ε_r of the TL´s substrate using simulations. The results up to 67GHz for the aforementioned TL on a conventional RF substrate are presented and show very good agreement with each other as well as data supplied by the substrate manufacturer.