This paper demonstrates how probe effects deteriorate mTRL-calibrated S-parameter measurements of conductor-backed CPW structures. A thorough study of CB-CPWs through field analysis is presented and for the first time an analytical description to predict the occurrence of ripples and resonance effects taking the probe geometries into account is presented. The analytical description is verified by em simulation and measurement for two different substrate materials, i.e. fused silica and alumina.

An existing analytical transmission line model to describe propagation properties of coplanar waveguides including parasitic effects was extended to take into account surface roughness of conductor traces. The influence of those parasitics is successively included in the simulation and compared to measurements. The device under test (DUT) was fabricated on an ceramic wafer. Propagation characteristics were measured up to 120 GHz.