Analytical Characterization of CPW-to-Microstrip Transitions Used in RF Test Structures

A method for characterizing coplanar-waveguide (CPW) to microstrip transitions is presented in this paper. The method takes into account the coupling between the signal and ground pads and allows the analytical extraction of physically meaningful parameters for the transition model. The formulation of the method is based on a simple but rigorous analysis of the ABCD-parameters of two lines differing only in length. Simulations using a model incorporating the extracted parameters agree well with experimental data up to 30 GHz, validating the proposed method.