A method for characterizing coplanar waveguide-to-microstrip transitions, and its application to the measurement of microstrip devices with coplanar microprobes

Abstract

This paper presents a method for characterizing coplanar waveguide-to-microstrip (CPW-M) transitions by using on-wafer coplanar (CPW) microprobes. It is based on extracting the transmission matrix of the CPW-M transition from the measurement of the S parameters of two microstrip transmission lines of different lengths, each of which includes two CPW-M transitions. To verify the proposed method, the S parameters of a zero-length line, which is composed of two CPW-M transitions (thru connection) and has not been used in the transition characterization, are measured up to 40 GHz and are compared to those extracted and obtained from electromagnetic simulations. The method is applied to the measurement of a microstrip coupled-line filter embedded in CPW-M transitions.