Simple modeling of coplanar waveguide on thick dielectric over lossy substrate

We present a simple semi-empirical high-frequency equivalent circuit model to characterize the coplanar waveguide structure, which consists of a relatively thick metal line on very thick polyimide over a lossy substrate such as a Si BiCMOS wafer. Considering the geometric dependence of the conductive loss and the skin effect of the substrate loss, we derive modified models for the equivalent circuit elements. We verify the validity of our model by comparing it with experimental measurements. Our model is simple enough not only to be suitable for efficient circuit simulation but also to be useful for process characterization and design.