A Study of High Frequency Performance of Coplanar Waveguide as a Function of Substrate Thickness

A theoretical model is derived which predicts the critical frequency above which coupling between Coplanar Waveguide and substrate modes occurs, and some design curves are presented. The measured performance of Coplanar Waveguide components is reported as a function of substrate thickness (GaAs) in the frequency range 0.04-110 GHz, and demonstrates improved mm-wave performance of transmission lines and short circuit elements on thinned substrates due to a reduction in moding, as predicted by the theoretical analysis.