Considerations in the Use of Coplanar Waveguide for Millimeter-Wave Integrated Circuits

Using a full-wave analysis, coplanar waveguide (CPW) transmission line is compared to microstrip in terms of conductor loss, dispersion, and radiation into parasitic modes. It is shown that, on a standard 0.1-mm semiconductor at 60 GHz, the dimensions of CPW can be chosen to give better results in terms of conductor loss and dispersion than microstrip. A calculation of parasitic mode generation is presented for CPW on a semiconductor for an open substrate, for a substrate suspended above a ground plane, and for substrates separated from a ground plane by quartz.