Millimetre-wave device modelling differences in microstrip and coplanar waveguide

The measurement of an active device produces results which depend on the transmission medium in which the device is embedded. These differences, insofar as a particular device is concerned, are related solely to its extrinsic elements, the intrinsic device being the same in all cases. Results are presented for on-wafer measurement and 2-D simulation of a specially designed active device and its associated transmission structure in both microstrip and coplanar waveguide. The measured and simulated results are obtained for pseudomorphic HEMTs (high electron mobility transistors) with a 0.2- mu m gate length arranged in a 6- mu m*15- mu m configuration with typical extrinsic f/sub t/´s of 70 GHz. The dual approach considered here has the advantage of enabling a model for the intrinsic device to be validated and the extrinsic model elements for both structures to be obtained.<>