On wafer intermodulation distortion measurements on resistive FET mixers for device comparison and model validation

Abstract

This work describes an "on wafer" mixer measurement test set that is close to real single FET mixer designs. The test set demonstrated for the first time that some GaAs p-HEMTs have better 3rd order intermodulation performance than some GaAs MESFETs when used as resistive FET mixers. It is also shown that HEMTs give the same conversion loss of MESFETs with a significantly smaller gate width. Preliminary simulations with both table and empirical models were presented, showing that further work is required before CAD models can be used to successfully minimise 3rd order intermodulation distortion in resistive FET mixers.