GaN FET's non-linear model constructed by adaptive multi-bias S-parameter measurements

The construction of a non-linear model of high frequency transistors requires S-parameter measurements at different bias points. For Gallium Nitride (GaN) based Field Effect Transistors (FETs) the safe operating area is wide, which means that the required number of bias points is very large. Consequently, the total measurement time increases to an impractical level. To reduce the total volume of experimental data and hence the measurement time, while still adequately capturing the non-linear device characteristics, a new adaptive measurement algorithm has been applied. This algorithm places more bias points in regions where the device characteristics changes rapidly and less bias points in regions where the device response stays constant. A comparison is made between S-parameter and Y-parameter based selection criteria. Finally, a GaN FET's non-linear model is constructed and good agreement is achieved between measurement and model results, verifying the proposed approach.