Verification of Non-Linear MOSFET Models by Intermodulation Measurements Under Loadpull Conditions

The trend towards system-on-chip realisation tightens the design specifications and consequently imposes high accuracy requirements on device models. Hence, model validations by only single-tone CW excitations do no longer suffice, because the obtained accuracy can not straightforwardly be extrapolated to an expected accuracy under realistic large-signal operating conditions. We developed a measurement set-up that enables to characterise the amplitude and phase of intermodulation products at different load impedances, which can serve as an important verification tool with regard to power amplifier applications. This technique is applied to evaluate two non-linear MOSFET model representations: the compact BSIM3v3 model and the in-house developed look-up table model. We show that for both model types the phase disagreement is more pronounced than the amplitude inaccuracy. We also stress the importance of an adequate de-embedding of the bonding pads and access transmission lines.