Automating the Accurate Extraction and Verification of the Cardiff Model via the Direct Measurement of Load-Pull Power Contours

Abstract

The CAD design of Power Amplifiers requires an accurate non-linear modelling solution. Generally, this is provided by state function (1-V, Q-V) model formulations. These typically require time consuming measurement procedures for model extraction and verification. Look-up table a-wave based behavioral models, i.e. the Cardiff Model, extracted directly from measurement data provide for a robust alternative, addressing both simulation accuracy and model extraction time. The challenge is identifying, in a time efficient manner, the appropriate load-pull impedance space, that ensures the model coefficients are accurately extracted. This paper outlines an automated approach addressing this requirement, that exploits the novel features of emerging high-speed load-pull measurement systems to identify and then measure directly load-pull power contours. The automated approach reduces significantly the number of required measurements, hence the measurement time, compared with the traditional approach while also ensuring an accurate Cardiff Model is extracted. The approach is demonstrated on a 10W packaged Cree HFET.