Extraction of a nonlinear AC FET model using small-signal S-parameters

The nonlinearities of an RF FET can be obtained by a set of small-signal circuit elements extracted over a range of terminal voltages and temperatures. This study used pulsed S-parameter measurements on a 3 /spl times/ 3 DC-bias-point grid at two different temperatures to obtain electrical and electrothermal nonlinearity coefficients up to the third order. The extracted nonlinear AC model can be used in a Volterra analysis to gain an insight into the distortion mechanisms. The measurement results were in good agreement with the calculated third-order intermodulation values.