This paper deals with FET's reactive nonlinearities characterization for intermodulation distortion prediction. An experimental procedure for extracting the second and third order coefficients of the Qg(Vgs,Vgd) bidimensional power-series expansion is suggested. It is based on Volterra-Series analysis and requires a previous extraction of Ids(Vgs,Vds) derivatives. The Qg(Vg$) characterization results for a HEMT in its saturated region are also shown and discussed, along with some considerations to improve the method
