Experimental Verification of the Smoothie Database Model for Third and Fifth Order Intermodulation Distortion

The experimental intermodulation verification of the Smoothie table-based model for FET devices is presented. The model is implemented in the Agilent’s Advanced Design System (ADS) circuit simulation program and is based on the smoothing spline approximation of the device Y-parameters. The device main functions, i.e. the terminal currents and charges, are calculated by the analytical line integration of the Y-parameters. The use of smoothing splines yields continuous higher order derivatives and, consequently, the correct simulation of higher order intermodulation products. The latter is of paramount importance in the development of 3G PA applications. The results presented show excellent agreement between the measured and modelled intermodulation distortion as function of bias and power.