Matching of GaAs power FETs using a large-signal modelling technique

Abstract

A large-signal modelling program based on fundamental frequency harmonic balance is described. The model uses nonlinear elements derived from bias-dependent S-parameter measurements and proves to be computationally efficient and suitable for use in modelling power FETs. Simulated output powers and gains as a function of output impedance are presented for the Plessey 4820 power FET. Results from a narrow-band prematched module designed using the large-signal model are presented showing output power within 0.5 dB of the theoretical maximum in the 7.9 to 8.4 Ghz band. This was achieved without the need for any fine tuning.