Large-Signal Time Domain Modelling of Noise in the Design of MESFET Oscillators

An analysis technique for MESFET microwave oscillators based on a large-signal equivalent circuit model is presented. The operation of the circuit may be simulated, generating long periods of time-domain data that may be used to accurately predict the oscillator´s frequency of operation, power output and harmonic content. By incorporating low-frequency, time-domain noise sources derived from physically representative frequency spectra the technique has the potential for modelling close-to-carrier noise, and could be used for the analysis of noise up-conversion and the effect of the device/circuit interaction on output noise. The model, and its use as both an analysis technique and a design aid is described. Difficulties encountered with the demodulation of the noise spectrum are discussed.