Time-domain non-linear noise analysis of FET oscillators

A novel approach to the noise analysis of FET oscillators is presented. A highly accurate simulation environment for oscillator analysis is constructed, based on full time-domain transient analysis using an equivalent circuit type device model. Internal noise sources are introduced as random signals in the time-domain, with a frequency spectrum matched to the physical spectrum of the appropriate noise mechanism. The channel thermal noise as a function of the periodically varying channel resistance, is modeled in the time-domain, as is the thermal resistance at the gate and at terminations. Flicker noise within the device is also considered. The effects of these noise sources near the oscillation frequency can be seen in the phase noise sidebands, with the flicker noise dominant closer to the oscillation frequency. Presented results show phase noise spectra in good qualitative and quantitative agreement with experimental results for typical FET oscillators.