Excess noise in GaAs MESFET oscillators

A novel technique for numerically simulating oscillator noise spectra is introduced. Additive and multiplicative noise is simulated for three industrial GaAs MESFET designs (with buried, uniform, and ion implanted channels) oscillating in simple resonant circuits at a center frequency of 4 GHz. Each oscillator exhibits excess 1/f noise, so that S/sub Phi /(f) varies as f/sup 3/ for small offset frequency f. Simulation predicts that the buried channel oscillator is about 12 dB quieter than oscillators built around either the uniform channel or ion-implanted devices, partly because of differences in device Q´s. Using S/sub phi //Q as a figure of merit to account for different Q´s, the uniform channel device to 2 dB/Q quieter than the buried channel circuit and about 0.5 dB/Q quieter than the ion-implanted circuit.<>