Noise in oscillators with two asynchronous oscillations

This paper describes noise phenomena in oscillators with two degrees of freedom, sustaining two-frequency asynchronous oscillations. The oscillator is comprised of two parallel high-Q-resonant RLC circuits connected in series to an active voltage-controlled one-port device with a symmetric volt-ampere characteristic having a nonlinearity described by a function arctg(x). The oscillator under analysis is isochronous, as it uses a purely resistive active device and has no additional phase shifts in the positive feedback loops. Phase noise at the two frequencies due to white noise sources is uncorrelated, while amplitude noise shows some mutual correlation. The main features of the noise characteristics arise due to the interaction of the two asynchronous oscillations via the common bias.