Model of flicker noise effects on phase noise in oscillators

Phase noise models that describe the near-carrier spectrum in an accurate but insightful way are needed, to better optimize the oscillator design. In this paper we present a model to describe the effect of flicker noise sources on the phase noise of an oscillator, that can be applied both to linear oscillators and to nonlinear structures like relaxation and ring oscillators, so extending previous works that considered only the effect of flicker noise superimposed to the control voltage of a VCO. We separate the effect of high-frequency noise sources, that are known to provide a Lorentzian-shaped phase noise spectrum, from flicker noise. The latter causes a change in the circuit bias point, that can be mapped in a shift in the oscillation frequency by exploiting Barkhausen criterion (for linear oscillators) or by CAD simulations. The overall oscillator spectrum can be obtained as a convolution of the Lorentzian spectrum due to white noise with the probability density function of frequency fluctuations due to flicker noise sources.