Nonlinear technique for the analysis of the free-running oscillator phase noise in presence of an interference signal

Abstract

A new methodology for the prediction of oscillator phase noise under the effect of an interference signal is presented. It is based on a semi-analytical formulation in the presence of the noisy interferer, using a realistic oscillator model extracted from harmonic-balance simulations. The theoretical analysis of the phase process enables the derivation of key mathematical properties, used for an efficient calculation of the interfered-oscillator phase noise spectrum. The resulting quasi-periodic spectrum is predicted, as well as the impact of the interferer phase noise over each spectral component, in particular over the pulled oscillation frequency. It is demonstrated that under some conditions, the phase noise at this component is pulled to that of the interference signal. Resonance effects at multiples of the beat frequency are also predicted. The analyses have been validated with experimental measurements, obtaining excellent agreement.