Surpassing fundamental limits of oscillators using nonlinear resonators

TL;DR

This paper demonstrates that operating nonlinear resonators at specific anharmonic points can surpass traditional limits of oscillator stability, reducing phase noise beyond conventional linear regimes.

Contribution

It introduces a novel approach to oscillator design by exploiting anharmonic regimes, supported by a comprehensive model and experimental validation with NEMS devices.

Findings

Significant phase noise reduction at special anharmonic points

Model accurately predicts noise behavior in nonlinear oscillators

Experimental verification with nanoelectromechanical systems

Abstract

Self-sustained oscillators are ubiquitous and essential for metrology, communications, time reference, and geolocation. In its most basic form an oscillator consists of a resonator driven on-resonance, through feedback, to create a periodic signal sustained by a static energy source. The generation of a stable frequency, the basic function of oscillators, is typically achieved by increasing the amplitude of motion of the resonator while remaining within its linear, harmonic, regime. Contrary to this conventional paradigm, in this Letter we show that by operating the oscillator at special points in the resonators anharmonic regime we can overcome fundamental limitations of oscillator performance due to thermodynamic noise as well as practical limitations due to noise from the sustaining circuit. We develop a comprehensive model that accounts for the major contributions to the phase noise of the nonlinear oscillator. Using a nanoelectromechanical system (NEMS)-based oscillator, we experimentally verify the existence of a special region in the operational parameter space that enables a significant reduction of the oscillators phase noise, as predicted by our model.