Highly Sensitive Coupled Oscillator Based on an Exceptional Point of Degeneracy and Nonlinearity

TL;DR

This paper introduces a highly-sensitive oscillator based on an exceptional point of degeneracy and nonlinearity, demonstrating both theoretical and experimental results that show improved sensitivity to circuit perturbations for sensing applications.

Contribution

It presents a novel coupled-resonator oscillator scheme utilizing an exceptional point of degeneracy and nonlinear effects to enhance sensitivity, with practical implementations and analysis of perturbation responses.

Findings

Achieved second-order EPD in coupled LC resonators with gain and loss.

Demonstrated ultrasensitivity of oscillation frequency to component perturbations.

Validated the scheme experimentally with wirelessly coupled resonators.

Abstract

We propose a scheme for obtaining highly-sensitive oscillators in a coupled-resonator system with an exceptional point of degeneracy (EPD) and a small instability. The oscillator with the exceptional degeneracy is realized by using two coupled resonators with an almost balanced small-signal gain and loss, that saturates due to nonlinear effects of the active component, resulting in an oscillation frequency that is very sensitive to a perturbation of the circuit. Two cases are investigated, with two parallel LC resonators with balanced small-signal gain and loss that are either coupled wirelessly by mutual inductance or coupled-wired by a capacitor. This paper demonstrates theoretically and experimentally the conditions to obtain a second-order EPD oscillator and analyzes the ultrasensitivity of the oscillation frequency to components' perturbation, including the case of asymmetric perturbation that breaks PT-symmetry. We discuss the effects of nonlinearity on the performance of the oscillator and how the proposed scheme improves the sensing's sensitivity of perturbations. In contrast to previous methods, our proposed degenerate oscillator can sense positive or negative changes of a circuit component. The degenerate oscillator circuit may find applications in various areas such as ultrasensitive sensors, tunable oscillators and modulators.