Acoustically-Coupled MEMS Transducer Pairs with Loss and Gain

TL;DR

This paper investigates the acoustic coupling dynamics of MEMS transducer pairs immersed in water, exploring how coupling strength varies with physical parameters and how gain feedback can induce exceptional points or bifurcations.

Contribution

It models and experimentally characterizes the open-loop acoustic coupling and demonstrates the formation of exceptional points in MEMS transducer pairs with gain feedback.

Findings

Coupling strength depends on pitch and resonance frequency.

Gain feedback can induce exceptional points or bifurcations.

Experimental validation of acoustic coupling models.

Abstract

This work treats the dynamics of pairs of microelectromechanical ultrasound transducers (MUTs) that are immersed in water and acoustically coupled through the fluid medium. A series of these transducer pairs with varying diameters (and thus resonance frequency) and pitch separation (and thus coupling strength) are fabricated and measured. The work presented here models and quantifies the open-loop coupling between the MEMS transducer pairs and its dependence on pitch. Furthermore, a gain feedback loop is systematically applied to one of the device pair and the dynamics of the acoustically-coupled gain-loss system is investigated, and the formation of an exceptional-point or of an Hopf bifurcation is equally used to quantify the coupling coefficient. This work provides an experimental study of acoustic coupling in MUT transducers, as well as an exploration of the formation of exceptional points in acoustically-coupled MEMS transducers.