CMUT with mechanically coupled plate actuators

Ultrasonic transducers are widely used in application fields of non-destructive testing, sensors and medical imaging. Capacitive micromachined ultrasonic transducers (CMUT) build a promising class of miniaturized and high-performance ultrasonic devices, which have been a part of active research for more than 20 years [1]. Currently, CMUTs suffer from limitations regarding their output pressure and addressable frequencies compared to established piezoelectric devices. We present a mechanically coupled micromachined ultrasonic transducer concept. Simulations based on finite element method (FEM) are used to analyze this approach regarding the eigenfrequency of the mechanical structure. In addition an analytical model for rigid coupling of single transducers is deduced. Preliminary test structures prove the concept and show a reduced resonance frequency. As the acoustic wave attenuation significantly decrease with lower frequencies in air, airborne applications benefit from reduced resonance frequencies.