An Approach to Linear Modeling of CMUTs: A Review

In this work, an introduction to the technology of Capacitive Micromachined Ultrasonic Transducers (CMUTs), based on its fundamental principles and small-signal modeling, is presented. The aim is to summarize the equations leading to lumped elements of the small-signal equivalent circuit through the conventional electrostatic transducer analysis; a parallel-plate capacitor with a movable plate, such modeling allows the designer insight into understanding more complex CMUT models. Furthermore, the material properties and geometry of the CMUT are proposed for concept validation purposes. As a result of it, approximate values of 150V and 1MHz are obtained for the collapse voltage and the natural frequency respectively. Finally, the small-signal model is implemented in Cadence Virtuoso, its operation as a transmitter is evaluated, where the model captures the spring softening effect, as well as different propagation media of the ultrasonic waves, which effects are consistent with the small-signal model behavior reported up to now.