Theoretical analysis of micro-machined ultrasonic transducer using a simple 1-D model.

Micro-machined ultrasonic transducers (MUT) appear as an attractive alternative to standard bulk transducers mainly based on PZT ceramic actuators. However, the simulation of these new devices requires one to take correctly into account their operating conditions. Particularly, most of the MUT structures are periodic, associating a very large number of elementary actuators excited in phase.

Full band gap for surface acoustic waves in a piezoelectric phononic crystal.

A plane-wave-expansion method suited to the analysis of surface-acoustic-wave propagation in two-dimensional piezoelectric phononic crystals is described. The surface modes of a square-lattice Y-cut lithium niobate phononic crystal with circular void inclusions with a filling fraction of 63% are identified. It is found that a large full band gap with a fractional bandwidth of 34% exists for surface acoustic waves of any polarization and incidence, coincidentally with the full band gap for bulk waves propagating in the plane of the surface.

Three-dimensional modelling of micromachined-ultrasonic-transducer arrays operating in water.

We report on the 3-D modelling of periodic arrays of capacitive micromachined ultrasonic transducers (cMUTs) operating in fluid. Specific developments have been performed to model biperiodic transducer arrays and to take into account radiation into any stratified media at the front-side as well as the back-side of the device. The model is based on a periodic finite-element-analysis/boundary-element-method (FEA/BEM).

Fast FEM/BEM simulation of SAW devices via asymptotic waveform evaluation.

The finite element method/boundary element method (FEM/BEM) computation model applied to surface acoustic wave devices requires the solution of a large linear system for each frequency point. An asymptotic waveform evaluation technique is used to obtain an approximate solution of the linear system that is valid over a large frequency bandwidth. The approximate solution was shown to be very accurate and vastly reduces the computation time.

A full 3D plane-wave-expansion model for 1-3 piezoelectric composite structures.

The plane-wave-expansion (PWE) approach dedicated to the simulation of periodic devices has been extended to 1-3 connectivity piezoelectric composite structures. The case of simple but actual piezoelectric composite structures is addressed, taking piezoelectricity, acoustic losses, and electrical excitation conditions rigorously into account. The material distribution is represented by using a bidimensional Fourier series and the electromechanical response is simulated using a Bloch-Floquet expansion together with the Fahmy-Adler formulation of the Christoffel problem.