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The development of new surface acoustic wave devices exhibiting complicated electrode patterns or layered excitation transducers has been favored by an intense innovative activity in this area. For instance, devices exhibiting interdigital transducers covered by piezoelectric or dielectric layers have been fabricated and tested, but the design of such structures requires simulation tools capable to accurately take into account the actual shape of the wave guide elements. A modeling approach able to address complicated surface acoustic wave periodic structures (defined in the saggital plane) exhibiting any geometry then has been developed and implemented. It is based on the combination of a finite element analysis and a boundary element method. A first validation of the computation is reported by comparison with standard surface wave devices. Surface transverse wave resonators covered by amorphous silica have been built and consequently used for theory/experiment assessment. Also the case of recessed electrodes has been considered. The proposed model offers large opportunities for modeling any two-dimensional periodic elastic wave guide. [ABSTRACT FROM AUTHOR]

The possibility to excite and detect acoustic waves in fluids using capacitive transducers built on silicon using surface micromachining offers attractive opportunities in the manufacturing of high quality low cost imaging probes. As in the case of standard probe transducers, simulation codes are required to accurately design such devices. The periodic structures extensively used for these capacitive transducers has to be accounted for. In this work, a two-dimensional finite element analysis of capacitive micromachined ultrasonic transducers (cMUT) is proposed, taking into account periodicity and radiation in fluids. The convergence of the calculation is verified using different computation approaches. It is then shown that the periodic computations provide a rapid and precise analysis of the cMUT compared to non periodic calculations. The mutual displacements are deduced from the periodic harmonic calculation, providing an efficient estimation of cross-talk phenomena arising for cMUT radiating in water. The capability of cMUT operating under such conditions to generate a low velocity wave guided at the fluid/silicon interface is theoretically pointed out. [ABSTRACT FROM AUTHOR]

The demand for high frequency surface acoustic wave devices for modern telecommunication applications imposes the development of devices able to answer the manufacturer requirements. The use of high velocity substrates for which a piezoelectric layer is required to excite and detect surface waves has been widely investigated and requires the implementation of accurate theoretical tools to identify the best combinations of material. The present paper proposes a mixed formulation combining finite element analysis with a boundary integral method to accurately simulate the capability of massive periodic interdigital transducers to excite and detect guided acoustic waves in layered media. The proposed model is exploited for different typical configurations. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]