P2M-5 Analysis of Guided Propagation Using Hybrid Acoustic Bulk & Interdigital Transducer

This paper proposes an original approach to design a new kind of transducer dedicated to high frequency applications. Using either multilayer structure, membrane, or plate, the device is composed of an isopotential interdigital transducer (IDT) together with a back counter electrode. Although electrical excitation is the same as a BAW device, modal propagation is settled onto the surface of the guiding structure, as for a SAW component. These Hybrid IDTs work naturally on the second Bragg harmonic. Consequently, with a given lithography process, central frequencies are twice higher than standard SAW IDT. Numerical models required to validate the principles of this structure and characterize the devices are presented. They are based on FEM/BEM analysis. Physical mechanisms involved are discussed in the paper, in order to find general rules to design Hybrid IDTs. Finally, an experimental validation is reported in the case of a piezoelectric plate