Theoretical Analysis of Planar Bulk-Acoustic-Wave Response

Interdigital Transducers (IDT’s) on a piezoelectric substrate launch, in addition to surface-acoustic waves (SAW’s), bulk-acoustic-waves (BAW’s) into the medium. Some of these BAW’s reach the output IDT after reflection from the bottom surface. Devices using this phenomenon are known as planar bulk-acoustic-wave devices and have gained considerable importance in recent years due to the fact that they operate at higher frequencies. A detailed theoretical analysis is presented for this device that results in a method for computing the bulk-acoustic-wave response for any orientation of any piezoelectric substrate. The BAW response for several devices for which experimental results are published, is computed using this method. The computed results are found to be in excellent agreement with the experimental ones. The analytical technique is also used to optimize one of these devices to achieve a lower value of insertion loss, by varying the separation between the two interdigital transducers. © 1990, IEEE