Thin-film Bulk Acoustic Wave Delay Line

Abstract

A thin-film bulk acoustic wave delay line device providing true-time delays and a method of fabricating same. An exemplary device can comprise several thin-film layers including thin-film transducer layers, thin-film delay layers, and stacks of additional thin-film materials providing acoustic reflectors and matching networks. The layer material selection and layer thicknesses can be controlled to improve impedance matching between transducers and the various delay line materials. For example, the transducer layers and delay layers can comprise piezoelectric and amorphous forms of the same material. The layers can be deposited on a carrier substrate using standard techniques. The device can be configured so that mechanical waves propagate solely within the thin films, providing a substrate-independent device. The device, so constructed, can be of a small size, e.g. 40 μm per side, and capable of handling high power levels, potentially up to 20 dBm, with low insertion loss of approximately 3 dB.