Broadband microwave bulk acoustic delay device

摘要

A thin film piezoelectric transducer generates bulk mode ultrasonic elastic waves which propagate into a transmission medium, such as silicon. The wave is reflected back towards the first transducer by a reflecting surface. A second transducer is located adjacent to the first transducer and receives the acoustic wave from the reflected surface. The path length of the ultrasonic wave from the first transducer to the second transducer is long enough to enable the bulk wave to be in the Fraunhofer field. An acoustic absorbing material, such as indium, may be placed on the reflecting surface and on the surface containing the two transducers in selective areas to reduce undesired reflections. The structure is suitable for use in the microwave region wherein the insertion loss may be relatively constant over a given frequency band.