Three phase unidirectional transducer

摘要

Disclosed is a multiterminal acoustic surface wave transducer which has a unidirectional response characteristic over a selected operating frequency band and is capable of launching and receiving surface waves in a body of piezoelectric material. In a specific embodiment the transducer includes a plurality of sets of first, second and third parallel electrodes arranged in cascade on a surface of the piezoelectric material with a center-to-center electrode spacing equal to one-third wavelength of a selected frequency within the frequency band. Corresponding electrodes in each set are interconnected, with each group of interconnected electrodes forming a terminal of what is in this case a three terminal transducer. When a three phase electrical signal is supplied to the terminals of the transducer with a 120 DEG phase separation between terminals, the transducer will launch a corresponding surface wave in the piezoelectric material in the direction of phase progression among the electrodes. Since the transducer is reciprocal in nature it can also be used to receive an acoustic surface wave propagating in a body of piezoelectric material and supply a corresponding electrical signal to a three phase load.