Phased array acoustic signal processor

Abstract

A bulk acoustic signal processor for processing GHz range R.F. signals employs a transmitter array comprised of an apodized set of subdivided interdigital electrodes mounted on a bulk wave launching crystal, the apodization being defined by the shape of an aperture in a layer of dielectric material on the crystal, over which the electrodes extend into contact with the surface of crystal for stressing the crystal and launching an acoustic wave into the bulk on which the crystal is mounted. Because a respective subdivided set of interdigital electrode elements has an impedance on the order of 0.5 to 6 ohms, each set is driven by a dedicated, impedance-transforming GaAs FET source-follower amplifier. When driven by an R.F. input signal, the respective sets of driver electrodes launch a focused set of acoustic waves which effectively spatially combine with one another to form a directed bulk wave whose direction of travel in the bulk is proportional to the input frequency and whose intensity is sufficient to enable the input energy to be detected by a spaced apart receiver electrode array. The receiver electrode array, similar to its transmitter counterpart, is formed of a plurality of interleaved electrode layers or fingers which extend over the layer of dielectric atop the lithium niobate crystal and into a receiver array aperture in the dielectric layer into contact with the surface of the crystal.