Shallow bulk acoustic wave devices employing energy trapping

Abstract

Energy trapping elements for use with shallow bulk acoustic wave devices of various kinds, to minimize the insertion loses in such devices due to spreading of electroacoustic energy into the crystal substrate upon which the devices are constructed. Electroacoustic energy propagated in a substrate is trapped close to the surface of the substrate by means of trapping elements comprising a plurality of strips or grooves disposed on the surface of the substrate in the path of the propagated energy, and oriented approximately perpendicularly to the direction of propagation. The spacing of the elements is such that their stop-band frequency, at which energy will be reflected, is substantially different from the characteristic center frequency of the entire device, in order that the elements will serve a purely trapping function and not a reflecting function.