New unidirectional transducer and broadband reflector of acoustic surface waves

An acoustic-surface-wave multistrip coupler, formed into the shape of a U, may be used on materials of high electro-mechanical coupling coefficient to convert a bidirectional interdigital transducer into a unidirectional transducer with negligible loss of bandwidth. The U-shaped coupler by itself acts as a normal-incidence mirror, and can have a reflection loss of less than 2 dB over a 60% bandwidth. Both devices are constructed of evaporated aluminium by existing photolithographic techiques. No special polishing operations or extra electrical components are required.