Surface acoustic wave device with reflectors in inter-electrode location

Abstract

An acoustic transducer is arranged as a ladder having uprights and rungs consisting of contact pads and interdigital fingers respectively. The transducer has inter-rung spaces 17 occupied by arrays of reflector strips. Each reflector strip is offset by .lambda./8 from a respective position distant 1/2n.lambda. from a transducer finger center, .lambda. being the transducer finger center and n as integer. The .lambda./8 offset reflector strips provide constructive interference between transducer output waves travelling in one direction and destructive interference in the opposite direction. This provides a transducer with undirectional properties which can be manufactured in one metal deposition process. Unwanted reflections at fingers may be reduced by additional blooming reflector banks or by repositioning reflector strips to provide both unidirectional and blooming properties. Other options include variation in spatial periodicity, overlap, length, width and/or number of reflector strips and/or transducer fingers.