Suppression of Bulk Wave Radiation from Surface Acoustic Wave Devices

It is well known that interdigital transducers usually launch a substantial amount of bulk wave radiation as well as the required surface wave. This dual effect is hardly surprising, since some of the first acoustic applications of such structures were specifically as sources of bulk wave radiation. The standard interdigital structure was used for this purpose by Mortley in 1965, and the interdigitally poled version described by Thomann in 1970 had already been described as a bulk wave transducer by van der Pauw in 1966. Furthermore, arrays of grooves were used as a means of converting bulk wave signals to surface waves, and vice versa , long before their use in reflective array compressors. Bulk wave radiation is therefore an expected rather than a surprising phenomenon in all these devices.