Investigation of High Efficiency Large TBW Line Acoustic Wave Convolvers

摘要

Line acoustic waves (LAW) are guided modes which follow the sharp edge of a crystal substrate. They offer non-dispersive propagation, tight acoustic energy confinement, and the availability of a signal pickup geometry which can be much more efficient than that of surface acoustic wave (SAW) beamwidth compressor devices. The objective of this program was to carry out theoretical and experimental investigation leading to wide bandwidth LAW transducers and to explore the feasibility of large time-bandwidth LAW convolvers. Broadband LAW generation was performed by converting SAWs to LAWs in multistrip mode converters (MSMCs). An MSMC having a bandwidth of 25% and conversion loss of 5 dB has been demonstrated. Theoretical comparisons between LAW and SAW convolvers indicate that the LAW convolvers should have significantly higher efficiency once they are fully developed. Fabrication of long, straight, chip-free edges was investigated. Improved techniques for cleaving crystals are described and significant progress toward a versatile new technique for sawing high quality edges is reported. Areas requiring additional work are identified and potential applications of LAW devices are discussed. (Author)