PRINCIPLES AND APPLICATIONS OF PRAETERSONICS.

Abstract : Praetersonics is concerned with the application of acoustic waves and acoustic wave interactions at frequencies in excess of 100 MHz. Such high frequency acoustic waves are already being exploited in a large number of devices. These devices have been based on the use of bulk acoustic waves, surface acoustic waves, magnetoelastic waves, acousto-electric interactions, and opto-acoustic interactions. In summing up the advantages of using acoustic (rather than electro-magnetic) waves it may be said that, for almost every device considered, there is a tremendous reduction in physical size. In specific cases there may be other advantages, such as the ability to electronically control time delay or phase shift, or to realize certain microwave signal processing functions not obtainable by other means. In view of the modern trend towards microminiaturization and circuit integration, however, it probably has been the small physical size of praetersonic devices that has played the greatest role in generating the large amount of interest in this field now being displayed. Praetersonic applications have become feasible only because of technological advances in the areas of transducers and materials. Research in these two areas will continue to be important (a prerequisite) if practical praetersonic devices are to be realized. So far as is known the report represents one of the few examinations of the many aspects of praetersonics that have been made. Previous works have concentrated along narrower lines. (Author)