Abstract :
Since the mid-1960s, there has been a strong upsurge of interest in the propagation of surface acoustic waves on solids. The stimulus for this interest came from the realisation that simple, compact, and potentially cheap surface-acoustic-wave devices could be made which performed valuable signal-processing functions principally at intermediate frequencies. In a very short space of time these devices have met demanding specifications and have been accepted for military systems. This article reviews the recent work on surface acoustic waves (s.a.w.s) with the main emphasis on devices and applications. The introductory section provides basic background information on the nature, propagation and transduction of s.a.w.s. In some s.a.w. devices, propagation of the surface wave is influenced by surface structures which reflect, couple, guide or amplify the wave, and these are reviewed prior to the main section which is devoted to the more important s.a.w. devices, i.e. delay lines, tapped delay lines, frequency filters, oscillators, fixed and programmable analogue matched filters, convolvers and correlators, and finally, devices related to displays. Surface-wave devices are beginning to have an impact in both radar and communications systems. Both these areas of application are reviewed with particular reference to code generation and matched filtering (pulse compression) for high-performance radars, correlation systems for simple radars, synthetic-clutter generation for clutter-reference radars, compressive receivers, processors for fusing and filters for acquisition of synchronisation in communication systems. At appropriate points in the review, basic limitations of s.a.w. devices are indicated and the competition offered by other devices is assessed.
