Elastic Surface Wave Guidance by (Δv/v) Effect Guidance Structures

Abstract

The possibility of utilizing guided surface acoustic waves in signal processing devices has generated interest in basic investigations of guidance mechanisms and structures for surface acoustic waves. Surface wave propagation, investigated in detail thus far in guidance structures, has unfortunately proven sufficiently dispersive to rule out many practical device applications. Reported here are theoretical investigations of the basic physical phenomena of a (Δv/v) guidance structure which is substantially nondispersive. Acoustic guidance in the (Δv/v) structure is assumed to be due principally to the velocity reduction Δv of a thin conducting strip on a piezoelectric substrate. With this assumption, major features of (Δv/v) guidance can be predicted theoretically from an isotropic nonpiezoelectric model which incorporates the velocity difference Δv. Numerical results are presented for quartz and lithium niobate. In addition, a generalized description for guided waves is developed which is approximately independent of the (Δv/v) velocity ratio. Thus, with the use of scaling factors, the normalized data are applicable to materials with a range of (Δv/v) ratios. Simply put, our principal conclusion is that for many common piezoelectrics, strong guidance and low dispersion are theoretically predicted. Basic experimental investigations thus appear warranted.