ABSTRACTThe characteristics of QSH (quasi shear horizontal) acoustic wavespropagating in thin plates of Y-cut, X-propagation lithium niobate areinvestigated theoretically and experimentally. The fractional velocitychange (Δ v/v) produced by electrical shorting of the surface iscalculated as a function of the normalized plate thickness h/λ (h =plate thickness, λ = acoustic wavelength). It wasfound that values of Δ v/v as high as 0.18 could be obtained.Experimental measurements show good agreement with theory. The properties ofQSH waves propagating in the presence of a perfectly conducting electrodeseparated from the piezoelectric plate by a small air gap have been studiedtheoretically and experimentally. It was found that by varying the height ofthe gap, the phase shift through a 3.2-MHz QSH wave delay line can be variedby more than 230°. We have also theoretically investigated the influenceof a thin layer of arbitrary conductivity on the velocity and attenuation ofthe QSH wave. Calculations show that the variations in these parameters canbe as high as 18% and 5 dB per wavelength for a change in layer surfaceconductance from 10-7 to 10-5 S. Results obtained in this paperconfirm the attractive properties of QSH waves for a variety of sensing andsignal processing applications.
1999 IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control Vol. 46, pp. 1298-1302, 1999
© 1999, by The Institute of Electrical and Electronics Engineers, Inc. All rights reserved.