Characteristic features of excitation and propagation of acoustic modes in piezoelectric plates

Abstract

Excitation and propagation of the I.V. Anisimkin and Lamb acoustic plate modes of various orders n has been experimentally investigated using, as an example, rotated 128° YX LiNbO₃ piezoelectric plates. It is shown that (1) an increase in the number of fingers of the interdigital transducers improves the frequency resolution of the neighboring modes with close velocities, (2) the use of aluminum as a finger material reduces the ripple of the mode amplitude-frequency characteristics (AFC) _n as compared to that in the case of gold fingers, and (3) the propagation loss increases with the distance and mode number n. It has been found that group velocities (v _g) _n and phase velocities (v _p) _n of the modes excited and received on the same surface of the plate do not change with distance starting, at least, from a 25-wavelength distance from the radiator. It has been established that, if the electrically conducting fluid is deposited on the opposite side of the plate, the shape of the (AFC) _n , central frequency f _n , and the phase characteristics of certain modes undergo changes that depend on whether the areas under the transducers are also covered with the fluid and on the distance between the transducers. No noticeable reflection of the modes from the plate edges has been recorded.