An analysis of propagation of surface acoustic waves in rotating piezoelectric plates

Abstract

As an important application of acoustic wave sensors, gyroscopes for rotation sensing purpose can also utilize surface acoustic waves in piezoelectric substrates. This requires an analysis of surface acoustic waves propagating in finite piezoelectric solids to aid the design process in parameter selection and optimization. Earlier studies have investigated the effect of rotation in semi-infinite piezoelectric solids, but result like this can only be considered as an approximation to actual gyroscopes with finite substrates. In this study, we consider the substrate as an infinite piezoelectric plate with finite thickness, thus enabling us to calculate the surface acoustic wave velocity in a rotating plate. It is known that there is only one velocity in a semi-infinite solid, but there will be two velocities if we study surface waves in an infinite plate. It is also found that both velocities are changed by the rotation. The numerical results on AT- and ST-cut quartz crystal show that both velocity branches have been changed and the two velocities can be clearly observed if the thickness of plate is less than three wavelengths. If the substrate is to be considered as a semi-infinite, the plate thickness has to be larger than three wavelengths. In this case, the effect of rotation on the velocity still exists, but the two modes essentially merged into the Rayleigh wave velocity. The velocity shifts due to rotation is different from the semi-infinite substrate, offering improved references and guidance in the substrate and material selection for rotation piezoelectric sensors. The extension of this study can be done with the application of two-dimensional theory for surface acoustic waves in finite plates.