A piezoelectric gyroscope based on thickness-shear modes of an AlN bimorph with inclined c-axes

We propose a new structure for piezoelectric gyroscope application. It consists of a two-layered plate of AlN with inclined c-axes. Through a theoretical analysis, it is shown that when the plate is electrically driven into thickness-shear (TSh) vibration in one direction and is rotating about the plate normal, the rotation causes a TSh vibration in a perpendicular direction with an electrical output which can be used to measure the angular rate of the rotation. Since AlN can be made into thin film devices much smaller than conventional crystal acoustic wave devices, the proposed gyroscope can be made much smaller than existing piezoelectric gyroscopes. The structure can also work with other crystals of class 6mm such as ZnO and polarized ceramics.