RESUMEN
Experimental results are presented to support the hypothesis that the shape and location of the active region of vibration in a thickness shear mode quartz resonator are the dominant factors in determining the acceleration sensitivity of the resonator. The shape and location of the mode in a real world resonator vary sufficiently from unit to unit (due to material and processing variations) that all other considerations are overwhelmed. It is shown experimentally that the mode shape and/or location can be trimmed with energy trapping by judicious addition or subtraction of mass to produce resonators with improved acceleration sensitivity.
RESUMEN
A perturbation technique for calculating the change in mode shape in a plano-convex thickness shear resonator blank due to off-center mass perturbations is developed. The perturbed shape is built as a linear combination of the familiar unperturbed modes and their anharmonics. The change in the location of the average center of the mode is calculated for different contours and different mass perturbation shapes and thicknesses. The results are used to predict changes in the acceleration sensitivity of two-point mounted 10-MHz, third SC-cut resonators when patches of metal film are deposited on the major surfaces off-center. These theoretical results are compared with published experimental results.