Acceleration sensitivity of SAW and STW devices

Abstract

An analysis of the normal acceleration sensitivity of rotated Y-cut quartz SAW (Surface Acoustic Wave) and STW (Surface Transverse Wave) resonators simply supported along rectangular edges is presented. The analysis is based upon the perturbation integral formulation of Tiersten (1978), and makes use of the previously known analytic representation of the substrate deformation for the case considered. An approximate acoustic mode shape which accounts for spatial variations along all three axes is employed in the perturbation integral, allowing the derivation of analytic expressions relating the normal acceleration sensitivity to such parameters as substrate length, width, thickness, and orientation, mode center offset, mode shape spatial variations, etc. While the case considered represents something of an overestimate as compared to support configurations typically employed in production, questions regarding aspect-ratio compensation, optimum choice of substrate parameters, etc. are clarified by the case considered. The results of the analysis compare favorably with measurements of oscillators employing two-port SAW and STW resonators.