Design and development of a MEMS-IDT gyroscope

The design, development and performance evaluation of a novel radio frequency microelectromechanical systems (MEMS) gyroscope, based on a surface acoustic wave resonator (SAWR) and a surface acoustic wave sensor is presented in this paper. Most of the MEMS gyroscopes based on silicon vibratory structures that utilize the energy transfer between the two vibratory modes demand small fabrication tolerances to minimize signal output when there is no rotation (i.e. zero rate output). This 1 cm × 1 cm gyroscope operates based on the principle of a surface acoustic wave (SAW) on a piezoelectric substrate. The SAWR creates SAW standing waves within the cavity space between the interdigital transducers (IDTs). The particles at the anti-nodes of a standing wave experience large amplitudes of vibration perpendicular to the plane of the substrate, which serves as the reference vibrating motion for this gyroscope. A number of metallic dots (proof masses) are strategically positioned at the anti-node locations so that the effect of the Coriolis force due to rotation will amplify the magnitude of the SAW that is generated in the orthogonal direction. The performance of this 74.2 MHz MEMS-IDT gyroscope has been evaluated using rate table and geophone set-ups, indicating very high sensitivity and dynamic range, which is ideal for many of the commercial applications. Unlike other MEMS gyroscopes, this gyroscope has a planar configuration with no suspended resonating mechanical structures, thereby being inherently robust and shock resistant. In view of its one-layer planar configuration, this gyroscope can be implemented for applications requiring conformal mounting onto a surface of interest. (Some figures in this article are in colour only in the electronic version; see www.iop.org)