Pseudo-Extensional Mode MEMS Ring Gyroscope

This paper presents the design and characterization of a yaw gyroscope which employs a pseudo-extensional mode of a ring. The extensional mode is typically a bulk mode where the ring width expands and contracts across its circumference in contrast to a traditional wineglass mode where the in-plane ring width stays nominally constant during vibrations. Our axial symmetrical gyroscope structure is comprised of an array of concentric rings to create an apparent extensional mode, but at much lower frequency since it is made of flexural elements. An advantage inherent to the new mode is the local rejection of linear accelerations as compared to the fundamental wineglass, which rejects linear accelerations by matching electrodes across the diameter of the ring. Implemented in the wafer-level Epitaxial Silicon Encapsulation process, the device occupies an area of 1.8 mm(2) and initial characterization clearly demonstrates feasibility of using the pseudo-extensional mode of vibration for rate sensing with Q-factors of 110,000 and noise level of 0.06 degrees/root hr.