Patent ID: 8347718

Claim:
An angular velocity sensor, comprising; a semiconductor substrate; a ring structure arranged to vibrate; a support arranged to support the ring structure relative to the semiconductor substrate; at least one primary drive transducer arranged to cause the ring structure to oscillate in a primary mode substantially at a resonant frequency of the primary mode; at least one primary pick-off transducer arranged to detect oscillation of the ring structure in the primary mode; a primary control loop arranged to receive primary pick-off signals from the at least one primary pick-off transducer and provide primary drive signals to the at least one primary drive transducer to maintain resonant oscillation of the ring structure; and wherein the primary control loop includes a first means arranged to determine an amplitude of the fundamental frequency of the primary pick-off signals and a second means arranged to determine an amplitude of the second harmonic frequency of the primary pick-off signals and a drive signal generator arranged to produce the primary drive signals with amplitude that is dependent on a ratio of the amplitude of the second harmonic frequency of the primary pick-off signals over the amplitude of the fundamental frequency of the primary pick-off signals.