Readout Techniques for High-Q Micromachined Vibratory Rate Gyroscopes

Inexpensive MEMS gyroscopes are enabling a wide range of automotive and consumer applications. Examples include image stabilization in cameras, game consoles, and improving vehicle handling on challenging terrain. Many of these applications imposevery stringent requirements on power dissipation. For continued expansion into new applications it is imperative to reduce power consumption of present devices by anorder-of-magnitude.
Gyroscopes infer angular rate from measuring the Coriolis force exerted on avibrating or rotating mass. For typical designs and inputs, this signal is extremely small, requiring ultra low noise pickup electronic circuits. This low noise requirement directly translates into excessive power dissipation.
This work describes a solution that combines a new low-power electronic readout circuit with mechanical signal amplification using a technique called mode-matching.The electronic circuit continuously senses the resonance frequency of the mechanical sense element and electrically tunes it to maximize the output signal. A new androbust feedback controller is used to accurately control the scaling factor and band-width of the gyroscope while at the same time guaranteeing stability in the presenceof undesired parasitic resonances.  The circuit has been fabricated in a 0.35μm CMOS process and consumes less than 1mW. The spot noise is 0.004◦/s/√Hz.
Publication date: 
December 31, 2007
Publication type: 
Ph.D. Dissertation
Ezekwe, C. D. (2007). Readout Techniques for High-q Micromachined Vibratory Rate Gyroscopes. (n.p.): University of California, Berkeley.

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