A system-level comparison of amplitude-vs frequency-modulation approaches exploited in low-power MEMS vibratory gyroscopes

Conventional MEMS vibratory gyroscopes rely on detecting the Coriolis-induced displacement amplitude along three orthogonal modes of a micro-mechanical structure. In recent years, an alternative approach based on frequency modulation, where the rate modulates the resonance frequency of the structure, has been proposed. This work tackles, from a system-level point of view, a comparison between the two solutions, aiming at a fair review of their main properties, advantages and drawbacks. The manuscript mainly focuses on low-power architectural aspects, on the sensitivity of the transduction principle against process and temperature variations, and on critical aspects related to the analog-to-digital conversion and the signal demodulation. Examples of experimental results enrich the discussion.

[1]  Andrei M. Shkel,et al.  MEMS Vibratory Gyroscopes: Structural Approaches to Improve Robustness (MEMS Reference Shelf) , 2008 .

[2]  Giacomo Langfelder,et al.  High Scale-Factor Stability Frequency-Modulated MEMS Gyroscope: 3-Axis Sensor and Integrated Electronics Design , 2018, IEEE Transactions on Industrial Electronics.

[3]  M. H. Kline,et al.  Quadrature FM gyroscope , 2013, 2013 IEEE 26th International Conference on Micro Electro Mechanical Systems (MEMS).

[4]  Bernhard E. Boser,et al.  17.6 A Fourth-Order Σ∆ Interface for Micromachined Inertial Sensors , 2004 .

[5]  Yan Su,et al.  A 0.23- $\mu \text{g}$ Bias Instability and 1- $\mu \text{g}/\surd $ Hz Acceleration Noise Density Silicon Oscillating Accelerometer With Embedded Frequency-to-Digital Converter in PLL , 2017, IEEE Journal of Solid-State Circuits.

[6]  Thomas W. Kenny,et al.  A 7ppm, 6°/hr frequency-output MEMS gyroscope , 2015, 2015 28th IEEE International Conference on Micro Electro Mechanical Systems (MEMS).

[7]  Roberto Oboe,et al.  A low-power 3-axis digital-output MEMS gyroscope with single drive and multiplexed angular rate readout , 2011, 2011 IEEE International Solid-State Circuits Conference.

[8]  Bernhard E. Boser,et al.  A 50 µW, 2.1 mdeg/s/√Hz frequency-to-digital converter for frequency-output MEMS gyroscopes , 2014, ESSCIRC 2014 - 40th European Solid State Circuits Conference (ESSCIRC).

[9]  Michael S. McCorquodale,et al.  A Monolithic and Self-Referenced RF LC Clock Generator Compliant With USB 2.0 , 2007, IEEE Journal of Solid-State Circuits.

[10]  Andrea L. Lacaita,et al.  A 160 µA, 8 mdps/√Hz frequency-modulated MEMS yaw gyroscope , 2017, 2017 IEEE International Symposium on Inertial Sensors and Systems (INERTIAL).

[11]  Enrico Dallago,et al.  An offset compensation technique for bandgap voltage reference in CMOS technology , 2008, 2008 IEEE International Symposium on Circuits and Systems.

[12]  Stefano Facchinetti,et al.  Development of a complete model to evaluate the Zero Rate Level drift over temperature in MEMS Coriolis Vibrating Gyroscopes , 2017, 2017 IEEE International Symposium on Inertial Sensors and Systems (INERTIAL).