This paper reports on a new type of high-frequency mode-matched gyroscope with significantly reduced dependencies on environmental stimuli such as temperature, vibration, and shock. A novel stress-isolation system is used to effectively decouple an axis-symmetric bulk-acoustic wave (BAW) vibratory gyro from its substrate, minimizing the effect that external sources of error have on the offset and scale factor of the device. Substrate-decoupled (SD) BAW gyros with a resonance frequency of 4.3 MHz and Q values near 60 000 were implemented using the high aspect ratio poly and single-crystal silicon (HARPSS) process to achieve ultra-narrow capacitive gaps. Wafer-level packaged sensors were interfaced with a customized application-specific integrated circuit (ASIC) to achieve low variations in the offset across temperature (±26°s − 1 from − 40 to 85°C), supreme random-vibration immunity (0.012°s − 1 g RMS − 1 ) and excellent shock rejection. With a scale factor of 800 μV (°s, the SD-BAW gyro system attains a large full-scale range (±1250°s) with a non-linearity of less than 0.07%. A measured angle-random walk (ARW) of 0.39°/√h and a bias instability of 10.5°h − 1 are dominated by the thermal and flicker noise of the integrated circuit (IC), respectively. Additional measurements using external electronics show bias-instability values as low as 3.5°h INTRODUCTIONMicromachined gyroscopes have enabled a myriad of applications that range from basic motion detection for gaming to safety control systems in automobiles 1 . More recently, an increased interest in the use of microelectromechanical system inertial sensors for dead reckoning and pedestrian navigation in handheld electronics has placed stringent requirements on the die size, power consumption, and overall performance of this type of device. To date, most commercially available rate sensors have been designed as low-frequency flexural tuning-fork gyroscopes (TFGs), which are typically sensitive to random vibrations and prone to linear accelerations, such as those experienced under shock. These limitations complicate the use of TFG technology in large-volume, high-end applications, particularly in personal navigation, for which dependencies on fluctuations in the environment translate into long-term drift in the output of the system. Additionally, in recent months, concerns about the high sensitivity of consumer-grade gyroscopes in response to lowfrequency pressure signals that can be used to recover audio have increased as a potential threat for eavesdropping 2 , justifying the need for more environmentally robust rotation sensors.Acceleration suppression mechanisms can be implemented in TFGs to alleviate part of this problem using redundant proof masses that reject shock and vibration as common-mode signals 3 .

No abstract

No abstract

No abstract

An optical fiber interferometer is described for measuring the out-of-plane displacement of microelectromechanical structures. The interferometric system has a theoretical measurement dynamic range greater than 10 8. Experimental results characterizing an electrostatically actuated polysilicon flexure beam are presented. The results are in good agreement with modeling data based on coupled boundary-element and finite-element analysis.