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High-Performance Wireless Microsystem for MEMS Capacitive Strain Sensors
Suster, Michael August

2011, Doctor of Philosophy, Case Western Reserve University, EECS - Electrical Engineering.
High-performance wireless microsystems consisting of MEMS sensors and low-power integrated circuits are crucial for applications such as the monitoring of biomedical signals, environmental monitoring, and advanced automotive and industrial sensing applications. These applications demand batteryless operation due to size and operation lifetime constraints. High-performance industrial sensing applications further impose design challenges due to the large signal bandwidth and dynamic range demanded for these applications. This work presents a complete stand-alone wireless microsystem for industrial strain sensing applications, such as point-stress and torque sensing for ball-bearings and rotating shafts and blades. The proposed microsystem consists of a MEMS capacitive strain sensor and integrated capacitive interface electronics with wireless powering and data telemetry capability. A prototype wireless strain sensing microsystem has been fabricated and tested. A capacitive differential MEMS strain sensor employs mechanical amplification through bent beam suspensions to achieve a sensitivity of 283 aF/microstrain. The sensor is wire-bonded to an IC consisting of a low-noise continuous-time synchronous-detection capacitance-to-voltage (C/V) converter and 2nd-order sigma-delta analog-to-digital converter (ADC) to digitize the strain information for reliable wireless data transmission. An on-chip temperature sensor and 1st-order sigma-delta ADC is included for system calibration. The microsystem is powered by a 51.2 MHz RF signal through an on-chip RF-DC converter and can simultaneously transmit two channels of digitized strain and temperature data over the RF powering link by passive phase shift-keying (PSK) and amplitude shift-keying (ASK) modulations, respectively, and a comparator generates the system timing clock from the incoming RF signal. The strain sensing microsystem exhibits a maximum DC input strain range of ±1000 microstrain, with an overall sensitivity of 816 mV/microstrain and 5.2% nonlinearity full-scale. Based on system noise characterization, the prototype design exhibits a strain resolution of 0.05 microstrain over a 10 kHz bandwidth. The temperature sensor exhibits a sensitivity of 3.8 mV/C from 25 °C to 150 °C with a resolution 0.01 °C due to electronic noise. The strain and temperature information are simultaneously telemetered to an external receiver at 2.56 Mbps and 128 kbps, respectively. The PSK and ASK channels are tested with a bit error rate of less than 10-7 The overall system consumes 2 mA from a 3V supply and occupies an area of 3 mm x 7 mm.
Darrin Young (Advisor)
Wen Ko (Committee Member)
Francis Merat (Committee Member)
Dominique Durand (Committee Member)
114 p.

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Suster, M. (2011). High-Performance Wireless Microsystem for MEMS Capacitive Strain Sensors. (Electronic Thesis or Dissertation). Retrieved from https://etd.ohiolink.edu/

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Suster, Michael. "High-Performance Wireless Microsystem for MEMS Capacitive Strain Sensors." Electronic Thesis or Dissertation. Case Western Reserve University, 2011. OhioLINK Electronic Theses and Dissertations Center. 16 Dec 2017.

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Suster, Michael "High-Performance Wireless Microsystem for MEMS Capacitive Strain Sensors." Electronic Thesis or Dissertation. Case Western Reserve University, 2011. https://etd.ohiolink.edu/

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