Michael A. Suster

Personal Navigation via High-Resolution Gait-Corrected Inertial Measurement Units

In this paper, a personal micronavigation system that uses high-resolution gait-corrected inertial measurement units is presented. The goal of this paper is to develop a navigation system that uses secondary inertial variables, such as velocity, to enable long-term precise navigation in the absence of Global Positioning System (GPS) and beacon signals. In this scheme, measured zero-velocity duration from the ground reaction sensors is used to reset the accumulated integration errors from accelerometers and gyroscopes in position calculation. With the described system, an average position error of 4 m is achieved at the end of half-hour walks.

A High-Performance MEMS Capacitive Strain Sensing System

This paper describes a high-performance strain sensing microsystem. The system consists of four parallel differential MEMS capacitive strain sensors with a nominal capacitance value of 440 fF, converting an input strain to a capacitance change with a sensitivity of 265 aF per microstrain (muepsiv), and low-noise integrated sensing electronics, which employ a differential continuous-time synchronous detection architecture converting the capacitive signal to an output voltage for further signal processing. Based on system noise characterization, the prototype design shows a capability of measuring a strain resolution of 0.9 nepsiv/radicHz, while demonstrating a maximum dc input stain range of 1000 muepsiv. The overall system consumes 1.5 mA dc current from a 3-V supply

An optically powered wireless telemetry module for high-temperature MEMS sensing and communication

A high-temperature, low-power silicon tunnel diode oscillator transmitter with an on-board optical power converter is proposed for harsh environment MEMS sensing and wireless data telemetry applications. The prototype sensing and transmitting module employs a MEMS silicon capacitive pressure sensor performing pressure to frequency conversion and a spiral loop serving as an inductor for the LC tank resonator and also as a transmitting antenna. A GaAs photodiode converts an incoming laser beam to an electrical energy for powering the prototype design. The system achieves a telemetry performance up to 250/spl deg/C over a distance of 1.5 m with a transmitter power consumption of approximately 60 /spl mu/W.

Low-noise CMOS integrated sensing electronics for capacitive MEMS strain sensors

This paper describes a high-performance strain sensing microsystem. A MEMS capacitive strain sensor converts an input strain to a capacitance change with a sensitivity of 26.5 aF per 0.1 /spl mu//spl epsiv/. Low-noise integrated sensing electronics, employing a continuous time synchronous detection architecture, convert the capacitive signal to an output voltage for further signal processing. The prototype microsystem achieves a minimum detectable strain of 0.09 /spl mu//spl epsiv/ over a 10 kHz bandwidth with a dynamic range of 81 dB. The sensing electronics consume 1.5 mA from a 3 V supply.

Wireless, Ultra-Low-Power Implantable Sensor for Chronic Bladder Pressure Monitoring

The wireless implantable/intracavity micromanometer (WIMM) system was designed to fulfill the unmet need for a chronic bladder pressure sensing device in urological fields such as urodynamics for diagnosis and neuromodulation for bladder control. Neuromodulation in particular would benefit from a wireless bladder pressure sensor which could provide real-time pressure feedback to an implanted stimulator, resulting in greater bladder capacity while using less power. The WIMM uses custom integrated circuitry, a MEMS transducer, and a wireless antenna to transmit pressure telemetry at a rate of 10 Hz. Aggressive power management techniques yield an average current draw of 9 μA from a 3.6-Volt micro-battery, which minimizes the implant size. Automatic pressure offset cancellation circuits maximize the sensing dynamic range to account for drifting pressure offset due to environmental factors, and a custom telemetry protocol allows transmission with minimum overhead. Wireless operation of the WIMM has demonstrated that the external receiver can receive the telemetry packets, and the low power consumption allows for at least 24 hours of operation with a 4-hour wireless recharge session.

A broadband sensor interface IC for miniaturized dielectric spectroscopy from MHz to GHz

This paper describes a broadband sensor interface IC as part of a miniaturized measurement platform for MHz-to-GHz dielectric spectroscopy. Developed in 0.35 μm 2P/4M RF CMOS, the IC measures frequency-dependent S 21 magnitude and phase of a microfluidic dielectric sensor fabricated in a thick gold-on-glass microfabrication process and loaded with a material-under-test (MUT). The IC architecture implements a broadband frequency response analysis (bFRA) method by first down-converting the sensor response signal from the RF excitation frequency to an intermediate frequency (IF) of 1 MHz using a low-noise amplifier (LNA) and active mixer, followed by down-converting the IF signal to dc using a coherent detector employing IF amplification stages with programmable gain, a passive mixer driven by in-phase (I) and quadrature-phase (Q) signals and an active-RC low-pass filter (LPF). The sensor interfaced with the IC is fully capable of differentiating among deionized (DI) water, phosphate buffered saline (PBS), ethanol and methanol in tests conducted at four different excitation frequencies of 50 MHz, 500 MHz, 1 GHz and 3 GHz. Further, dielectric readings of ethanol from the sensor interfaced with the IC at five excitation frequencies in the range of 50 MHz to 2 GHz are in excellent agreement (error <;1%) with those from using a vector network analyzer (VNA) as the sensor readout. A bulk-solution reference measurement by an Agilent 85070E dielectric probe kit interfaced with a VNA is also performed to verify proof-of-concept feasibility in conducting MHz-to-GHz dielectric spectroscopy with a miniaturized measurement platform using μL-sample volumes.

Personal navigation via shoe mounted inertial measurement units

We are developing a personal micronavigation system that uses high-resolution gait-corrected inertial measurement units. The goal of this project is to develop a navigation system that use secondary inertial variables, such as velocity, to enable long-term precise navigation in the absence of Global Positioning System (GPS) and beacon signals. In this scheme, measured zero velocity durations from the ground reaction sensors are used to reset the accumulated integration errors from the accelerometers and gyroscopes in position calculation. We achieved an average position error of 4 meters at the end of half-hour walks.

A Wireless Strain Sensing Microsystem with External RF Power Source and Two-Channel Data Telemetry Capability

A wireless strain sensing microsystem is powered by a 50MHz signal and can simultaneously telemeter both digitized strain and temperature data over the RF powering link using passive PSK and ASK modulations, respectively. The prototype system achieves a minimum detectable strain of 0.87muepsiv over a 10kHz bandwidth with a maximum input signal of plusmn1000muepsiv. The temperature sensor resolution is 0.02Cdeg rms with a 100Hz BW. The chip is fabricated in 1.5mum CMOS and dissipates 6mW

Wireless power recharging for implantable bladder pressure sensor

This paper presents a wireless power recharging system design for implantable bladder pressure chronic monitoring application. The power recharging system consists of an external 4-turn 15-cm-diameter powering coil and a silicone-encapsulated implantable spiral coil with a dimension of 7 mm × 17 mm × 2.5 mm and 18 turns, which further encloses an ASIC with a programmable charging current and logic control capability, a 3-mm-diameter 12-mm-long rechargeable battery, and two ferrite rods. The ferrite rods are employed to improve the quality factor of the implantable coil. For a constant charging current of 100 µA, an RF power of 2.4 mW needs to be coupled into the implantable microsystem through tuned coil loops. With the two coils aligned coaxially or with a tilting angle up to 30°, an external RF power of 7W or 25W is required, respectively, for a large coupling distance of 20 cm at an optimal frequency of 3 MHz.

Micro-power wireless transmitter for high-temperature MEMS sensing and communication applications

A low-power silicon-tunnel-diode-based LC-tuned oscillator transmitter is proposed for high-temperature MEMS sensing and wireless data transmission applications. The prototype sensing and transmitting module employs a MEMS silicon capacitive pressure sensor performing pressure to frequency conversion and a miniature on-board coil loop serving as the inductor for the LC tank and also a transmitting antenna. The system achieves telemetry performance up to 290/spl deg/C over a distance of 2.5 meters with a total power consumption of 110 /spl mu/W.