A Self-sustained Wireless Sensor System for Environmental Monitoring

• Main Authors: Wen, Fu-Chun, 溫富鈞
• Other Authors: Liao, Yu-Te
• Format: Others
• Language: en_US
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/62281266298225681441

碩士 === 國立中正大學 === 電機工程研究所 === 101 === With advanced silicon technology, electronics devices become powerful, robust, and miniaturized. Integrating sensor and electronic interface circuits on single chip can enable many new applications, such as cochlear implant and biometrics. In addition to the integration technology, the energy source is usually the major limits for the wireless sensor applications. The thesis is dedicated to designing low power sensor interface circuitry for the applications with only constrained energy source. Chapter 2 presents a 26nW regulator with settling enhancement and low voltage bandgap circuitry to solve the issue of slow transitions in ultra-low power electronics design. A feedback loop is employed in the bandgap reference to enhance the startup speed. Comparing to conventional regulator, the proposed regulator improves settling time 40X at the same power consumption while providing -33dB power supply rejection. The chip was fabricated in a 90 nm CMOS process. The regulator only occupies an active area of 0.3 x 0.5 mm2 and consumes 26nW. Chapter 3 describes a wireless moisture and temperature monitoring system for plant care and sophisticated agriculture. The proposed system harvests energy from environment, avoiding frequent battery replacement. To provide a stable energy source, hybrid energy scavenger including RF power and soil cells is used in our system. Soil energy is a kind of green energy. Comparing to solar and tidal energy, soil energy is easily accessible and stable. A soil-powered monitoring system is first demonstrated on a PCB. The system includes a microcontroller, DC-DC converter, micro LCD display. The system can acquire temperature and moisture data every 80 seconds. For precision measurement, the sensor system is supposed to be placed close to the target. An integrated sensor platform, including power management, sensor readout circuits and wireless communication circuitry, was designed and fabricated in 90nm CMOS technology. Three measurement modes are implemented in the sensor platform for moisture, temperature, and PH value monitoring. The modes can be controlled by communication with remote interrogators. Furthermore, the sensor system can wirelessly transfer data to the external reader with a backscattering communication scheme. The chip occupies an area of 1 mm2 and only consumes 1.2 µW.