A 5.1μW RFID tag chip integrated with sensors for wireless environmental monitoring

Abstract

An RF-powered transponder with temperature and photo sensors is designed and fabricated for environmental monitoring. The transponder gathers power from external ISM (860-960MHz) band RF signal and senses ambient temperature and light. It contains a supply voltage generator, a temperature-compensated ring oscillator, an oversampling synchronizer, a PTAT temperature sensor and an abrupt transition buffered photo sensor. Its internal clock frequency has variation less than 7% for 1.5-V supply voltage and 90/spl deg/C temperature change. The transponder occupies 0.4mm/sup 2/ with 0.25-/spl mu/m CMOS process and dissipates only 5.14-/spl mu/W during active state.