Yao Zhu; Yuanjin Zheng; Yuan Gao; Made, D.I.; Chengliang Sun; Minkyu Je; Gu, A.Y., "An Energy Autonomous 400 MHz Active Wireless SAW Temperature Sensor Powered by Vibration Energy Harvesting," Circuits and Systems I: Regular Papers, IEEE Transactions on , vol.62, no.4, pp.976,985, April 2015 doi: 10.1109/TCSI.2015.2402937
Abstract:
An energy autonomous active wireless surface acoustic wave (SAW) temperature sensor system is presented in this paper. The proposed system adopts direct temperature to frequency conversion using a lithium niobate SAW resonator for both temperature sensing and high-Q resonator core in a cross-coupled
RF oscillator. This arrangement simplifies the temperature sensor readout circuit design and reduces the overall system power consumption. A power conditioning circuit based on buck-boost converter is utilized to provide high efficiency power extraction from piezoelectric energy harvester (PEH) and dynamic system
power control. The SAW resonator is fabricated in-house using a two-step lithography procedure while the RF oscillator as well as the PEH power conditioning circuit are implemented in standard 65-nm and 0.18- CMOS processes respectively. The measured RF transmitter output power is 15 dBm with a phase noise of
99.4 dBc/Hz at 1 kHz offset, achieving a figure of merit (FOM) of 217.6 dB. The measured temperature sensing accuracy is 0.6 in 40 to 120 range. Fully powered by a vibration PEH, the proposed energy autonomous system has a self-startup voltage of 0.7 V and consumes an average power of 61.5 .
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