Wi-Fi RF energy harvesting for battery-free wearable radio platforms
- 1 April 2015
- conference paper
- conference paper
- Published by Institute of Electrical and Electronics Engineers (IEEE) in 2015 IEEE International Conference on RFID (RFID)
Abstract
Wearable devices have huge market potential, but their usage has been limited because means to power such devices is still a challenge. Batteries, the most widespread solution, add size, weight and need periodic recharging which is a huge deterrent. In this work, we propose to eliminate batteries by leveraging Wi-Fi transmissions from nearby devices such as access points and smart phones to deliver power wirelessly to wearable devices. We develop a wearable temperature sensor, which harvests energy from Wi-Fi transmissions and transmits data back to an access point. We enable this application by designing an efficient 2.4 GHz Wi-Fi harvesting front-end to power an ANT radio platform with a smartphone as the Wi-Fi source. We study and analyze the effect of OFDM modulation, wide bandwidth (72 MHz) and the bursty nature of 802.11 Wi-Fi signals on the sensitivity, efficiency and the output power of the RF harvester. Our prototype achieves a sensitivity of -16.5 dBm with 100 % duty cycle Wi-Fi transmissions for a target output voltage of 2.05 V and 2.5 μW leakage at the storage capacitor node. This translates to an operating range of about 11.5 cm from a 2 dBm Wi-Fi transmitter on a smartphone and 92 cm from a 20 dBm Wi-Fi access point with a 3 dBi antenna on the wearable device.Keywords
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