Multiport UHF RFID-Tag Antenna for Enhanced Energy Harvesting of Self-Powered Wireless Sensors

This paper presents the design and experimental evaluation of a long-range solar powered sensor-enhanced radio frequency identification (RFID) tag. The tag antenna is a multiport microstrip patch with an overlay of thin-film solar cells for energy harvesting. A second port is allocated on the patch antenna for supplementary energy harvesting from the RF signal transmitted by the reader. An I-2 C-RFID chip along with a microcontroller unit (MCU) and temperature and humidity sensor are incorporated into the tag design to implement a low-cost wireless sensor using a commercial RFID reader. The measurements of the fabricated RFID-tag sensor demonstrate that a maximum sensing/reading range of 27 m is achieved when all the circuits are powered using solar cells, while it is 7.48m with only the secondary option of energy harvesting. The proposed sensor with dual energy harvesting achieves both a longer range and a lifetime compared with similar battery-powered sensor-enhanced RFID tags. The RFID sensor is also evaluated in a climate chamber and the sensor data (temperature/humidity) were remotely recorded with an excellent accuracy using a commercial ultra high frequency (UHF) RFID reader. In addition, the sensor can be programmed for the temperature/humidity surveillance of sensitive items, such as those found in various supply chain and transportation applications.