Multi-Port UHF RFID tag antenna for enhanced energy harvesting of self-powered wireless sensors

In this paper, a multi-port RFID tag antenna is integrated with an I2C-RFID chip along with a microcontroller unit (MCU) and a sensor to implement a low-cost wireless temperature sensor using a commercial RFID reader. The key feature of this design is a two-port patch antenna with energy-harvesting circuitry at its second port, which can acquire the supply voltage needed for the operation of RFID tag sensor from the RF signal transmitted by the reader. In addition, a secondary method of energy harvesting is included by integrating thin film solar cells in the RFID tag profile. The measurements of the fabricated tag-based sensor demonstrate that a maximum sensing/reading range of 27 m is achieved when all the circuits are powered using solar cells. When the tag is operated as a simple RFID tag with no energy harvesting employed to power up the passive RFID chip 12.1m reading range is obtained.