Finger-Worn UHF Far-Field RFID Tag Antenna

This letter presents the design and measurement of an experimental passive UHF radio frequency identification (RFID) tag worn as a ring with applications particularly in healthcare or secure environments. Three sizes of rings were designed for the European UHF RFID band over two different substrates at varying heights off the skin. Designing effective body-mounted antennas for passive RFID is very challenging, particularly when mounted directly upon the skin. The rings were simulated with a commercial electromagnetic simulation software and then constructed and tested on an adult male ring finger over several angles of RF illumination so that read ranges and directivity could be determined. Main beam read distances between 2 and 5 m were achieved dependent on the ring substrate height.