Design of a Circularly Polarized Tag Antenna for Increased Reading Range

We introduce a novel circularly polarized tag antenna, consisting of a truncated patch, a shorting plate, and a ground plane, to increase the reading range while remaining in compliance with EIRP regulations. The reading range of the proposed tag is twice that of linearly polarized tags, due to the decreased polarization mismatch between the reader and tag antennas. An additional parasitic patch is loaded onto the structure to boost the reading range in the UHF RFID band. As a result, an average reading range of 8 m is achieved between 860 MHz and 960 MHz, compared to a range of about 3 m with conventional dipole tags.