Planar Broadband Tag Antenna Mounted on the Metallic Material for UHF RFID System

A novel broadband design of planar tag antenna mounted on the metallic objects for the UHF radio frequency identification (RFID) system is proposed. We derive a new resonant mode that is excited with frequency shifting to enhance the operating bandwidth for broadband operation by employing the shorting pins posted at the corner of the proposed tag antenna. The obtained impedance bandwidth across the operating band can reach about 112 MHz (12.5%) for the UHF band, which is from 850 to 962 MHz. Also, with unidirectional pattern, the measured reading distance is about 5.2 m as the proposed tag antenna mounted on the metallic object.