Planar metallic tag antenna for UHF RFID system

A novel broadband design of planar tag antenna mounted on the metallic objects for UHF 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 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.