Planar inverted-E antenna for UHF RFID tag on metallic objects with bandwidth enhancement

A novel design of a planar compact inverted-E tag antenna mounted on metallic objects for UHF RFID systems is proposed. By insetting the slit into the upper horizontal strip of the proposed compact tag antenna, a new resonant mode close to the fundamental mode of the inverted-E antenna is excited to enhance the operating bandwidth. The obtained impedance bandwidth across the operating band can reach about 123 MHz (13.7 ) for the UHF band. Also, with directional pattern, the measured reading distance is about 2.5 m when the proposed compact tag antenna is mounted on the metallic object.