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A cavity backed segmented loop antenna is proposed for ultra high frequency (UHF) near-field radio frequency identification (RFID) readers. The induced current along the cavity edges shows significant effect on the impedance matching and magnetic field distribution of the segmented loop antenna. A backed cavity with optimized dimensions enables the antenna generating stronger magnetic field so that the reading range is enhanced. The reading range of an antenna prototype with a cavity of optimized dimensions of 234 mm × 234 mm × 51 mm is increased by 7 mm compared to that of the segmented loop antenna without any cavity.