A Center-Fed UHF Near-Field RFID Reader Antenna with Large Interrogation Zone

A novel ultra-high frequency (UHF) radio frequency identification (RFID) reader antenna is introduced in this paper. To achieve strong and uniform magnetic field distribution over an electrically large interrogation zone, this design adopts four tapered double-side parallel striplines to feed four segmented loop structures. The measured results show that this antenna achieves the good impedance matching over the frequency range from 850 to 1050 MHz, and it produces strong and uniform magnetic field distribution with an interrogation zone of 320 mm × 320 mm. The maximum reading distance is more than 300 mm with 30 dBm input power. Moreover, the antenna can achieve more than 95% read percentage within the height of 75 mm.