UHF near-field segmented loop antennas with enlarged interrogation zone

Near-field radio frequency identification (RFID) technology at ultra high frequency (UHF) bands is of increasingly interest because of its promising opportunities in item-level RFID applications. The conventional single solid-line loop antenna is unable to generate strong and uniform magnetic field within an electrically large interrogation zone at the UHF bands. Segmented loop antennas are promising for UHF near-field RFID applications since they are able to generate uniform and strong magnetic field in an electrically larger interrogation zone. The reported segmented loop antennas have been able to offer an interrogation zone with a perimeter of around two operating wavelengths. In this paper, the segmented loop antennas with enlarged interrogation zone are presented. Using dual or multiple segmented loop configurations, the perimeters of the interrogation zone of the antennas can be larger than three operating wavelengths at the UHF bands.