An UHF reader antenna design for near-field RFID Applications

In this paper, two UHF reader antennas based respectively on inductive and capacitive couplings for near-field RFID applications are presented. To identify item-level tags with inductive coupling, a loop-type antenna is developed to have strong magnetic fields in near zone. As for the capacitive coupling, a near-field focusing circular patch array fed by a network with various input phases for radiation elements is proposed to enhance the electric field in near zone. Thus, dipole-like tags can be recognized with the capacitive coupling. Measurements show that those antennas operating with commercial readers provide good performance of tag identifications for near-field RFID applications with inductive and capacitive couplings, respectively.