UHF reader loop antenna for near-field RFID applications

A novel reader loop-type antenna for ultra-high-frequency (UHF) near-field radio frequency identification (RFID) applications is presented. This antenna, printed on a 0.8 mm-thick FR4 substrate with a diameter of 16 cm, is composed of four curved strips and four pairs of coupled stubs, and achieves a wide impedance bandwidth from 840 to 1300 MHz. The proposed structure can make large currents along the loop so that a strong and uniform magnetic field distribution is excited in the region around the antenna. Measurements show that the antenna operating with a commercial reader demonstrates good performance of tag identification with inductive coupling for near-field RFID applications.