UHF near-field RFID reader antenna with capacitive couplers

A segmented loop antenna with capacitive couplers is proposed for ultra-high frequency (UHF) near-field radio frequency identification (RFID) applications, which is capable of generating a strong and uniform magnetic field in a near-field zone even though the perimeter of the loop is comparable to the operating wavelength. As an example, an antenna printed onto an FR4 printed circuit board with an interrogation zone of 154 × 154 mm exhibits good impedance matching and uniform magnetic field distribution over an operating bandwidth of 790-1000 MHz, which is desirable for UHF near-field RFID reader applications.