UHF RFID antenna structure with high isolation characteristic

In this paper, we have proposed a compact passive UHF radio frequency identification (RFID) reader antenna which have high isolation characteristics, which consists of two quadruple inverted-F antennas (QIFAs) and the feeding networks. The high isolation can be achieved by two concentric, circularly polarized antennas and 4-point feed circuits, which make the same circular polarization. The simulated and experimental results show that the transmit/receive isolation is more than 50 dB and the gains of two QIFAs are 1.5 dBi for the transmitter and 1.4 dBi for receiver at the 910 MHz, respectively.