Planar Shared Antenna Structure for NFC and UHF-RFID Reader Applications

A novel shared antenna structure is presented in this communication for near-field communication and ultrahigh-frequency (UHF)-radio frequency identification (RFID) reader applications. This design is developed based on a circularly polarized gap-loaded loop antenna and then evolved to contain a two-turn coil for inductive coupling. The design procedure and the operating principles in the two scenarios are interpreted. Experimental results confirm the good performances of the proposed design with low profile and simple structure. The measured 15 dB impedance matching and 3 dB axial ratio bandwidths can fully cover the entire UHF-RFID band of 840-960 MHz. In the high-frequency band, the optimal matching circuit of the proposed structure is determined and an average transmission coefficient of 0.61 is achieved within the operating range of 50 mm.