Abstract
To avoid performance fluctuation of radio frequency identification (RFID) system while the tag is attached on objects with different materials, a platform-tolerant UHF RFID tag antenna with stable high gain is proposed in this paper. The antenna is composed of an upper layer feeding loop and a lower layer planar dipole. Inductively coupling approach is adopted to feed, so that large mutual inductance could be introduced into the incident impedance of antenna, which enables great match between RFID chip and antenna. The coupling feeding method can also significantly decrease the impact on antenna impedance due to the introduced parallel capacity between radiation plane and platform. The realized results show that the antenna has an impedance bandwidth (S11<−18dB) of 14.5% (840–975MHz) and a stable gain with peak value of 2.34dBi. Moreover, it is immune to influence of platforms which is validated by experiments using a 30×20cm2 plate of aluminum, paper, copper, glass and air to be the platform, during these experiments the antenna gain varies less than 1dB. Compared with other cavity backed antenna or AMC, EBG based antenna, the antenna proposed in this paper has higher gain with an extremely simple structure which performs significant advantage for mass production.
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