Design of UHF RFID broadband anti-metal tag antenna applied on surface of metallic objects

A radio frequency identification (RFID) tag antenna mountable on metal surfaces is designed. It operates in the UHF frequency band (usually called UHF RFID tag) and is matched to the Alien Higgs-3 chip (a kind of RF IC chip). Based on the special structure of the microstrip antenna-two conducting surfaces: the antenna plane and the ground plane, we embed a pair of E-type slot to obtain broadband characteristics and use a short-circuited stub feed in the antenna plane. The antenna impedance is conveniently matched to the complex conjugate of the RF IC chip impedance so as to achieve good power transfer from the antenna to the RF IC chip. The simulation and practical measurement results show that the proposed anti-metal tag antenna structure is simple and the antenna bandwidth reaches 250 MHz when the return loss S11 is less than 10 dB. Also, the proposed antenna has good radiation pattern and gain.