UHF-RFID tag antenna using T-matching and double-ended rectangular loop techniques for wristband applications

This paper presents the UHF-RFID tag antenna applied on a human body (wrist). The proposed tag antenna was fabricated on a thin FR4 substrate (εr= 4.3) with the thickness of 0.25 mm. The T-matching and double-ended rectangular loop techniques are presented to improve an antenna impedance to achieve a matching condition with the NXP G2XL IC chip with the impedance of 21.29 − j191.7 Ω, considering at the center frequency of the standard in Thailand with 922.5 MHz. The proposed tag antenna can apply for the standard of UHF-RFID in Thailand (920–925 MHz) and FCC (902–928 MHz). The radiation patterns of the tag antenna with and without wrist models are unidirectional and omnidirectional, respectively.