Specifically designed tag antenna based on I-Loop structure for UHF RFID applications

This paper presents the UHF RFID tag antenna designed for the operating frequency band of 920–925 MHz corresponding to the standard of UHF RFID in Thailand. The tag antenna was fabricated by using a thin FR4 substrate (εr = 4.3) with the thickness of 0.25 mm. The pattern of the tag antenna is omnidirectional. The “KMITL” text bent dipole is the technique to reduce the physical size of the tag antenna. The I-loop structure is used to improve the impedances of the tag antenna to achieve the conjugate matching with the IC chip. The impedance of the IC chip at the frequency of 922.5 MHz is 21.29 − j191.7 Ω. The maximum read range is 4.5 m.