A Capacitively Coupling Multifeed Slot Antenna for Metallic RFID Tag Design

This letter describes a capacitively coupling multifeed slot antenna, which is comprises a slot radiator and a small dipole coupling source for metallic plate radio frequency identification (RFID) tag design. The features of the design is that the tag can function effectively with three different RFID chips, whose impedances vary widely, and the design of the conjugate impedance match of the RFID tag can be easily achieved. The important advantages of the design are that the tag does not have to be redesigned to work with different RFID chips, and additionally, the indirect coupling mechanism helps solve the mounting issue encountered in the process of mass production of the RFID tag. The experimental tests carried out with tags in which the TI, Alien-H2, and Alien-H3 chips were incorporated show that the maximum read ranges we can achieve are 1.2, 2.8, and 4.2 m, respectively, which has been tested for an RFID reader with only 0.5 W of EIRP. The letter shows that the simulated and measured results are shown to be in good agreement with each other.