High chip reactance matching for ultra-high-frequency radio frequency identification tag antenna design

This study describes a high impedance-matched dipole antenna, which is composed of an inductive T-loop and a small bent dipole radiator with a slit for ultra-high-frequency (UHF) radio frequency identification (RFID) tag design. Simple adjustments of the T-loop and dipole radiator of the antenna allow for easy control of the antenna resistance and inductive reactance, from which a high chip reactance (or high Q -factor) requirement may be readily satisfied. For a conjugate match to the FEC-MM Gen2 microchip impedance of 46- j 796 at 915 MHz, a compact (36 mm 28 mm) tag antenna with a Q -factor of 17 was designed. The T-loop coupling mechanism can excite two resonance modes with reactance match to enhance the impedance bandwidth for solving the relative high Q -factor of the RFID tag. The fabricated tag sensitivity of about -3.5-dBm, read range of 2.4-m on the x - z and y - z planes and measured orientation radiation patterns were obtained in the desired frequency band.