An ultra-high-frequency (UHF), passive RF-identification (RFID) tag typically comprises an antenna and an application-specific integrated circuit (ASIC). Most RFID tags must be attached to small objects and different surfaces, which limits the tag antenna in both size and gain. At Taiwan’s National Kaohsiung University of Applied Sciences, a UHF RFID tag antenna with dual-polarization reading patterns on safety-glass objects has been proposed by Yi-Fang Lin, Shu-An Yeh, Hua-Ming Chen, and Sue-Wei Chang.
That UHF RFID tag antenna comprises a trapezoidal loop and a dual-dipole radiator with an L-slit for omnidirectional polarized reading patterns. The orthogonal dual-dipole tag antenna with an L-slit on each dipole arm ensures a conjugate match to the Monza 3 microchip impedance of 44 – j231 Ω at 915 MHz. Antenna resistance and inductive reactance are easily controlled with simple size adjustments of the L-slit and dipole radiator. A prototype attached on a different glass read beyond 9 m. It was tested for an RFID reader with 4.0 W effective isotropic radiated power (EIRP). See “Design of an Omnidirectional Polarized RFID Tag Antenna for Safety Glass Applications,” IEEE Transactions On Antennas And Propagation, Oct. 2012, p. 4530.
