Read range enhancement of RFID tag antenna mounted on metallic plane

A novel radio frequency identification (RFID) tag antenna design mounted on metallic plane is presented in this article. The tag antenna structure is a rectangular radiating plate with a Z-shaped slot, which behaves like a half-wavelength slot resonator and a dipole-type ground radiator. For a conjugate match to the Alien Higgs-3 chip impedance of 8-j142 Ω at 925 MHz is obtained by etched a half-wavelength slot resonator in the center of the rectangular radiating plate (120 mm × 60 mm). By simply tuning the length and width of the Z-slot resonator, the tag antenna resistance and inductive reactance are easily adjusted to match the desired chip impedance. The half-wavelength resonant radiating plate (dipole-type ground radiator) is spaced from the metallic plane and enhances the antenna gain by the reflection of the metallic plane. Tests of an RFID reader with an effective isotropic radiated power of 4.0 W showed that the proposed tag antenna mountable on metallic plane has a maximum read range exceeding 10 m. Measurement data were in good agreement with simulation results.