Compact Shorted C-Shaped Patch Antenna for UHF RFID Tag Mounted on Metallic Objects

This study describes a design of a tag antenna for Radio Frequency Identification (RFID) in the Ultra-High Frequency (UHF) which allows different tuning methods to tune the antenna's impedance on metallic objects. The compact patch antenna consists of a C-Shaped resonator and a ground plane connected a small shorting wall and fed by a loop in the middle of the C-Shaped resonator. A couple of slits etched around the shorting wall and a slot etched in the center of the C-shaped resonator result in a flexible adjusting method to match a conjugating impedance with the UCODE 8/8m chip (19 - j234 Ω at 915 MHz). The optimal design with an overall size of 30 × 30 × 3 mm3 (0.092 λ0 x 0.092 λ0 x 0.0092 λ0) yields a reading range of 6.4 m for the effective isotropic radiated power (EIRP) of 4.0 W.