Inverted Patch with an Inductive Loop-Shaped Feeder for On-Metal Tag Design

A low-profile tag antenna, which comprises a radiating patch and an under-loading loop-shaped feeder, is explored for on-metal applications. The proposed tag antenna has an electrically small size of 45 mm × 45 mm × 3.2 mm. The under-loading loop-shaped feeder is employed for tuning the resonant frequency, where the inductive loop is found to be effective in bringing down the tag resonance to the useful UHF band and achieving conjugate impedance matching. From the simulation, the tag antenna's read distance on metal is found to be 33 m at the resonant frequency of 918 MHz.