A Compact UHF-RFID Tag Antenna Based on PIFA Structure for Two-Side Anti-Metal Application

Based on the Planar Inverted F-shaped Antenna structure, we propose a two-side anti-metal tag antenna for ultra-high frequency radio frequency identification. The chip of the proposed tag antenna is housed within a square slot of FR4 material. Three gaps can be observed on the surface of the proposed tag antenna. As a result of these gaps, the resonant frequency can be adjusted with flexibility in order to ensure an optimal power transmission coefficient and impedance matching. The proposed tag antenna maintains a compact size of
$\boldsymbol{{40}\times 28\times 3.2 \ \text{mm}^{3}}$
. The proposed tag antenna is measured by placing it on a metal plate, resulting in 5.2 m and 5 m read distances, respectively. The proposed tag antenna is compact, and exhibits good performance, particularly with its two-side anti-metal characteristics.