Low Profile Planar Inverted-L Antenna (PILA) for UHF RFID on Metal-Tag

A novel planar inverted-L antenna (PILA) for a UHF RFID tag mounted on metal is introduced in this study. By loading a via in every patch to form eight PILA structures, the designed antenna is miniaturized to an overall size of 25 $\times 20 \times 3.2\mathrm{m}\mathrm{m}^{3}$. In this design, the PILA is inductively excited by coupling adjacent patches, allowing for more flexible adjustment of reactance on a large scale. Additionally, the gaps between the coupled patches enable precise control of the antenna input impedance’s capacitance, perfectly matching the Monza 6 chip impedance (10.5-jl34 $\Omega$ at 915 MHz). The measured reading distances with and without a backing metal object were 6.7 and 7.8 m, respectively. These results indicate that the proposed antenna is a promising choice for applications involving metallic objects, particularly in scenarios where size reduction is a priority.