Compact Planar Inverted-S Antenna With Embedded Tuning Arm for On-Metal UHF RFID Tag Design

Abstract

A planar inverted-S antenna (PISA) is proposed for designing a compact ultrahigh frequency (UHF) radio frequency identification (RFID) tag for on-metal applications. For the first time, a U-shaped arm is embedded into the middle layer of the tag structure for effectively miniaturizing the footprint. Here, a serpentine patch is tactfully placed on top of the U-shaped arm to achieve a higher level of miniaturization. A compact UHF tag ( $25\,\,\text {mm} \times 25\,\,\text {mm} \times 3.2\,\,\text {mm}$ ), with a good power transmission coefficient of 99.7% and a long read distance of greater than 11 m, has been successfully demonstrated. It is also shown that our tag size can be further reduced to $15\,\,\text {mm} \times 15\,\,\text {mm} \times 3.2\,\,\text {mm}$ by simply adjusting the geometrical parameters, without sacrificing the power transmission coefficient much. With reference to a 4 W EIRP reader output power, the proposed tag antenna can be read from 11.9 m. For the tag with a footprint of $15\,\,\text {mm} \times 15\,\,\text {mm}$ , the read range is estimated to be at least 7 m.