A Novel Miniature Circular Eye-Inspired UHF RFID Tag Antenna Design

This paper introduces a novel miniature structure of Tag UHF RFID antenna, specifically designed for use on metallic objects within the European frequency bandwidth of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$865-868 \text{MHz}$</tex>. The proposed Tag antenna is a circular structure Eye-inspired designed to match the configuration of a folded dipole antenna. It incorporates a default T-Match network, which ensures flexible conjugate input impedance matching between the antenna and the chip. The RFID chip used is an Alien H4 having an input impedance around <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$Z_{c}=23.27-\mathrm{j} 203.35 \Omega$</tex> at 868 MHz, this chip used due to its reading sensitivity of −20.5 dBm. The final proposed antenna is mounted on a substrate Rogers RO 4350 B having a thickness of 1.524 mm, with a dielectric constant <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\varepsilon_{r}=3.66$</tex> and a loss tangent <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\tan \delta=0.0037$</tex>.