Low-profile folded dipole UHF RFID tag antenna with outer strip lines for metal mounting application

Abstract

A metal mountable UHF RFID tag antenna with a low-profile folded dipole structure is proposed. It is fabricated on a single layer of polytetrafluoroethylene (PTFE) dielectric laminate. It is composed of two symmetrical C-shape resonators integrated with the outer strip lines. The IC chip's terminals are connected directly to the center of the C-shaped resonators. The outer strip lines are integrated with the C-shaped resonators, which function to lower the reflection coefficient so as to match the IC chip impedance. In particular, the outer strip lines increase the inductive reactance of the antenna impedance in order to realize IC chip impedance. The design has a simple structure, due to the fact that it lacks any metallic vias. Moreover, the gain of the tag antenna can be enhanced when positioned on a large metallic sheet. Installed on a $40$ $\times$ $40$ $cm^{2}$ metallic plate, the total gain of the proposed tag antenna is $3$ dB, with a maximum reading range of $5.77$ m, while it is $3.92$ m in free space. The simulation results were in excellent agreement with the fabricated design results.