Electrically Large Segmented Dipole Array Antenna With Reflectors for UHF Near-Field RFID Applications

Abstract

A novel electrically large segmented dipole array antenna with reflectors for ultrahigh-frequency near-field (NF) radio frequency identification applications is proposed in this communication. It consists of eight electrically large segmented dipoles and two reflecting plates of convex parabolic shape. Each dipole has 12 identical parts connected by appropriate capacitive loads, which almost achieves an in-phase surface current distribution. The two plates act as reflectors to limit the strength of the NF magnetic fields outside of the reading area and to improve the impedance matching. The proposed antenna generates a strong and uniform magnetic field distribution in a finite area, which could effectively reduce the misreading rates outside of the interrogation zone. A prototype was fabricated and tested for verification. The measured results showed that a strong and uniform magnetic field distribution was generated within an interrogation zone of $480\,\,\text {mm} \times 300$ mm. A broadband of approximately 117 MHz ( $\vert \text{S}_{11}\vert dB), from 843 to 960 MHz, was achieved, covering the ETSI and FCC standards.