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

A novel electrically large segmented dipole array antenna with reflectors for ultra-high-frequency (UHF) near-field (NF) radio frequency identification (RFID) applications is proposed in this paper. It consists of eight electrically large segmented dipoles and two reflecting plates of convex parabolic shape. Each dipole has twelve 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. Measured results showed that a strong and uniform magnetic field distribution was generated within an interrogation zone of 480 mm ෗300 mm. A broad band of approximately 117 MHz (|Sn| <-10 dB), from 843 MHz to 960 MHz was achieved, covering the ETS1 and FCC standards.