An Electrically Large Zero-Phase-Shift Line (ZPSL) Dual-Loop Antenna with Inset Feeding structure

Abstract

A zero-phase-shift line (ZPSL) dual-loop antenna with inset feeding configuration is designed for applications of ultra-high frequency (UHF) near-field radio frequency identification (RFID). Designed on 0.5 mm thick FR4 substrate, the ZPSL dual-loop antenna achieves a uniform magnetic field distribution within an interrogation area of 400 mm ×400 mm (perimeter of 1600 mm, 4.88$\lambda$ at 915 MHz). The antenna is measured with $\vert$ $S_{11}$ $\vert$ smaller than 10 dB in a wide range of frequencies 850-1060 MHz, achieving a 100% reading range up to 15 mm (with an Impinj reader of 1W output power, Sag tag).