A UHF RFID antenna using double-tuned impedance matching for bandwidth enhancement

Abstract

A broadband ultra-high-frequency (UHF) Radio Frequency Identification (RFID) antenna using double-tuned impedance matching theory is proposed. This paper presents a proximity coupled vertical meandered strip feed technique based on double-tuned impedance match which results in a wide bandwidth. This antenna mainly consists of a rectangular ground plane, a U-shaped radiation patch, and a suspended vertical meandered strip (VMS) by mesas of rotated Γ-shaped strip. The Ushaped radiation patch is fed by the VMS. The simulated and measured results show that the antenna has a very wide impedance matching bandwidth of 150 MHz (820-970 MHz) or 16.8% with the voltage standing wave ration (VSWR) less than 1.5 and achieves a high gain level about 8.5 dBi. Therefore, the proposed antenna can cover the entire UHF band of 840-960 MHz and is a good candidate for universal UHF RFID applications.