Using the zeroth order resonance of an inter‐digital capacitive unit‐cell to design antennas for passive UHF RFID tags

Abstract

Abstract Meander‐line and multi‐layer antennas have been used extensively to design compact UHF radio‐frequency identification (RFID) tags; however the overall size reduction of meander‐line antennas is limited by the amount of parasitic inductance that can be introduced by each meander‐line segment and multi‐layer antennas can be too costly. In this paper, a new compact antenna topology for passive UHF RFID tags based on zeroth order resonant (ZOR) design techniques is presented. The antenna consists of lossy coplanar conductors and inter‐connected inter‐digital capacitor (IDC) unit‐cells with a ZOR frequency near the operating frequency, which is a key component in the design process because the unit‐cells chosen for the design are inductive at the operating frequency. This makes the unit‐cells very useful for antenna miniaturization. The new design in this work has several benefits; namely the coplanar layout can be printed on a single layer, matching inductive loops that reduce antenna efficiency are not required and ZOR analysis can be used for the design. Finally, for validation, a prototype antenna was designed with a unit‐cell ZOR resonant frequency of 900 MHz, fabricated and characterized. A maximum read‐range of 7.6 m was determined.

Keywords

• Waveguide and microwave transmission line components
• Single antennas
• RFID systems
• Metamaterials and structures (microwave)