Analysis of the Split Ring Resonator (SRR) Antenna Applied to Passive UHF-RFID Tag Design

Abstract

An electrically small planar passive UHF-RFID tag based on an edge-coupled split ring resonator (EC-SRR) antenna is presented in this work. In order to explore the potentiality and limitations of the SRR antenna and to aid the tag design, an analytical study of the SRR radiation properties at its fundamental resonance is presented for the first time. Radiation resistance, efficiency, polarization, bandwidth, and impedance matching with the radio-frequency identification (RFID) application-specific integrated circuit (ASIC) are treated in the study. Based on such analysis, the tag design process is presented, and a tag prototype of size 30 mm × 30 mm (λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> /11 × λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> /11) is designed to operate in the North-American UHF-RFID band (902-928 MHz) and manufactured. The measured read range is in good agreement with the simulation and reaches 9.3 m at 911 MHz. The tag also features a mitigation of the blind spots, providing a minimum measured read range of 4.2 m.