Rhombic Split Ring Resonator (R-SRR) RFID tag for UHF band

Abstract

Radio frequency identification (RFID) in the UHF band and its supporting communication technology has received increasing research interest recently. RFID has several benefits over the conventional method of identification, such as a higher reading range, faster data transfer, and ability to simultaneously read a massive amount of tags. An RFID tag consisting of a microchip and an antenna is an important part of an RFID system. Proper impedance matching between the antenna and the chip is crucial in achieving good read range for the RFID tag. Many modified forms of dipoles with T-match network are reported for RFID tag antennas. Recently Split Ring Resonator (SRR) consisting of two concentric rings separated by a gap and splits on the opposite sides of the rings are incorporated in the RFID tag design. In this paper design and development of an RFID tag based on a dipole antenna with T-mach network whose arms are loaded with a Rhombic Split ring resonator (R-SRR) to operate in the European UHF RFID band of 865–867MHz is reported. The R-SRR loaded in the arms of the dipole tag reduces the overall size and produce inductive input impedance required for conjugate impedance matching with the chip. A chip of impedance 27 − j212Ω at 866MHz is connected at the terminals of the proposed antenna. The CST microwave studio is used for tuning the R-SRR parameters and a T-matching network is implemented in the antenna design to get impedance matching and miniaturization. The read range measurements are carried out with an STA IR0507E reader with a receiver sensitivity of −80dBm and RF power of 28dBm with circularly polarized antennas and a maximum read range of 7.4m is obtained. The proposed UHF tag exhibits appreciably good read range over the entire azimuth and elevation angular ranges.