DefinePK

Abstract

This article describes a tag antenna fed by an inductively coupled technique for Radio Frequency Identification (RFID) applications. The folded stepped-impedance resonator (SIR) is used for the feed structure while the split ring resonator (SRR) is used as radiating dipole arms. An equivalent circuit model for the inductively coupled tag antenna is given to synthesize the tag antenna system with an RFID chip. The simultaneous use of SRR and SIR resonators provide flexible tuning in terms of antenna impedance and easier to miniaturize the prototype. It is printed on an epoxyFR4substrate at the vey compact size of44×44×1.6 mm3. It is designed using Murata IC chip having an impedance of 25-j200 Ohm at center frequency of 915 MHz. The experiment yields result of the impedance bandwidth is 35 MHz (901-936 MHz, 3.8%), which operates within the standard UHF frequency band. Furthermore, the results showed that the peak gain of the proposed tag antenna is -1.4 dBi with radiation efficiency higher than 58% at the center frequency of 915 MHz. It provides an Omni directional radiation pattern with a maximum measured read range of 3.18 meters at the resonant frequency of 915 MHz with an effective isotropic radiated power (EIRP) of 4.0 W. The measurement results agree with the simulated ones. Consequently, the proposed prototype offers attractive benefits for RFID applications.