Low-Profile, Dual-Band, Unidirectional RFID Tag Antenna Using Metasurface

In this paper, a low-profile, dual-band, unidirectional, tag antenna is proposed for ultrahighfrequency band (UHF) radio frequency identification (RFID) applications. The antenna consists ofa compact printed dipole, a metasurface of 4 × 4 periodic metallic plates, and a metallic reflector. Thedipole antenna is fed by a modified T-matching network for a conjugate impedance matching with theUCODE G2XM chip. The metasurface is designed to work as an artificial magnetic conductor surface,which allows low-profile configuration and unidirectional radiation. More interestingly, the finite-sizedmetasurface generates extra resonance for the antenna system, which is combined with dipole resonancefor the dual-band operation. For an easy realization and low cost, the dipole and metasurface are builton the top and bottom sides of a thin FR-4 substrate, respectively. The final design with overall size of190mm × 190mm ×15.8mm (0.532λ ×0.532λ ×0.044λ at 840 MHz) yields a simulated |S11| < −10 dBbandwidth of 840–855 MHz and 916–932 MHz and a unidirectional radiation with a directivity of 7.0 dBand 5.8 dB at 925MHz and 845 MHz, respectively. The antenna has been fabricated and tested. Themeasured readable range agrees rather closely with the predicted values. The measurements result inthe maximum readable range of 6-m and 4.4-m at standard frequency bands of FCC (902–928 MHz) forNorth America and IN (840–845 MHz) for India, respectively. © Progress In Electromagnetics Research C. All rights reserved.