Miniaturized Circularly Polarized Microstrip RFID Antenna Using Fractal Metamaterial

Abstract

A novel miniaturized circularly polarized (CP) microstrip antenna that can handle UHF band (920–925 MHz, corresponding to the assigned band for RFID in China) has been designed, fabricated, and measured in this paper. The miniaturization of antenna is achieved by a special cross-shaped fractal metamaterial structure that is inserted between the patch and ground plane. The measured results show that the antenna possesses an impedance bandwidth of 8.7% with VSWR 1.5 : 1 and 3-dB axial bandwidth of 3.8%. Furthermore, the proposed antenna has 10.2% size reduction compared with traditional patch antenna. The tested results are in good agreement with that of the simulations.