FRACTAL-BASED TRIANGULAR SLOT ANTENNAS WITH BROADBAND CIRCULAR POLARIZATION FOR RFID READERS

Equilateral-triangular slot antennas with modifled edges for wideband circular polarization are proposed in this paper. Circular polarization was flrstly obtained by adding two asymmetric perturbations to two edges of triangular slot. Then fractal-like boundaries were adopted in the antenna design for size reduction and broadband operation. Two antenna prototypes for RFID readers were fabricated to cover RFID UHF band and ISM 2.4GHz band, respectively. Measured results show that the presented antennas obtain fairly wide 3-dB axial ratio bandwidths of 15.7% (820{960MHz) and 19.8% (2.18{2.66GHz).