A dual-broadband circularly polarized (CP) antenna with compact structure 97 × 97 × 0.8 mm3 is proposed. The measured -10 dB return loss bandwidth is 0.38 GHz (0.75-1.13 GHz) for UHF band and 0.81 GHz (2.32-3.13 GHz) for ISM 2.4 GHz band. The measured 3 dB axial ratio bandwidth is about 0.235 GHz (0.83-1.065 GHz) for UHF band and 0.34 GHz (2.36-2.7 GHz) for ISM band. The antenna consists of a feedline, patch, Stepped slot-1 and -2, a pair of orthogonal rectangular slots (H/V slot), and L-slot. There are two advantages for the proposed antenna: broadband and independent adjusting for UHF and ISM 2.4 GHz bands. The proposed antenna is a good candidate for worldwide RFID reader antenna.
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