A Compact and Broadband Circularly Polarized Printed Monopole Antenna for UHF RFID

In this paper, a compact and broadband printed monopole antenna for circular polarization (CP) is proposed. The miniaturization is achieved by inserting an elliptical notch to the rectangular patch. Moreover, the broadband circular polarization is achieved by designing the antenna asymmetrically to the microstrip line. Finally, the antenna for ultrahigh frequency (UHF) radio-frequency identification (RFID) is designed by using the proposed antenna. The bandwidth of the 10dB-return loss with a 3dB-axial ratio is from 783MHz to 1132MHz (36.4%). The antenna size is 0.51 wavelength $\times$ 0.41 wavelength at the center frequency.