Stub-Loaded Uniplanar Monopole Antenna for Circular Polarization

This paper presents a circularly polarized stub-loaded inverted L-shaped planar monopole antenna. Circular polarization (CP) is achieved with the help of stubs attached to the inverted L-shaped radiator. The proposed antenna provides circular polarization with good impedance matching over a broad frequency range of (7.8 - 8.5 GHz). Further, the antenna shows right hand circular polarization (RHCP) with a cross-polar difference (XPD) of more than 20 dB, slightly directional radiation pattern, peak realized gain of 3.7 dBi, and radiation efficiency of more than 90 % over coinciding impedance bandwidth (IMBW) and axial ratio bandwidth (ARBW) of 8.6 % which makes antenna useful for X-band applications. The proposed antenna has very simple geometry and is excited with coplanar waveguide (CPW) feed which makes it uniplanar, low-profile, and cost-effective. In addition, the sense of CP can be changed from RHCP to LHCP by the mirror-image configuration of the proposed antenna.