A novel coplanar waveguide (CPW) fed wide slot antenna for broadband circular polarization (CP) operation is proposed in this letter. Utilizing an asymmetrical ground plane and an open slot, broadband axial ratio and good impedance characteristics can be obtained in the middle and low bands. The perturbation patch on the right side of the wide slot excites the upper-band CP mode. By adjusting the upper-part feedline and the wide slot structure, the axial ratio performance can be optimized to a wideband axial ratio bandwidth (ARBW). Compared with wide slot antennas of similar size, the proposed antenna has a simpler structure while achieving a wider ARBW. The proposed antenna has been fabricated and tested. The measured results show that the -10 dB impedance bandwidth (ZBW) is 2.40-7.55 GHz (103.5%); 3-dB ARBW is 2.47-6.2 GHz (86.0%); and the peak gain is about 4 dBic. Right-hand circular polarization (RHCP) radiation pattern is achieved in +z direction. The proposed antenna can be used in WLAN/WiMAX applications and various wireless communication systems which require broadband ZBW and ARBW.
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