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Inverted U-shaped circularly polarized quad-band antenna for wideband wireless applications

A small quad-band antenna with circular polarization is proposed in this paper. It is fed by micro-strip line with coplanar waveguide (CPW), and features an inverted-U structure in the radiating patch which provides circular polarization (CP) mode at 4.53 GHz. Two inverted-L structures embedded at the opposite corners provide another two CP modes at 3.99 GHz and 7.25 GHz. The antenna provides four bandwidths operating at 1.74GHz, 3.59 GHz, 4.28 GHz and 5.42 which have more than −10 dB reflection coefficient (return loss). The antenna also features 3 dB axial ratio and the VSWR is below 2 in the operating frequency band.