A Dual-Wideband Circularly Polarized Antenna Using an Artificial Magnetic Conductor

A dual-wideband circularly polarized (CP) antenna was proposed based on the strategy of combining multimode resonances. The primary radiators were two barbed-shape dipoles and two bowtie dipoles printed on the same substrate. They were placed over an artificial magnetic conductor (AMC) for the low-profile antenna design purpose. Properly combining the fundamental mode of the barbed-shape dipole, the bowtie mode, the slot mode, the second mode of a barbed-shape dipole, and extra resonance generated by the AMC surface, a dual-wideband operation can be achieved. The final design with an overall size of 0.6 lambda(o) x 0.64 lambda(o) x 0.16 lambda(o) at 2.4 GHz had measured impedance bandwidth of 40% (2-3 GHz) and 49.5% (3.8-6.3 GHz) for the lower and upper bands, respectively. The measured 3-dB axial-ratio bandwidths were 19.3% (2.25-2.73 GHz) and 33.8% (4.3-6.05 GHz) for the lower and upper bands, respectively. The antenna performed an average gain of about 6.6 dBic across the low CP region and 7.4 dBic across the high CP region.