A Dual-Circularly Polarized Wideband Dipole Antenna With Stable Axial-Ratio and Half-Power Beamwidths

With wide impedance bandwidth (IBW), wide axialratio bandwidth (ARBW), stable AR beamwidth, and stable halfpower beamwidth (HPBW), a dual-circularly polarized (DCP) crossed-dipole antenna is proposed. Each dipole consisting of two patches is fed by a pair of parallel transmission lines, leading to a wide IBW. To enhance the ARBW and AR beamwidth, a quadrature wideband coupler is used, and the overlapping bandwidth of IBW and ARBW is up to 100%. The quadrature coupler is integrated with two pairs of parallel transmission line, and are printed on two substrates, which are squeezed into the space between the radiators and reflector, resulting into a compact antenna structure. With a total height of 0.016 lambda(L), a prototype is fabricated and measured, showing 1.5-VSWR IBW of larger than 104% for both left-handed CP (LHCP) and right-handed CP (RHCP), 3 dB ARBW of up to 100% both for LHCP and RHCP, and port-to-port (polarization) isolation of lager than 30 dB in 1.70-2.82 GHz, so the effective bandwidth is about 50% (1.70-2.82 GHz). 3 dB AR beamwidth of 76 degrees +/- 5 degrees, stable DCP characteristics with average gain of 7.2 dBi and HPBWs of 67 degrees +/- 4 degrees are achieved.