A Miniaturized Wideband Circularly Polarized Magneto-Electric Dipole Antenna With Wide Beamwidth Using ψ-Shaped Phase Shifter

This brief presents a miniaturized wideband circularly polarized magneto-electric dipole antenna using psi -shaped phase shifter. Its magneto-electric dipole structure utilizes four L-section patches attached to outer edges of four square patches to achieve miniaturization. A parasitic patch positioned above the dipole structure is employed as an impendence transformer to extended the bandwidth. Meanwhile, a notched cavity equivalent to four magnetic dipoles is set around the dipole structure to enhance the beamwidth. To achieve circularly polarized wave, a feeding network composed of four-order Wilkinson power divider and psi -shaped phase shifter is designed to realize two equal-amplitude outputs with 90 degrees phase difference. The psi -shaped phase shifter utilizes an open-short stub combining open circuit and short circuit, then achieving 106.9% impendence bandwidth with low insertion loss of 0.03 dB at 1.5 GHz. Then, the proposed antenna is fabricated with a compact size of 0.5 lambda(0) x 0.5 lambda(0) x 0.3 lambda(0), (lambda(0) at 1.5 GHz). The measured results show that its impedance bandwidth is 94.6% while the 3-dB axial ratio bandwidth reaches 107.1%. The maximum half-power beamwidth reaches 144 degrees/135 degrees at -45 degrees/45 degrees-plane within the band from 0.78 GHz to 2.15 GHz while maximum axial ratio beamwidth respectively obtains 182 degrees/203 degrees in -45 degrees/45 degrees-planes.