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 Ψ-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 Ψ-shaped phase shifter is designed to realize two equal-amplitude outputs with 90∘ phase difference. The Ψ-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 0.5λ0×0.5λ0×0.3λ0 (λ0 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∘/135∘ at -45∘/45∘ -plane within the band from 0.78 GHz to 2.15 GHz while maximum axial ratio beamwidth respectively obtains 182∘/203∘ in -45∘/45∘ -planes.