Improved broadband circularly polarized cross dipole with multiple circular parasitic ring resonators

A printed cross dipole antenna with parasitic ring resonators is proposed. The proposed antenna achieves both a broadband axial ratio and broadband impedance bandwidths. It consists of cross dipole with 90° phase delay line. This results in having one minimum axial ratio point due to the sequential arms rotation. In addition to that, the parasitic rings produce the other minimum axial ratio point. Therefore the cross dipole in combination with the parasitic ring resonators achieve broadband axial ratio and broadband impedance bandwidths. The resulted broadband axial ratio bandwidth ranges from 1.87 GHz to 2.86 GHz with fractional bandwidth of 42 %. While the broadband impedance bandwidth ranges from 1.588 GHz to 2.936 GHz with fractional bandwidth of 59.6 %. This paper presents the design of the proposed cross dipole antenna with the parasitic ring resonators, the simulated and measured results.