An Improved Ultra-Wideband Circularly Polarized Cross-Dipole Antenna

In this paper, a broadband Circularly Polarized (CP) cross-dipole antenna is proposed. And it can be divided three layers. The top layer is composed of a pair of crossed-dipoles and four parasitic rectangular patches. The middle layer consists of metal walls, and the bottom layer is a metal ground. The purpose of adding four parasitic patches, four metal walls and rings of phase delay for the dipole arm is to expand the impedance bandwidth (IBW) and axial ratio bandwidth (ARBW). In addition, by improving the feed structure at the dipole arm, the ARBW can be further widened. The overall design size of the final antenna is 0.8λ0*0.8λ0*0.29λ0 (λ0 is the wavelength at 3.7 GHz). The simulation results depict that the IBW of is 99.3% (1.83 GHz~5.44 GHz) and 3dB ARBW of is 91.4% (2.02 GHz~5.42 GHz). The gain range of the proposed antenna is 3.3dBic to 6dBic in the CP working frequency band.