Bow-Tie-Shaped Radiating Element for Single and Dual Circular Polarization

A fully metallic radiating element is presented in this article for single and dual circular polarization applications. The shape of the radiating element corresponds to a bow-tie-shaped field rotator designed to generate two orthogonal modes in quadrature as a basis for circular polarization. The bow-tie-shaped basic element is able to provide low axial ratio with a compact, easy-to-manufacture profile. In addition, it allows diverse ways of operation: feeding through a rectangular waveguide provides single circular polarization, while square waveguide is used for dual circular polarization. The radiating element has been designed at the Ku band and validated by the competitive experimental results. In the case of single circular polarization, over 21% bandwidth has been obtained under 15 dB return loss and 3 dB axial ratio criteria, with a radiating element height of 0.75λ0(free-space wavelength) at 18 GHz. The dual circularly polarized version achieves 18.3% bandwidth when 15 dB return loss and 3 dB axial ratio are established. In this case, the required antenna height is slightly higher than λ0at 18 GHz.