Impact of Element Polarization on the Circular Polarization Purity of Phased Arrays with Sequential Feeding Network

The effect of the antenna element polarization on the polarization purity of phased arrays fed using sequential rotation networks is investigated. As a case study, two 4×4 antenna arrays are designed with linear polarized (LP) and circular polarized (CP) elements and integrated with sequential feeding networks. By changing the excitation phase via the feeding network, the radiation patterns are steered to different angles up to 40°. The calculated axial ratio bandwidth demonstrates that the antenna array with CP elements maintains high circular polarization purity for steering angles of more than 20° compared to the antenna array with LP elements, where the onset of polarization purity degradation is observed from small scanning angles. Consequently, it is recommended to use CP elements in sequentially rotated antenna arrays to achieve a purer circular polarization for wide steering angles.