Enhancing cross‐polarisation discrimination or axial ratio beamwidth of diagonally dual or circularly polarised base station antennas by using vertical parasitic elements

The cross‐polarisation discrimination (XPD) of a ± 45° dual‐polarised base station antenna is enhanced by adding vertical parasitic elements. First, it is established that high XPD can be achieved by employing four vertical parasitic elements between a simple ± 45° dual‐polarised radiator and ground. Second, based on the proposed method, a simple ± 45° dual‐polarised antenna for a long‐term evolution 1.71–2.17GHz base station is designed, fabricated and measured. Compared with the antenna without vertical elements, XPDs are improved by about 7dB in the horizontal plane due to the addition of the vertical parasitic elements. Third, with a wideband quadrature hybrid, the proposed antenna is shown to radiate circularly polarised waves. In particular, the 3 dB axial ratio beamwidth of the proposed antenna is increased from 84 ° to 195 ° with the addition of the four vertical parasitic elements.