Dual-polarisation reflectarray made of cells with two orthogonal sets of parallel dipoles for bandwidth and cross-polarisation improvement

A reflectarray antenna has been proposed to provide broadband operation, low cross-polarisation and independent beamforming in dual linear polarisation. The reflectarray element consists of two orthogonal sets of three coplanar parallel dipoles, where each set of parallel dipoles is used for controlling the phase-shift of each polarisation. A focused beam 40 cm reflectarray has been designed, manufactured and tested. According to the experimental results, the antenna shows a 27% bandwidth for a gain of 32.9 dBi with a variation of 1 dB. The antenna efficiency is better than 60% and the maximum crosspolar radiation levels are at least 30 dB below the main beam co-polar levels for both linear polarisations. In addition, it has been demonstrated that the antenna performance is maintained when it is designed to provide two separate beams in each linear polarisation.