Symmetry, XPD, and port isolation in an ACMPA array with dual linear polarization

Aperture coupled microstrip patch antennas (ACMPA) are very convenient array elements for designing high directivity planar antennas. Dual polarization ACMPA arrays for Direct Broadcasting Services (DBS) have the problems of low cross-polar discrimination (XPD) and port isolation. In this work, the relationships between feed symmetry and the values of XPD and Port Isolation are investigated. A particular feeding structure, which optimizes XPD and Port Isolation, is proposed. An 4x4 array that operates at the European DBS frequencies has been designed, built and measured to demonstrate the effectiveness of the proposed structure.