A ground shield is connected to a princted circuit board or antenna card in an antenna unit cell to cover a balun to prevent or inhibit the ability of a differential signal flowing towards or through the balun from coupling with a similar differential signal flowing through an adjacent antenna card in the antenna unit cell. This ground shield may be one of a pair of ground shields on the antenna card. Two ground shield can be positioned on opposing sides of the balun to enhance isolation thereof by shielding the differential signals flowing towards and through the balun from coupling with adjacent differential signals to thereby increase bandwidth performance of the antenna unit cell. The ground shields may be generally or substantially or totally planar so as to be conformal with a substrate or dielectric layer of the antenna card or printed circuit board.