An antenna array assembly comprises a ground plate, an array of radiator elements disposed in a spaced relationship with a first face of the ground plate between first and second substantially parallel conductive walls projecting from the first face of the ground plate, and a first and second conductive plate. Each of the first and second conductive plates is electrically isolated from the ground plate, and each is disposed in an upstanding relationship to the first face of the ground plate in a substantially parallel relationship with the first and second conductive walls. This provides reduced radiation in at least one direction in the hemisphere on the opposite side of the ground plate to the first face.