Abstract: A flat antenna array includes a screen plate, a conductive aperture plate which overlies the screen plate, and a dielectric sheet which is located between the aperture plate and the screen plate. Apertures in the screen plate define the locations of waveguides. A network of conductors is carried on the dielectric sheet. The conductors include stimulating elements which are aligned with the apertures. Each stimulating element includes first and second probes which have axes which cross each other and constitute a probe pair. A plurality of reflective elements are located above the dielectric sheet at locations which correspond to the apertures. A first output circuit connects together the first probes, a second output circuit connects together the second probes.