Abstract: A dual frequency array antenna comprises an upper layer including an array of antennas operating at a first frequency, a first ground layer disposed below the upper layer at a predetermined distance and a dielectric material disposed between the first ground layer and the upper layer. An array of slot radiator apertures are provided in the first ground layer. The apertures are spaced from the array of antennas and radiate at a second frequency. An array of feed lines is disposed at a predetermined distance below the first ground layer with one of the feed lines below each one of the apertures. A second ground plane layer is disposed at a predetermined distance below the array of feed lines. The two frequencies are, for example, from two distinct microwave bands.