An array antenna including two interleaved array antennas, capable of being operated independently at a first frequency, or together, at a second frequency. Each of the two array antennas is composed of alternating elements of an antenna array, and the two arrays are interleaved. Each of the interleaved arrays may be operated independently, e.g., in the X band, or the arrays may be driven together, as a single array with more densely spaced elements, e.g., in the Ku band.