We have developed a new method for generating arbitrary radiation patterns from conformal antennas on complex metallic objects. The object is coated with a pattern of conductive patches that are printed on a grounded dielectric layer. The patches are small compared to the wavelength of interest, and the coating can be considered as an artificial impedance surface. By varying the shape of the patches, we can create an arbitrary surface impedance profile, which governs the electromagnetic scattering properties of the surface, and controls the radiation pattern of antennas on the surface. Borrowing concepts from holography, the surface impedance is designed as the interference pattern between the expected currents generated by an antenna, and the fields corresponding to a desired radiation pattern. This holographic artificial impedance surface enables conformal antennas with novel radiation properties, including significant gain in directions that would normally be shadowed by the object.
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