The impossibility of certain desirable luneberg lens modifications

Abstract
THE DIFFICULTY of rapid scanning over the outer surface of a Luneberg lens has led Gutman1 to devise a lens in which the feed moves on a smaller radius. In Gutman's lens the feed horn points toward the center of the lens and the center section, which rotates during the scan, also serves as a focusing region. In some applications it would be desirable to point the feed horn outward and reserve this center section for rf components. The rotational torque required could also be reduced considerably thereby. We assume throughout that the lens must be radially symmetric to allow 360° of scan.