Generic Luneburg Lens With Focus-Radius Ratio Fs ≥ 1

As is known that the Luneberg lens misaligns the focus if the feed antenna is not on the spherical surface, as a result, the radiation performances such as the gain and the sidelobe suppression degrade. Aiming to tackle the above problem, this report presents a generalized model in which the focal length can be customized to allow for focus-radius ratio Fs > 1, i. e., the feed antenna may be set outwards and far away from the spherical surface of the Luneburg lens while perfect radiation pattern e. g., the high gain value and wonderful sidelobe suppression etc., remains. Furthermore, this report gives a set of analytical closed-form solutions of optimized shell thickness as well as the corresponding dielectric constant for given Fs and number of shells to allow to manufacture the proposed generic Luneburg lens with the widely applied multiple-shell technique. An eight-beam Luneburg lens antenna with Fs = 1.5, where the feed-centroid distance is 1.5 times the radius, is designed, manufactured, and measured by the Satimo-128 spherical near-field system, which exhibits excellent gain, side-lobe suppression and other radiation performances, and thus validates the proposed approach for the generic Luneburg lens.