The Luneburg Lens is a passive radar augmentation device used to increase the radar reflectivity of a target without the use of additional energy.
The lens reflector is a sphere in shape, usually composed of concentric dielectric shells. By the proper selection of dielectric constants for each shell, radar energy incident on one of the faces of the lens is focused at a point on the rear surface of the lens. The rear conductive surface reflects radar energy back to the source.
The physical characteristic of a Luneburg lens varies according to its application and the frequency at which it is required to operate. To meet a variety of weapon system requirements, QinetiQ Target Systems integrates a variety of lens types into its targets. Generally these are of 7.5 inches in diameter, but alternative sizes from 4 inches to 8.7 inches in diameter are available.