Ground-plane-backed hemispherical Luneberg-lens reflector

A spherical Luneberg-lens reflector provides excellent passive wideband and wide-angular radar-signature augmentation, and has been widely used. Much of its signature-enhancement performance over half of its angular coverage can potentially be achieved by using a corresponding low-profile, hemispherical Luneberg-lens reflector, mounted on a reflective ground plane. This paper presents a quantitative study of a practical design of an off-the-shelf hemispherical Luneberg-lens reflector to gain insight and to fully explore its performance limits. Extensive wideband and wide-angle measurements were carried out for this lens configuration, and a comprehensive numerical analysis was also conducted, using the finite-element method combined with a boundary integral equation to complement the test data. The effect, in practice, of a finite-sized ground plane, and the resulting vertically polarized traveling-wave interference to the direct lens reflector's return, were demonstrated. Key design issues are discussed, and potential solutions are suggested.