Broadband 3-D Luneburg Lenses Based on Metamaterials of Radially Diverging Dielectric Rods

In this letter, we describe and study microwave Luneburg lenses using a broadband metamaterial composed of radially diverging dielectric rods. The gradual Luneburg's permittivity profile is achieved in this lens through arranging identical thin rods with a spatially variable cross section in various radial directions with a subwavelength separation. The performance of the considered metamaterial lenses was studied by full-wave numerical simulation and measurements in an anechoic chamber. The results reveal that, although anisotropy of the structure causes aperture phase errors, the structure composed of diverging dielectric rods may still operate as a cylindrical or spherical Luneburg lens. Advantageously, the considered design is attractive for mass production of large-scaled beam-steering antennas because the lens is composed of identical shaped dielectric parts.