Lens Antenna With Planar Focal Surface for Wide-Angle Beam-Steering Application

A new lens antenna for wide-angle beam-steering application is presented. The 2-D lens permittivity profile according to Luneburg is modified using transformation optics to obtain a planar focal surface, allowing for a simple cost-effective planar feed technology. A slice of the lens is confined between two metallic surfaces forming a parallel-plate transmission line, enabling beam-steering in the plane containing the slice. Stacking up such slices result in a more focused beam and beam-steering capabilities in the perpendicular plane. As a result, full 2-D beam-steering becomes possible, with a very wide steering range of ±60° in one plane and a smaller steering range of ±15° in the orthogonal plane. The inhomogeneous dielectric slice is made of four dielectric materials with different permittivity, with a pattern of drilled holes of different diameters realizing a smooth gradient of the effective permittivity. The measured performance of the antenna prototype, operating at about 10 GHz includes 17.2 dB maximum directivity, a scan loss better than 0.8 dB, a sidelobe level better than 11 dB, and an aperture efficiency of 74%, outperforming any other reported beam steering antenna with planar focal surface.