Compact Metamaterial-Based Substrate-Integrated Luneburg Lens Antenna

A compact and small electric-size aperture directive broadband Luneburg lens antenna is presented. The substrate-integrated lens antenna is based on embedding a Vivaldi antenna source inside a parallel-plate waveguide to illuminate a Luneburg lens operating in X-band. The focusing condition of the lens, requiring a gradient refractive index, is achieved through the use of complementary nonresonant metamaterial structures. Numerical simulations are performed to determine the suitable unit cells geometry with respect to the wave launcher inserted into the parallel-plate waveguide. A prototype fabricated using standard printed circuit board techniques has been measured in an anechoic chamber. The electric field distribution inside the antenna system has also been explored using a two-dimensional near-field microwave scanning setup. A good qualitative agreement is observed between simulations and experiments. It has been shown from both far- and near-field measurements that the proposed planar antenna presents good focusing properties.