Broadband low profile substrate-integrated antenna based on gradient index lens

A broadband metamaterial-based low profile antenna is presented in the 8-12 GHz frequency band. The antenna is composed of a parallel-plate TEM waveguide embedding a planar gradient index Luneburg lens and a slot Vivaldi antenna that illuminates the latter lens. The focusing condition of the lens, requiring a gradient refractive index is achieved through the use of complementary non-resonant metamaterial structures. Numerical simulations are performed to determine the suitable unit cells geometry with respect to the wave launcher. A prototype fabricated using standard printed circuit board techniques has been measured in an anechoic chamber. A good qualitative agreement is observed between simulations and experiments. The proposed planar antenna presents good focusing properties.