A Novel Collapsible Flat-Layered Metamaterial Gradient-Refractive-Index Lens Antenna

With the advent of small-scale satellite technologies, there has been significant interest in developing low-profile antennas. This article presents a novel collapsible flat-layered lens based on gradient-refractive-index (GRIN) metamaterials. The 3-D lens consists of multilayer double-sided microstrip square-rings units of variable sizes distributed on planar dielectric substrates to satisfy the required refractive index distribution. Adjacent layers can be stored compressed in a stacked configuration with minimal height, then deployed to an operational arrangement to their full dimensions and capabilities. The key factor in this design is the judicious choice of the discretized metamaterial unit cell such that neighboring layers are separated by an air gap, which allows the lens to collapse. A proof-of-concept prototype operating at 13.4 GHz with a 11.2 cm diameter and a height of 0.4 and 2.1 cm in collapsed and operational arrangement, respectively, was manufactured within fabrication tolerances. A resonant patch array feed was used and the lens antenna was measured in the UCLA Plane Bi-Polar Near-Field measurement range achieving a 23 dBi directivity and 22.2 dBi gain. The numerical and experimental results agree well and demonstrate that this new lens is advantageous in terms of low packaging height without compromising high-performance.