X-band high directivity lens antenna realized by gradient index metamaterials

This paper presents the theoretical modeling and prototype demonstration of broadband, low loss, and dual polarization capability of a gradient index metamaterial lens using multilayer microstrip square ring arrays. Microstrip closed square ring elements of variable size are distributed on the planar substrate to satisfy the radial gradient index function and axial impedance match layer configuration of the lens, which is designed to transform spherical wave-front into planar wave-front and minimize reflection loss. A prototype gradient index lens antenna composed of multilayer of CSR arrays and a PEC horn are modeled and simulated. The simulation results shows that the prototype lens antenna maintain low return loss and high directivity over X-band. These results demonstrate the feasibility of such a light weight slab metamaterial lens for broadband and high directivity antenna application, such as in radar and communication system.