3D-printed cylindrical Luneburg lens antenna for millimeter-wave applications

A 3D-printed cylindrical Luneburg lens antenna working at 26 GHz is proposed in this article. The antenna consists of a feeding waveguide, a 3D-printed cylinder, and a pair of printed metal grids which are stuck on the side faces of the cylinder. 3D-printed structure ensures the convenience for processing and structural integrity of the Luneburg lens. Hole drilling technology is utilized for the design of the cylindrical lens. In the E-plane, conversion of spherical waves into planar waves is achieved based on the gradient refractive index which is realized by the gradient equivalent relative dielectric constant. The main part of the lens contains a hole drilling region to realize the desired equivalent permittivity from 1.23 to 2, while another gradual-thickness region realize the permittivity ranges from 1.23 to 1. H-probe method is utilized for the optimization of the gradual-thickness region in this article. And for the H-plane, with the grids, H-field distribution is optimized compared with the Luneburg lens antenna without the loading grids. Thus, the side lobe level (SLL) in H-plane could be reduced. Meanwhile, a narrower half power beamwidth (HPBW) in H-plane will be obtained due to the metal grids. Experiment results illustrate the feasibility and validity of the proposed 3D-printed cylindrical Luneburg lens antenna.