A Low-Profile High-Gain Multi-Beam Antenna Based on Cylindrical Metasurface Luneburg Lens

Abstract

A multi-beam antenna is present in this paper based on a cylindrical metasurface Luneburg lens. The antenna is composed of a flat Luneburg lens beamforming network (BFN) and a substrate integrated waveguide (SIW) leaky-wave antenna (LWA) array. The LWA array is placed on the top of the BFN, several coupled slots are used to transform the field from the bottom BFN to the top radiator. The multi-layer design greatly miniature the size of the antenna. The flat cylindrical Luneburg lens is realized by an air full parallel plate waveguide (PPW) with non-uniform circular slots on the bottom metallic plate, and the diameters of the circular slot can adjust the effective refractive index distribution in the PPW. The sources at different positions of the focal plane can generate different phase gradients to the LWA array by the Luneburg lens. Hence, the proposed antenna can realize a passive beam scanning capability by the ports switching. In our simulation, the antenna can achieve seven beams with a ±28° beam scanning range within the operating bandwidth of 5.73-5.9GHz. The gain, side lobe level (SLL), and crossover level of the 7 beams are around 25dB, -11dB and -4dB in the simulated results, respectively. The advantages including low profile, low cost and passive beam scanning capability make it a very promising solution for communication and radar applications.