Best Feed Positions and Radiation Patterns of Typical Multibeam Dielectric Lens Antenna

Abstract

Multibeam base station antennas are introduced for 5G and 6G mobile communication systems. Considering higher frequency bands such as millimeter waves for 5G and terahertz for 6G, dielectric lens antennas become promising candidates due to their simple antenna configuration and excellent multibeam radiation characteristics. Therefore, it is important to identify the best multibeam antenna from the existing typical lens antennas. In this article, a shaped lens and some conventional lenses are considered. For the conventional types, the hyperbolic-planar, plano-convex, and spherical-convex are selected. As for the shaped lens, Abbe's sine condition lens is selected. This research begins by finding the best feed position of four types of lenses. A MATLAB program is developed to find the smallest distance point for all focal region rays. Based on this point, the feed position is selected and multibeam radiation patterns of four lenses are obtained. It is shown that the spherical-convex lens can achieve the highest gain and the smallest beam shape degradation. High gain characteristics are obtained until a 35° beam shift. As for sidelobe characteristics, Abbe's sine condition lens has the lowest sidelobe level. These properties are then clarified using amplitude and phase distribution on the aperture plane. Furthermore, focal region ray concentration changes by F/D and refractive index are discussed for practical applications.