Plastic-Filled Dual-Polarized Lens Antenna for Beam-Switching in the Ka-Band

This letter presents a circular lens antenna for wideangle beam steering and for dual-polarized operation at millimeterwave (mm-wave) frequencies (27-30 GHz). The lens consists of a dielectric disc and two parallel plates, whose vertical spacing is varied linearly to achieve a suitable effective refraction index profile for the polarization parallel to the plates. The desired refraction profile is that of the Luneburg lens. The variation in plate spacing has negligible effect on the polarization perpendicular to the plates, and therefore, the dielectric material is selected such that the circular shape of the lens approximates the dimensions of the extended hemispherical lens. This way, the lens provides focusing or collimation for both linear polarizations. The lens is fed with square waveguides supporting both polarizations. Several feeding waveguides allow beam switching over a wide angular range. The designed lens antenna was fabricated, and the simulation and measurement results agree well and show that the proposed antenna concept is a valid solution for the upcoming 5G technologies, for instance as the access-point antenna. The antenna provides a ±50° beam-scanning range in both polarizations, and the realized gain is mostly between 9 and 12 dBi for the main beam. The measured reflection coefficient is mainly below -10 dB for both polarizations across the whole frequency band.