A simple way to achieve planar excitation of arc-shaped array feeds in two-dimensional beam-steerable spherical lens antenna

Abstract

In this article, a simple technique for achieving planar excitation positions of arc-shaped array feeds in a two-dimensional (2D) beam-steerable spherical lens antenna (SLA) is proposed. Specifically, a cuboid solder model is introduced to connect the feedlines of the feeds with the coaxial probe. An equivalent circuit model of the bowtie feed unit with solder is proposed to illustrate the impact of the introduced solder on the port matching. Additionally, the excitation position is altered by extending the microstrip feedline, which does not change the radiation structure of the feed nor affect its phase center. Subsequently, a homogeneous dielectric SLA with a 139-element bowtie-shaped dipole feed array is constructed to verify the planar excitation position scheme for the arc-shaped array feeds, which facilitates system integration. The theoretical calculation formulas for the beam pointing angles of numerous beams are also proposed. In the fabricated prototype, all feeds exhibit an overlapping bandwidth of 31–36.7 GHz for reflection coefficients, with the coupling less than -20 dB. The 139 switched beams cover a 2D continuous beam space of [$-$33°, 33°], with adjacent beam crossover levels around -4 dB. The measured peak gain is 28.7 dBi at 34.5 GHz, with an aperture efficiency of 57%.