Fully Metallic Anisotropic Lens Crossover-in-Antenna Based on Parallel Plate Waveguide Loaded with Uniform Posts

This article presents a Ka-band fully metallic crossover-in-antenna based on an anisotropic lens. The crossover-in-antenna is a multifunction device simultaneously acting as a waveguide crossover and a multibeam antenna. The anisotropic lens performs like a Maxwell fish-eye (MFE) lens and a Luneburg lens in different incident directions, supporting the transmission and radiation, respectively. The lens consists of a parallel plate waveguide (PPW) with gradient spacing loaded with periodic uniform cuboid posts, which can be treated as an array of anisotropic subwavelength unit cells with gradient equivalent refractive indices. The WR28 waveguides are employed as the input-output ports. A flare is added to improve the radiation and impedance matching of antenna channels. According to the experimental results, a waveguide crossover is well realized with the reflection coefficients lower than -15 dB and insertion losses mostly lower than 1.4 dB from 28.7 to 38.2 GHz. Meanwhile, a multibeam antenna with four independent beams is obtained in the whole Ka-band, showing the gains higher than 12.5 dBi and the radiation efficiencies higher than 87.8%. The results indicate that the proposed crossover-in-antenna has application potential in the high-density multifunction integration of millimeter-wave (mmW) systems.