Fully Metallic Millimeter-Wave and Sub-6 GHz Aperture-Shared Multibeam Luneburg Lens Integrated Stacked Horn Antenna

This article demonstrates a fully metallic aperture-shared multi-beam Luneburg lens integrated stacked horn antenna. Multiple high-gain beams at 28 and 38 GHz bands are achieved based on the Luneburg lens that can collimate the spherical waves into plane waves. The bed of nails with different heights inside the parallel plate waveguide (PPW) achieves a gradient refractive index (GRIN) for mm-wave Luneburg lenses. The two Luneburg lenses are integrated into a sub-6 GHz stacked horn antenna with a shared aperture. To solve the blockage issue, the Luneburg lens feeds are implemented using the gap-waveguide technique, which confines the mm-wave band energy to feed the lens and permits the sub-6 GHz wave to propagate. The antenna achieves multi-beam radiation with low gain fluctuation at both 28 and 38 GHz, with beam switching angles of 0°, ±22.5°, and ±45°, and boresight radiation in the sub-6 GHz band. An antenna prototype is designed, fabricated, and measured.