A Wideband PCB-Stacked Air-Filled Luneburg Lens Antenna for 5G Millimeter-Wave Applications

This letter presents a novel wideband printed circuit board (PCB)-stacked Luneburg lens antenna with a flared open edge for multibeam scanning application at 5G millimeter-wave band. The lens consists of two groups of parallel PCBs. Each group includes 12 layers of low-cost FR4 PCB, which are fixed by metal screws. Inside the lens there is no dielectric, resulting in an air-filled structure. With drilling holes of different radius in each PCB layer (except the top and bottom layers), the air spacing between the two groups of PCBs varies discretely which approximates the graded refractive index. Eleven antipodal linearly tapered antennas are placed on the focuses of the lens as feed elements, permitting the beam to cover a wide angular range. To enhance the gain of the lens, the radiation aperture is flared, like an H-plane horn. Measurements of the lens antenna with a diameter of 130 mm show good agreement with the theoretical predictions. The measured impedance bandwidth covers 26-37 GHz with isolations better than 18.8 dB. The measured peak gain is around 15.4 dBi at 29 GHz. By switching the 11 feed elements, the overall 2-D beam scanning coverage is up to ±72°. The results indicate that the proposed Luneburg lens antenna demonstrates a good application potential for 5G millimeter wave wireless communication.