A Truncated 2-D Luneburg Lens Antenna with Planar Feeding Surface Using PCB Technology for Stable Wide-Angle Beam-Steering Applications

A new approach for implementing a truncated Luneburg lens (LL) antenna (LLA) with a planar feeding surface is proposed, aimed at achieving stable wide-angle beam steering in millimeter-wave band. This technique entails the attachment of just two thin, high-permittivity dielectric slabs to the sides of the truncated LL, maintaining the original permittivity distribution of the lens, which ranges from 1 to 2. These high-permittivity dielectric slabs cause an upward shift of the focal points, leading to a focal plane near the truncated surface, with an increased curvature radius. As a result, the phase centers of the feed elements remain closely aligned with the lens's focal points, which is crucial for sustaining high gain and minimizing gain variation. To validate the concept, a nine-element patch antenna array was integrated with the lens to enable beam scanning, and the entire assembly was processed using low-loss printed circuit board technology. Measurement results demonstrated a peak realized gain of 14.09 dBi, with a gain fluctuation of only 0.6 dB across a broad beam-scanning range of ±67° at 30 GHz.