A Multibeam Flat GRIN Lens Antenna With Full 2-D Beam Coverage

This article presents the development of a wide-angle multibeam flat gradient-index (GRIN) lens antenna that supports full 2-D beam coverage using a fully planar topology. An optimal flat focal plane is first determined to achieve high-performance multiple beam radiation across different elevation angles. Subsequently, a compact sublens-integrated feeding mechanism is introduced, supporting effective tilting of the feed beam in both azimuthal and elevational dimensions toward the lens center. This approach mitigates spillover losses of multiple feeds while enabling their seamless placement on the flat focal plane. A proof-of-concept prototype is fabricated and tested, incorporating 21 feed structures to achieve 21 beams distributed over a 2-D coverage. Measurement results demonstrate that all feeds can operate simultaneously with high isolations, supporting multiple independent beams with angular ranges of 360° in the azimuthal plane and about ±50° in the elevation plane. The fabricated lens antenna achieves a 3-dB gain bandwidth of 11.2% from 12.7 to 14.2 GHz, with a peak realized gain of 19.0 dBi at 13.0 GHz, corresponding to an aperture efficiency of 38%.