Compound GRIN Fanbeam Lens Antenna With Wideband Wide-Angle Beam-Scanning

This work presents a parallel-plate waveguide (PPWG) fanbeam antenna achieving a± 48^∘field of view with an average maximum scan loss of2.7\,dBover the Ka-band for a flat feed surface. This approach uses a novel compound gradient index (GRIN) lens system, wherein two GRIN lenses are cascaded axially: an “aperture” lens at the antenna output provides the bulk of the phase collimation, while a “focal” lens near the feed surface corrects the spillover losses and provides additional phase collimation. This arrangement represents a wide-scanning alternative that requires 76% of the axial depth and only 37.3% of the actual material compared to a Luneburg lens fanbeam antenna with similar aperture size. A maximum scan loss of$2.58~$dB at 48° and a scan loss exponent of 1.5 are achieved at$40~$GHz.