Compound GRIN Fanbeam Lens Antenna With Wideband Wide-Angle Beam-Scanning
Nicolas Garcia, Jonathan Chisum
Abstract
This work presents a parallel-plate waveguide (PPWG) fanbeam antenna achieving a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pm 48^\circ $ </tex-math></inline-formula> field of view with an average maximum scan loss of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.7\,\textrm {dB}$ </tex-math></inline-formula> over 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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.58~$ </tex-math></inline-formula> dB at 48° and a scan loss exponent of 1.5 are achieved at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$40~$ </tex-math></inline-formula> GHz.