Frequency performance of 4-layer discretized Luneburg antennas

A series of 8λ
₀
to 14λ
₀
radius 4-layer stepped approximation Luneburg lenses were designed for the same scalar feed positioned at 1.1 lens radii. The relative permittivities and normalized thicknesses of the matching layers of each lens were close but not equal. The lenses were simulated in commercially available full wave simulators. The aperture efficiencies decreased as the lens radii was increased, showing that minor variations in layer thickness and relative permittivity were unable to compensate for decreased excitation aperture illumination. Achieving high aperture efficiencies requires optimization of both lens and feed, the best here been 80% across 15% bandwidth for the 8λ
₀
lens. The peak cross-polarized radiation within the main lobe was found to be in the 45° plane and to be an artifact of the scalar feed, and not the lens designs.