Geodesic lens antennas for low-angle radiation

Previous unit-index geodesic lens antenna designs have not been able to produce a lens with good radiation characteristics in or near the plane of the lens rim. This paper extends previous work to permit the design of a geodesic lens for angles within approximately
20\deg
of the plane of the lens rim. This is accomplished by requiring that less than the full semicircular aperture be exactly focused, and also by dividing the outer annulus into two or more constant-slope sections. The capability of these lenses for beam elevation positioning is also discussed.