Optimum beam scanning in offset single and dual reflector antennas

Optimum beam scanning in offset single reflector (paraboloid) and dual reflector (Cassegrain and Gregorian) antennas is considered. Analytical, computationally efficient solutions and results are presented for the optimum feed position, the constant beam direction feed loci, and the optimum feed position locus. Examples are presented to verify that the analysis technique yields the optimum feed position, which exhibits better gain, pattern symmetry, and sidelobe levels when compared with other feed positions producing beams scanned to the same direction. The solutions described were obtained under the ray optics approximation and a 'receive mode' analysis. Although the developed method was applied to the antennas listed above, it can be easily extended to other n-reflector systems, shaped reflector antennas, lenses, and other similar systems.