Dual Offset Reflector Antenna Systems with Rotationally Symmetric Aperture Distributions.

A detailed derivation is given of the basic design equation for a dual offset reflector antenna consisting of a paraboloid main reflector and a confocalhyperboloid or ellipsoid subreflector. The basic design equation is a relation between the subreflector eccentricity the relative orientations of the axes of the main reflector, subreflector, and feed and the paraboloid focal length. If satisfied, the basic design equation guarantees that that to within the geometric optics approximation a circularly symmetric and linearly polarized feed pattern will give rise to a circularly symmetric and linearly polarized main aperture distribution and far field pattern. The relation between the amplitude distribution of the feed pattern and main aperture is also derived.