Efficiency degradation caused by an axial feed defocusing in generalized classical axially-symmetric dual-reflector antennas

The present work investigates the efficiency decay due to small axial feed displacements in classical axially-symmetric dual-reflector antennas. Analytical expressions for the antenna aperture field were previously derived from Geometrical Optics (GO) principles. These expressions enable the study of the aperture aberration dependence on small feed displacements and the consequent decrease in antenna efficiency. Parametric studies are conducted, in a generalized way, for the complete set of classical axially-symmetric dual-reflector antennas. Some representative geometries are further analyzed by the Moment Method (MM) to determine the accuracy of the present formulation.