First-order aberrations on generalized classical axially-symmetric dual-reflector antennas

This work presents a first-order treatment of aberrations caused by small feed displacement in classical axially-symmetric dual-reflector antennas. A general and closed-form analysis (based on geometrical optics) of the aberrated aperture field is derived in terms of the reflector geometry and feed illumination. The consequence to the aperture efficiency and main-beam tilt are illustrated for an axially-displaced-ellipse configuration.