Magnified beam waveguide feed with perfect pattern symmetry

Beam waveguide feeds are commonly employed as rotary joints in steerable reflector antenna systems requiring fixed transmitters and feed horns. With the traditional beam waveguide configuration shown, a perfect image of the feed (from a geometrical optics standpoint) can be generated at the beam waveguide focal point. In some situations, it is desirable to magnify the image of the feed. This allows a lower gain horn than what is actually required to feed the reflector antenna, to be used. In this paper, a new configuration of the traditional beam waveguide is presented. This new configuration allows magnification of the feed while maintaining the symmetry of the beam waveguide pattern, which results in zero cross polarization.