Abstract: A short-focus microwave reflector is located a short distance away from the feed horn and is positioned to reflect the beam of microwave radiation away from the feed axis and toward a large primary reflector antenna for transmission. A conical shield extends from the feed horn to the secondary reflector, joining them together as a unit and preventing sidelobe radiation. The beam of radiation emerges from the shield through an aperture in the sidewall thereof. The short focus of the secondary reflector causes the beam to be focussed approximately at the plane of the aperture, such that the beam diameter is small and the aperture can also be small, reducing stray radiation from the shield structure. Diffraction at the edges of the aperture is reduced by a radially surrounding choke structure which further suppresses sidelobe radiation.

Abstract: This specification discloses a polarization network for selectively converting between linear and circular polarization. The network includes a twistable waveguide having a generally rectangular cross section. Coupled to the twistable rectangular waveguide is a transducer waveguide which acts as an interface between the rectangular waveguide and circular waveguide. A polarizer having a generally circular cross section is coupled to the transducer waveguide and can convert transmitted electromagnetic waves between linear and circular polarization. A coupling means permits relative rotation between the transducer waveguide and the polarizer and selective securing at any of three rotational positions. A first position permits a linearly polarized signal to pass through the polarizer remaining linearly polarized. A second position converts between a linearly polarized signal and a right hand circularly polarized signal.