Horn antenna with rotating waveguide and polarization lens means

An antenna feed system comprising a rectangular horn having a rectangular aperture, a rectangular waveguide connected to said horn, said horn and waveguide being formed from two parts joined together so that the junction therebetween is in the longitudinal symmetry plane parallel to the electric field of the TE.sub.01 waveguide mode, a polarisation converter including a screen comprising a plurality of dielectric layers each having a conductor pattern provided thereon such that said patterns form a predominantly capacitive load for one component of the electric field of an electromagnetic wave incident on said screen, and a predominantly inductive load for a second component of said field which is perpendicular to said one component, first means for supporting said screen in front of said aperture for rotation about the longitudinal axis of said waveguide and second means for supporting said horn and waveguide connected thereto for rotation about said longitudinal axis relative to said screen.