Circularly polarizing antenna feed

A circularly polarizing antenna feed comprises a feed waveguide having a short circuit reflecting plate at one end and a radiating horn at the other, a wave exciter for launching linearly polarized plane waves axially along the feed waveguide in opposite directions, and a grid of parallel reflector strips disposed in a plane which is perpendicular to the waveguide axis and which is located between the wave exciter and the reflecting termination at a distance of approximately lambda g/8 from the exciter and approximately lambda g/4 from the termination. The reflecting strips of the grid are inclined at an angle of 45 DEG to the direction of polarization of the waves propagated by the exciter, the grid and the reflecting termination together forming a twist reflector which effectively reflects and rotates through 90 DEG the waves incident upon the grid. These reflected waves together with the forwardly propagated waves from the exciter represent circularly polarized waves. As an alternative to the reflector grid the feed may comprise a metal septum plate which has an axial length of lambda g/4 and which is disposed in the waveguide in an axial plane inclined at 45 DEG to the polarization direction of waves propagated by the exciter and so that its front edge is located lambda g/8 behind the exciter.