Abstract: Apparatus and method for providing an antenna feed (10) operative at different microwave frequency bands employ a circular waveguide (14) interconnecting an orthomode transducer (20) to a feed horn (16) thereby providing a feed (10) suitable for illuminating the reflector (54) of an antenna (12). The orthomode transducer provides for a coupling of waves in the first frequency band with both vertical and horizontally polarized waves. Included within the feed is a coupler assembly (26) of waves of the second frequency band operative via a sidewall of the circular waveguide. The coupler assembly includes plural identical coupling sections (28) each having a rectangular waveguide section contiguous and parallel to the circular waveguide with a row of apertures for coupling power into and out of the circular waveguide. Pairs of the coupling sections are disposed in orthogonal planes so as to introduce two linearly polarized waves which are perpendicular to each other.

Abstract: An antenna pointing detection system for use with circularly polarized electromagnetic radiation has a horn, a waveguide and at least one mode switching arm. The horn receives radiation in a primary mode from the radiation source. The waveguide receives radiation from the horn and supports only radiation in a primary mode, e.g. the TE.sub.11 mode and the next higher order TE mode, e.g. the TE.sub.21 mode at one or more rectangular mode switching arms extending from the circular waveguide for stimulating radiation of the-next order TE.sub.21 mode in the waveguide. The arm has a series of switchable pin diodes for changing the effective length of the mode switching arm to cause a phase alteration in the TE.sub.21 mode thereby causing a deflection of the effective pointing direction of the horn. The magnitude of the received signal is detected and compared with different deflections of the horn to operate conventional antenna pointing hardware.