Importance

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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. A slab (48) of dielectric material is placed in each of the coupling sections to match the phase velocity of waves in the coupling sections to waves in the circular waveguide at the second frequency band while mismatching the phase velocities at the first frequency band. The dispersion of the waveguides provides for interaction with electromagnetic waves in the second frequency band while inhibiting such interaction at the first frequency band.

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First Claim