Scanning beam antenna arrangement
First Claim
1. A feed arrangement for use with an antenna systemcharacterized in thatthe feed arrangement comprises a linear phased array of feed elements (14) capable of effecting an essentially planar wavefront (25) which is scannable along one angular coordinate, the array being disposed within a rectangular waveguide section (27) with the wide sides (261, 262) thereof oriented parallel to both the linear array and said one angular coordinate, the rectangular waveguide section comprising an offset curved focusing reflecting surface (28) disposed therein for bidirectionally converting an essentially planar wavefront propagating between the linear array and the reflecting surface into a converging wavefront which is focused to a point source at a focal plane (Σ
- f) of the feed arrangement and when the array is scanned along said one angular coordinate the resulting point sources of a scanning wavefront move along a straight line of the focal plane, and the principle ray of each converging wavefront is always directed at a predetermined remote point beyond the focal plane regardless of the direction of scan along said one angular coordinate.
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Abstract
The present invention relates to an antenna arrangement capable of generating one or more linearly scanning spot beams which are scanned over separate strip portions of the entire field of view of the antenna. The antenna arrangement comprises an optical system comprising an aperture and a focal plane, and a novel feed arrangement. The feed arrangement comprises a separate linear phased array disposed within a separate rectangular waveguide section for each linear scanning beam desired. An offset curved reflector, disposed in each waveguide section, converts a linearly scanning planar wavefront generated by an array into a converging beam forming a linearly moving point source on the antenna'"'"'s focal plane with the principle ray of each instantaneous wavefront being directed at the center of an image of the aperture of the optical system as seen by the feed arrangement.
26 Citations
8 Claims
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1. A feed arrangement for use with an antenna system
characterized in that the feed arrangement comprises a linear phased array of feed elements (14) capable of effecting an essentially planar wavefront (25) which is scannable along one angular coordinate, the array being disposed within a rectangular waveguide section (27) with the wide sides (261, 262) thereof oriented parallel to both the linear array and said one angular coordinate, the rectangular waveguide section comprising an offset curved focusing reflecting surface (28) disposed therein for bidirectionally converting an essentially planar wavefront propagating between the linear array and the reflecting surface into a converging wavefront which is focused to a point source at a focal plane (Σ - f) of the feed arrangement and when the array is scanned along said one angular coordinate the resulting point sources of a scanning wavefront move along a straight line of the focal plane, and the principle ray of each converging wavefront is always directed at a predetermined remote point beyond the focal plane regardless of the direction of scan along said one angular coordinate.
- View Dependent Claims (2, 3)
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4. A scanning beam antenna arrangement comprising:
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an optical system including an aperture (D0) and a focal plane (Σ
f), the optical system being capable of bidirectionally converting an essentially planar wavefront at the aperture (D0) into a converging wavefront which is focused at a focal plane (Σ
f) of the optical system; anda feed arrangement disposed on the focal plane of the optical system in a manner capable of intercepting the converging wavefront characterized in that the feed arrangement comprises a linear phased array of feed elements (14) capable of generating an essentially planar wavefront which is scannable along one angular coordinate, the array being disposed within a rectangular waveguide section (27) with the wide sides (261 and 262) thereof oriented parallel to both the linear array and said one angular coordinate, the rectangular waveguide section comprising an offset curved focusing reflecting surface (28) disposed therein and capable of bidirectionally converting an essentially planar wavefront propagating between the linear array and the reflecting surface into a converging wavefront propagating between the reflecting surface and the optical system in a manner that each converging wavefront of the feed arrangement is focused at the focal plane (Σ
f) and is scanned linearly therealong, the principle ray in each converging wavefront being directed at essentially the central point of an image of the aperture (D0) of the optical system as seen by the feed arrangement regardless of the direction of scan along said one angular coordinate, whereby a linear scanning spot beam is capable of being generated by the antenna arrangement which covers only a strip portion of an entire field of view of the antenna arrangement. - View Dependent Claims (5, 6, 7, 8)
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Specification