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Multiple beam satellite antenna with preferred polarization distribution

  • US 4,232,321 A
  • Filed: 11/24/1978
  • Issued: 11/04/1980
  • Est. Priority Date: 11/24/1978
  • Status: Expired due to Term
First Claim
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1. In a satellite communications system, a method of transmitting electromagnetic energy from a satellite to a remote receiving area on the surface of a celestial body which results in a reduced amount of cross-polarization coupling along the transmission path, the satellite being in orbit directly above a subsatellite point (51) on the celestial body and comprises an antenna arrangement comprising (a) at least a main reflector aperture, a feed and a focal surface disposed transversely about the feed axis, the focal surface being comprised of a plurality of focal points, each of which corresponds to a respective point in the remote receiving area and a projection of the subsatellite point (50) on the focal surface and (b) plural feed elements disposed on the focal surface, the method comprising the step of:

  • (a) energizing one or more feed elements (e.g., 113,

         114) for transmitting at least one beam of electromagnetic energy comprising any combination of a first and a second direction of essentially linear polarization which are orthogonal to one another toward the portions of the receiving area on the celestial body associated with the particular points on the focal surface where the energized feed elements are disposed,CHARACTERIZED IN THATthe method comprises the further step of;

    (b) in performing step (a), energizing the one or more feed elements for transmitting the at least one beam of electromagnetic energy so that when the first direction of polarization is used by any particular one of the energized feed elements, the first direction is aligned parallel to a line on the focal surface connecting the corresponding subsatellite point and the point where the particular feed element is disposed (60-66), and when the second direction of polarization is used by any particular one of the feed elements, the second direction is aligned orthogonal to the line on the focal surface connecting the corresponding subsatellite point and the point on the focal surface where the particular feed element is disposed (70-73).

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