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Circularly polarized helix and spiral antennas

  • US 3,906,509 A
  • Filed: 03/11/1974
  • Issued: 09/16/1975
  • Est. Priority Date: 03/11/1974
  • Status: Expired due to Term
First Claim
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1. An elliptically polarized helical antenna with low axial ratio comprising a support having a conductive outer surface, at least two conductors spaced from said surface and helically wound about said surface in the same direction, said conductors wound with a pitch angle greater than 25*, means for supporting the helical conductors spaced from said surface, and means for feeding the adjacent end of each of said two or more conductors with voltages of substantially equal magnitude and having predetermined phase relationship whereby to excite said antenna in a selected mode, said helically wound conductors being unequally spaced around the support and the feed voltages are given by Vn 3j n M where n 1, 2, ...N N the total number of helically wound conductors M the mode number, an integer, for mode M the phase of the radiated electric field varies with the azimuth angle, phi , as M phi for a constant elevation angle theta , and the magnitude of the electric field is essentially independent of the azimuth angle phi , phi n the angular placement of the nth helically wound conductor about the support, all starting and fed at the same transverse plane.

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