Appeal No. 1998-0180
Application No. 08/471,309
BACKGROUND
The invention is directed to a tracking antenna having coaxial waveguides. Claim 1 is
reproduced below.
1. In a tracking antenna of the type having a feed for receiving electromagnetic energy from
free space, the feed having a sum port and a difference port, the feed comprising,
a first coaxial waveguide having an input end and an output end, said waveguide being bounded
longitudinally by an inner conducting surface and by an outer conducting surface, and
a second coaxial waveguide having an input end and an output end, said second waveguide
being bounded longitudinally by an inner conducting surface and by an outer conducting surface,
the first coaxial waveguide being located inside of and coaxially with the second coaxial
waveguide,
the first coaxial waveguide having an opening at its input end, the opening allowing
electromagnetic energy to pass from free space into and propagate within the first coaxial waveguide,
said electromagnetic energy propagating within the first coaxial waveguide in the TE11 mode, the TE11
mode having a dispersion,
the second coaxial waveguide having an opening at its input end, the opening allowing
electromagnetic energy to pass from free space into and propagate within the second coaxial
waveguide, said electromagnetic energy propagating within the second coaxial waveguide in the TE21
mode; the TE21 mode having a dispersion,
the dimensions of the first coaxial waveguide and the dimensions of the second coaxial
waveguide being selected such that the dispersion of the TE11 mode in the first coaxial waveguide is
approximately the same as the dispersion of the TE21 mode in the second coaxial waveguide,
the first coaxial waveguide having a first coupling device connected to its output end, the first
coupling device coupling energy between the sum port and electromagnetic energy propagating within
the first coaxial waveguide,
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