Patent ID: 6222492
Filing Date: 2001-04-24
Classification: H01Q

Abstract:
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, anda 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,the second coaxial waveguide having a second coupling device connected to its output end, the second coupling device coupling energy between the difference port and electromagnetic energy propagating within the second coaxial waveguide,whereby the first coaxial waveguide provides a sum electromagnetic radiation pattern with respect to the electromagnetic radiation received from free space and the second coaxial waveguide provides a difference electromagnetic radiation pattern with respect to the electromagnetic radiation received from free space.