Small dual frequency band, dual-mode feedhorn

摘要

The present invention relates to a dual frequency band, dual-mode feedhorn comprising three serially connected waveguide sections (20, 22, 24) and a separate discontinuity (21, 23) at each joint between waveguide sections. More particularly, the feedhorn comprises a first waveguide section (20) for supporting the TE11 mode in both frequency bands. A first discontinuity (21) symmetrically increases the first waveguide size for converting a portion of the TE11 mode in both frequency bands into the TM11 mode. The second waveguide section (22) connected to the first discontinuity comprises an aperture size for supporting the TE11 mode in both frequency bands but only the TM11 mode of the higher frequency band. A second discontinuity (23) symmetrically increases the size of the second waveguide for converting another portion of the TE11 mode in both frequency bands into the TM11 mode. A third waveguide section (24) coupled to the second discontinuity is capable of propagating both modes in both frequency bands with a length to cause the vector sums of each of the remaining TE11 and TM11 modes in each frequency band to be in phase at the exit port of the feedhorn.