Small dual frequency band, dual-mode feedhorn

Claim 1

A dual frequency band, dual-mode feedhorn comprising: a first waveguide section (20) comprising a longitudinal passage with a first and second port at a first and second end thereof, respectively, and capable of supporting a dominant TE 11 mode of a first and a second signal in a first and a second frequency band, respectively, propagating therein; a second waveguide section (22) comprising a longitudinal passage, which is larger in cross-section than the longitudinal passage of the first waveguide section, with a first and a second port at a first and a second end thereof, respectively, and capable of supporting the TE 11 mode of said first and second frequency bands and only the TM 11 mode of a higher one of the two frequency bands; a first discontinuity (21) connecting the second port of the first waveguide section with the first port of the second waveguide section and capable of converting a portion of the TE 11 mode in both frequency bands into TM 11 mode energy; a third waveguide section (24) comprising a longitudinal passage, which is larger in cross-section than the longitudinal passage of the second waveguide section, with a first and a second port at a first and a second end thereof, respectively, and capable of supporting the TE 11 and TM 11 mode in said first and second frequency bands, said second and third waveguide sections comprising a longitudinal length such that the vector sum of the associated TE 11 and TM 11 mode components in each of the frequency bands are all substantially in phase at the second port of the third waveguide section; and a second discontinuity (23) connecting the second port of the second waveguide section with the first port of the third waveguide section and capable of converting a portion of the TM 11 mode in both frequency bands into TM 11 mode energy.