Small dual frequency band, dual-mode feedhorn

• US 4,442,437 A
• Filed: 01/25/1982
• Issued: 04/10/1984
• Est. Priority Date: 01/25/1982
• Status: Expired due to Term

• Current Assignee: Bell Telephone Laboratories, Inc. (Nokia Corporation)
• Original Assignee: Bell Telephone Laboratories, Inc. (Nokia Corporation)
• Inventors: Chu, Ta-Shing, England, Robert W.
• Primary Examiner(s): Lieberman, Eli
• Assistant Examiner(s): Wimer, Michael C.
• Application Number:
  US06/342,058
• Time in Patent Office: 806 Days
• Field of Search: 343/786, 343/776, 343/772, 343/778, 343/773
• US Class Current: 343/786
• CPC Class Codes: H01Q 13/025 Multimode horn antennas; Horns using higher mode of propagation H01Q13/0241 takes precedence; multiple beam H01Q25/04
• CPC Class Codes: H01Q 5/45 using two or more feeds in association with a common reflecting, diffracting or refracting device

Abstract

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.

Claims

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 TE₁₁ 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 TE₁₁ mode of said first and second frequency bands and only the TM₁₁ 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 TE₁₁ mode in both frequency bands into TM₁₁ 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 TE₁₁ and TM₁₁ 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 TE₁₁ and TM₁₁ 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 TM₁₁ mode in both frequency bands into TM₁₁ mode energy.

2. A dual frequency band, dual-mode feedhorn according to claim 1 wherein said first and second discontinuities comprise a first and a second tapered portion, respectively, at a respective first and second angle to an inner wall of the second and third waveguide sections, respectively.

3. A dual frequency band, dual-mode feedhorn according to claim 1 or 2 wherein said first and second discontinuities comprise a smooth rounded surface in the area where said first and second discontinuities connect to the second ports of said first and second waveguide sections, respectively, to avoid an unwanted excitation of TM₁₁ modes.

4. A dual frequency band, dual-mode feedhorn according to claim 1 wherein the combined longitudinal length of said second and third waveguide sections is such that a differential rotation for a phase vector for the TM₁₁ mode in the higher one of the two frequency bands which was excited by said first discontinuity will not exceed 2π

in reaching the second port of the third waveguide section.