Circularly polarized horn antenna

• US 20090033579A1
• Filed: 08/03/2007
• Published: 02/05/2009
• Est. Priority Date: 08/03/2007
• Status: Active Grant

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: Lam, Tommyhing-K H.
• Granted Patent: US 7,852,277 B2
• Time in Patent Office: Days
• US Class Current: 343/786
• CPC Class Codes: H01Q 13/02 Waveguide horns
• CPC Class Codes: H01Q 13/0266 provided with a flange or a choke
• CPC Class Codes: H01Q 15/244 converting a linear polarised wave into a circular polarised wave guided wave H01P1/17

Abstract

In some embodiments, a circularly polarized horn antenna may include a circular polarizer having a step shape. In some embodiments, a circularly polarized horn antenna may include a choke that is offset in position with respect to the antenna aperture. Such antennas may have a relatively constant beamwidth with respect to frequency, compact size, and/or low weight.

Claims

1. A horn antenna, comprising:

a waveguide; and

a circular polarizer coupled to the waveguide, the circular polarizer comprising a slab of dielectric material having a first portion of a first width and a second portion of a second width smaller than the first width such that the slab has a step shape, the second portion of the slab being positioned at an aperture of the horn antenna.

2. The horn antenna of claim 1, wherein the second width is less than about 75% of the first width.

3. The horn antenna of claim 1, wherein the second portion has a cuboid shape.

4. The horn antenna of claim 1, wherein the slab abruptly transitions from having the first width to having the second width at a boundary between the first portion and the second portion.

5. The horn antenna of claim 1, wherein the first and second portions of the slab have a same thickness.

6. The horn antenna of claim 1, wherein the second portion is centered with respect to the first portion along a direction parallel to the first and second widths.

7. The horn antenna of claim 1, further comprising:

a body having a cylindrical shape and an opening that defines a position of the aperture;

wherein the slab is positioned at least partially within the body.

8. The horn antenna of claim 7,

wherein the second portion comprises a first end of the slab, wherein the first end is aligned with the opening.

9. The horn antenna of claim 7, further comprising:

an coaxial connector integrated with the body of the antenna.

10. The horn antenna of claim 1, further comprising:

a choke displaced from the aperture of the horn antenna by a distance of between 0.55λ

_center and 0.61λ

_center inclusive, where λ

_center is a wavelength of a radio wave at a center frequency of a radio frequency band upon which the horn antenna is designed to operate.

11. The horn antenna of claim 9, wherein the choke is displaced from the aperture towards the waveguide along a direction normal to a plane of the aperture.

12. The horn antenna of claim 1, wherein the second portion of the slab comprises a first end of the slab that is substantially flat and is positioned within a plane of the aperture.

13. The horn antenna of claim 1, wherein a height of the second portion of the slab is chosen such that the circular polarizer matches the impedance of the waveguide to the impedance of air.

14. The horn antenna of claim 1, wherein the waveguide comprises a rectangular waveguide, and wherein the horn antenna further comprises a waveguide transition coupling the rectangular waveguide to the circular polarizer.

15. The horn antenna of claim 1, wherein the horn antenna has a beamwidth that varies by less than 5°

over an operating frequency range of at least 14 GHz.

16. The horn antenna of claim 15, wherein the beamwidth is about 90°

.

17. A horn antenna, comprising:

a choke displaced from an aperture of the horn antenna by a distance of between 0.55λ

_center and 0.61λ

_center inclusive, where λ

_center is a wavelength of a radio wave at a center frequency of a radio frequency band upon which the horn antenna is designed to operate.

18. The horn antenna of claim 17, further comprising:

a body having an opening that defines a position of the aperture.

19. The horn antenna of claim 17, wherein a portion of the choke nearest the aperture is positioned a distance of 0.58λ

_center from the aperture.

20. The horn antenna of claim 17, wherein the horn antenna has a beamwidth that varies by less than 5°

over an operating frequency range of at least 14 GHz.