Antenna Array with Reduced Mutual Coupling Between Array Elements

• US 20140340271A1
• Filed: 05/16/2013
• Published: 11/20/2014
• Est. Priority Date: 05/16/2013
• Status: Active Grant

• Current Assignee: Maxar Space LLC (Galileo Parent, Inc.)
• Original Assignee: Space Systems/Loral Incorporated (Loral Space and Communications Incorporated)
• Inventors: Simon, Peter S., Petkov, Peter Z.
• Granted Patent: US 9,537,209 B2
• Time in Patent Office: Days
• US Class Current: 343/776
• CPC Class Codes: H01Q 1/523 between antennas of an array
• CPC Class Codes: H01Q 13/0266 provided with a flange or a choke
• CPC Class Codes: H01Q 21/064 using horn or slot aerials slotted waveguides arrays H01Q21/005

Abstract

An array of antenna feed elements includes a plurality of horns, each horn having an aperture and configured for transmission of electromagnetic energy therethrough. At least a first horn is configured with an electrically conductive external surface proximate to the aperture, the external surface contoured so as to reduce mutual coupling between the first horn and an adjacent horn. Where the electromagnetic energy is within a radio frequency (RF) band, the external surface is contoured so as to provide an abrupt change in a gap dimension between the first horn and an adjacent horn, the change occurring at a distance behind the aperture of equal to a multiple of one half the characteristic wavelength of the RF band.

Claims

1. An array of antenna feed elements comprising a plurality of horns, each horn including an aperture at a distal end of the horn, and configured for transmission of electromagnetic energy therethrough, the energy being within a radio frequency (RF) band, at least a first horn being configured with an electrically conductive external surface proximate to the aperture, the external surface being contoured so as to reduce mutual coupling between the first horn and an adjacent horn.

2. The array of claim 1, wherein:

the first horn has an aperture external diameter d_a, and is separated from the adjacent horn by a center to center distance d_c-c;

the external surface is contoured so as to include at least a first portion and a second portion;

the first portion has a length l that extends from a longitudinal position proximate to the aperture toward a proximal end of the horn, the first portion being contoured so as to provide, proximate to each adjacent horn, a first lateral gap between the first portion and an external surface of the adjacent horn, the first lateral gap being approximately constant, throughout length l, length l being approximately n×

λ

/2, where λ

is a characteristic wavelength of the RF band and n is a positive integer; and

the second portion of the external surface extends from the first portion toward an axial position proximate to the distal end, and provides, proximate to the adjacent horn, a second lateral gap significantly larger than the first lateral gap.

3. The array of claim 2, wherein the first lateral gap is approximately equal to the difference between d_c-c and d_a.

4. The array of claim 2, wherein n equals one.

5. The array of claim 2, wherein the first lateral gap is no greater than d_a/10.

6. The array of claim 1, wherein each horn comprises an electrically conductive interior surface.

7. The array of claim 6, wherein the interior surface is shaped as a truncated cone.

8. The array of claim 6, wherein the interior surface includes one or more of a step, a taper, corrugations, and/or ridges.

9. The array of claim 1, wherein a cross section of the first horn, parallel to the aperture, is circular.

10. The array of claim 9, wherein a cross section of the first portion, parallel to the aperture, is a circular annulus.

11. The array of claim 9, wherein a cross section of the first portion, parallel to the aperture, has a circular inner circumference and a scalloped outer circumference.

12. The array of claim 1, wherein a cross section of the first horn, parallel to the aperture, is square, rectangular or hexagonal.

13. The array of claim 1, wherein the horns are disposed in an array that conforms to a geometric plane, or to a surface of revolution having a minimum radius of curvature that is significantly larger than the horn separation d_c-c, or to any other gently curved geometric shape.

14. An antenna feed element configured as a horn, the horn comprising an aperture at a distal end of the horn, and configured for transmission of electromagnetic energy therethrough, the energy being within a radio frequency (RF) band, the horn being configured with an electrically conductive external surface proximate to the aperture, the external surface being contoured so as to reduce mutual coupling between the horn and an adjacent horn.

15. The antenna feed element of claim 14, wherein:

the external surface is contoured so as to include at least a first portion and a second portion;

the first portion has a length l that extends from a longitudinal position proximate to the aperture toward a proximal end of the horn, the first portion being contoured so as to provide, proximate to the adjacent horn, a first lateral gap between the first portion and an external surface of the adjacent horn, the first lateral gap being approximately constant, throughout length l, length l being approximately n×

λ

/2, where λ

is a characteristic wavelength of the RF band and n is a positive integer; and

the second portion of the external surface extends from the first portion toward an axial position proximate to the distal end, and provides, proximate to the adjacent horn, a second lateral gap significantly larger than the first lateral gap.

16. The array of claim 15, wherein n equals one.

17. The antenna feed element of claim 14, wherein the horn comprises an electrically conductive interior surface shaped as a truncated cone.

18. The antenna feed element of claim 17, wherein the interior surface includes one or more of a step, a taper, corrugations, and/or ridges.

19. The antenna feed element of claim 14, wherein a cross section of the horn, parallel to the aperture, is circular, square, rectangular or hexagonal.

20. An antenna system comprising an array of antenna feed elements illuminating a reflector, the array including a plurality of horns, each horn comprising an aperture at a distal end of the horn, and configured for transmission of electromagnetic energy therethrough, the energy being within a radio frequency (RF) band, at least a first horn being configured with an electrically conductive external surface proximate to the aperture, the external surface being contoured so as to reduce mutual coupling between the first horn and an adjacent horn, wherein:

the first horn has an aperture external diameter d_a, and is separated from the adjacent horn by a center to center distance d_c-c;

the external surface is contoured so as to include at least a first portion and a second portion;

the first portion has a length l that extends from a longitudinal position proximate to the aperture toward a proximal end of the horn, the first portion being contoured so as to provide, proximate to each adjacent horn, a first lateral gap between the first portion and an external surface of the adjacent horn, the first lateral gap being approximately constant, throughout length l, length l being approximately n×

λ

/2, where λ

is a characteristic wavelength of the RF band and n is a positive integer; and

the second portion of the external surface extends from the first portion toward an axial position proximate to the distal end, and provides, proximate to the adjacent horn, a second lateral gap significantly larger than the first lateral gap.