Phase-only reconfigurable multi-feed reflector antenna for shaped beams

• US 6,456,252 B1
• Filed: 10/23/2000
• Issued: 09/24/2002
• Est. Priority Date: 10/23/2000
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Goyette, Guy
• Primary Examiner(s): Wong, Don
• Assistant Examiner(s): NGUYEN, HOANG V
• Application Number:
  US09/694,994
• Time in Patent Office: 701 Days
• Field of Search: 343/853, 343/779, 343/778, 343/781.R, 343/782, 343/840
• US Class Current: 343/779
• CPC Class Codes: H01Q 19/17 the primary radiating source comprising two or more radiating elements H01Q19/15, H01Q25/00 take precedence
• CPC Class Codes: H01Q 25/002 providing at least two patterns of different beamwidth; Variable beamwidth antennas
• CPC Class Codes: H01Q 25/007 using two or more primary active elements in the focal region of a focusing device for operation on different wavebands H01Q5/22
• CPC Class Codes: H01Q 3/2658 Phased-array fed focussing structure

Abstract

A method and apparatus for reconfigurably transmitting shaped beam satellite signals via reflector array antennas are disclosed. The apparatus comprises a reflector for reflecting RF signals having a reflector focal plane and a feed array comprising a plurality of feed elements wherein said feed array is defocused from said reflector focal plane, yet produces a wavefront substantially similar to a wavefront that would be produced by a feed array located at the reflector focal plane. The method of transmitting a signal in accordance with the present invention comprises forming a wavefront with a feed array, wherein said feed array is defocused from a reflector focal plane, yet produces a wavefront substantially similar to a wavefront that would be produced by a feed array located at the reflector focal plane and reflecting said wavefront to a coverage area.

Claims

1. An antenna system for transmitting a signal comprising:

a reflector for reflecting a signal beam having a reflector focal plane; and

a feed array for producing a wavefront substantially similar to a wavefront that would be produced by a feed array located at said reflector focal plane, the feed array including a plurality of feed elements;

a Beam Forming Network (BFN) having a variable phase shifter for each signal of said feed elements wherein the wavefront is produced by varying only a phase for each signal of said feed elements while a gain of each signal remains substantially fixed; and

at least one amplifier amplifying each phase shifted signal of each of said plurality of feed elements by a substantially fixed gain.

2. The antenna system of claim 1, wherein each said variable phase shifter performs phase shifting of at least five-bit quantization.

3. The antenna system of claim 1, wherein said reflector reflects the wavefront to a coverage area, said coverage area being reconfugurable in shape and scan by reconfiguring said variable phase shifters.

4. The antenna system of claim 1, wherein the feed element size is greater the one wavelength.

5. The antenna system of claim 1, wherein the at least one amplifier produces a substantially circularly symmetric taper at the feed array with a maximum at a center of the feed array.

6. The antenna system of claim 1, wherein the reflector possesses an offset with respect to a focal length of the reflector allowing the feed array to be defocused without substantially blocking the reflector.

7. The antenna system of claim 1, further comprising a reflector gimbal mechanism for repainting a boresight of the reflector.

8. The antenna system of claim 7, wherein said reflector gimbal mechanism provides at least ±

2°

of range for repointing the boresight of the reflector.

9. A method of transmitting a signal comprising:

forming a wavefront with a feed array, wherein said feed array is defocused from a reflector focal plane yet produces a wavefront substantially similar to a wavefront that would be produced by a feed array located at the reflector focal plane, the step of forming further comprising the substeps of;

varying only the phase for each signal of a plurality of feed elements in a Beam Forming Network (BFN) while a gain of each signal remains substantially fixed; and

amplifying each signal of the plurality of feed elements by a substantially fixed gain to produce the wavefront; and

reflecting said wavefront to a coverage area.

10. The method of claim 9, wherein phase shifting is performed with at least five-bit quantization.

11. The method of claim 9, wherein said coverage area is reconfigurable in shape and scan by variably phase shifting the signal at each of said plurality of feed elements.

12. The method of claim 9, wherein the feed element size is greater than one wavelength.

13. The method of claim 9, wherein amplifying the signal at a fixed gain produces a substantially circularly symmetric taper with a maximum at a center of the taper.

14. The method of claim 9, wherein reflecting the wavefront is performed with an offset with respect to a focal axis of the reflector allowing the feed array to be defocused without substantially blocking the reflector.

15. The method of claim 9, further comprising repointing a boresight of the reflector.

16. The method of claim 15, wherein said reflector boresight is repointed with a range of at least ±

2°

.

17. An antenna feed network comprising:

a Beam Forming Network (BFN) having;

a signal divider for dividing an input signal into a plurality of divided signals;

a plurality of variable phase adjusters, said variable phase adjusters each receiving one of the plurality of divided signals and outputting a phase adjusted signal; and

at least one fixed gain amplifier for amplifying each phase adjusted signal by a fixed gain and outputting an amplified signal for each phase adjusted signal;

a feed array defocused from a reflector, said feed array comprising a plurality of feed elements, each feed element receiving the amplified signal and radiating a radiated signal, the combination of the radiated signals of each feed element forming a wavefront;

wherein the feed array produces the wavefront by varying only a phase for each divided signal of said feed elements while a gain of each divided signal remains substantially fixed.

18. The antenna feed network of claim 17, wherein each said variable phase shifter performs phase shifting of at least five-bit quantization.

19. The antenna feed network of claim 17, wherein said reflector reflects the wavefront to a coverage area, said coverage area being reconfigurable in shape and scan by reconfiguring said variable phase shifters.

20. The antenna feed network of claim 17, wherein the feed element size is greater than one wavelength.

21. The antenna feed network of claim 17, wherein the at least one amplifier produces a substantially circularly symmetric taper at the feed array with a maximum at a center of the feed array.

22. The antenna feed network of claim 17, wherein the reflector possesses an offset with respect to a focal length of the reflector allowing the feed array to be defocused without substantially blocking the reflector.

23. The antenna feed network of claim 17, further comprising a reflector gimbal mechanism for repointing a boresight of the reflector.

24. The antenna feed network of claim 23, wherein said reflector gimbal mechanism provides at least ±

2°

of range for repointing the boresight of the reflector.

25. A wavefront produced by a feed array comprising a plurality of feed elements, wherein said feed array is defocused from a reflector focal plane yet produces a wavefront substantially similar to a wavefront that would be produced by a feed array located at the reflector focal plane;

wherein the feed array produces the wavefront by varying only a phase for a signal to each of said feed elements while a gain of each signal remains substantially fixed.

26. An antenna system for transmitting a signal comprising;

a means for reflecting signal having a focal plane; and

a means for generating a signal wavefront with a plurality of feed elements substantially similar to a wavefront that would be produced by a feed array located at said focal plane;

wherein the means for generating the signal wavefront produces the wavefront by varying only a phase for a signal to each of said feed elements while a gain of each signal remains substantially fixed.