Ground-based, wavefront-projection beamformer for a stratospheric communications platform

• US 6,380,893 B1
• Filed: 09/05/2000
• Issued: 04/30/2002
• Est. Priority Date: 09/05/2000
• Status: Expired due to Term

• Current Assignee: Hughes Electronics Corporation (Rtx Corporation)
• Original Assignee: Hughes Electronics Corporation (Rtx Corporation)
• Inventors: Chang, Donald C. D., Hagen, Frank A., Wang, Weizheng, Yung, Kar
• Primary Examiner(s): Blum, Theodore M.
• Application Number:
  US09/655,041
• Time in Patent Office: 602 Days
• Field of Search: 342/373, 342/372, 342/354, 342/157
• US Class Current: 342/373
• CPC Class Codes: H01Q 25/00 Antennas or antenna systems providing at least two radiating patterns arrangements for changing or varying the orientation or the shape of the directional pattern H01Q3/00
• CPC Class Codes: H01Q 3/26 varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture H01Q3/12, H01Q3/22, H01Q3/24 take precedence
• CPC Class Codes: H01Q 3/30 varying the relative phase between the radiating elements of an array H01Q3/2605, H01Q3/2658, H01Q3/2682, H01Q3/44 take precedence

Abstract

A method for beamforming signals for an array of receiving or transmitting elements includes the steps of selecting a beam elevation and azimuth and grouping elements of an antenna array into element ensembles that are substantially aligned with a wavefront projection on the antenna array corresponding to the selected beam elevation and azimuth.

Claims

1. A method for beamforming comprising the following steps:

(a) selecting a beam elevation and azimuth; and

(b) grouping elements of an antenna array into element ensembles that are substantially aligned with a wavefront projection on the antenna array corresponding to the selected beam elevation and azimuth.

2. The method of claim 1 further comprising the step of (c) calculating an ensemble signal sum for each of the element ensembles.

3. The method of claim 2 further comprising the step of (d) calculating a compensation phasor for each of the element ensembles from a phase progression increment to generate a phase weighted projection signal for each of the element ensembles.

4. The method of claim 3 further comprising the step (e) of summing the phase weighted projection signals.

5. The method of claim 4 further comprising the step (f) of outputting the summed phase weighted projection signals to a corresponding beam port for the selected beam elevation and azimuth.

6. The method of claim 1 further comprising the step (c) of calculating a back-projection signal onto the elements of each of the element ensembles.

7. The method of claim 6 further comprising the step (d) of outputting the back-projection signal to the antenna elements.

8. The method of claim 7 wherein multiple back-projection beams are calculated and added at the antenna elements to form a summed back-projection signal.

9. The method of claim 7 further comprising the step (e) of outputting the summed back-projection signal to the antenna elements.

10. The method of claim 2 wherein step (c) comprises normalizing each of the element ensemble sums by the number of elements in each of the element ensembles respectively.

11. The method of claim 1 wherein step (b) comprises calculating the wavefront projection on the antenna array corresponding to a phase correction value for each of the element ensembles.

12. The method of claim 11 wherein step (a) comprises associating selected antenna elements with a particular wavefront projection.

13. The method of claim 12 wherein the selected antenna elements associated with each wavefront projection respectively define the element ensembles.

14. The method of claim 12 wherein the selected antenna elements are grouped by rows if ||azimuth|−

90°

|>

45° and

by columns otherwise.

15. The method of claim 14 wherein two antenna elements from each group are interpolated to the position of the wavefront projection.

16. The method of claim 15 wherein each element ensemble contains all of the interpolated values from each group for a particular wavefront projection.

17. The method of claim 1 wherein the antenna array is mounted on a stratospheric platform.

18. The method of claim 17 wherein the antenna elements are linked to a ground station.

19. A beamformer comprising:

a beam selector for selecting a desired beam elevation and azimuth; and

an ensemble selector for grouping elements of an antenna array into element ensembles that are substantially aligned with a wavefront projection on the antenna array corresponding to the selected beam elevation and azimuth.

20. The beamformer of claim 19 further comprising an ensemble sum calculator for calculating an element ensemble sum signal for each element ensemble.

21. The beamformer of claim 20 wherein the ensemble sum calculator normalizes the element ensemble sum signal for each element ensemble.

22. The beamformer of claim 20 further comprising a phase compensation calculator for calculating a phase weighted projection signal for each element ensemble.

23. The beamformer of claim 22 further comprising a phasor product summer for summing the phase weighted projection signals.

24. The beamformer of claim 19 further comprising a back-projection signal calculator for calculating a back-projection signal for each antenna element from the phase weighted projection signals.

25. The beamformer of claim 24 further comprising a back-projection signal summer for summing multiple back-projection signals at each antenna element corresponding to different transmit beams.

26. The beamformer of claim 20 wherein the ensemble selector calculates the wavefront projection on the antenna array corresponding to a phase correction value for each of the element ensembles.

27. The beamformer of claim 26 wherein the ensemble selector associates selected antenna elements with the wavefront projection.

28. The beamformer of claim 27 wherein the selected antenna elements are grouped by rows if ||azimuth|−

90°

|>

45° and

by columns otherwise.

29. The beamformer of claim 28 wherein two antenna elements from each group nearest to the wavefront projection are interpolated.

30. The beamformer of claim 28 wherein the element ensemble contains the interpolated value from each group.

31. The beamformer of claim 28 wherein each element ensemble contains the two antenna elements from each group nearest to the wavefront projection.

32. The beamformer of claim 19 further comprising a stratospheric platform on which the antenna array is mounted.

33. The beamformer of claim 19 further comprising a ground station linking the beamformer to the stratospheric platform.