Intermodulation suppression for transmit active phased array multibeam antennas with shaped beams

• US 6,831,600 B1
• Filed: 03/23/2004
• Issued: 12/14/2004
• Est. Priority Date: 08/26/2003
• Status: Active Grant

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: Cherrette, Alan, Cleaveland, Bryan, Lier, Erik
• Primary Examiner(s): Phan, Dao
• Application Number:
  US10/806,776
• Time in Patent Office: 266 Days
• Field of Search: 342/81, 342/154, 342/368, 342/371, 342/372, 342/373, 455/67.11, 455/202, 455/203, 455/450
• 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

Abstract

Methods and apparatus are provided for determining aperture phase distributions for use in radiating signals with an active phased array antenna having multiple beams and multiple carriers. Distinct initial phase distributions corresponding to the carriers are allocated. The initial phase distributions are modified for each of the carriers to generate respective radiation patterns that substantially correspond to respective coverage areas in accordance with amplification and radiation of signals having the initial phase distributions. The modified phase distributions are optimized to simultaneously increase carrier-signal power and reduce an intermodulation product radiated in the respective coverage areas in accordance with amplification and radiation of signals having the modified phase distributions.

Claims

1. A method for determining aperture phase distributions for use in radiating signals with an active phased array antenna having a plurality of shaped beams and a plurality of carriers, the method comprising:

allocating distinct initial aperture phase distributions corresponding to the plurality of carriers; and

optimizing the aperture phase distributions to simultaneously increase carrier-signal power and reduce an intermodulation product radiated in the respective coverage areas in accordance with amplification and radiation of signals having the modified aperture phase distributions.

2. The method recited in claim 1 further comprising modifying the initial aperture phase distributions for each of the plurality of carriers to generate respective radiation patterns that substantially correspond to respective coverage areas in accordance with amplification and radiation of signals having the initial aperture phase distributions.

3. The method recited in claim 1 wherein the respective coverage areas for the plurality of carriers are substantially the same.

4. The method recited in claim 1 wherein at least one of the initial aperture phase distributions is substantially paraboloidal.

5. The method recited in claim 1 wherein at least one of the initial aperture phase distributions is substantially hyperbolically paraboloidal.

6. The method recited in claim 1 wherein a first of the initial aperture phase distributions has two or more orthogonal planes of symmetry about an axis orthogonal to an aperture plane and a second of the initial aperture phase distributions is asymmetric about the axis.

7. The method recited in claim 1 wherein a second of the initial aperture phase distributions is substantially related to a first of the initial aperture phase distributions by complex conjugation and 180°

rotation of underlying complex aperture voltage distributions.

8. The method recited in claim 1 wherein the intermodulation product comprises a third-order intermodulation product.

9. The method recited in claim 1 wherein the intermodulation product comprises a fifth-order intermodulation product.

10. The method recited in claim 1 wherein the intermodulation product comprises an in-band intermodulation product.

11. The method recited in claim 1 wherein the active phased array antenna further comprises a second plurality of carriers, the method further comprising:

allocating second initial aperture phase distributions corresponding to the second plurality of carriers, each such second initial aperture phase distribution being substantially equal to one of the initial aperture phase distributions;

modifying the second initial aperture phase distributions for each of the second plurality of carriers to generate respective radiation patterns that substantially correspond to respective coverage areas in accordance with amplification and radiation of signals having the second initial aperture phase distributions; and

optimizing the modified second aperture phase distributions to simultaneously increase carrier-signal power and reduce an intermodulation product radiated in the respective coverage areas in accordance with amplification and radiation of signals with the modified aperture phase distributions and second modified aperture phase distributions.

12. The method recited in claim 11 wherein each of the plurality of carriers and the second plurality of carriers is less than five in number.

13. A method for radiating a plurality of shaped beams with an active phased array antenna having a plurality of carriers, wherein the beams have aperture phase distributions determined with the method recited in claim 1.

14. A method for radiating a plurality of shaped beams with an active phased array antenna having a plurality of carriers, the method comprising:

radiating a first of the plurality of shaped beams with a first of the plurality of carriers; and

radiating a second of the plurality of shaped beams with a second of the plurality of carriers,

wherein the plurality of shaped beams have aperture phase distributions determined in accordance with the following;

allocating distinct initial aperture phase distributions corresponding to the plurality of carriers;

modifying the initial aperture phase distributions for each of the plurality of carriers to generate respective radiation patterns that substantially correspond to respective coverage areas in accordance with amplification and radiation of signals having the initial aperture phase distributions; and

optimizing the modified aperture phase distributions to simultaneously increase carrier-signal power and reduce an intermodulation product radiated in the respective coverage areas in accordance with amplification and radiation of signals having the modified aperture phase distributions.

15. The method recited in claim 14 wherein the respective coverage areas for the plurality of carriers are substantially the same.

16. The method recited in claim 14 wherein at least one of the initial aperture phase distributions is substantially paraboloidal.

17. The method recited in claim 14 wherein at least one of the initial aperture phase distributions is substantially hyperbolically paraboloidal.

18. The method recited in claim 14 wherein a first of the initial aperture phase distributions is rotationally symmetric about an axis orthogonal to an aperture plane and a second of the initial aperture phase distributions is asymmetric about an axis orthogonal to the aperture plane.

19. The method recited in claim 14 wherein a second of the initial aperture phase distributions is substantially related to a first of the initial aperture phase distributions by complex conjugation and 180°

rotation of underlying complex aperture voltage distributions.

20. The method recited in claim 14 wherein the intermodulation product comprises a third-order intermodulation product.

21. The method recited in claim 14 wherein the intermodulation product comprises a fifth-order intermodulation product.

22. The method recited in claim 14 wherein the intermodulation product comprises an in-band intermodulation product.

23. The method recited in claim 14 wherein the active phased array antenna further comprises a second plurality of carriers, the method further comprising:

radiating a third of the plurality of shaped beams with a first of the second plurality of carriers;

radiating a fourth of the plurality of shaped beams with a second of the second plurality of carriers,

wherein the plurality of shaped beams have aperture phase distributions further determined in accordance with the following;

allocating second initial aperture phase distributions corresponding to the second plurality of carriers, each such second initial aperture phase distribution being substantially equal to one of the initial aperture phase distributions;

modifying the second initial aperture phase distributions for each of the second plurality of carriers to generate respective radiation patterns that substantially correspond to respective coverage areas in accordance with amplification and radiation of signals having the second initial aperture phase distributions; and

optimizing the modified second aperture phase distributions to simultaneously increase carrier-signal power and reduce an intermodulation product radiated in the respective coverage areas in accordance with amplification and radiation of signals with the modified aperture phase distributions and second modified aperture phase distributions.

24. The method recited in claim 23 wherein each of the plurality of carriers and the second plurality of carriers is less than five in number.

25. An active phased array antenna comprising:

a plurality of antenna elements;

a plurality of filter elements coupled with the antenna elements;

a plurality of amplifier elements coupled with the filter elements;

a plurality of beam ports; and

a beamformer having a plurality of elemental paths for coupling the beam ports with the amplifier elements, wherein the beamformer includes phase shifters adapted to provide aperture phase distributions per beam to the amplifier elements in accordance with the following;

allocating distinct initial aperture phase distributions corresponding to the plurality of amplifier elements; and

optimizing the aperture phase distributions to simultaneously increase carrier-signal power and reduce an intermodulation product radiated in the respective coverage areas in accordance with amplification and radiation of signals having the modified aperture phase distributions with the amplifier elements and antenna elements.

26. The active phased array antenna recited in claim 25 wherein the beamformer is further adapted to modify the initial aperture phase distributions for each of the plurality of amplifier elements to generate respective radiation patterns that substantially correspond to respective coverage areas in accordance with amplification and radiation of signals having the initial aperture phase distributions with the amplifier elements and antenna elements.

27. The active phased array antenna recited in claim 25 wherein the respective coverage areas for the plurality of carriers are substantially the same.

28. The active phased array antenna recited in claim 25 wherein at least one of the initial aperture phase distributions is substantially paraboloidal.

29. The active phased array antenna recited in claim 25 wherein at least one of the initial aperture phase distributions is substantially hyperbolically paraboloidal.

30. The active phased array antenna recited in claim 25 wherein a first of the initial aperture phase distributions is rotationally symmetric about an axis orthogonal to an aperture plane and a second of the initial aperture phase distributions is asymmetric about an axis orthogonal to the aperture plane.

31. The active phased array antenna recited in claim 25 wherein a second of the initial aperture phase distributions is substantially related to a first of the initial aperture phase distributions by complex conjugation and 180°

rotation of underlying complex aperture voltage distributions.

32. The active phased array antenna recited in claim 25 wherein the intermodulation product comprises a third-order intermodulation product.

33. The active phased array antenna recited in claim 25 wherein the intermodulation product comprises a fifth-order intermodulation product.

34. The active phased array antenna recited in claim 25 wherein the intermodulation product comprises an in-band intermodulation product.

35. The active phased array antenna recited in claim 25 wherein the phase shifters are further adapted to provide aperture phase distributions to the amplifier elements in accordance with the following:

allocating second initial aperture phase distributions corresponding to the second plurality of amplifier elements, each such second initial aperture phase distribution being substantially equal to one of the initial aperture phase distributions;

modifying the second initial aperture phase distributions for each of the second plurality of amplifier elements to generate respective radiation patterns that substantially correspond to respective coverage areas in accordance with amplification and radiation of signals having the second initial aperture phase distributions with the amplifier elements and antenna elements; and

optimizing the modified second aperture phase distributions to simultaneously increase carrier-signal power and reduce an intermodulation product radiated in the respective coverage areas in accordance with amplification and radiation of signals having the modified aperture phase distributions and second modified aperture phase distributions with the amplifier elements and antenna elements.