Broad beam antenna design for a tilted phased array with platform motion

• US 8,604,976 B1
• Filed: 08/25/2011
• Issued: 12/10/2013
• Est. Priority Date: 08/25/2011
• Status: Active Grant

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Chang, Kaichiang, Kennedy, William
• Primary Examiner(s): Phan, Dao
• Application Number:
  US13/217,506
• Time in Patent Office: 838 Days
• Field of Search: 342/81, 342/154, 342/368, 342/372, 342/373, 342/377
• US Class Current: 342/377
• 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

Embodiments of the present invention are directed to techniques and systems for modifying the transmit beam of a phased array antenna in order to effect a shape change in the beam that pre-compensates for platform motion and clutter considerations in the local environment. The techniques and systems herein disclosed take advantage of the phase controlling capability of phased array antennas to adjust the performance of each element in a way that de-focuses or spoils the transmit beam. This spoiling, in turn, enables the transmission of a broader, tailored beam that provides illumination over an area that would otherwise require multiple scans from narrow transmit beams. The techniques described provide a closed-form solution that sacrifices some antenna pattern efficiency in exchange for greatly reduced computational complexity over prior art, optimal search techniques.

Claims

1. In a beamforming apparatus for a phased array antenna, a method for beamforming in a phased array antenna having a total aperture, comprising:

receiving a specified beam steering vector (BSV);

determining a number of concentric sub-apertures based upon a beam spoiling vector associated with said BSV;

dividing the total aperture into the determined number of concentric sub-apertures;

computing a spoiled BSV for at least one of two orthogonal co-planar dimensions perpendicular to the direction of propagation of a transmit wavefront based on the BSV;

applying the spoiled BSV in divergent directions for each sub-aperture by;

for each element i in each of said sub-apertures, computing a beam steering phase coefficient, where said beam steering phase coefficient is determined by the equation

2. The method of claim 1, wherein the number of sub-apertures is determined by the desired level of non-homogeneity across the total aperture.

3. The method of claim 1, wherein the number of sub-apertures range from one to the square root of the number of elements in the total aperture times π

.

4. The method of claim 1, wherein said sub-aperture beam steering phase coefficient computation is performed in parallel for all said sub-apertures.

5. An apparatus for beam forming in a phased array antenna having a total aperture, comprising:

a communications processor configured to process INS data to determine a beam pointing vector and a beam spoiling vector;

a beam spoiler operatively connected to said communications processor and configured to compute phase coefficients for each element in said total aperture based at least in part on said beam spoiling vector;

a beam steering generator operative coupled to said beam spoiler and said phased array antenna elements and configured to steer said phased array antenna with at least said phase coefficients.

6. The apparatus of claim 5, wherein said total aperture further comprises one or more sub-apertures and wherein said beam spoiler computes said phase coefficients for each element in each of said one or more sub-apertures.

7. The apparatus of claim 6, wherein said sub-aperture phase coefficient computation is performed in parallel for all said sub-apertures.

8. An apparatus for beamforming in a phased array antenna having a total aperture, comprising:

means for receiving a specified beam steering vector (BSV);

means for determining a number of concentric sub-apertures based upon a beam spoiling vector associated with said BSV;

means for dividing the total aperture into the determined number of concentric sub-apertures;

means for computing a spoiled BSV for at least one of two orthogonal co-planar dimensions perpendicular to the direction of propagation of a transmit wavefront based on the BSV;

means for applying the spoiled BSV in divergent directions for each sub-aperture by;

for each element i in each of said sub-apertures, computing a beam steering phase coefficient, where said beam steering phase coefficient is determined by the equation

9. The apparatus of claim 8, wherein the number of sub-apertures is determined by the desired level of non-homogeneity across the total aperture.

10. The apparatus of claim 8, wherein the number of sub-apertures range from one to the square root of the number of elements in the total aperture times π

.

11. The apparatus of claim 8, wherein said sub-aperture beam steering phase coefficient computation is performed in parallel for all said sub-apertures.

12. A computer-readable medium storing a non-transitory computer program executable by at least one computer, the computer program comprising computer instructions for in a phased array antenna having a total aperture:

receiving a specified beam steering vector (BSV);

determining a number of concentric sub-apertures based upon a beam spoiling vector associated with said BSV;

dividing the total aperture into the determined number of concentric sub-apertures;

computing a spoiled BSV for at least one of two orthogonal co-planar dimensions perpendicular to the direction of propagation of a transmit wavefront based on the BSV;

applying the spoiled BSV in divergent directions for each sub-aperture by;

for each element i in each of said sub-apertures, computing a beam steering phase coefficient, where said beam steering phase coefficient is determined by the equation

13. The computer-readable medium of claim 12, wherein the number of sub-apertures is determined by the desired level of non-homogeneity across the total aperture.

14. The computer-readable medium of claim 12, wherein the number of sub-apertures range from one to the square root of the number of elements in the total aperture times π

.

15. The computer-readable medium of claim 12, wherein said sub-aperture beam steering phase coefficient computation is performed in parallel for all said sub-apertures.