Multi-arm elliptic logarithmic spiral arrays having broadband and off-axis application

• US 6,583,768 B1
• Filed: 01/18/2002
• Issued: 06/24/2003
• Est. Priority Date: 01/18/2002
• Status: Expired due to Fees

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Underbrink, James R.
• Primary Examiner(s): LE, HOANGANH T
• Application Number:
  US10/051,235
• Time in Patent Office: 522 Days
• Field of Search: H01/Q 2.100, 343/893, 343/700.MS, 343/895, 343/769, 343/770, 381/92, 367/905
• US Class Current: 343/893
• CPC Class Codes: H01Q 11/10 Logperiodic antennas H01Q11/08 takes precedence
• CPC Class Codes: H01Q 9/27 Spiral antennas
• CPC Class Codes: Y10S 367/905 Side lobe reduction or shading

Abstract

A multi-arm elliptic logarithmic spiral array that is particularly effective in off-axis beamforming applications. The array is formed by providing an elliptic logarithmic spiral and a plurality of concentric ellipses which intersect with angularly spaced apart sample points on the elliptic logarithmic spiral. An odd number of sample points are included on each ellipse. The array of the present invention is particularly effective in off-axis beamforming applications, such as aeroacoustic test applications within wind tunnels, where the location of the array is fixed and the source of noise is positioned off axis of the array.

Claims

1. A non-redundant planar array for reducing sidelobes in at least one of source maps and projected beams during beam forming, said array comprising:

an elliptical logarithmic spiral having a plurality of sample points spaced apart thereon;

a plurality of multi-arm elliptic logarithmic arrays formed by a plurality of ellipses, wherein said ellipses are each formed off of a respective one of said sample points on said elliptical logarithmic spiral so as to each intersect a respective one of said sample points;

wherein each said ellipse includes an odd number of equi-angularly spaced sample points; and

wherein a plurality of array elements are disposed at said sample points.

2. The array of claim 1, wherein said ellipses are formed concentrically with one another.

3. The array of claim 1, wherein each said ellipse includes an odd number of equi-angularly spaced sample points over a 2 TT angle.

4. The array of claim 1, wherein each said ellipse has a major and a minor axis, and wherein said major axes are all orientated in a direction in accordance with a primary look direction of the array, and wherein minor axes of each said array are orientated perpendicular to said major axes.

5. A non-redundant planar array for reducing sidelobes in source maps or projected beams during off axis beam forming, said array comprising:

an elliptical logarithmic spiral having a plurality of sample points spaced apart thereon;

a plurality of multi-arm elliptic logarithmic arrays formed by a plurality of ellipses, wherein said ellipses are each formed off of a respective one of said sample points on said elliptical logarithmic spiral so as to each intersect a respective one of said sample points;

wherein each said ellipse includes an odd number of equi-angularly spaced sample points and said ellipses are disposed concentrically with one another; and

wherein a plurality of array elements are disposed at said sample points.

6. The array of claim 5, wherein each said ellipse has an eccentricity in accordance with an eccentricity of an ellipse used to determine a maximum radius of said elliptical logarithmic spiral.

7. The array of claim 5, wherein each said ellipse includes an odd number of equi-angularly spaced sample points over a 2 TT angle.

8. The array of claim 5, wherein each said ellipse has a major and a minor axis, and wherein said major axes are all orientated in a direction in accordance with a primary look direction of the array, and wherein minor axes of each said ellipse are orientated perpendicular to said major axes.

9. A method for forming a non-redundant planar array having reduced sidelobes in source maps or projected beams during off axis beam forming, said method comprising:

forming an elliptical logarithmic spiral having a maximum desired radius;

selecting a plurality of angularly spaced apart sample points on said elliptical logarithmic spiral;

forming a plurality of multi-arm elliptic logarithmic arrays via a plurality of ellipses, wherein said ellipses are each formed to intersect a respective one of said sample points on said elliptical logarithmic spiral;

including an odd number of equi-angularly spaced sample points on each said ellipse; and

disposing an array element at a plurality of said sample points.

10. The method of claim 9, further comprising arranging said ellipses concentrically with one another.

11. The method of claim 9, further comprising providing each said ellipse with an eccentricity in accordance with an eccentricity of a reference ellipse used to determine a maximum radius of said elliptical logarithmic spiral.

12. The method of claim 9, further comprising:

forming each said ellipse with a major axis and a minor axis, and wherein said major axes are all orientated in a direction in accordance with a primary look direction of the array, and wherein minor axes of each said ellipse are orientated perpendicular to said major axes.

13. The method of claim 9, further comprising spacing said sample points over a 2 TT angle on each said ellipse.