Wideband adaptive beamforming methods and systems

• US 10,177,451 B1
• Filed: 09/24/2015
• Issued: 01/08/2019
• Est. Priority Date: 08/26/2014
• Status: Active Grant

• Current Assignee: BAE Systems Space & Mission Systems Incorporated (BAE Systems Plc)
• Original Assignee: Ball Aerospace & Technologies Corporation (Ball Corporation)
• Inventors: Baraban, Mara S., Sauer, Jacob A., Leifer, Mark Curtis, McMillan, Stanton B.
• Primary Examiner(s): Nguyen, Chuong P
• Application Number:
  US14/864,386
• Time in Patent Office: 1,202 Days
• Field of Search: 342379, 342372, 34235759
• CPC Class Codes: G01S 19/21 Interference related issues ; Issues related to cross-correlation, spoofing or other methods of denial of service
• CPC Class Codes: H01Q 1/38 formed by a conductive layer on an insulating support patch antennas H01Q9/0407; microstrip dipole antennas H01Q9/065; microstrip slot antennas H01Q13/106; transmission line microstrip antennas H01Q13/206; manufacturing reflecting surfaces using insulating material for supporting the reflecting surface H01Q15/142
• CPC Class Codes: H01Q 3/2611 Means for null steering; Adaptive interference nulling
• CPC Class Codes: H01Q 9/27 Spiral antennas
• CPC Class Codes: H04B 1/0007 wherein the AD/DA conversion occurs at radiofrequency or intermediate frequency stage
• CPC Class Codes: H04B 1/1027 assessing signal quality or detecting noise/interference for the received signal
• CPC Class Codes: H04B 2001/7152 with means for suppressing interference
• CPC Class Codes: H04B 7/08 at the receiving station
• CPC Class Codes: H04B 7/18506 Communications with or from aircraft, i.e. aeronautical mobile service
• CPC Class Codes: H04K 2203/32 including a particular configuration of antennas
• CPC Class Codes: H04K 3/226 Selection of non-jammed channel for communication spectrum sharing arrangements H04W16/14; selection of wireless resources by user or terminal H04W72/02
• CPC Class Codes: H04K 3/228 Elimination in the received signal of jamming or of data corrupted by jamming interference suppression in receivers H04B1/10

Abstract

Wide band adaptive beam forming methods and systems are provided. The beam forming methods can include receiving signals at multiple antenna elements and digitizing samples of the received signals for some period of time. The samples are divided into sub-channels according to frequency, and interferers are identified as signals appearing across at least some minimum number of the sub-channels. After removing signals not identified as interferers from the collected signal information, that information is used to calculate weights for forming a beam having a null at the identified location of the interferer. The beam forming systems include multiple element antennas having arms in the form of a spiral, and processing hardware for performing adaptive beam forming.

Claims

1. A beam forming system, comprising:

an antenna, the antenna including a plurality of antenna elements;

one or more analog to digital converters, wherein each of the antenna elements is connected to an analog to digital converter; and

a processor, wherein the processor is operable to execute instructions to;

collect samples of the response of each of the antenna elements from the one or more analog to digital converters for a selected period of time;

sort the collected samples by frequency, wherein each of the collected samples is assigned to one of a plurality of frequency bins;

identify a signal present in each of the frequency bins as an interferer;

adjust any signals present in any frequency bin that is not identified as an interferer to a noise floor;

for each frequency bin, calculate a weight to place a null in an antenna beam pattern at a location corresponding to an interferer;

for each frequency bin, apply the calculated weight for a frequency bin to the collected samples associated with that frequency bin to create a weighted signal; and

generate a beam using the weighted signal, wherein the beam includes a null at the location corresponding to the interferer.

2. The beam forming system of claim 1, further comprising:

for each frequency bin, generating a covariance matrix for each of the collected samples associated with the frequency bin; and

performing an Eigen decomposition of each of the covariance matrices to obtain eigenvalues and normalized eigenvectors for each of the covariance matrices.

3. The beam forming system of claim 2, further comprising:

taking dot products between potential interference eigenvectors, wherein identifying a signal present in each of the frequency bins as an interferer includes identifying those signals in at least a selected number of frequency bins that have a dot product of at least a selected magnitude.

4. The beam forming system of claim 3, wherein the selected number of frequency bins is four, and wherein the selected magnitude is 0.9.

5. The beam forming system of claim 3, further comprising:

adjusting eigenvalues that have not been associated with interferers to or below a noise floor.

6. The beam forming system of claim 5, wherein the weight vector w for each frequency bin is calculated from the expression

7. The beam forming system of claim 6, wherein a=v^HUΛ

<sup>−

1</sup>U^Hv.

8. The beam forming system of claim 6, wherein the desired pattern is omnidirectional.

9. The beam forming system of claim 1, wherein each of the antenna elements is disposed on a planar substrate and is connected to a signal line at a feed point, and wherein each of the antenna elements is a spiral shaped element that increases in width from a respective feed point to an outer circumference of the antenna.

10. The beam forming system of claim 9, wherein a sweep angle of each of the antenna elements is between 0°

and 360°

.

11. The beam forming system of claim 9, wherein a sweep angle of each of the antenna elements is about 88°

.

12. The beam forming system of claim 10, wherein the antenna includes eight antenna elements.

13. The beam forming system of claim 9, wherein the width of each of the antenna elements increases logarithmically.

14. The beam forming system of claim 9, wherein a sweep angle of each of the antenna elements is between 1°

to 100°

.

15. The beam forming system of claim 9, wherein a sweep angle of each of the antenna elements is between 80°

to 90°

.

16. The beam forming system of claim 15, wherein the width of each of the antenna elements increases logarithmically.

17. The beam forming system of claim 16, wherein the antenna possesses circular symmetry.

18. The beam forming system of claim 9, wherein each of the plurality of antenna elements is disposed on a planar substrate.

19. The beam forming system of claim 9, wherein the antenna possesses circular symmetry.

20. The beam forming system of claim 1, further comprising:

a digital to analog converter, wherein the weighted signal is converted to an analog signal.

21. The beam forming system of claim 1, further comprising a radio, wherein the radio receives the weighted signal.

22. A method for adaptive beamforming, comprising:

receiving radio waves at a plurality of antenna elements;

collecting samples of the antenna response to the radio waves at each of the antenna elements for a period of time by a processor;

sorting the samples from each of the antenna elements into a plurality of different frequency bins by the processor, wherein each different frequency bin contains information regarding radio waves within a different range of frequencies;

identifying a signal present in multiple ones of the different frequency bins as an interferer by the processor;

after removing signals not identified as an interferer, calculating a plurality of weights to place a null within an antenna beam at a location corresponding to an interferer by the processor; and

applying the weights by the processor to generate a beam having a null in the direction of the interferer.

23. The method of claim 22, further comprising:

digitizing the collected samples, wherein the antenna response for each antenna element is recorded as a complex number representing an amplitude and phase of a received signal at each of a plurality of intervals in time for the period of time.

24. The method of claim 23, wherein sorting the samples from each of the antenna elements into a plurality of different frequency bins includes sorting the digitized collected samples into frequency bins.

25. The method of claim 24, further comprising:

creating a covariance matrix from the information contained for each of the frequency bins.

26. The method of claim 25, further comprising:

performing an Eigen decomposition of the covariance matrices for each of the frequency bins.

27. The method of claim 26, wherein identifying a signal present in multiple ones of the different frequency bins as an interferer includes taking a dot product between potential interference eigenvectors across multiple ones of the different frequency bins, wherein a dot product close to one is taken as an indication that the eigenvectors are associated with an interferer.

28. The method of claim 27, further comprising:

adjusting a value of eigenvalues that are not interferers to the noise floor.

29. The method of claim 28, wherein the weight (w) for each frequency bin is calculated from the expression

30. The method of claim 29, wherein the desired antenna beam pattern is omnidirectional.