Adaptive multiple interference tracking and cancelling antenna

• US 4,500,883 A
• Filed: 03/07/1983
• Issued: 02/19/1985
• Est. Priority Date: 03/07/1983
• Status: Expired due to Fees

• Current Assignee: United States Of America As Represented By The Secretary Of The Army (Government of the United States of America)
• Original Assignee: The United States Of America As Represented By The Secretary Of The Army
• Inventors: Gutleber, Frank S.
• Primary Examiner(s): Lieberman, Eli
• Assistant Examiner(s): Wimer, Michael C.
• Application Number:
  US06/472,793
• Time in Patent Office: 715 Days
• Field of Search: 343/844, 343/853, 343/380, 343/383, 343/423, 343/426, 343/428, 343/430, 343/374
• US Class Current: 342/383
• CPC Class Codes: H01Q 3/2617 Array of identical elements

Abstract

An array antenna comprised of n individual elements where n is an integer wer of the base two. The individual elements have predetermined space code positions N which are varied by means of a plurality of tracking loops comprised of a portion of receiver apparatus coupled to the array and a null seeking detector which is adapted to vary the space code positions of the elements such that the elements are selectively spaced at respective N'"'"' locations relative to the N locations to provide a predetermined 180° phase difference between sets of elements operating in pairs at each space angle of arrival of each of M interference signals whereby a null and substantially complete cancellation of the interfering sources are simultaneously provided while retaining the ability to receive the desired signal at its peak received value.

Claims

1. An adaptive array antenna for cancelling undesired signals received thereby, comprising:

a plurality of antenna elements;

means for varying the space coded positions of said plurality of antenna elements in response to a control signal to provide a 180°

phase difference between one half of the number of said plurality of antenna elements with respect to the other half of the number of said antenna elements for an undesired signal arriving at a certain space angle relative to an axis of said antenna;

receiver means coupled to said antenna elements and including means for detecting and providing an output signal of said undesired signal; and

means responsive to the amplitude of said undesired output signal for generating said control signal whereby said varying means varies said spacing between said halves of antenna elements until a null of said output signal occurs and said undesired signal is cancelled.

2. The array antenna as defined by claim 1 wherein said receiver means and said means for generating said control signal are coupled in a closed loop control circuit between said antenna elements and said means for varying the space code positions thereof.

3. The antenna as defined by claim 2 wherein said means for generating a control signal additionally includes null signal detector means.

4. The array antenna as defined by claim 3 wherein said undesired signal comprises an interference signal from an external source and wherein said antenna elements have a first coded space position relative to said other half of said antenna elements in absence of said interference signal and a second coded space position when said predetermined interference signal is present, said spacing between said first and second code spacing being an incremental spacing equal to 1/2K where K is related to a space angle θ

by the expression d/λ

sin θ

, where d is equal to the length of the array of said plurality of antenna elements divided by the space code positions of said one and other halves of said plurality of antenna elements in absence of said interference signal and λ

is equal to wavelength.

5. The array antenna as defined by claim 4 wherein said plurality of antenna elements comprises n elements where n is an integer power of the base 2.

6. The array antenna as defined by claim 5 wherein said one and said other half of the number of said antenna elements comprise first and second sub-arrays each comprised of n/2 elements.

7. The array antenna as defined by claim 6 wherein said means for varying the space code positions comprises motor means coupled to said n/2 elements of said first sub-array for moving said n/2 elements in unison relative to said n/2 elements of said second sub-array.

8. The array antenna as defined by claim 7 and wherein said closed loop additionally includes signal filter coupled between said null signal detector means and said motor means.

9. The array antenna as defined by claim 6 wherein said means for varying the space coded positions comprises means for electronically varying the space coding of said n/2 elements of said first sub-array relative to said n/2 elements of said second sub-array.

10. The array antenna as defined by claim 9 wherein said means for electronically varying the space coding of said first and second sub-arrays comprises a switch matrix coupled to said n antenna elements and control means responsive to said control signal for selectively activating said switch matrix.

11. The array antenna as defined by claim 10 and additionally including signal filter means coupled between said control signal generating means and said control means.

12. The array antenna as defined by claim 11 wherein said control means comprises a control signal processor.

25. The array antenna as defined by claim 11 wherein said control means comprises a signal processor.

13. An adaptive array antenna for cancelling a plurality of interference signals received thereby, comprising:

a plurality of antenna elements;

means for varying the space coded positions of said plurality of antenna elements in sets of antenna elements equal in number to the number of said plurality of interference signals received, said varying means being responsive to a control signal for each said interference signal to provide a respective 180°

phase difference between one half the number of antenna elements in each set relative to the other half of elements in said set for each space angle of arrival for the plurality of interference signals received;

receiver means coupled to said antenna elements and including means for detecting said plurality of interference signals and providing a composite output signal of the detected plurality of interference signals; and

means responsive to the amplitude of said output signal for generating a respective control signal for each interference signal detected, said respective control signal being applied to said varying means to vary the space coded positions of said sets of said antenna elements in a predetermined sequence until a null for each interference signal occurs as indicated by the amplitude of said output signal to provide said respective 180°

phase differences whereby said interference signals are cancelled.

14. The array antenna as defined by claim 13 wherein said receiver means and said means for generating a control signal comprise a portion of a plurality of closed loop control circuits, one for each interference signal, coupled between said antenna elements and said means for varying the space code positions of said antenna elements.

15. The array antenna as defined by claim 14 wherein each set of antenna elements have a first coded space position relative to said other half of said antenna elements in said set in absence of said interference signal and a second coded space position when said predetermined interference signal is present, said spacing between said first and second code spacing being an incremental spacing equal to 1/2K where K is related to a space angle θ

, for a respective interference signal, by the expression d/λ

sin θ

where d is equal to the length of the array of said set of a plurality of antenna elements divided by the space code positions of said one and other halves of said set of antenna elements in absence of said interference signal and λ

is equal to wavelength.

16. The array antenna as defined by claim 15 wherein said plurality of antenna elements comprises n elements where n is an integer power of the base 2.

17. The array antenna as defined by claim 16 wherein said n elements repetitively sub-divide in half for each interference signal in sequence into 2^M sets of progressively diminishing number of elements by said space code position varying means, where M is equal to the number of interference signals.

18. The array antenna as defined by claim 17 wherein said means for generating a control signal additionally includes null signal detector means in said plurality of closed loop control circuits.

19. The array antenna as defined by claim 18 wherein said means for varying the space code positions of said antenna elements comprises plural motor means respectively coupled to said null signal detector means and being selectively coupled to said sets of antenna elements to progressively move one half the elements of each set in unison relative to the other half of the elements in said set.

20. The array antenna as defined by claim 19 wherein each of said closed loop control circuits additionally include respective signal filter means coupled between said null signal detector means and said plural motor means.

21. The array antenna as defined by claim 20 wherein said null signal detector means comprises a respective null signal detector in each closed loop control circuit.

22. The array antenna as defined by claim 18 wherein said means for varying the space coded positions comprises means for electronically varying the space coding of said sets of antenna elements.

23. The array antenna as defined by claim 22 wherein said means for electronically varying the space coding comprises a switch matrix coupled to said plurality of antenna elements and control means therefor responsive to respective control signals generated by said plurality of closed loop control circuits for selectively activating said switch matrix.

24. The array antenna as defined by claim 23 and additionally including respective signal filter means in said plurality of closed loop control circuits coupled between said control means and said null signal detector means.