Memory efficient jammer locator for a digital adaptive beamforming receiver

• US 6,771,220 B1
• Filed: 03/28/2003
• Issued: 08/03/2004
• Est. Priority Date: 03/28/2003
• Status: Active Grant

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: Gaus, Richard C. Jr., Ashe, Jeffrey M.
• Primary Examiner(s): Blum, Theodore M.
• Application Number:
  US10/402,502
• Time in Patent Office: 494 Days
• Field of Search: 342/417, 342/14, 342/16
• US Class Current: 342/417
• 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: H04K 2203/32 including a particular configuration of antennas
• CPC Class Codes: H04K 3/22 including jamming detection and monitoring

Abstract

A method and computer program product are disclosed for locating signal jammers in a digital beamforming receiver having an antenna with a plurality of associated antenna orientations. An associated antenna gain value is calculated for a first of a sequence of the plurality of antenna orientations at each of a series of sample points. The antenna gain values from the first antenna orientation are evaluated for null spaces to obtain a set of candidate null locations. Associated antenna gain values are calculated and evaluated for subsequent antenna orientations only at the set of candidate null locations. Candidate null locations are eliminated from the set after any evaluation in which they are not found to be null spaces.

Claims

1. A method for locating signal jammers in a digital beamforming receiver having an antenna with a plurality of antenna orientations, comprising:

calculating an associated antenna gain value for a first of a sequence of the plurality of antenna orientations at each of a series of sample points;

evaluating the antenna gain values from the first antenna orientation for null spaces to obtain a set of candidate null locations; and

calculating and evaluating associated antenna gain values for subsequent antenna orientations only at the set of candidate null locations, where a candidate null location is eliminated from the set after any evaluation in which it is not found to be a null space.

2. A method as set forth in claim 1, wherein the method includes an iterative search for a jammer location comprising:

establishing at least one candidate jammer region around one or more candidate null locations remaining after antenna gain values have been evaluated for all antenna orientations; and

iteratively repeating the following steps until the occurrence of a termination event;

subdividing the candidate jammer region into smaller subregions;

selecting the subregion with the lowest antenna gain by calculating antenna gain values at one or more representative points within the subregions; and

replacing the candidate jammer region with the selected subregion.

3. A method as set forth in claim 2, wherein the iterative search is conducted at each candidate jammer region for each antenna orientation, using its associated antenna gain, to obtain a plurality of approximate jammer locations within the candidate jammer region, and the method includes the additional step of finding the centroid of the plurality of approximate jammer locations.

4. A method as set forth in claim 1, wherein the associated antenna gain values for the sequence of antenna orientations are calculated using precalculated information stored in a memory and data received at a plurality of antenna elements for each antenna orientation.

5. A method as set forth in claim 4, wherein the precalculated information includes a series of sampling points and a set of values for an associated phase function for each of a plurality of antenna elements corresponding to the series of sampling points.

6. A method as set forth in claim 4, wherein the sets of phase functions values are stored in sequence as an array of values, each value corresponding to one of the series of sampling points, and values for a particular antenna element are retrieved by starting at the value corresponding to a sampling point associated with that antenna element and retrieving the remaining values in sequence.

7. A method as set forth in claim 4, wherein the data received at each antenna element comprises a plurality of beamformer coefficients that vary with frequency, the precalculated information includes a set of frequency dependent complex weights, and calculating the antenna gain values includes applying the frequency dependent complex weights to the received beamformer coefficients to obtain a frequency-independent values for each antenna element.

8. A method as set forth in claim 1, wherein the method further includes:

establishing at least one candidate jammer region around one or more candidate null locations; and

searching each of the established candidate jammer regions via an iterative gradient search.

9. A computer program product for locating signal jammers in a digital beamforming receiver having an antenna with a plurality of associated antenna orientations, comprising:

an estimation routine that calculates an associated antenna gain value for a first of a sequence of the plurality of antenna orientations at each of a series of sample points;

a coarse search routine that evaluates the antenna gain values from the first antenna orientation for null spaces to obtain a set of candidate null locations;

characterized in that the estimation routine and the coarse search routine calculate and evaluate associated antenna gain values for subsequent antenna orientations only at the set of candidate null locations, where a candidate null location is eliminated from the set after any evaluation in which it is not found to be a null space.

10. A computer program product as set forth in claim 9, wherein the computer program product further includes the following:

a regionalization routine that establishes at least one candidate jammer region around one or more candidate null locations remaining after antenna gain values have been evaluated for all antenna orientations; and

a fine search routine that iteratively performs the following sequence of functions until the occurrence of a termination event;

subdividing the candidate jammer region into smaller subregions;

selecting the subregion with the lowest antenna gain by calculating antenna gain values at one or more representative points within the subregions; and

replacing the candidate jammer region with the selected subregion.

11. A method of locating a jammer within a defined region, said method comprising:

iteratively repeating the following steps until the occurrence of a termination event;

subdividing the region into smaller subregions;

selecting the subregion with the lowest antenna gain for an associated antenna by calculating antenna gain values at one or more representative points within the subregions; and

replacing the region with the selected subregion.

12. A method as set forth in claim 11, wherein the region is defined by the location of one or more candidate null locations associated with one or more antenna gain patterns.

13. A method as set forth in claim 12, wherein the candidate null locations are determined by the following process:

calculating an associated antenna gain value for a first of a sequence of antenna orientations at each of a series of sample points;

evaluating the antenna gain values from the first antenna orientation for null spaces to obtain a set of candidate null locations; and

calculating and evaluating associated antenna gain values for subsequent antenna orientations only at the set of candidate jammer locations, where a candidate null location is eliminated from the set after any evaluation in which it is not found to be a null space.

14. A method as set forth in claim 11, wherein the one or more representative points include the centroid of each subregion.

15. A method as set forth in claim 11, wherein each region is divided into four subregions.

16. A computer program product for locating a jammer within a defined region, comprising:

a fine search routine that iteratively performs the following sequence of functions until the occurrence of a termination event;

subdividing the region into smaller subregions;

selecting the subregion with the lowest antenna gain for an associated antenna by calculating antenna gain values at one or more representative points within the subregions; and

replacing the region with the selected subregion.

17. A computer program product as set forth in claim 16, wherein the region is defined by the location of one or more candidate null locations associated with one or more antenna gain patterns, and the candidate null locations are determined by:

an estimation routine that calculates an associated antenna gain value for a first of a sequence of antenna orientations at each of a series of sample points; and

a coarse search routine that evaluates the antenna gain values from the first antenna orientation for null spaces to obtain a set of candidate null locations;

characterized in that the estimation routine and the coarse search routine calculate and evaluate associated antenna gain values for subsequent antenna orientations only at the set of candidate jammer locations, where a candidate null location is eliminated from the set after any evaluation in which it is not found to be a null space.

18. A system for locating signal jammers in a digital beamforming system having an antenna with a plurality of associated antenna orientations, comprising:

a central processing unit that calculates an associated antenna gain value for a first of a sequence of the plurality of antenna orientations at each of a series of sample points and evaluates the antenna gain values from the first antenna orientation for null spaces to obtain a set of candidate null locations; and

a working memory that stores the candidate null locations;

characterized in that the central processing unit calculates and evaluates associated antenna gain values for subsequent antenna orientations only at the set of candidate null locations, and further characterized in that a candidate null location is eliminated from the set after any evaluation in which it is not found to be a null space.

19. A system as set forth in claim 18, wherein the central processing unit establishes at least one candidate jammer region around one or more candidate null locations remaining after antenna gain values have been evaluated for all antenna orientations and iteratively searches each of these candidate jammer regions.

20. A system as set forth in claim 19, wherein the iterative search of a candidate jammer region includes:

iteratively repeating the following steps until the occurrence of a termination event;

subdividing the candidate jammer region into smaller subregions;

selecting the subregion with the lowest. antenna gain by calculating antenna gain values at one or more representative points within the subregions; and

replacing the candidate jammer region with the selected subregion.

21. A system as set forth in claim 20, wherein the candidate jammer region is divided into two subregions.

22. A system as set forth in claim 20, wherein the representative points include one or more of the corners of each subregion.