Methods and systems for detection and location of multiple emitters

• US 7,626,546 B2
• Filed: 09/27/2007
• Issued: 12/01/2009
• Est. Priority Date: 09/27/2007
• Status: Expired due to Fees

• Current Assignee: L-3 Communications Integrated Systems LP (L3Harris Technologies, Inc.)
• Original Assignee: L-3 Communications Integrated Systems LP (L3Harris Technologies, Inc.)
• Inventors: Robertson, Mark A., Parker, John M., Le, Phuong H., Chung, Hyo K., Reid, David L.
• Primary Examiner(s): Issing; Gregory C
• Application Number:
  US11/904,630
• Publication Number:
  US 20090224957A1
• Time in Patent Office: 796 Days
• Field of Search: 342/465
• US Class Current: 342/465
• CPC Class Codes: G01S 5/0009 Transmission of position information to remote stations involving assistance data G01S5/0236
• CPC Class Codes: G01S 5/0244 Accuracy or reliability of position solution or of measurements contributing thereto
• CPC Class Codes: G01S 5/0246 involving frequency difference of arrival or Doppler measurements G01S5/02685 takes precedence
• CPC Class Codes: G01S 5/0249 Determining position using measurements made by a non-stationary device other than the device whose position is being determined
• CPC Class Codes: G01S 5/0268 by deriving positions from different combinations of signals or of estimated positions in a single positioning system
• CPC Class Codes: G01S 5/06 Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements G01S5/12 takes precedence
• CPC Class Codes: G01S 5/12 by co-ordinating position lines of different shape, e.g. hyperbolic, circular, elliptical or radial

Abstract

Systems and methods for detection and geolocation of multiple emitters that are emitting RF signal energy on a common frequency, and that may be implemented to separate, geolocate, and/or determine the number of emitters (e.g., radio users) emitting on a common RF frequency. Real-time signal qualification processing may be employed to continuously monitor and collect incoming receiver tuner data for signal activity and ignore irrelevant noise data. Each set of data blocks from an emitter transmission signal may be defined as an emission cluster, and a set of time difference of arrival (TDOA)/frequency difference of arrival (FDOA) pairs may be computed for each emission cluster with each TDOA/FDOA pair yielding a geolocation result. A statistical qualification method may be used to produce a final geolocation answer from each set of emission cluster geolocation results, and a geolocation error ellipse computed for the final geolocation answer of each emission cluster. The final geolocation answer of each emission cluster may be run through a correlation and fusion algorithm.

Claims

1. A method of locating one or more emitters that are emitting multiple sequential radio frequency (RF) signals on a common frequency, said method comprising:

providing multiple collection nodes, each of said multiple collection nodes being spaced apart from the other of said multiple collection nodes;

collecting said multiple sequential RF signals at each of said multiple collection nodes, each of said sequential emitted RF signals being collected at each of said multiple collection nodes as a cluster of data blocks;

determining a first group of multiple geolocation solutions based on a first one of said multiple clusters of data blocks by measuring at least one of time difference of arrival (TDOA) information or frequency difference of arrival (FDOA) information for said multiple sequential RF signals between at least two of said multiple collection nodes;

determining a second group of multiple geolocation solutions based on a second one of said multiple clusters of data blocks by measuring at least one of TDOA information or FDOA information for said multiple sequential RF signals between at least two of said multiple collection nodes;

determining a first geographic area corresponding to said first one of said multiple cluster of data blocks, said first geographic area including at least a portion of said first group of multiple geolocations, and determining a second geographic area corresponding to said second one of said multiple cluster of data blocks, said second geographic area including at least a portion of said second group of multiple geolocations; and

comparing said first determined geographic area with said second determined geographic area to determine whether or not said first determined geographic area correlates to the same emitter geolocation as said second determined geographic area.

2. The method of claim 1, wherein said first geographic area comprises a first error ellipse;

wherein said second geographic areas comprises a second error ellipse; and

wherein said method further comprises determining said first error ellipse by removing a portion of said group of multiple geolocation solutions using statistical analysis, and determining said second error ellipse by removing a portion of said group of multiple geolocation solutions using statistical analysis.

3. The method of claim 1, further comprising fusing together said first and second determined geographic areas into a single fused geographic area if said first and second determined geographic areas are determined to correlate to the same emitter location, said single fused geographic area including a location of at least one of said emitters.

4. The method of claim 3, further comprising determining if said first determined geographic area correlates to the same emitter geolocation as said second determined geographic area by determining if said first determined geographic area overlaps with said second determined geographic area;

and fusing together said first and second determined geographic areas into a single fused geographic area if said first and second determined geographic areas are determined to overlap with each other.

5. The method of claim 3, wherein said one or more emitters comprise at least two emitters, each of which emits at least one of said sequential RF signals on said common frequency;

and wherein said method further comprises;

collecting a first one of said multiple sequential RF signals emitted by a first one of said emitters at each of said multiple collection nodes as said first one of said multiple clusters of data blocks; and

collecting a second one of said multiple sequential RF signals emitted by a second one of said emitters at each of said multiple collection nodes as said second one of said multiple clusters of data blocks;

wherein said first geographic area includes the geolocation of said first emitter;

wherein said second geographic area includes the geolocation of said second emitter; and

wherein said step of comparing comprises comparing said first determined geographic area with said second determined geographic area to determine that said first determined geographic area does not correlate to the same emitter location as said second determined geographic area.

6. The method of claim 5, further comprising determining that said first determined geographic area does not correlate to the same emitter location as said second determined geographic area by determining that said first determined geographic area does not overlap with said second determined geographic area.

7. The method of claim 3, wherein a first one of said multiple collection nodes comprises a first airborne sensing platform;

wherein a second one of said multiple collection nodes comprises a second airborne sensing platform; and

wherein said method further comprises;

providing a processing node in communication with said first and second ones of said multiple collection nodes;

communicating said multiple clusters of data blocks from each of said first and second collection nodes to said processing node; and

performing the following steps at said processing node;

determining said first group of multiple geolocation solutions, determining said second group of multiple geolocation solutions, determining said first geographic area, determining said second geographic area, comparing said first determined geographic area with said second determined geographic area, and fusing together said first and second determined geographic areas into said single fused geographic area if said first and second determined geographic areas are determined to correlate to the same emitter location.

8. The method of claim 7, wherein said processing node is a processing and control node;

and wherein said method further comprises communicating control information from said processing and control node to each of said multiple collection nodes to control said step of collecting said multiple sequential RF signals at each of said multiple collection nodes.

9. The method of claim 8, wherein said first airborne sensing platform is a first aircraft;

wherein said second airborne sensing platform is a second aircraft; and

wherein said first and second aircraft are moving at different velocities and headings relative to said at least one of said emitters.

10. The method of claim 3, further comprising determining said first group of multiple geolocation solutions based on a first one of said multiple clusters of data blocks by measuring time difference of arrival (TDOA) information and measuring frequency difference of arrival (FDOA) information for said multiple sequential RF signals between at least three of said multiple collection nodes, and determining said second group of multiple geolocation solutions based on a second one of said multiple clusters of data blocks by measuring TDOA information and FDOA information for said multiple sequential RF signals between at least three of said multiple collection nodes.

11. The method of claim 3, wherein said one or more emitters comprise at least two emitters, each of which emits at least one of said sequential RF signals at a different location on said common frequency;

and wherein said method further comprises;

determining a third group of multiple geolocation solutions based on a third one of said multiple clusters of data blocks by measuring time difference of arrival (TDOA) information and measuring frequency difference of arrival (FDOA) information for said multiple sequential RF signals between at least two of said multiple collection nodes;

determining a third geographic area corresponding to said third one of said multiple cluster of data blocks, said third geographic area including at least a portion of said third group of multiple geolocations;

comparing said third determined geographic area with said first and second determined geographic areas to determine whether or not said third determined geographic area correlates to the same emitter geolocation as said second determined geographic area;

fusing together said third determined geographic area with said first determined geographic area into a single fused geographic area when said third determined geographic area is determined to correlate to the same emitter location as said first determined geographic area, said single fused geographic area including a location of said first emitter; and

not fusing said second determined geographic area with said first and second determined geographic areas when said second determined geographic area is determined not to correlate to the same emitter location as said first and second determined geographic areas, said second geographic area including a location of said second emitter.

12. An emitter location system, comprising:

a first collection node configured to receive radio frequency (RF) signals, said first collection node comprising a first sensing platform and signal processing circuitry configured to process RF signals received at said first sensing platform on a time and frequency basis;

a second collection node configured to receive radio frequency (RF) signals, said second collection node comprising a second sensing platform and signal processing circuitry configured to process RF signals received at said second sensing platform on a time and frequency basis; and

a processing node comprising processing circuitry configured to communicate with said signal processing circuitry of said first collection node and said signal processing circuitry of said second collection node;

wherein said processing circuitry of said processing node is configured to;

receive radio frequency (RF) emission cluster data from each of said first and second collection nodes, said RF emission cluster data being produced by one or more RF emitters on a common frequency and comprising at least two different clusters of data blocks,

perform at least one of time difference of arrival (TDOA)/frequency difference of arrival (FDOA), TDOA/TDOA, or FDOA/FDOA processing on said RF emission cluster data to produce at least two geolocation areas that each correspond to a respective different one of said clusters of data blocks, and

compare a first one of said geographic areas with a second and different one of said geographic areas to determine whether or not said first geographic area correlates to the same emitter geolocation as said second determined geographic area.

13. The system of claim 12, wherein said processing circuitry of said processing node is further configured to fuse together said first and second geographic areas into a single fused geographic area if said first and second geographic areas are determined to correlate to the same emitter location, said single fused geographic area including a location of said emitter.

14. The system of claim 13, wherein said processing circuitry of said processing node is further configured to output said single fused geographic area as emitter geolocation information.

15. The system of claim 12, wherein said processing node further comprises control circuitry configured as a master controller for communicating and controlling operation of said first and second collection nodes.

16. The system of claim 12, wherein said first and second sensing platforms are each aircraft;

wherein said first sensing platform comprises a first sensor antenna coupled to said signal processing circuitry of said first sensing platform;

wherein said second sensing platform comprises a second sensor antenna coupled to said signal processing circuitry of said second sensing platform.

17. The system of claim 12, further comprising:

a third collection node configured to receive radio frequency (RF) signals, said third collection node comprising a third sensing platform and signal processing circuitry configured to process RF signals received at said third sensing platform on a time and frequency basis;

wherein said processing node is configured to communicate with said signal processing circuitry of said third collection node; and

wherein said processing circuitry of said processing node is configured to receive said RF emission cluster data from each of said first, second and third collection nodes.

18. The system of claim 12, wherein said processing circuitry of said processing node is configured to:

receive radio frequency (RF) emission cluster data from each of said first and second collection nodes, said RF emission cluster data being produced by at least two emitters on a common frequency and comprising at least three different clusters of data blocks, each of said at least two emitters being at a different location;

perform at least one of TDOA/FDOA, TDOA/TDOA, or FDOA/FDOA processing on said RF emission cluster data to produce at least three geolocation areas that each correspond to a respective different one of said clusters of data blocks;

compare a first one of said geographic areas with second and third different ones of said geographic areas to determine whether or not said first geographic area correlates to the same emitter geolocation as each of said second and third determined geographic areas;

fuse together said first and third geographic areas into a single fused geographic area when said first and third geographic areas are determined to correlate to the same emitter location, said single fused geographic area including a location of a first one of said emitters; and

not fuse together said second geographic area with said first and second geographic areas when said second geographic area is determined not to correlate to the same emitter location as said first and second geographic areas, said second geographic area including a location of said second emitter.

19. A system for processing collected clusters of data blocks to locate one or more emitters that are emitting multiple sequential radio frequency (RF) signals on a common frequency, said system comprising:

one or more processing components configured to receive collected clusters of data blocks from each of multiple collection nodes, each of said collected clusters of datablocks collected from a corresponding sequential emitted RF signal;

wherein said one or more processing components is further configured to;

determine a first group of multiple geolocation solutions based on a first one of said multiple clusters of data blocks by measuring at least one of time difference of arrival (TDOA) information or frequency difference of arrival (FDOA) information for said multiple sequential RF signals between at least two of said multiple collection nodes,

determine a second group of multiple geolocation solutions based on a second one of said multiple clusters of data blocks by measuring at least one of TDOA information or FDOA information for said multiple sequential RF signals between at least two of said multiple collection nodes,

determine a first geographic area corresponding to said first one of said multiple cluster of data blocks, said first geographic area including at least a portion of said first group of multiple geolocations,

determine a second geographic area corresponding to said second one of said multiple cluster of data blocks, said second geographic area including at least a portion of said second group of multiple geolocations,

compare said first determined geographic area with said second determined geographic area to determine whether or not said first determined geographic area correlates to the same emitter geolocation as said second determined geographic area,

fuse together said first and second determined geographic areas into a single fused geographic area if said first and second determined geographic areas are determined to correlate to the same emitter location, said single fused geographic area including a location of at least one of said emitters, and

output emitter geolocation information based on said single fused geographic area.

20. The system of claim 19, wherein said first geographic area comprises a first error ellipse;

wherein said second geographic areas comprises a second error ellipse; and

wherein said one or more processing components are further configured to;

determine said first error ellipse by removing a portion of said group of multiple geolocation solutions using statistical analysis;

determine said second error ellipse by removing a portion of said group of multiple geolocation solutions using statistical analysis; and

fuse together said first and second error ellipses into a single statistically refined fused geographic location if said first and second determined error ellipses are determined to correlate to the same emitter location.

21. The system of claim 19, wherein said one or more emitters comprise at least two emitters, each of which emits at least one of said sequential RF signals on said common frequency;

a first one of said multiple sequential RF signals emitted by a first one of said emitters is collected at each of said multiple collection nodes as said first one of said multiple clusters of data blocks;

wherein a second one of said multiple sequential RF signals emitted by a second one of said emitters at each of said multiple collection nodes as said second one of said multiple clusters of data blocks;

wherein said first geographic area includes the geolocation of said first emitter, and said second geographic area includes the geolocation of said second emitter; and

wherein said one or more processing components are further configured to compare said first determined geographic area with said second determined geographic area to determine that said first determined geographic area does not correlate to the same emitter location as said second determined geographic area.

22. The system of claim 19, further comprising multiple collection nodes, each of said multiple collection nodes being configured to collect said multiple sequential RF signals as a cluster of data blocks;

wherein a first one of said multiple collection nodes comprises a first aircraft configured as a sensing platform;

wherein a second one of said multiple collection nodes comprises a second aircraft configured as a sensing platform;

wherein said one or more processing components comprises a processing node configured to communicate with said first and second ones of said multiple collection nodes;

wherein each of said first and second ones of said multiple collection nodes are configured to communicate said multiple clusters of data blocks to said processing node; and

wherein said processing node is configured to perform the following steps;

determining said first group of multiple geolocation solutions, determining said second group of multiple geolocation solutions, determining said first geographic area, determining said second geographic area, comparing said first determined geographic area with said second determined geographic area, and fusing together said first and second determined geographic areas into said single fused geographic area if said first and second determined geographic areas are determined to correlate to the same emitter location.

23. The system of claim 19, wherein said one or more processing components comprises a processing and control node configured to communicate control information to each of said multiple collection nodes to control collection of said multiple sequential RF signals at each of said multiple collection nodes.

24. The system of claim 19, wherein said one or more processing components if further configured to determine said first group of multiple geolocation solutions based on a first one of said multiple clusters of data blocks by measuring time difference of arrival (TDOA) information and measuring frequency difference of arrival (FDOA) information for said multiple sequential RF signals between at least three of said multiple collection nodes, and determining said second group of multiple geolocation solutions based on a second one of said multiple clusters of data blocks by measuring TDOA information and FDOA information for said multiple sequential RF signals between at least three of said multiple collection nodes.

25. The system of claim 19, wherein said one or more emitters comprise at least two emitters, each of which emits at least one of said sequential RF signals at a different location on said common frequency;

and wherein said one or more processing components is further configured to;

determine a third group of multiple geolocation solutions based on a third one of said multiple clusters of data blocks by measuring time difference of arrival (TDOA) information and measuring frequency difference of arrival (FDOA) information for said multiple sequential RF signals between at least two of said multiple collection nodes;

determine a third geographic area corresponding to said third one of said multiple cluster of data blocks, said third geographic area including at least a portion of said third group of multiple geolocations;

compare said third determined geographic area with said first and second determined geographic areas to determine whether or not said third determined geographic area correlates to the same emitter geolocation as said second determined geographic area;

fuse together said third determined geographic area with said first determined geographic area into a single fused geographic area when said third determined geographic area is determined to correlate to the same emitter location as said first determined geographic area, said single fused geographic area including a location of said first emitter; and

not fuse said second determined geographic area with said first and second determined geographic areas when said second determined geographic area is determined not to correlate to the same emitter location as said first and second determined geographic areas, said second geographic area including a location of said second emitter.