System and Method for Geolocation of Multiple Unknown Radio Frequency Signal Sources

• US 20120293371A1
• Filed: 05/19/2011
• Published: 11/22/2012
• Est. Priority Date: 05/19/2011
• Status: Active Grant

• Current Assignee: Harris Global Communications, Inc. (L3Harris Technologies, Inc.)
• Original Assignee: ITT Manufacturing Enterprises, Inc. (ITT, Inc.)
• Inventors: Lu, Ning Hsing
• Granted Patent: US 8,878,725 B2
• Time in Patent Office: Days
• US Class Current: 342/387
• CPC Class Codes: G01S 1/04 Details
• CPC Class Codes: G01S 2205/03 Airborne
• CPC Class Codes: G01S 5/0263 by combining or switching between positions derived from two or more separate positioning systems
• 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 5/14 Determining absolute distances from a plurality of spaced points of known location

Abstract

According to an embodiment of the present invention, geolocations of multiple unknown radio frequency (RF) signal sources are determined using three-dimensional (3-D) geolocation techniques. The three-dimensional (3-D) geolocation techniques obtain reliable geolocation estimates of radio frequency (RF) emitters based on energy or received signal strength (RSS) of emitter transmitted signals and based on their time differences of arrival (TDOAs) at various sensor locations. The energy based geolocations and the time difference of arrival (TDOA) geolocations are combined to determine an overall set of geolocations for multiple unknown radio frequency (RF) signal sources. The geolocation information is used to track and monitor the locations of the multiple emitters.

Claims

1. A system for locating an emitter within an area comprising:

a receiver to receive signals transmitted by said emitter at a plurality of different locations within said area;

a sampling module to digitize said received signals to produce digital signals;

a memory to store said digital signals;

a processor to process said digital signals to locate said emitter within said area, wherein said processor includes;

a blind source separation module to separate said digital signals into narrowband and broadband components;

an energy-based geolocation module to process said narrowband components and determine a first three-dimensional location of said emitter within said area based on energy measures of said narrowband components, wherein said energy measures are proportional to distances between said emitter and each of said plurality of locations;

a time difference of arrival based geolocation module to process said broadband components and determine a second three-dimensional location of said emitter within said area based on time differences of reception times of said received signals at each of said plurality of locations, wherein said time differences are proportional to range differences between said plurality of locations and said emitter; and

a combiner module to combine said first three-dimensional location with said second three-dimensional location to determine a combined three-dimensional location of said emitter within said area.

2. The system of claim 1, wherein said a blind source separation module includes:

a preprocessing module to decorrelate said digital signals;

a signal separation module to separate said decorrelated signals; and

a post processing module to generate said narrowband components and said broadband components from said separated signals.

3. The system of claim 2, wherein said preprocessing module generates a covariance matrix from said digital signals and decorrelates said digital signals by applying a transform to said covariance matrix such that a new set of data are generated that approximate white noise.

4. The system of claim 2, wherein said preprocessing module decorrelates said digital signals performing principle component analysis.

5. The system of claim 2, wherein said signal separation module separates said decorrelated signals using independent component analysis.

6. The system of claim 2, wherein said post-processing module generates said narrowband components and said broadband components using signal deflation and reconstruction on said separated signals.

7. The system of claim 1, wherein said energy-based geolocation module includes:

a signal to noise ratio enhancement and energy estimation module to enhance a signal to noise ratio of said narrowband components and estimate an energy level for said enhanced narrowband components;

a system formulation module to manage said narrowband components and load said estimated energy levels into said memory; and

a location module to determine said first three-dimensional location of said emitter based on said estimated energy levels of said narrowband components.

8. The system of claim 7, wherein said signal to noise ratio enhancement and energy estimation module enhances said signal to noise ratio of said narrowband components using iterative power subtraction and filtering.

9. The system of claim 7, wherein said location module determines said first three-dimensional location by solving a set of simultaneous equations relating to said distances, wherein said set of simultaneous equations include unknown variables representing coordinates of said first three-dimensional location of said emitter within said area.

10. The system of claim 1, wherein said time difference of arrival based geolocation module includes:

a time difference of arrival estimation module to estimate time differences of arrival for said broadband components between each of said plurality of locations;

a system formulation module to manage and load said time difference of arrival estimates into said memory; and

a location module to determine said second three-dimensional location of said emitter based on said estimated time differences of arrival.

11. The system of claim 10, wherein said location module determines said second three-dimensional location by solving a set of simultaneous equations relating to said range differences, wherein said set of simultaneous equations include unknown variables representing coordinates of said second three-dimensional location of said emitter within said area.

12. The system of claim 1, wherein said combiner module combines said first three-dimensional location with said second three-dimensional location to determine said combined three-dimensional location of said emitter based on one or more of signal non-Gaussianity, narrowband signal features, broadband signal features, and root means square signal errors.

13. The system of claim 1, wherein said combiner module tracks movement of said emitter.

14. The system of claim 1, further comprising:

a transceiver to transmit and receive digitized radio frequency data.

15. A method for locating an emitter within an area comprising:

(a) receiving signals transmitted by said emitter via a receiver at a plurality of different locations within said area;

(b) sampling said received signals to produce digital signals;

(c) storing said digital signals in memory;

(d) processing said digital signals, via a processor, wherein step (d) further includes;

(d.1) separating said digital signals into narrowband and broadband components;

(d.2) determining a first three-dimensional location of said emitter within said area based on energy measures of said narrowband components, wherein said energy measures are proportional to distances between said emitter and each of said plurality of locations;

(d.3) determining a second three-dimensional location of said emitter within said area based on time differences of reception times of said received signals at each of said plurality of locations, wherein said time differences are proportional to range differences between said plurality of locations and said emitter; and

(d.4) combining said first three-dimensional location with second three-dimensional location to determine a combined three-dimensional location of said emitter within said area.

16. The method of claim 15, wherein step (d.1) further includes:

(d.1.1) decorrelating said digital signals;

(d.1.2) separating said decorrelated signals; and

(d.1.3) generating said narrowband components and said broadband components from said separated signals.

17. The method of claim 16, wherein step (d.1.1) comprises decorrelating said digital signals by generating a covariance matrix from said digital data and decorrelating said digital signals by applying a transform to said covariance matrix such that a new set of data are generated that approximate white noise.

18. The method of claim 16, wherein step (d.1.1) comprises decorrelating said digital signals by performing principle component analysis on said digital signals.

19. The method of claim 16, wherein step (d.1.2) comprises separating said decorrelated signals by performing independent component analysis on said decorrelated signals.

20. The method of claim 16, wherein step (d.1.3) comprises generating said narrowband components and said broadband components by performing signal deflation and reconstruction on said separated signals.

21. The method of claim 15, wherein step (d.2) further includes:

(d.2.1) enhancing a signal to noise ratio of said narrowband components;

(d.2.2) estimating an energy level for said enhanced narrowband components;

(d.2.3) managing and loading said estimated energy levels into said memory; and

(d.2.4) determining said first three-dimensional location of said emitter based on said estimated energy levels of said narrowband components.

22. The method of claim 21, wherein step (d.2.) comprises enhancing said signal to noise ratio of said narrowband components using iterative power subtraction and filtering.

23. The method of claim 21, wherein step (d.2.4) comprises determining said first three-dimensional location by solving a set of simultaneous equations relating to said distances, wherein said set of simultaneous equations include unknown variables representing coordinates of said first three-dimensional location of said emitter within said area.

24. The method of claim 15, wherein step (d.3) further includes:

(d.3.1) estimating time differences of arrival for said broadband components between each of said plurality of locations;

(d.3.2) managing and loading said time difference of arrival estimates into said memory; and

(d.3.3) determining said second three-dimensional location of said emitter based on said estimated time differences of arrival.

25. The method of claim 24, wherein step (d.3.3) comprises determining said second three-dimensional location by solving a set of simultaneous equations relating to said range differences, wherein said set of simultaneous equations include unknown variables representing coordinates of said second three-dimensional location of said emitter within said area.

26. The method of claim 15, wherein step (d.4) comprises combining said first three-dimensional location with said second three-dimensional location to determine said combined three-dimensional location of said emitter based on one or more of narrowband signal and broadband signal non-Gaussianity, narrowband signal features, broadband signal features, and root means square signal errors.

27. The method of claim 15, further including tracking movement of said emitter.

28. The method of claim 15, further including transmitting said digital signals.