Systems And Methods For Direct Emitter Geolocation

• US 20140327571A1
• Filed: 05/31/2013
• Published: 11/06/2014
• Est. Priority Date: 05/02/2013
• Status: Active Grant

• Current Assignee: L3harris Technologies Integrated Systems LP (L3Harris Technologies, Inc.)
• Original Assignee: L-3 Communications Integrated Systems LP (L3Harris Technologies, Inc.)
• Inventors: Westcott, Bryan L., Stanners, Steven P.
• Granted Patent: US 9,377,520 B2
• Time in Patent Office: Days
• US Class Current: 342/351
• CPC Class Codes: G01S 2205/03 Airborne
• 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

Abstract

Systems and methods are disclosed for locating signal wave (SW) emitter/s using at least one moving signal collection platform. The disclosed systems and methods may be employed in one embodiment to estimate the signal energy transmitted from a grid of locations (such as a map) using collected IQ data (or other raw data representation such as IQ data covariance matrix), and without requiring computation of any intermediate geolocation-observable measurements (such as angle-of-arrival, direction-of-arrival, etc.). In a further embodiment, the disclosed systems and methods may be implemented in a blind manner (i.e., transmitted emitter signal/s are unknown and processed blindly) to geolocate SW emitters using a single SW signal collection platform (e.g., at relatively large standoff distances in some implementations) without relying on a known signal modulation or operation of multiple simultaneous SW signal collection platforms.

Claims

1. A method for locating at least one signal wave (SW) emitter of unknown modulation using a single moving signal collection platform, comprising:

collecting a raw data representation of SW signal emissions within a SW emissions environment only at the single moving collection platform, the raw data representation of SW signal emissions including SW emissions of unknown modulation from the SW emitter, and the raw data representation including data samples having magnitudes that are characteristic of received signal energy of the SW emitter;

estimating the signal energy transmitted within the SW emissions environment from a two or three dimensional grid of locations using the raw data representation collected only at the single moving signal collection platform; and

determining the location of the SW emitter on the two dimensional or three dimensional grid from an estimated signal energy distribution across the two or three dimensional grid without knowledge of the modulation of the SW emissions from the SW emitter and without determining any intermediate geolocation observable measurement.

2. The method of claim 1, where the collected raw data representation of SW signal emissions includes SW emissions from multiple SW emitters of unknown modulation collected only at the single moving signal collection platform;

where the raw data representation includes data samples having magnitudes that are characteristic of received signal energy of each of the SW emitters; and

where the method further comprises;

decomposing and separating the received signal energy of the raw data representation into the signal energy contributions for each of the multiple SW emitters at a single location on the grid; and

determining a location of each of the multiple SW emitters on the grid based at least in part on the received signal energy contribution of each SW emitter without knowledge of the modulation of the SW emissions from any of the multiple SW emitters and without determining any intermediate geolocation observable measurements;

where each SW emitter remains stationary on the grid at the same time that the signal collection platform moves relative to the SW emitter and collects the raw data representation of SW signal emissions.

3. The method of claim 2, further comprising decomposing and separating the received signal energy of the raw data representation into the signal energy contributions for each of the multiple SW emitters using at least one of single pass sparse reconstruction that jointly and simultaneously estimates the contribution of each emitter;

iterative serial nulling or cancellation that separately and sequentially estimates the contribution of each emitter;

or a combination thereof.

4. The method of claim 2, further comprising:

using an interferometer array on the single moving collection platform to collect the raw data representation of SW signal emissions within the SW emissions environment, the interferometer array comprising multiple spaced antenna elements, and the number of multiple SW emitters on the grid exceeding a number of elements of the interferometer array; and

using overloaded array processing to determine a location of each of the multiple SW emitters on the grid, the number of determined emitter locations exceeding the number of antenna elements of the interferometer.

5. The method of claim 4, where the overloaded array processing comprises using iterative serial nulling to process the collected raw data representation of SW signal emissions including the SW emissions from the multiple SW emitters by:

(a) identifying the geolocation of the strongest emitter signal on or between grid points of the quantized grid that is currently present in the collected raw data representation;

(b) then removing the signal energy contribution of the previously identified strongest emitter signal energy to produce a new collected raw data representation that does not include the signal energy of previously identified strongest emitter signal; and

(c) then repeating steps (a) and (b) to identify the geolocation of a greater number of emitter signals than the number of antenna elements in the interferometer array.

6. The method of claim 1, further comprising:

estimating the signal energy transmitted from a given moving SW emitter at multiple locations on the two or three dimensional grid of locations at respective different times using the collected raw data representation; and

determining the multiple locations of the SW emitter at the respective different times on the two dimensional or three dimensional grid from the estimated signal energy distribution across the two or three dimensional grid as it changes over time.

7. The method of claim 1, further comprising using an interferometer array on the single moving collection platform to collect the raw data representation of SW signal emissions within the SW emissions environment, the interferometer array comprising multiple spaced antenna elements.

8. The method of claim 1, further comprising determining the location of the SW emitter on a two-dimensional grid which represents a quantized set of potential emitter locations that span a local physical area having grid points that each correspond to a unique latitude and longitude pair;

and where each grid point also corresponds to a single value of altitude above the earth.

9. A signal wave (SW) emitter location system, comprising a single mobile signal collection platform including at least one antenna element coupled to signal processing circuitry and configured to receive SW signal emissions within a SW emissions environment as the signal collection platform is moving;

where the signal processing circuitry is configured to;

use the at least one antenna element to collect a raw data representation of the SW signal emissions within the SW emissions environment as the signal collection platform is moving, the raw data representation of SW signal emissions including SW emissions from at least one SW emitter of unknown modulation, and the raw data representation including data samples having magnitudes that are characteristic of received signal energy of the SW emitter;

estimate the signal energy transmitted within the SW emissions environment from a two or three dimensional grid of locations using the raw data representation collected only at the single moving signal collection platform; and

determine the location of the SW emitter on the two dimensional or three dimensional grid from an estimated signal energy distribution across the two or three dimensional grid without knowledge of the modulation of the SW emissions from the SW emitter and without determining any intermediate geolocation observable measurement.

10. The system of claim 9, where the collected raw data representation of SW signal emissions includes SW emissions from multiple SW emitters of unknown modulation collected only at the single moving signal collection platform;

where the raw data representation includes data samples having magnitudes that are characteristic of received signal energy of each of the SW emitters; and

where the signal processing circuitry is further configured to;

decompose and separate the received signal energy of the raw data representation into the signal energy contributions for each of the multiple SW emitters at a single location on the grid; and

determine a location of each of the multiple SW emitters on the grid based at least in part on the received signal energy contribution of each SW emitter without knowledge of the modulation of the SW emissions from any of the multiple SW emitters and without determining any intermediate geolocation observable measurements;

where each SW emitter remains stationary on the grid at the same time that the signal collection platform moves relative to the SW emitter and collects the raw data representation of SW signal emissions.

11. The system of claim 10, where the signal processing circuitry is further configured to decompose and separate the received signal energy of the raw data representation into the signal energy contributions for each of the multiple SW emitters using at least one of single pass sparse reconstruction that jointly and simultaneously estimates the contribution of each emitter;

iterative serial nulling or cancellation that separately and sequentially estimates the contribution of each emitter, or a combination thereof.

12. The system of claim 10, where the at least one antenna array comprises an interferometer array comprising multiple spaced antenna elements;

and where the signal processing circuitry is further configured to;

use the interferometer array on the single moving collection platform to collect the raw data representation of SW signal emissions within the SW emissions environment, the interferometer array comprising multiple spaced antenna elements, and the number of multiple SW emitters on the grid exceeding a number of elements of the interferometer array; and

use overloaded array processing to determine a location of each of the multiple SW emitters on the grid, the number of determined emitter locations exceeding the number of antenna elements of the interferometer

13. The system of claim 12, where the signal processing circuitry is further configured to use iterative serial nulling to process the collected raw data representation of SW signal emissions including the SW emissions from the multiple SW emitters by:

(a) identifying the geolocation of the strongest emitter signal on or between grid points of the quantized grid that is currently present in the collected raw data representation;

(b) then removing the signal energy contribution of the previously identified strongest emitter signal energy to produce a new collected raw data representation that does not include the signal energy of previously identified strongest emitter signal; and

(c) then repeating steps (a) and (b) to identify the geolocation of a greater number of emitter signals than the number of antenna elements in the interferometer array.

14. The system of claim 9, where the signal processing circuitry is further configured to:

estimate the signal energy transmitted from a given moving SW emitter at multiple locations on the two or three dimensional grid of locations at respective different times using the collected raw data representation; and

determine the multiple locations of the SW emitter at the respective different times on the two dimensional or three dimensional grid from the estimated signal energy distribution across the two or three dimensional grid as it changes over time.

15. The system of claim 9, where the at least one antenna array comprises an interferometer array comprising multiple spaced antenna elements;

and where the signal processing circuitry is further configured to use the interferometer array on the single moving collection platform to collect the raw data representation of SW signal emissions within the SW emissions environment.

16. The system of claim 9, where the signal processing circuitry is further configured to determine the location of the SW emitter on a two-dimensional grid which represents a quantized set of potential emitter locations that span a local physical area having grid points that each correspond to a unique latitude and longitude pair;

and where each grid point also corresponds to a single value of altitude above the earth.

17. A method for locating at least one signal wave (SW) emitter using at least a single moving signal collection platform, comprising:

collecting a raw data representation of SW signal emissions within a SW emissions environment at the single moving collection platform, the raw data representation of SW signal emissions including SW emissions from the SW emitter, and the raw data representation including data samples having magnitudes that are characteristic of received signal energy of the SW emitter;

estimating the signal energy transmitted within the SW emissions environment from a two or three dimensional grid of locations using the collected raw data representation; and

determining the location of the SW emitter on the two dimensional or three dimensional grid from an estimated signal energy distribution across the two or three dimensional grid;

where the collected raw data representation of SW signal emissions includes SW emissions from multiple SW emitters;

where the raw data representation includes data samples having magnitudes that are characteristic of received signal energy of each of the SW emitters; and

where the method further comprises;

decomposing and separating the received signal energy of the raw data representation into the signal energy contributions for each of the multiple SW emitters at a single location on the grid, and

determining a location of each of the multiple SW emitters on the grid based at least in part on the received signal energy contribution of each SW emitter,

where each SW emitter remains stationary on the grid at the same time that the signal collection platform moves relative to the SW emitter and collects the raw data representation of SW signal emissions; and

where the method further comprises decomposing and separating the received signal energy of the raw data representation into the signal energy contributions for each of the multiple SW emitters using at least one of single pass sparse reconstruction that jointly and simultaneously estimates the contribution of each emitter;

iterative serial nulling or cancellation that separately and sequentially estimates the contribution of each emitter;

or

a combination thereof.

18. The method of claim 17, where the at least single moving signal collection platform comprises multiple moving signal collection platforms;

and where the method further comprises collecting the raw data representation of SW signal emissions within the SW emissions environment at the multiple moving collection platforms.

19. The method of claim 17, where the at least single moving signal collection platform comprises only a signal moving signal collection platform;

and where the method further comprises collecting the raw data representation of SW signal emissions within the SW emissions environment only at the single moving collection platform.

20. The method of claim 17, where only partial modulation information is known for at least one of the SW emitters without full knowledge of the signal modulation of the at least one SW emitter, the partial information comprising timing structure of the at least one SW emitter, frequency structure of the at least one SW emitter, or a combination thereof;

and where the step of determining the location of the at least one SW emitter on the grid further comprises using the known partial modulation information of the SW emitter to improve the accuracy of the determined geolocation of the SW emitter without consideration of a known reference signal.

21. The method of claim 17, where no signal modulation information is known for at least one of the SW emitters;

and where the step of determining the location of the at least one SW emitter on the grid further is performed without any knowledge of the signal modulation of the at least one of the SW emitters.

22. A SW emitter location system, comprising at least one mobile signal collection platform including at least one antenna element coupled to signal processing circuitry and configured to receive SW signal emissions within a SW emissions environment as the signal collection platform is moving;

where the signal processing circuitry is configured to;

use the at least one antenna element to collect a raw data representation of the SW signal emissions within the SW emissions environment as the signal collection platform is moving, the raw data representation of SW signal emissions including SW emissions from the SW emitter, and the raw data representation including data samples having magnitudes that are characteristic of received signal energy of the SW emitter;

estimate the signal energy transmitted within the SW emissions environment from a two or three dimensional grid of locations using the collected raw data representation; and

determine the location of the SW emitter on the two dimensional or three dimensional grid from an estimated signal energy distribution across the two or three dimensional grid;

where the collected raw data representation of SW signal emissions includes SW emissions from multiple SW emitters;

where the raw data representation includes data samples having magnitudes that are characteristic of received signal energy of each of the SW emitters; and

where the signal processing circuitry is further configured to;

decompose and separate the received signal energy of the raw data representation into the signal energy contributions for each of the multiple SW emitters at a single location on the grid, and

determine a location of each of the multiple SW emitters on the grid based at least in part on the received signal energy contribution of each SW emitter,

where each SW emitter remains stationary on the grid at the same time that the signal collection platform moves relative to the SW emitter and collects the raw data representation of SW signal emissions; and

where the signal processing circuitry is further configured to decompose and separate the received signal energy of the raw data representation into the signal energy contributions for each of the multiple SW emitters using at least one of single pass sparse reconstruction that jointly and simultaneously estimates the contribution of each emitter;

iterative serial nulling or cancellation that separately and sequentially estimates the contribution of each emitter, or a combination thereof.

23. The system of claim 22, where the at least one mobile signal collection platform includes multiple mobile signal collection platforms that each includes at least one antenna element;

and where the signal processing circuitry is configured to use the at least one antenna element on each of the multiple signal collection platforms to collect the raw data representation of the SW signal emissions within the SW emissions environment as the multiple signal collection platforms are moving.

24. The system of claim 22, where the at least one mobile signal collection platform includes only a single mobile signal collection platform that includes at least one antenna element;

and where the signal processing circuitry is configured to use the at least one antenna element on only the single signal collection platform to collect the raw data representation of the SW signal emissions within the SW emissions environment as the single signal collection platform is moving.

25. The system of claim 22, where the signal processing circuitry is further configured to:

determine the location of at least one SW emitter on the grid for which only partial modulation information is known, the partial information comprising timing structure of the at least one SW emitter, frequency structure of the at least one SW emitter, or a combination thereof; and

use the known partial modulation information of the SW emitter to improve the accuracy of the determined geolocation of the SW emitter without consideration of a known reference signal.

26. The system of claim 22, where the signal processing circuitry is further configured to determine the location of at least one SW emitter on the grid without any knowledge of signal modulation information for the at least one SW emitter