Cooperative systems and methods for TDOA-based emitter location

• US 8,866,672 B2
• Filed: 04/05/2012
• Issued: 10/21/2014
• Est. Priority Date: 04/05/2012
• 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: Stroud, Ken A.
• Primary Examiner(s): LIU, HARRY K
• Application Number:
  US13/440,036
• Publication Number:
  US 20130265198A1
• Time in Patent Office: 929 Days
• Field of Search: 342/378
• US Class Current: 342/378
• CPC Class Codes: G01S 1/04 Details
• CPC Class Codes: G01S 5/0081 Transmission between base stations
• CPC Class Codes: G01S 5/02216 Timing or synchronisation of the receivers
• 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

Abstract

Systems and methods that may be implemented to determine the location of an emitter of electromagnetic radiation having an unknown location, using a cooperative TDOA-based location methodology. The cooperative TDOA-based location methodology (e.g., such as TDOA/TDOA, TDOA/FDOA, etc.) may be implemented using at least one cooperative transmitter that transmits a cooperative electromagnetic (EM) signal from a known location that is received at multiple different EM sensing platforms that are also each of known location. The known geolocation of the cooperative transmitter may be used to resolve the signal arrival timing relationships between the different sensing platforms that is utilized to determine the location of another EM transmitter of unknown location.

Claims

1. A method of determining a time difference of arrival (TDOA) information for an electromagnetic (EM) signal of interest that is transmitted in an EM emissions environment, comprising:

providing multiple EM sensing platforms within the EM emissions environment, the EM emissions environment including the EM signal of interest, and the EM signal of interest having a center frequency and bandwidth;

transmitting a cooperative EM signal from a source of known location simultaneously with the transmission of the EM signal of interest;

simultaneously capturing each of the EM signal of interest and the cooperative EM signal at each of the multiple EM sensing platforms while the sensing platforms are positioned at different geolocations from each other;

deriving a common clock for EM data captured at each given one of the EM sensing platforms based on one or more signal timing characteristics of the EM cooperative signal at the given EM sensing platform and based on the known location of the source of the EM cooperative signal and the known location of the given EM sensing platform at the same time the EM data is captured at each given one of the multiple EM sensing platforms; and

determining the time difference of arrival (TDOA) information for the EM signal of interest between at least two of the multiple EM sensing platforms based on the common clock derived based on the one or more signal timing characteristics of the EM cooperative signal at each given one of the EM sensing platforms.

2. The method of claim 1, further comprising:

detecting the EM signal of interest;

determining one or more frequency characteristics of the detected signal of interest;

transmitting the cooperative EM signal from the source of known location simultaneously with the transmission of the EM signal of interest such that the cooperative EM signal is based at least in part on the determined frequency characteristics of the detected signal of interest so that it has a center frequency that is placed at a selected distance from the center frequency of the EM signal of interest and such that the cooperative EM signal has a bandwidth that does not overlap the bandwidth of the EM signal of interest; and

simultaneously capturing each of the EM signal of interest and the cooperative EM signal at each of the EM sensing platforms in a same collection frequency window.

3. The method of claim 2, further comprising transmitting the cooperative EM signal from the source of known location simultaneously with the transmission of the EM signal of interest such that the cooperative EM signal has a center frequency that is placed at a frequency position relative to the center frequency of the EM signal of interest that is positioned outside the collection frequency window but that folds with analog to digital sampling into a closer relationship with the EM signal of interest such that the folded EM signal of interest is within the collection frequency window.

4. The method of claim 3, where the frequency position of the center frequency of the cooperative EM signal is a harmonic of the EM signal of interest.

5. The method of claim 2, where each of the EM sensing platforms comprises an antenna coupled to receiver circuitry;

and where the method further comprises simultaneously capturing each of the EM signal of interest and the cooperative EM signal at each given one of the EM sensing platforms in the same collection frequency window using the same antenna and the same receiver circuitry of the given EM sensing platform.

6. The method of claim 5, where each of the EM sensing platforms further comprises signal processing circuitry coupled to the receiver circuitry;

and where the method further comprises;

providing digital signal data of the captured collection frequency window from the receiver circuitry to the signal processing circuitry, the signal data comprising sampled data from the EM signal of interest together with sampled data from the cooperative EM signal; and

using the signal processing circuitry to process the digital signal data from the EM signal of interest and the digital signal data from the cooperative EM signal on at least one of a time basis, a frequency basis, or a combination thereof.

7. The method of claim 1, where an emitter of the EM signal of interest has an unknown geolocation;

and where the method further comprises using TDOA-based geolocation methodology to determine the geolocation of the emitter of the EM signal of interest based at least in part on the determined TDOA information for the EM signal of interest between at least two of the multiple EM sensing platforms.

8. The method of claim 1, wherein at least one of the EM sensing platforms is moving relative to an emitter of the EM signal of interest.

9. The method of claim 1, wherein the one or more signal timing characteristics comprises at least one of time of arrival of the cooperative EM signal at the given EM sensing platform, or time of receipt of at least one signature within the cooperative EM signal at the given EM sensing platform.

10. The method of claim 1, further comprising:

transmitting the cooperative EM signal from the source of known location simultaneously with the transmission of the EM signal of interest such that the cooperative EM signal has a center frequency that is placed at a distance from the center frequency of the EM signal of interest and such that the cooperative EM signal has a bandwidth that does not overlap the bandwidth of the EM signal of interest; and

simultaneously capturing each of the EM signal of interest and the cooperative EM signal at each of the EM sensing platforms in different collection frequency windows.

11. The method of claim 1, where at least a given one of the multiple EM sensing platforms comprises transceiver or transmitter circuitry coupled between signal processing circuitry and a communication antenna;

and where the method further comprises;

using the transceiver or transmitter circuitry to transmit at least one of processed emitter signal information or control signals from the signal processing circuitry via the communication antenna to at least one other of the multiple EM sensing platforms;

determining the geolocation of the given one of the multiple EM sensing platforms; and

using the transceiver or transmitter circuitry to transmit the cooperative EM signal from the given one of the multiple EM sensing platforms via the communication antenna simultaneously with the transmission of the EM signal of interest, the geolocation of the given one of the multiple EM sensing platforms being determined and known during transmission of the cooperative EM signal.

12. The method of claim 1, further comprising:

providing at least of the multiple EM sensing platforms as a pre-existing EM sensing platform that includes transceiver or transmitter circuitry coupled between signal processing circuitry and a communication antenna, the transceiver or transmitter circuitry being configured to transmit at least one of processed emitter signal information or control signals from the signal processing circuitry via the communication antenna to at least one other of the multiple EM sensing platforms; and

modifying the pre-existing EM sensing platform to be a modified EM sensing platform by adding cooperative transmitter and processing control circuitry coupled to the transceiver or transmitter circuitry; and

using the cooperative transmitter and processing control circuitry to cause transmission of the cooperative EM signal from the modified EM sensing platform via the communication antenna.

13. A system to determine a time difference of arrival (TDOA) information for an electromagnetic (EM) signal of interest that is transmitted in an EM emissions environment, comprising:

multiple EM sensing platforms configured to simultaneously receive EM signals of interest in the EM emissions environment while the EM sensing platforms are positioned at different known geolocations from each other;

at least one cooperative EM signal transmission platform comprising circuitry configured to transmit a cooperative EM signal from the cooperative EM signal transmission platform simultaneously with the transmission of the EM signal of interest while the cooperative EM signal transmission platform has a known geolocation; and

TDOA-based processing and control circuitry in signal communication with the multiple EM sensing platforms and the cooperative EM signal transmission platform, the TDOA-based processing and control circuitry being configured to;

derive a common timing relationship for EM data captured at each given one of the EM sensing platforms based on one or more signal timing characteristics of the EM cooperative signal at the given EM sensing platform and based on the known location of the source of the EM cooperative signal and the known location of the given EM sensing platform at the same time the EM data is captured at each given one of the multiple EM sensing platforms, and

determine the time difference of arrival (TDOA) information for the EM signal of interest between at least two of the multiple EM sensing platforms based on the timing relationship derived based on the one or more signal timing characteristics of the EM cooperative signal at each given one of the EM sensing platforms.

14. The system of claim 13, where each given one of the EM sensing platforms comprises signal processing circuitry configured to process EM signals of interest received at the given EM sensing platform on a time basis to produce time-processed EM signal data;

where each of the multiple EM sensing platforms is further configured to receive the cooperative EM signal and use the signal processing circuitry to process the received EM signal on a time basis to produce time-processed cooperative EM signal data; and

where the TDOA-based processing and control circuitry is further configured to receive the time-processed EM signal data and the time-processed cooperative EM signal data from each one of the multiple EM sensing platforms.

15. The system of claim 13, where one of the multiple EM sensing platforms comprises the TDOA-based processing and control circuitry.

16. The system of claim 13, where at least one of the multiple EM sensing platforms is configured as a cooperative EM signal transmission platform.

17. The system of claim 13, where the at least one cooperative EM signal transmission platform is configured to determine one or more frequency characteristics of a signal of interest detected by at least one of the multiple EM sensing platforms or the cooperative EM signal transmission platform;

transmit the cooperative EM signal from the source of known location simultaneously with the transmission of the EM signal of interest such that the cooperative EM signal is based at least in part on the determined frequency characteristics of the detected signal of interest so that it has a center frequency that is placed at a selected distance from the center frequency of the EM signal of interest and such that the cooperative EM signal has a bandwidth that does not overlap the bandwidth of the EM signal of interest; and

simultaneously capture each of the EM signal of interest and the cooperative EM signal at each of the EM sensing platforms in a same collection frequency window.

18. The system of claim 17, where the at least one cooperative EM signal transmission platform is configured to transmit the cooperative EM signal from the source of known location simultaneously with the transmission of the EM signal of interest such that the cooperative EM signal has a center frequency that is placed at a frequency position relative to the center frequency of the EM signal of interest that is positioned outside the collection frequency window but that folds with analog to digital sampling into a closer relationship with the EM signal of interest such that the folded EM signal of interest is within the collection frequency window.

19. The system of claim 18, where the frequency position of the center frequency of the cooperative EM signal is a harmonic of the EM signal of interest.

20. The system of claim 18, where each of the EM sensing platforms comprises an antenna coupled to receiver circuitry;

and where the multiple EM sensing platforms are configured to simultaneously capture each of the EM signal of interest and the cooperative EM signal in the same collection frequency window using the same antenna and the same receiver circuitry of the given EM sensing platform.

21. The system of claim 20, where each of the EM sensing platforms further comprises signal processing circuitry coupled to the receiver circuitry;

and

where the receiver circuitry of each given one of the EM sensing platforms is configured to provide digital signal data of the captured collection frequency window from to the signal processing circuitry of the given one of the EM sensing platforms, the signal data comprising sampled data from the EM signal of interest together with sampled data from the cooperative EM signal; and

where the signal processing circuitry of each given one of the EM sensing platforms is configured to process the digital signal data from the EM signal of interest and the digital signal data from the cooperative EM signal on at least one of a time basis, a frequency basis, or a combination thereof.

22. The system of claim 13, where the TDOA-based processing and control circuitry is further configured to use TDOA-based geolocation methodology to determine the geolocation of the emitter of the EM signal of interest based at least in part on the determined TDOA information for the EM signal of interest between at least two of the multiple EM sensing platforms.

23. The system of claim 13, wherein at least one of the EM sensing platforms is a mobile EM sensing platform configured to move relative to an emitter of the EM signal of interest.

24. The system of claim 13, wherein the one or more signal timing characteristics comprises at least one of time of arrival of the cooperative EM signal at the given EM sensing platform, or time of receipt of at least one signature within the cooperative EM signal at the given EM sensing platform.

25. The system of claim 13, here the at least one cooperative EM signal transmission platform is configured to transmit the cooperative EM signal from known location simultaneously with the transmission of the EM signal of interest such that the cooperative EM signal has a center frequency that is placed at a distance from the center frequency of the EM signal of interest and such that the cooperative EM signal has a bandwidth that does not overlap the bandwidth of the EM signal of interest;

and where the each of the multiple EM sensing platforms is configured to simultaneously capture each of the EM signal of interest and the cooperative EM signal in different collection frequency windows.

26. The system of claim 13, where at least a given one of the multiple EM sensing platforms comprises transceiver or transmitter circuitry coupled between signal processing circuitry and a communication antenna;

where the transceiver or transmitter circuitry is configured to transmit at least one of processed emitter signal information or control signals from the signal processing circuitry via the communication antenna to at least one other of the multiple EM sensing platforms;

where the at least a given one of the multiple EM sensing platforms further comprises location determination circuitry for determining the geolocation of the given one of the multiple EM sensing platforms; and

where the transceiver or transmitter circuitry is further configured to transmit the cooperative EM signal from the given one of the multiple EM sensing platforms via the communication antenna simultaneously with the transmission of the EM signal of interest, the geolocation of the given one of the multiple EM sensing platforms being determined and known by the location circuitry during transmission of the cooperative EM signal.

27. A cooperative EM signal transmission platform, comprising:

a communication antenna;

transceiver or transmitter circuitry coupled to the communications antenna and configured to communicate with one or more EM sensing platforms in an an EM emissions environment;

TDOA-based processing and control circuitry coupled to the transceiver circuitry and being configured to communicate with the multiple EM sensing platforms to receive EM data from each of the multiple EM sensing platforms via the transceiver circuitry and communications antenna, the TDOA-based processing and control circuitry being configured to determine the time difference of arrival (TDOA) information for an EM signal of interest between at least two of the multiple EM sensing platforms based on a common timing relationship derived based on one or more signal timing characteristics of an EM cooperative signal at each given one of the EM sensing platforms; and

cooperative transmitter and processing control circuitry coupled to the transceiver or transmitter circuitry configured to cause transmission of the cooperative EM signal from the cooperative EM signal transmission platform via the transceiver or transmitter and the communication antenna.

28. A method of operating a cooperative EM signal transmission platform in an EM emissions environment, comprising:

providing a cooperative EM signal transmission platform that includes;

a communication antenna,

transceiver or transmitter circuitry coupled to the communications antenna,

TDOA-based processing and control circuitry coupled to the transceiver or transmitter circuitry, and

cooperative transmitter and processing control circuitry coupled to the transceiver or transmitter circuitry;

using the TDOA-based processing and control circuitry to communicate with multiple other EM sensing platforms in the EM emissions environment to receive EM data from each of the multiple EM sensing platforms via the transceiver circuitry and communications antenna;

using the TDOA-based processing and control circuitry to determine the time difference of arrival (TDOA) information for an EM signal of interest between at least two of the multiple EM sensing platforms based on a common clock derived based on one or more signal timing characteristics of an EM cooperative signal at each given one of the EM sensing platforms; and

using the cooperative transmitter and processing control circuitry to cause transmission of the cooperative EM signal from the cooperative EM signal transmission platform via the transceiver or transmitter and the communication antenna.