Multiplatform TDOA correlation interferometer geolocation

• US 7,453,400 B2
• Filed: 02/02/2007
• Issued: 11/18/2008
• Est. Priority Date: 02/02/2007
• Status: Active Grant

• Current Assignee: BAE Systems Information and Electronic Systems Integration Incorporated (BAE Systems Plc)
• Original Assignee: BAE Systems Information and Electronic Systems Integration Incorporated (BAE Systems Plc)
• Inventors: Struckman, Keith A., Kabel, Allan M.
• Primary Examiner(s): PHAN, DAO LINDA
• Application Number:
  US11/701,679
• Publication Number:
  US 20080186235A1
• Time in Patent Office: 655 Days
• Field of Search: 342/357.06, 342/442, 342/450, 342/463, 342/465, 701/213, 701/215
• US Class Current: 342/465
• CPC Class Codes: G01S 5/02213 Receivers arranged in a network for determining the position of a transmitter
• 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 5/06 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

A radio geolocation system is described in which a plurality of moving platforms such as aircraft concurrently receive a signal from a remote transmitter and the geolocation of the transmitter is determined. At each platform every thirty seconds a plurality of samples of the received signal are taken over a one second period. The samples are digitized and a time and GPS location stamp are added to each sample. The digitized samples with time and location stamps from all platforms are transmitted to a central location and stored in covariance matrices, one matrix per one second sample period. The signal samples in each matrix are processed utilizing a unique algorithm to generate a data set which defines a correlation surface. The data from a plurality of data sets are summed together on a point by point basis and normalized to yield a summation data set which defines a summation correlation surface. The summation correlation surface has a well defined peak that defines the geolocation of the remote transmitter.

Claims

1. A method for locating a remote transmitter from which an electromagnetic signal is being received using an antenna and a receiver mounted on each of a plurality of moving platforms, and indicating the geolocation of the transmitter, the method comprising the steps of:

(a) obtaining a plurality of sets of samples of the electromagnetic signal received with the antenna and receiver on each moving platform, there being one set of samples received at each moving platform for each of a plurality of time periods;

(b) placing a time and location stamp on each of the signal samples obtained in step (a) indicating the time when and the location where each signal sample is taken;

(c) transmitting the signal samples received at each moving platform and having the time and location stamps thereon per step (c) to a central location;

(d) storing at the central location the set of signal samples transmitted in step (c) from each moving platform for each period of time;

(e) processing the stored set of signal samples from all the moving platforms for each period of time to produce an individual data set for each period of time; and

(f) analyzing the data sets produced in step (e) to determine the geolocation of the remote transmitter.

2. The method for locating a remote transmitter of claim 1 further comprising the step of:

(g) summing the plurality of individual data sets produced in step (e) to produce a summation data set that has a distinctive point with a well defined peak value that is higher than the value of other peaks in the summation data set, the well defined peak value indicating the geolocation of the remote transmitter, wherein the summing reducing extraneous peaks in the individual data sets produced in step (e) and enhances the well defined peak in the summation data set; and

wherein step (f) is performed on the summation data set produced in step (g) to locate the well defined peak which yields the geolocation of the remote transmitter.

3. The method for locating a remote transmitter of claim 2 wherein step (f) comprises a hill climbing algorithm such as a conjugate gradient search to locate the well defined peak in the summation data set which indicates the geolocation of the remote transmitter.

4. The method for locating a remote transmitter of claim 3 wherein the central location is separate from any of the plurality of moving platforms.

5. The method for locating a remote transmitter of claim 4 wherein the moving platforms are aircraft.

6. The method for locating a remote transmitter of claim 3 wherein the central location is separate from any of the plurality of moving platforms, and wherein the moving platforms are aircraft.

7. The method for locating a remote transmitter of claim 1 wherein the central location is separate from any of the plurality of moving platforms.

8. The method for locating a remote transmitter of claim 7 wherein the moving platforms are aircraft.

9. The method for locating a remote transmitter of claim 8 further comprising the step of:

(g) summing the plurality of individual data sets produced in step (e) to produce a summation data set that has a distinctive point with a well defined peak value that is higher than the value of other peaks in the summation data set, the well defined peak value indicating the geolocation of the remote transmitter, wherein the summing reducing extraneous peaks in the individual data sets produced in step (e) and enhances the well defined peak in the summation data set; and

wherein step (f) is performed on the summation data set produced in step (g) to locate the well defined peak which yields the geolocation of the remote transmitter.

10. The method for locating a remote transmitter of claim 1 wherein the moving platforms are aircraft.

11. The method for locating a remote transmitter of claim 5 wherein a highly accurate, source of time is used to provide the source of the time stamp placed on each signal samples obtained in step (a) at all of the aircraft, and wherein the global positioning system is used to provide the source of the location stamp placed on each signal samples obtained in step (a) at all of the aircraft.

12. The method for locating a remote transmitter of claim 1 wherein there is more than one antenna and receiver mounted on each moving platforms, and step (a) is repeated for the signals received by each antenna, and further comprising the steps of:

(h) processing the set of signals samples received using each antenna and receiver on a moving platform for each of the plurality of time periods to minimize or remove the effects caused by such things as undesired interfering signals, and thermal background noise; and

(i) generating a single set of cleaned up signal samples for each of the plurality of time periods using the processed sets of signal samples from step (h), the cleaned up signal samples being transmitted to the central location in step (c) after having the time and location stamps placed on each cleaned up signal sample in step (b).

13. A method for locating a remote transmitter from which an electromagnetic signal is being received using an antenna and a receiver mounted on each of a plurality of moving platforms, and indicating the geolocation of the transmitter on the terrain of the earth, the method comprising the steps of:

(a) sampling the electromagnetic signal received at each of the moving platforms to produce a plurality of sets of signal samples that are digitized, there being one set of signal samples for each of a plurality of periods of time at each platform;

(b) adding a time and location stamp on each of the digitized signal samples obtained in step (a) indicating the time when and geolocation where each digitized signal sample is taken on a moving platform;

(c) transmitting each set of digitized signal samples with their time and location stamps from each moving platform to a common location for processing;

(d) storing the sets of digitized signal samples transmitted in step (c) to the common location in a covariance matrix for each of the plurality of periods of time;

(e) processing the sets of digitized signal samples received from all platforms for each of the plurality of periods of time to produce a like plurality of individual data sets;

(f) summing and normalizing all of the individual data sets produced in step (e) to produce a summation data set; and

(g) analyzing the summation set of data produced in step (f) to determine the geolocation of the remote transmitter.

14. The method for locating a remote transmitter of claim 13 wherein the summation data set produced in step (f) has a well defined peak that is higher than any other peaks in the summation data set, the well defined peak indicating the geolocation of the remote transmitter;

and

wherein step (g) is performed on the summation data set produced in step (f) to locate the well defined peak which indicates the geolocation of the remote transmitter.

15. The method for locating a remote transmitter of claim 13 wherein the moving platforms comprise aircraft.

16. The method for locating a remote transmitter of claim 15 wherein the common location for processing is separate from any of the plurality of moving platforms.

17. The method for locating a remote transmitter of claim 16 wherein a highly accurate, source of time is used to provide the source of the time stamp placed on each signal samples produced in step (a) at all of the aircraft, and wherein the global positioning system is used to provide the source of the location stamp placed on each signal samples produced in step (a) at all of the moving platforms.

18. The method for locating a remote transmitter of claim 17 wherein step (g) comprises utilizing a hill climbing algorithm such as a conjugate gradient search to locate the well defined peak in the summation data set which indicates the geolocation of the remote transmitter.

19. The method for locating a remote transmitter of claim 13 wherein there is more than one antenna and receiver mounted on each moving platforms, and step (a) is repeated for the signals received by each antenna, and further comprising the steps of:

(h) processing the set of signals samples received using each antenna and receiver on a moving platform for each of the plurality of time periods to minimize or remove the effects caused by such things as undesired interfering signals, and thermal background noise; and

(i) generating a single set of cleaned up signal samples for each of the plurality of time periods using the processed sets of signal samples from step (h), the cleaned up signal samples being transmitted to the central location in step (c) after having the time and location stamps placed on each cleaned up signal sample in step (b).

20. The method for locating a remote transmitter of claim 13 wherein step (g) comprises utilizing a hill climbing algorithm such as a conjugate gradient search performed on the summation data set to geolocate the remote transmitter.

21. A method for locating a remote transmitter from which an electromagnetic signal is being received using an antenna and a receiver mounted on each of a plurality of moving platforms, and indicating the geolocation of the transmitter, the method comprising the steps of:

(a) obtaining a plurality of sets of samples of the electromagnetic signal received with the antenna and receiver on each moving platform, there being one set of samples received at each moving platform for each of a plurality of time periods;

(b) placing a time and location stamp on each of the signal samples obtained in step (a) indicating the time when and the location where each signal sample is taken;

(c) transmitting the signal samples received at each moving platform and having the time and location stamps thereon per step (b) to a central location that is separate from any of the plurality of moving platforms;

(d) storing at the central location the set of signal samples transmitted in step (c) from each moving platform for each period of time;

(e) processing the stored set of signal samples from all the moving platforms for each period of time to produce an individual data set for each period of time; and

(f) summing the plurality of individual data sets produced in step (e) to produce a summation data set that has a distinctive point with a well defined peak value that is higher than the value of other peaks in the summation data set, the well defined peak value indicating the geolocation of the remote transmitter, wherein the summing reducing extraneous peaks in the individual data sets produced in step (e) and enhances the well defined peak in the summation data set; and

(g) analyzing the summation data sets produced in step (f) using a hill climbing algorithm such as a conjugate gradient search to locate the well defined peak in the summation data set to determine the geolocation of the remote transmitter.