REFERENCE BEACON IDENTIFICATION USING TRANSMISSION SEQUENCE CHARACTERISTICS

• US 20070257832A1
• Filed: 04/12/2006
• Published: 11/08/2007
• Est. Priority Date: 04/12/2006
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Lommen, Layne
• Granted Patent: US 7,411,548 B2
• Time in Patent Office: Days
• US Class Current: 342/52
• CPC Class Codes: G01S 5/021 Calibration, monitoring or correction G01S5/0252 takes precedence
• 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

A method and apparatus for encoding information in a reference beacon signal for use in a time-difference-of-arrival/frequency-difference-of-arrival (TDOA/FDOA) geolocation system. Information is encoded in the reference beacon signal using variations in the times and frequencies of sequential reference signal transmissions. The encoded information may include an identifier associated with the transmitter of the reference beacon signal. A geolocation system receiving the reference beacon signal can thus differentiate it from non-cooperative target emissions as well as from other reference beacon signals.

Claims

1. A method of identifying a transmitter of a reference beacon signal for geolocation error correction, comprising:

sequentially transmitting a plurality of reference beacon signal segments, each reference beacon signal segment being characterized by a frequency parameter and a time parameter, wherein at least one of the frequency and the time parameter of each reference beacon signal segment is determined in accordance with a reference beacon identifier.

2. The method of claim 1, wherein the time parameter of each reference beacon signal segment includes a start time of the reference beacon signal segment and the frequency parameter of each reference beacon signal segment includes a frequency of the reference beacon signal segment.

3. The method of claim 1, wherein a difference in the frequency parameters of adjacent reference beacon signal segments is indicative of a portion of the reference beacon identifier.

4. The method of claim 3, wherein the portion of the reference beacon identifier is a bit, the bit having a first binary value if the difference in frequency parameters has a first differential frequency value and the bit having a second binary value if the difference in frequency parameters has a second differential frequency value.

5. The method of claim 2, wherein the start time of a reference beacon signal segment relative to the other reference beacon signal segments is indicative of a position of the reference beacon signal segment within the plurality of reference beacon signal segments.

6. The method of claim 5, wherein the start times of the sequentially transmitted reference beacon signal segments follow a predetermined progression.

7. The method of claim 6, wherein the predetermined progression is in accordance with the following expressions:

D=D0+D1*N/2 for N=even, and
D=D0−

D1*(N+1)/2 for N=odd,

where D is the time interval between the start of the Nth and (N+1)th reference beacon signal segments, and D0 and D1 are predetermined parameters, with D1=f*D0, wherein 0<

f<

1.

8. The method of claim 3, wherein the portion of the reference beacon identifier is a bit, the bit having a first binary value if the frequency parameters follow a first predetermined progression and the bit having second binary value if the frequency parameters follow a second predetermined progression.

9. The method of claim 1, wherein each of the plurality of reference beacon signal segments includes a pseudo-random waveform.

10. The method of claim 1, comprising:

receiving at least a portion of the plurality of reference beacon signal segments; and

extracting the reference beacon identifier from the received reference beacon signal segments.

11. The method of claim 1, wherein the time parameter of each reference beacon signal segment is indicative of a portion of the reference beacon identifier.

12. The method of claim 11, wherein the portion of the reference beacon identifier is a bit, the bit having a first binary value if the time parameter has a first value and the bit having a second binary value if the time parameter has a second value.

13. The method of claim 2, wherein the frequency of a reference beacon signal segment is indicative of a position of the reference beacon signal segment within the plurality of reference beacon signal segments.

14. The method of claim 13, wherein the frequencies of the sequentially transmitted reference beacon signal segments follow a predetermined progression.

15. The method of claim 11, wherein the portion of the reference beacon identifier is a bit, the bit having a first binary value if the time parameters follow a first predetermined progression and the bit having second binary value if the time parameters follow a second predetermined progression.

16. An apparatus for identifying a transmitter of a reference beacon signal for geolocation error correction, comprising:

means for sequentially transmitting a plurality of reference beacon signal segments, each reference beacon signal segment being characterized by a frequency parameter and a time parameter, wherein at least one of the frequency and the time parameter of each reference beacon signal segment is determined in accordance with a reference beacon identifier.

17. The apparatus of claim 16, wherein the time parameter of each reference beacon signal segment includes a start time of the reference beacon signal segment and the frequency parameter of each reference beacon signal segment includes a frequency of the reference beacon signal segment.

18. The apparatus of claim 16, wherein a difference in the frequency parameters of adjacent reference beacon signal segments is indicative of a portion of the reference beacon identifier.

19. The apparatus of claim 18, wherein the portion of the reference beacon identifier is a bit, the bit having a first binary value if the difference in frequency parameters has a first differential frequency value and the bit having a second binary value if the difference in frequency parameters has a second differential frequency value.

20. The apparatus of claim 17, wherein the start time of a reference beacon signal segment relative to the other reference beacon signal segments is indicative of a position of the reference beacon signal segment within the plurality of reference beacon signal segments.

21. The apparatus of claim 20, wherein the start times of the sequentially transmitted reference beacon signal segments follow a predetermined progression.

22. The apparatus of claim 21, wherein the predetermined progression is in accordance with the following expressions:

D=D0+D1*N/2 for N=even, and
D=D0−

D1*(N+1)/2 for N=odd,

where D is the time interval between the start of the Nth and (N+1)th reference beacon signal segments, and D0 and D1 are predetermined parameters, with D1=f*D0, wherein 0<

f<

1.

23. The apparatus of claim 18, wherein the portion of the reference beacon identifier is a bit, the bit having a first binary value if the frequency parameters follow a first predetermined progression and the bit having second binary value if the frequency parameters follow a second predetermined progression.

24. The apparatus of claim 16, wherein each of the plurality of reference beacon signal segments includes a pseudo-random waveform.

25. The apparatus of claim 16, comprising:

means for receiving at least a portion of the plurality of reference beacon signal segments; and

means for extracting the reference beacon identifier from the received reference beacon signal segments.

26. The apparatus of claim 16, wherein the time parameter of each reference beacon signal segment is indicative of a portion of the reference beacon identifier.

27. The apparatus of claim 26, wherein the portion of the reference beacon identifier is a bit, the bit having a first binary value if the time parameter has a first value and the bit having a second binary value if the time parameter has a second value.

28. The apparatus of claim 17, wherein the frequency of a reference beacon signal segment is indicative of a position of the reference beacon signal segment within the plurality of reference beacon signal segments.

29. The apparatus of claim 28, wherein the frequencies of the sequentially transmitted reference beacon signal segments follow a predetermined progression.

30. The apparatus of claim 26, wherein the portion of the reference beacon identifier is a bit, the bit having a first binary value if the time parameters follow a first predetermined progression and the bit having second binary value if the time parameters follow a second predetermined progression.