Acquisition and tracking of burst code signals

• US 20040125868A1
• Filed: 12/31/2002
• Published: 07/01/2004
• Est. Priority Date: 12/31/2002
• Status: Active Grant

• Current Assignee: L3 Technologies, Inc. (L3Harris Technologies, Inc.)
• Original Assignee: L-3 Communications Corporation (L3Harris Technologies, Inc.)
• Inventors: Mazahreh, Raied N., Lundquist, Alan Earl, Keller, Merle L., Bagley, Zachary C., McEntire, Steven J., Barham, Steven, Willes, Warren Paul, Kingston, Samuel Charles
• Granted Patent: US 7,822,157 B2
• Time in Patent Office: Days
• US Class Current: 375/150
• CPC Class Codes: H04B 1/7075 with code phase acquisition
• CPC Class Codes: H04B 2201/70715 with application-specific features

Abstract

A digital communication system includes a generator for generating a plurality of pulse trains, each having a different timing, and pre-compensation circuitry for synchronizing the plurality of pulse trains to a timing signal. The system also includes comparison circuitry for simultaneously comparing a received burst code signal to each of the plurality of pulse trains, where the burst code signal is synchronized to the timing signal, and a detector for detecting which of the pulse trains is a closest temporal match to the burst code signal. The pre-compensation circuitry operates to reduce acquisition time and keep PN code uncertainties within the range of the comparison circuitry.

Claims

1. A method of acquiring a burst code signal comprising:

generating a plurality of pulse trains, each having a different timing; and

simultaneously comparing the burst code signal to each of the plurality of pulse trains, wherein the burst code signal and the plurality of generated pulse trains are synchronized to a timing signal; and

detecting which of the pulse trains is a closest temporal match to the burst code signal.

2. The method of claim 1, wherein the plurality of pulse trains are generated by a pseudo noise code generator and synchronizing the plurality of generated pulse trains comprises bringing a chipping rate of the pseudo noise code generator into approximate agreement with the accuracy of the timing signal.

3. The method of claim 2, wherein synchronizing the plurality of generated pulse trains further comprises maintaining a composite pseudo noise code phase of pseudo noise code generator substantially coincident with a phase of the timing signal.

4. The method of claim 1, wherein the timing signal is a GPS timing signal.

5. The method of claim 4, wherein synchronizing the plurality of generated pulse trains comprises adjusting a pseudo noise code phase of a pseudo noise code generator to have the same phase as it would have had it begun at the beginning of a GPS day and progressed at a nominal chipping rate ideally achieved with a reference oscillator used for generating the GPS timing signal.

6. The method of claim 4, wherein synchronizing the plurality of generated pulse trains comprises bringing the chipping rate of a pseudo noise code generator approximately to the accuracy of the GPS timing signal.

7. The method of claim 6, wherein synchronizing the plurality of generated pulse trains further comprises maintaining a composite PN code phase of the PN code generator substantially at a GPS time of day.

8. The method of claim 1, wherein simultaneously comparing the burst code signal to each of the plurality of pulse trains includes generating a correlation value for each comparison.

9. The method of claim 8, wherein detecting which of the pulse trains is a closest temporal match is performed by comparing the correlation values.

10. The method of claim 8, wherein simultaneously comparing the burst code signal to each of the plurality of pulse trains utilizes a finite impulse response filter having an impulse response time.

11. The method of claim 10, wherein the burst code signal and the plurality of pulse trains are synchronized to be within the impulse response time.

12. A digital communication system comprising:

a generator for generating a plurality of pulse trains, each having a different timing;

pre-compensation circuitry for synchronizing the plurality of pulse trains to a timing signal comparison circuitry for simultaneously comparing a received burst code signal to each of the plurality of pulse trains, wherein the received burst code signal is synchronized to the timing signal; and

detection circuitry for detecting which of the pulse trains is a closest temporal match to the received burst code signal.

13. The system of claim 12, wherein the generator comprises a pseudo noise code generator.

14. The system of claim 13, wherein the pre-compensation circuitry comprises an output signal for bringing a chipping rate of the pseudo noise code generator into approximate agreement with the accuracy of the timing signal.

15. The system of claim 14, wherein the pre-compensation circuitry further comprises an output signal for maintaining a composite pseudo noise code phase of the pseudo noise code generator substantially coincident with a phase of the timing signal.

16. The system of claim 12, wherein the wherein the timing signal is a GPS timing signal.

17. The system of claim 16, wherein the generator comprises a pseudo noise generator.

18. The system of claim 17, wherein the pre-compensation circuitry comprises an output signal for adjusting a pseudo noise code phase of the pseudo noise code generator to have the same phase as it would have had it begun at the beginning of a GPS day and progressed at a nominal chipping rate ideally achieved with a reference oscillator used for generating the GPS timing signal.

19. The system of claim 17, wherein the pre-compensation circuitry comprises an output signal for bringing a chipping rate of the pseudo noise code generator into approximate agreement with the accuracy of the GPS timing signal.

20. The system of claim 17, wherein the pre-compensation circuitry further comprises an output signal for maintaining a composite pseudo noise code phase of the pseudo noise code generator substantially at a GPS time of day.

21. The system of claim 12, wherein the comparison circuitry generates a correlation value for each comparison.

22. The system of claim 21, wherein the detection circuitry detects which of the pulse trains is a closest temporal match to the received burst code signal, by comparing the correlation values.

23. The system of claim 21, wherein the comparison circuitry comprises a finite impulse response filter having an impulse response time.

24. The system of claim 23, wherein the pre-compensation circuitry synchronizes the plurality of pulse trains to be within the impulse response time.

25. A method of acquiring a burst code signal comprising:

generating a plurality of pulse trains using a pseudo noise code generator, wherein each of the pulse trains has a different timing;

synchronizing a chipping rate of the pseudo noise code generator with a timing signal;

maintaining a composite pseudo noise code phase of the pseudo noise code generator substantially coincident with a phase of the timing signal;

simultaneously comparing the burst code signal to each of the plurality of pulse trains, wherein the burst code signal and the plurality of generated pulse trains are synchronized to a timing signal; and

detecting which of the pulse trains is a closest temporal match to the burst code signal.

26. The method of claim 25, wherein the timing signal is a GPS timing signal.

27. The method of claim 26, wherein synchronizing the plurality of generated pulse trains comprises adjusting a pseudo noise code phase of a pseudo noise code generator to have the same phase as it would have had it begun at the beginning of a GPS day and progressed at a nominal chipping rate ideally achieved with a reference oscillator used for generating the GPS timing signal.

28. The method of claim 26, wherein synchronizing the plurality of generated pulse trains comprises bringing the chipping rate of a pseudo noise code generator approximately to the accuracy of the GPS timing signal.

29. The method of claim 28, wherein synchronizing the plurality of generated pulse trains further comprises maintaining a composite PN code phase of the PN code generator substantially at a GPS time of day.

30. A digital communication system comprising a pluralty of platforms, each platform including:

a pseudo noise code generator for generating a plurality of pulse trains, each having a different timing;

pre-compensation circuitry for correcting a clock rate of the pseudo noise generator to approximate a clock rate of a timing signal, and for maintaining a composite pseudo noise code phase of the pseudo noise code generator substantially coincident with a phase of the timing signal;

correlation circuitry for simultaneously correlating a received burst code signal with each of the plurality of pulse trains, wherein the received burst code signal is synchronized to the timing signal; and

detection circuitry for detecting which of the pulse trains is a closest temporal match to the received burst code signal.

31. The system of claim 30, wherein the wherein the timing signal is a GPS timing signal.

32. The system of claim 31, wherein the pre-compensation circuitry comprises an output signal for adjusting a pseudo noise code phase of the pseudo noise code generator to have the same phase as it would have had it begun at the beginning of a GPS day and progressed at a nominal chipping rate ideally achieved with a reference oscillator used for generating the GPS timing signal.

33. The system of claim 31, wherein the pre-compensation circuitry comprises an output signal for bringing a chipping rate of the pseudo noise code generator into approximate agreement with the accuracy of the GPS timing signal.

34. The system of claim 31, wherein the pre-compensation circuitry further comprises an output signal for maintaining a composite pseudo noise code phase of the pseudo noise code generator substantially at a GPS time of day.

35. The system of claim 30, wherein the correlation circuitry comprises a finite impulse response filter having an impulse response time.

36. The system of claim 35, wherein the pre-compensation circuitry synchronizes the plurality of pulse trains to be within the impulse response time.