High-precision radio frequency ranging system

• US 8,199,047 B2
• Filed: 03/09/2010
• Issued: 06/12/2012
• Est. Priority Date: 03/09/2010
• Status: Active Grant

• Current Assignee: ENSCO, Incorporated (Teris LLC)
• Original Assignee: ENSCO, Incorporated (Teris LLC)
• Inventors: Fretenburg, Russell Alan, Leung, Henry Hon-You, Pyner, Derek John, Farnsworth, Bradley David, Taylor, David W. A. Jr.
• Primary Examiner(s): Brainard, Timothy A
• Application Number:
  US12/659,448
• Publication Number:
  US 20110221632A1
• Time in Patent Office: 826 Days
• Field of Search: 342/118, 342/145
• US Class Current: 342/145
• CPC Class Codes: G01S 13/325 using transmission of coded signals, e.g. P.S.K. signals
• CPC Class Codes: G01S 13/84 for distance determination by phase measurement
• CPC Class Codes: G01S 13/878 Combination of several spaced transmitters or receivers of known location for determining the position of a transponder or a reflector G01S13/874 takes precedence

Abstract

Methods for estimating a distance between an originator and a transponder, methods for calculating a fine time adjustment in a radio, computer-readable storage media containing instructions to configure a processor to perform such methods, originators used in a system for estimating a distance to a transponder, and transponders used in a system for estimating a distance to an originator. The methods utilize fine time adjustments to achieve sub-clock cycle time resolution. The methods may utilize offset master clocks. The methods may utilize a round-trip full-duplex configuration or a round-trip half-duplex configuration. The method produces accurate estimates of the distance between two radios.

Claims

1. A method for estimating a distance between an originator and a transponder, the method comprising:

transmitting a first message from a first channel in said originator;

receiving a second message on a second channel in said originator;

calculating a coarse time measurement of the round-trip propagation time between said originator and said transponder,

calculating a fine time adjustment in said originator comprising;

calculating a plurality of peak error measurements of a correlator output in said second channel of said originator during a time period;

calculating a rate of change of said plurality of peak error measurements during said time period; and

estimating a peak error at a point after said time period by using said rate of change of said plurality of peak error measurements during said time period;

calculating a round-trip propagation time using said coarse time measurement and said fine time adjustment; and

calculating an estimated distance between said originator and said transponder using said round-trip propagation time.

2. The method of claim 1, wherein said point after said time period corresponds with said second channel of said originator receiving a synchronization word.

3. The method of claim 2, wherein said originator includes a first channel functioning at a specified master clock frequency and said originator includes a second channel functioning at a master clock frequency other than said specified master clock frequency.

4. The method of claim 3, wherein a first clock outputs said specified master clock frequency and a second clock outputs said master clock frequency other than said specified master clock frequency.

5. The method of claim 3, wherein a first clock outputs said specified master clock frequency and a direct digital synthesis device outputs said master clock frequency other than said specified master clock frequency.

6. A method for estimating a distance between an originator and a transponder, the method comprising:

transmitting a first message from said originator to said transponder;

transmitting a second message from said transponder to said originator;

calculating a coarse time measurement of the round-trip propagation time between said originator and said transponder;

calculating a first fine time adjustment in said transponder comprising;

calculating a first plurality of peak error measurements of a correlator output in said transponder during a first time period;

calculating a rate of change of said first plurality of peak error measurements during said first time period; and

estimating a peak error at a point after said first time period by using said rate of change of said first plurality of peak error measurements during said first time period;

calculating a second fine time adjustment in said originator comprising;

calculating a second plurality of peak error measurements of a correlator output in said originator during a second time period;

calculating a rate of change of said second plurality of peak error measurements during said second time period; and

estimating a peak error at a point after said second time period by using said rate of change of said second plurality of peak error measurements during said second time period;

calculating a round-trip propagation time using said coarse time measurement and said first and second fine time adjustments; and

calculating an estimated distance between said originator and said transponder using said round-trip propagation time.

7. The method of claim 6, wherein said point after said first time period corresponds with said transponder receiving a synchronization word and said point after said second time period corresponds with said originator receiving a synchronization word.

8. The method of claim 7, wherein said originator operates at a specified master clock frequency and said transponder operates at a frequency other than said specified master clock frequency.

9. A computer-readable storage medium containing instructions to configure a processor to perform a method for estimating a distance between an originator and a transponder, the method comprising:

transmitting a first message from a first channel in said originator;

receiving a second message on a second channel in said originator;

calculating a coarse time measurement of the round-trip propagation time between said originator and said transponder;

calculating a fine time adjustment in said originator comprising;

calculating a plurality of peak error measurements of a correlator output in said second channel of said originator during a time period;

calculating a rate of change of said plurality of peak error measurements during said time period; and

estimating a peak error at a point after said first time period by using said rate of change of said plurality of peak error measurements during said time period;

calculating a round-trip propagation time using said coarse time measurement and said fine time adjustment; and

calculating an estimated distance between said originator and said transponder using said round-trip propagation time.

10. The method of claim 9, wherein said point after said first time period corresponds with said second channel of said originator receiving a synchronization word.

11. The method of claim 10, wherein said originator includes a first channel functioning at a specified master clock frequency and said originator includes a second channel functioning at a master clock frequency other than said specified master clock frequency.

12. The method of claim 11, wherein a first clock outputs said specified master clock frequency and a second clock outputs said master clock frequency other than said specified master clock frequency.

13. The method of claim 11, wherein a first clock outputs said specified master clock frequency and a direct digital synthesis device outputs said master clock frequency other than said specified master clock frequency.

14. A computer-readable storage medium containing instructions to configure a processor to perform method for estimating a distance between an originator and a transponder, the method comprising:

transmitting a first message from said originator to said transponder;

transmitting a second message from said transponder to said originator;

calculating a coarse time measurement of the round-trip propagation time between said originator and said transponder;

calculating a first fine time adjustment in said transponder comprising;

calculating a first plurality of peak error measurements of a correlator output in said transponder during a first time period;

calculating a rate of change of said first plurality of peak error measurements during said first time period; and

estimating a peak error at a point after said first time period by using said rate of change of said first plurality of peak error measurements during said first time period;

calculating a second fine time adjustment in said originator comprising;

calculating a second plurality of peak error measurements of a correlator output in said originator during a second time period;

calculating a rate of change of said second plurality of peak error measurements during said second time period; and

estimating a peak error at a point after said second time period by using said rate of change of said second plurality of peak error measurements during said second time period;

calculating a round-trip propagation time using said coarse time measurement and said first and second fine time adjustments; and

calculating an estimated distance between said originator and said transponder using said round-trip propagation time.

15. The method of claim 14, wherein said point after said first time period corresponds with said transponder receiving a synchronization word and said point after said second time period corresponds with said originator receiving a synchronization word.

16. The method of claim 15, wherein said originator operates at a specified master clock frequency and said transponder operates at a frequency other than said specified master clock frequency.

17. A computer-readable storage medium containing instructions to configure a processor to perform a method for calculating a fine time adjustment in a radio, the method comprising:

calculating a plurality of peak error measurements of a correlator output in said radio during a time period;

calculating a rate of change of said plurality of peak error measurements during said time period; and

estimating a peak error at a point after said time period by using said rate of change of said plurality of peak error measurements during said time period.

18. An originator for estimating a distance between said originator and a transponder, said originator comprising:

transmission means for transmitting a first message from a first channel in said originator;

receiving means for receiving a second message on a second channel in said originator;

calculating means for calculating a coarse time measurement of the round-trip propagation time between said originator and said transponder;

calculating means for calculating a fine time adjustment comprising;

calculating means for calculating a plurality of peak error measurements of a correlator output in said second channel during a time period;

calculating means for calculating a rate of change of said plurality of peak error measurements during said time period; and

estimating means for estimating a peak error at a point after said time period by using said rate of change of said plurality of peak error measurements during said time period;

calculating means for calculating a round-trip propagation time using said coarse time measurement and said fine time adjustment; and

calculating means for calculating an estimated distance between said originator and said transponder using said round-trip propagation time.

19. The originator of claim 18, wherein said point after said time period corresponds with said second channel of said originator receiving a synchronization word.

20. The originator of claim 19, wherein said originator includes a first channel functioning at a specified master clock frequency and said originator includes a second channel functioning at a master clock frequency other than said specified master clock frequency.

21. The originator of claim 20, wherein a first clock outputs said specified master clock frequency and a second clock outputs said master clock frequency other than said specified master clock frequency.

22. The originator of claim 20, wherein a first clock outputs said specified master clock frequency and a direct digital synthesis device outputs said master clock frequency other than said specified master clock frequency.

23. An originator for estimating a distance between said originator and a transponder, said originator comprising:

transmission means for transmitting a first message to said transponder;

receiving means for receiving a second message from said transponder;

calculating means for calculating a coarse time measurement of the round-trip propagation time between said originator and said transponder;

calculating means for calculating a fine time adjustment comprising;

calculating means for calculating a plurality of peak error measurements of a correlator output in said originator during a time period;

calculating means for calculating a rate of change of said plurality of peak error measurements during said time period; and

estimating means for estimating a peak error at a point after said time period by using said rate of change of said plurality of peak error measurements during said time period;

calculating means for calculating a round-trip propagation time using said coarse time measurement, said fine time adjustment, and at least some data from said second message from said transponder; and

calculating means for calculating an estimated distance between said originator and said transponder using said round-trip propagation time.

24. The originator of claim 23, wherein said point after said time period corresponds with said originator receiving a synchronization word.

25. A transponder for use in a system for estimating a distance between an originator and said transponder, said transponder comprising:

receiving means for receiving a first message from said originator;

calculating means for calculating a fine time adjustment in said transponder comprising;

calculating means for calculating a plurality of peak error measurements of a correlator output in said transponder during a time period;

calculating means for calculating a rate of change of said plurality of peak error measurements during said time period; and

estimating means for estimating a peak error at a point after said time period by using said rate of change of said plurality of peak error measurements during said time period; and

transmission means for transmitting a second message to said originator.

26. The transponder of claim 25, wherein said point after said time period corresponds with said transponder receiving a synchronization word.

27. The transponder of claim 25, wherein at least two of such transponders operate in a network of transponders.