CALCULATING NAVIGATION SYSTEM TIME IN A SATELLITE NAVIGATION SYSTEM

• US 20100073230A1
• Filed: 03/31/2009
• Published: 03/25/2010
• Est. Priority Date: 08/08/2008
• Status: Active Grant

• Current Assignee: Maishi Electronic (Shanghai) Limited
• Original Assignee: Maishi Electronic (Shanghai) Limited
• Inventors: HUANG, Haiquan, YU, Xiaoguang, DU, Sterling
• Granted Patent: US 8,378,889 B2
• Time in Patent Office: Days
• US Class Current: 342/357.630
• CPC Class Codes: G01S 19/235 Calibration of receiver components

Abstract

A satellite navigation system receiver that includes a counter and a controlling unit is described. The counter may be driven by a reference clock signal having a reference clock frequency. The controlling unit can calculate a correction value indicative of a corrected reference clock frequency by comparing an increment of the counter values during a time period with an increment of the navigation system times during the time period. The controlling unit can generate a calculated navigation system time according to the correction value.

Claims

1. A satellite navigation system receiver comprising:

a counter driven by a reference clock signal having a reference clock frequency, wherein said counter provides counter values; and

a controlling unit coupled to said counter and operable for calculating a correction value indicative of a corrected reference clock frequency by comparing an increment of said counter values during a time period with an increment of navigation system times during said time period, wherein said controlling unit is also operable for generating a calculated navigation system time according to said correction value.

2. The receiver of claim 1, wherein said controlling unit calculates said correction value by calculating an average refresh rate of said counter values over a particular period of said navigation system time.

3. The receiver of claim 2, wherein said controlling unit generates said calculated navigation system time according to said average refresh rate of said counter values.

4. The receiver of claim 1, wherein said receiver is operable for determining navigation bit boundaries according to said calculated navigation system time.

5. The receiver of claim 1, wherein said receiver is operable for determining visibility of satellites according to said calculated navigation system time.

6. The receiver of claim 1, further comprising a sampling clock coupled to said controlling unit and operable for digitizing a received satellite signal, wherein said reference clock signal is provided by said sampling clock.

7. The receiver of claim 1, further comprising a real time clock circuit coupled to said controlling unit and operable for providing a local time, wherein said controlling unit is also operable for determining if said counter values are correct according to said local time.

8. The receiver of claim 7, further comprising a sampling clock coupled to said controlling unit and operable for digitizing a received satellite signal, wherein said real time clock circuit is driven by said sampling clock.

9. A method for positioning a satellite navigation system receiver, comprising:

generating a reference clock signal having a reference clock frequency;

calculating a correction value indicative of a corrected reference clock frequency by counting clock pulses of said reference clock signal over a particular period of navigation system time;

generating a calculated navigation system time according to said correction value; and

employing said calculated navigation system time during calculation of a current position result of said receiver.

10. The method of claim 9, further comprising:

determining navigation bit boundaries according to said calculated navigation system time.

11. The method of claim 9, further comprising:

determining visibility of satellites according to said calculated navigation system time.

12. The method of claim 9, further comprising:

driving a counter by said reference clock signal for providing counter values; and

calculating said correction value by comparing an increment of said counter values during a time period with an increment of said navigation system times during said time period.

13. The method of claim 9, further comprising:

calculating said correction value by calculating an average refresh rate of said counter values over a particular period of said navigation system time.

14. The method of claim 13, further comprising:

generating said calculated navigation system time according to said average refresh rate of said counter values.

15. The method of claim 9, further comprising:

digitizing a received satellite signal with a sampling clock; and

generating said reference clock signal by said sampling clock.

16. The method of claim 9, further comprising:

generating a local time by a real time clock circuit; and

determining if said counter values are correct according to said local time.

17. The method of claim 16, further comprising:

digitizing a received satellite signal with a sampling clock; and

driving said real time clock circuit by said sampling clock.

18. A satellite navigation system receiver, comprising:

a radio frequency (RF) front end operable for converting a frequency of a received satellite signal to a desired frequency;

a clock coupled to said RF front end and operable for generating a reference clock signal having a reference clock frequency;

a baseband processing unit coupled to said RF front end and operable for acquiring and tracking satellite signals and for calculating position results of said receiver; and

a controlling unit coupled to said baseband processing unit and operable for calculating a correction value indicative of a corrected reference clock frequency by counting clock pulses of said reference clock signal over a particular period of navigation system time, and also operable for generating a calculated navigation system time according to said correction value,

wherein said baseband processing unit is operable for employing said calculated navigation system time during calculation of a current position result of said receiver.

19. The receiver of claim 18, further comprising a counter driven by said reference clock signal for providing counter values, wherein said controlling unit calculates said correction value by comparing an increment of said counter values during a time period with an increment of said navigation system times during said time period.

20. The receiver of claim 19, wherein said controlling unit calculates said correction value according to the following equation:

21. The receiver of claim 20, wherein said controlling unit generates said calculated navigation system time according to the following equation:

22. The receiver of claim 18, wherein said baseband processing unit is operable for determining navigation bit boundaries according to said calculated navigation system time.

23. The receiver of claim 18, wherein said baseband processing unit is operable for determining visibility of satellites according to said calculated navigation system time.

24. The receiver of claim 18, wherein said received satellite signal is digitized by said clock.

25. The receiver of claim 18, further comprising a real time clock circuit coupled to said controlling unit and operable for providing a local time, wherein said controlling unit is operable for determining if said counter values are correct according to said local time.

26. The receiver of claim 25, wherein said received satellite signal is digitized by said clock, and wherein said real time clock circuit is driven by said clock.