Method and system for sharing an oscillator for processing cellular radio signals and GNSS radio data signals by deferring AFC

• US 8,681,043 B2
• Filed: 02/06/2012
• Issued: 03/25/2014
• Est. Priority Date: 12/31/2009
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Abraham, Charles, Walley, John
• Primary Examiner(s): Keith, Jack W
• Assistant Examiner(s): Mull, Fred H
• Application Number:
  US13/367,333
• Publication Number:
  US 20120223858A1
• Time in Patent Office: 778 Days
• Field of Search: 342/357.62, 342/357.76
• US Class Current: 342/357.62
• CPC Class Codes: G01S 19/235 Calibration of receiver components
• CPC Class Codes: G01S 19/36 relating to the receiver frond end

Abstract

A global navigation satellite system (GNSS) enabled mobile device comprising a crystal oscillator and an automatic frequency correction (AFC) circuit may be operable to share the crystal oscillator between processing of cellular radio signals and processing of GNSS data messages. The GNSS enabled mobile device may be operable to enforce an AFC correction when the crystal oscillator drifts beyond a specific frequency error. The AFC correction may be allowed during time intervals corresponding to GNSS words at which decoding of these words is not required. The GNSS enabled mobile device may be operable to disable the AFC correction during time intervals associated with decoding of words while the crystal oscillator may drift within the specific frequency error range. After the decoding of one or more of words is completed, the AFC correction may be allowed during the time intervals corresponding to these words.

Claims

1. A global navigation satellite system (GNSS) enabled mobile device, comprising:

a wireless transceiver configured to process a cellular radio signal;

a GNSS receiver configured to process a GNSS data message;

a crystal oscillator shared between said wireless transceiver and said GNSS receiver; and

an automatic frequency correction (AFC) manager configured;

to determine time intervals within a time period corresponding to a frame of said GNSS data message for AFC, and

to control said AFC based on said determined time intervals and a clock reference associated with said cellular radio signal.

2. The GNSS enabled mobile device according to claim 1, wherein said AFC manager is further configured to enforce said AFC when said crystal oscillator drifts beyond a specific frequency error range.

3. The GNSS enabled mobile device according to claim 1, wherein said frame of said GNSS data message comprises a plurality of subframes, and each of said plurality of subframes comprises a plurality of words, and said plurality of words comprise a telemetry word, a handover word and a plurality of data words.

4. The GNSS enabled mobile device according to claim 3, wherein said AFC manager is configured to allow said AFC during said time intervals when decoding of one or more of said plurality of data words is not required to control said AFC.

5. The GNSS enabled mobile device according to claim 3, wherein said AFC manager is configured to allow said AFC during said time intervals when said plurality of data words are associated with almanac data.

6. The GNSS enabled mobile device according to claim 3, wherein said AFC manager is configured to disable said AFC during said time intervals associated with decoding of one or more of said plurality of words while said crystal oscillator drifts within a specific frequency error range to control said AFC.

7. The GNSS enabled mobile device according to claim 6, wherein said AFC correction manager is configured to allow said AFC during said time intervals that occur after completion of said decoding of said one or more of said plurality of words to control said AFC.

8. The GNSS enabled mobile device according to claim 7, wherein said AFC manager is configured to allow said AFC during said time intervals corresponding to said telemetry word and said handover word after a GNSS time is decoded to control said AFC.

9. The GNSS enabled mobile device according to claim 1, wherein said GNSS receiver is further configured to receive said GNSS data message from a global positioning system (GPS) satellite.

10. The GNSS enabled mobile device according to claim 1, wherein said GNSS receiver is further configured to receive said GNSS data message from a global orbiting navigation satellite system (GLONASS) satellite.

11. A global navigation satellite system (GNSS) enabled mobile device, comprising:

a wireless transceiver configured to process a cellular radio signal using a clock reference derived from a crystal oscillator;

a GNSS receiver configured to process a GNSS data message using a second clock reference derived from said crystal oscillator;

an automatic frequency correction (AFC) block configured to adjust a frequency of said crystal oscillator; and

an AFC manager configured to direct said AFC block to adjust said frequency of said crystal oscillator during a time interval within a time period corresponding to a portion of said GNSS data message that occurs after completion of decoding of said portion of said GNSS data message.

12. The GNSS enabled mobile device according to claim 11, wherein said crystal oscillator comprises:

a digitally controlled crystal oscillator (DCXO);

or

a voltage controlled temperature compensated crystal oscillator.

13. The GNSS enabled mobile device according to claim 11, wherein said AFC block comprises:

a bank of switched capacitors configured to be controlled by said AFC manager to adjust said frequency of said crystal oscillator.

14. The GNSS enabled mobile device according to claim 11, wherein said portion of said GNSS data message comprises:

a data word associated with almanac data.

15. The GNSS enabled mobile device according to claim 11, wherein said AFC manager is further configured to disable said AFC block during a second time interval associated with decoding of said portion of said GNSS data message while said crystal oscillator drifts within a specific frequency error range.

16. The GNSS enabled mobile device according to claim 11, wherein said AFC manager is further configured to direct said AFC block to adjust said frequency of said crystal oscillator when said crystal oscillator drifts beyond a specific frequency error range.

17. The GNSS enabled mobile device according to claim 16, wherein said specific frequency error range is based on said clock reference.

18. The GNSS enabled mobile device according to claim 11, further comprising:

a host processor configured to process signals from said wireless transceiver and said GNSS receiver.

19. A global navigation satellite system (GNSS) enabled mobile device, comprising:

a wireless transceiver configured to process a cellular radio signal using a clock reference derived from a crystal oscillator;

a GNSS receiver configured to process a GNSS data message using a second clock reference derived from said crystal oscillator;

an automatic frequency correction (AFC) block configured to adjust a frequency of said crystal oscillator; and

an AFC manager configured to direct said AFC block to adjust said frequency of said crystal oscillator during a time interval within a time period corresponding to a portion of said GNSS data message that is not required to be decoded by said GNSS receiver.

20. The GNSS enabled mobile device according to claim 19, wherein said portion of said GNSS data message comprises:

a telemetry word;

or

a handover word.