System and method for selecting optimum local oscillator discipline source

• US 8,576,014 B2
• Filed: 02/06/2012
• Issued: 11/05/2013
• Est. Priority Date: 06/19/2009
• Status: Expired due to Fees

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Smiley, Russell, Nicholls, Charles
• Primary Examiner(s): Chang, Joseph
• Assistant Examiner(s): SHIN, JEFFREY M
• Application Number:
  US13/366,765
• Publication Number:
  US 20120133443A1
• Time in Patent Office: 638 Days
• Field of Search: 331/2, 331/10, 331/11, 331/46, 331/49, 331/50
• US Class Current: 331/18
• CPC Class Codes: G06F 1/14 Time supervision arrangements, e.g. real time clock
• CPC Class Codes: H03L 7/00 Automatic control of frequency or phase; Synchronisation
• CPC Class Codes: H03L 7/087 using at least two phase detectors or a frequency and phase detector in the loop

Abstract

A device is provided having a local oscillator (LO) configured to generate a first signal having timing information, frequency information, phase information or combinations thereof. The device also includes a prioritizer comprising at least two inputs, each input configured to receive a respective second signal having timing information, frequency information, phase information or combinations thereof. The prioritizer is configured to determine an accuracy of at least one second signal of the at least two second signals in relation to a second signal assigned to be a most accurate of the at least two second signals. The prioritizer is also configured to order the at least two second signals from most accurate to least accurate. The LO is disciplined to correct an offset error of the LO relative to a most accurate second signal that is available to the device, based on the order of the at least two second signals.

Claims

1. A system, comprising:

a local oscillator; and

a discipline signal provider configured to;

receive at least two reference signals;

compare each received reference signal to an output of the local oscillator to derive a respective correction signal associated with each reference signal;

select the correction signal associated with the reference signal deemed most accurate; and

provide the selected correction signal to the local oscillator; and

discipline the local oscillator based on the received reference signal deemed to be most accurate.

2. The system of claim 1, wherein the discipline signal provider is operable to:

receive a primary reference signal and at least two secondary reference signals;

compare the secondary reference signals to the primary reference signal to determine a most accurate secondary reference signal;

discipline the local oscillator based on the primary reference signal when the primary reference signal is available; and

discipline the local oscillator based on the secondary reference signal determined to be most accurate when the primary reference signal is not available.

3. The system of claim 1, wherein the discipline signal provider is operable to:

order the reference signals from a reference signal deemed most accurate to a reference signal deemed least accurate;

discipline the local oscillator based on the reference signal deemed most accurate when the reference signal deemed most accurate is available; and

discipline the local oscillator based on a reference signal deemed next most accurate when the reference signal deemed most accurate is not available.

4. The system of claim 1, wherein the discipline signal provider is operable to:

order the reference signals from a reference signal deemed most accurate to a reference signal deemed least accurate;

discipline the local oscillator based on the reference signal deemed most accurate until the reference signal deemed most accurate is interrupted; and

discipline the local oscillator based on a reference signal deemed next most accurate when the reference signal deemed most accurate is interrupted.

5. The system of claim 4, wherein the discipline signal provider is operable to discipline the local oscillator based on the reference signal deemed most accurate when the signal deemed most accurate is restored.

6. The system of claim 1, wherein the discipline signal provider is operable to:

select the correction signal associated with the reference signal deemed most accurate when the reference signal deemed most accurate is available; and

select the correction signal associated with a reference signal deemed next most accurate when the reference signal deemed most accurate is not available.

7. The system of claim 1, wherein the discipline signal provider is operable to determine availability of each reference signal of the at least two reference signals.

8. The system of claim 7, wherein the discipline signal provider is operable to determine availability of at least one reference signal by receiving information from at least one source external to the discipline signal provider, the information pertaining to the availability of the at least one reference signal.

9. The system of claim 1, wherein:

the local oscillator generates a signal comprising at least one of;

timing information;

frequency information; and

phase information; and

the discipline signal provider receives reference signals comprising at least one of;

timing information;

frequency information; and

phase information.

10. The system of claim 1, wherein the discipline signal provider is configured to receive at least one reference signal selected from a group comprising:

a GPS timing signal;

a network timing signal;

a network frequency signal;

a signal generated by a mathematical model of the local oscillator;

a signal comprising synchronization information; and

a signal derived from a period during which the local oscillator was disciplined by a primary reference signal.

11. A method of operating a local oscillator, comprising:

receiving at least two reference signals;

comparing each received reference signal to an output of the local oscillator to derive a respective correction signal associated with each reference signal;

selecting the correction signal associated with the reference signal deemed most accurate; and

providing the selected correction signal to the local oscillator to discipline the local oscillator; and

disciplining the local oscillator based on the received reference signal deemed to be most accurate.

12. The method of claim 11 further comprising:

receiving a primary reference signal and at least two secondary reference signals;

comparing the secondary reference signals to the primary reference signal to determine a most accurate secondary reference signal;

disciplining the local oscillator based on the primary reference signal when the primary reference signal is available; and

disciplining the local oscillator based on the secondary reference signal determined to be most accurate when the primary reference signal is not available.

13. The method of claim 11 further comprising:

ordering the reference signals from a reference signal deemed most accurate to a reference signal deemed least accurate;

disciplining the local oscillator based on the reference signal deemed most accurate when the reference signal deemed most accurate is available; and

disciplining the local oscillator based on a reference signal deemed next most accurate when the reference signal deemed most accurate is not available.

14. The method of claim 11 further comprising:

ordering the reference signals from a reference signal deemed most accurate to a reference signal deemed least accurate;

disciplining the local oscillator based on the reference signal deemed most accurate until the reference signal deemed most accurate is interrupted; and

disciplining the local oscillator based on a reference signal deemed next most accurate when the reference signal deemed most accurate is interrupted.

15. The method of claim 14 further comprising:

disciplining the local oscillator based on the reference signal deemed most accurate when the signal deemed most accurate is restored.

16. The method of claim 11 further comprising:

selecting the correction signal associated with the reference signal deemed most accurate when the reference signal deemed most accurate is available; and

selecting the correction signal associated with a reference signal deemed next most accurate when the reference signal deemed most accurate is not available.

17. The method of claim 11 further comprising determining availability of each reference signal of the at least two reference signals.

18. The method of claim 17 further comprising determining availability of at least one reference signal by receiving information from at least one source external to the discipline signal provider, the information pertaining to the availability of the at least one reference signal.

19. The method of claim 11, wherein:

the local oscillator generates a signal comprising at least one of;

timing information;

frequency information; and

phase information; and

the reference signals comprise at least one of;

timing information;

frequency information; and

phase information.

20. The method of claim 11 further comprising receiving at least one reference signal selected from a group comprising:

a GPS timing signal;

a network timing signal;

a network frequency signal;

a signal generated by a mathematical model of the local oscillator;

a signal comprising synchronization information; and

a signal derived from a period during which the local oscillator was disciplined by a primary reference signal.