System and method for built in self test for timing module holdover

• US 8,847,690 B2
• Filed: 09/14/2012
• Issued: 09/30/2014
• Est. Priority Date: 07/06/2009
• Status: Active Grant

• Current Assignee: Malikie Innovations Limited (Key Patent Innovations Limited)
• Original Assignee: Blackberry Limited
• Inventors: Nicholls, Charles, Wu, Philippe
• Primary Examiner(s): Chang, Joseph
• Assistant Examiner(s): Shin, Jeffrey
• Application Number:
  US13/618,387
• Publication Number:
  US 20130046497A1
• Time in Patent Office: 746 Days
• Field of Search: 331/14, 331 16- 18, 331/44
• US Class Current: 331/16
• CPC Class Codes: H03L 1/026 by using a memory for digitally storing correction values H03L1/025 takes precedence
• CPC Class Codes: H03L 1/028 of generators comprising piezoelectric resonators H03L1/021, H03L1/022 take precedence; oscillation generators with a piezoelectric resonator H03B5/32
• CPC Class Codes: H03L 7/0805 the loop being adapted to provide an additional control signal for use outside the loop
• CPC Class Codes: H03L 7/146 by using digital means for generating the oscillator control signal H03L7/141, H03L7/143 take precedence
• CPC Class Codes: H04J 3/0688 Change of the master or reference, e.g. take-over or failure of the master

Abstract

Aspects of the embodiments include a method for synchronizing a device having an oscillator to a reference signal. A correction signal can be determined based on the reference signal. A mathematical model of the oscillator can be trained based at least upon the correction signal. A predicted correction signal for the trained mathematical model can be determined. A time error using the predicted correction signal can be generated to assess suitability of the trained mathematical model for disciplining drift in the oscillator and synchronizing the device when the reference signal is not available.

Claims

1. A method for synchronization of a device having an oscillator to a reference signal, comprising:

determining a correction signal based on the reference signal;

training a mathematical model of the oscillator based at least upon the correction signal;

determining a predicted correction signal for the trained mathematical model; and

generating a time error using the predicted correction signal to assess suitability of the trained mathematical model for disciplining drift in the oscillator and synchronizing the device when the reference signal is not available.

2. The method of claim 1, wherein the correction signal is sampled and the samples are stored.

3. The method of claim 2, wherein the time error is generated by integrating over time a frequency error based upon a difference between the predicted correction signal and the stored samples of the correction signal, wherein the frequency error represents an error that would occur if the predicted correction signal was used to discipline drift in the oscillator.

4. The method of claim 1, further comprising:

determining whether the time error is less than a threshold of an allowable time error for a specified duration of time that the oscillator is locked to the reference signal.

5. The method of claim 4, further comprising:

periodically updating the frequency error, the time error, and whether the time error is less than the threshold at a given interval subsequent to the specified duration of time.

6. The method of claim 1, further comprising:

for two or more mathematical models, selecting a mathematical model for generating a correction signal to discipline drift in the oscillator and to synchronize the device when the reference signal is not available.

7. The method of claim 6, wherein selecting the mathematical model comprises:

comparing the time errors for each of the two or more mathematical models; and

selecting the mathematical model with a smallest cumulative time error that is less than a threshold of an allowable time error.

8. The method of claim 6, further comprising:

maintaining for the specified duration of time an identification of the mathematical model that is selected as having a smallest time error; and

maintaining for at least one interval after the specified duration of time an identification of the mathematical model that is selected as having the smallest time error for each interval.

9. The method of claim 8 further comprising:

maintaining mathematical model parameters associated with the mathematical model identified.

10. The method of claim 8 further comprising:

disciplining the oscillator at an end of a specified duration of time using the selected mathematical model without an additional testing period for testing the selected mathematical model.

11. A method of synchronization of a device having an oscillator to a reference signal, comprising:

training at least two mathematical models of the oscillator based at least in part upon a correction signal, wherein the correction signal is a function of a reference signal which is used to discipline drift in the oscillator; and

selecting a mathematical model of the at least two mathematical models having a smallest time error to discipline drift in the oscillator and synchronize the device to the reference signal when the reference signal is unavailable.

12. The method of claim 11, further comprising:

testing the selected mathematical model using a sampled version of the correction signal such that the selected mathematical model can be used without the need for a testing duration.

13. The method of claim 11, wherein training the at least two mathematical models comprises determining a predicted correction signal for each mathematical model.

14. A device comprising:

a local oscillator (LO) configured to generate a first signal comprising at least one of timing information, frequency information, phase information, and combinations thereof;

a control loop filter for generating a correction signal that is a function of a reference signal used to discipline drift in the LO;

at least one mathematical model of the LO configured to receive the correction signal and generate a predicted correction signal; and

a time interval error checker (TIEC) configured to generate a time error for each mathematical model, wherein the time error represents an error that would occur if the predicted correction signal was used to discipline drift in the oscillator.

15. The device of claim 14, further comprising a digital to analog control (DAC) configured to provide a signal to the LO based on a correction signal from the TIEC, wherein when the reference signal is available the LO is disciplined as a function of the reference signal, and the at least one mathematical model is trained to generate a predicted correction signal.

16. The device of claim 14, wherein the time interval error checker (TIEC) is further configured to select a mathematical model having a smallest time error.

17. The device of claim 16, further comprising a digital to analog control (DAC) selector configured to receive the correction signal of the mathematical model selected by the TIEC, and provide a control signal to the DAC to discipline the oscillator.

18. The device of claim 14, further comprising a sample data buffer for storing samples of the correction signal, timing information from the reference signal, and temperature information.

19. The device of claim 18, wherein the time error for each mathematical model is generated by determining a difference between the predicted correction signal and samples of the correction signal for each mathematical model to produce a frequency error;

and integrating over time the frequency error.

20. The device of claim 14 wherein the at least one mathematical model is at least one of a model that includes (1) both temperature and aging dependent parameters, (2) temperature dependent parameters, (3) a constant value, and (4) parameters of a model selected to have the smallest time error in a previous given interval.