Methods and apparatus to monitor GPS/GNSS atomic clocks are disclosed. An example method includes establishing a measured difference between an atomic frequency standard (AFS) and a monitoring device. The method also includes modeling an estimated difference model between the AFS and the monitoring
Methods and apparatus to monitor GPS/GNSS atomic clocks are disclosed. An example method includes establishing a measured difference between an atomic frequency standard (AFS) and a monitoring device. The method also includes modeling an estimated difference model between the AFS and the monitoring device, and computing a residual signal based on the measured difference and the estimated difference model. In addition, the method includes analyzing, by a first detector, the residual signal at multiple thresholds, each of the thresholds having a corresponding persistency defining the number of times a threshold is exceeded before one or more of a phase jump, a rate jump, or an acceleration error is indicated. Furthermore, the method includes analyzing, by a second detector, a parameter of the estimated difference model at multiple thresholds, each of the thresholds having a corresponding persistency defining the number of times a drift threshold is exceeded before a drift is indicated.
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1. A method, comprising: establishing a measured difference of at least one of a phase or a frequency between an atomic frequency standard (AFS) and a monitoring device;modeling an estimated difference model associated with the at least one of the phase or the frequency between the AFS and the monit
1. A method, comprising: establishing a measured difference of at least one of a phase or a frequency between an atomic frequency standard (AFS) and a monitoring device;modeling an estimated difference model associated with the at least one of the phase or the frequency between the AFS and the monitoring device;computing a residual signal based on the measured difference and the estimated difference model;analyzing, by a first detector, the residual signal at multiple thresholds, each of the thresholds having a corresponding persistency defining a number of times a threshold is exceeded before one or more of a phase jump, a rate jump, or an acceleration error is indicated; andanalyzing, by a second detector, a parameter of the estimated difference model at multiple thresholds, each of the thresholds having a corresponding persistency defining the number of times a drift threshold is exceeded before a drift is indicated. 2. The method as defined in claim 1, further comprising determining, by a voting architecture, a source of the jump or a source of the drift. 3. The method as defined in claim 1, wherein the parameter is rate bias. 4. The method as defined in claim 1, wherein the monitoring device is an independent clock. 5. The method as defined in claim 4, wherein the independent clock is a voltage controlled oscillator or a numerically controlled oscillator. 6. The method as defined in claim 4, wherein the independent clock is a crystal oscillator and a voltage controlled oscillator or numerically controlled oscillator. 7. The method as defined in claim 4, wherein the independent clock is a crystal oscillator. 8. The method as defined in claim 1, wherein the monitoring device is a delayed clock signal of the AFS. 9. The method as defined in claim 8, wherein the delayed clock signal is created using an oscillator-based delay mechanism. 10. The method as defined in claim 8, wherein the delayed clock signal is created using a delay line. 11. An apparatus, comprising: a meter to measure a difference of at least one of a phase or a frequency between an atomic frequency standard (AFS) and a monitoring device;an estimator to model an estimated difference of the at least one of the phase or the frequency between the AFS and the monitoring device;an analyzer to compute a residual signal based on the measured difference and the estimated difference;a first detector to analyze the residual signal at multiple thresholds, each of the thresholds having a corresponding persistency defining a number of times a threshold is exceeded before one or more of a phase jump, a rate jump, or an acceleration error is indicated; anda second detector to analyze a parameter of the estimated difference at multiple thresholds, each of the thresholds having a corresponding persistency defining the number of times a drift threshold is exceeded before a drift is indicated. 12. The apparatus as defined in claim 11, further comprising a voting architecture to determine a source of the jump or a source of the drift. 13. The apparatus as defined in claim 11, wherein the parameter is rate bias. 14. The apparatus as defined in claim 11, wherein the monitoring device is an independent clock. 15. The apparatus as defined in claim 11, wherein the monitoring device is a delayed clock signal of the AFS. 16. A method, comprising: establishing a measured difference of at least one of a phase or a frequency between an atomic frequency standard (AFS) and a monitoring device;modeling an estimated difference model associated with the at least one of the phase or the frequency between the AFS and the monitoring device; anddetecting, by a detector, a drift if a parameter of the estimated difference model exceeds a threshold at a corresponding persistency defining a number of times that a drift threshold is exceeded before a drift is indicated. 17. The method of claim 16, further comprising: analyzing, by the detector, the parameter of the estimated difference model at multiple thresholds, each of the thresholds having a corresponding persistency defining the number of times a drift threshold is exceeded before a drift is indicated. 18. The method as defined in claim 16, wherein the parameter is rate bias. 19. The method as defined in claim 16, wherein the monitoring device is an independent clock. 20. The method as defined in claim 16, wherein the monitoring device is a delayed clock signal of the AFS.
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Allan David W. (Boulder CO) Levine Judah (Boulder CO) Davis Dicky D. (Boulder CO) Weiss Marc A. (Boulder CO), Device and method for providing accurate time and/or frequency.
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