Atomic Clock Calibration for GPS Reference Loss Continuity
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Solution Overview
Problem
Current atomic clock systems face challenges in maintaining phase and frequency continuity during disruptions in the primary timing reference, such as loss of GPS signals, leading to inaccuracies in downstream systems.
Innovation Solution
The atomic clock system incorporates a tunable local oscillator, follower circuit, atom referenced circuit, switch, controller, and memory to selectively apply digital pumping signals, allowing it to maintain the output frequency and phase by using stored operating settings when an external reference signal is removed, ensuring continuity with the last detected reference signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the atomic clock locks its output frequency to a primary timing reference (GPS), then the timing accuracy is improved, but when the reference is disrupted the clock reverts to free running frequency causing phase and frequency discontinuity
Solution Approach 1:
The system pre-calibrates the atomic clock frequency to match the primary reference frequency before disruption occurs. The calibration circuit stores the relationship between the atomic clock's free-running frequency and the reference frequency, enabling the clock to maintain continuity by applying pre-determined frequency adjustments even when the reference signal is lost.
Solution Approach 2:
A calibration circuit acts as an intermediary between the atomic clock and the primary reference. This circuit captures and stores the frequency relationship during normal operation, then uses this stored information to maintain phase and frequency continuity when the reference signal is disrupted, preventing direct reversion to free-running mode.
2Adaptability or versatility
If the atomic clock uses free running frequency without external reference, then the clock operates independently, but the output frequency deviates from the primary reference causing timing errors
Solution Approach 1:
The system performs preliminary calibration to establish the frequency offset between the atomic clock's free-running state and the primary reference frequency. This pre-established relationship allows the clock to operate independently while maintaining frequency accuracy by applying the calibrated adjustment.
Solution Approach 2:
The calibration circuit continuously monitors the relationship between the atomic clock output and the primary reference, using this feedback to determine the necessary frequency adjustment. This feedback mechanism ensures that when operating independently, the clock maintains accurate frequency by applying the learned calibration data.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution ensures that the atomic clock maintains accurate timing by switching to stored settings when the external reference is lost, preventing phase and frequency deviations and ensuring minimal disruption to downstream systems.
Implementation Method 1
The atomic spectroscopy circuit is configured to excite the ensemble of atoms with the synthesized signal. The ensemble of atoms has a spectroscopic response at an atomic resonance frequency.
Data Source
AI summary
An atomic clock is provided. An output of a tunable LO is coupled to a user output of the atomic clock. A charge pump adjusts the tunable LO with a LO tuning voltage. A follower circuit sets an output frequency of the atomic clock to a frequency of an external reference signal coupled to an external reference input. An atom referenced circuit sets the output frequency of the atomic clock to a frequency based on stored operating settings. A controller stores then current operating settings generated based on a then current external reference signal coupled to the external reference input. The controller is further configured to apply the stored then current operating settings to the atom referenced circuit when the then current external reference signal is removed from the external reference input to maintain the output frequency of the atomic clock at the output frequency set by the follower circuit.