Crystal Oscillator Holdover Correction for Temperature and Aging Drift
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Solution Overview
Problem
Oscillator devices that rely on external clock signals for frequency stability face challenges when these signals are interrupted, leading to instability in generated frequency signals due to temperature and secular changes.
Innovation Solution
An oscillator device incorporating a crystal resonator with a frequency difference detector, temperature detector, correction value calculator, and correction coefficient calculator to calculate and apply frequency correction values based on aging and temperature changes, ensuring stability even during external clock signal interruptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the oscillator device uses an external clock signal for frequency calibration, then the frequency stability is improved, but the system becomes vulnerable to signal interruption and holdover conditions
Solution Approach 1:
The system pre-calculates and stores correction values for secular change and temperature characteristics during periods when the external clock signal is available. These correction values are prepared in advance so that when the external signal is interrupted, the oscillator can immediately switch to using the stored correction values without loss of frequency stability.
Solution Approach 2:
The invention introduces correction values as an intermediary element between the external clock signal and the frequency output. When the external signal is unavailable, these correction values act as a mediator to maintain frequency stability, allowing the system to bridge the gap between external signal dependency and independent operation.
2Reliability
If the oscillator device compensates for temperature change and secular change using calibration signals, then the frequency stability during holdover is improved, but the device complexity increases
Solution Approach 1:
The system changes the parameters being monitored and corrected from raw temperature and time values to pre-calculated correction values. By transforming the correction mechanism to work with directly applicable frequency correction parameters rather than requiring continuous physical measurement and calculation, the system achieves effective compensation with reduced operational complexity.
3Measurement precision
If the oscillator device calculates frequency correction values based on accumulated elapsed time and temperature, then the frequency accuracy is improved, but the measurement and calculation complexity increases
Solution Approach 1:
The oscillator device uses its own internal time-keeping mechanism to track accumulated elapsed time for secular change calculation, eliminating the need for external time reference during holdover. The temperature sensor integrated in the device provides self-contained temperature measurement, making the system self-sufficient for correction value calculation without requiring additional external measurement infrastructure.
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
The device stabilizes frequency signals by calculating and applying correction values during both external clock signal availability and interruptions, maintaining high stability and accuracy.
Implementation Method 1
an oscillating unit 40 that includes a crystal resonator 10 to output a frequency signal
Implementation Method 2
a temperature detector 203 to detect a temperature of an atmosphere where the crystal resonator 10 is disposed
Data Source
AI summary
In an oscillator device that outputs a frequency signal based on an oscillation frequency of a crystal resonator and a frequency setting value, a frequency difference detector that obtains a difference value corresponding to a frequency difference between the output frequency of the oscillator device and an external clock signal and a temperature detector are disposed. An aging coefficient and a temperature characteristic coefficient are obtained based on a secular change of the difference value obtained in the frequency difference detector and a secular change of the detected temperature during a period where the external clock signal is obtained. Furthermore, a frequency correction value is calculated using the aging coefficient and the temperature characteristic coefficient during a holdover period, and the frequency correction value is added to the frequency setting value.