Reference Frequency Holdover Control Using Oscillator Temperature Slope
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Solution Overview
Problem
Existing reference frequency generating devices struggle to maintain highly accurate output when the voltage controlled oscillator is controlled by holdover capabilities, particularly during rapid temperature changes, as they rely solely on elapsed time and temperature variations for frequency estimation.
Innovation Solution
A reference frequency generating device that uses a temperature approximating function and second-order differentiation to detect local temperature variations and temperature slope changes, allowing for accurate corrections in the aging characteristic of the oscillator, thereby generating a holdover control signal that considers these changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If holdover control is performed using only elapsed time and temperature variations for frequency estimation, then the device can maintain operation during reference signal loss, but the frequency accuracy deteriorates during rapid temperature changes
Solution Approach 1:
The patent applies preliminary action by detecting temperature slope changes (rate of change of temperature) in advance during holdover control. The controller calculates the temperature slope based on stored temperature data and uses this information to proactively correct frequency deviations before they significantly impact accuracy. This allows the system to maintain frequency precision during rapid temperature changes while preserving holdover control capability.
2Adaptability or versatility
If the oscillator temperature changes rapidly from a changing state to a stable state, then thermal shock occurs affecting aging characteristics, but traditional control methods cannot detect this state transition accurately
Solution Approach 1:
The patent applies dynamics by transitioning from static temperature monitoring to dynamic temperature slope analysis. The controller continuously calculates the rate of change of temperature (temperature slope) and detects state transitions when the temperature changes from a rapidly changing state to a stable state. This dynamic approach enables accurate detection of thermal shock conditions and appropriate adjustment of holdover control parameters.
Solution Approach 2:
The patent applies feedback by using the detected temperature slope information to continuously adjust the frequency correction in holdover control. The controller monitors temperature changes, calculates the slope, and feeds this information back to modify the frequency estimation, creating a closed-loop system that adapts to real-time temperature conditions and maintains frequency accuracy.
Data Source
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AI summary
To provide a reference frequency generating device that can output a highly accurate reference frequency signal even if a reference signal becomes unable to be acquired. The reference frequency generating device includes a synchronization circuit, a temperature sensor, and a controller. The synchronization circuit controls a reference frequency signal outputted from a voltage controlled oscillator, by a control signal obtained based on a reference signal. The temperature detector detects a temperature of the voltage controlled oscillator being used. When the reference signal is unable to be acquired, the controller corrects a voltage controlled signal in consideration of a distortion in the aging characteristic of the voltage controlled oscillator based on a rate of change with time in a slope of the oscillator temperature, and generates a holdover control signal based on corrected contents to control the voltage controlled oscillator.