Oscillator Aging Correction Using Kalman Hold-Over Estimation
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Solution Overview
Problem
Existing oscillators, such as OCXO and TCXO, face challenges in maintaining high frequency stability due to aging effects, which lead to frequency variations, especially in hold-over states where reference signals are absent or abnormal, making it difficult to achieve accurate aging correction across individual oscillators with varying performance and environmental conditions.
Innovation Solution
A circuit device incorporating a processor that performs signal processing on frequency control data using a Kalman filter process to estimate true values before hold-over states are detected, allowing for accurate aging correction by generating frequency control data that compensates for frequency changes, thereby reducing the impact of element variations and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If aging correction is performed using correspondence relationship information obtained from sample oscillators, then aging correction can be implemented, but the accuracy is insufficient due to individual variations in element performance and environmental conditions
Solution Approach 1:
The system performs preliminary actions by continuously estimating the true value of oscillation frequency through Kalman filter processing during normal operation (before hold-over state occurs). This allows the system to capture real-time aging characteristics specific to each individual oscillator, rather than relying on pre-acquired sample data. The true value estimation is performed in advance and stored for use when hold-over state occurs, ensuring accurate aging correction tailored to each oscillator's actual behavior.
Solution Approach 2:
The system implements feedback by using the phase comparison result between the input signal and reference signal to continuously update the true value estimation through Kalman filter processing. This feedback mechanism allows the system to adapt to individual variations in each oscillator's aging characteristics, improving measurement precision by using actual operational data rather than sample-based correspondence relationship information.
2Reliability
If a hold-over state occurs due to absence or abnormality of reference signal, then the oscillator must maintain frequency stability, but aging effects cause frequency variations that are difficult to correct without real-time true value data
Solution Approach 1:
The system performs preliminary estimation of the true value during normal operation (before hold-over state) using Kalman filter processing on phase comparison results. This true value, which reflects the actual oscillation frequency including aging effects, is stored and held during hold-over state. When hold-over occurs, the system uses this pre-acquired true value to perform accurate aging correction, ensuring frequency stability without requiring real-time reference signals.
3Ease of manufacture
If correspondence relationship information is acquired using a sample oscillator, then the acquisition process is simplified, but element variations cause difficulties in reducing frequency changes across different oscillators
Solution Approach 1:
The system implements self-service by enabling each oscillator to autonomously estimate its own true value during normal operation through Kalman filter processing on its own phase comparison results. This eliminates the need for external sample oscillators and manual acquisition of correspondence relationship information. Each oscillator automatically captures its own aging characteristics, ensuring both ease of implementation and high frequency consistency tailored to each individual device's actual behavior.
Data Source
AI summary
A circuit device includes an oscillation signal generation circuit that generates an oscillation signal having an oscillation frequency using a resonator, the oscillation frequency being a frequency set by using frequency control data, and a processor configured to perform a signal process on input frequency control data based on a phase comparison result between an input signal based on the oscillation signal and a reference signal. The processor is configured to estimate a true value for an observed value of the frequency control data based on the phase comparison result through a Kalman filter process in a period before a hold-over state is detected, and generate aging-corrected frequency control data, in a case where the hold-over state is detected, by holding the true value at a timing corresponding to a timing of detecting the hold-over state, and by performing a calculation based on the true value.