Multi-Reference PLL Clock Synchronization With Reduced Phase Drift
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Solution Overview
Problem
Conventional phase-locked loop (PLL) circuits rely heavily on a single clock reference, leading to accuracy and stability issues when the reference is unstable or inaccurate, and require direct line of sight with multiple satellites for GPS-based timing synchronization, which is time-consuming and prone to phase drift.
Innovation Solution
A PLL apparatus that utilizes multiple clock reference signals, including frequency and phase references, to determine phase and time differences, generating control parameters to stabilize the oscillator, allowing for improved clock synchronization with reduced dependency on single accurate references and minimizing phase drift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single clock reference is used in conventional PLL circuits, then the circuit structure is simple, but the accuracy and stability of clock synchronization deteriorate when the reference is unstable or inaccurate
Solution Approach 1:
The patent combines multiple clock reference sources (GPS disciplined oscillator, atomic clock, and local crystal oscillator) into a unified PLL system. The phase comparator integrates phase difference signals from multiple references, and the loop filter processes combined error signals to generate a stable control voltage for the VCO, achieving improved reliability without excessive complexity increase
Solution Approach 2:
The PLL apparatus is designed to accept and process multiple types of clock references simultaneously. The phase comparator can handle phase difference signals from different reference sources, and the system can dynamically select or weight different references based on their availability and accuracy, providing universal adaptability to various timing sources
2Measurement precision
If GPS-based timing synchronization is used, then time reference accuracy can be improved, but the requirement for direct line of sight with multiple satellites increases processing time and causes phase drift
Solution Approach 1:
The system pre-processes GPS timing signals by extracting time-of-week information and comparing it with locally generated time references before full synchronization is achieved. The phase comparator continuously monitors phase differences and prepares correction signals in advance, reducing the time required for complete synchronization when GPS signals become available
Solution Approach 2:
The patent introduces a local crystal oscillator and phase comparator as intermediary elements between the GPS reference and the VCO. These intermediaries continuously track and correct phase differences in real-time, eliminating the need for lengthy processing periods and preventing phase drift that would occur with direct GPS-to-VCO synchronization
3Reliability
If multiple clock reference signals are integrated, then accuracy and stability of clock synchronization are enhanced, but the device complexity increases
Solution Approach 1:
The patent segments the multiple clock references into distinct functional groups: GPS disciplined oscillator for long-term stability, atomic clock for precision timing, and local crystal oscillator for immediate responsiveness. Each reference is processed through dedicated phase detection paths that feed into a common loop filter, organizing complexity into manageable segments while maintaining overall system accuracy
Solution Approach 2:
The system implements continuous feedback through the phase comparator and loop filter, which monitor phase differences from all clock references and dynamically adjust the VCO control voltage. This feedback mechanism automatically balances the contributions of multiple references, allowing the system to achieve high accuracy while managing complexity through intelligent signal integration and adaptive weighting
Data Source
AI summary
A phase-locked loop (PLL) apparatus and a method for clock synchronization are disclosed. According to an embodiment, the PLL apparatus includes an adjustable oscillator, one or more first difference determiners, one or more first parameter determiners and a loop integrator. The adjustable oscillator can generate an oscillating signal based on a control signal. Each first difference determiner can receive a first clock reference signal and determine a phase difference between the received first clock reference signal and the oscillating signal. Each first parameter determiner can receive a phase difference from the one or more first difference determiners and generate a first control parameter based on a variation of the phase difference. The loop integrator can integrate the one or more first control parameters to generate the control signal for the adjustable oscillator.