Hardware Clock Syntonization for Fast PTP Frequency Alignment
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Solution Overview
Problem
Existing software-based approaches for time synchronization in networks, such as IEEE 802.1 compliant techniques, face challenges with startup initialization delays, limited tracking rates, and software interrupts, especially when dealing with secondary clocks that have frequency drift due to less accurate crystal-based circuitry, leading to phase differences with primary clocks.
Innovation Solution
Hardware-based syntonization circuitry, including frequency error measurement and correction mechanisms, alleviates computational burdens on CPUs by using ASIC or FPGA to synchronize secondary clocks with high-precision reference clocks, enabling frequency alignment and reducing clock drift through hardware logic circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If software-based approaches (IEEE 802.1) are used for time synchronization, then implementation flexibility is improved, but startup initialization delays and processing time increase
Solution Approach 1:
The patent replaces software-based synchronization mechanisms with hardware-based circuitry (phase-locked loops, frequency synthesizers, timing circuits) that operate at the electrical/circuit level. This substitution eliminates software initialization overhead and enables immediate clock synchronization upon system startup, resolving the contradiction between implementation flexibility and startup time.
2Ease of operation
If software-based approaches are used, then ease of programming is improved, but tracking rates and response speed are limited
Solution Approach 1:
The patent replaces software processing with hardware circuitry including phase-locked loops and frequency synthesizers that naturally operate at high speeds. These analog/digital circuits provide deterministic tracking rates in the nanosecond range, eliminating the processing bottlenecks inherent in software-based approaches while maintaining configurability through hardware design.
3Ease of manufacture
If secondary clocks with crystal-based circuitry are used, then cost is reduced, but frequency drift and phase differences with primary clocks increase
Solution Approach 1:
The patent implements phase-locked loop (PLL) circuits that continuously monitor the frequency and phase of secondary clocks and provide feedback control. The PLL adjusts the secondary clock frequency in real-time to match the primary reference clock, compensating for crystal drift while maintaining the cost benefits of using inexpensive crystal oscillators instead of expensive atomic clocks.
Solution Approach 2:
The patent performs preliminary frequency calibration and phase alignment during system initialization using hardware timing circuits. This pre-synchronization establishes accurate phase relationships before operational loads are applied, preventing cumulative drift and reducing the need for frequent corrections during normal operation.
4Measurement precision
If hardware-based syntonization circuitry is used, then frequency alignment precision is improved, but device complexity increases
Solution Approach 1:
The patent integrates multiple timing functions (clock generation, frequency synthesis, phase measurement, synchronization control) into a single unified hardware timing module. This multi-functional design achieves high frequency alignment precision through integrated phase-locked loops and frequency synthesizers while reducing overall device complexity by eliminating the need for separate discrete timing circuits.
Data Source
AI summary
Apparatus are disclosed to syntonize timing devices. An example apparatus includes activity detection circuitry to generate a pulse output based on a first clock and a second clock, the pulse output having a periodicity of the first clock, phase error generation circuitry to determine phase error direction indicators between the pulse output and a regenerated clock, the regenerated clock having a first frequency, proportional/integral (PI) circuitry to determine correction values based on the phase error direction indicators, the correction values to cause modification of the first frequency of the regenerated clock, and precision time protocol (PTP) timer circuitry to modify a frequency of a third clock based on accumulated ones of the correction values.