Digitally Controlled Oscillator Feedback for Stable Clock Syntonization
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Solution Overview
Problem
Existing clock synchronization methods in computer networks, such as Synchronous Ethernet (SyncE) and Precision Time Protocol (PTP), face challenges in achieving accurate synchronization, particularly in maintaining low phase noise and good drift stability over time.
Innovation Solution
A system utilizing a digitally controlled oscillator (DCO) and clock synchronization circuitry to adjust the local clock frequency based on comparisons with a remote clock frequency, ensuring synchronization through digital control commands and firmware computations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Synchronous Ethernet (SyncE) is used to achieve syntonization, then clock frequency alignment is improved, but phase noise and drift stability deteriorate
Solution Approach 1:
The patent replaces traditional electronic oscillators with a digitally controlled oscillator (DCO) that uses digital feedback control to adjust frequency. The DCO is controlled by a feedback loop that monitors the difference between local and remote clock frequencies and dynamically adjusts the DCO's control voltage or digital control words to minimize frequency offset, thereby achieving both accurate syntonization and stable phase characteristics.
Solution Approach 2:
The patent implements a feedback mechanism where the system continuously monitors the remote clock frequency through received signals, compares it with the local clock frequency, and uses the frequency difference to generate correction signals. This feedback loop enables dynamic adjustment of the local oscillator frequency to maintain synchronization while compensating for drift and reducing phase noise accumulation.
2Measurement precision
If Precision Time Protocol (PTP) is used to align offset and phase, then time synchronization is improved, but frequency stability deteriorates
Solution Approach 1:
The patent combines the frequency alignment capability of SyncE with the time synchronization capability of PTP into a unified system. The DCO simultaneously performs both functions by using feedback control for frequency alignment while also providing accurate time stamping and offset measurement, thereby achieving both frequency stability and time synchronization without the trade-offs of using separate protocols.
Solution Approach 2:
The DCO system serves multiple functions: it provides frequency alignment through feedback control, generates accurate time stamps for synchronization, and maintains stable frequency output. This multi-functional approach eliminates the need to choose between SyncE and PTP, as the single system delivers both frequency stability and time synchronization accuracy.
3Device complexity
If traditional oscillators are used for clock generation, then device complexity is reduced, but synchronization accuracy deteriorates
Solution Approach 1:
The patent transitions from static oscillators with fixed frequencies to a dynamic DCO system that can adjust its frequency in real-time based on feedback from remote clock comparisons. The DCO's frequency is continuously modified through digital control words or analog control voltages, enabling adaptive synchronization while maintaining a relatively simple overall device structure.
Solution Approach 2:
The system changes the operating parameters of the oscillator by using a DCO that accepts digital control inputs. The control words or voltages modify the oscillator's frequency parameter dynamically, allowing precise frequency adjustment and synchronization without requiring complex hardware structures. The parameter changes are achieved through standard digital-to-analog conversion or direct digital synthesis techniques.
Data Source
AI summary
In one embodiment, a system includes a digitally controlled oscillator (DCO) to generate a local clock having a local clock frequency, and clock synchronization circuitry to receive from a device a signal indicative of a remote clock frequency, compare measures of the remote clock frequency and the local clock frequency; generate a digital control command based on the comparison; and provide the digital control command to the DCO, wherein the DCO is to adjust the local clock frequency responsively to the digital control command.