Networked Frequency Reference Distribution Using IEEE 1588
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Solution Overview
Problem
In complex test and measurement environments, achieving accurate frequency reference distribution among multiple instruments is challenging due to internal oscillator differences and drifting frequencies, leading to issues of accuracy and increased costs with traditional solutions like precision timebases and common oscillator approaches.
Innovation Solution
Utilizing the IEEE 1588 standard for precision clock synchronization over computer networks, specifically Ethernet, to synchronize instruments with a common time source, allowing for precise time and interval data exchange to adjust and correct oscillator frequencies, thereby maintaining accurate frequency references across instruments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If precision timebases (double-oven temperature controlled crystal oscillators) are used in each instrument, then frequency accuracy and stability are greatly increased, but instrument price, weight, heat generation, and power consumption increase significantly
Solution Approach 1:
The patent merges the timebase functions of multiple instruments by having them share a common reference oscillator through network synchronization. Instead of each instrument having its own precision timebase, the system combines the timing reference function into a shared resource that all instruments can access via IEEE 1588 protocol over the network, thereby reducing total power consumption while maintaining frequency accuracy.
Solution Approach 2:
The patent introduces an intermediary mechanism - the IEEE 1588 network synchronization protocol - that mediates between the reference oscillator and individual instrument oscillators. This intermediary allows frequency reference distribution without requiring direct physical connections or duplicate precision timebases in each instrument, reducing power consumption while maintaining synchronization accuracy.
2Measurement precision
If a common oscillator reference is distributed to each instrument through additional cabling, then frequency reference accuracy is improved, but device complexity and cost increase due to additional connectors and cables
Solution Approach 1:
The patent replaces the mechanical/electrical cabling system with a digital network communication system. Instead of using physical BNC connectors and coaxial cables to distribute the reference signal, the system uses IEEE 1588 protocol over standard Ethernet network infrastructure, eliminating the need for additional dedicated reference cabling while maintaining frequency reference accuracy.
Solution Approach 2:
The patent makes the existing network infrastructure multi-functional by using it both for data communication and for frequency reference distribution. The same Ethernet network cables that carry data traffic also carry the IEEE 1588 synchronization messages, eliminating the need for separate dedicated reference cabling and reducing overall system complexity.
3Measurement precision
If instruments are synchronized through a master instrument with upgraded timebase, then frequency accuracy is improved, but the master instrument becomes a single point of failure and system complexity increases
Solution Approach 1:
The patent segments the timebase function across multiple independent instruments rather than concentrating it in a single master instrument. Each instrument maintains its own oscillator and can independently receive IEEE 1588 synchronization messages from any available reference source, eliminating the single point of failure problem while maintaining frequency accuracy through distributed synchronization.
Data Source
AI summary
A correction processor connected to an oscillator uses precision timing signals propagated over a digital network to generate an error signal. IEEE-1588 time synchronization protocols produce precision time signals which are converted to precision interval signals. The correction processor uses the precision interval signals to count pulses of the oscillator. A correction circuit compares the counter output with a predetermined value and generates an error signal may be used to correct the oscillator or may be propagated to consumers of the oscillator. An arbitrary reference oscillator may be used to generate the precision timing signals propagated on the network, to slave other oscillators to it. The precision of the reference oscillator may be deliberately overstated to insure it is used as a master.