Temperature-Lookup Clock Synchronization for Timing Holdover
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Solution Overview
Problem
Current electronic timer systems face challenges in maintaining precise timing and synchronization, especially in packet-switched networks where delays and variations in packet delay times limit synchronization accuracy, and the use of highly stable oscillators is costly and impractical for small base stations.
Innovation Solution
A local clock system with a counter-based time generator and a translator that operates based on the relation tp=A⋅tr+B, where A and B are configurable parameters, allowing for cost-effective and power-efficient generation of precise time signals, even without continuous synchronization sources, using a temperature sensor and look-up table for frequency control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a highly stable oscillator (OCXO) is used to maintain timing accuracy during synchronization outages, then timing stability is improved, but cost increases significantly
Solution Approach 1:
The patent changes the operational parameters of a standard TCXO by using a look-up table to dynamically adjust the oscillator frequency based on temperature readings. This allows the system to achieve OCXO-level stability during synchronization outages without the high cost of an OCXO, by compensating for temperature drift through software-controlled frequency adjustments.
Solution Approach 2:
The patent introduces a look-up table as an intermediary between the temperature sensor and the oscillator control. This table stores pre-calculated frequency correction values that are applied based on measured temperature, enabling accurate temperature compensation without complex real-time calculations or expensive hardware.
2Ease of manufacture
If a temperature compensated crystal oscillator (TCXO) is used instead of OCXO, then cost is reduced, but timing stability during synchronization outages is insufficient
Solution Approach 1:
The patent implements a feedback mechanism where the temperature sensor continuously monitors oscillator temperature, the look-up table provides corresponding frequency correction values, and the oscillator frequency is adjusted accordingly. This closed-loop system enables a TCXO to achieve timing stability comparable to an OCXO during synchronization outages.
Solution Approach 2:
The patent performs preliminary action by pre-calculating and storing frequency correction values in the look-up table during system setup or calibration phases. This allows the system to quickly respond to temperature changes during operation without requiring complex real-time computations, thereby maintaining stability with a TCXO.
3Ease of manufacture
If packet switching is used for backhaul data traffic, then cost advantage is improved, but synchronization accuracy deteriorates due to variable packet delays
Solution Approach 1:
The patent prepares for potential synchronization disruptions by implementing a look-up table based compensation mechanism that can operate independently during packet delay variations or synchronization outages. This pre-prepared compensation system cushions against the harmful effects of packet switching variability, maintaining timing accuracy despite the use of cost-effective packet-switched backhaul.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables stable and accurate timekeeping in electronic timer systems, reducing power consumption and costs by allowing operation without high-frequency hardware and enabling precise timing in various applications, including telecommunications and industrial automation.
Implementation Method 1
A temperature sensor is placed in the vicinity of the oscillator or the crystal used by the oscillator
Implementation Method 2
The look-up control table is constructed from pairs of values of temperature and the parameter A sampled at suitable intervals during a table construction phase when the timer system is synchronized with a synchronization source
Implementation Method 3
The resonant frequency of a quartz crystal changes slowly with age, has some dependence on circuit component values and on driving strength and thus of the supply voltage of the oscillator, and, foremost, it is dependent on temperature
Data Source
AI summary
An electronic time or timer system comprises a counter-based time generator (10) for continuously generating raw base time, and a translator for translating between raw base time and local precise time. The counter-based time generator (10) is driven by an oscillator (200). The timer system further comprises a temperature sensor (300) placed in the proximity of the oscillator or a crystal used by the oscillator, and a look-up control table (400) holding temperature values associated with corresponding control values representative of the configurable parameter value A. The look-up control table is generated when the timer system is synchronized with a synchronization source so that the temperature and control values are characteristic of the operation of the timer system in synchronization. The timer system is also configured for reading, when no synchronization source is available, a temperature value from the temperature sensor (300), and for extracting, based on the temperature value, a control value from the look-up control table (400) corresponding to a suitable (quantized) representation of the temperature value. The timer system is then able to configure the parameter variable A in accordance with the extracted control value.