RTC Crystal Oscillator Temperature Compensation for Frequency Precision

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Solution Overview

Problem

Conventional real-time clocks using crystal oscillators face significant frequency precision errors due to temperature variations, which are inefficient to calibrate and costly to compensate for, especially in low-cost designs.

Innovation Solution

A method for temperature-dependent frequency compensation that determines general and specific frequency compensation values for crystal oscillators using sample oscillators, allowing for efficient calibration and adjustment of real-time clocks across multiple temperatures, reducing the need for extensive thermal equilibrium measurements and costly temperature-compensated crystal oscillators.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional crystal oscillators are used in real-time clocks, then the device cost is low, but the frequency precision error increases significantly with temperature variations

Engineering Contradiction:

Improvefrequency precisionVSAvoidtemperature-induced frequency error

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by pre-determining frequency compensation coefficients through measurements at four different temperatures during manufacturing. These coefficients are stored in memory and automatically applied during operation to compensate for temperature-induced frequency drift, eliminating the need for real-time complex measurements while maintaining high precision.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the operating parameters of the crystal oscillator by applying frequency compensation based on temperature. The system measures temperature, retrieves corresponding compensation coefficients from memory, and adjusts the oscillator frequency accordingly, transforming the oscillator from a temperature-sensitive component to a temperature-compensated precision frequency source.

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If frequency compensation coefficients are determined by measuring crystal oscillators at four different temperatures, then the frequency precision is improved, but the calibration time and process complexity increase

Engineering Contradiction:

Improvefrequency compensation accuracyVSAvoidcalibration time

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

The patent performs all necessary frequency measurements and compensation coefficient determinations during the manufacturing process. By completing the calibration work beforehand and storing the results in memory, the system eliminates time-consuming real-time measurements during operation, achieving both high precision and fast response.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses a simplified approach by measuring at exactly four strategically selected temperatures, which is sufficient to determine the cubic polynomial compensation coefficients. This partial measurement approach (rather than continuous measurement across all temperatures) achieves adequate precision while minimizing calibration time and complexity.

Inventive Principle:

Principle #16Partial or excessive action

3Manufacturing precision

If temperature-compensated crystal oscillators (TCXOs) are used, then the frequency precision error is reduced, but the device cost increases significantly

Engineering Contradiction:

Improvefrequency precisionVSAvoiddevice cost

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent creates a software-based model (copy) of the temperature-frequency relationship using compensation coefficients stored in memory. Instead of using expensive hardware TCXO circuits, the system uses a standard crystal oscillator with pre-determined compensation data, replicating the TCXO performance at a fraction of the cost.

Inventive Principle:

Principle #26Copying

Solution Approach 2:

The patent replaces expensive temperature-compensated crystal oscillators with inexpensive standard crystal oscillators combined with software-based compensation. The system uses cheap temperature sensors and memory storage instead of costly TCXO hardware, achieving cost-effective temperature compensation suitable for mass production in consumer electronics.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Data Source

PatentUS11012032B2Systems and methods for frequency compensation of real-time-clock systems

Publication Date: 2021.05.18 GUANGZHOU ON BRIGHT ELECTRONICS

AI summary

Method and system for temperature-dependent frequency compensation. For example, the method for temperature-dependent frequency compensation includes determining a first frequency compensation as a first function of temperature using one or more crystal oscillators, processing information associated with the first frequency compensation as the first function of temperature, and determining a second frequency compensation for a crystal oscillator as a second function of temperature based on at least information associated with the first frequency compensation as the first function of temperature. The one or more crystal oscillators do not include the crystal oscillator, and the first frequency compensation as the first function of temperature is different from the second frequency compensation as the second function of temperature.