RTC Crystal Oscillator Calibration Using Sample-Based Temperature Compensation

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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 various temperatures, reducing the need for extensive measurement and increasing precision.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

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:

Improvedevice costVSAvoidfrequency precision

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent applies parameter changes by measuring the crystal oscillator's frequency at multiple temperature points and using these measurements to calculate compensation coefficients. The system dynamically adjusts the frequency compensation based on temperature changes, transforming the static crystal oscillator into a temperature-compensated oscillator through software-based parameter adjustment rather than hardware modification.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses sample crystal oscillators to establish a frequency-temperature characteristic model that can be copied and applied to compensate other oscillators of the same type. By measuring a few sample oscillators at different temperatures and deriving compensation algorithms, the system creates a reusable compensation model that eliminates the need to physically adjust every individual oscillator, significantly reducing calibration time and cost.

Inventive Principle:

Principle #26Copying

2Measurement precision

If each crystal oscillator is measured at four different temperatures to determine compensation coefficients, then the frequency precision is improved, but the calibration process becomes inefficient and time-consuming

Engineering Contradiction:

Improvefrequency precisionVSAvoidcalibration efficiency

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent applies preliminary action by pre-measuring sample crystal oscillators to establish frequency-temperature characteristic models before actual deployment. These pre-obtained compensation coefficients and algorithms are stored and ready for use, eliminating the need to perform time-consuming four-temperature-point measurements for every individual oscillator during production or field calibration.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses the measurement results from a small number of sample oscillators to create compensation models that are then copied and applied to compensate a large number of oscillators. This approach allows the system to achieve high frequency precision for many oscillators by leveraging the calibration data from just a few samples, dramatically improving calibration efficiency.

Inventive Principle:

Principle #26Copying

3Measurement 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:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent replaces expensive hardware-based temperature-compensated crystal oscillators (TCXOs) with a software-based compensation approach using conventional, inexpensive crystal oscillators. By using algorithms to calculate and apply frequency compensation based on temperature measurements, the system achieves TCXO-level precision without the high hardware cost, effectively substituting a cheap software solution for an expensive hardware component.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent substitutes the mechanical/physical temperature compensation mechanism found in TCXOs (which require additional hardware components like varactors and control circuits) with a software-based digital compensation system. The system uses temperature sensor data and pre-calculated compensation coefficients to adjust the oscillator frequency through digital means, replacing complex hardware compensation mechanisms with simpler software processing.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS10734947B2Systems and methods for frequency compensation of real-time-clock systems

Publication Date: 2020.08.04 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.