Crystal Resonator Frequency Correction for Temperature and Stress Drift
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current mechanical resonators in electronic oscillators face limitations in short-term frequency stability due to temperature changes and mechanical stress, with existing methods being either costly, power-consuming, or requiring factory calibration and pairing with electronics.
Innovation Solution
A system and method that uses state space description to determine and correct for changes in mass, stiffness, and dimensions of the crystal resonator, allowing for indirect measurement of these variables through electrical parameters and resonance frequencies, enabling improved frequency stability by populating a table of frequency correction factors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If temperature compensation methods (TCXO/MCXO) are used to improve short-term frequency stability, then frequency stability improves, but device complexity and cost increase due to temperature sensors, calibration procedures, and microprocessor-controlled frequency synthesizers
Solution Approach 1:
The patent extracts the temperature sensing function from a separate temperature sensor and integrates it into the crystal resonator itself by utilizing the crystal's inherent temperature-dependent frequency characteristics. The measurement of resonance frequencies at different overtones serves as the temperature indicator, eliminating the need for external temperature sensors and reducing device complexity while maintaining frequency stability compensation capabilities
Solution Approach 2:
The crystal resonator is given multiple functions: it serves both as the frequency reference element and as the temperature sensor. By measuring the frequency ratio between fundamental and overtone modes, the system simultaneously obtains both the reference frequency and the temperature information needed for compensation, reducing the overall component count and system complexity
2Reliability
If ovenized crystal oscillators (OCXO) are used to improve frequency stability, then frequency stability improves, but power consumption, size, and cost increase
Solution Approach 1:
The patent changes the operating parameters by using the natural frequency-temperature relationship of the crystal without requiring thermal isolation. Instead of maintaining a constant high temperature through power-consuming heating, the system allows the crystal to operate at ambient temperature and uses electrical measurement of frequency ratios to detect and compensate for temperature variations, dramatically reducing power consumption
3Reliability
If temperature sensors and calibration procedures are used to improve frequency stability, then frequency stability improves, but manufacturing complexity and cost increase due to pairing requirements
Solution Approach 1:
The crystal resonator performs self-measurement of its temperature state through its inherent frequency characteristics. The system uses the crystal's own resonance frequencies at different overtones to determine temperature and automatically applies compensation, eliminating the need for external sensors, calibration procedures, and factory pairing processes
4Reliability
If dual-mode oscillators with beat frequency measurement are used to improve temperature compensation, then frequency stability improves, but retrace errors occur due to mechanical stress sensitivity
Solution Approach 1:
The patent applies local quality by selecting specific overtone modes (odd overtones) that have different sensitivity characteristics to temperature and mechanical stress. By measuring the frequency ratio between the fundamental mode and a specific overtone mode, the system can distinguish temperature effects from stress effects, as the two factors affect different modes differently, thereby reducing retrace errors
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 approach enhances short-term frequency stability by accurately compensating for temperature drift and mechanical stress without the need for direct measurement, reducing retrace errors and operational costs, while maintaining long-term stability through advanced packaging techniques.
Implementation Method 1
The at least two independent electrically measurable parameters are selected from the group consisting of a ratio of a resonance frequency of the crystal with respect to another resonance frequency of the crystal, a power loss in the crystal resonator at one or more of its resonance frequencies, and a quality factor of the crystal resonator at one or more of its resonance frequencies
Implementation Method 2
Measuring a resonance mode frequency of a crystal with respect to a known reference signal frequency
Data Source
Figure 1
AI summary
The invention relates to a method for operating a mechanical resonator in an electronic oscillator, comprising determining a state space description of the resonator, in which state variables are the mass, the stiffness or dimensions of components used in the crystal resonator; providing a table with frequency correction factors as a function of a state space of a resonator; finding a frequency correction factor corresponding to the determined state space; and multiplying the output frequency of the resonator with the correction factor, and to an electronic oscillator, comprising a mechanical resonator, wherein an output frequency of the oscillator is multiplied by a frequency correction factor, the frequency correction factor being obtained from determination of the state variables of the resonator, in particular dominant mechanical state variables.