Dual-Crystal Oscillator Frequency Difference Temperature Compensation
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Solution Overview
Problem
Temperature-controlled crystal oscillators (TCXOs) face challenges in achieving high frequency stability due to lower frequency stability against temperature changes compared to oven-controlled crystal oscillators (OCXOs), requiring large-capacity memory for accurate temperature correction and suffering from limited detection accuracy of temperature detectors, which complicates manufacturing and reduces product yield.
Innovation Solution
An oscillator device utilizing two crystal units with shared electrodes, a frequency difference detection unit, and correction value acquisition units to calculate frequency correction values using approximation formulas, reducing errors and improving temperature compensation accuracy by treating the frequency difference between the two crystal units as instantaneous temperature data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If a temperature-controlled crystal oscillator (TCXO) is used to achieve lower power consumption and simpler structure compared to OCXO, then power consumption and structure are improved, but frequency stability against temperature changes deteriorates
Solution Approach 1:
The patent introduces a frequency difference detection unit that measures the frequency difference between two crystal units as an intermediary parameter to represent temperature. This frequency difference serves as a mediator that translates temperature information into a measurable electrical signal without requiring direct temperature sensing, enabling temperature compensation in TCXO while maintaining its low power consumption advantage.
Solution Approach 2:
The patent replaces the traditional temperature detector (thermistor) with a frequency difference detection mechanism. Instead of mechanically/thermally sensing temperature and converting it to electrical signals, the system uses the inherent frequency-temperature characteristic of crystal oscillators to directly obtain temperature information through frequency measurement, eliminating the need for separate temperature sensing components.
2Measurement precision
If a large-capacity memory is used to store frequency temperature characteristic data for accurate temperature correction, then temperature correction accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts only the essential temperature information needed for compensation by using the frequency difference between two crystal units as a direct temperature indicator. This eliminates the need to store and process large amounts of frequency-temperature characteristic data in memory, as the system only needs to measure the frequency difference and apply a simple correction based on this single parameter.
Solution Approach 2:
Instead of storing temperature-to-frequency-correction data in memory and looking it up, the patent inverts the approach by using the frequency difference itself as the temperature indicator. The system measures the frequency difference and uses it directly to determine the correction amount, eliminating the need for large memory storage and complex data lookup operations.
3Ease of operation
If a thermistor is used as the temperature detector to obtain temperature information, then temperature detection is simplified, but detection accuracy is limited and cannot be improved by increasing data amount
Solution Approach 1:
The patent replaces the thermistor-based temperature detection system with a frequency difference detection system. Instead of using a thermistor to convert temperature changes into resistance changes and then into voltage signals, the system uses the frequency-temperature characteristic of crystal oscillators to directly convert temperature information into frequency differences, which can be measured with much higher precision using standard digital counters.
4Measurement precision
If two crystal units are provided with different arrangement positions to measure temperature, then temperature measurement capability is gained, but manufacturing complexity increases and product yield decreases
Solution Approach 1:
The patent merges the temperature sensing function with the frequency generation function by using two crystal units that are both oscillators and temperature sensors. The frequency difference detection unit combines the outputs of both crystal units to extract temperature information, eliminating the need for separate temperature sensing components and simplifying the manufacturing process.
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
The solution enables high-accuracy temperature compensation of output frequency, improving stability and reducing errors in frequency correction, while simplifying the manufacturing process and increasing product yield without the need for complex adjustments or large memory capacity.
Implementation Method 1
a first crystal unit (10) and a second crystal unit (20) are provided. Each of the first and second crystal units (10, 20) includes a crystal element (Xb) and a pair of electrodes (11, 12 and 21, 22).
Implementation Method 2
a frequency difference detection unit (3) is provided. The frequency difference detection unit (3) obtains frequency difference information corresponding to a difference value between a value corresponding to a difference between f1 and f1r and a value corresponding to a difference between f2 and f2r
Data Source
AI summary
A value corresponding to a difference value between a value corresponding to a difference between f1 and f1r and a value corresponding to a difference between f2 and f2r is treated as an instantaneous temperature, where f1 and f2 denote oscillation outputs of the first and second oscillation circuits, respectively, and f1r and f2r denote oscillation frequencies of the first and second oscillation circuits, respectively, at a reference temperature. A first correction value is obtained using an approximation formula of the frequency correction value of f1 based on the value corresponding to the difference value, and a second correction value for canceling a correction residual error is obtained from the correction residual error which is a difference between the first correction value and the frequency correction value actually measured. The frequency correction value is obtained from a sum of the first and second correction values.