Quartz Oscillator Temperature Compensation Using Frequency Difference
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Solution Overview
Problem
Existing oscillation devices, such as TCXO, face challenges in achieving high frequency stability due to large memory requirements for temperature compensation data and limited detection accuracy, which complicates the manufacturing process and reduces yield.
Innovation Solution
The oscillation device employs two quartz-crystal oscillators thermally coupled on a common quartz-crystal piece, with a frequency difference detecting unit and a compensation value obtaining unit that calculates frequency compensation using an nth-order polynomial, reducing memory capacity and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large-capacity memory is used to store frequency-temperature characteristic data for fine temperature compensation, then frequency accuracy is improved, but device cost increases
Solution Approach 1:
The patent divides the temperature compensation function into two parts: a first quartz-crystal oscillator for main operation and a second quartz-crystal oscillator specifically for temperature detection. This segmentation allows the temperature detection oscillator to use a simple lookup table in memory while the main oscillator receives compensated frequency signals, resolving the contradiction between memory capacity and frequency accuracy.
Solution Approach 2:
The patent introduces a frequency difference detecting unit that measures the frequency difference between the first and second oscillators as an intermediary step. This intermediary measurement allows the system to determine temperature-induced frequency deviations without requiring the main oscillator's control circuit to directly process large amounts of temperature compensation data, reducing memory requirements while maintaining accuracy.
2Device complexity
If a thermistor is used as the temperature detector, then device structure is simplified, but detection accuracy is limited
Solution Approach 1:
The patent makes the second quartz-crystal oscillator serve dual purposes: it oscillates to generate a frequency signal for the main system while simultaneously acting as a temperature sensor. The oscillator's frequency naturally varies with temperature according to its characteristic curve, providing accurate temperature detection without requiring external temperature sensors like thermistors, thus maintaining structural simplicity while improving detection accuracy.
3Ease of operation
If the temperature detector and quartz-crystal oscillator are disposed at different positions, then device layout is flexible, but temperature measurement accuracy deteriorates
Solution Approach 1:
The patent merges the temperature detection function directly into the quartz-crystal oscillator structure by providing a second pair of electrodes on the same quartz-crystal piece. This integration ensures that the temperature detector (second oscillator) and the measured object (first oscillator) are at the same position, accurately reflecting the actual temperature of the crystal while maintaining layout flexibility through the electrode configuration.
4Measurement precision
If two quartz-crystal oscillators are adjusted to satisfy f0≈f1≈f2, then frequency accuracy is improved, but manufacturing process becomes complicated
Solution Approach 1:
The patent changes the approach from adjusting oscillators to satisfy f0≈f1≈f2 to using the inherent frequency difference between oscillators as a useful parameter. The frequency difference detecting unit measures the natural frequency difference caused by temperature, and the control circuit uses this difference to calculate compensation values. This parameter change eliminates complex adjustment processes while maintaining frequency accuracy through mathematical compensation.
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 stabilizes the output frequency across temperature variations, reducing memory requirements and enhancing frequency accuracy while simplifying the manufacturing process.
Implementation Method 1
a first quartz-crystal oscillator, structured by providing first electrodes on a quartz-crystal piece; a second quartz-crystal oscillator, structured by providing second electrodes on a quartz-crystal piece
Implementation Method 2
quartz-crystal oscillator
Data Source
AI summary
An oscillation device for reducing memory capacity includes a frequency difference detecting unit and a compensation value obtaining unit. When oscillation frequencies of the first and second oscillation circuits are respectively f1 and f2, and oscillation frequencies of the first and second oscillation circuits at a reference temperature are respectively f1r and f2r, the frequency difference detecting unit determines a difference corresponding value x 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. The compensation value obtaining unit obtains a frequency compensation value of f1 resulting from ambient temperature different from reference temperature based on the difference corresponding value x, and calculates the frequency compensation value of f1 by calculating nth-order polynomial for X being a value corresponding to x/k, where k is a divide coefficient specific to a device.