Dual-MEMS Frequency Reference Oscillator With Thermal Stabilization
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Solution Overview
Problem
Existing frequency reference oscillators based on MEMS resonators face challenges in achieving stable and temperature-insensitive output frequencies with low phase noise and high long-term stability, as they are prone to significant temperature drift and variability, making them less suitable for replacing quartz oscillators.
Innovation Solution
A frequency reference oscillator design utilizing two MEMS resonators with different long-term stability characteristics, where a first resonator with high stability is used to thermally stabilize a second resonator, employing a thermostatic controller and stability control circuit to maintain a temperature-insensitive output frequency without relying on frequency measurements, allowing for independent thermostatic control and reduced power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a MEMS resonator is operated at elevated temperature to improve frequency stability, then temperature drift is reduced, but power consumption increases
Solution Approach 1:
The system divides the frequency reference function into two separate MEMS resonators: a first resonator operated at elevated temperature for stability, and a second resonator operated at lower temperature for power efficiency. The resonant frequencies of both resonators are combined through frequency addition to produce the final output, thereby segmenting the thermal burden and reducing overall power consumption while maintaining frequency stability.
Solution Approach 2:
The system operates the first MEMS resonator at an elevated temperature (e.g., 85°C or higher) to achieve maximum frequency stability and minimum temperature drift, while the second resonator operates at a lower temperature. This parameter differentiation allows the system to optimize stability for the first resonator while conserving power with the second resonator, with the combined frequency output reflecting both operational states.
2Stability of the object's composition
If a single high-stability MEMS resonator is used, then frequency stability improves, but device complexity increases
Solution Approach 1:
The system merges the resonant frequencies of two MEMS resonators through frequency addition to produce the final output frequency. By combining the stable frequency reference from the first resonator (operated at elevated temperature) with the second resonator's frequency, the system achieves high frequency stability without requiring a single complex high-stability resonator, thereby simplifying the overall device architecture.
Solution Approach 2:
Both MEMS resonators serve multiple functions: the first resonator provides temperature-stable frequency reference while also contributing to the final output frequency, and the second resonator provides both frequency contribution and temperature compensation. This multi-functionality reduces the need for separate compensation circuits and simplifies the overall oscillator structure.
3Measurement precision
If frequency measurements are used for temperature compensation, then frequency accuracy improves, but measurement precision requirements increase
Solution Approach 1:
The system uses the second MEMS resonator as a thermal copy or proxy for the first resonator, both experiencing similar temperature conditions. By measuring the frequency of the second resonator (which operates at lower temperature and has good stability characteristics) and using it to infer temperature effects on the first resonator, the system achieves temperature compensation without requiring high-precision frequency measurements of the elevated-temperature resonator, thereby reducing measurement precision requirements and control circuit complexity.
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 design achieves long-term stability of less than 1 ppm/year and retrace performance of 20 ppb or less, comparable to quartz crystals, with improved temperature stability and reduced power consumption, making it suitable for replacing quartz oscillators.
Implementation Method 1
a first oscillator comprising a first resonator having first long-term stability and a first frequency-vs-temperature turnover temperature, the first oscillator being capable of providing a first frequency signal
Implementation Method 2
a thermostatic controller for adjusting the temperature of the first resonator essentially to said turnover temperature and the second resonator essentially to said second turnover temperature
Implementation Method 3
a stability control circuit configured to use the first frequency signal for adjusting the second oscillator for providing a temperature stabilized and long-term stabilized output frequency signal
Data Source
AI summary
A frequency reference oscillator device and method of providing a frequency reference signal. The oscillator device includes a first oscillator including a first resonator having first long-term stability and a first frequency-vs-temperature turnover temperature, the first oscillator being capable of providing a first frequency signal. Further, the device includes and a second oscillator including a second resonator having second long-term stability, which is inferior to the first long-term stability, and a second frequency-vs-temperature turnover temperature, the second oscillator being capable of providing a second frequency signal. There is also provided a thermostatic controller for adjusting the temperature of the first resonator essentially to said first turnover temperature and the temperature of the second resonator essentially to said second turnover temperature, and a stability control circuit configured to use the first frequency signal for adjusting the second oscillator for providing a temperature stabilized and long-term stabilized output frequency signal.