Reference Clock Resonator Arrays for Thermal Stability and Low Jitter
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Solution Overview
Problem
Existing clock generators face challenges in maintaining stable frequency, particularly with MEMS resonators, which have limited thermal stability and high jitter, and quartz resonators, which are limited by frequency range and fabrication constraints, making it difficult to achieve high-frequency reference clocks with low power consumption and minimal jitter.
Innovation Solution
An array of resonators with similar frequencies but varying turnover temperatures is used, along with a temperature sensor and switching circuitry to select the appropriate resonator based on temperature, ensuring high frequency stability and reduced jitter by dividing the temperature range into sections and optimizing each resonator for its corresponding range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If MEMS resonators are used for high-frequency reference clocks, then frequency range and power consumption are improved, but thermal stability and jitter performance deteriorate
Solution Approach 1:
The temperature range is divided into multiple sections, with each resonator optimized for a specific temperature section. The system segments the temperature compensation task across multiple resonators, each having different turnover temperatures, to achieve stable operation across the entire temperature range.
Solution Approach 2:
The invention changes the turnover temperature parameter of resonators to match different temperature sections. By adjusting the turnover temperature of each resonator, the system optimizes frequency stability for specific temperature ranges while maintaining high-frequency operation.
2Device complexity
If a single resonator is used for all temperature ranges, then device complexity is reduced, but frequency stability across temperature ranges deteriorates
Solution Approach 1:
The system dynamically switches between different resonators based on the detected temperature section. This dynamic adaptation allows the clock generator to maintain optimal frequency stability across varying temperature conditions by selecting the most appropriate resonator for the current temperature range.
Solution Approach 2:
A temperature sensor provides feedback about the current temperature, which the control circuit uses to determine the appropriate temperature section and select the corresponding resonator. This feedback mechanism ensures continuous optimization of frequency stability based on real-time temperature conditions.
3Stability of the object's composition
If resonators with different turnover temperatures are used for temperature compensation, then frequency stability is improved, but device complexity and switching requirements increase
Solution Approach 1:
The temperature range is segmented into discrete sections, with each section assigned to a specific resonator. This segmentation allows the use of relatively simple switching circuitry that only needs to select between a finite number of resonators based on temperature section, rather than requiring complex continuous adjustment mechanisms.
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 achieves frequency stability under 100 ppm and reduces jitter, enabling high-frequency reference clocks with faster start-up times and lower power consumption compared to traditional methods.
Implementation Method 1
A clock generator can include a quartz crystal resonator or a Microelectromechanical Systems (MEMS) resonator, for instance, which vibrates at a specific resonant frequency when excited by a signal from a driver
Implementation Method 2
A temperature sensor detects a temperature and provides an indication of the temperature to a control circuit
Data Source
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Figure 3A~3C
AI summary
Embodiments herein relate to a reference clock that includes an array of resonators with different turnover temperatures. The resonators may be Microelectromechanical Systems (MEMS) resonators with different doping concentrations, or quartz crystal resonators with different cut angles, for example. For MEMS resonators in particular, the turnover temperature can be adjusted by providing an overlying oxide layer with different thicknesses. In another approach, the resonators are piezoelectric-on-silicon resonators with different finger pitch-to-thickness ratios. A control circuit obtains a sensed temperature from a temperature sensor and selects one of the resonators having a turnover temperature in a temperature range corresponding to the sensed temperature. Each resonator may have a turnover temperature in a different temperature range. The resonators may have separate drivers or have a common driver.