Dual-Oscillator Clock Circuit for Temperature-Stable MEMS Timing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
MEMS resonators face challenges in temperature stability and initial accuracy, with uncompensated MEMS resonators having a high temperature coefficient compared to quartz oscillators, and conventional methods like electrostatic pulling are ineffective for high-frequency MEMS oscillators.
Innovation Solution
A frequency-control circuit that alters pulses of an input signal to tune the output frequency, using techniques such as pulse removal, addition, or switching between oscillators, coupled with a temperature sensor for dynamic stabilization, allowing for precise and temperature-stable clock generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional electrostatic pulling is used to tune MEMS oscillators, then frequency adjustment is possible, but it is ineffective for high-frequency MEMS oscillators due to very high equivalent stiffness
Solution Approach 1:
The patent replaces the mechanical electrostatic pulling method with a signal processing approach using a frequency control circuit. Instead of physically adjusting the resonator frequency through electrostatic forces, the system uses pulse alteration (removal or addition) in the output signal to achieve effective frequency tuning. This substitution bypasses the mechanical limitation of high stiffness in high-frequency MEMS oscillators.
2Device complexity
If uncompensated MEMS resonators are used, then device complexity is reduced, but temperature stability deteriorates with a temperature coefficient of approximately 40 ppm/°C
Solution Approach 1:
The patent implements a feedback mechanism where a temperature sensor monitors the temperature of the MEMS resonator and provides this information to the frequency control circuit. The circuit then dynamically adjusts the pulse alteration amount based on the temperature reading, creating a closed-loop system that compensates for temperature-induced frequency drift and maintains stable operation across varying temperatures.
3Stability of the object's composition
If quartz oscillators are used instead of MEMS oscillators, then temperature stability is improved to approximately 0.035 ppm/°C, but cost and availability increase
Solution Approach 1:
The patent changes the operational parameters of the MEMS oscillator by dynamically altering the number of pulses in the output signal based on temperature measurements. This parameter change approach allows the MEMS device to achieve temperature stability comparable to quartz oscillators without requiring the more expensive quartz material, thereby maintaining ease of manufacture and availability while improving performance.
4Measurement precision
If pulse skipping is used to adjust clock frequency, then frequency synchronization is achieved, but initial accuracy and temperature stability are not effectively improved
Solution Approach 1:
The patent applies pulse skipping as a preliminary frequency adjustment mechanism to bring the oscillator close to the target frequency, then uses temperature-compensated pulse alteration as a fine-tuning mechanism to achieve precise initial accuracy and temperature stability. This two-stage approach combines the benefits of frequency synchronization with improved precision, addressing both aspects of the contradiction.
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-precision, temperature-stable clock signals with improved accuracy and reduced spurious signals, suitable for various applications without the need for expensive quartz-based resonators, while maintaining performance comparable to quartz-based oscillators.
Implementation Method 1
a frequency-control circuit that is configured to receive a first signal having a first untuned frequency from a first oscillator, and to alter one or more pulses of the first signal to tune an output frequency of an output clock signal to have an average frequency at a desired target frequency
Implementation Method 2
coupled with a temperature sensor for dynamic stabilization
Implementation Method 3
MEMS resonators having a first resonant frequency
Data Source
AI summary
A frequency-control circuit, which is configured to receive a first signal having a first untuned frequency from a first oscillator, and to alter one or more pulses of the first signal to tune an output frequency of an output clock signal to have an average frequency at the desired target frequency. In some embodiments, the two oscillators of intentionally different frequencies are periodically switched at a duty factor, which is dependent on an absolute temperature, to generate a calibrated, precise, and temperature-stable clock.