MEMS Resonator Oscillator Circuit for Temperature-Stable Frequency
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Solution Overview
Problem
Microelectromechanical resonators experience significant frequency drift due to temperature-induced changes in Young's modulus, making it challenging to maintain stable resonance frequencies over varying operating temperatures.
Innovation Solution
The implementation of an oscillator system comprising two microelectromechanical resonators with different temperature-dependent frequency responses, where the frequency manipulation circuitry, including digital or analog components, subtracts or mixes the output signals to generate a third signal that is substantially stable over a predetermined temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single microelectromechanical resonator is used, then the device structure is simple, but the frequency stability over temperature is poor
Solution Approach 1:
The system divides the frequency reference function into multiple segments by using two separate resonators with different temperature coefficients. Each resonator handles a portion of the temperature compensation range, and their outputs are combined through frequency manipulation circuitry to achieve overall frequency stability across the full temperature range.
Solution Approach 2:
The system creates a composite frequency reference by combining outputs from two resonators made of different materials or structures (first resonator with first temperature coefficient, second resonator with second temperature coefficient). This composite approach leverages the complementary temperature responses to cancel out frequency drift.
2Reliability
If multiple microelectromechanical resonators with different temperature responses are used, then frequency stability over temperature is improved, but the device complexity increases
Solution Approach 1:
The patent replaces complex mechanical temperature compensation mechanisms with an electronic frequency manipulation system. Instead of physically adjusting the resonators to compensate for temperature, the system uses frequency mixing and mathematical combination of signals from multiple resonators to achieve compensation, substituting mechanical adjustment with electronic signal processing.
Solution Approach 2:
The system changes the operational parameters of the resonators by operating them at different frequencies and combining their outputs through frequency manipulation. The frequency ratio between the two resonators is specifically selected to achieve temperature compensation, transforming the problem from mechanical adjustment to parameter optimization.
3Reliability
If frequency manipulation circuitry is added to combine resonator outputs, then temperature compensation is achieved, but the circuit complexity increases
Solution Approach 1:
The frequency manipulation circuitry acts as an intermediary system that receives signals from the resonators and produces the compensated output. This intermediary layer handles the complexity of temperature compensation by performing frequency mixing and signal combination, isolating the resonators from direct temperature sensitivity while providing a stable frequency reference to the output.
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 effectively compensates for temperature-induced frequency shifts, providing a stable output signal by canceling or offsetting temperature-dependent terms, thereby maintaining consistent resonance frequencies across a range of operating temperatures.
Implementation Method 1
a first microelectromechanical resonator to generate a first output signal having a frequency that varies with operating temperature, wherein the first microelectromechanical resonator includes a frequency function of temperature
Implementation Method 2
frequency manipulation circuitry, coupled to the first and second microelectromechanical resonators to generate a third signal having frequency that is substantially stable over a predetermined operating temperature using the first and second output signals
Data Source
AI summary
There are many inventions described and illustrated herein. In one aspect, the present inventions relate to oscillator systems which employ a plurality of microelectromechanical resonating structures, and methods to control and/or operate same. The oscillator systems are configured to provide and/or generate one or more output signals having a predetermined frequency over temperature, for example, (1) an output signal having a substantially stable frequency over a given/predetermined range of operating temperatures, (2) an output signal having a frequency that is dependent on the operating temperature from which the operating temperature may be determined (for example, an estimated operating temperature based on a empirical data and/or a mathematical relationship), and/or (3) an output signal that is relatively stable over a range of temperatures (for example, a predetermined operating temperature range) and is “shaped” to have a desired turn-over frequency.