Dual-Mode MEMS Resonator for Temperature-Stable Frequency Output
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Solution Overview
Problem
Conventional MEMS resonators face challenges due to frequency deviations caused by temperature variations, particularly because silicon resonators have a highly negative temperature coefficient of elasticity, leading to strong correlation of resonant frequency with temperature.
Innovation Solution
A dual-mode MEMS resonator capable of operating in both in-plane and out-of-plane modes of vibration, allowing for the generation of two different frequencies from a single package. This resonator can selectively output one or both frequencies and is equipped with circuitry to determine temperature based on the concurrently outputted frequencies, eliminating the need for external temperature sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external temperature sensors and compensation circuitry are added to measure and compensate for temperature, then temperature compensation accuracy is improved, but device complexity and power consumption increase
Solution Approach 1:
The resonator uses its own dual-mode vibration frequencies to determine temperature, eliminating the need for external temperature sensors. The system self-measures temperature by comparing the frequencies of in-plane and out-of-plane modes, which have different temperature coefficients, thereby reducing device complexity and power consumption while maintaining accurate temperature measurement.
Solution Approach 2:
The resonator structure serves multiple functions: it generates timing frequencies and simultaneously measures temperature. By operating in two vibration modes with different temperature dependencies, the same device structure provides both timing reference and temperature sensing capabilities, reducing the need for separate components.
2Measurement precision
If external temperature sensors and compensation circuitry are added to measure and compensate for temperature, then temperature compensation accuracy is improved, but power consumption increases
Solution Approach 1:
The resonator uses its own dual-mode vibration frequencies to determine temperature, eliminating the need for external temperature sensors. The system self-measures temperature by comparing the frequencies of in-plane and out-of-plane modes, which have different temperature coefficients, thereby reducing device complexity and power consumption while maintaining accurate temperature measurement.
3Area of stationary object
If a single resonator operates in multiple vibration modes to provide different frequencies, then space requirements are reduced, but frequency stability may be affected by mode coupling
Solution Approach 1:
The resonator is designed with distinct in-plane and out-of-plane vibration modes that are spatially and mechanically segmented. The in-plane modes involve lateral vibrations while out-of-plane modes involve vertical vibrations, creating natural separation that minimizes mode coupling and maintains frequency stability while providing multiple frequencies from a single device.
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 dual-mode MEMS resonator provides more accurate temperature measurements and stable frequency output, reducing power consumption and space requirements while offering improved performance compared to conventional systems.
Implementation Method 1
operating the MEMS resonator in an in-plane mode of vibration using a first oscillator, thereby obtaining a first electrical signal having a first frequency. The method comprises concurrently operating the MEMS resonator in an out-of-plane mode of vibration
Implementation Method 2
obtaining a first electrical signal having a first frequency. The method comprises concurrently operating the MEMS resonator in an out-of-plane mode of vibration using a second oscillator, thereby obtaining a second electrical signal having a second frequency
Implementation Method 3
mixing the first and second electrical signals together, thereby obtaining a third electrical signal having a third frequency, the third frequency being proportional to a temperature of the MEMS resonator
Data Source
AI summary
An example resonating structure comprises a substrate, a resonator body, and an anchoring body for anchoring the resonator body to the substrate. The resonator body is doped with a dopant having a concentration chosen so as to minimize a second order temperature coefficient of frequency for the resonator body. The resonator body is operable in an in-plane mode of vibration and an out-of-plane mode of vibration.