Resonant MEMS Sensor Decoupling Structure for Mode Coupling Control
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Solution Overview
Problem
Resonant microelectromechanical sensors, particularly accelerometers, face issues with mode coupling due to the significant difference in resonant frequencies between nanoresonators and seismic masses, leading to loss of acceleration information and potential malfunction when spurious modes interact, limiting the dynamic range of measurable accelerations.
Innovation Solution
Incorporating a mechanical decoupling structure with a resonant frequency between the seismic mass and nanoresonator frequencies, acting as a low-pass filter to prevent high-frequency forces from activating spurious modes, ensuring the nanoresonator's frequency range does not cross seismic mass modes, thus maintaining sensor operation and expanding the dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the resonant frequency of the nanoresonator is in the order of several MHz to achieve high acceleration sensitivity, then the sensitivity is improved, but the resonant frequency crosses that of spurious modes of the seismic mass, leading to mode coupling and loss of acceleration information
Solution Approach 1:
A mechanical decoupling structure is introduced as an intermediary element between the seismic mass and the nanoresonator. This decoupling structure has a resonant frequency specifically designed to be between the seismic mass fundamental mode frequency and the nanoresonator operating frequency. The decoupling structure acts as a frequency filter that blocks the transmission of spurious high-frequency modes from the seismic mass to the nanoresonator, while allowing the low-frequency acceleration signal to pass through. This resolves the contradiction by enabling the nanoresonator to operate at high frequency for sensitivity while preventing mode coupling that would compromise reliability.
2Reliability
If the frequency range of the nanoresonator is limited to avoid crossing spurious modes, then mode coupling is avoided, but the range of measurable accelerations is limited, degrading the dynamic range of the sensor
Solution Approach 1:
The mechanical decoupling structure serves as a frequency-selective intermediary that resolves the contradiction between reliability and dynamic range. By positioning the decoupling structure's resonant frequency between the seismic mass spurious modes and the nanoresonator operating frequency, it creates a protective filter that blocks harmful high-frequency coupling while allowing the nanoresonator to sweep through its full frequency range for wide dynamic range acceleration measurement. This enables the sensor to maintain reliable operation across an extended measurement range.
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 mechanical decoupling structure effectively prevents mode coupling, maintaining sensor accuracy and expanding the range of measurable accelerations by filtering out high-frequency interference, thereby enhancing the sensor's dynamic range and reliability.
Implementation Method 1
The decoupling means have a low-pass filter function which allows transmission of low frequency forces in the order of one kHz or a few kHz from the proof body to the resonator and prevents transmission of high frequency forces in the order of one MHz or a few MHz from the resonator to the proof body
Implementation Method 2
at least one resonator arranged one with respect to the other so that displacement of the proof body causes a variation in the stress in the resonator
Data Source
AI summary
A resonant sensor including a support, a proof body suspended from the support and having a resonant frequency ωa, an element that measures a force including at least one resonator of resonant frequency ωrn, the force being applied by the proof body, and a mechanical decoupling structure interposed between the proof body and the resonator. The decoupling structure includes a decoupling mass, a first connecting element between the decoupling mass and the proof body, a second connecting element between the decoupling mass and the resonator, the decoupling structure having a main vibration mode whose resonant frequency ωd is such that ωa<ωd<ωrn, the decoupling structure forming a mechanical low-pass filter between the proof body and the resonator.