MEMS Accelerometer Capacitor Merging for Compact Three-Axis Sensing
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Solution Overview
Problem
Conventional micro-electromechanical system (MEMS) sensors require a large number of wires to route signals from the accelerometer structure to the sensing circuit, leading to a large device size and high cost, while also being inefficient in measuring forces along multiple axes.
Innovation Solution
The design combines capacitors to measure acceleration or force along two perpendicular axes parallel to a substrate face, allowing for a compact MEMS sensor device with increased sensitivity by reusing capacitors and implementing differential logic for multiple axes sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If twelve wires are used to route signals from the accelerometer structure to the sensing circuit, then three-axis acceleration measurement is achieved, but the device size becomes too large and cost increases
Solution Approach 1:
The patent combines capacitors to measure acceleration along multiple axes simultaneously. Specifically, capacitors are configured such that the same capacitor structure can sense acceleration in different directions by utilizing differential capacitance changes, thereby reducing the number of separate sensing elements and associated wiring required for three-axis measurement.
Solution Approach 2:
The patent implements multi-functionality by designing capacitors that can serve multiple sensing purposes. The same capacitor structure is used to detect acceleration along different axes by applying different excitation voltages and measuring differential capacitance changes, allowing a single capacitor to perform what would traditionally require multiple separate sensors.
2Reliability
If twelve wires are routed for differential input and output signals, then complete signal routing is achieved, but wire complexity and device area increase
Solution Approach 1:
The patent merges signal routing paths by using common electrodes and shared capacitive structures for multiple measurement axes. By combining the sensing function across different axes into shared capacitor elements, the number of separate signal paths and wires is reduced while maintaining the ability to extract complete three-axis acceleration information through differential measurements.
Solution Approach 2:
The patent uses capacitive coupling and electrostatic induction to create virtual sensing paths without requiring physical wire connections for every sensing element. The electric field coupling between movable and fixed electrodes creates effective signal paths that reduce the need for extensive physical wiring.
3Measurement precision
If separate capacitors are used for each axis measurement, then measurement precision is maintained, but device size becomes large
Solution Approach 1:
The patent merges capacitor structures to serve multiple measurement functions simultaneously. By configuring movable and fixed electrodes to form capacitive sensing elements that can detect displacement in multiple directions through differential capacitance changes, the patent maintains measurement precision while reducing the total number of separate capacitor structures required.
Solution Approach 2:
The patent utilizes the electrostatic field dimension to achieve multi-axis sensing. By measuring capacitance changes in response to electric field variations caused by acceleration-induced displacement, the patent can extract information about acceleration along different axes from the same physical capacitor structure, effectively adding a measurement dimension without increasing physical footprint.
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 reduces the size of the MEMS sensor device while maintaining or enhancing sensitivity, achieving a compact and cost-effective design capable of detecting forces along multiple axes.
Implementation Method 1
a capacitor having a capacitance that changes in response to acceleration or force
Data Source
AI summary
A MEMS acceleration device for measurement of the acceleration along three axes. The device includes capacitors, which capacitance changes under the influence of an acceleration acting upon the device. The change of capacitance for acceleration parallel to the substrate are, normally used with distinct capacitors. This device combines capacitors for using the change in capacitance for sensing in two independent and different directions parallel to the substrate thereby reusing the capacitor. Thereby allowing shrinking of the device while maintaining substantially the same sensitivity.