MEMS Accelerometer Self-Calibration via Segmented Reference Electrodes
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Solution Overview
Problem
Current MEMS accelerometers face challenges in self-adjusting calibration of offset and sensitivity due to external mechanical sources, which degrade signal-to-noise ratio (SNR) and require larger reference electrodes that occupy valuable space and reduce sensitivity.
Innovation Solution
The design incorporates smaller reference paddles placed at the center of the electrode, with separate signal paths for acceleration and reference electrodes, allowing for self-adjusting calibration of offset and sensitivity by sampling and modifying signals to enhance sensitivity without reducing SNR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If larger reference electrodes are used to reduce offset from exogenous mechanical sources, then offset calibration accuracy is improved, but device area is increased and sensitivity is reduced
Solution Approach 1:
The patent divides the reference electrode into multiple segments arranged in a specific pattern around the active electrode. This segmentation allows the reference electrode to maintain sufficient area for offset calibration while fitting within a compact device footprint, resolving the contradiction between calibration accuracy and device area.
Solution Approach 2:
The patent transitions from a conventional linear or simple geometric arrangement to a two-dimensional patterned arrangement of reference electrode segments. This dimensional change enables more efficient space utilization, providing adequate reference electrode area without increasing the overall device footprint, thus resolving the area contradiction.
2Measurement precision
If larger reference electrodes are used to reduce offset from exogenous mechanical sources, then offset calibration accuracy is improved, but sensitivity is reduced
Solution Approach 1:
The patent applies different qualities to different regions: the active electrode maintains high sensitivity characteristics while the segmented reference electrode provides offset calibration functionality. The spatial separation and functional differentiation allow each region to optimize its specific purpose without compromising the other, resolving the contradiction between calibration accuracy and sensitivity.
3Measurement precision
If reference electrodes are placed at a distance from active electrodes, then offset calibration is improved, but device complexity and space utilization are worsened
Solution Approach 1:
The patent merges the active electrode and reference electrode into a single integrated electrode structure where reference segments are positioned around the active electrode. This merging eliminates the need for separate distant reference electrodes, reducing device complexity and improving space utilization while maintaining offset calibration capability through the integrated design.
4Measurement precision
If reference electrodes occupy valuable space, then offset calibration is improved, but active sensing area is reduced
Solution Approach 1:
The reference electrode is segmented and arranged in a compact pattern that minimizes its footprint. This segmentation allows the reference electrode to provide sufficient calibration functionality while occupying minimal space, thereby preserving maximum active sensing area for the active electrode.
Solution Approach 2:
The patent uses a two-dimensional patterned arrangement of segmented reference electrodes that efficiently packs the reference electrode area within the available device footprint. This dimensional optimization ensures that the reference electrode provides adequate calibration capability without encroaching significantly on the active sensing area.
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 increases the sensitivity of MEMS devices while maintaining offset accuracy, improving the signal-to-noise ratio and reducing the size of reference paddles, thus enhancing the performance of MEMS devices like accelerometers, magnetometers, and barometers.
Implementation Method 1
The MEMS device includes a first capacitive sensing element disposed between the proof mass and the sense electrodes and a second capacitive sensing element disposed between the proof mass and the reference electrodes
Data Source
AI summary
Techniques for self-adjusting calibration of offset and sensitivity of a MEMS accelerometer are provided. In one example, a system comprises a first microelectromechanical (MEMS) sensor. The first MEMS sensor comprises: a proof mass coupled to an anchor connected to a reference plane, wherein the proof mass is coupled to the anchor via a first spring and a second spring; a plurality of reference paddles coupled to the anchor; and a plurality of acceleration sensing electrodes disposed on the reference plane, wherein a first area of each of the acceleration sensing electrodes is larger than a second area of each of a plurality of reference electrodes associated with the plurality of reference paddles.