MEMS Sensor Common-Mode Read-Out Circuit Robustness
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
MEMS sensors face challenges in robustness due to sensitivity to external disturbances such as particles and varying temperatures, which affect their accuracy and reliability, especially when interacting with fluids like air or gases.
Innovation Solution
The design incorporates a MEMS sensor arrangement with a stator electrode between two movable electrodes, connected to a common-mode read-out circuit via capacitive coupling, allowing for different bias voltages to be applied. This configuration enables additive contributions to measurement signals from both electrodes, enhancing robustness by compensating for external disturbances and reducing sensitivity to interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional MEMS sensor with single movable electrode is used, then the device complexity is low, but the sensor sensitivity to external disturbances is high
Solution Approach 1:
The single movable electrode is segmented into two separate movable electrodes (first movable electrode and second movable electrode), each capable of independent movement. This segmentation allows the sensor to measure different physical quantities simultaneously and provides redundancy against external disturbances, thereby improving reliability while managing complexity through modular design
Solution Approach 2:
The patent applies different bias voltages (first bias voltage and second bias voltage) to the two movable electrodes, creating different operating parameters for each electrode. This parameter differentiation enables the electrodes to respond differently to the same external stimulus, allowing disturbance rejection through differential measurement techniques while maintaining manageable device complexity
2Reliability
If the first movable electrode and second movable electrode are positioned at different distances from the stator electrode, then the measurement signal robustness is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent deliberately positions the first movable electrode and second movable electrode at different distances from the stator electrode, creating an asymmetric configuration. This asymmetry ensures that the electrodes have different capacitance values and respond differently to external disturbances, improving measurement signal robustness. The design accepts increased manufacturing precision requirements as a necessary trade-off to achieve the desired asymmetric positioning
Solution Approach 2:
The read-out circuit measures the capacitance changes of both movable electrodes and processes these signals to compensate for positioning variations. By using feedback from the actual measured capacitance values, the system can adjust and normalize the measurements, reducing the impact of manufacturing tolerances on the final measurement accuracy
3Object-affected harmful factors
If a common-mode read-out circuit with capacitive coupling is used, then the insensitivity to disturbances is improved, but the device complexity increases
Solution Approach 1:
The patent introduces a common-mode read-out circuit with capacitive coupling as an intermediary between the movable electrodes and the signal processing system. This intermediary circuit measures the capacitance changes of both electrodes and processes them in a common-mode configuration, which inherently rejects disturbances that affect both electrodes equally. The added circuit complexity is justified by the significant reduction in disturbance sensitivity
Solution Approach 2:
The common-mode read-out circuit maintains equipotential references for both movable electrodes, ensuring that both electrodes operate from the same potential baseline. This equipotential configuration allows the circuit to measure differential capacitance changes while rejecting common-mode disturbances, improving insensitivity to external factors while managing circuit complexity through symmetric design
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 solution provides robust MEMS sensors that are less sensitive to external disturbances, maintaining accuracy and reliability even in varying ambient conditions, such as those encountered with fluid interactions, by utilizing a common-mode read-out circuit with differential bias voltages.
Implementation Method 1
a common-mode read-out circuit connected to the stator electrode by a capacitive coupling and comprising a second bias voltage source, which is configured to apply a second bias voltage to a side of the capacitive coupling that faces away from the stator electrode
Implementation Method 2
MEMS sensors can utilize different physical effects in order to carry out sensor-based measurements. One example thereof is the deflection of a membrane
Data Source
AI summary
In accordance with an embodiment, a MEMS sensor includes a MEMS arrangement having a movable electrode and a stator electrode arranged opposite the movable electrode. The MEMS sensor includes a first bias voltage source, which is connected to the stator electrode and which is configured to apply a first bias voltage to the stator electrode. The MEMS sensor further includes a common-mode read-out circuit connected to the stator electrode by a capacitive coupling and comprising a second bias voltage source, which is configured to apply a second bias voltage to a side of the capacitive coupling that faces away from the stator electrode.