MEMS Pressure Sensor Shielding Electromagnetic Interference
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Solution Overview
Problem
Existing MEMS pressure sensors are susceptible to external electromagnetic interference due to their design, which affects the accuracy of pressure detection and increases noise levels, as they require exposure to air and lack effective shielding mechanisms.
Innovation Solution
The MEMS pressure sensing element features a sealed cavity with a pressure-sensitive film and movable electrode plates, where the film drives the electrode plates to change capacitance in response to external pressures, while being shielded from electromagnetic interference by a differential capacitor structure within the sealed cavity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the pressure-sensitive film is exposed in air to enable pressure detection, then the sensor can respond to external air pressures, but external electromagnetic interference will affect the output and increase noise levels
Solution Approach 1:
The sensor is divided into two distinct functional zones: a pressure-sensitive film area exposed to air for pressure detection, and a capacitor area enclosed in a sealed cavity for electromagnetic shielding. This segmentation allows each component to operate in its optimal environment without compromising the other.
Solution Approach 2:
The capacitor structure (including movable electrode plate, fixed electrode plate, and sealing layer) is nested within the substrate, forming a sealed cavity that contains the electrical components. This nested design protects the capacitor from external electromagnetic interference while maintaining the pressure-sensitive film's exposure to air.
2Device complexity
If a single capacitor detection manner is used, then the device structure is simple, but detection errors are large and interference signals cannot be filtered
Solution Approach 1:
The patent employs differential capacitor detection where two capacitors (C1 and C2) are used in a push-pull configuration. When the pressure-sensitive film deflects, one capacitor's capacitance increases while the other decreases, creating a differential signal that amplifies the pressure measurement and cancels out common-mode interference signals.
Solution Approach 2:
The capacitor structure uses asymmetric positioning of the movable electrode plate relative to the fixed electrode plate, creating two capacitors with different initial capacitance values. This asymmetry enables differential detection that is sensitive to pressure-induced changes while rejecting common interference signals.
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 design enhances the precision of pressure detection by isolating the capacitor structures from external electromagnetic interference, reducing noise and improving signal-to-noise ratios, thereby providing more accurate pressure measurements.
Implementation Method 1
a capacitance formed by the pressure-sensitive film and the substrate will be changed, and external pressures can be obtained by detecting such capacitance changes
Data Source
AI summary
The present invention discloses an MEMS pressure sensing element, including a substrate provided with a groove; a pressure-sensitive film disposed above the substrate, the pressure-sensitive film sealing an opening of the groove to form a sealed cavity; and a movable electrode plate and a fixed electrode plate which are located in the sealed cavity and form a capacitor structure, wherein the fixed electrode plate is fixed on a bottom wall of the groove of the substrate, and the movable electrode plate is suspended above the fixed electrode plate and opposite to the fixed electrode plate; and the pressure-sensitive film is connected to the movable electrode plate so as to drive the movable electrode plate to move under the action of an external pressure. According to the MEMS pressure sensing element, pressure sensitivity and electrical detection are separated, the pressure-sensitive film is exposed in air, the capacitor structures are disposed in the sealed cavity defined by the pressure-sensitive film and the substrate, and the movable electrode plates of the capacitor structures can be driven by the pressure-sensitive film. In this way, not only is a pressure-sensitive function finished, but also external electromagnetic interferences on the capacitor structures are shielded.