MEMS Microphone Electrode Layout for Low-Loss Directional Sensing
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Solution Overview
Problem
Traditional directional microphones rely on pressure differences across a membrane to convert sound waves into electrical signals, which can result in high acoustic losses and limited directional sensitivity.
Innovation Solution
A MEMS transducer design featuring a moveable electrode and a pair of fixed electrodes in a stacked arrangement, laterally spaced apart, that responds to viscous drag forces from air flow, eliminating the need for backplates and enhancing directional sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If traditional pressure difference transduction is used, then the microphone can convert sound waves to electrical signals, but acoustic losses increase and directional sensitivity is limited
Solution Approach 1:
The patent replaces the traditional pressure difference transduction mechanism with a viscous drag force-based transduction mechanism. Instead of relying on pressure differential across a membrane, the invention uses air flow-induced viscous drag forces on a moveable electrode to generate electrical signals, thereby reducing acoustic losses while maintaining or improving directional sensitivity
Solution Approach 2:
The invention changes the fundamental transduction parameter from pressure difference to viscous drag force. By utilizing the viscous drag force generated by air flow directly on the moveable electrode, the system achieves better directional sensitivity and lower acoustic losses compared to traditional pressure difference methods
2Device complexity
If backplates are used in traditional MEMS microphones, then the structure is complete, but acoustic losses increase
Solution Approach 1:
The patent removes the backplate component from the traditional MEMS microphone structure. By eliminating the backplate, the invention reduces acoustic losses that occur in traditional designs while maintaining structural integrity through an alternative support configuration for the moveable electrode
Solution Approach 2:
The invention transitions from a planar parallel-plate capacitor arrangement to a three-dimensional stacked electrode arrangement. This dimensional change allows the moveable electrode to be positioned between two fixed electrodes in the vertical direction, creating a more efficient acoustic pathway and reducing losses
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 design minimizes acoustic losses and improves directional sensitivity by leveraging air flow-induced drag forces, allowing for enhanced sound capture from specific directions.
Implementation Method 1
A MEMS transducer design featuring a moveable electrode and a pair of fixed electrodes in a stacked arrangement, laterally spaced apart, that responds to viscous drag forces from air flow
Implementation Method 2
The pair of fixed electrodes are laterally spaced apart from the end of the moveable electrode to establish a capacitance indicative of the vibrational movement
Data Source
AI summary
A microelectromechanical (MEMS) transducer includes a substrate, a moveable electrode supported by the substrate, and a pair of fixed electrodes supported by the substrate, each fixed electrode of the pair of fixed electrodes being configured as a bias or sense electrode. The pair of fixed electrodes are disposed in a stacked arrangement. An end of the moveable electrode is configured for vibrational movement along the stacked arrangement during excitation of the moveable electrode. The pair of fixed electrodes are laterally spaced apart from the end of the moveable electrode to establish a capacitance indicative of the vibrational movement.