MEMS Microphone Force Feedback via Dielectric Grid
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Solution Overview
Problem
Small microphones, particularly MEMS microphones, face performance losses due to viscous losses from airflow resistance, leading to higher acoustic noise and lower signal-to-noise ratios, and existing solutions struggle to achieve a dynamic range that can distinguish between atmospheric pressure and acoustic signals effectively.
Innovation Solution
A MEMS transducer with a pressure diaphragm exposed to a closed chamber at low pressure, utilizing a dielectric grid as both an actuator and sensor to generate a force feedback that offsets atmospheric pressure, allowing the diaphragm to respond only to acoustic pressure changes, thereby enhancing signal clarity and reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a closed chamber at low pressure is used, then atmospheric pressure impact is reduced and signal-to-noise ratio is improved, but device complexity increases
Solution Approach 1:
The patent implements a nested structure where a closed chamber containing a MEMS transducer is integrated within a housing that includes an atmospheric equalization vent. The closed chamber is sealed to the housing, creating a nested configuration that maintains low pressure inside the chamber while allowing the system to function as a complete microphone device. This nesting approach achieves the desired pressure isolation without requiring separate, complex pressure control systems.
Solution Approach 2:
The patent introduces an atmospheric equalization vent as an intermediary element that connects the housing interior to the exterior environment. This vent acts as a mediator that allows atmospheric pressure to equalize in the housing while preventing acoustic signals from entering the closed chamber, thus isolating the acoustic signal from atmospheric pressure variations without requiring complex active pressure control mechanisms.
2Measurement precision
If atmospheric pressure compensation is implemented, then acoustic signal isolation is improved, but force feedback mechanism complexity increases
Solution Approach 1:
The patent employs a self-service approach where the MEMS transducer's diaphragm naturally responds to pressure differential changes between the closed chamber and atmospheric pressure. The sensing element automatically detects both atmospheric pressure variations and acoustic signals through this pressure differential, eliminating the need for complex external force feedback mechanisms or active compensation systems. The system uses the inherent physical response of the diaphragm to achieve pressure compensation.
3Volume of moving object
If smaller microphone size is used, then device miniaturization is achieved, but acoustic noise increases due to airflow resistance
Solution Approach 1:
The patent creates an inert environment by evacuating air from the closed chamber, establishing a vacuum or low-pressure condition inside the chamber. This inert environment eliminates air molecules that would otherwise create viscous losses and acoustic noise through airflow resistance. The absence of gas molecules in the closed chamber allows the diaphragm to respond to acoustic signals without the harmful interactions that occur in atmospheric conditions, thereby reducing acoustic noise while maintaining small device size.
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 significantly reduces noise by minimizing the impact of atmospheric pressure on the diaphragm, enabling a higher signal-to-noise ratio and achieving a dynamic range that spans from 0.0001 Pa to 100 kPa, effectively isolating acoustic signals from atmospheric pressure variations.
Implementation Method 1
utilizing a dielectric grid as both an actuator and sensor to generate a force feedback that offsets atmospheric pressure
Implementation Method 2
A MEMS transducer with a pressure diaphragm exposed to a closed chamber at low pressure
Data Source
AI summary
A MEMS transducer for a microphone includes a closed chamber, an array of conductive pins, a dielectric grid, and a diaphragm. The closed chamber is at a pressure lower than atmospheric pressure. The array of conductive pins is in a fixed position in the closed chamber, distributed in two dimensions, and have gaps formed therebetween. The dielectric grid is positioned within the closed chamber, includes a grid of dielectric material positioned between the gaps of the array of conductive pins, and is configured to move parallel to the conductive pins. The diaphragm is configured to form a portion of the closed chamber and deflect in response to changes in a differential pressure between the pressure within the closed chamber and a pressure outside the transducer. The diaphragm is configured to move the dielectric grid relative to the array of conductive pins in response to a change in the differential pressure.