Dielectric Comb MEMS Microphone Atmospheric Noise Compensation
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Solution Overview
Problem
Microelectromechanical systems (MEMS) microphones face performance losses due to viscous losses as they shrink in size, and encapsulating them under low pressure or vacuum increases noise from atmospheric pressure fluctuations, which interfere with acoustic signals.
Innovation Solution
A dielectric comb and bellow diaphragm structure within a MEMS transducer that senses both atmospheric and acoustic pressures, using a charge pump to generate a bias voltage and counteract atmospheric pressure noise, and a layered diaphragm to maintain vacuum conditions and reduce stiffness under cyclic loading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If MEMS microphones are shrunk in size, then they can be deployed in smaller devices, but they experience greater signal loss due to friction and lower signal-to-noise ratios
Solution Approach 1:
The patent applies vacuum encapsulation to create an inert environment within the MEMS microphone, removing air molecules that cause viscous friction losses. This allows the microphone to operate in a low-pressure or vacuum environment, significantly reducing friction-related signal loss and improving signal-to-noise ratio while maintaining small size
2Loss of energy
If MEMS microphones are encapsulated under low pressure or vacuum, then viscous losses are reduced, but noise from atmospheric pressure fluctuations increases and interferes with acoustic signals
Solution Approach 1:
The patent segments the pressure sensing function from the acoustic sensing function by using separate conductor pairs: one pair specifically for detecting atmospheric pressure fluctuations and another for detecting acoustic signals. This allows independent processing and filtering of atmospheric noise from desired acoustic information
Solution Approach 2:
The patent implements a feedback mechanism where atmospheric pressure signals detected by the first conductor pair are used to generate compensation signals that counteract the atmospheric pressure noise in the output, effectively canceling out the harmful noise while preserving acoustic signals
3Device complexity
If a single diaphragm structure is used, then device complexity is reduced, but the diaphragm becomes too stiff under cyclic loading or loses vacuum conditions
Solution Approach 1:
The patent divides the diaphragm into multiple separate diaphragms, each serving specific functions: one diaphragm maintains vacuum conditions while another responds to acoustic pressure changes. This segmentation allows each diaphragm to be optimized for its specific function, maintaining flexibility and vacuum stability without excessive complexity
Solution Approach 2:
The patent designs the multi-diaphragm structure to serve multiple functions simultaneously: maintaining vacuum conditions, detecting acoustic pressure, and providing mechanical support. Each diaphragm layer contributes to different aspects of the overall system performance, achieving multi-functionality without proportionally increasing complexity
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 effectively reduces noise from atmospheric pressure fluctuations and maintains microphone performance by counteracting electrostatic forces and maintaining vacuum conditions, enhancing signal quality and reducing viscous losses.
Implementation Method 1
The at least one dielectric bar positioned within the cavity and secured in a fixed position with respect to the cavity such that the at least one dielectric bar remains fixed under the pressure changes. Each of the at least one dielectric bars is adjacent to at least the at least one first conductor or at least one second conductor of the plurality of conductors.
Implementation Method 2
The charge pump electrically connected to at least a portion of the plurality of conductors to provide a biasing charge to at least the portion of the plurality of conductors. The atmospheric pressure processing circuit is configured to process the first electrical signals to generate a charge pump bias signal in response to the pressure changes resulting from the changes in the atmospheric pressure.
Implementation Method 3
The charge pump bias signal is configured to generate an electric force between the plurality of conductors to move the plurality of conductors in a direction opposite a direction of movement caused by the changes in the atmospheric pressure.
Data Source
AI summary
Microphones including a housing defining a cavity, a plurality of conductors positioned within the cavity, at least one dielectric bar positioned within the cavity, and a transducer diaphragm. The conductors are structured to move in response to pressure changes while the housing remains fixed. A first conductor generates first electrical signals responsive to the pressure changes resulting from changes in an atmospheric pressure. A second conductor generates second electrical signals responsive to the pressure changes resulting from acoustic activity. The dielectric bar is fixed with respect to the cavity and remains fixed under the pressure changes. The dielectric bar is adjacent to at least one of the conductors. In response to an applied pressure that is an atmospheric pressure and/or an acoustic pressure, the transducer diaphragm exerts a force on the housing and displaces at least a portion of conductors with respect to the dielectric bar.