Capacitive MEMS Microphone Pre-Deviation for Lower THD and Higher AOP
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Capacitive MEMS microphones suffer from high non-linearity and low acoustic overload point due to the use of diaphragms with low static deflection, which compromises sensitivity and performance.
Innovation Solution
Implement a pre-deviated diaphragm design with a static deflection ratio greater than or equal to 0.5, counteracting non-linearity by introducing mechanical asymmetry to balance capacitance detection non-linearity, using stress structures like stress rings, corrugated membranes, or support structures to achieve greater diaphragm deflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a diaphragm with low static deflection is used to ensure mechanical linear performance, then the mechanical linearity is improved, but the sensitivity and acoustic overload point deteriorate
Solution Approach 1:
The patent applies preliminary anti-action by pre-deviating the diaphragm in a direction away from the back electrode plate before operation. This pre-deviation counteracts the non-linearity that would otherwise occur during operation, allowing the diaphragm to maintain better mechanical linearity while achieving greater static deflection for improved sensitivity and acoustic overload point
Solution Approach 2:
The patent changes the parameter of static deflection by introducing stress structures (such as stress rings or corrugated membranes) that increase the diaphragm's static deflection ratio to 0.5 or greater. This parameter change enables the diaphragm to achieve both high sensitivity and improved non-linearity performance
2Strength
If a diaphragm with low static deflection is used to maintain structural rigidity, then the structural strength is improved, but the total harmonic distortion performance deteriorates
Solution Approach 1:
The pre-deviation of the diaphragm in a direction away from the back electrode plate creates a preliminary mechanical state that counteracts non-linear deformation during operation. This reduces total harmonic distortion while maintaining the structural rigidity needed for structural strength
Solution Approach 2:
The patent employs composite structures including stress rings or corrugated membranes integrated with the diaphragm. These composite structures provide both the necessary rigidity and the stress distribution characteristics that reduce non-linear deformation and total harmonic distortion
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
Improves Total Harmonic Distortion (THD) and Acoustic Overload Point (AOP) performance by reducing overall non-linearity and maintaining sensitivity, allowing for lower bias power requirements and easier fabrication.
Implementation Method 1
at least a portion of the diaphragm is pre-deviated in a direction away from the back electrode plate relative to a flat position
Implementation Method 2
capacitive MEMS microphone includes a back electrode plate, a diaphragm, and a spacer for separating the back electrode plate from the diaphragm
Data Source
AI summary
Disclosed in embodiments of the present disclosure are a capacitive MEMS microphone, a microphone unit and an electronic device. The capacitive MEMS microphone includes: a back electrode plate; a diaphragm; and a spacer for separating the back electrode plate from the diaphragm, wherein in a state where no operating bias is applied, at least a portion of the diaphragm is pre-deviated in a direction away from the back electrode plate relative to a flat position.