Differential MEMS Microphone Reducing Total Harmonic Distortion
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Solution Overview
Problem
Existing microphones suffer from high total harmonic distortion (THD), leading to poor signal quality, which previous approaches have not adequately addressed.
Innovation Solution
A dual micro electro mechanical system (MEMS) differential microphone design, where two MEMS devices with diaphragms and back plates are arranged such that positive pressure moves one diaphragm closer to its back plate while simultaneously moving the other diaphragm further away, reducing THD and improving performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single MEMS device is used in a conventional microphone, then the device complexity is low, but the total harmonic distortion is high resulting in poor signal quality
Solution Approach 1:
The microphone is divided into two separate MEMS devices, each with its own diaphragm and back plate, operating in opposite directions. This segmentation allows each device to contribute to reducing harmonic distortion while maintaining manageable individual device complexity
Solution Approach 2:
Two MEMS devices are combined in a differential configuration where their outputs are processed together. The merging of these two devices' signals in a differential architecture achieves superior signal quality by canceling out even-order harmonics that would be present in a single-device configuration
2Measurement precision
If positive pressure moves the diaphragm closer to the back plate in one MEMS device, then the sensitivity increases, but the total harmonic distortion increases
Solution Approach 1:
The second MEMS device is configured as a counterweight to the first, with its diaphragm moving in the opposite direction under positive pressure. This counteracting motion cancels out the nonlinear distortion effects that would otherwise degrade signal quality, while preserving the sensitivity benefits of diaphragm displacement
Solution Approach 2:
The second MEMS device is arranged with its diaphragm and back plate in inverted positions compared to the first device. This inversion causes the diaphragm to move away from the back plate when positive pressure is applied, creating opposite-phase signals that cancel harmonics when combined differentially
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 significantly reduces THD, resulting in improved microphone performance by producing sinusoidal or near-sinusoidal signals with lower distortion.
Implementation Method 1
sound energy traverses through the port, moves the diaphragm and creates a changing potential of the back plate
Implementation Method 2
moves the diaphragm and creates a changing potential of the back plate, which creates an electrical signal
Data Source
AI summary
A microphone includes a base; a first micro electro mechanical system (MEMS) device and a second MEMS device disposed on the base. The first MEMS device has a first diaphragm and a first back plate, and the second MEMS device has a second diaphragm and a second back plate. The first MEMS device and the second MEMS device are arranged such that positive pressure moves the first diaphragm towards the first back plate, and the positive pressure simultaneously moves the second diaphragm of the from second back plate.