Force Feedback Actuator for MEMS Transducer Noise Compensation

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Solution Overview

Problem

Microelectromechanical systems (MEMS) microphones face performance losses due to viscous losses from airflow resistance, leading to lower signal-to-noise ratios, which are exacerbated by smaller device sizes and increased acoustic noise.

Innovation Solution

The implementation of a force feedback actuator with a dielectric comb structure or grid that provides compensation for atmospheric pressure fluctuations, featuring a dielectric grid with controlled voids to stabilize electrostatic force gradients, enhancing sensitivity and operational range.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the microphone size is reduced to fit smaller devices, then device compactness is improved, but acoustic noise increases and signal-to-noise ratio deteriorates

Engineering Contradiction:

Improvemicrophone sizeVSAvoidacoustic noise

Core Design Contradiction:

Volume of moving objectVSObject-affected harmful factors

Solution Approach 1:

The patent implements a force feedback actuator that uses a dielectric comb structure to sense diaphragm position and apply corrective electrostatic forces. The actuator provides feedback control to compensate for acoustic noise and atmospheric pressure effects, maintaining signal quality despite the reduced microphone size.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent changes the physical parameters of the actuator structure by introducing controlled voids within the dielectric comb fingers. This modifies the electrostatic force characteristics and force gradient, enabling effective force feedback compensation in the compact microphone design.

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If a force feedback actuator is implemented to compensate for atmospheric pressure, then signal-to-noise ratio is improved, but device complexity increases

Engineering Contradiction:

Improvesignal-to-noise ratioVSAvoidactuator structure

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The dielectric comb structure serves multiple functions: it acts as both the sensing element for detecting diaphragm position and as the actuating element for applying force feedback. This multi-functionality reduces the need for separate sensing and actuating components, thereby reducing overall device complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The actuator uses a composite structure combining dielectric material with controlled internal voids. This composite design enables the structure to provide both mechanical support and optimized electrostatic force characteristics, achieving effective force feedback with a single integrated component rather than multiple separate elements.

Inventive Principle:

Principle #40Composite materials

3Stability of the object's composition

If controlled voids are added to the dielectric grid, then electrostatic force stability is improved, but manufacturing complexity increases

Engineering Contradiction:

Improveelectrostatic force stabilityVSAvoidvoid structure control

Core Design Contradiction:

Stability of the object's compositionVSManufacturing precision

Solution Approach 1:

The patent introduces controlled voids within the dielectric comb fingers, creating a porous or hollow internal structure. This modifies the electrostatic force characteristics and force gradient to achieve greater stability and linearity. The voids are integrated into the manufacturing process rather than added as separate steps.

Inventive Principle:

Principle #31Porous materials

Solution Approach 2:

The formation of controlled voids is combined with the existing dielectric layer deposition process. The void structure is created during the same manufacturing sequence that forms the dielectric comb fingers, merging the void creation step with the material deposition step to avoid additional complex manufacturing operations.

Inventive Principle:

Principle #5Merging (Combining)

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 solution improves the signal-to-noise ratio by stabilizing electrostatic forces and reducing noise interference, allowing for more effective acoustic signal capture in compact devices.

Implementation Method 1

When a voltage is applied to the adjacent pins, a force is created on the dielectric grid, pulling the dielectric grid parallel to the pins

Methodology Applied

Scientific EffectElectrostatic force: Electrostatics

Implementation Method 2

The dielectric grid has two functions. The first function is to operate as an actuator to provide force feedback to the pressure diaphragm... The second function of the dielectric grid is as a sensor

Methodology Applied

Scientific EffectElectrostatic force stabilization: Electrostatics

Data Source

PatentUS11516597B2Force feedback actuator for a MEMS transducer

Publication Date: 2022.11.29 KNOWLES ELECTRONICS LLC

AI summary

A force feedback actuator includes a pair of electrodes and a dielectric member. The pair of electrodes are spaced apart from one another to form a gap. The dielectric member is disposed at least partially within the gap. The dielectric member includes a first portion having a first permittivity and a second portion having a second permittivity that is different from the first permittivity. The dielectric member and the pair of electrodes are configured for movement relative to each other.