Annular Electrode Segmentation for Piezoelectric Microphone Sensitivity

Solution Overview

Problem

Piezoelectric microphones face challenges in maintaining sensitivity as they shrink in size, due to charge normalization across regions of differing curvature, leading to reduced voltage sensitivity, especially in small-dimension devices.

Innovation Solution

The introduction of gaps between electrodes at inflection points allows for selective connection of capacitors in parallel or series, enhancing voltage and charge sensitivity by avoiding charge normalization and optimizing sensor circuit design.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the microphone size is reduced, then the device compactness is improved, but the voltage sensitivity deteriorates due to charge normalization across regions of differing curvature

Engineering Contradiction:

Improvemicrophone sizeVSAvoidvoltage sensitivity

Core Design Contradiction:

Volume of moving objectVSMeasurement precision

Solution Approach 1:

The patent divides the continuous electrode structure into segmented regions with gaps at inflection points. This segmentation prevents charge normalization by creating electrically isolated regions, thereby maintaining voltage sensitivity even in reduced-size microphones. The gaps are strategically positioned at inflection points where curvature changes occur, allowing each segment to independently respond to acoustic pressure variations.

Inventive Principle:

Principle #1Segmentation

2Ease of manufacture

If continuous electrodes are used across regions of differing curvature, then the manufacturing simplicity is improved, but the charge normalization occurs leading to reduced sensitivity

Engineering Contradiction:

Improveelectrode structure simplicityVSAvoidvoltage sensitivity

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The electrode structure is segmented with gaps positioned at inflection points, which are regions of zero curvature. This segmentation approach maintains manufacturing simplicity by using standard photolithography techniques while preventing charge normalization. The gaps are formed as part of the standard electrode fabrication process, adding minimal complexity to manufacturing.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies local quality by introducing gaps specifically at inflection points rather than uniformly across the electrode. This localized modification targets the specific regions where charge normalization occurs, maintaining electrode continuity in other areas and preserving manufacturing simplicity while improving sensitivity.

Inventive Principle:

Principle #3Local quality

3Measurement precision

If gaps are introduced at inflection points, then the voltage sensitivity is improved by avoiding charge normalization, but the device complexity increases

Engineering Contradiction:

Improvevoltage sensitivityVSAvoidelectrode structure complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The electrode structure is segmented with gaps positioned at inflection points, which are regions of zero curvature. This segmentation approach maintains manufacturing simplicity by using standard photolithography techniques while preventing charge normalization. The gaps are formed as part of the standard electrode fabrication process, adding minimal complexity to manufacturing.

Inventive Principle:

Principle #1Segmentation

4Quantity of substance

If the dielectric constant is increased to improve capacitance, then the capacitance value is improved, but the lateral stress coupling and charge normalization issues persist

Engineering Contradiction:

ImprovecapacitanceVSAvoidvoltage sensitivity

Core Design Contradiction:

Quantity of substanceVSMeasurement precision

Solution Approach 1:

The patent divides the continuous electrode structure into segmented regions with gaps at inflection points. This segmentation prevents charge normalization by creating electrically isolated regions, thereby maintaining voltage sensitivity even in reduced-size microphones. The gaps are strategically positioned at inflection points where curvature changes occur, allowing each segment to independently respond to acoustic pressure variations.

Inventive Principle:

Principle #1Segmentation

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 approach improves voltage and charge sensitivity, increasing the signal-to-noise ratio and enabling effective signal processing in small-dimension microphones and transducers.

Implementation Method 1

The piezoelectric mic includes a layer of piezoelectric material between two conductive plates (electrodes). An acoustic wave incident on the membrane of the mic results in the application of a time varying force to the piezoelectric material. Application of this force to piezoelectric material results in induced stresses in the piezoelectric material, which in-turn creates a time-varying voltage signal across the material.

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS7538477B2Multi-layer transducers with annular contacts

Publication Date: 2009.05.26 AVAGO TECHNOLOGIES INTERNATIONAL SALES PTE LTD

AI summary

Transducer structures having multiple piezoelectric layer and annular contacts are described.