Capacitance Sensor with Segmented Electrodes for Dynamic Range

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Solution Overview

Problem

Conventional microphones face challenges in achieving a wide dynamic range due to trade-offs between detection sensitivity and total harmonic distortion, with fluctuations in acoustic characteristics and mismatching between sensing units limiting their performance.

Innovation Solution

A capacitance sensor with multiple sensing units of different sensitivities, where the vibration and fixed electrode plates are divided into regions, and an isolation portion is formed on the back plate to suppress vibration propagation, reducing harmonic distortion and mismatching between units.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the detection sensitivity of acoustic vibration is improved, then the ability to detect low sound pressure sound is enhanced, but the total harmonic distortion increases when receiving high sound pressure sound

Engineering Contradiction:

Improvedetection sensitivityVSAvoidtotal harmonic distortion

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

The vibration electrode plate is divided into multiple regions, creating multiple sensing units with different sensitivities. Each sensing unit has a specific detection range, allowing the system to handle both low and high sound pressure levels without excessive harmonic distortion by selecting the appropriate sensing unit for the current sound pressure level.

Inventive Principle:

Principle #1Segmentation

2Reliability

If the maximum detection sound pressure is increased by reducing total harmonic distortion, then the dynamic range is expanded, but the sensitivity to detect low sound pressure sound is deteriorated

Engineering Contradiction:

Improvemaximum detection sound pressureVSAvoiddetection sensitivity

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

Multiple sensing units with different sensitivities are created by dividing the electrode plates. Each sensing unit is optimized for specific sound pressure ranges, enabling the system to maintain high sensitivity for low sound pressure detection while also handling high sound pressure levels without distortion.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The sensitivity parameters of different sensing units are adjusted by varying the area of vibration electrode plate regions or the gap distances between electrode plates. This allows each sensing unit to be tuned for specific detection ranges, achieving both high sensitivity and high maximum detection pressure capabilities.

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If multiple acoustic sensors with different detection sensitivities are used to achieve wide dynamic range, then the detection capability is improved, but fluctuations in acoustic characteristics and mismatching between sensing units occur

Engineering Contradiction:

Improvedynamic rangeVSAvoidacoustic characteristic consistency

Core Design Contradiction:

Adaptability or versatilityVSStability of the object's composition

Solution Approach 1:

Multiple sensing units are integrated into a single capacitance sensor structure with shared electrode plates and isolation portions. This unified structure reduces manufacturing variations and acoustic characteristic fluctuations compared to using completely separate sensors, while maintaining the benefits of multiple sensitivity levels.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

Isolation portions are introduced between sensing units to prevent vibration propagation from one unit to another. This intermediary structure eliminates cross-interference and mismatching between sensing units, ensuring each unit operates independently with stable acoustic characteristics.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 configuration allows for a wider dynamic range without compromising sensitivity, as distortion vibrations are isolated, preventing harmonic distortion and maintaining sensitivity across varying sound pressures.

Implementation Method 1

The acoustic sensor used in the MEMS microphone is an electrostatic capacitance acoustic sensor manufactured by using the MEMS technique

Methodology Applied

Scientific EffectElectrostatic capacitance: Capacitance

Implementation Method 2

an isolation portion to suppress vibration from being propagated is formed on the back plate to partition the sensing units from each other

Methodology Applied

Scientific EffectVibration isolation: Damping

Data Source

PatentUS9118994B2Capacitance sensor, acoustic sensor, and microphone

Publication Date: 2015.08.25 MMI SEMICON CO LTD

AI summary

A capacitance sensor has a substrate, a vibration electrode plate formed over an upper side of the substrate, a back plate formed over the upper side of the substrate to cover the vibration electrode plate, and a fixed electrode plate arranged on the back plate facing the vibration electrode plate. At least one of the vibration electrode plate and the fixed electrode plate is divided into a plurality of regions. A sensing unit configured by the vibration electrode plate and the fixed electrode plate is formed on each of the divided regions. An isolation portion that suppresses vibration from being propagated is formed on the back plate to partition the sensing units from each other.