MEMS Transducer Shared Cavity Differential Noise Rejection

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Solution Overview

Problem

Miniaturization of MEMS sensors is hindered by parasitic capacitance effects, which reduce effective gain and increase susceptibility to mechanical and electrical noise, making it challenging to design efficient interface circuits.

Innovation Solution

A MEMS transducer system comprising two MEMS transducer elements with a shared cavity, acoustically coupled and biased with different or same bias voltages, generating differential signals that are amplified to produce an output, with the option of using multiple transducer elements and various amplifier configurations to enhance signal processing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If MEMS sensors are miniaturized, then device size is reduced, but parasitic capacitance effects increase reducing effective gain and increasing susceptibility to noise

Engineering Contradiction:

ImproveMEMS sensor sizeVSAvoidsignal quality

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The patent divides the sensing function into multiple transducer elements (first and second MEMS transducer elements) that operate differentially. This segmentation allows the system to maintain smaller individual element sizes while achieving better noise rejection and signal quality through differential operation, resolving the contradiction between miniaturization and signal reliability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent converts the harmful effect of parasitic capacitance into a beneficial differential configuration. By using matched parasitic capacitances in both transducer elements and operating them differentially, the parasitic effects cancel out, transforming what was previously a harmful limitation into an advantage that enables better noise rejection and maintains signal quality even in miniaturized devices.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Volume of moving object

If MEMS sensors are miniaturized, then device size is reduced, but susceptibility to mechanical and electrical noise increases

Engineering Contradiction:

ImproveMEMS sensor sizeVSAvoidnoise susceptibility

Core Design Contradiction:

Volume of moving objectVSObject-affected harmful factors

Solution Approach 1:

The patent segments the sensing system into multiple transducer elements that can be differentially operated. This allows noise rejection through differential signaling while maintaining miniaturized device dimensions, as the noise cancellation occurs through signal processing rather than requiring larger physical structures.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent transforms the harmful noise susceptibility into a benefit by using differential operation. The matched parasitic capacitances and differential signaling configuration cause noise and interference to cancel out, converting what was previously a vulnerability into a robust noise-rejection capability in miniaturized devices.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Device complexity

If interface circuits are designed for miniaturized sensors, then device integration is improved, but design complexity increases due to parasitic effects

Engineering Contradiction:

Improveinterface circuit designVSAvoidparasitic effect control

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The patent segments the transducer into multiple elements with matched parasitic characteristics. This segmentation simplifies interface circuit design because the differential configuration naturally rejects parasitic effects, eliminating the need for complex compensation circuits that would otherwise be required to achieve the same level of performance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent converts the harmful parasitic effects into a beneficial differential configuration. By designing the interface circuit to exploit the symmetry and matching of parasitic capacitances in the differential pair, the circuit automatically compensates for parasitic effects without requiring additional complex components or calibration, thereby reducing overall design complexity.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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

The system achieves robust performance with reduced noise interference, linear operation, high dynamic range, and efficient signal processing, even under high sound pressure levels, while maintaining manufacturing cost-effectiveness and physical robustness.

Implementation Method 1

the semiconductor substrate includes a shared cavity acoustically coupled to the first and second MEMS transducer elements

Methodology Applied

Scientific EffectAcoustic coupling: Acoustics

Data Source

PatentUS11225408B2System and method for a mems transducer

Publication Date: 2022.01.18 INFINEON TECHNOLOGIES AG

AI summary

An embodiment as described herein includes a microelectromechanical system (MEMS) with a first MEMS transducer element, a second MEMS transducer element, and a semiconductor substrate. The first and second MEMS transducer elements are disposed at a top surface of the semiconductor substrate and the semiconductor substrate includes a shared cavity acoustically coupled to the first and second MEMS transducer elements.