Grounded Shield Structure for Dual Mass Accelerometer Interference

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Solution Overview

Problem

Dual mass accelerometers face challenges in achieving high sensitivity while maintaining immunity to external interference and low power consumption, as current designs require voltage regulators to maintain shield potentials, which can be limited by power constraints and interfere with capacitance measurements.

Innovation Solution

The dual mass accelerometer is designed with a shield structure biased at ground potential, eliminating the need for voltage regulators and allowing for differential measurements with larger amplitude voltages, thereby enhancing resistance to interference and reducing power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If voltage regulators are used to maintain shield potentials, then immunity to external interference is improved, but power consumption increases and sensitivity is reduced

Engineering Contradiction:

Improveimmunity to external interferenceVSAvoidpower consumption

Core Design Contradiction:

Object-affected harmful factorsVSUse of energy by moving object

Solution Approach 1:

The patent removes the voltage regulator component from the system by grounding the shield structure directly. This extraction eliminates the power consumption associated with voltage regulation while maintaining interference immunity through the grounded shield configuration.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Instead of actively maintaining the shield at a specific potential using voltage regulators, the patent inverts the approach by grounding the shield and allowing it to naturally follow ground potential. This passive grounding approach eliminates the need for active power-consuming regulation.

Inventive Principle:

Principle #13The other way round (Inversion)

2Stability of the object's composition

If voltage regulators are used to maintain shield potentials, then shield stability is improved, but measurement precision deteriorates due to interference with capacitance measurements

Engineering Contradiction:

Improveshield potential stabilityVSAvoidcapacitance measurement accuracy

Core Design Contradiction:

Stability of the object's compositionVSMeasurement precision

Solution Approach 1:

The voltage regulator is removed from the system, eliminating its interfering electric fields and current paths that disrupted capacitance measurements. The grounded shield provides stability without the measurement interference caused by active regulation.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The ground connection serves as an intermediary that provides a stable reference potential for the shield without introducing the active regulation interference. The ground acts as a passive mediator that stabilizes the shield potential while being electrically neutral to capacitance measurements.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Measurement precision

If larger amplitude voltages are used for differential measurements, then signal-to-noise ratio is improved, but power consumption increases

Engineering Contradiction:

Improvesignal-to-noise ratioVSAvoidpower consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent converts the previously harmful effect of unregulated shield potentials into a beneficial grounded reference. This allows larger measurement voltages to be applied without the added power burden of regulating the shield, as the grounded shield naturally absorbs any electrostatic effects.

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

This configuration increases the accelerometer's tolerance to external interferers, maintains low electrostatic forces, and allows for higher signal-to-noise ratios without significant power increase, improving sensitivity and operational stability.

Implementation Method 1

a shield structure coupled to the substrate and formed adjacent the first proof mass, wherein the shield structure is electrically coupled to a fixed ground potential

Methodology Applied

Scientific EffectElectrostatic shielding: Faraday Cage

Implementation Method 2

a first movable electrode that is electrically coupled to a first fixed electrode having a first potential and may be coupled to a second fixed electrode having a second potential

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentEP4354151A1Accelerometer having a grounded shield structure

Publication Date: 2024.04.17 STMICROELECTRONICS INT NV

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Figure 1C

AI summary

An embodiment of an accelerometer front-end device includes a substrate and a first proof mass coupled to the substrate and electrically coupled to a first movable electrode and electrically coupled to a first fixed electrode having a first potential and electrically coupled to a second fixed electrode having a second potential. A shield structure is coupled to the substrate, and adjacent the first proof mass, wherein the shield structure is electrically coupled to a fixed ground potential. A second proof mass is coupled to the substrate that includes a second movable electrode that is electrically coupled to a third fixed electrode having a third potential and is electrically coupled to a fourth fixed electrode having a fourth potential, wherein the second proof mass is electrically coupled to the fixed ground potential.