Passive Filter Circuit for Physical Quantity Detection

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Solution Overview

Problem

Existing physical quantity detection devices suffer from saturation issues due to increased detuning frequency components, leading to incorrect outputs, and active filters amplify noise produced by transistors, which is undesirable.

Innovation Solution

A circuit incorporating a passive filter with a cutoff frequency lower than the detuning frequency and a semiconductor substrate with shield wiring lines to suppress detuning frequency components and prevent noise amplification, using a simple CR filter configuration and additional filtering units for further suppression.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If an active filter is used to remove detuning frequency components, then the detuning frequency component can be suppressed, but noise resulting from transistors in the active filter is amplified and outputted

Engineering Contradiction:

Improvedetuning frequency component suppressionVSAvoidnoise from transistors

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent extracts and removes the transistor component from the filter circuit, replacing the active filter with a passive filter that uses only resistors, capacitors, and inductors. This extraction eliminates the noise source (transistors) while maintaining the detuning frequency suppression function through the passive filtering mechanism.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent employs simple passive components (resistors, capacitors, inductors) that are more reliable and noise-free compared to complex active components with transistors. These passive components have no active noise generation and provide stable, long-term operation without the noise amplification issues of transistor-based active filters.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Reliability

If the cutoff frequency of the filter is lowered to better suppress detuning frequency components, then suppression effectiveness improves, but the filter may also attenuate useful signal frequencies

Engineering Contradiction:

Improvedetuning frequency component suppression effectivenessVSAvoiddetection signal accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent applies local quality by designing the passive filter with specific frequency characteristics that target only the detuning frequency components while preserving the detection signal bandwidth. The filter is configured with appropriate cutoff frequencies and Q-factors to create a localized suppression effect at the detuning frequency without affecting the broader detection signal spectrum.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent optimizes the filter parameters (cutoff frequency, Q-factor, component values) to achieve the desired balance between detuning frequency suppression and detection signal preservation. By carefully selecting and adjusting these parameters, the filter effectively removes detuning components while maintaining the integrity of the useful detection signals.

Inventive Principle:

Principle #35Parameter changes

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 solution effectively reduces detuning frequency components and prevents noise amplification, enhancing the reliability of physical quantity detection devices by using passive filters and shield wiring configurations.

Implementation Method 1

a passive filter which has a filter characteristic in which a cutoff frequency is lower than a detuning frequency and a cutoff frequency band contains a frequency band higher than the cutoff frequency

Methodology Applied

Scientific EffectFrequency filtering: Filter (electronic)

Implementation Method 2

a semiconductor substrate with shield wiring lines to suppress detuning frequency components and prevent noise amplification

Methodology Applied

Scientific EffectElectromagnetic shielding: Faraday Cage

Data Source

PatentUS10520316B2Circuit for physical quantity detection device, physical quantity detection device, electronic apparatus, and moving object

Publication Date: 2019.12.31 SEIKO EPSON CORP

AI summary

A circuit for a physical quantity detection device includes a drive unit that generates a drive signal that causes an vibrator to vibrate, a detection unit that detects a detection signal outputted from the vibrator based on the drive signal, a passive filter which has a filter characteristic in which a cutoff frequency is lower than a detuning frequency and a cutoff frequency band contains a frequency band higher than the cutoff frequency and to which a signal from the detection unit is inputted, and an amplification unit that amplifies a signal from the passive filter.