Variable Band-Pass Filter Circuit for Tracking Biological Signal Frequency

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Solution Overview

Problem

Biological information measurement devices face reduced accuracy due to noise from other biological phenomena or environmental factors superimposed on the measured signals, particularly when frequency fluctuations occur in the biological signals.

Innovation Solution

Incorporation of a variable band-pass filter with a phase-locked loop to synchronize with the phase of the input signal, allowing the passband to dynamically adjust based on the frequency of the tracking signal, thereby isolating the target frequency components and reducing noise interference.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a fixed band-pass filter is used to remove noise, then noise removal is achieved, but the measurement accuracy decreases when biological signal frequency fluctuates

Engineering Contradiction:

Improvebiological information measurement accuracyVSAvoidfrequency tracking capability

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent applies dynamics by transforming a fixed band-pass filter into a variable band-pass filter whose passband can dynamically adjust. The filter's center frequency and bandwidth are modifiable in real-time to track the fluctuating frequency of biological signals, allowing the system to maintain high measurement accuracy across varying physiological conditions while still effectively removing noise.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent implements parameter changes by modifying the frequency characteristics of the band-pass filter. Specifically, the center frequency and bandwidth parameters are adjusted based on the detected biological signal frequency, enabling the filter to adapt to frequency fluctuations and maintain optimal noise removal performance throughout the measurement process.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If a variable band-pass filter is used to track frequency fluctuations, then measurement accuracy is maintained, but device complexity increases

Engineering Contradiction:

Improvebiological information measurement accuracyVSAvoidfilter control system complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent employs feedback by creating a closed-loop system where the biological signal frequency is continuously detected, and this information is fed back to adjust the variable band-pass filter parameters. The frequency detector monitors the signal frequency, and this feedback enables the filter to automatically adapt its center frequency and bandwidth, maintaining measurement accuracy without requiring complex manual intervention.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system implements self-service through automatic frequency tracking. The variable band-pass filter is configured to automatically adjust its parameters based on the detected signal characteristics, eliminating the need for external manual tuning or complex control mechanisms. The filter essentially serves itself by autonomously adapting to frequency changes in the biological signal.

Inventive Principle:

Principle #25Self-service

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 enables accurate calculation of biological information frequencies by continuously tracking frequency fluctuations, ensuring high measurement accuracy even in the presence of noise from other biological phenomena.

Implementation Method 1

a phase-locked loop to generate a tracking signal synchronized with a phase of a signal that has passed through the variable band-pass filter

Methodology Applied

Scientific EffectPhase-locked loop:

Implementation Method 2

a variable band-pass filter with a variable passband

Methodology Applied

Scientific EffectBand-pass filtering: Filter (electronic)

Data Source

PatentUS20250359770A1Biological information measurement device and variable filter circuit

Publication Date: 2025.11.27 MURATA MFG CO LTD

AI summary

A biological information measurement device in which a biological signal with a harmonic structure is input to a variable band-pass filter. A first signal, which has passed through the variable band-pass filter, is input to a frequency calculator. The frequency calculator outputs a second signal including information related to a frequency of the input first signal. A biological information acquirer acquires biological information from the second signal. A band-pass filter controller shifts a passband of the variable band-pass filter based on the information related to the frequency included in the second signal.