Impedance Circuitry for Biometric Signal Interference Mitigation
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Solution Overview
Problem
Biometric signal measurements are interfered with by motion artefacts and triboelectric effects caused by varying impedance circuits and uneven electric charge distribution across skin electrodes, especially when measuring moving subjects.
Innovation Solution
A measurement apparatus with differential amplifier circuitry and impedance circuitry that tunes input impedance to be higher within the frequency band of biometric signals, suppressing interference by equalizing skin electrode potentials and grounding DC charges, while maintaining high impedance on the measurement frequency band and low impedance outside it.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If skin electrodes are used to measure biometric signals from a moving body, then the measurement can be performed on moving subjects, but motion artefacts and triboelectric effects cause interference and reduce measurement precision
Solution Approach 1:
The patent applies equipotentiality by connecting skin electrodes through an impedance circuit configured to equalize their electrical potentials. The circuit includes impedance elements arranged to create equipotential points that cancel out potential differences caused by motion artifacts and triboelectric effects, thereby reducing interference and improving measurement precision while maintaining the ability to measure on moving subjects
Solution Approach 2:
The patent changes the impedance parameters of the circuit by using frequency-dependent impedance elements. The impedance circuit is designed with specific impedance values and frequency characteristics that optimize the cancellation of motion artifacts while preserving the biometric signal, effectively resolving the contradiction between measurement adaptability and precision
2Adaptability or versatility
If skin electrodes are in continuous motion with respect to the skin, then measurements can be taken during movement, but the motion modulates the impedance circuit and causes motion artefacts that interfere with measurement
Solution Approach 1:
The impedance circuit creates equipotential connections between skin electrodes that remain effective during motion. By configuring the impedance elements to equalize potentials dynamically, the circuit compensates for impedance modulations caused by electrode movement, maintaining measurement reliability while allowing movement during measurement
Solution Approach 2:
The patent employs feedback mechanisms where the impedance circuit continuously adjusts to compensate for motion-induced impedance changes. The circuit configuration provides automatic compensation that detects and counteracts motion artifacts in real-time, ensuring measurement stability during movement
3Measurement precision
If the impedance of the impedance circuitry is made higher to suppress interference, then measurement accuracy improves, but signals outside the frequency band are also affected
Solution Approach 1:
The patent applies local quality by designing the impedance circuit with frequency-selective impedance elements that provide different impedance characteristics for different frequency bands. The circuit is configured to present high impedance specifically at the biometric signal frequency band to suppress interference, while maintaining appropriate impedance characteristics for other frequency ranges, thus selectively improving measurement precision without adversely affecting other signals
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
Effectively reduces motion-induced interference and triboelectric effects, enhancing the accuracy and reliability of biometric signal measurements by stabilizing input impedance and equalizing skin electrode potentials.
Implementation Method 1
impedance circuitry coupled between the first signal line and the second signal line in order to tune input impedance of the differential amplifier, wherein impedance of the impedance circuitry is higher on a first frequency band covering a frequency band of the measured biometric signals than on a second frequency band outside the frequency band of the measured biometric signals
Implementation Method 2
the contact between the skin electrodes and the subject's skin causes a triboelectric effect, also known as triboelectric charging. The triboelectric effect is a type of contact electrification in which materials in contact with each other become electrically charged as a result of their movement with respect to each other
Data Source
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AI summary
This document presents an apparatus comprising: a first signal line configured to couple signals from a first skin electrode to a first input of a differential amplifier comprised as a front-stage in a signal detection circuitry for measurement of biometric signals sensed by the first skin electrode; a second signal line configured to couple signals from a second skin electrode, different from the first skin electrode, to a second input of the differential amplifier of the signal detection circuitry for measurement of biometric signals sensed by the second skin electrode; and an impedance circuitry coupled between the first signal line and the second signal line in order to tune input impedance of the differential amplifier, wherein impedance of the impedance circuitry is higher on a first frequency band covering a frequency band of the measured biometric signals than on a second frequency band not covering the frequency band of the measured biometric signals.