Self-Oscillating Split-Ring Resonator for Noise-Resistant Physiological Signal Detection

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Solution Overview

Problem

Physiological signals, such as heart beats and pulse signals, are weak and prone to interference from noise, device fit, ambient light, and skin properties, making their detection and analysis challenging in wearable devices.

Innovation Solution

A physiological signal sensor utilizing a self-oscillating complementary split-ring resonator (SO-CSRR) element, demodulator, baseband amplifier, and microcontroller (MCU) that detects signals through perturbation and injection-locked theories, transforming them into modulated signals for improved detection and processing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional PPG sensors are used to detect physiological signals, then the device can measure pulse signals, but the detection is affected by noise, ambient light, device fit, and skin properties reducing measurement precision

Engineering Contradiction:

Improvephysiological signal detection accuracyVSAvoidnoise and interference from ambient light, device fit, and skin properties

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent introduces a self-oscillating complementary split-ring resonator (SO-CSRR) as an intermediary sensing element that converts physiological signal-induced mechanical perturbations into frequency-modulated oscillation signals. This intermediary mechanism transforms weak physiological signals into robust frequency-domain representations that are inherently more resistant to noise and interference from ambient light, device fit variations, and skin properties.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces conventional optical detection mechanisms with a mechanical resonance-based detection system. The SO-CSRR element utilizes mechanical oscillations and resonance phenomena to detect physiological signals, substituting the optical field-based PPG approach with a mechanical field-based approach that is less susceptible to optical interference and ambient light effects.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If physiological signals are detected using conventional methods, then basic pulse measurement is achieved, but the weak signal strength makes detection difficult and requires complex noise filtering

Engineering Contradiction:

Improvesignal detection reliabilityVSAvoiddifficulty in detecting weak physiological signals

Core Design Contradiction:

ReliabilityVSDifficulty of detecting and measuring

Solution Approach 1:

The patent employs mechanical vibration and resonance principles through the self-oscillating SO-CSRR element. The resonator is designed to oscillate at a specific resonant frequency, and physiological signals cause perturbation in this oscillation. By operating at resonance, the system amplifies the response to physiological inputs while maintaining immunity to non-resonant noise, thereby improving detection reliability without requiring complex filtering.

Inventive Principle:

Principle #18Mechanical vibration

Solution Approach 2:

The patent transforms the detection approach by changing the parameter domain from amplitude-based detection (conventional PPG) to frequency-based detection. The SO-CSRR converts physiological signal-induced mechanical perturbations into frequency modulations of the oscillation signal. This parameter transformation enhances signal-to-noise ratio because frequency measurements are inherently more precise and less susceptible to amplitude variations caused by noise and interference.

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 sensor achieves high sensitivity in measuring physiological signals, overcoming interference issues and facilitating accurate health monitoring in wearable devices, comparable to photoplethysmography (PPG) sensors while addressing limitations like device fit and ambient light effects.

Implementation Method 1

a self-oscillating complementary split-ring resonator (SO-CSRR) element, configured to detect a physiological signal and output a modulated signal

Methodology Applied

Scientific EffectResonance: Resonance

Implementation Method 2

based on perturbation and injection-locked theories

Methodology Applied

Scientific EffectPerturbation:

Data Source

PatentUS11439355B2Perturbation-injection-locked physiological signal sensor

Publication Date: 2022.09.13 NAT TAIWAN UNIV OF SCI & TECH

AI summary

A physiological signal sensor, comprising a self-oscillating complementary split-ring resonator (SO-CSRR), a demodulator and a microcontroller (MCU). The SO-CSRR detects a physiological signal and outputs a modulated signal, the demodulator receives the modulated signal and outputs a pulse physiological signal, the baseband amplifier receives the pulse physiological signal and outputs an amplified pulse physiological signal, and the MCU receives the amplified pulse physiological signal and outputs a digital signal.