Non-Contact Biosignal Sensing With Noise-Canceling Feedback
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Solution Overview
Problem
Existing non-contact biosignal sensing technologies suffer from inadequate sensitivity and unwanted background noise, rendering them unsuitable for detecting acute events and chronic conditions.
Innovation Solution
A non-contact sensing system with a non-contact sensing electrode, differential amplifier, and compensation signal generator circuit that estimates and cancels noise, allowing for increased amplifier gain without saturation, using passive and active feedback impedance to enhance sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If non-contact sensing is used to avoid contact with the subject, then ease of operation and hygiene are improved, but sensitivity and signal quality deteriorate due to inadequate signal strength and background noise
Solution Approach 1:
The patent implements a feedback mechanism where a compensation signal is generated based on the sensed signal and fed back to the amplifier input. This feedback loop actively compensates for background noise and interference, allowing the system to maintain high sensitivity in non-contact mode by continuously adjusting the compensation signal to counteract unwanted noise components.
Solution Approach 2:
The patent introduces a compensation signal as an intermediary element that mediates between the weak biosignal and the noise. This compensation signal acts as a mediator that selectively cancels background noise while preserving the actual biosignal, enabling accurate non-contact measurement without direct contact with the subject.
2Measurement precision
If amplifier gain is increased to improve sensitivity, then measurement precision is improved, but signal saturation occurs due to noise and interference
Solution Approach 1:
The patent converts the harmful effect of background noise into a beneficial compensation mechanism. By analyzing the noise characteristics and generating a compensating signal that mirrors the noise but with opposite polarity, the system transforms the harmful noise into a useful reference that enables noise cancellation, allowing higher gain without saturation.
Solution Approach 2:
The feedback mechanism continuously monitors the amplified signal and adjusts the compensation signal accordingly. This closed-loop control prevents saturation by dynamically balancing the amplified biosignal with the compensation signal, allowing the amplifier to operate at higher gains while maintaining signal integrity and avoiding clipping.
3Measurement precision
If background noise is reduced through filtering, then measurement precision is improved, but signal bandwidth is limited and acute events may be missed
Solution Approach 1:
The patent extracts only the harmful noise components from the signal while preserving the full bandwidth of the biosignal. By using a compensation signal that specifically targets and removes background noise through subtraction, the system achieves high signal-to-noise ratio without applying broad bandwidth filtering that would attenuate important high-frequency acute event signals.
Solution Approach 2:
The compensation signal serves as an intermediary that selectively removes noise without affecting the biosignal bandwidth. This intermediary approach allows the full frequency spectrum to pass through while noise components are canceled out, maintaining the system's ability to detect both gradual and acute events across the complete frequency range.
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 system achieves improved sensitivity and reduced noise, enabling accurate measurement of biosignals such as ECG, EEG, and respiration rates with enhanced signal-to-noise ratio.
Implementation Method 1
a non-contact sensing electrode configured to sense an electric potential and provide a sensor signal at an output of the sensing electrode based on the sensed electric potential
Implementation Method 2
The amplifier is configured to provide an amplified output signal representative of at least one measured biosignal based on the sensor signal and a feedback signal provided to the second input of the amplifier
Data Source
AI summary
An example sensing system includes a non-contact sensing electrode configured to sense an electric potential and provide a sensor signal at an output of the sensing electrode based on the sensed electric potential. The output of the sensing electrode is coupled to a first input of an amplifier. The amplifier is configured to provide an amplified output signal representative of at least one measured biosignal based on the sensor signal and a feedback signal provided to the second input of the amplifier. A compensation signal generator is coupled between the output of the amplifier and the second input. The compensation signal generator is configured to estimate corresponding noise and provide the feedback signal to include a filtered signal representative of the estimated noise to the second input to the corresponding noise at the first input of the amplifier and mitigate saturation of the amplifier.