Wearable ECG Clipping Detection With Adaptive Gain Control
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Solution Overview
Problem
Wearable medical devices face signal distortion due to analog clipping in ECG signal amplification, leading to unreliable signal processing and potential false alarms or missed arrhythmia detections, which can result in unnecessary shocks or failure to treat cardiac conditions.
Innovation Solution
A wearable medical device with a programmable attenuation/gain stage and an analog clipping detection and control unit that monitors digitized ECG signals to prevent clipping by adjusting attenuation based on voltage levels, ensuring reliable signal processing and preventing distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If multiple amplifier stages are used to maximize signal-to-noise ratio, then noise reduction is improved, but signal clipping distortion increases
Solution Approach 1:
The patent applies preliminary action by detecting the voltage level at each amplifier stage before clipping occurs and proactively adjusting the gain in advance. The detection circuit monitors the analog ECG signal voltage levels, and when a threshold is approached, the gain is reduced before clipping can happen, preventing distortion while maintaining signal-to-noise ratio benefits of multiple amplification stages.
Solution Approach 2:
The patent implements feedback by using the digitized ECG signal to monitor voltage levels and automatically adjusting the gain of amplifier stages. The control circuit receives feedback about signal levels and dynamically modifies amplification parameters to prevent clipping while maintaining optimal noise reduction, creating a closed-loop system that balances these conflicting requirements.
2Reliability
If gain is increased to amplify weak ECG signals, then signal amplitude is improved, but clipping threshold is exceeded causing distortion
Solution Approach 1:
The patent applies dynamics by making the gain of amplifier stages variable rather than fixed. The system dynamically adjusts gain based on real-time signal conditions, increasing amplification when signals are weak to improve detectability, and reducing gain when signals approach clipping thresholds to prevent distortion, thus adapting to changing signal levels.
Solution Approach 2:
The patent implements parameter changes by modifying the gain parameter of amplifier stages based on detected voltage levels. When the ECG signal amplitude is low, the gain parameter is increased to boost signal strength; when voltage approaches the clipping threshold, the gain parameter is reduced to prevent distortion, thus dynamically optimizing signal quality.
3Reliability
If automatic gain control is implemented to prevent clipping, then signal quality is improved, but device complexity increases
Solution Approach 1:
The patent applies merging by combining the clipping detection function with the existing analog-to-digital converter and control circuitry. Rather than adding a completely separate detection system, the invention utilizes the digitized signal from the ADC to monitor voltage levels and control gain, integrating multiple functions into existing components to minimize added complexity.
Solution Approach 2:
The patent implements multi-functionality by using the digitized ECG signal for multiple purposes: both for clinical analysis and for monitoring voltage levels to prevent clipping. The control circuit that manages amplifier gain is also responsible for overall signal processing coordination, reducing the need for dedicated separate circuits and minimizing device complexity.
Data Source
AI summary
A wearable medical device and method of detecting clipping of ECG signals is disclosed. In one embodiment, the wearable medical device comprises a plurality of ECG sensing electrodes configured to sense an ECG of a patient and an ECG acquisition circuit electrically coupled to a pair of the plurality of ECG sensing electrodes and configured to provide an amplified and conditioned analog ECG signal, a programmable attenuation/gain stage electrically coupled between a first gain stage and a second gain stage, an ADC electrically coupled to the ECG acquisition circuit to receive and digitize the amplified and conditioned analog ECG signal and provide a digitized ECG signal, and a signal conditioning and control unit electrically coupled to the ECG acquisition circuit and the ADC to receive and monitor the digitized ECG signal and to detect clipping of the amplified and conditioned analog ECG signal based upon the digitized ECG signal.