Wearable ECG Signal Clipping Detection With Programmable Attenuation
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Solution Overview
Problem
Wearable medical devices, such as defibrillators, face signal distortion due to analog clipping in ECG signal amplification, leading to unreliable signal processing and potential false 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 detect clipping, adjust attenuation, and prevent signal distortion by marking or attenuating the signal when approaching a clipping threshold, ensuring reliable signal processing.
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 susceptibility worsens
Solution Approach 1:
The patent implements a feedback mechanism where the system continuously monitors the amplified ECG signal for clipping conditions and dynamically adjusts the attenuation setting in response. The processor detects when clipping occurs and sends control signals to modify the attenuation level, creating a closed-loop system that automatically prevents clipping while maintaining optimal signal-to-noise ratio through multiple amplifier stages.
Solution Approach 2:
The patent employs dynamic attenuation control where the attenuation level is not fixed but can be adjusted in real-time based on signal conditions. The programmable attenuator's setting is modified dynamically in response to detected clipping conditions, allowing the system to adapt its gain structure to prevent clipping while preserving the benefits of multiple amplification stages for noise reduction.
2Measurement precision
If amplification gain is increased to maximize signal amplitude, then signal detection capability is improved, but clipping threshold is exceeded
Solution Approach 1:
The system uses feedback to monitor the amplified signal level and automatically adjusts the attenuator setting when clipping is detected. The processor analyzes the digitized signal for clipping conditions and sends control signals back to the attenuator to reduce gain, ensuring the signal remains within acceptable levels while maintaining detection capability through the feedback-driven adjustment.
Solution Approach 2:
The patent applies preliminary attenuation before the signal enters the multiple amplifier stages. By setting an initial attenuation level that pre-prevents clipping conditions, the system can safely apply high amplification gains without risking signal distortion. This preliminary action creates a headroom that allows aggressive amplification while maintaining signal integrity.
3Reliability
If attenuation is increased to prevent clipping, then signal quality is maintained, but signal-to-noise ratio deteriorates
Solution Approach 1:
The patent implements dynamic attenuation control where the attenuation level is adjusted in real-time based on signal conditions rather than being fixed. The system starts with low attenuation to preserve signal-to-noise ratio and only increases attenuation when clipping conditions are detected, maintaining optimal signal quality without unnecessary noise degradation.
Solution Approach 2:
The feedback mechanism ensures attenuation is applied only when necessary. The system monitors the amplified signal and automatically increases attenuation settings in response to detected clipping, rather than applying constant high attenuation. This feedback-driven approach maintains signal-to-noise ratio by minimizing attenuation while preserving signal quality through selective application.
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 to 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.