Real-Time Hybrid PLI Filtering for Analog ECG Signals

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Solution Overview

Problem

Existing methods for removing power line interference (PLI) from electrocardiograms (ECG) signals are inefficient in real-time, causing delays that affect the accuracy of synchronous pacing and ECG signal analysis.

Innovation Solution

A hybrid PLI filter that estimates PLI digitally and cancels it analogously in real-time, using a predictive or feedback loop method to suppress PLI harmonics with minimal delay, implemented using circuitry with a microprocessor and differential amplifiers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If digital filtering methods are used to remove power line interference from ECG signals, then PLI suppression is achieved, but time delay occurs affecting synchronous pacing accuracy

Engineering Contradiction:

Improvepower line interferenceVSAvoidsignal processing delay

Core Design Contradiction:

Object-affected harmful factorsVSLoss of time

Solution Approach 1:

The patent replaces traditional digital filtering methods with an analog adaptive filtering system. The analog filter uses a voltage-controlled oscillator (VCO) tuned to the power line frequency (50/60 Hz) to generate a reference signal, which is then processed through analog circuitry to cancel PLI from the ECG signal in real-time without the time delays inherent in digital sampling and processing.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent dynamically adjusts the frequency and phase parameters of the reference signal generated by the VCO to match the actual power line interference characteristics. This adaptive parameter adjustment allows the analog filter to maintain effective PLI suppression while responding to frequency drifts in the power line signal, achieving both suppression and real-time performance.

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If digital sampling and buffering methods are used for PLI removal, then interference filtering is possible, but processing complexity and time delay increase

Engineering Contradiction:

Improvepower line interferenceVSAvoidsignal processing system

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent replaces complex digital signal processing algorithms with simpler analog circuit implementations. The adaptive filtering is achieved through analog components including VCO, phase-locked loops, and analog multipliers, which naturally perform the filtering function without requiring microprocessors, memory buffers, or complex computational algorithms.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The analog adaptive filtering system is self-regulating, automatically tracking and adapting to power line frequency variations through the phase-locked loop mechanism. The system continuously adjusts its own parameters (frequency and phase of reference signal) based on the detected PLI characteristics, eliminating the need for external control software or complex processing logic.

Inventive Principle:

Principle #25Self-service

3Speed

If traditional analog filtering is used, then real-time processing is achieved, but PLI suppression effectiveness is insufficient

Engineering Contradiction:

Improvesignal processing speedVSAvoidpower line interference

Core Design Contradiction:

SpeedVSObject-affected harmful factors

Solution Approach 1:

The patent incorporates a phase-locked loop (PLL) feedback mechanism that continuously monitors the power line interference signal and adjusts the VCO frequency and phase to maintain precise locking. This feedback ensures that the reference signal generated by the VCO remains synchronized with the actual PLI, enabling effective suppression even when power line frequency drifts occur, while maintaining real-time processing capability.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent transforms the static analog filter into a dynamic adaptive system. The VCO frequency and phase are continuously adjusted in real-time to match the varying PLI characteristics. This dynamic adaptation allows the analog filter to maintain high PLI suppression effectiveness despite changes in power line frequency, overcoming the limitation of fixed-frequency analog filters.

Inventive Principle:

Principle #15Dynamics

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

Achieves significant PLI suppression in real-time, improving T-wave identification and reducing noise levels in ECG signals for accurate pacing and analysis.

Implementation Method 1

a differential amplifier configured to cancel the PLI from the ECG signal

Methodology Applied

Scientific EffectSignal cancellation through differential amplification:

Data Source

PatentUS20250302359A1Filtering power line noises from analog electrophysiological signals in real-time

Publication Date: 2025.10.02 BIOSENSE WEBSTER (ISRAEL) LTD

AI summary

A power line interference (PLI) suppression method includes receiving an input analog signal superimposed with PLI, and digitally estimating one or more harmonics of the PLI in real-time. Responsively to the one or more digitally estimated harmonics, one or more analog harmonic waveforms are outputted, that match the respective one or more harmonics of the PLI. The input analog signal and the one or more analog harmonic waveforms are received, and the superimposed PLI in the input analog signal is suppressed using the one or more analog harmonic waveforms. An analog output signal is outputted, that corresponds to the input analog signal having the suppressed PLI.