Elimination Of Power Line Interference Research Articles

The commonly used methods for ECG Power-line interference removal

The amplitude of electrocardiogram (ECG) signals is on the millivolt level, and is susceptible to interference from human respiration, muscle tremors, and device circuits during the acquisition process, resulting in baseline drift, electromyographic (EMG) interference, and power line interference. Power line interference is a significant noise source in physiological signal acquisition among these. This article explores several methods to reduce the impact of power frequency interference. By analyzing wavelet transforms, adaptive filtering, and smoothing filters, commonly used methods are evaluated to determine their advantages and limitations. Experimental results show that the smoothed filtering method produces the highest SNR and lowest MSE of the electrocardiogram signal after denoising, resulting in the best denoising effect and thorough filtering. The denoising effect of wavelet transform and adaptive filter is poor. But the different methods for power line interference elimination should be applied according to the data acquisition requirements and equipment performance in response to different situations.

Exact and approximate multiplications for signal processing applications

Approximate computing is an emerging technique that can be used for developing power, area and delay efficient circuits at the cost of loss of accuracy. This paper investigates the possibility of efficient exact multipliers through the use of improved compressors and counters and thereafter deriving approximate multiplier structures to achieve a higher percentage of logic optimization at the expense of the lowest possible error. NAND gate based array structure with reduced complexity is used for generating the partial products for both the exact and approximate multipliers. Two variants of the efficient exact multiplier are proposed. The proposed exact multiplier EM-1 is area and power efficient, whereas EM-2 is delay and energy efficient. Two variants of 4:2 compressors are introduced for developing approximate multipliers. The proposed multipliers excel most of the state-of-the-art existing multipliers in terms of the important performance metrics. The proposed exact and approximate multiplier designs are employed for developing ECG denoising FIR filter for the elimination of power line interference and the corresponding performance improvement is illustrated. Cadence RTL compiler v11.10 with GPDK 45 nm standard cell library is used for the synthesis. The simulation of all the multipliers is done by running a test bench program using modelsim.

Cardiogram baseline wander and power line interference elimination by proficient adaptive-rate FIR filtering

For a successful diagnosis, electrocardiogram (ECG) must be cleaned from the power line interference (PLI) and the baseline wander (BW). In this framework, an adaptive rate linear phase filtering method is suggested. The system parameters adapt automatically by monitoring the incoming signal variations. It adjusts the acquisition rate and the noise-suppressing filter order and renders the filtering of lesser samples by filters of inferior taps compared to the conventional counterparts. The applicability is demonstrated by using the MIT-BIH ECG database. The accuracy of the system is measured in terms of the signal to noise ratio (SNR). Results show that while providing a comparable output quality, the proposed method achieves a two times compression gain and notable computational efficiency over the conventional counterparts. A superior precision of the suggested solution over the state-of-the-art counter equals is also demonstrated.

Power Line Interference Elimination in ECG Signals

The recordings of electrocardiogram (ECG), as an important biological signal which provides a valuable basis for the clinical diagnosis and treatment, are often corrupted by the wide range of artifacts. One important of them is power line interference (PLI). The overlapping interference affects the quality of ECG waveform, leading to the false detection and recognition of wave groups, and thus causing faulty treatment or diagnosis. The study deals with some of the signal processing approaches frequently used for elimination of PLI in ECG signal and compares the accuracy of methods by evaluation of the power of the remaining noise and comparing a filtered ECG signal with an original. The results are compared for three levels of interference and each tested method: Butterworth filter (BF), notch filter, moving average filter (MA), adaptive noise canceller (ANC), wavelet transform (WT) and empirical mode decomposition (EMD).

Methods of Power Line Interference Elimination in EMG Signal

Electromyogram (EMG) recordings are often corrupted by the wide range of artifacts, which one of them is power line interference (PLI). The study focuses on some of the well-known signal processing approaches used to eliminate or attenuate PLI from EMG signal. The results are compared using signal-to-noise ratio (SNR), correlation coefficients and Bland-Altman analysis for each tested method: notch filter, adaptive noise canceller (ANC) and wavelet transform (WT). Thus, the power of the remaining noise and shape of the output signal are analysed. The results show that the ANC method gives the best output SNR and lowest shape distortion compared to the other methods.

Elimination of Power Line Interference in ECG Signal Using Adaptive Filter, Notch Filter and Discrete Wavelet Transform Techniques

An ECG is a biomedical non-stationary signal, which contains valuable information about the electrical activity of the heart. The ECG is very sensitive and a weak signal, hence, it gets corrupted by various types of noise such as power line interference, baseline wander, motion artifacts, muscle contractions, electrode contact noise, etc., that may lead to a misdiagnosis. Among these noise parameters the power line interference is very crucial because noise falls in the ECG bandwidth, i.e. 0.05 Hz to 100 Hz. The article proposes the removal of power line interference (PLI) noise in an ECG signal based on discrete wavelet transform (DWT) and adaptive filtering techniques. The results are compared with the existing notch filter both in time and frequency domain by filter performance parameters like ESD, MSE %PSD and SNR.

Elimination of power line interference from ECG signals using recurrent neural networks.

This study proposed a method for the elimination of 50-Hz power line interference (PLI) in electrocardiogram (ECG) signals, using recurrent neural networks (RNN). The method is to preliminarily train an RNN-based model to obtain the signal pattern of PLI. The ECG signals are then filtered by subtracting the PLI signals extracted by the trained model. The results suggest that the proposed method could significantly relieve the distortion of QRS complex while filtering the ECG signals efficiently. The method was evaluated by comparing with a traditional IIR notch filter and an adaptive filtering method.

An Intelligent Adaptive Filter for Elimination of Power Line Interference From High Resolution Electrocardiogram

Electrocardiogram (ECG) is a non-invasive method to monitor electric activities inside the heart. The signals observed on the surface of human body have very low amplitude, and thus, ECG is highly vulnerable to noise. One of the most devastating noise is power line interference (PLI) and its harmonics, which are interlaced with ECG signal even if the ECG equipment is operated on battery. The problem is further complicated when the frequency of PLI is not static, making the conventional notch filter completely ineffective. High-resolution electrocardiogram (HRECG) is a specialized technique in which higher frequency components present in the ECG signal are observed; here, we need to eliminate the harmonics of PLI as well. In this paper, we propose an intelligent adaptive noise rejection filter, which tracks and eliminates PLI as well as its harmonics. The proposed system can estimate the frequency of PLI and tune the adaptive filter for precise elimination of PLI as well as its harmonics without the requirement of an auxiliary reference input. The proposed system is based on recursive state space model, inherited with less computational complexity and performs well in a non-stationary environment. The proposed system responds well to the ongoing variations in amplitude and frequency of PLI present in the HRECG signal as well as intracardiac signal. The proposed system does not require any reference signal for tracking the PLI and its harmonics, and it is capable to self-adjust its tracking frequency for highly precise filtration of first, third, and fifth harmonics of PLI.

Designing a low-noise, high-resolution, and portable four channel acquisition system for recording surface electromyographic signal

In current years, the application of biopotential signals has received a lot of attention in literature. One of these signals is an electromyogram (EMG) generated by active muscles. Surface EMG (sEMG) signal is recorded over the skin, as the representative of the muscle activity. Since its amplitude can be as low as 50 μV, it is sensitive to undesirable noise signals such as power-line interferences. This study aims at designing a battery-powered portable four-channel sEMG signal acquisition system. The performance of the proposed system was assessed in terms of the input voltage and current noise, noise distribution, synchronization and input noise level among different channels. The results indicated that the designed system had several inbuilt operational merits such as low referred to input noise (lower than 0.56 μV between 8 Hz and 1000 Hz), considerable elimination of power-line interference and satisfactory recorded signal quality in terms of signal-to-noise ratio. The muscle conduction velocity was also estimated using the proposed system on the brachial biceps muscle during isometric contraction. The estimated values were in then normal ranges. In addition, the system included a modular configuration to increase the number of recording channels up to 96.

Power-line interference elimination from ECG in case of non-multiplicity between the sampling rate and the power-line frequency

The paper deals with some aspects of the subtraction procedure, which removes the power-line interference (PLI) without affecting the components intrinsic to ECG. This procedure is based on the following principles: the interference is cancelled in linearly going ECG segments that have near to zero frequency content using moving averaging; the extracted samples are saved in a buffer and are then subtracted from the remaining parts of the signals. The accuracy of the subtraction procedure is analysed and improved in the cases of non-multiplicity between the sampling rate and the rated interference frequency. Extrapolation filters are applied over the buffer samples. Experiments with synthesised and real signals are carried out to assess the filter's stability. The results obtained show that the improved subtraction procedure removes the PL interference from ECG signals regardless of the type of multiplicity, odd or even, between the sampling rate and the power-line frequency.

Elimination of Power Line Interference on Telephone Cables Under Frequency-Varying Conditions

A new method for the elimination of power line interference of potentially time-varying frequency, phase, and amplitude on telephone loops is presented. The proposed method is based on adaptive estimation, and subsequent elimination, of the fundamental and individual harmonic components of the induced power signal and tracking their variations over time. The structure and mathematical formulation of the proposed technique are presented, and its performance is demonstrated in a variety of scenarios. Superior performance of the proposed method over existing techniques is observed throughout all experiments. The proposed algorithm presents a simple and efficient method of elimination of narrowband interference of a potentially nonstationary nature that is suitable for real-time applications due to its structural simplicity.

Subtraction of 16.67 Hz railroad net interference from the electrocardiogram: application for automatic external defibrillators

The widespread application of automatic external defibrillators (AEDs) for treating out-of-hospital cardiac arrest incidents and their particular use at railway stations defines the task for 16.67 Hz power line interference elimination from the electrocardiogram (ECG). Although this problem exists only in five European countries, it has to be solved in all AEDs, which must comply with the European standard for medical equipment requirements for interchangeability and compatibility between rail systems. The elimination of the railroad interference requires a specific approach, since its frequency band overlaps with a significant part of the frequencies in the QRS spectra. We present a method based only on one channel ECG signal processing, which effectively subtracts the interference components. The computation procedure is based on simple signal processing tools, which include: (i) bi-directional band-pass filtering (13–23 Hz) of the analyzed ECG segment; (ii) estimation of adequate linearity thresholds; (iii) frequency measurement and calculation of dynamic interference buffer in linear segments and (iv) phase synchronization and subtraction technique in nonlinear segments. The developed method has proved advantageous in providing sufficient quality of the output interference free ECG signal for seven defined arrhythmia types (normal sinus rhythm, normal rhythm, supraventricular tachicardia, slow/rapid ventricular tachycardia, and coarse/fine ventricular fibrillation), and simulated interferences with constant or variable frequencies and amplitudes, which cover the entire amplitude range of the input channel. The procedure is suitable to be embedded in AEDs as a preprocessing branch, which proves reliable for analysis of ECG signals, thus guaranteeing the specified accuracy of the AED automatic rhythm analysis algorithms.

A nonlinear adaptive method of elimination of power line interference in ECG signals

A new method of elimination of power line noise in electrocardiogram signals is presented. The proposed method employs, as its main building block, a recently developed signal processing algorithm capable of extracting a specified component of a signal and tracking its variations over time. Design considerations and performance of the proposed method are presented with the aid of computer simulations. Superior performance is observed in terms of effective elimination of noise under conditions of varying powerline interference frequency. The proposed method presents a simple and robust structure which complies with practical constraints involved in the problem such as low computational resource availability and low sampling frequency.