scholarly journals Removing mains interference from the mfERG by applying a post-processing digital notch filter: for the good or the bad?

2021 ◽  
Author(s):  
Sven P. Heinrich
Keyword(s):  
Multifocal Electroretinogram ◽  
Notch Filter ◽  
Peak Time ◽  
Post Processing ◽  
Nonlinear Superposition ◽  
Analog To Digital ◽  
Mains Interference ◽  
Digital Notch Filter ◽  
Frequency Components ◽  
Input Range

Abstract Purpose Ideally, the multifocal electroretinogram (mfERG) is recorded without noticeable intrusion of mains interference. However, sometimes contamination is difficult to avoid. A post-processing digital notch filter can help to recover the retinal response even in severe cases of mains interference. While a digital filter can be designed to have little to no impact on peak times, filtering out mains interference also removes the retinal signal content of the same frequency, which may result in a change of amplitude. The present study addressed this issue in the standard first order kernel mfERG. Methods In 24 recordings from routine exams with no perceivable mains interference, the effects of 50-Hz and 60-Hz non-causal digital notch filters on amplitude and peak time were assessed. Furthermore, the effect of filtering on contaminated traces was demonstrated and simulated mains interference was used to provide an example of nonlinear superposition of retinal signal and mains interference. Results mfERG amplitudes were reduced by 0%–15% (median 6%) with the 50-Hz filter and remained virtually unaffected with the 60-Hz filter. Simulations illustrate that spurious high-frequency components can occur in the filtered signal if a strongly contaminated signal is clipped due to a limited input range of the analog-to-digital converter. Conclusion The application of a 50-Hz digital notch filter to mfERG traces causes a mild amplitude reduction which will not normally affect the clinical interpretation of the data. The situation is even more favorable with a 60-Hz digital notch filter. Caution is necessary if the assumption of linear additivity of retinal signal and mains interference is violated.

scholarly journals An approach of adaptive notch filtering design for electrocardiogram noise cancellation

2021 ◽  
Vol 22 (3) ◽  
pp. 1303
Author(s):  
Rahmad Hidayat ◽  
Ninik Sri Lestari ◽  
Herawati Herawati ◽  
Givy Devira Ramady ◽  
Sudarmanto Sudarmanto ◽  
...  
Keyword(s):  
Notch Filter ◽  
Ecg Signal ◽  
Least Mean Square ◽  
Heart Activity ◽  
Frequency Range ◽  
Biomedical Signal ◽  
Nlms Algorithm ◽  
Digital Notch Filter ◽  
Notch Filtering ◽  
Electrocardiogram Ecg

An electrocardiogram (ECG) is a means of measuring and monitoring important signals from heart activity. One of the major biomedical signal issues such as ECG is the issue of separating the desired signal from noise or interference. Different kinds of digital filters are used to distinguish the signal components from the unwanted frequency range to the ECG signal. To address the question of noise to the ECG signal, in this paper the digital notch filter IIR 47 Hz is designed and simulated to demonstrate the elimination of 47 Hz noise to obtain an accurate ECG signal. The full architecture of the structure and coefficient of the IIR notch filter was carried out using the FDA Tool. Then the model is finished with the help of Simulink and the MATLAB script was to filter out the 47 Hz noise from the signal of ECG. For this purpose, the normalized least mean square (NLMS) algorithm was used. The results indicate that before being filtered and after being filtered it clearly shows the elimination of 47 Hz noise in the signal of the ECG. These results also show the accuracy of the design technique and provide an easy model to filter out noise in the ECG signal.

Second-Order IIR Notch Filter Design and Implementation of Digital Signal Processing System

2013 ◽  
Vol 347-350 ◽  
pp. 729-732
Author(s):  
Chun Mei Wang ◽  
Wei Cai Xiao
Keyword(s):  
Signal Processing ◽  
Filter Design ◽  
Processing System ◽  
Audio Signal ◽  
Notch Filter ◽  
Digital Signal ◽  
Interference Filter ◽  
Filter Method ◽  
Signal Processing System ◽  
Digital Notch Filter

In this paper the AC power 50Hz power interference, we use IIR digital notch filter method for industrial frequency interference filter. From the design of IIR digital filter method proceed with, on the IIR digital notch filter simulation, the algorithm deduced, on the fixed-point DSP programming method and overflow handling problems made elaborate incisively, and in digital audio signal processing system has been applied.

scholarly journals Improved Data Preprocessing Algorithm for Time-Domain Induced Polarization Method with Digital Notch Filter

2016 ◽  
Vol 64 (6) ◽  
pp. 2264-2288 ◽  
Author(s):  
Shuang-Chao Ge ◽  
Ming Deng ◽  
Kai Chen ◽  
Bin Li ◽  
Yuan Li
Keyword(s):  
Time Domain ◽  
Notch Filter ◽  
Data Preprocessing ◽  
Induced Polarization ◽  
Polarization Method ◽  
Digital Notch Filter

A Design Method for IIR and FIR Digital Notch Filter Used to sEMG

2012 ◽  
Vol 263-266 ◽  
pp. 184-187
Author(s):  
Lin Li ◽  
Jian Hui Wang ◽  
Shuai Ban
Keyword(s):  
Design Method ◽  
Notch Filter ◽  
Recognition System ◽  
Non Invasive ◽  
Bioelectric Signal ◽  
Digital Notch Filter ◽  
Simulation Results ◽  
And Control ◽  
Better Than ◽  
Semg Signals

Surface electromyography (sEMG) signals, a non-invasive bioelectric signal, can be used for the rehabilitation and control of artificial extremities. But this signal is so weak that the electrical voltages ranging from -5 to +5 mv. In order to eliminate the 50Hz noise included in sEMG and hold details of the signal, IIR50HZ notch filter and FIR 50Hz notch filter are design. The compared simulation results show that the application of FIR 50Hz is better than IIR 50Hz in sEMG patter recognition system.

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