Removing Power Line Interference from ECG Signal

Base paper: - http://www.ipcsit.com/vol47/027-ICCTS2012-T30009.pdf
Noise Analysis & QRS Detection in ECG Signals
International Proceedings of Computer Science and Information Technology.
Abstract:
With the latest advancements in electronics, several techniques are used for removal of unwanted
entities from signals especially that are implied in the most sophisticated applications. The removal of
power line interference from most sensitive medical monitoring equipment can also be removed by
implementing various useful techniques. The power line interference (50/60 Hz) is the main source of
noise in most of bio-electric signals. The thesis report presents the removal of power line interference
and other single frequency tones from ECG signal using the advanced adaptive filtering technique with
LMS (least mean square) algorithm. The thesis is based on digital signal processing (DSP) techniques with
MATLAB package, with the emphases on design of adaptive LMS algorithm. The adaptive interference
removal technique can be used for removal of power line interference in various potential applications
such as recording Electrocardiograms (ECG), Electroencephalogram (EEG) and Electromyogram (EMG).
MATLAB package will be used in the thesis work which is a powerful tool for the interactive design in
most of the scientific applications and complex engineering calculations.
As an additional in order to achieve the goal of thesis it will also be investigated and implemented for
the removal of harmonics (hum) and high frequency noise from ECG signal by using general notch
rejection filters, which are partial milestone for the thesis.

A: - Removal of Power Line Interference (50 Hz) from ECG Signal by LMS Algorithm
FilterTap = 16
mu = 0.005

FilterTap = 16
mu = 0.009

FilterTap = 32
mu = 0.005

FilterTap = 32
mu = 0.009

B: - Removing of Harmonics and High Frequency Noise from Original ECG Signal
Conclusions:
This report is devoted to the problems and solutions on removal of Power Line Interference and other
Single Frequency Tones from Signals. The understanding of noise cancellation from ECG signal was
explained clearly to the readers, the methods and techniques applicable to be used discussed
throughout the report. It has been proposed a solution for the power line interference its respective
harmonics and high frequency noise interferences from original ECG signal. The results have been
obtained which were required in purpose statement of the report.
In general FIR filters are used because these types of filters have simple architecture and are logically
stable, so the FIR filter was chosen for the development of the system. The research has been made for
the selection of filters and algorithm, two kind of adaptive filters i.e. FIR (Finite impulse response) & IIR
(Infinite impulse response) and two kinds of algorithms, the LMS (least mean square) & RLS (recursive
least squares) algorithms were studied and examined. The LMS algorithm is the most widely used
adaptive filtering algorithm in biomedical monitoring equipment, so it was decided to be employed for
the thesis to get the required solution for the main purpose. The applications of the LMS algorithm can
be implemented due to its simplicity and robustness.
An adaptive filter is used in applications that require different filter characteristics in response to
variable signal conditions. The speed of adaptation and accuracy of the noise cancellation after
adaptation are important measures of performance for noise cancellation algorithm. The goal of the
adaptive filter is to match the filter coefficients to the noise so that the adaptive filter can subtract the
noise out from signal. So adaptive filtering technique was selected to achieve the goal of thesis.
The test for the simulation of ECG signal has been taken. The signal is corrupted by power line
interference of 50 Hz. It is observed that the frequency of the power line interference is 50 Hz which is
then mixed with original ECG signal, it is also examined that the mixed signal is displayed on the plot.
After passing through LMS algorithm the filtered output is nearly same as the input signal with some
acceptable distortion range. The value of step size μ play an important role in determining the
convergence speed, stability and residual error after convergence. The convergence rate was controlled

by Removal of Power Line Interference and other Single Frequency Tones from Signals MSc Thesis
Report, Mälardalen University, Sweden
56
LMS step size μ. The ECG signal graphs described in the simulation results verify the adaptation of the
LMS adaptive algorithm by changing various parameters like step size, convergence value (μ) and filter
taps have various effects on the output graphs. The result shows that LMS is an effective algorithm used
for the adaptive filter in the noise cancellation implementation.
By increasing the filter order it shows a convergence rate but makes the results more precise and by
decreasing the step size value it creates the slower convergence but improves the stability and accuracy.
The recovered signal closely resembles to the original simulated signal minus the noise. It can be seen
that the implementation of the algorithm functions as correctly and efficiently. By comparing the graphs
of the input signal of ECG and output signal, it is noticed that the simulation program performs
satisfactorily and that noise cancellation from original ECG signal is acquired. The overall performance of
LMS algorithm for power line interference is achieved.
Furthermore the general notch rejection filters method also performs the correct operation while
filtering the noise from original ECG signal. This technique for the investigation, implemented and
analysis of removal of harmonics and high frequency noise from original ECG signal performed
satisfactory. It is concluded that the low frequency noise (hum) and high frequency noise can be
removed from original ECG signal by the implementation of general notch rejection filters method and
the desired result can be achieved accurately.
Future Enhancements:
The depth knowledge achieved is in a number of aspects by using digital signal processing techniques
with MATLAB package for medical monitoring equipment (ECG). It provides the real concepts along with
the theoretical backgrounds of removal of power line interference, single frequency tones and high
frequency noise from original ECG signal. This enhances the understanding and self-confidence in the
field of electronics and biomedical engineering.
In the thesis, the adaptive signal processing filtering technique based on LMS algorithm could be
implemented for more signals and also improvement of the thesis can be further implemented with
different algorithms such as NLMS and RLS to achieve the desired results. It could also be investigate
and implement the removal of multiple of harmonics from ECG signal. In further research it would be of
interest to make a broader study and look at some companies for related project for the
implementation.
References:
[1] Stacy Finlay, Carrie Klekta and Ernie Packulak, Adaptive Noise Cancellation for ECG Signal, 2002
[2] http://en.wikipedia.org/wiki/Adaptive_filter Accessed on 2008-11-22
[3] Rolf Limacher, Removal of power line interference from the ECG signal by an Adaptive digital filter,
ETH Zurich, laboratory of Electrical Engineering Design Gloriast, Zurich
[4] Applications of Adaptive Filtering to ECG Analysis, Noise Cancellation and Arrhythmia Detection
Nitish V . Thakor, Seiiior Member, IEEE, and Yi-Sheng Zhu, Se~iior Momher, IEEE
[5] http://www.eng.nus.edu.sg/EResnews/0410/sf/sf_7.html Accessed on 2008-11-23
[6] http://www2.netdoctor.co.uk/health_advice/examinations/ecg.htm Accessed on 2008-09-13

[7] http://www.essortment.com/all/howhumanheart_roua.htm Accessed on 2008-11-23
[8] http://www4.ncsu.edu/~xzhang11/PDF/525_proj1.pdf
[9] Dr. A. Michael Noll, Technological Challenges of Power Line, Feb 5 (2002) California,
Telecommunication, Annenberg School of Communication at the University of Southern Los Angeles.
and Baseline Drift Removal, Depart of Psychology, Second University of Naples,Italy and International
Institute for Advanced Scientific Studies, Italy. Block Approach Harvey Mudd College, California.
[10] Anna Esposito, Pierluigi D. Andria, An Adaptive Learning Algorithm for ECG Noise
[11] John Leis, Digital Signal Processing- A MATLAB-Based Tutorial Approach, Research Studies Press Ltd.
2002
[12] http://www.mathworks.com Accessed on 2008-11-21
[13] Hakan Johansson, Synthesis and Realization of High-Speed Recursive Digital Filters, University of
Linkoping, Sweden, 1998
[14] MATLAB Software help
[15] Philip D. Cha , John I. Molinder , Fundamentals of Signals and Systems, A Building
[16] John G. Proakis, Dimitris G. Manolakis Digital Signal Processing, Principles, Algorithm and
Applications
[17] Emmanuel. C. Ifeachor, Barrie. W. Jervis, Digital Signal Processing
[18] Rahman Jamal, Mike Cerna, John Hanks Designing Filters Using the Digital Filter Design Toolkit
[19] Edward P. Cunningham, Digital Filtering An Introduction, John Wiley & Sons, Inc. 1995
[20] Haykin S, Adaptive Filter Theory, 2nd Edition, United Stated of American: Prentice-Hall, Inc. 1991,
[21] Krister Landernas, Implementation of Digital Filters Using Digital-Series Arithmetics, Department of
electronics, Licentiate thesis No. 23, 2004
66
[22] http://www.dsptutor.freeuk.com/dfilt2.htm
[23] http://www.intersil.com/data/AN/an9603.pdf
*24+ Nicholas John Loy, An Engineer’s Guide to FIR Digital Filters, Prentice Hall, 1988
[25] Andreas Antoniou, Digital Filters Analysis, Design and Applications, Second Edition, McGraw-Hill,
Inc. 1993
[26] B. Widow, "Adaptive noise cancelling: principles and applications", Proceedings of the IEEE, vol. 63,
[28] http://www.dspguru.com/info/terms/filtterm/index2.htm

[30] W. Kenneth Jenkins, Andrew W. Hull, Jeffrey C. Strait, Bernard A. Schnaufer, Xiaohui Li, Advanced
Concept in Adaptive Signal Processing, Kluwer Academic Publisher 1996
[31] Per Sjosten, Adaptive Noise Control Using The LMS Algorithm, Chalmer University of Technology
[32] Maurice G. Bellanger, Adaptive Digital Filters, Second Edition Revised and expanded, Marcel Dekker,
Inc. 2001
[33] Paulo S.R. Diniz, Adaptive Filtering Algorithm and Practical Implementation, Kluwer Academic
Publishers, 1997
[34] Michael S. White and Stuart J. Flockton, Adaptive Recursive Filtering using Evolutionary Algorithms.
Department of Physics, Royal Holloway, University of London.
[35] B. Widrow and S. Stearns. Samuel D. Adaptive Signal Processing. Prentice Hall, Inc,1985
[36] Farhang Boroujeny, B. Adaptive Filters: Theory and Applications. Chichester: John Wiley and Sons,
1998
[37] Treichler, John. R. and Johnson Jr., Richard C. and Larimore, Michael G. Theory and Design of
Adaptive Filters. New York: John Wiley and Sons, 1987
[38] Yuu-Seng Lau, Zahir M. Hussian and Richard Harris, Performance of Adaptive Filtering Algorithms: A
Comparative Study, Centre for Advanced Technology in Telecommunications (CATT), School of Electrical
and Computer Engineering RMIT University, Melbourne, Victoria, Australia.
[39] Ali H. Sayed, Fundamentals of Adaptive Filtering, John Wiley & Sons Inc, 2003
[40] Cedric Keip, Design of a Finite Impulse Response Filter Coefficients Computation Tool Using
Evolutionary Strategies and Extension to Filter Bank Design, 2004
[41] Terrell, Trevor J. Introduction to Digital Filters. Second Edition, London: Macmillan, 1980
[42] C.F.N. Cowan, P.M Grant, Adaptive Filters, United States of America: Prentice Hall, Inc. 1985
[43] Thomas J. Cavicchi, John, Digital Signal Processing, Wiley & Sons, Inc 2000
[44] http://dualist.stanford.edu/~ee265/www-Sept2006/docs/digital_filters.pdf
[45] N. Kalouptsidis. Adaptive System Identification and Signal Processing Algorithm (University of
Athens) and S. Theodoridis (University of Patras) Prentice Hall Inc.,1993.
67
[46] L. Guo, L. Ljung, G.J. Wang, Necessary and Sufficient Condition for Stability of LMS, Department of
Electrical Engineering, Linkoping University, Sweden, 1995
[47] Monson H. Hayes, Jonson. Statistical Digital Signal Processing and Modeling, Wiley & Sons.
[48] Simon Haykin, Adaptive Filter Theory, Fourth Edition, Prentice Hall, Inc 2002
[49] International Journal of Control, Automation, and Systems, vol. 3, no. 1, March 2005
[50] Charles Le and Scott Hensley. RFI removal from AIRSAR polarimetric data, Jet Propulsion Laboratory
California Institute of Technology

[51] Special issue on Adaptive Signal Processing of the International Journal computers & Electrical
Engineering Vol. 18, No. 3/4, 1992.
[52] A. Zaknich, Principles of Adaptive Filters and Self-Learning Systems, Springer
[53] John L. Semmlow, Robert Brunswick, Biosignal and Biomedical Image Processing Matlab-Based
Applications, New Hersey, U.S.A. Rutgers University, Piscataway, New Jersey, U.S.A.
[54] Haykin, S. Adaptive Filter Theory. Third Edition. New Jersey: Prentice-Hall, Inc.1996

Removing Power Line Interference from ECG Signal

Recommandé

Recommandé

Contenu connexe

Tendances

Tendances (19)

Similaire à Removing Power Line Interference from ECG Signal

Similaire à Removing Power Line Interference from ECG Signal (20)

Plus de Harshal Ladhe

Plus de Harshal Ladhe (15)

Dernier

Dernier (20)

Removing Power Line Interference from ECG Signal