An Adaptive Noise Canceller for Fluctuated Frequency Power Line Interference in Cardio Signal
The electrocardiogram (ECG) is indispensable during the measuring procedure of the cardio-electrical system performance. The ECG is generated by sensing the electrical impulses, that is generated by polarization and depolarization of cardiac tissue, and then mutates them into a waveform. The amplitude range of the ECG signal is very weak (about 1mV) which leads to a great concern about its corruption by different environmental noise sources. Some of these sources originated from power lines at certain frequencies which are known as the Power Line Interference (PLI). The fixed notches analogue and digital filtering techniques are used overwhelmingly to overcome this unwanted PLI involvement. Unfortunately, when frequency and/or phase of the power line humming are unsteady, then those techniques are incapable to extract ECG signals from their corrupted versions. Adaptive filter techniques; which characterized by the self-modifying property of its frequency response; are qualified for tracking the aforementioned deviations of frequency (50/60 Hz) and/or phase of PLI. In this paper, we utilized an Adaptive Noise Canceller (ANC) that is based on adaptive filtering for ECG signals extraction under inconstant PLI characteristics environment. Adaptive filter based on LMS and NLMS algorithms have been investigated with a deviation of 3Hz in PLI frequency. The simulation results show a good outperforming of adaptive filtering in tracking the change of PLI conduct.