ABSTRACT

The electrocardiogram has the considerable diagnostic significance, and applications of ECG monitoring are diverse and in wide use. ECG signal after acquisition contains noises such as power line interference, instrumentation noise, external electromagnetic field interference, noise due to random body movements and respiration movements. These noises can be classified according to their frequency content. It is essential to reduce these disturbances in ECG signal to improve accuracy and reliability. The bandwidth of the noise overlaps that of wanted signals, so that simple filtering cannot sufficiently enhance the signal to noise ratio. The present paper introduces the digital notch filtering to cope with the 50 Hz power line noise interference in the ECG signal. Modern biomedical amplifiers have a very high common mode rejection ratio. Nevertheless, recordings are often contaminated by residual power-line interference. Traditional analogue and digital filters are known to suppress ECG components near to the power-line frequency. FIR filter is used to remove 50 Hz power line noise interference from ECG signals(mixed with 50 Hz power line noise interference) , since it does not introduces phase distortion. A ECG signal (without noise) was mixed with constant 0.5mVp-p noise at different values of PLI frequencies 48,48.5,49,49.5,50,50.5 and 51 Hz, and processed by Band reject filters of stop band bandwidth of 48–52Hz. The order of filter are taken as 500. In this paper the proposed filters were designed using Rectangular, Blackman, Hamming, Hann, Kaiser Window method to remove PLI from ECG. Simulation results are also shown. Performance of filters are analyzed by comparing MSE(mean square error) and SNR(signal to noise ratio) of output ECG signal.