MATLAB Examples

# Removing High-Frequency Noise from an ECG Signal

This examples shows you how to filter an ECG signal that has high-freqquency noise, and remove the noise by low-pass filtering.

```% Create one period of ECG signal x = ecg(500).'; y = sgolayfilt(x,0,5); Fs = 1000; [M,N] = size(y); % Initialize scopes TS = dsp.TimeScope('SampleRate',Fs,... 'TimeSpan',1.5,... 'YLimits',[-1 1],... 'ShowGrid',true,... 'NumInputPorts',2,... 'LayoutDimensions',[2 1],... 'Title','Noisy and Filtered Signals'); % Design lowpass filter Fpass = 200; Fstop = 400; Dpass = 0.05; Dstop = 0.0001; F = [0 Fpass Fstop Fs/2]/(Fs/2); A = [1 1 0 0]; D = [Dpass Dstop]; b = firgr('minorder', F, A, D); LP = dsp.FIRFilter('Numerator',b); % Design Highpass Filter Fstop = 200; Fpass = 400; Dstop = 0.0001; Dpass = 0.05; F = [0 Fstop Fpass Fs/2]/(Fs/2); % Frequency vector A = [0 0 1 1]; % Amplitude vector D = [Dstop Dpass]; % Deviation (ripple) vector b = firgr('minord', F, A, D); HP = dsp.FIRFilter('Numerator', b); % Stream tic; while toc < 30 x = .1 * randn(M,N); highFreqNoise = HP(x); noisySignal = y + highFreqNoise; filteredSignal = LP(noisySignal); TS(noisySignal,filteredSignal); end % Finalize release(TS) ```