Hi Everyone, I faced a problem to apply Wavelet for extraction ECG fetal Signal I know there are three steps you have to do which are :
1- Transform the noisy ECG mother and fetal signal to wavelet domain for finding DWT coefficients of each level (sub band).
2- Apply thresholding to obtain the estimated wavelet coefficients for each level. but i d'ont have a thresholding functions for detect ECG fetal .
3- Reconstruct the ECG signal which have the estimated wavelet coefficients by inverse DWT.
please I am looking for your help.
code :
Fs = 4e3;
Time = 40;
NumSamp = Time * Fs;
%% Mom's Heartbeat
% In this example, we shall simulate the shapes of the electrocardiogram
% for both the mother and fetus. The following commands create an
% electrocardiogram signal that a mother's heart might produce assuming
% a 4000 Hz sampling rate. The heart rate for this signal is approximately
% 89 beats per minute, and the peak voltage of the signal is 3.5 millivolts.
x1 = 3.5*ecg(2700).'; % gen synth ECG signal
y1 = sgolayfilt(kron(ones(1,ceil(NumSamp/2700)+1),x1),0,21); % repeat for NumSamp length and smooth
n = 1:Time*Fs';
del = round(2700*rand(1)); % pick a random offset
mhb = y1(n + del)'; %construct the ecg signal from some offset
t = 1/Fs:1/Fs:Time';
subplot(3,2,1); plot(t,mhb);
axis([0 2 -4 4]);
grid;
xlabel('Time [sec]');
ylabel('Voltage [mV]');
title('Maternal Heartbeat Signal');
%% Fetus Heartbeat
% The heart of a fetus beats noticeably faster than that of its mother,
% with rates ranging from 120 to 160 beats per minute. The amplitude of the
% fetal electrocardiogram is also much weaker than that of the maternal
% electrocardiogram. The following series of commands creates an electrocardiogram
% signal corresponding to a heart rate of 139 beats per minute and a peak voltage
% of 0.25 millivolts.
x2 = 0.25*ecg(1725);
y2 = sgolayfilt(kron(ones(1,ceil(NumSamp/1725)+1),x2),0,17);
del = round(1725*rand(1));
fhb = y2(n + del)';
subplot(3,2,2); plot(t,fhb,'m');
axis([0 2 -0.5 0.5]);
grid;
xlabel('Time [sec]');
ylabel('Voltage [mV]');
title('Fetal Heartbeat Signal');
sig_mix=fhb+mhb;
%%DWT
sig1=sig_mix
OPsig=wden(sig1,'rigrsure','s','sln',6,'sym7');
[CA,CD] = wavedec(OPsig,6,'sym7');
A=CA;
P = thselect(CA,'rigrsure');
CA = wthresh(CA,'h',P);
AA=CA;
Csig = waverec(CA,CD,'sym7');
figure()
subplot(211)
plot(Csig,'r')
subplot(212)
plot(sig_mix,'b')
