supress high amplitude signal and only keep low amplitude

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Rahul
Rahul 2013-3-4
i have a continuous positive signal which has a wave of high amplitude followed by a low aplitude i want to supress the high amplitude wave completely and only keep low amplitude signal
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Youssef Khmou
Youssef Khmou 2013-3-5
编辑：Youssef Khmou 2013-3-5
hi,@Wayne and @Juan : the Amplitudes are Completely added only if the signals have the same Frequency and same phase .
I reproduce Wayne s example ( modified ) :
t = 0:0.001:1-0.001;
x = 2*cos(2*pi*100*t);
y = 4*cos(2*pi*100*t-pi/8);
z = x+y;
plot(t,z)
x and y have the same Freq, but y contains a delay phase (pi/8) then Max(Z)=5.69 not 6 v .
Juan Camilo Medina
Juan Camilo Medina 2013-3-5
编辑：Juan Camilo Medina 2013-3-5
OK, if the phases are different, the result is not exactly the same wave with amplitude equal to the sum of the other two waves. But still, the result is a "single" wave with the same frequency but shifted and different amplitude. If that is what you have, try a Fourier type sine-cosine basis functions decomposition:
t = 0:0.001:1-0.001;
a=5; phi=-1/8; f=10;
x = a*sin(2*pi*f*t+phi); % origial"mixed" wave
figure(1); clf; plot(t,x); hold on;
% decomposition into fourier basis functions
y = (a*sin(pi/2+phi))*sin(2*pi*f*t);
z = (a*sin(phi))*cos(2*pi*f*t);
plot(t,y+z,'--r')

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Juan Camilo Medina
If they oscillate at different frequencies, you can create a high-pass filter, just read the help for the functions
[B,A] = butter(N,Wn,'high'); % this is just one of many filters types
Y = filter(B,A,X); % where X is your signal

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