# How do I perform envelop on a time signal

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Osasu on 25 Jul 2013
Edited: Lisa Justin on 15 Apr 2014
I have a vibration time signal from .lvm file I want to perform envelop on. Any ideal of the code to use? I want to use the result for worm gear fault detection.
I am particularly interested in the high frequency region.
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### Answers (2)

Youssef Khmou on 25 Jul 2013
hi,you have Analog methods :
1. Frequency Modulation :
Fs = 8000; % Sampling rate of signal
Fc = 3000; % Carrier frequency
t = [0:Fs]'/Fs; % Sampling times
s1 = sin(2*pi*300*t)+2*sin(2*pi*600*t); % Channel 1
s2 = sin(2*pi*150*t)+2*sin(2*pi*900*t); % Channel 2
x = [s1,s2]; % Two-channel signal
dev = 50; % Frequency deviation in modulated signal
y = fmmod(x,Fc,Fs,dev); % Modulate both channels.
z = fmdemod(y,Fc,Fs,dev); % Demodulate both channels.
2. Amplitude Modulation :
% Sample the signal 100 times per second, for 2 seconds.
Fs = 100;
t = [0:2*Fs+1]'/Fs;
Fc = 10; % Carrier frequency
x = sin(2*pi*t); % Sinusoidal signal
% Modulate x using single- and double-sideband AM.
ydouble = ammod(x,Fc,Fs);
ysingle = ssbmod(x,Fc,Fs);
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Lisa Justin on 15 Apr 2014
Edited: Lisa Justin on 15 Apr 2014
x = 1:100;
y1 = rand(1, 100);
y2 = rand(1, 100);
y3 = rand(1, 100);
joined = cat(1, y1, y2, y3);
env_max = max(joined, [], 1);
env_min = min(joined, [], 1);
plot(x, joined);
hold('on');
plot(x, env_max, 'k');
plot(x, env_min, 'k');
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