How do I perform envelop on a time signal

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.

Answer 1

[Youssef Khmou]

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);

Answer 2

[Lisa Justin]

see http://www.mathworks.se/matlabcentral/answers/47237-how-to-create-an-envelop-from-three-graphs

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');