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Hello, I have this signal m(t) = cos(2*pi*t), and the AM signal of m : y = (Ac + m).*cos(2*fc*pi*t).
The first plot is the original signal, the second plot is the AM signal and the last is the envelope of the modulated signal.
I want to get the original signal so I try to do demodulation to AM signal, using z = amdemod(y,fc,fs) and next get the envelope of the demolated singal
but I get again the AM's signal envelope. As you see y axis is in range (1,3) but I want it in range (-1,1) like the orginal signal. I want just to deduct the Ac I added in (Ac + m), to get the original, but with amdemod() I don't get that result.

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 采纳的回答

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I think that by removing the mean (DC offset) of your demodulated signal in figure 3, you will then get your signal within the range (-1,1):
m = m-mean(m);
I would write an amDemod function like this:
function m = amDemod(s,fc,fs,n)
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Function amDemod()
% Goal : Demodulation of an AM signal
% IN : - s : AM modulated signal
% - fc: Carrier signal frequency
% - fs: Sampling frequency
% - n : Number of carrier signal periods
% IN/OUT: -
% OUT : - m : Original demodulated signal
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Rectify the modulated signal
s = abs(s);
% Set the number of samples on which to do the moving average
k = round(n*fs/fc);
% Take the moving average
m = movmean(s,k);
% Remove the DC offset
m = m-mean(m);
end
Hope this helps.

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SINETHEMBA MNGUNI
SINETHEMBA MNGUNI 2020-10-16

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Hi, I need to modulate and demoduate an Audio.wav signal, how can I go about it?

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