How to stimulate an FM modulator?
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For an assignment I've got to stimulate an FM modulator I did that part
But I need help to find the "MINIMUM MODULATOR INDEX WHEN THE POWER OF THE CARRIER FREQUENCY IS REDUCED TO ZERO(BELOW 0.01)"
here is the code which I did.
%code bigins
close all;
clear all;
fc = 100;%carrier frqncy
Fs = 1024;%sampling rate
fm=1;%modulating frqncy
Ts=1/Fs;%sample period
t=[0:Ts:120];%observation period
m=cos(2*pi*fm*t);%modulating signal
beta=0.5;%modulating index
theta=2*pi*fc*t+2*pi*beta*cumsum(m)*Ts;%integral signal
s=cos(theta);
FFTsize =4096;
S=spectrum(s,FFTsize);%s(401) is the power of the carrier
Freq=[0:Fs/FFTsize:Fs/2];
subplot(2,1,1),plot(t,s),xlabel('Time(ms)'),ylabel('Amplitude');
axis([0 0.5 -1.5 1.5]),grid on
subplot(2,1,2),stem(Freq,sqrt(S/682))
xlabel('Frequency (kHz)'),ylabel('Amplitude Spectrum');
axis([95 105 0 1]),grid on
for i = 0:5;
betai = i;
thetai=2*pi*fc*t+2*pi*betai*cumsum(m)*Ts;%integral signal
si=cos(thetai);
FFTsize =4096;
Si=spectrum(si,FFTsize);%s(401) is the power of the carrier
Freq=[0:Fs/FFTsize:Fs/2];
figure;
stem(Freq,sqrt(Si/682)); axis([99.9 100.1 0 1.05]);
end
%code is over
By using the code I got the power of carrier frequency when the modulation index is 0,1,2,3,4 and 5 in six different figures(that's what the code does).
What i want to do is to plot the data I've got from those six different figures in a same modulation index(X-axis) vs power of carrier frequency(Y-axis) graph.
Thank you in advance
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