Amplitude Modulation & spectrum analysis using fft | MATLAB

%Code:

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%Generating message signal of 10 Hz frequency

%sampling frequency=1000 Hz , modulation index=0.5

%carrier frequency=100Hz

Ts=1/1000;%Sampling Time

t=0:1/1000:3;%Time sample range of input signal

m=sin(2*pi*10*t);%Input Signal

plot(t,m);%plot the signal

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%Single sided spectrum

N=length(t);

y=fft(m,N);

z=y(1:(floor(N/2)+1));

k=0:(floor(N/2));

stem(k,abs(z));

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%Verifying the message signal frequency from the figure window

digital_frequency_in_rad=(2*pi/N)*30;

analog_frequency_in_rad=digital_frequency_in_rad/Ts;

analog_frequency_in_Hertz=analog_frequency_in_rad/(2*pi);

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%Modulation

s=10*(1+0.5*m).*sin(2*pi*100*t);%AM= Ac[1+ma*m(t)]sin2?fct

plot(t,s);

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%Spectrum of modulated signal

N=length(t);

y=fft(s,N);

z=y(1:(floor(N/2)+1));

k=0:(floor(N/2));

stem(k,abs(z));

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%Verifying the frequency components present in the modulated wave

k=[270 300 330];

digital_frequency_in_rad=(2*pi/N)*k;

analog_frequency_in_rad=digital_frequency_in_rad/Ts;

analog_frequency_in_Hertz=analog_frequency_in_rad/(2*pi);