Created
July 19, 2020 13:46
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Write a code in MATLAB to obtain output form the expression for the amplitude modulation (DSB-C) signals, where message signal is m(t)=5 sin(2 π 100t) and carrier signal c(t)= 10 sin(2 π 1500t).
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%DSB-SC modulation | |
Am=5; %amplitude of message signal | |
Ac=5; %amplitude of carrier wave | |
fm=100; %frequency of message signal(Hz) | |
fc=1500; %frequency of carrier wave (Hz) | |
F=10000; %sampling frequency (Hz) | |
T=1/F; | |
t=0:T:0.1; %time vector | |
%1.Message signal | |
figure(1); | |
subplot(311); %plot at 1st position in a 3-by-1 grid | |
m=Am*sin(2*pi*fm*t); | |
plot(t,m); xlabel('t(sec)'); ylabel('m(t)'); | |
title('Message signal Vs Time'); | |
%Spectrum of message signal | |
n=length(m); %length returns period of the message signal | |
M=fftshift(fft(m,n)); | |
%zero-centered fast fourier transform | |
f=F*[-n/2:n/2-1]/n; %zero-centered frequency range | |
figure(2); | |
subplot(311); | |
plot(f,abs(M));xlabel('f(Hz)'); ylabel('M(f)'); | |
title('Spectrum of Message signal'); | |
%2.Carrier wave | |
c=Ac*sin(2*pi*fc*t); | |
figure(1); | |
subplot(312); %creates axis at 2nd place on a 3-by-1 grid | |
plot(t,c); xlabel('t(sec'); ylabel('c(t)'); | |
title('Carrier signal Vs Time') | |
%Spectrum of carrier wave | |
N=length(c); | |
C=fftshift(fft(c,N)); | |
f=F*[-N/2:N/2-1]/N; | |
figure(2); | |
subplot(312); | |
plot(f,abs(C)); xlabel('f(Hz)'); ylabel('C(f)'); | |
title('Spectrum of Carrier wave'); | |
%3.DSB-SC modulation | |
x_dsbsc=m.*c; %DSB-C signal | |
figure(1); | |
subplot(313); %creates axis at 3rd place on a 3-by-1 grid | |
plot(t,x_dsbsc);xlabel('t(sec)'); ylabel('x_d_s_b_-_s_c(t)'); | |
title('DSB-SC signal Vs Time'); | |
%Spectrum of DSB-SC modulated signal | |
l=length(x_dsbsc); | |
X_dsbsc=fftshift(fft(x_dsbsc,l)); | |
figure(2); | |
subplot(313); | |
plot(f,abs(X_dsbsc)); xlabel('f(Hz)');ylabel('X_d_s_b__s_c(f)'); | |
title('Spectrum of DSB-SC modulated signal'); | |
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