Question

Q: In MATLAB, make time-domain graphs of a Conventional DSB AM signal u(t) = A_c[1 + am(t)]cos(2×π×f_c×t), with A_c = 1, m(t) = cos(2×π×f_m×t), f_c = 1 kHz, f_m = 50 Hz, for four cases of AM modulations: a = 0, a = 0.3, a = 1, a = 1.3. Your graphs should be over four periods of the message (i.e., 0 < t < 4/fm). Include your code in your solution as well as the four graphs.

Answer 1

MATLAB CODE

clc;
clear all

fm=50;
t=0:1e-4:4/fm; % Time Axis
Ac=1; % Initial Values
a1=0;
fc=1e3;
m_t=cos(2*pi*fm*t);
u1=Ac*(1+a1*m_t).*cos(2*pi*fc*t); % Equation
figure(1)
plot(t,u1); % Plots

title('DSB-SC MODULATION IN TIME DAOMAIN a=0');
xlabel('time (sec)');
ylabel('amplitude');
% a=0.3;
a2=0.3;
u_2=Ac*(1+a2*m_t).*cos(2*pi*fc*t);
figure(2)
plot(t,u_2);

title('DSB-SC MODULATION IN TIME DAOMAIN a=0.3');
xlabel('time (sec)');
ylabel('amplitude');
% a=01;
a3=1;
u_3=Ac*(1+a3*m_t).*cos(2*pi*fc*t);
figure(3)
plot(t,u_3);

title('DSB-SC MODULATION IN TIME DAOMAIN a=1');
xlabel('time (sec)');
ylabel('amplitude');
% a=1.3;
a4=1.3;
u_4=Ac*(1+a4*m_t).*cos(2*pi*fc*t);
figure(4)
plot(t,u_4);

title('DSB-SC MODULATION IN TIME DAOMAIN a=1.3');
xlabel('time (sec)');
ylabel('amplitude');

PLOTS