Matlab Code For CT

                                       Matlab Code For CT

1)Amplitude Modulation

clear all;close all;clc;

fc=5000;

fs=30000;

N=5000;

Ts=1/fs;

t=(0:Ts:(N+Ts)-Ts);

fm=500;

m=cos(2*pi*fm*t);

mu=0.75;

[f1 m]=T2f(t,m);

[f2 c]=T2f(t,c);

s=(1+mu*m)*c;

[f3 s]=T2f(t,s);

figure();

subplot(3,2,1);

plot(t,m/max(m),'black','linewidth',1.5);

axis([0 0.005 -1.2 1.2]);

xlabel('time(seconds)');

ylabel('amplitude');

title('500hz message signal');

grid on;

subplot(3,2,2);

plot(fs,abs(m/max(m)),'r','linewidth',2);

axis([-8000 8000 -0.001 1.2]);

xlabel('frequencey');

ylabel('magnitude');

title('specturm of message signal');

grid on;

subplot(3,2,3);

plot(t,c/max(c),'b','linewidth',1.5);

axis([0 0.005 -1.2 1.2]);

xlabel('time(seconds)');

ylabel('amplitude');

title('20000hz carrier signal');

grid on;

subplot(3,2,4);

plot(fs,abs(c/max(c)),'m','linewidth',2);

axis([-8000 8000 -0.01 1.2]);

ctitle('specturm of carrier signal');

grid on;

subplot(3,2,5);

plot(t,rear(s/max(m)),'r','linewidth',1.5);

axis([00.005 -1.2 1.2]);

title('AM signal');

xlabel('time(seconds)');

ylabel('amplitude');

grid on;

subplot(3,2,6);

plot(f3,abs(s/max(s)),'b','linewidth',2);

grid on;

axis([-8000 8000 -0.02 1.2]);

xlabel('frequencey');

ylabel('magnitude');

title('spectrum of AM')

2)DSB

close all 

clear all 

clc

t=0:0.000001:0.001;

vm=1;

vc=1;

fm=2000;

fc=50000;

mt=vm*sin(2*pi*fm*t);

subplot(4,1,1);

plot(t,mt);

ct=vc*sin(2*pi*fc*t);

subplot(4,1,2);

plot(t,ct);

subplot(4,1,3);

st=mt.*ct;

hold on;

plot(t,st);

plot(t,mt,'r:');

plot(t,-mt,'r:');

r=st.*ct;

[b a]=butter(1,0.01);

mr=filter(b,a,r);

subplot(4,1,4);

plot(t,mr);

3)SSB

close all

clear all

clc

fs=8000;

fm=20;

fc=50;

Am=1;

Ac=1;

t=[0:0.1*fs]/fs;

subplot(5,1,1);

m1=Am*cos(2*pi*fm*t);

plot(t,m1);

title('message signal');

m2=Am*sin(2*pi*fm*t);

subplot(5,1,2);

c1=Ac*cos(2*pi*fc*t);

plot(t,c1);

title('carrier signal');

c2=Ac*sin(2*pi*fc*t)

subplot(5,1,3);

%Susb=0.5*Am*cos(2*pi*fm*t)*Ac*cos(2*pi*fc*t);

Susb=0.5*m1.*c1-0.5*m2.*c2;

plot(t,Susb);

title('SSB-SC signal with USB');

subplot(5,1,4);

S1sb=0.5*m1.*c1+0.5*m2.*c2;

plot(t,S1sb);

title('SSB-SC signal with LSB');

r=Susb.*c1;

subplot(5,1,5);

[b a]=butter(1,0.0001);

mr=filter(b,a,r);

plot(t,mr);

title('demodulated output');