1. Amplitude modulation with a complex exponential carrier

2. Implementation x x

3. Amplitude modulation with a Sinusoidal carrier

4. Synchronous demodulation

5. Implementation 2 x x
Low pass filter

6. Asynchronous demodulation

7. Synchronous
Asynchronous

8. Synchronous
Asynchronous

9. Asynchronous demodulation

10. Frequency-division multiplexing+ x

11. Frequency-division multiplexing -- demodulation1 1 1 x
Bandpass filter
Low pass filter

12. Single-sideband sinusoidal amplitude modulationx + x

13. Single-sideband sinusoidal amplitude modulationx + x

14. Single-sideband sinusoidal amplitude modulation
double-sideband

15. clear all;
clf;
deltat = 0.001;
T = 1;
t = 0:deltat:20-deltat;
alpha1 = -10;
x1 = exp(alpha1.*t);
wc = 2*pi*10;
y1 = x1.*cos(wc.*t);
dm = 0.01;
om = -16*2*pi:dm:2*16*pi;
for m=1:length(om) % Fourier transmform
Ym = x1.*exp(-j*om(m).*t);
X1m(m) = trapz(t,Ym);
if om(m)>=0
X1pm(m) = j*X1m(m);
else
X1pm(m) = -j*X1m(m);
end
Ym = y1.*exp(-j*om(m).*t);
Y1m(m) = trapz(t,Ym);
for k=1:length(t) %inverse fourier transfrom
Y1k = X1pm.*exp(j*om*t(k));
x1p(k) = trapz(om,Y1k);
x1p = x1p./(2*pi);
y1p = x1p.*sin(wc.*t);
y = y1p+y1;
Ym = y.*exp(-j*om(m).*t);
Ypm(m) = trapz(t,Ym);
plot(t, y1);
hold on
plot(t,real(y1p),'r');
hold off;
figure(2)
plot(om/(2*pi),abs(X1m));
hold on;
plot(om/(2*pi),abs(X1pm),'y');
plot(om/(2*pi),abs(Y1m),'r');
plot(om/(2*pi),abs(Ypm),'g');