Amplitude modulation & demodulation signal

hey there, can anybody help me .. i had run the code but the graph doesnt want to appear..anybody can help me..thank you

t=linspace(0,0.02,10000);

fc=5000;

fm=200;

fs=40000;

Am=5;

Ac=10;

m=(Am/Ac);

wc=(2*pi*fc*t);

wm=(2*pi*fm*t);

ec=(Ac*sin(wc));

em=(Am*sin(wm));

y=(Ac*(l+m*sin(wm).*sin(wc)));

d=(y.*ec);

dl=(conv(d,exp(-t/0.000795)));

l=10000;

subplot(4,1,1),plot(t(1:1),em(1:1))

xlabel('time(sec)');

ylabel('amplitude in volts(V)');

title('MODULATING SIGNAL');

subplot(4,1,2),plot(t(1:1),ec(1:1))

xlabel('time(sec)');

ylabel('amplitude in volts(V)');

title('CARRIER SIGNAL');

subplot(4,1,3),plot(t(1:1),ec(1:1))

xlabel('time(sec)');

ylabel('amplitude in volts(V)');

title('MODULATED SIGNAL');

subplot(4,1,4),plot(t(1:1),ec(1:1))

xlabel('time(sec)');

ylabel('amplitude in volts(V)');

title('DEMODULATED SIGNAL');

[Ashik Ali]

%%
% $$ %% AM Modulation and Demodulation using Functions in MATLAB
%% Modulation index
h= 60;
%% Time Pereiod of Simulation :
t = linspace(0, 0.2, 100000);
%% Message Signal :
Am = 14;
fm = 200;
ym = Am*cos(2*pi*fm*t);
figure;
subplot(4, 1, 1);
plot(t(1:10000), ym(1:10000));
title('Message Signal');
xlabel('time(t)');
ylabel('Amplitude');
%% Carrier Signal :
Ac = Am/h;
fc = 2000;
yc = Ac*cos(2*pi*fc*t);



subplot(4, 1, 2);
plot(t(1:10000), yc(1:10000));
title('Carrier Signal');
xlabel('time(t)');
ylabel('Amplitude');
%% Modulated Signal :
y = ammod(ym, fc, 100000, 0, Ac);
subplot(4, 1, 3);
plot(t(1:10000), y(1:10000));
title('Modulated Signal');
xlabel('time(t)');
ylabel('Amplitude');
%% Demodulated Signal :
z = amdemod(y, fc, 100000, 0, Ac);
subplot(4, 1, 4);
plot(t(1:10000), z(1:10000));
title('Demodulated Signal');
xlabel('time(t)');
ylabel('Amplitude');
ylim([-10, 10]);

Answer 1

[Star Strider]

‘... the graph doesnt want to appear.’

It wants to appear, however you are not letting it!

The (1:1) subscript reference addresses only one point, that being 1, and since the plot function plots between pairs of points, nothing appears. (Note that ‘l’ is in the wrong place in your code. Put it before it is first used.)

Try this:

subplot(4,1,1),plot(t,em)
xlabel('time(sec)');
ylabel('amplitude in volts(V)');
title('MODULATING SIGNAL');
subplot(4,1,2),plot(t,ec)
xlabel('time(sec)');
ylabel('amplitude in volts(V)');
title('CARRIER SIGNAL');
subplot(4,1,3),plot(t,ec)
xlabel('time(sec)');
ylabel('amplitude in volts(V)');
title('MODULATED SIGNAL');
subplot(4,1,4),plot(t,ec)
xlabel('time(sec)');
ylabel('amplitude in volts(V)');
title('DEMODULATED SIGNAL');

You likely copied the plot calls and pasted them to the subplot calls, so you are plotting the same vector the last three times. You might want to check that.

Answer 2

[LAKSHMI CHAITRA NUNNA]

%**********AMPLITUDE MODULATION AND DEMODULATION***********%

close all;
clear all;
clc;
fs=8000; %SAMPLE FREQUENCY
fm=20; %THREE MESSAGE SIGNAL FREQUENCY
fc=500; %CARRIER FREQUENCY
Am=1; %MESSAGE AMPLITUDE
Ac=1; %CARRIER AMPLITUDE
t=[0:0.1*fs]/fs; %TIME DURATION
m=Am*cos(2*pi*fm*t); 
c=Ac*cos(2*pi*fc*t);
ka=0.5;
u=ka*Am;
s1=Ac*(1+u*cos(2*pi*fm*t)).*cos(2*pi*fc*t);
subplot(4,3,1:3);
plot(t,m);
title('Modulating or Message signal(fm=20Hz)');
subplot(4,3,4:6);
plot(t,c);
title('Carrier signal(fc=500Hz)');
subplot(4,3,7);
plot(t,s1);
title('Under Mod signal');
Am=2;
ka=0.5;
u=ka*Am;
s2=Ac*(1+u*cos(2*pi*fm*t)).*cos(2*pi*fc*t);
subplot(4,3,8);
plot(t,s2);
title('Exact Mod signal');
Am=5;
ka=0.5;
u=ka*Am;
s3=Ac*(1+u*cos(2*pi*fm*t)).*cos(2*pi*fc*t);
subplot(4,3,9);
plot(t,s3);
title('Over Mod signal');
r1=s1.*c;
[b a]=butter(1,0.01); %BUTTERWORTH FILTER
mr1=filter(b,a,r1); %DEPTH OF MODULATION
subplot(4,3,10);
plot(t,mr1);
title('DeModulated signal');
r2=s2.*c;
[b a]=butter(1,0.01);
mr2=filter(b,a,r2);
subplot(4,3,11);
plot(t,mr2);
title('DeModulated signal');
r3=s3.*c;
[b a]=butter(1,0.01);
mr3=filter(b,a,r3);
subplot(4,3,12);
plot(t,mr3);
title('DeModulated signal');

Answer 3

[Katkoju Ajay kumar]

* AM DSBFC Demodulation Circuit

V1 1 0 AC 50mV 50kHz

V2

2 0 AC 80mV 50Hz

M1

3 1 2 0 Multiplier

C1

4 3 1nF

R1

5 4 10k

D1

6 5 Diode

C2

7 6 1nF

R2

8 7 10k

Rload

9 8 1k

Osc

0 Rload

.model Diode D

.tran 0.1ms 200ms

.control

run

plot

V(1), V(2), V(9)

.endc