CE_DeltaModulation.m

clc; 
clear all; 
close all; 
pkg load signal

%Signal Parameters
A=1;
fc=1; 
t=linspace(0,1,1000);
x_t=A*sin(2*pi*fc*t);
s=.2; 

%Delta Modulation
s_t=0;
v=1;
mqc_t=0;
for i=1:5:length(t)
  if(x_t(1,i)>mqc_t(1,v))
  s_t(1,v)=1;
  mqc_t(1,v+1)=mqc_t(1,v)+s;
else
 s_t(1,v)=0;
  mqc_t(1,v+1)=mqc_t(1,v)-s;
end
t1(1,v)=t(1,i);
v=v+1;
end

subplot(3,1,1) %first plot
plot(t,x_t);
title('Message Signal (1904215)');
xlabel('Time Axis');
ylabel('Amplitude');
hold on
stairs(t1,mqc_t(2:201))

subplot(3,1,2) %second plot
stairs(s_t)
title('Delta Modulated Signal (1904215)');
xlabel('Time Axis');
ylabel('Amplitude');
hold on
stem(s_t,'r')
axis([0 200 -0.5 1.5])

%Demodulation
mq_t=0;
%Convert bit stream into steps and integrate
for i=1:length(s_t)
  if(s_t(i)==1)
  mq_t(i+1)=mq_t(i)+s;
else
  mq_t(i+1)=mq_t(i)-s;
end
end

%Filtering through LPF
[b,a]=butter(5,.1);
r_t=filter(b,a,mq_t);

subplot(3,1,3) %third plot
plot(t1,r_t(2:201))
title('Demodulated Signal (1904215)');
xlabel('Time Axis');
ylabel('Amplitude');
hold on;

xn=0; 
for i=1:l 
  if x(i)>xn(i) 
    d(i)=1; 
    xn(i+1)=xn(i)+delta; 
  else d(i)=0; xn(i+1)=xn(i)-delta; 
  end 
end 
stairs(xn) 
hold on 
for i=1:d 
  if d(i)>xn(i) 
    d(i)=0; 
    xn(i+1)=xn(i)-delta; 
  else d(i)=1; 
    xn(i+1)=xn(i)+delta; 
  end 
end 
plot(xn);