dm_demo.m

By using a MATLAB program, design a Delta Modulation (DM) system with one step-size and a modified D

%Sample demo for Delta modulation

close all
clear
% signal sampling
fs=1/2000;
tn=0:fs:1/25;
%Example1 ****************************
s=.5*sin(2*pi*50*tn);

% Delta modulation-demodulation
StepSize=1/15;
%encoder
cn=dm_encoder(s, StepSize);
%decoder
[Sn]=dm_decoder(StepSize,fs, cn);
%lowpass filter
Sa=lpf(100, .1, Sn);

%plot the input and accumulator output 
subplot(3,1,1):plot(s,'r');
grid on
title('DM (red:input signal, green:decoder output, blue: LPF output)');
ylabel('amplitude');
subplot(3,1,2):plot(Sn,'g');
grid on
ylabel('amplitude');
subplot(3,1,3):plot(Sa,'b');
grid on 
xlabel('index, n');
ylabel('amplitude');

%example2 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
figure
[s,fs]=wavread('bye441');  %read .wav file
% Delta modulation-demodulation
StepSize=1/15;
%encoder
cn=dm_encoder(s, StepSize);
%decoder
[Sn]=dm_decoder(StepSize,fs, cn);
%lowpass filter
Sa=lpf(100, .1, Sn);

%plot the input and accumulator output 
subplot(3,1,1):plot(s,'r');
grid on
title('DM (red:input signal, green:decoder output, blue: LPF output)');
ylabel('amplitude');
subplot(3,1,2):plot(Sn,'g');
grid on
ylabel('amplitude');
subplot(3,1,3):plot(Sa,'b');
grid on 
xlabel('index, n');
ylabel('amplitude');

sound(Sa,fs);