B. P. Lathi, Zhi Ding - Modern Digital and Analog Communication Systems-Oxford University Press (2009)

318 SAMPLING AND ANALOG-TO-DIGITAL CONVERSION
Fi g
ure 6.43
Comparison
between the
original signal
and the PCM
signals after
low-pass filtering
to recover the
original
message.
0
Signal g(t) and filtered 16-PCM signal
-- Original
· - ' - Recovered
- 1
- 2 '----'------'----'-------'----_.__---'----'--""'-'--'------'----'
0 0.1 0.2 0.3 0.4 0.5 0.6 0.8 0.9
Time, second
Signal g(t) and filtered 4-PCM signal
-- Original
· - · - Recovered
0
- 1
-2 '----'------'----'-------'----_.__---'----'--"""",c._-'------'----'
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
Time, second
s_DMout (l)=-Delta/2 ;
for k=2 : Num_it
xvar=s_DMout (k- 1) ;
s_DMout (k) =xvar+Delta*s ign ( s_down (k-1)-xvar) ;
end
s_DMout=kron ( s_DMout ,p_zoh) ;
else
warning ('Error ! ts/td is not an integer! ');
s_DMout= [l ;
end
end
To generate DM signals with different step sizes, we apply the same signal g(t) as used
in the PCM example. The MATLAB program ExDM . m applies three step sizes: L'. 1 = 0.2,
L'.2 = 2L'. 1 , and b.3 = 4L'. 1 .
% (ExDM.m)
% Example of sampling, quantization, and zero-order hold
clear;clf;
td=0 .002 ; %original sampling rate 500 Hz