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

6.9 MATLAB Exercises 317
Figure 6.42
Original signal
and the PCM
signals with
different numbers
of quantization
levels.
Signal g(t) and its 16-level PCM signal
0
-1
-2L_ ___j___ L__ _ ___j___ L__ _ ___j___ L___'s:::z:lL__ _ __j____ _J
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
Time, second
Signal g(t) and its 4-level PCM signal
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
Delta Modulation
Instead of applying PCM, we illustrate the practical effect of step size selection in the design
of DM encoder. The basic function to implement DM is given in del tamod. m.
% (deltamod .m)
function s_DMout= deltamod (sig_in,Delta,td, ts)
% Usage
% s_DMout deltamod (xsig, Delta,td, ts) )
% Delta DM steps ize
% sig_in - input signal vector
% td original signal sampling period of sig_in
% ts new sampling period
% NOTE : td*fs must be a positive integer;
% Function outputs :
% s_DMout - DM sampled output
if (rem(ts/td, 1)==0)
nfac=round (ts/td) ;
p_zoh=ones (l,nfac) ;
s_down=downsample ( sig_in,nfac) ;
Num_i t=length ( s_down) ;