PRACTICAL MATLAB® FOR ENGINEERS PRACTICAL MATLAB

Time Domain Representation of Continuous and Discrete Signals 81

figure(2) % reconstructions

f25 = 0;

for k = 1:1:26;

fr25 = fd(k)*sinc(Fs*(t-k*Ts));

f25 = f25+fr25;

end

subplot(3,1,1)

plot(t,f25,’ko-’,t,fa,’ks-.’); legend(‘sinc-reconst’,’f(t)’);

title(‘Reconstruction of f(t) ‘)

ylabel(‘Amplitude’)

subplot(3,1,2)

stem(nTs,fd);hold on;

stairs(nTs,fd); ylabel(‘Amplitude’);legend(‘stairs’)

subplot(3,1,3)

y = spline(nTs,fd,t);

plot(nTs(1:2.5:26.5),y); legend(‘spline’);

ylabel(‘Amplitude’)

xlabel(‘time (sec)’)

figure(3)

error=abs(fa-f25);

plot(t,error);ylabel(‘magnitude’)

title(‘error(t) = abs [f(t) - Reconstruction (Sums(sinc))]’)

xlabel(‘time(sec)’)

Back in the command window the script fi le sample_data is executed and the results are

shown in Figures 1.67 through 1.69.

FIGURE 1.67

Plots of f(t) and f(nT) of Example 1.16.

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

× 10 −^3

× 10 −^4

× 10 −^4

time index n (msec)

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

× 10 −^3

time t (msec)

4

2

0

Amplitude

4

2

0

Amplitude

f(t) versus t

f(t) sample with Ts=.2msec.