Multirate Digital Signal Processing, Oversampling of Analog-to-Digital Conversion, and Undersampling of Bandpass Signals - Digital Signal Processing: Fundamentals and Applications - page 591

5

xq(n)

4

yq(n)

3

2

1

0

-1

-2

x(t)

-3

-4

-5

0 5 10 15 20 25 30 35 40 45 50

Sample number

FIGURE 12.27

Comparisons of continuous, regular sampled, and oversampled signal amplitudes.

subplot(3,2,2);plot(f(1:NN/2),log10(Ak(1:NN/2)), k );grid;ylabel( X(f) ); axis([0 500

' ' ' '

-4 2])
subplot(3,2,3);plot(n,xq, k );grid;axis([0 500 -5 5]);ylabel( xq(n) );

' ' ' '

Ak Ak(1)/2;

subplot(3,2,4);plot(f(1:NN/2),log10(Ak(1:NN/2)),

¼ 2*abs(fft(xq))/NN; Ak(1) ¼

k );grid;ylabel( Xq(f) ); axis([0 500

' ' ' '

-4 2])
subplot(3,2,5);plot(n,yd, ' k ' );grid;axis([0 500 -5 5]);ylabel( ' yq(n) ' );
xlabel( ' Sample number ' );
Ak ¼ 2*abs(fft(yd))/NN; Ak(1) ¼ Ak(1)/2;
subplot(3,2,6);plot(f(1:NN/2),log10(Ak(1:NN/2)), ' k ' );grid;ylabel( ' Yq(f) ' ); axis([0 500
-4 2])
xlabel( ' Frequency (Hz) ' );
figure (3)
plot(n(1:50),x(1:50), ' k ' , ' LineWidth ' ,2); hold % Plot of

rst 50 samples

stairs(n(1:50),xq(1:50), ' b ' );
stairs(n(1:50),yd(1 þ nd:50 þ nd), ' r ' , ' LineWidth ' ,2);grid
axis([0 50 -5 5]);xlabel( ' Sample number ' );ylabel( ' Amplitudes ' )
snr(x,xq);
snr(x(1:ntotal-nd),yd(1 þ nd:ntotal));