Digital Signal Processing Reference
In-Depth Information
1,00
0,75
0,50
0,25
0,00
-0,25
375
400
425
450
475
500
525
550
575
600
ms
Bit pattern
Bipolar
Time domain
Spectrum
LP 1 28Hz
IFFT
5,0
4,5
4,0
3,5
3,0
2,5
2,0
1,5
1,0
0,5
0,0
150
175
200
225
250
275
300
325
350
ms
Illustration 258:
Ideal filtering and limiting case
In Illustration 257, bottom, the limiting case (minimal bandwidth and complete reconstruction) is reached.
At a cutoff frequency of 100 Hz and an ideal - i.e. rectangular - bandwidth limitation the pulse response is
Si-shaped. In this special case, however, the Si-functions overlap as is shown in the Illustration, top. The
aggregate signal of the individual pulse responses is free of interference at the sampling instant because
the Si-functions of all neighbouring pulses have a zero crossing at that moment. The Illustration at the
bottom shows that in this case the "0" and "1" values of the bit pattern are definitely reconstructible at a
discrimination threshold of 50%.
