(a) Explain why a digital signal necessarily has a periodic spectrum.
(b) Why must every digital signal - stored over a block length n - be understood as periodic in the time domain over the block length n?
(c) Analog signals can be interpreted as the limiting case of a digital signal. What does this limiting case look like?
(d) By means of what trick using DASYLab was the frequency domain in Illustration 197 - Illustration 203 expanded to such an extent compared with Illustration 190 - Illustration 196 that the periodicity of the spectra can be recognized.