Digital Signal Processing Reference
In-Depth Information
Illustration 38:
From the periodic signal with a line spectrum to the non-periodic signal with a
continuous spectrum.
On the left in the time domain you see sequences of periodic rectangular pulses from top to bottom. The
pulse frequency is halved in each case but the pulse width remains constant. Accordingly the distance
between the spectral lines becomes smaller and smaller (T = 1/f), but the position of the zero positions
does not change as a result of the constant pulse duration.
Finally, in the lower sequence a one-time rectangular pulse is depicted. Theoretically it has the period
length . The spectral lines lie "infinitely close" to each other, the spectrum is continuous and is
drawn as a continuous function.
T
→
∞
We have now gone over to the customary (two-dimensional) representation of the time and frequency
domains. This results in a much more accurate picture in comparison to the "playground" for sinusoidal
signals used up to now.
