Digital Signal Processing Reference
In-Depth Information
Signals
Time domain
Signalswitch
Audio
Analog-out
4
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0
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s
Illustration 22:
Important periodic signals
Here you see five important forms of periodic signals, from the top to the bottom: sine, triangle, rectangle,
saw tooth and (extremely short!) pulses. From a theoretical point of view periodic signals are of infinite
duration, that is, they extend far into the past and future beyond the illustrated segment. Try to determine
the period length and frequency of the individual signals.
Surprisingly however, we must say that language and music are not conceivable without
"near periodic" oscillations inspite of what has just been said. Periodic oscillations are
easier to describe in their behaviour and that is why we are dealing with them at the
beginning of this topic.
Our ear as a FOURIER-analyzer
By means of very simple experiments it is possible to establish fundamental common
features of different oscillation and signal forms. Simple instruments to be found in
almost any collection of teaching aids are adequate for this purpose.
A function generator is able to produce different periodic AC voltages. It represents the
source of the signal. The signal can be heard over the loudspeaker and can be seen on the
screen of the oscilloscope or computer.
