文档介绍：SignalsSignals andand SignalSignal ProcessingProcessing
• Signals play an important role in our daily
life
• A signal is a function of independent
variables such as time, distance, position,
temperature, and pressure
• Some examples of typical signals are shown
next
1 Copyright © 2002 S. K. Mitra
ExamplesExamples ofof TypicalTypical SignalsSignals
• Speech and music signals - Represent air
pressure as a function of time at a point in
space
• Waveform of the speech signal “I like
digital signal processing” is shown below
1
0
Amplitude
-
-1
0 1 2 3
2 Time, sec. Copyright © 2002 S. K. Mitra
ExamplesExamples ofof TypicalTypical SignalsSignals
• Electrocardiography (ECG) Signal -
Represents the electrical activity of the
heart
• A typical ECG signal is shown below
3 Copyright © 2002 S. K. Mitra
ExamplesExamples ofof TypicalTypical SignalsSignals
• The ECG trace is a periodic waveform
• One period of the waveform shown below
represents one cycle of the blood transfer
process from the heart to the arteries
R
T
P
Millivolts
Q
S
Seconds
4 Copyright © 2002 S. K. Mitra
ExamplesExamples ofof TypicalTypical SignalsSignals
• Electroencephalogram (EEG) Signals -
Represent the electrical activity caused by
the random firings of billions of neurons in
the brain
5 Copyright © 2002 S. K. Mitra
ExamplesExamples ofof TypicalTypical SignalsSignals
• Seismic Signals - Caused by the movement
of rocks resulting from an earthquake, a
volcanic eruption, or an underground
explosion
• The ground movement generates 3 types of
elastic waves that propagate through the
body of the earth in all directions from the
source of movement
6 Copyright © 2002 S. K. Mitra
ExamplesExamples ofof TypicalTypical SignalsSignals
• Typical seismograph record
7 Copyright © 2002 S. K. Mitra
ExamplesExamples ofof TypicalTypical SignalsSignals
• Black-and-white picture - Represents light
intensity as a