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Department Electrical & Computer Engineering
EK131 E5
Introduction to Engineering
Prof. Michel A. Kinsy
Lecture 6: Analog and Digital Signals
Department Electrical & Computer Engineering
Signals & Computing
Physical World
Computing System Store and Process
SenseAct
Department Electrical & Computer Engineering
Signals & Data Representation
Computing Cycle
Physical World
Computing System Store and Process
SenseAct
The physical world is analog
Most computing systems are digital
Computers has more senses: they can see, hear, taste, smell, and feel things that humans cannot
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Signals
Human life is one of continuous signal processing
What is a signal?
• An electromagnetic representation of data
Then what is a data?
• Some entity that has meaning or conveys information
Signal processing and transmission
• Consist of moving data from source to destination
through the use of signals
Two signal types
• Analog and Digital
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Characteristics of Signals
Communication channel
• Media used to transmit the signal
• It can be:
Physical wire
• Copper wire, fiber, etc.
Radio wave
• Line of sight, Ground waves and Sky waves
Radiated source of energy
• x-rays
Free space
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Characteristics of Signals
All signals are transmitted via electromagnetic
radiation (EM radiation or EMR)
• EM radiation is the radiant energy released through
an electromagnetic processes
Electromagnetic waves
• Synchronized oscillations of electric and magnetic
fields that propagate at the speed of light through a
vacuum
Examples of electromagnetic radiation
• Visible light, radio, infrared, and x-rays
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Characteristics of Signals
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Characteristics of Signals
Bandwidth • The range of frequencies occupied or used by a carrier
wave
Attenuation • As a signal propagates, its strength decreases
Noise • Unwanted electromagnetic energy that degrades the
signal Crosstalk and other interferences
Distortion • Denotes the altering the original shape or characteristics
of waveform representing the signal
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Characteristics of Signals
An electromagnetic wave is defined by four
parameters
• Amplitude
• Frequency
• Wavelength
• Phase
Wavelength
Amplitude
Department Electrical & Computer Engineering
Characteristics of Signals
An electromagnetic wave
is defined by four
parameters
• Amplitude
A measure of waveform
strength at a given point in
time
Wavelength
Amplitude
Department Electrical & Computer Engineering
Characteristics of Signals
An electromagnetic wave
is defined by four
parameters
• Frequency
Number of times a wave
cycles from peak amplitude
to low amplitude and back to
peak again
Measured in cycles/sec
(Hertz, Hz)
Frequency = 1 cycle / sec =
1 Hz
Wavelength
Amplitude
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Characteristics of Signals
An electromagnetic wave is
defined by four parameters
• Wavelength
The distance between two
corresponding points on a
wave cycle
Wavelength is generally
expressed in some variant of
meters or feet
Wavelength is inversely
proportional to frequency
• High frequency implies short
wavelength
Wavelength
Amplitude
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Characteristics of Signals
An electromagnetic wave
is defined by four
parameters
• Phase
The progress of a wave over
time in relationship to a fixed
point
Two separate waves with
same amplitude and
frequency starting at different
points in time
Phases are 90 degrees apart
Wavelength
Amplitude
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Types of Signals
Two types of signal that can be composed three
ways: analog, digital, and mixed signal
• Analog has values from a continuous set
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Types of Signals
With analog signals
• One-to-one relationship between how data are
captured and recorded and how data are
reproduced
• Higher fidelity
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Types of Signals
Two types of signal that can be composed three
ways: analog, digital, and mixed signal
• With digital, signals have a finite number of discrete
values
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Modern Data Processing Systems
Modern data processing systems are mainly
digital systems
Digital representation means that everything is
represented by numbers only
Digital representation is very suited for both
numerical and non-numerical information or data
processing
• Numerical values: 0, 4, 5567, 24354543, -2
• Non-numerical values: There will be light! (Each
letter in this sentence)
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Advantages of Digital Systems
Easier to control by electronics• The finite number of values in a digital system can be
represented by a vector of signals with just two values (binary signals)
Device to process this type of signal is very simple
Can be a switch: open/close
Adjustable precision
Complex digital integrated circuits (ICs) are manufactured with the advent of Microelectronics Technology
Higher noise immunity
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Challenges with Digital Systems
Our physical world is analog and computing is
interacting with the physical world:
• So we need to convert physical signals to digital
then back to analog to communicate with the real
world
Data
Audio
Image
Video
A-to-D
Digital
Computing
System
D-to-AReceiver
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Discretization of Signals
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Next Class
Electronics components: resistors, capacitors,
inductors, transistors, RC circuits, KVL, KCL