Chapter01

© 2008 The McGraw-Hill Companies
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Principles of ElectronicPrinciples of Electronic
Communication SystemsCommunication Systems
Third Edition
Louis E. Frenzel, Jr.

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Chapter 1Chapter 1
Introduction to Electronic Communication

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Topics Covered in Chapter 1Topics Covered in Chapter 1
 1-1: Significance of Human Communication
 1-2: Communication Systems
 1-3: Types of Electronic Communication
 1-4: Modulation and Multiplexing
 1-5: The Electromagnetic Spectrum
 1-6: Bandwidth
 1-7: A Survey of Communication Applications
 1-8: Jobs and Careers in the Communication
Industry

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1-1: Significance of1-1: Significance of
Human CommunicationHuman Communication
 Communication is the
process of exchanging
information.
 Main barriers are language
and distance.
 Contemporary society’s
emphasis is now the
accumulation, packaging, and
exchange of information.

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1-1: Significance of1-1: Significance of
Human CommunicationHuman Communication
Methods of communication:
1.Face to face
2.Signals
3.Written word (letters)
4.Electrical innovations:
•Telegraph
•Telephone
•Radio
•Television
•Internet (computer)

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1-2: Communication Systems1-2: Communication Systems
 Basic components:
 Transmitter
 Channel or medium
 Receiver
 Noise degrades or interferes with transmitted
information.

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Figure 1-2:
A general model of all communication systems.

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Transmitter is a collection of electronic
components and circuits that converts the
electrical signal into a signal suitable for
transmission over a given medium.
Transmitters are made up of oscillators,
amplifiers, tuned circuits and filters,
modulators, frequency mixers, frequency
synthesizers, and other circuits.

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 The Communication Channel is the
medium by which the electronic signal is sent
from one place to another.
 Types of media include
•Electrical conductors
•Optical media
•Free space
•System-specific media (e.g., water is the
medium for sonar).

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 RECEIVER is a collection of electronic
components and circuits that accepts the
transmitted message from the channel and
converts it back into a form understandable
by humans.
 Receivers contain amplifiers, oscillators,
mixers, tuned circuits and filters, and a
demodulator or detector that recovers the
original intelligence signal from the
modulated carrier.

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 TRANSCEIVER is an electronic unit that
incorporates circuits that both send and
receive signals.
Examples are:
 Telephones
 Fax machines
 Handheld CB radios
 Cell phones
 Computer modems

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ATTENUATION
Signal Attenuation, or
degradation, exists in all media
of wireless transmission. It is
proportional to the square of the
distance between the
transmitter and receiver.

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Noise
It is random, undesirable
electronic energy that enters
the communication system via
the communicating medium
and interferes with the
transmitted message.

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1-3: Types of Electronic1-3: Types of Electronic
CommunicationCommunication
 Electronic communications are
classified according to whether they are:
a. One-way (simplex)
b. two-way transmissions
a) full duplex
b) half duplex
OR
A. Analog Signals.
B. Digital Signals.

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SIMPLEX
The simplest method of electronic
communication is referred to as
simplex.
This type of communication is one-
way. Examples are:
Radio
TV broadcasting
Beeper (personal receiver)

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Full Duplex
Most electronic communication is
two-way and is referred to as
duplex.
When people can talk and listen
simultaneously, it is called full
duplex. The telephone is an
example of this type of
communication.

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Half Duplex
 The form of two-way communication in
which only one party transmits at a time is
known as half duplex. Examples are:
 Police, military, etc. radio transmissions
 Citizen band (CB)
 Family radio
 Amateur radio

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Analog Signals
An analog signal is a smoothly
and continuously varying voltage
or current. Examples are:
Sine wave
Voice
Video (TV)

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Figure 1-5: Analog signals
(a) Sine wave “tone.”
(b) Voice. (c) Video (TV) signal.

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Digital Signals
 Digital signals change in steps or in
discrete increments.
 Most digital signals use binary or two-state
codes. Examples are:
 Telegraph (Morse code)
 Continuous wave (CW) code
 Serial binary code (used in computers)

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Figure 1-6: Digital signals (a) Telegraph (Morse
code). (b) Continuous-wave (CW) code. (c) Serial
binary code.

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Digital Signals
 Many transmissions are of signals that originate
in digital form but must be converted to analog
form to match the transmission medium.
 Digital data over the telephone network.
Analog signals.
 They are first digitized with an analog-to-digital
(A/D) converter.
 The data can then be transmitted and
processed by computers and other digital
circuits.

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1-4: Modulation and Multiplexing1-4: Modulation and Multiplexing
Modulation and multiplexing are
electronic techniques for transmitting
information efficiently from one place to
another.
Modulation makes the information
signal more compatible with the medium.
Multiplexing allows more than one
signal to be transmitted concurrently
over a single medium.

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1. Baseband Transmission
Baseband information can be sent
directly and unmodified over the medium
or can be used to modulate a carrier for
transmission over the medium.
 In telephone or intercom systems, the voice
is placed on the wires and transmitted.
 In some computer networks, the digital
signals are applied directly to coaxial or
twisted-pair cables for transmission.

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2. Broadband Transmission
A carrier is a high frequency
signal that is modulated by audio,
video, or data.
A radio-frequency (RF) wave is
an electromagnetic signal that is
able to travel long distances
through space.

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Broadband Transmission (continue)
 A broadband transmission takes place when a
carrier signal is modulated, amplified, and sent to
the antenna for transmission.
 The two most common methods of modulation
are:
 Amplitude Modulation (AM)
 Frequency Modulation (FM)
 Another method is called phase modulation
(PM), in which the phase angle of the sine wave
is varied.

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Figure 1-7: Modulation at the transmitter.

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Figure 1-8: Types of modulation. (a) Amplitude modulation.

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Figure 1-8: Types of modulation.(b) Frequency modulation.

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Broadband Transmission
 Frequency-shift keying (FSK) takes place
when data is converted to frequency-varying
tones.
 Devices called modems (modulator-
demodulator) translate the data from digital to
analog and back again.
 Demodulation or detection takes place in the
receiver when the original baseband (e.g.
audio) signal is extracted.

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Multiplexing: Multiplexing is the
process of allowing two or more
signals to share the same medium
or channel.
 The three basic types of multiplexing are:
Frequency division
Time division
Code division

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Figure 1-11: Multiplexing at the transmitter.

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1-5: The Electromagnetic Spectrum1-5: The Electromagnetic Spectrum
The range of
electromagnetic signals
encompassing all
frequencies is referred to
as the electromagnetic
spectrum.

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Figure 1-13: The electromagnetic spectrum.

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Frequency and Wavelength:Frequency and Wavelength: FrequencyFrequency
 A signal is located on the frequency
spectrum according to its frequency and
wavelength.
 Frequency is the number of cycles of a
repetitive wave that occur in a given period
of time.
 A cycle consists of two voltage polarity
reversals, current reversals, or
electromagnetic field oscillations.
 Frequency is measured in cycles per
second (cps).
 The unit of frequency is the hertz (Hz).

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Example:
What is the wavelength if the frequency is
4MHz?
Wavelength
Wavelength (λ) = speed of light ÷ frequency
Speed of light = 3 × 108
meters/second
Therefore:
λ = 3 × 108
/ f
λ = 3 × 108
/ 4 MHz
= 75 meters (m)

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Wavelength:Wavelength:
 Wavelength is the distance occupied
by one cycle of a wave and is usually
expressed in meters.
Wavelength is also the distance
traveled by an electromagnetic wave
during the time of one cycle.
The wavelength of a signal is
represented by the Greek letter
lambda (λ).

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Figure 1-15: Frequency and wavelength. (a) One cycle. (b) One wavelength.

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The electromagnetic spectrum is divided into segments:
• Extremely Low Frequencies
(ELF)
30–300 Hz.
• Voice Frequencies (VF) 300–3000 Hz.
• Very Low Frequencies (VLF) include the higher end of the
human hearing range up to
about 20 kHz.
• Low Frequencies (LF) o30–300 kHz.
• Medium Frequencies (MF) 300–3000 kHz
AM radio 535–1605 kHz.

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High Frequencies (HF)
(short waves; VOA, BBC
broadcasts; government and
military two-way communication;
amateur radio, CB.
3–30 MHz
Very High Frequencies (VHF)
FM radio broadcasting (88–108
MHz), television channels 2–13.
30–300 MHz
Ultra High Frequencies (UHF)
TV channels 14–67, cellular
phones, military communication.
300–3000 MHz

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Microwaves and Super High
Frequencies (SHF)
Satellite communication, radar,
wireless LANs, microwave ovens
1–30 GHz
Extremely High Frequencies (EHF)
Satellite communication, computer
data, radar
30–300 GHz

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Optical Spectrum
The optical spectrum exists directly
above the millimeter wave region.
Three types of light waves are:
Infrared
Visible spectrum
Ultraviolet

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Optical Spectrum:Optical Spectrum:
Infrared: Infrared
radiation is produced by
any physical equipment
that generates heat,
including our bodies.

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Infrared is used:Infrared is used:
In astronomy, to detect stars and
other physical bodies in the
universe,
For guidance in weapons
systems, where the heat radiated
from airplanes or missiles can be
detected and used to guide
missiles to targets.

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In most new TV remote-control
units, where special coded signals
are transmitted by an infrared LED
to the TV receiver to change
channels, set the volume, and
perform other functions.
In some of the newer wireless LANs
and all fiber-optic communication.
Infrared is used:Infrared is used:

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Optical Spectrum:Optical Spectrum: The Visible SpectrumThe Visible Spectrum
 Just above the infrared region is the visible
spectrum we refer to as light.
 Red is low-frequency or long-wavelength light
 Violet is high-frequency or short-wavelength
light.
 Light waves’ very high frequency enables
them to handle a tremendous amount of
information (the bandwidth of the baseband
signals can be very wide).

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Optical Spectrum: Ultraviolet
Ultraviolet is not used for
communication
Its primary use is medical.

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1-6: Bandwidth1-6: Bandwidth
Bandwidth (BW) is that portion
of the electromagnetic spectrum
occupied by a signal.
Channel bandwidth refers to
the range of frequencies required
to transmit the desired
information.

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More Room at the Top
 Today, virtually the entire frequency spectrum between
approximately 30 kHz and 300 MHz has been spoken
for.
 There is tremendous competition for these frequencies,
between companies, individuals, and government
services in individual carriers and between the different
nations of the world.
 The electromagnetic spectrum is one of our most
precious natural resources.

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More Room at the Top
 Communication engineering is devoted to making the
best use of that finite spectrum.
 Great effort goes into developing communication
techniques that minimize the bandwidth required to
transmit given information and thus conserve spectrum
space.
 This provides more room for additional communication
channels and gives other services or users an
opportunity to take advantage of it.

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Spectrum Management and Standards
 Spectrum management is provided by agencies set up
by the United States and other countries to control
spectrum use.
 The Federal Communications Commission (FCC)
and the National Telecommunications and
Information Administration (NTIA) are two agencies
that deal in spectrum management.
 Standards are specifications and guidelines necessary
to ensure compatibility between transmitting and
receiving equipment.

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1-7: A Survey of1-7: A Survey of
Communications ApplicationsCommunications Applications
 Simplex
 AM and FM
broadcasting
 Digital radio
 TV broadcasting
 Digital television (DTV)
 Cable television
 Facsimile
 Wireless remote control
 Paging services
 Navigation and
direction-finding
services
 Telemetry
 Radio astronomy
 Surveillance
 Music services
 Internet radio and
video

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1-7: A Survey of1-7: A Survey of
Communications ApplicationsCommunications Applications
 Duplex
 Telephones
 Two-way radio
 Radar
 Sonar
 Amateur radio
 Citizens radio
 Family Radio service
 The Internet
 Wide-area networks
(WANs)
 Metropolitan-area
networks (MANs)
 Local area networks
(LANs)

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1-8: Jobs and Careers in the1-8: Jobs and Careers in the
Communication IndustryCommunication Industry
 The electronics industry is roughly divided into
four major specializations:
1. Communications (largest in terms of people
employed and the dollar value of equipment
purchased)
2. Computers (second largest).
3. Industrial controls.
4. Instrumentation.

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Types of Jobs
 Engineers design communication equipment and
systems.
 Technicians install, troubleshoot, repair, calibrate, and
maintain equipment.
 Engineering Technicians assist in equipment design,
testing, and assembly.

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Types of Jobs
 Technical sales representatives determine customer
needs and related specifications, write proposals and
sell equipment.
 Technical writers generate technical documentation for
equipment and systems.
 Trainers develop programs, generate training and
presentation materials, and conduct classroom training.

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Major Employers
 The communication electronics industry is made up of
the following segments:
 Manufacturers
 Resellers
 Service Organizations
 End users

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Figure 1-18: Structure of the communication electronics industry.

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