Transcript REview to Electronics Comm_Lecture1

ELECTRONICS
COMMUNICATIONS(EKT313)
Introduction
By:Cik Junita Mohd Nordin
049798419/0133910593
School:PPKKP,
Aras 2,Blok A, Kompleks Pengajian KUKUM
EKT313
Sem: 1 2006/2007
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Meeting: Lecture 3 Hours,
Lab 2 Hours
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Tuesdays: 12-2pm; 4-6 pm (labs)
Thursdays: 3-4pm
Attendance are compulsory!!
SYNOPSIS
OBJECTIVES:
To introduce and familiarized the students
to electronics elements, components
and circuits used in RF communications.
At the end of the course, student would
also be able to design and analyze the
RF communication circuits.
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SYNOPSIS
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TOPICS COVERED ARE:
- Introductions to Electronics
Communications, AM& SSB
Modulations, AM Circuits, FM and FM
Circuits, Radio Transmitter and
Communications Receivers
ASSESSMENTS
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Final exam = 50%
Test 1
= 10%
Assignments/quizzes=5%
Lab
= 35%
presentation
Report
Project
LECTURE 1
REVIEW TO COMMUNICATION
SYSTEMS
PART 1
WHAT DO YOU UNDERSTAND
of
COMMUNICATION SYSTEM?
DEFINITIONS OF
COMMUNICATIONS
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Humans exchanging information
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Machines exchanging information
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Conveying thoughts, feelings,
ideas, and facts
Sending and receiving information
by electronic means
BARRIERS TO
COMMUNICATIONS
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Language: human,
computer, or electronic
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Distance: space between
sending and receiving
parties
COMMON FORMS OF
COMMUNICATIONS
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Human voice: face-to-face conversations,
public speakers, actors in plays, etc.
Audio: CDs, tape, records, radio
Body language: non-verbal
Print: newspapers, magazines, books, etc.
Film: still and movie
Video: movies, graphics and animation
Music: personal, concerts
FORMS OF ELECTRONIC
COMMUNICATIONS
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Radio and TV broadcasting
Telephone, wired and wireless
Fax
Pagers
Computer networks: modem, email, Internet and World Wide
Web, wireless
Satellites, radar, radio telescopes
KEY MILESTONES IN
ELECTRONIC COMMUNICATIONS
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1844
1876
1895
1923
1943
1946
1962
1989
Telegraph
Telephone
Radio
TV
Radar
Computers
Satellites
Internet
MODEL OF ALL
COMMUNICATIONS SYSTEMS
Transmitter
TX
Channel
Communications
medium
Noise
Information to be
transmitted
Receiver
RX
Received
information
TYPES OF
COMMUNICATIONS
TX
Channel
TX
RX
RX
Channel(s)
RX
TX
Simplex:
One-way
Duplex:
Two-way
Half duplex:
Alternate TX/RX
Full duplex:
Simultaneous
TX/RX
TYPES OF COMMUNICATIONS
SIGNALS
Analog - smooth and continuous voltage variation.
Digital - binary or two voltage levels.
Time
COMMUNICATIONS
SIGNAL VARIATIONS
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Baseband - The original
information signal such as audio,
video, or computer data. Can be
analog or digital.
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Broadband - The baseband signal
modulates or modifies a carrier
signal, which is usually a sine
wave at a frequency much higher
than the baseband signal.
MODULATION
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An electronic technique in which a
baseband information signal
modifies a carrier signal (usually a
sine wave) for the purpose of
frequency translation and carrying
the information signal via radio.
The common types of modulation
are amplitude, frequency and phase.
AMPLITUDE MODULATION
The modulating (baseband) signal is a sinusoid in this example.
High-frequency carrier
An AM signal as it usually
appears on an oscilloscope
The carrier frequency is normally much
higher than the baseband frequency.
FREQUENCY MODULATION
The baseband signal controls the carrier’s frequency
and the carrier’s amplitude remains constant.
Carrier
Resting fc
Increasing fc
Decreasing fc
Increasing fc
Resting fc
Modulating signal
FM
MULTIPLEXING
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Multiplexing (MUX or MPX) - the
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Demultiplexing (DEMUX or DMPX) - the
process of simultaneously transmitting
two or more baseband information
signals over a single communications
channel.
process of recovering the individual
baseband signals from the multiplexed
signal.
MULTIPLEXING AND
DEMULTIPLEXING
Single communications channel (radio or cable)
MUX
Original baseband
information signals
DEMUX
Recovered baseband
information signals
ELECTRONIC COMMUNICATIONS
APPLICATIONS
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Radio broadcasting (AM & FM)
Television broadcasting (analog &
DTV)
Cable TV
Wireless remote control
Paging
Navigation and direction finding
Telemetry
ELECTRONIC COMMUNICATIONS
APPLICATIONS (Continued)
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Radio astronomy
Surveillance
RF identification (ID)
Music services
Telephones (wired, cordless,
cellular)
Facsimile
Two-way radio
ELECTRONIC COMMUNICATIONS
APPLICATIONS (Continued)
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Radar
Sonar
Amateur radio
Citizens and family radio
Data communications
Networks
Internet and World Wide
Web
FREQUENCY AND WAVELENGTH
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Cycle - One complete occurrence of a
repeating wave (periodic signal) such
as one positive and one negative
alternation of a sine wave.
Frequency - the number of cycles of a
signal that occur in one second.
Period - the time distance between two
similar points on a periodic wave.
Wavelength - the distance traveled by
an electromagnetic (radio) wave during
one period.
PERIOD AND FREQUENCY
COMPARED
T = One period
time
One cycle
Frequency = f = 1/T
Frequency and wavelength compared
+
T
0
time
f = 1/T
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distance
CALCULATING WAVELENGTH
AND FREQUENCY
 = 300/f
f = 300/
 = wavelength in meters
f = frequency in MHz
(f = 300/)
Frequency
300 GHz
30 GHz
VHF UHF SHF EHF
Millimeter
waves
10-4 m
10-3 m
10-2 m
10-1 m
1m
10 m
102 m
103 m
104 m
105 m
106 m
107 m
Wavelength
3 GHz
HF
300 MHz
MF
30 MHz
LF
3 MHz
VLF
300 kHz
VF
30 kHz
ELF
3 kHz
300 Hz
30 Hz
THE ELECTROMAGNETIC SPECTRUM
FROM 30 HZ TO 300 GHZ
( = 300/f)
LOW AND MEDIUM
FREQUENCIES
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Extremely Low Frequencies - 30 to
300 Hz
Voice Frequencies - 300 to 3000 Hz
Very Low Frequencies - 3 kHz to 30
kHz
Low Frequencies - 30 kHz to 300 kHz
Medium Frequencies - 300 kHz to 3
MHz
HIGH FREQUENCIES
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High Frequencies
- 3 MHz to 30 MHz
Very High Frequencies
- 30 MHz to 300 MHz
Ultra High Frequencies
- 300 MHz to 3 GHz
(1 GHz and above = microwaves)
Super High Frequencies
- 3 GHz to 30 GHz
Extremely High Frequencies
- 30 GHz to 300 GHz
300 GHz
Cosmic rays
Gamma rays
X-rays
Ultraviolet
Visible
Infrared
Millimeter
waves
0.4 x 10-6 m
0.8 x 10-6 m
10-5 m
10-4 m
10-3 m
THE ELECTROMAGNETIC
SPECTRUM ABOVE 300 GHZ
Wavelength
OPTICAL FREQUENCIES
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Infrared - 0.7 to 10 micron
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Visible light - 0.4 to 0.8 micron
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Ultraviolet - Shorter than 0.4
micron
Note: A micron is one millionth of a meter.
Light waves are measured and expressed
in wavelength rather than frequency.
Noise, interference and
distortion
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Noise:unwanted signals that coincide with the desired
signals. Noise is random, undesirable electric energy.
Two type of noise:internal and external noise.
Internal noise: Caused by internal
devices/components in the circuits.
External noise:noise that is generated outside the
circuit. Eg: atmospheric noise,solar noise, cosmic
noise, man made noise.
Interference-one type of external noise
Distortion: signal being distorted
Limitations in communication
system
Physical constraint
-Delay, attenuation, bandwidth
limitation, etc
 Technological constraint
- hardware.
- Expertise
- economy, law
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Frequency Spectrum &Bandwidth
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The frequency spectrum of a waveform
consists of all frequencies contained in
the waveform and their amplitudes
plotted in the frequency domain.
The bandwidth of a frequency spectrum
is the range of of frequencies contained
in the spectrum.It is calculated by
subtracting the lowest frequency from
the highest.
Frequency Spectrum &Bandwidth
(cont’d)
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Bandwidth of the information signal
equals to the difference between the
highest and lowest frequency contained
in the signal.
Similarly, bandwidth of communication
channel is the difference between the
highest and lowest frequency that the
channel allow to pass through it