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ELECTRONICS COMMUNICATIONS(EKT313
)Introduction
By:Cik Junita Mohd Nordin049798419/0133910593
School:PPKKP,Aras 2,Blok A, Kompleks Pengajian KUKUM
EKT313Sem: 1 2006/2007
Meeting: Lecture 3 Hours, Lab 2 Hours
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.
SYNOPSIS TOPICS COVERED ARE:
- Introductions to Electronics Communications, AM& SSB
Modulations, AM Circuits, FM and FM Circuits, Radio Transmitter and
Communications Receivers
ASSESSMENTS Final exam = 50% Test 1 = 10% Assignments/quizzes=5% Lab = 35%
presentationReport Project
LECTURE 1
REVIEW TO COMMUNICATION SYSTEMS
PART 1
WHAT DO YOU UNDERSTAND
ofCOMMUNICATION SYSTEM?
DEFINITIONS OF COMMUNICATIONS Humans exchanging information Machines exchanging
information Conveying thoughts, feelings,
ideas, and facts Sending and receiving
information by electronic means
BARRIERS TO COMMUNICATIONS
Language: human, computer, or electronic
Distance: space between sending and receiving parties
COMMON FORMS OF COMMUNICATIONS 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
Radio and TV broadcasting Telephone, wired and wireless Fax Pagers Computer networks: modem, e-
mail, Internet and World Wide Web, wireless
Satellites, radar, radio telescopes
KEY MILESTONES INELECTRONIC COMMUNICATIONS
1844 Telegraph 1876 Telephone 1895 Radio 1923 TV 1943 Radar 1946 Computers 1962 Satellites 1989 Internet
MODEL OF ALL COMMUNICATIONS SYSTEMS
TX RX
Noise
Communicationsmedium
Information to betransmitted
Received information
Transmitter ReceiverChannel
TYPES OF COMMUNICATIONS
TX RX
TX
TX
RX
RX
Simplex:One-way
Duplex:Two-wayHalf duplex:Alternate TX/RXFull duplex:SimultaneousTX/RX
Channel
Channel(s)
TYPES OF COMMUNICATIONS SIGNALS
Analog - smooth and continuous voltage variation.
Digital - binary or two voltage levels.
Time
COMMUNICATIONS SIGNAL VARIATIONS Baseband - The original
information signal such as audio, video, or computer data. Can be analog or digital.
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
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
High-frequency carrier
The modulating (baseband) signal is a sinusoid in this example.
An AM signal as it usuallyappears on an oscilloscope
The carrier frequency is normally muchhigher than the baseband frequency.
FREQUENCY MODULATION
The baseband signal controls the carrier’s frequency and the carrier’s amplitude remains constant.
Res
ting
f c
Incr
easi
ng f c In
crea
sing
f c
Dec
reas
ing
f c
Res
ting
f c
Mod
ulat
ing
sign
alC
arri
er
FM
MULTIPLEXING
Multiplexing (MUX or MPX) - the process of simultaneously transmitting two or more baseband information signals over a single communications channel.
Demultiplexing (DEMUX or DMPX) - the process of recovering the individual baseband signals from the multiplexed signal.
MULTIPLEXING AND DEMULTIPLEXING
MUX DEMUX
Single communications channel (radio or cable)
Original baseband information signals
Recovered basebandinformation signals
ELECTRONIC COMMUNICATIONS APPLICATIONS
Radio broadcasting (AM & FM) Television broadcasting (analog
& DTV) Cable TV Wireless remote control Paging Navigation and direction finding Telemetry
ELECTRONIC COMMUNICATIONS APPLICATIONS (Continued) Radio astronomy Surveillance RF identification (ID) Music services Telephones (wired, cordless,
cellular) Facsimile Two-way radio
ELECTRONIC COMMUNICATIONS APPLICATIONS (Continued)
Radar Sonar Amateur radio Citizens and family radio Data communications Networks Internet and World Wide
Web
FREQUENCY AND WAVELENGTH
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.
One cycle
time
PERIOD AND FREQUENCY COMPARED
Frequency = f = 1/T
T = One period
+
0 time
distance
Frequency and wavelength compared
f = 1/T
T
CALCULATING WAVELENGTH AND FREQUENCY
= wavelength in meters
f = frequency in MHz
= 300/f
f = 300/
ELF
103 m
107 m
104 m
105 m
106 m
10 m
1 m
10-1 m
10-2 m
10-3 m
10-4 m
102 m
300
Hz
30 H
z
30 k
Hz
3 kH
z
300
kHz
30 M
Hz
3 M
Hz
300
MH
z
3 G
Hz
300
GH
z
30 G
Hz
THE ELECTROMAGNETIC SPECTRUM FROM 30 HZ TO 300 GHZ
UHFVHFHFMFLFVLFVF SHF EHF
Frequency
Wavelength
Mill
imet
erw
aves
( = 300/f)
(f = 300/)
LOW AND MEDIUM FREQUENCIES
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 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
10-3 m
10-4 m
300
GH
zM
illim
eter
wav
esTHE ELECTROMAGNETIC
SPECTRUM ABOVE 300 GHZWavelength
0.8
x 10
-6 m
0.4
x 10
-6 m
Infr
ared
Vis
ible
Ultr
avio
let
X-r
ays
Gam
ma
rays
Cos
mic
ray
s
10-5 m
OPTICAL FREQUENCIES Infrared - 0.7 to 10 micron Visible light - 0.4 to 0.8 micron 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
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
Frequency Spectrum &Bandwidth
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) 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