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