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BENT 3113 Communication Principle

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Chapter1. Introduction2. AM3. Single Side Band4. Angle Modulation5. Noise6. Digital Modulation

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Chapter 1

Introduction to Telecommunication ----------------------------------------------------------------------------Outline :

- Introduction- Transmission mode - Electromagnetic frequency spectrum- BW- Type of electronic communications

- Wave propagation - Limitation in communication system

- Information capacity. - Power measurement

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Introduction to Telecommunications (CONT.)

People need communication

Traditional method Modern method

Problem

Upgrade the technology??

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Introduction to Telecommunications (CONT.)

pictures

Data / sms

Sound / music

Multimedia /mms

Save cost/time

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OVERVIEW ON TELECOMMUNICATION SYSTEM

Telecommunications is all about sending information to, and receiving information from a distant location with using integrated equipments

Nowadays we use Electronics communication as integrated equipment

The main function of electronics communication is to transfer information from one place to another place

Transfer information means : transmission , reception and processing information between two or more location using electronic circuit.

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Basic Element of Communication

Information

Transmitter

Medium

ReceiverInformation

Voice Informasi

Noise

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BASIC COMMUNICATIONS MODEL

This model is supposed to outline the concept of how communications flows between two points.

Communications Model

• The source is can also be called the sender. • The sink can be referred to as the receiver. • A message flows from the "Source" to a "Sink" through

a transmission path or circuit called Channel .

Source Sink

Sender Receiver

Media/ Circuit

Channel

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Simplified block diagramof an electronic communications system

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Basic Communication Model (CONT.)

• A detailed model of communication system can be represented as the following block diagram:

Sender

Modulator

Amplifier AmplifierChannel/

Transmission medium

Demodulator

Recipient

Noise

Type of Information Voice, Picture /video, Data

Transmitter Receiver

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Modulation at Transmitter

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Simplified block diagram of an analog communications system

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Transmission channel :

Physical link between the communicating parties.

Modulator : Transforms the source signal so that it is physically suitable for transmission channel.

Transmitter : Introduces modulated signal into the channel (usually amplifying the signal as it does so)

Receiver : Detects the signal on the channel and usually amplifies it (as it will have been attenuated by its journey)

Demodulator : Receives the signal source signal from the received signal and passes it to the recipient.

At its simplest, the system contains:

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Telecommunication Network

Terminal AccessNetwork

Switching (central)

Transmission- Satellite- Microwave- Submarine cable- Terrestrial cable

NetworkManagement

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Terminal

• Is an interface between user (person) and transmission– example : phone set, mobile set, TV, PC

• Include of appropriate “transducer”– Phone set : microphone, speaker– TV : CRT screen, speaker– PC : keyboard, mouse, CRT,– Video Camera : camera,

microphone– Video Conference : camera, screen CRT,

microphone, speaker

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Communications system can be designed for transmitting information in one or both direction.

Simplex, full-duplex and half-duplex system.

Equipt A Equipt B

Sender ?Receiver ?

Receiver ?Sender ?

Media/ Circuit

Channel

Transmission Mode

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Transmission Mode

Simplex (one way)• Duplex (two way –

two channel)• Asymetrix (two way

and different BW)

Half Duplex (two way – one channel)

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Transmission Mode Simplex System :

Capable of sending information in one direction only.Only sender can send and only recipient can receive E.G : public address system, TV and broadcast radio.

Half – Duplex System:Can go in both directions but in only one direction at a

time. E.G : two – way radio (walkie – talkie).

Full – Duplex System:Capable of sending information in both directions at thesame time. Two directional of information travel areindependent of each otherE.G : ordinary telephone systems, computer systems.

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Half – Duplex Full – Duplex

Limited bandwidth, number of wires or number of signal channels. Each user sharing same bandwidth or wires but at different time. Used when there is a need for 2-way information flow

Requires twice as much bandwidth as a half- duplex path. User do not have to take turns. More convenient to use and more efficient in an overall communication systems.

Half Duplex Vs Full Duplex

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SIGNAL

The signal can be represent in two type: Time domain and Frequency domain  

Ampl

Time domain

Time(sec)

Freq(Hz)

Frequency domain

f LOf HO

Ampl

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Wave form of analog signal

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

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Analog amplitude change smoothlyDigital data is universally represented by strings of 1s or 0s.

Example a signal that may vary between 0 and 15 has an information content of 4 bits.

Analog signal Digital signal

t

01

t

11

A A

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Electromagnetic Frequency Spectrum

• Communicating the information between two or more locations is accomplished by converting original information into electromagnetic energy and then transmitting it to the receiver station where it is converted back to its original form. This electromagnetic energy is distributed throughout an almost infinite range of frequencies.

The total electromagnetic frequency spectrum with the approximate locations of various services is shown below:

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Speed, Wavelength, Frequency

System Frequency Wavelength

AC current 60 Hz 5,000 km

FM radio 100 MHz 3 m

Cellular 800 MHz 37.5 cm

Ka band satellite 20 GHz 15 mm

Ultraviolet light 1015 Hz 10-7 m

Light speed = Wavelength x Frequency

= 3 x 108 m/s = 300,000 km/s

fx

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- EM Frequency is a natural resources- Radio frequency is a part of electromagnetic frequency

Electromagnetic Frequency Spectrum

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Electromagnetic Spectrum

SOURCE: JSC.MIL

SOUND LIGHTRADIO HARMFUL RADIATION

VHF = VERY HIGH FREQUENCYUHF = ULTRA HIGH FREQUENCYSHF = SUPER HIGH FREQUENCY EHF = EXTRA HIGH FREQUENCY

4G CELLULAR56-100 GHz

3G CELLULAR1.5-5.2 GHz

1G, 2G CELLULAR0.4-1.5GHz

UWB

3.1-10.6 GHz

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Wave length of electromagnetic wave spectrum

where = wave length C = speed of light f = working frequency = speed of EM wavef

C

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Abbreviation Frequency Applications

ELF (extremely Low) 30 – 300 Hz Sub marine communications

VF (Voice Freq) 03 – 3 KHz Telephony, data terminal

VLF (Very Low) 3 – 30 KHz Navigation, telephony

LF (Low) 30 – 300 KHz Navigation, radio beacon, power line comm.

MF (Medium) 0.3 – 3 MHz AM radio, amateur, mobile

HF (High) 3 – 30 MHz Radio control planes, mobile

Radio Frequency Spectrum

VHF (Very High) 30 – 300 MHz TV, FM broadcasting, air traffic control

UHF (Ultra High) 300 MHz – 3 GHz TV, mobile phones, satellite comm.

SHF (Super High) 3 – 30 GHz Radar, satellite links

EHF (Extremely High) 30 – 300 GHz Research, radio astronaut

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Bandwidthis the range of frequencies occupied by the signal.

Telephone speech typically occupies the range 300Hz to 3400HzBW = 3100 Hz

Audio signals analog :occupies a frequency range from about 200Hz to about 15KHz. BW= 15000 – 200 Hz = 14800 Hz

Analogue video signal is signal occupies range 0 to 4MHz BW = 4MHz

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Bandwidth

- Bandwidth signal at the certain position point is not the same-Bandwidth of a channel transmission ?

Signal ABW = a

Channel transmission / Media/ Circuit , BW = B

There will be two possibilities :1. a>b ?2. b>a ?

Example: Analogue video signal is signal , BW = 4MHz

Metal pair line, BW = 5.6 kHz

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Example

For a sinusoid 50 MHz signal, finda. Wavelength b. Periodc. Draw wave form