satalite communication

8/9/2019 Satalite Communication

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Presented by

SATELLITE COMMUNICATION

KALPESH B. PANCHAL

BIREN A . PATEL

GOVT. ENGG. COLLEGE

GANDHINAGAR

SEC : 26


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CONTENTS

# Overview of satellite communication

# Satellite orbits# Spacecraft & its Subsystem

# Multiple access techniques

# Antenna# Earth stations

# Indian Activities in satellite communication


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OVERVIEW

# Satellite communication means communication

through satellites.

# A satellite is held in its circular Or elliptical orbit

trajectory by combination of its gravitational

force and its tangential velocity.

# Satellite forms an essential part of the

telecommunication


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ADVANTAGES :

1. Long distance communication with higher capacity.

2. Satellite can be installed rapidly.

3. The mobile communication can be easily achieved by

satellite system as it has a unique degree of flexibility in

interconnecting mobile vehicles.

4. The satellite costs are independent of distance.


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DISADVANTAGES :

1. Delay of th second between the transmission

and reception of signal

2. Repairing any part of the satellite after launching is very

difficult.

3. To launch geo-stationary satellite in space more powerful

launch vehicles are required and thus the high cost of

launching can affect the total cost for communication.

4. High free space loss.


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PASSIVE SATELLITES

In passive satellite the transmitter of the ground station

requires large power and the receiving station receives a

fraction of that power and then it is amplified by active

electronic means,

like ECHO-I, ECHO-II.

ACTIVE SATELLITES

In active satellite system on board transponder is used by

which the signal the earth Station is received, amplified,down converted and retransmitted for another earth

station thus the required power of the transmitting earth

station is law,

like SCORE.


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SATELLITE APPLICATIONS

# In communication such as

T.V.,telephony data transfer

such as E-mail and internet etc.

# Remote sensing and earth observation can be done

by LEO satellites.


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# Meteorological applications

such weather survey,

to study different layer and amount of ozone

contents in the atmosphere.

# Military applications

like short distance local communication

from one to another, to study the

location of the enemy, etc.


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SATELLITE ORBITS

The path in which the satellite goes around the

earth is called orbit path and the distance from

the centre of the earth to the satellite is called

orbit radius.

Satellite can be classified in terms of altitude

as follows:

# Low Earth Orbit (LEO) satellite

# Middle Earth Orbit (MEO) satellite

# Geo-stationary Earth Orbit (GEO) satellite

# Highly Eccentric Orbit (HEO) satellite


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ATTITUDE CNNTROL SYSTEM (ACS)

A spacecraft may stabilize in two ways-

Spin stabilization

which maintains the spin axes in the same

direction. Spin stabilization is used for cylindrical shapedsatellites.

Three axes body stabilization

A satellite can rotate about the three axes termed as yaw, roll

and pitch axes. A satellite is stabilized about these axes.


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TELEMETRY TRACKING AND COMMAND (TT & C)

# TELEMETRY

# TRACKING

# COMMAND


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TRANSPONDER

Transmitter-receiver system taken together is known

as a transponder.

A transponder is the series of interconnected units which

form a single communication channel between the receive

and transmit antennas in a communication satellite.

The choice of the transponder bandwidth depends on the

nature of the signal to be carried by the satellite and the

multiple access technique used.

6/4 GHz BAND


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LAUNCHES & LAUNCH VEHICLES

Two technologies can be

used for satellite

launching:

# Expandable launch

vehicle (ELV)

# Space shuttle (STS)


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MULTIPLE ACCESS TECHNIQUES

There are three types of multiple

access techniques :

# Frequency Division

Multiple Access (FDMA)

# Time Division Multiple Access(TDMA)

# Code Division Multiple Access (CDMA)


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ANTENNA

It is the most important component of an earth

station through which the transmitter and receivers

of earth stations establishes link with the satellite.

An Earth station antenna should have high directive

gain, low noise temperature and

Easily steerable.

There are two types of antennas:

1. Horn Antennas

2. Parabolic Reflector


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Radiation Patterns:

1. Spot & Zonal beams:

It covers 10% of earth space. o/p power

required more to focus on particular area.

2. Hemispherical beams:

It covers 20% of earth space. o/p power required

less than 50% compare to spot & zonal beams.

3. Earth (global) beams:

It is covers 42% area of earth surface. Its required power

is less compare to other. Its beam width is more.

Reuse: when frequency band is filled, the capacity

can increase by reuse frequency spectrum.

# By increasing size of Antenna.

# By use of dual polarization.


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EARTH STATION

A ground based communication facility capable of

transmitting, receiving and processing data relayed to andFrom orbiting satellites .

There are three types of earth stations :

1. Transmit Receive Earth Station:

In this type the earth station can transmit signal forsatellite as well as can receive the signal from

the satellite. Like telephony, data transfer etc.

2. Receive Only Earth station :

These earth stations can receive the signal from a

satellite but not transmit any thing towards the satellite.These station are mostly used in CATV systems.

3. Transmit only Earth Station :

Here the earth station can transmit signal only towards

The satellite and mostly used in data collection systems.


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INDIAN ACTIVITIES IN SATELLITE

COMMUNICATION

In 1972, Indian Space Research Organization

(ISRO) was established at Bangalore under the

department of Space Govt. of India.

The two important experiments were performed

by ISRO scientists for the development of

Satellite program,

which are as follows :

# Satellite Instructional Television Experimental

(SITE) program

# Satellite telecommunication Experiment

project (STEP)


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1. Satellite Instructional Television Experimental

(SITE) program

organized between 1975 and 1976 using the ATS-6

satellite of NASA.

This program helped to design and test

uplink stations, testing of TV sets.

2. Satellite telecommunication Experiment

project (STEP) was completed during

1977-79. The project was mainly to

perform experiments with digital satellite

communications, radio networking and

TV transmission with several audio

channels.


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APPLE was the first Indian experimental

satellite launched in the year of 1981,

had a microwave c-band transponder. It is

very helpful for testing of computer

communication, TDMA communication,FAX transmission and TV

broadcasting, APPLE thus

gave a strong foundation

to India for fixed satellite

system (FSS) that led tothe development of

INSAT series

Of satellites.

APPLE


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INDIAN NATIONAL SATELLITE SYSTEM

(INSAT)

INSAT is a multipurpose satellite system for

telecommunications, broadcasting,Meteorology and search services.

INSAT was the largest domestic communication

system In Asia-Pacific region.


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