Sat Overview -1

8/6/2019 Sat Overview -1

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Satellite Communications An

overview


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Brief Outline

Need of Satellite Communication

History and Evolution

Satellite Systems and Components.

INSAT Satellite System.

Applications of Satellite Communication


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SATELLITE COMMUNICATION

Satellite communication is a kind of microwave communication

with a repeater placed in space.

Today Satellite Communications does not competewith but complements the terrestrial

modes of communication like optical fiber andMicrowave communication.


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Geo stationary Satellite 35,768 km above surface of the earth.

Sidereal Day : 23 hr 56 minutes and4.1 sec.

Geo synchronous vs Geostationary orbit.

Non GEO orbits : LEO, MEO.


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1. Only one repeater in the link

2. Covers 1/3 of earths surface.

3. Provides high quality communication.

4. Insensitive to fading.

5. Large areas could be covered if the height of themicrowave repeater could be increased by putting

it on board an artificial earth satellite (FIG. 1).


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SATELLITE

REPEATER

10000 KM

1500 KM

750 KM

50 KM

MAXIMUM COVERAGEEARTH

LOS

RADIO RELAY

TROPOSPHERIC

SCATTER

IONOSPHERIC

REFLECTION

(HF RADIO)

FIG. 1: MODES OF COMMUNICATION


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The origin of satellite communication can betraced to an

article written by Arthur C. Clarke in British radio

magazine Wireless World in 1945.


History andEvolution

In 1957 Russian satellite Sputnikwas launched .


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EARTHEARTH

3

6,0

00KM

PERIOD24 HRS

EQUATOR

GEO-STATIONARYORBIT

FIG. 2: GLOBAL COVERAGE WITH GEOSTATIONARY SATELLITES

CLARKES CONCEPT

GEO-STATIONARY

ORBIT

THE EARTH


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20 years later in 1965 INTELSAT launched firstgeo-

stationary communication Satellite namedEARLY

BIRD

The satellite was having the capacity of 240 voicecircuit . The satellite weighed mere 36 kgs (80 lb) andincorporated

02 nos of 6/4 GHz transponders, each with 25 MHz

bandwidth. The satellite was used commercially forcommunications

between Europe and United States.


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Rapid advances in launch vehicles & developmentsin reliable microwave devices,have made satellitecommunication systems quite affordable andcommon.

The present generation satellites carry a no of radiochannels called communication Transponders andhave the expected life span of 10 to 12 years.


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ADVANTAGES OF SATELLITE COMMUNICATIONS

(i)Large Coverage

Almost one-third of the earth with theexception of

polar regions, is visible from Geo stationaryorbit.

(ii) High Quality

Satellite links can be designed for high quality

performance. It is free from Ionospheric

disturbances and multi-path effects.

(iii) High Reliability

Reliability is high since only one repeater is

involved


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A Communication satellite essentially consists of two parts

i) Communication Subsystem consists of communicationtransponders & transmit/receive antenna.

ii) Support Sub-system consists of

a) Structure

b) Attitude and orbit control System (AOCS).

c) Propulsion system

d) Electric Power System

e) Thermal control

f) Telemetry and Tele command system


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A communication subsystem consists of

Antennas : transmit and receive over wide range of microwave frequencies.

Transponders : A set of transmitters and receivers that amplify and

retransmit the incoming signal.

Communication Subsystem

A Transponders consist of a band pass filter, a

down converterand an output amplifier.


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L 1-2 GHz

S 2-4 GHz

C 4-8 GHz

X 8-12 GHz

Ku 12-18 GHz

K 18-27 GHz

Ka 18-40 GHz

V > 40 GHz

M/W Frequency Bands


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C- Band :

U/L : 5.925 6.425

GHz.D/L : 3.7 4.2 G Hz.

Total 500 M HzBW.

Frequency BandsFor Satellite Communication

Extended C- Band :

U/L : 6.725 7.025 GHz.

D/L : 4.5 4.8 G Hz.

Additional 300 MHz BW.

Ku band :

U/L : 14.0 - 14.5 G Hz.

D/L : 10.95 11.2 and 11.45 - 11.7 GHz.

A total of 500 MHz BW in Ku band.


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Tracking of the Satellite : Azimuth and Elevation.

Satellite E/S

Main advantage with Ku band is that E/S can be located anywhere even

in the heart of the city.

U/C HPAMODIF

Amplifier

Base-band

HPA Types

Klystron : 1.5 kW, BW 40 MHz

TWT : 400 W, BW 500 M Hz

SSPA : up-to 1 K W,500 M Hz.


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Figure of Merit : G/T

Satellite E/S

G : Receive gain of Antenna in db.

T : Temperature of the system in degree K.

In our INSAT network -

Type ofStation

AntennaDia M

LNA

K

G/T

db/K

Type A 11.0 40 31.7

Type B 7.5 90 25.7

Type C 4.5 120 19.7


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36 M Hz is widely used as transponder BW, with 54 and 72 M Hz adopted

for some satellites.

Transponders

6 additional Transponders ( Tx no. 13 to 18 ) are

present in additional 300 M Hz band in extended C-band in INSAT s stems.

The narrower bandwidth is preferred for transponder to avoid inter-

modulation distortion likely to occur when high power amplifier ( TWT) is

driven close to saturation.

Satellites operating in 6/4 G Hz band carry 12 transponders.

24 transponders can be accommodated in 500 M Hz BW through

frequency reuse by orthogonal polarizations.


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SATELLITE AND TRANSPONDER CAPACITIES

S. No. Name of

Satellite

Transponder Capacity

Orbit Location

(Long itude)C- Band Ext-CBand

Ku-Band

S- Band

Mobile(MSS)

(CxS &SxC)

(i) INSAT-1D 12 - - 2 - 83 0 E

(ii) INSAT-2A 12 6 - 2 - 74 0 E

(iii) INSAT-2B 12 6 - 2 - 93.5 0 E

(iv) INSAT-2C 12 6 3 1 1 93.5 0 E

(v) INSAT-2E 12 5 - - - 83 0 E

(vi) INSAT-2DT 25 - - 1 - 55 0 E

(vii) INSAT-3B - 12 3 - 1 83 0 E


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Satellite Footprint

Satellite - D/L EIRP 32 dbw at Beam center.

Beam center - Jabalpur or Nagpur.

Primary Coverage Area - 3 db contour EIRP 32 dbw .

Secondary Coverage Area - 6 db contour EIRP 29 dbw .

Tertiary Coverage Area - 9 db contour EIRP 26 dbw .


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Link Engineering

Input Saturation Flux Density : Power required at the input of antenna to

get 32 dbw EIRP.

-80 dbw/sq. m.

Satellite - D/L Power EIRP 32 dbw.

Input Back off : 10 db.

Output Back off : 4 db.


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Multiple Access Method

FDMA -

TDMA -

ALOHA -

CDMA -


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Applications

Emergency Communications Disaster Management.

Communication in difficult and hilly terrains.

Mobile Satellite Services MSS.

Digital DBS-TV.

Satellite Navigation Systems- GPS, Glonass, Galileo.


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FORWARD

S-BAND

RETURN

S-BAND

Portable Mobile Earth Station

RETURN

S-BAND

FORWARD

S-BAND

RETURN

S-BAND

HUB

PSTN PSDN

INSAT-MSS Network Configuration

Maritime Mobile Earth Station


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INDIAN COMMUNICATION SATELLITES LAUNCHED SO FOR.

NAME OF SATELLITE DATE OF LAUNCH LAUNCH VEHICLE

APPLE JUNE 19, 1981 ARIANE

INSAT-1A APRIL 10,1982 DELTA (US)

INSAT-1B AUGUST 30, 1983 US Space Shuttle.

INSAT-1C JULY 22, 1988 ARIANE

INSAT-1D JUNE 12, 1990 DELTA (US)

INSAT-2A JULY 10, 1992 ARIANE

INSAT-2B JULY 23, 1993 ARIANE

INSAT-2C DECEMBER 7, 1995 ARIANE


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(INSAT 2-D FAIFED AFTER 2 MONTHS OF ITS LAUNCH.)

INSAT-2DT JANUARY, 1998 IN-ORBIT

(Satellite was purchased from ARABSAT communication payload withdrawn now)

INSAT-2E APRIL 3,1999 ARIANE

INSAT-3B MARCH 22,2000 ARIANE

GSAT-1 APRIL 21, 2001 GSLV

INSAT 3C January 24 2002ARIANE

I

NSAT 3A 10th April 200 3 ARIANE

(INSAT 2D failed after 2 months of its launch.)


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SATELLITECOMMUNICATION IN INDIA

(A)EXISTING EARTH STATIONS.

1. TYPE A (MAIN Earth station) 14

2. TYPE B (PRIMARY Earth station) 59

3. TYPE C (REMOTE Earth Station) 13

4. MCPC VSATs 345

5. IDRs (Digital Satellite Equipment 56

6. Analogue SATCOM Equipment. 216voice ccts7. Total VSATs including private. 24000

Types of Services available via Satellite.

1. Point to multipoint video service

2. Point to point Telephone service

3 Remote area business messaging service.

4. Multi channel per carrier (MCPC-VSAT)


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6. High Speed VSAT Network. (HVNET)

7. Fly Away Terminals for Emergency communication.

Satellites used for providing services in INDIA.

1. Insat 2E

2. Thi com 3

3. Insat 3B.

4. Insat 3C.

5 Intelsat 703

6 Insat 3A.


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MCPC V-SAT

Govt of India Plan

All Tehsil HQs to he connected on STD map

irrespective of their exchange capacities.

All industrial growth centers, important

tourist places should be provided with STD

facilities.

All such divisional HQs and exchanges of

more than 500 lines are to he linked to


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VSAT to VSAT Communication via HUB


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Objective:- to have a reliable x mission media

between trunk exchanges and the places

mentioned above.Present scenario :- for some places mentioned

above networks are based on O/H lines

running through forests to having difficultterrain and therefore are vulnerable.

At many places the traffic is thin and even 2

hop UHF sys. is not fear able.

MCPC V-SAT


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MCPC is a sat. based network and is very

much reliable.

It provides connection between RAX ANDTAX directly W/O involving any link in

between these two points.

MCPC provides.Voice chls 7 (16KBPs each)

Esc 1 (9.6KBPs)

MCPC V-SAT


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Data chls.of 19.2 kBPs 4 ( in lieu of voice)an a signal carrier chl.

Network Design.

In case of SCPC one carrier is used for onevoice chl.

For N Voice chls. The requirement will use

N carriers.This needs a back off power in HPA, on theother hand if a no. of chls are carried on onecarrier, the size of the HPA will be reduced.

MCPC V-SAT


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MCPC is basically a digital system, BB is

converted to If by QPSK Mod. Tech- Max bit

rate offered is 128kBPs for 8 channel.Any sat station is broadly sub divided into 3

sub. Systems.

i. Antennaii. RF/IF Unit.

iii. Base band unit.

MCPC V-SAT


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MCPC Network ARCHITECTURE has two

main parts.

1. Hub station

2. Remote STN (V-SAT)

MCPC V-SAT


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SINGLE VOICE CHANNEL

FLYAWAY TERMINALS FOR CRISISMANAGEMENT

SUITCASE TYPE TERMINAL FOR VVIPsPROVISION OF TELEPHONE TO GRAME

PANCHAYAT

LONG DISTANCE SATELLITE TELEPHONE

MULTIPLE VOICE TERMINALSMCPC VSAT FOR PROVIDING LONG DISTANCETRUNK CIRCUITS TO REMOTE, HILLY AND

INACCESSIBLE

RURAL COMMUNICATION


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INTERACTIVE DATA COMMUNICATION AT

SPEEDS UPTO 1200 Bps IN GENERAL BUT LIMITED

TERMINALS UPTO 9600 Bps

ACCESS TO PUBLIC TELEX NETWORKS

ACCESS TO PACKET PUBLIC SWITCHED DATA

NETWORKS (I-NET)

ACCESS TO INTERNATIONAL DATA NETWORK

THROUGH (GPSS)

PRESENTLY 500 VSATS (CAPACITY 1000 VSATS)

RABM NETWORK OFFERS


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USES SSMA

MASTER EARTH STATION ( MES) COLOCATED WITHDOTs DELHI EARTH STATION AT SIKANDRABAD

(UP) MICRO EARTH STATIONS AT USERs PREMISES

STAR CONFIGURATION OF N/W

SPACE SEGMENT (INSAT-3C)

MASTER EARTH STATION IS CONNECTED TO DELHI

TRANSMISSION CENTRE BY MICROWAVE/ OPTICALFIBRE LINK.

MICRO EARTH STATION HAVE BEEN SUPPLIED BYM/s IESL BANGALOURE.

V-SAT COMMUNICATION

RABMN

Documents

Sat Overview -1