doordarshan pptg

8/8/2019 DOORDARSHAN PPTg

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WHAT IS COMMUNICATION ?

BLOCK DIAGRAM OF EARTH STATION.

UPLINKING.

DOWNLINKING.

BASIC OF DTH (DIRECT TO HOME).


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COST OF TRANSMISSION IS INDEPENDENT OF DIST. INVOLVED.

MULTI-ACCESS TWO WAY COMMUNICATION

CAPABLE OF HANDLING VERY HIGH BANDWIDTH. LARGE AREA CAN BE COVERED.

CAN PROVIDE SIGNALS TO TERRESTRIAL UNCOVERED POCKETS LIKE VALLEYS ,

MOUNTAINS ETC.

PROVIDE UNIFORM SIGNAL TO URBAN AREAS AS WELL AS RURAL AREA UNLIKE

TERRESTRIAL SERVICES.


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C-BAND FREQUENCY : 3.4 GHz TO 4.2 GHz

KU-BAND FREQUENCY : 13.75 TO 14.50 GHz

L-BAND FREQUENCY : 950 TO 1750 MHz


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RECEPTION OF TURN AROUND CHANNEL

FROM INSAT 3A , AND 4B.

COMBINE THESE CHANNEL IN DIGITAL

MODE.

MODULATE AND TRANSMIT ABOVE

CHANNEL TO INSAT 4B.

MONITORING OF CHANNEL DOWN LINKED

BY INSAT 4B USING 1.2 m ANTENNA.


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LINK B/W EARTH AND SATELLITE FOR TV TRANSMISSION

VIDEO

PROCESSOR

OPTIMOD

ENCODER

+

MODULATOR

POWERAMPLIFIERUP-CONVERTER

IRD

(INTEGRATED

RECEIVER

DECODER)

VIDEO I/P

AUDIO I/P

70 MHz

(I.F.)

C-BAND

RF SIGNAL

VIAWAVEGUIDE

V

A

FIG. BLOCK DIAGRAM

(TWT,KHPA)


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TWO METHODS:

4:2:0 ---------------67% B.W. SAVED

4:2:2----------------48% B.W. SAVED


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F.E.C. : FIELD ERROR CORRECTION - ( , , 5/6 )

B.E.R : BIT ERROR RATE

BER = ERROR BITS PER TOTAL BITS TRANSMITTED .

EX: BER OF 1 X 10-3

NOISE IS INTRODUCED DUE TO STORMS, NON-LINEARITY OF DEVICES, THERMAL

NOISE.

HIGHER C/N RATIO IS PREFFERED FOR BETTER ERROR PERFORMANCE


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LNBCC TO L BANDCONVERTER

LNA

IRD


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RF I/P FREQ. : 3.2 GHz 4.2 GHz

IF O/P FREQ. : 950-1750 MHz

GAIN : 55 DB 70 DB

I/P DC VOLTAGE : +15V TO +24V

I/P INTERFACE : CPR-229G

O/P INTERFACE : F-TYPE, 75 OHM


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THE LNA IS USED TO AMPLIFY THE SIGNAL RECEIVED AT ANTENNA FEED TO A

LEVEL WHICH CAN BE PROCESSED FURTHER.

IT IS USED FOR THE AMPLIFICATION OF VERY LOW SIGNAL.

THE OUTPUT OF LNA IS FURTHER GIVEN TO CONFIDENCE MONITORING SYSTEM

AND BEACON TRACKING RECEIVER.

EXTERNAL 24 V IS GIVEN TO THE LNA.


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UPLINK FREQUENCY : AT WHICH MESSAGE SIGNAL IS UPLINK TO SATELLITE.

DOWNLINK FREQUENCY : AT WHICH MESSAGE SIGNAL IS RECEIVED FROM

SATELLITE.


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SYSTEM IS INTENDED FOR PROVIDING DTH SERVICE OF 10 VIDEO CHANNELS

THESE TV CHANNELS HAVE DVD QUALITY AS ENTIRE PROCESSING IS IN DIGITAL

DOMAIN.

THESE CHANNELS ARE RECEIVED VIA 1.2m ANTENNA.

IT USES KU BAND FOR THE TRANSMISSION PURPOSE.

IN ANDAMAN AND NICOBAR ISLAND DTH IS PROVIDED THROUGH C-BAND FREQ.


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