training presentation by lokesh jain

8/3/2019 Training Presentation by Lokesh Jain

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Lokesh Jain

B.TECH. VII SEM. (ECE)

EC-1

MNIT, Jaipur


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A

Practical Training

Presentationon

Doordarshan Kendra, Jaipur


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Contents:-

1. Introduction

2. Basics Of Tv (Pal) Signal

3.Pre-Production

-Light-Camera-Microphones

4.Production-CCU

-MSR-VM

5. Satellite Communication

6. Setup In Rajasthan


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History-

In 1930, radio broadcasting was started.

In March 1935, Govt. took over charge of broadcasting.

In 1936 All India Radio(AIR) came into the force.

In 1956 AIR changed to Aakashwani.

Doordarshan started in India in 1959 with black & white

transmission.

In 1982, B&W transmission was converted fully into colour

transmission during asian games.


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The first Television Programme was viewed by the

people of Rajasthan on 1st August 1975 under the

Satellite Instructional Television Experiment in the

districts of Kota, Sawai Madhopur and Jaipur.

On 1st March 1977, Upgrah Doordarshan Kendra

(UDK) was set up at Delhi.

The programmes were produced at UDK for Jaipur .


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Intro cont...

On 1st June 1987, Jaipur Doordarshan Kendra was set up atJhalana Doongri and transmission started on 6th July 1987.

Initially the Kendra produced only 30 minutes of programmingand this was gradually increased to about 4 hours.

From 2nd Oct. 1993, the LPTS located at Ajmer, Udaipur,Jodhpur and Bikaner and HPT at Bundi were connected withDDK Jaipur via satellite.

Doordarshan Jaipur is the only Programme Production Center inRajasthan. The studios are housed at Jhalana Doongri, Jaipurand the transmitter is located at the Nahargarh Fort.


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BASICS OF TV (PAL) SIGNAL-

Video is nothing but a sequence of pictures.

The impression made by any light seen by the eye persists

for a small fraction of second(1/16s) .

If enough pictures are presented to the eye during the

interval, the eye will integrate them and it create illusion of

motion. This is called Persistent of Vision.

In PAL TV system repetition rate is 25 frame/sec.


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In case of TV camera scene is focused on the photosensitive

surface of the pick up device and a optical image is formed.

Like CCD device.

Electron beam scans the charge image and produces optical

image.

Scanning is done in both horizontal & vertical direction

simultaneously.

Hor/ Ver scanning freq are 15625 & 50 Hz.

The frame is divided in two fields.

Odd lines are scanned first and then even lines.

The odd and even lines are interlaced.


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Interlacing reduces flicker.

Frame rate is 25 Hz, Field rate is 50 Hz.


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Work at DDK is divided into 3 parts-

1. Pre-production

2. Production

3. Post-production


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Pre-Production(TV Studio)-

A television studio is an installation in which

television or video productions take place .

1. Light2. Camera

3. Microphone


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STUDIO LIGHTING-

Parameters of lights are-Quantity- Amount of radiated energy by the source of lightQuality- Type of light source used

Contrast ratio- Difference between highly lighted and darkest

part of the scene.

Colour temperature- Different lights and colors have their owntemperature.

Source TemperatureSun Light 5600 KelvinStudio Lamp 3200 Kelvin

Domestic Lamp 2780 KelvinFire 1930 KelvinFluorescent 6500 KelvinCloudy Day 6500 Kelvin


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Balancing of Lighting-Key Light 100%Fill Light 85%Back Light 110%Back Ground Light 50% - 60%

Types of Lights-

Key light- the main light used to highlight any object or to

give attention towards the person.

Fill light- used to suppress the shadow made by key light.

Back light- used to seperate artist from the background andso to produce 3d visualization by lighting the head and

shoulders.Background light- used to highlight the background of thescene or to create color background on white cyclorama.


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CAMERA-

A typical video camera have following sections-

Lens

Optical Block

Transducer or pick up device

Electronics


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Production-

1.Camera Control Unit(CCU)

2.Master Switching Room(MSR)

3.Vision Mixer(VM)


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Camera Control Unit

The output of Studio cameras ispre-amplified and then connected

to the camera control unit (CCU)through long multi-core cable (35

to 40 cores).

Many Parameters of Video SignalsLike Voltage level, color correctionare controlled From CCU.

.


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Master Switching Room

It is the heart of the studio.

Most of the switching electronics is kept.e.g. camera base stations, switcher main

frame, Satellite receivers, MW link, & mostof the patch panels.

Signal is routed through MSR.

Signal can be Monitored at various stages.


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VISION MIXER-

A vision mixer(production switcher) is one of the primary device

used to produce a television program.

Production switcher is used to either switch or cut between two

video sources, or to combine them in a variety of ways.

The principal methods used to combine video are- Mixing,

Wiping,& Keying.


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Satellite in general is a Follower. A heavenly body whichfollows a planet is called a satellite.

Wireless World in 1945, A radio relay satellite in an

equaqtorial orbit with of 24 hours would remain stationarywith respect to earths surface and make possible longdistance radio links.

Birth of satellite commnication in Oct.,1957.

Started in 1960.

Started in India in 1975 .

First Indian Satellite INSAT launched in 1982 .


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Satellite Transmission

Frequency bands

Frequency band Range

C-band 4-8GHzX-band 8-12 GHzKu-band 12-18GHzKa-band 27-40GHz


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Satellite Transmission:

C - Band

Frequency band 4.0 to

8.0 GHz

Large sized dish required

for reception

Useful to SystemProviders / Cable

Operators

Ku -Band

Frequency Band 12.5 to

18 GHz

Smaller dish ( 6090

Cms) needed for

reception

Most useful for DTH

application


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Satellite

User

Terrestrial Network

Earth Station

User

Terrestrial Network

Earth Station

Basic Satellite System


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Why uplink frequency is always higher

than downlink frequency ?

1) To avoid Interference between Uplink and Down link.

2) Because the Satellite has a limited RF Power outputand Transmission Loss diminishes as frequencydecreases


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Earth Station is a very important part of satellitecommunication system for broadcasting of signals.

It is an uplink center from which the signals are fed to Satellite

for distribution in a specified area covered by the Satellite.

The signal is up-linked from the Earth Station and received by

many down link centers in TV broad casting via PDA.

Earth Stations is purely Digitization version.


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Major Components of Digital Earth Station:-

PDA (Parabolic Dish Antenna)

Wave Guide / Low Loss Cable

HPA (TWT, Klystrons)

Up & Down converter

Modulator & Demodulator


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Encoder

LNADown-

ConverterDecoder

Modulator

Demodulator

Up

ConverterHPA

Base

Band

equip-

ment

TerrestrialNetwork

Antenna


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Up-Converters:-

Up-Conversions is required to raises the frequency of signalin desired band:- C-band, Extended C-band or Ku bandBefore transmisson.

I/P of Up-Converter is 70 MHz. O/P is fed to the HPA.

The Up- Conversion may be done in stages or in one stagedirectly.

Normally L-band monitoring point is also provided in Up-converters for monitoring purposes.


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High Power Amplifier:-

HPA is used for the final power amplification of digital RF

signal in C-Band/Ku band that is fed to the antenna.

The order of magnitude of the power required at the

transmitter output is 300 to 500 watt.

Different types of HPAs are:-

1. Klystrons

2. TWTA


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Low Noise Amplifier:-

LNAs are used in earth station to

minimize the noise generated during

launching mechanism of satellite andraises the SNR of received signal.


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Down-Converters:-

Downconverter receives the modulated RF carrier fromthe LNA & translates its radio frequency specturm of thesatellite & intermediate frequency.

The Down Conversion process can be achieved by thesingle conversion or dual conversion prosess, similar toup-converter.


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Earth Station Antennas:-

Earth Station antennas provides means of transmitting and

receiving the signals by uplink and down linktransmission in frequency spectrum.

Antenna must have a highly directive gain that is, it mustfocus its radiated energy into a narrow beam to illuminate

the antenna in both transmit & receive modes so that itprovides the required uplink and downlink carrier power.


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Cont..

Antenna must have a low noise temperature so that theeffective noise temperature of the receiver side of earthstation can be kept low to reduce the noise power within

downlink carrier bandwidth.

Antenna must be easily steered so that a tracking systemcan be employed to point the antenna beam accuratelytowards the satellite, taking into account the satellites

drift position.


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Two type of antenna are used in Earth station-

Paraboloid Antenna

Cassegrain Antenna

Paraboloid Antenna Cassegrain Antenna


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Applications:

1. In Communication such as TV, Mobile communication,

data transfer such as E- mail and internet.

2. Militray applications like short distance local

communication from one camp to another & also in radars.


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Modes--Terrestrial (Area coverage72%)-Satellite (Area coverage100%)

Transmitters90

SatelliteINSAT

Satellite Position - 93.5 E

Uplinking frequency6165.5 MHz

Downlinking frequency3940.5 MHz


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training presentation by lokesh jain

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