terrestrial broadcasting 1

8/8/2019 Terrestrial Broadcasting 1

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Generation of C C V S

Review of the PAL Composite Video Signal

Starts with the RBG component signal.

Matrix creates color difference YUV signals.

Analog Composite

Video (PAL)

R

Y

V

U

COMPOSITE

ENCODER

B

G

Composite

Analog Video(RGB)

Color Difference

Composite

Analog Video (YUV)

M

A

T

R

I

X



TIMING DETAILS OF C C V S

Sync and Burst Amplitude both should be 300mv.



COLOUR TRANSMISSION



SATELLITES

Presently to INSAT-2A (74oE) andINSAT-2B (93.5oE) and INSAT 2E (83o

E). Down link frequency bands beingused are C-Band (3.7-4.2 GHz) and Ex-C Band (4.5-4.8 Doordarshan is up

linking its national, and regionalservices



TRANSMISSION OF BASE BAND

TO SATELLITE

The base band signal consists of video (5 MHz),two audio subcarriers (5.5 MHz & 5.75 MHz)

and energy dispersal signal (25 Hz). Aftermodulation (70 MHz) and upconversion (6 GHz)the carrier is amplified and uplinked throughSolid Parabolic Dish Antenna (PDA). Down linksignal can be received through same PDA using

Trans-Receive Filter (TRF) and Low NoiseAmplifier (LNA). After down conversion to 70MHz, it is demodulated to get audio and video.



EARTH STATION UP

LINK/DOWN LINK



SATELLITE TRANSPONDER



Figure of Merit (G/Teq)

Down link Carrier to noise density of a

satellite down link signal is given as

( ) k loss Path

T

G EIRP

N

C

eq

sat

Do

−−+=

where k is boltzman's constant (-228.6 dB/degree

Kelvin



Azimuth and

Elevation

Both the azimuth and elevation of a dish can

be affected by three factors for geo-stationarysatellites. They are The longitude of the

satellite. The latitude of the place. The

longitude of the place.



LATITUDE AND LONGITUDE

LATITUDE ASANGULAR DISTANCEPARALLELSOF LATITUDE



LONGITUDE



CALCULATION OF ANGLE OF

ELEVATION

Where

R = Radius of the earth (6367 kms)

R = Radius of Synchronous orbit (42,165 kms)

Ø = Latitude of the earth station

D = difference in longitude of the earth

station and the satellite. (λ r - λ s)

( )

φ−

−φ= −

2

1

Cos.DCos1

R

r Cos.DCos

tanElevation



CALCULATION OF AZIMUTH

where D = λ r - λ s in degrees.

Ø= latitude of the given site in degrees.

λ r = longitude of the given site indegrees.

λ s = longitude of the satellite.

( )( )φ sintantan180 1 Dazimuth o −

±=



POLARIZATION

Circular or Elliptical

Right hand circular (RHCP) b)Left half circular (LHCP).

LINEAR POLARIZATION

Vertical (v) b) horizontal (h)



SYNTHESIZED TVRO SYSTEM



LOW NOISE BLOCK

CONVERTER



TVRO BLOCK DIAGRAM



PSU PSU PSU

AVR 50KVA Isolation

TFR 50

KVA

P s

1 - P

s 5

PA 1

PA 1

PA 1

PA 1

PA 1

PA 1

PA 1

PA 1

8

W

A

YS

P

L

I

T

TE

R

8

W

A

Y

CO

M

B

I

N

ER

AHU

Driver A

LCD

Touch

Screen

Driver B CPU

CPU

Multiplexer

input output

VA

V

A

EX-B

EX-AVrf O/P Diple

xer

CIBD

3 dB

Divider

PA 1

PA 1

3 dB

Divider

1600w6dBArf

13dBm

6dB

Driver A&B

CPU

To Txr



Video + IF

Processor

EXITER

IF/RF

Converter

Interconnection Board

Sound + IF

Processor

IF/RF

Converter

Local

Osc.

Video I/P

1V PP

75Ω

IF O/P

38.9 MHz

-4 dbm VRF O/P

19 dbm

For Ch#5

175.25 MHz

To Control

System

600Ω

+6dbm

Audio2

Audio1

180.25 MHz

For Ch # 5-4dbm

IF O/P

33.4 MHz

ARF O/P

13 dbm

For Ch#5

214.25 MHz



AURAL MODULATOR



Representation of the side bands

in VSB transmission

Sound Carrier Picture Carrier

Parto

fL.S

.B

U.S.B

-1.25 –0.75 0 5 5.5

Frequency MHz



RECEPTION OF VESTIGIAL SIDE

BAND SIGNALS

1600 O



1600 W POWER AMPLIFIER

PhaseGain2 dbm

I/P T8MRF

182

Hybrid

MHL

8118

Pre-Amp

T7

Driver

AB

Driver

Driver

PCB

3

WA

Y

S

S

P

L

I

T

T

E

R

13 A20 W

13 A

20 W

13 A

20 W

T1

T2

T1

T2

T1

T2

10 W

10 W

W

IL

K

I

N

S

O

N

C

OM

B

I

N

E

R

3dBCombiner

Front panel

sample

600 W

600 W

600 W

1600 W O/P

3dB Divider

PA PCB AGC VSWR

Combiner PCBDC Biasing & Distribution Board

3.4 V biasingDrain 50 V

Over Drive

Protection

Over Current

Protection

VSWR

Protection

Safety Interface Board

Preamp board

CONSTANT IMPEDENCE BAND



CONSTANT IMPEDENCE BAND

PASS DIPLEXER

OPF

STUB +2fs

- 2fs- fs

H2

BPF1

BPF2H1

A in

E

(4))

(3)

(2)(1)

R

A

B(3') (4')

(1'))

(2')

HF

Output

V in

CIBD

ea

(VP-P)

ev(VP-P)

ea

√2∠

0

o

ea

√2∠-90

o ∠-90oev

√2

ev

√2∠0

o

ev

ev & ea



TRANSMITTING TOWER

UPPER BAY

1 to 12

2 to 24

L Meter

L + λ/4 Meter

Matchers for

Fine Tuning

Matchers for

Fine Tuning

12 Branch

Feeder Cables

LOWER BAY

1 to 12

2 to 24

L Meter

L + λ/4 Meter

Matchers for

Fine Tuning

Matchers for

Fine Tuning

12 Branch

Feeder Cables



TV Demodulator (TVDM) is a precision monitoring

equipment for checking the quality of a TV

Transmitter in the VHF and UHF bands. It is similar to a precision TV receiver in many respects. The

function of the TVDM is to recover the picture and

sound signals from the carrier output.

TV DEMODULATORS



TV DEMODULATOR BLOACK

DIAGRAM

PSU

+12V

-12V

-55V

230V

AC

Local Osc

Filter

RF IN

Mixer

IF IN

Inter Carrier Processing

SoundDiscriminator

LS

AF Out

DEV

VideoOutputNyquist Filter

AMP

AGC AMP

ENVDetector

SynchronousDet ector

Gating Pulse

Processor

VID AMP

Zero Ref Pulse

Processor



SAMPLING AND QUANTIZATION

terrestrial broadcasting 1

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