This document discusses earth stations, which transmit and receive signals to and from satellites using dish-shaped antennas. It describes the key components of both analog and digital earth station setups. Analog setups transmit one program per channel and require high power, while digital setups can transmit many more programs using compression and more efficient modulation schemes. The components of a digital earth station include encoders, multiplexers, modulators, up/down converters, high power amplifiers, low noise amplifiers, and antennas.

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2.  What is an Earth Station
 Classification
 Typical analog E/S setup
 Typical digital E/S setup
 Problems of analog
 Why digital
 Digital communication setup
 Components
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3.  Any transmitting or receiving system which sends or receives
signals to and from satellite
 Counterpart to the earth station is the “space station”
 Generally use dish-shaped antennas.
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4. Uplink Station Receive Centre
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What is an Earth Station

5.  Analogue Earth Station
 Analog / Digital Simulcast
 Digital Earth Station
 ASNG
 DSNG
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W/G
A1-A2
A1-A2
Sound Mod
combiner
IF Mod UP converter HPAVideo
Sound Mod
combiner
IF Mod UP converter HPAVideo
DUMMY
LOAD
(Baseband V:0-5MHz, A:5.5/5.75MHZ)
(Baseband V:0-5MHz, A:5.5/5.75MHZ)
70MHz
70MHz
Channel freq. 2
Channel freq. 1
U/L PDA

7. ES PDA
Base band
Processing
Base band
Processing
Enc. 1
Enc. 2
Base band
Processing
Enc. R
MUX 1
MUXR
Modulator#
1
Modulator#
R U/C-R
U/C 1 HPA 1
HPA R
V
V
A
V
A
V
A
V
A
A
V
A
R
O
U
T
E
R
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8.  One program per channel / transponder
 Comparatively noisy
 Required huge power for qualitative transmission
 Ghosts in Terrestrial Transmission
 Uneconomical
 Fixed reception
 Lower Quality with respect to VCD, DVD or Digital Media
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9.  More programs per channel / Transponder i.e. spectrum efficient
10 to 14 TV channels per 36 MHz Transponder
( DVB-S, MPEG 2 )
25 to 50 TV channels per 36 MHz Transponder
( DVB-S2, MPEG 4 / WM 9)
 Economical
 Provision of Encryption
 Reduced uplink power
 Ghost elimination
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10. Channel encoding:
Introduce controlled
redundancy
ARQ, FEC
Source encoding Channel encoding
User Source decoding Channel decoding
Transmission channel
RF Stage
Digital source Mod.
Detector
Source encoding:
Remove redundancy
Base Band
Signal
Compression & IF
stage
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11.  Analog signal is sampled at 27 MHz, encoded into 10 bits PCM - Total bit
rate : 270 Mbps.
 The Y (luminance), Cr (R-Y) and Cb (B-Y) signals are used for
Digitalization.
 The digital standard is known as Serial Digital Interface (SDI)
 Audio signal (AES/EBU) either separate or it may be in embedded with
Video signal.
Digital Base Band signals

12. Need for Compression
Sampling rate for analog video signal
Sampling Frequency for Y-signal 13.5 MHz
Sampling Frequency for CB-signal
Sampling Frequency for CR-signal
6.75 MHz
6.75 MHz
Bit rate for a digital video signal
with 10-bit quantization resolution
13.5 *10 =135 Mbps
6.75 *10 =67.5 Mbps
6.75 *10 =67.5 Mbps
270 MbpsTotal
Video Bit Rate
44.1 kHz
(32/44.1/48 kHz)
2*16*44.1= 1.41 Mbps
Bit rate of digital audio signal with 16-bit
quantization resolution
Sampling Frequency for
audio signal
Audio Bit Rate
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13. Bandwidth requirement for a
given data rate m
R
RB b
s
)1(
)1(




B is bandwidth required
α is Roll-off factor of
pulse shaping filter
Typically ranges 0.28-0.35
RS Symbol rate
Rb Bit rate
m an integer depends on the types of
digital modulation
For
BPSK, m=1
QPSK, m=2
8PSK, m=3
16PSK, m=4
and so on

14. Why Compression ?
To reduce very high bit rate of digital audio and video signals to manageable low
bit rate for various applications. (Saving bandwidth)
What is Compression ?
Removal of redundancy in audio and video signals to achieve very low bit rates
with a little degradation in audio/video quality.
Digital Video at 270 Mbps in SDI format is re-constructed to 1.5 to 15 MBPS
(variable) & digital audio to128 Kbps for CD quality audio (MUSICAM coding)
for transmission.

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ENCODER n
ENCODER 2
ENCODER 1
MUX
CHANNEL
CONTROLLER
SDI 2
SDI 1
SDI n
ASI
ASI out
Sharing of more than one program in single frequency slot in time domain
(MCPC)

16. The process to convert data in a form to transmit through a lossless network, it
includes:
1. Inner coding :FEC (forward error correction) convolution coding (Addition
of one repetitive extra bit after some elementary bit)
2. Outer coding :RS (REED- SOLOMON) coding (188 to 204 bytes)
-Can correct up to 8 lost symbols
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17. • Delivers the Video, Audio and other data in
terms of PES, and other types of data , over
media with errors
• Packets of 204 byte :
• 184 net bytes payload
• 4 bytes header
(+ optional adaptation field)
• 16 bytes Reed – Solomon Parity FECc
Header Bytes
Net Payload
16 4 184
Parity FEC bytes
(RS)
Gross Payload
204
MPEG2
PES: Packetized Elementary Stream
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18.  PDA (Parabolic Dish Antenna)
 LNA / LNBC
 HPA (TWTA, SSPA, Klystrons)
 Up converter
 Modulator
 IRD (Integrated Receiver Decoder)
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19.  Paraboloid antenna with a focal point feed
- Reflector –parabolic
- Feed – phase centre at focal point of reflector
- OMT – three port n/w
 Cassegrain antenna
- Dual reflectors – main reflector and sub reflector
- Feed- phase centre at focal point of sub reflector
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20.  Prime Focus
 Cassegrain
 Off set
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22.  Why Offset?
 Avoid blockage/ LNBF shadow: Low gain
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OPTICAL RECEIVER
AUDI O PROCESSOR
AUDI O
PROCESSOR
VIDEO PROCESSOR
VIDEO PROCESSOR
ROUTER
ENCODER R
ENCODER 2
ENCODER 1
MUX R
MUX 1
ROUTER
PROTECTION
SWITCH
MODULATOR 1
MODULATOR R
UP CONVERTER R
UP CONVERTER 1
W/G
SWITCH
RF SWITCH
TWTA 1
TWTA R
DUMMY
TRANSMITTING
PDA
CHANNEL
CONTROLLER
UPCONVERTER
SWITCH
TO MODULATORS
FROMMUX
FROM
STUDIO
RF MONITORING &
CONTROL

25.  Modulate the final signal to 70 MHz Intermediate frequency
 Mode of modulation :QPSK
 Most commonly used modulation scheme in Digital Satellite
communications.
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26.  Accepts modulated IF carrier and converts into RF signal
 IF signal is mixed with local oscillator frequency and passed
through a band pass filter.
 May be single conversion process or with a dual – conversion
process
 Signal is then fed to HPA and then to dish antenna.
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27.  For receiving, the LNA boosts the signals to the down
converter, which lowers the frequency and sends it to the modem.
The modem demodulates the carrier, and the digital output goes to
the demultiplexing device and then to its destinations.
 Like up conversion it can be with a single conversion process or
dual-conversion process.
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28.  Commonly used are :
 Parametric amplifiers:
-Employed since inception of satellite
 GaAs FET amplifier:
- Gate length - 0.5 micro meter
- Very low noise temp.
- Stable , reliable , low cost
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29.  Used for the final power amplification of the digital RF
signal in C-band/Ku band that is fed to the antenna.
 The important parameters of HPAs are:
• Frequency range
• Output power at flange
• Bandwidth
• Gain variation (1.0db (max.) for 40MHz (narrow band)
• 2.50db for full bandwidth.
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