The document provides an overview of satellite communication systems. It discusses key topics such as: 1. How satellite communication works by transmitting signals between Earth-based stations and satellites. 2. The components involved including the uplink from Earth to satellite and downlink from satellite to Earth. 3. Technical aspects like frequency bands, conversions, and satellite positioning in geostationary orbit. 4. Applications of satellite communication including broadcasting, internet access, and GPS navigation.

1. Satellite Communication System
Overview
Satellite
Communication
System
Overview
DIPAK KUMAR JHA
ECE(4th Year)

2. Through lecture, presentation and visual display each learner
will be able to understand and explain how Satellite
Communication operates overall and within a network.
• Objectives:
1. The learner will be able to identify basic terminology
associated with any Satellite
Communications operation scheme.
2. The learner will be able to identify and explain the typical
satellite link to include
components, carriers, conversion values and locations.
3. The learner will be able to describe the different
frequency bands and frequency
conversion utilized within a basic satellite network.
4. The learner will be able to get hold of advantages and
disadvantages of Satellite Communications.
5. The learner will be able to analyze different applications of
Satellite.

3. • In satellite communication, signal
transferring between the sender and
receiver is done with the help of
satellite. In this process, the signal
which is basically a beam of modulated
microwaves is sent towards the satellite.
Then the satellite amplifies the signal
and sent it back to the receiver’s
antenna present on the earth’s surface.
So, all the signal transferring is
happening in space. Thus this type of
communication is also known as space
communication.
• The conventional way to call the process
of transmitting the modulated signal
from HUB teleport to Satellite is the
“Uplink” whereas from the satellite
down to a remote station is “Downlink”.

4. 1. Satellite act as a repeater placed
in space.
2. Satellite have communication
payloads known as Transponders.
These Transponder operates in
fixed freq. band(C,Ku,Ka band) and
with fixed polarization i.e.
Vertical/Horizontal
3. Satellite is located in fix slot
(allocated by ITU) in Geostationary
Orbit , which is 36000 KM above
the Equator of the Earth.
4. Satellite received the signal
(uplink freq band)from Trans.Earth
station, convert the signal into
down link freq band, amplified and
transmit back to the Earth.

5. • Frequency Band
• L 1-2 GHz
• S 2-4 GHz
• C 4-8 GHz D/L 3.7 to 4.2 U/L 5.925-6.425
• X 8-12 GHz
• Ku 12-18 GHz D/L 11.7-12.2 U/L 14-14.5
• Ka 27-40 GHz D/L 17.7-21.2 U/L 27.5-30

9. Earth Orbits for Satellite
Communication Services
• Orbit Definition Altitude Range
(km) Period (Hours) (above
surface of the earth),Orbital
speed(Km/s)
• LEO 150 to 1,000 KM ,1.5 to 1.8
Hrs,7.13Km/s
• MEO 5,000 to 10,000 KM,3.5 to 6
Hrs,4.89Km/s
• Geosynchronous 36,000 KM 24
Hrs,3.07Km/s.Geo stationary
Satellite: Precisely 35,786 km in the
plane of the equator. Mean earth
radius is 6378.137 Km & GEO
radius from the centre of earth is
42164.17Km

10. Geosynchronous Earth Orbit

12. Geostationary Orbit
• To be perfectly geostationary, the
orbit of a satellite needs to have
three features : (a) it must be
exactly circular(i.e. have an
eccentricity of zero), (b) it must be
at the correct altitude (i.e. have the
correct period),(c) it must be in the
plan of equator(i.e. have a zero
inclination with respect to the
equator).
Geosynchronous Orbit
• If the inclination of the satellite is
not zero and/or if the eccentricity is
not zero, but the orbital period is
correct, then the satellite will be in
a geosynchronous orbit . The
orbital period of geo satellite, 23h
56m 4.1s is one sidereal day. A
sidereal day is the time between
consecutive crossing of any
particular longitude on the earth by
any star, other than the sun.
Geostationary Orbit Vs Geosynchronous Orbit

14. CC
E
A
D
EE
D
B
Downlink – Uplink
C
B
430 kHz
Downlink
A
User A
User D
User CUser B
User E
Hub/Teleport Location
14000 14500
36 MHz 36 MHz36 MHz36 MHz36 MHz36 MHz
14122 14158
14123.530
Uplink
Downlink
Upstream Carrier
Multiple UpstreamsMultiple UpstreamsMultiple Upstreams

16. Frequency Translation

17. • Conversion Calculations (Ku-Band):
1325.750MHz L-Band HUB Teleport TX
+ 12,800.000MHz Up Converter Local Oscillator (L/O)
14,125.75MHz Ku-Band Uplink RF
------------------------------------------------------------------------
- 2300.000MHz Sat Xponder L/O (typical)
------------------------------------------------------------------------
11,825.750MHz Ku-Band Downlink RF
- 10750.000MHz LNB L/O
1075.75MHz calc’d L-Band Remote terminal RX
Frequency Calculations

19. A
TIMING: Time Division Multiple Access.
C
430 kHz
E
D
B
User A
User D
User CUser B
User E
Hub/Teleport Location
14000 14500
36 MHz 36 MHz36 MHz36 MHz36 MHz36 MHz
14122 14158
14123.530
Uplink
Downlink
HUB Teleport shall be intelligent to handle timings
At T1 time only Remote C shall Xmit.
At T2 time only Remote A shall Xmit.
At T3 time only Remote B shall Xmit.
……….
……….
A
DD
A BBB
EEE
A
DD
A
E
D
BBA

20. Modulation
BPSK QPSK 8PSK
16PSK

21. • Axial or front feed This is the most common type,
with the feed antenna suspended in front of the dish
on the beam axis, at the focal point, pointed back
toward the dish. One drawback of this type is that the
feed and its supports partially block the beam.
• Off-axis feed or offset-feed The primary reflector is
asymmetric, with the focus, and the feed, located to
one side, outside the beam area. This avoids the
problem of the feed obstructing the beam. It is used
in home satellite dishes.
• Cassegrain In this design, the feed is located on or
behind the dish, and its beam illuminates a small
hyperboloidal secondary reflector convex at the focus
of the dish, which reflects the beam back to the
parabolic dish. It is used in antennas with bulky or
complicated feeds, such as satellite ground antennas
and radio telescopes.
• Gregorian This is similar to the Cassegrain, except the
secondary reflector has a concave ellipsoidal shape.

24. Advantages of SAT.COM
• The satellite communication is very
helpful for the people staying in
remote areas
The satellite communication services
are very much helpful during the
time of natural disasters as the wired
services have large chances of failing
.
• Satellite communication services
include the services like voice calling,
video calling, radio, television
channels, internet, fax, etc
Satellite communication services
being so portable are very easy to
install and user-friendly as well.
• Satellite is also used for
broadcasting purpose.

27. Disadvantages of SAT.COM
• * Signal delay: Because the
satellite is 36,000km from
the earth there is an
appreciable delay
* Cost: Satellites are large
and expensive, thus there
is a large capital cost in
building and launching a
satellite
* Impossibility to repair
and maintain

28. 1. Essentially Satellite link is capable to handle any kind of
traffic. Be it TCP, UDP, Video, Multicast so on and so forth.
Example: Imagine yourself in a remote area typing
www.yahoo.com on your laptop. Your yahoo.com request
reaches the remote terminal Satellite  HUB Teleport 
yahoo.com server and reply back to HUB Teleport  Satellite
 Remote Terminal  to your computer where you see the
yahoo.com page.
Satellite communication Applications

29. Satellite communication Applications
2. Imagine yourself flying from India to USA. How will you feel
when the Air Hostess lets you know you will be connected to
internet and hence to the world through out your flight for
16 hours? Is it possible?

31. Altitude: 10,900 nautical miles (26561
km semi-major)
Orbital Period: 12 hours
Orbital Plane: 55o to equatorial plane
Six Orbital Planes
3.87km/s
24 satellites
Global
Positioning
System
(GPS)
GPS Constellation
Planned Lifespan: 7.5 years
Weight: 1900 lbs (in orbit)
Size: 17 ft with solar panels
The current GPS constellation consists
of
32 Block II/IIA/IIR/IIR-M
satellites.

32. BSNL
Connecting India