Satellite communication

1. Presentation on
Satellite Communication
By
Vaibhav Kumar
Assistant Professor
Department of
Electronics & Communication
Tula’s Institute

2. CONTENTS :
What’s mean by satellite ?
History of Satellites :
Generalized communication system :
What are the components of a satellite?
 How Satellites Work ?
 How do satellite stay in orbit ?
Why satellite are launched 36,000 Km from centre of earth ?
Types of bands :
Types of orbits :
Advantages And Disadvantages Of satellite :
Uses of satellite :

3. what’s mean by sATELLITE ?
Passive Satellites Active satellites
I. Natural satellites
II. artificial satellites.
 A passive satellite only
reflects received signals back
to earth.
 Ex.moon is a natural satellite
of earth
 Active satellites are
complicated structures
having a processing
equipment called
Transponder .
 An active satellite acts as a
REPEATER
A Satellite is a solid object which revolves around some
body due to the effect of gravitational forces OR
a satellite is an object which has been placed into
orbit by human endeavour.

4. History of Satellites :
 First satellite that was used
for communication
purpose in INDIA was
-ARYABHATTA (19 April
1975)
 The first geostationary
communication satellite
-SYNCOM 3(19 Aug 1963).
The world's first artificial satellite is the Sputnik 1
was launched in 1957

5. INFORM
ATION
SOURCE
Uses
of
infor
matio
n
TRAN
NSMI
TTER
Recei
verChannel
1 2 3 4
1= Message signal.
2 = tranmitted signal.
3 = received signal.
4 = message signal.
Generalized communication system :
NOISE OCCUR

6. What are the components of a satellite?
 Many satellites are
powered by
rechargeable
batteries.
 Small thrusters
provide attitude i.e.
stabilize the satellite's
position in space.

7. How Satellites Work :
I. A Earth Station
sends message in
GHz range (Uplink).
II. Satellite Receive and
retransmit signals
back. (Downlink)
III. Difference between
Downlink and
Uplink frequency is
2 GHz.

8.  1.Gravitational force=
attraction between any
two objects
 2.Centrifugal force=an
outward-directed
force that normally
balances the inward-
directed centripital
forceThere are two relevant
forces involved in this
problem
Why geostationary satellite are launched 36,000 km from thecenter of
the earth?

9. How do satellites stay in orbit?
Satellites stay in orbit
due to the balance of
two factors:
i. Velocity and
ii. Gravitational pull between
the Earth and the satellite.
 Satellites never fall into
the Earth this because Earth
is round and curves.

10. Satellite Frequency Bands :
 There is a inverse
relationship between
frequency and wavelength.
 Different kinds of satellites
use different frequency
bands.
 L–Band: 1 to 2 GHz,
 S-Band: 2 to 4 GHz
 C-Band: 4 to 8 GHz
 X-Band: 8 to 13 GHz
 Ku-Band: 13 to 18 GHz
 K-Band: 18 to 28 GHz
 Ka-Band: 28 to 40 GHz
As wavelength
increases (and
frequency decreases),
larger antennas
(satellite dishes) are
necessary to gather
the signal.

11. C-band :
 C-band is the most
common frequency
spectrums used by
today’s satellite.
 C-band satellite
transmissions occupy
the 4 to 8 GHz
frequency range.
 C-band antenna is
approximately 2-3
meters in diameter

12. Ku-band:  Ku-band satellite
transmissions occupy the 13 to
18 GHz frequency range.
 Ku-band antennas can be as
small as 18 inches in diameter
 These very high frequency
transmissions mean very small
wavelengths and very small
diameter receiving antennas.

13. TYPES OF ORBITS
Low-Earth-Orbit (LEOs)
Medium-Earth-Orbit (MEOs)
Geostationary (GEOs)

14. Low-Earth-Orbit (LEO)
Altitude (600-1000 KM)
 satellite gives it a better
signal strength
Advantages:
Reduces transmission
delay
Disadvantages:
Smaller coverage area.
Shorter life span (5-8
yrs.)

15. Little LEOs Applications
 0.8 GHz range
 Small, low-cost
 Used for short
communications.

16. Middle-Earth-Orbiting (MEO)
MEOs orbits between the
altitudes of 8,000 - 20,000 km
above the earth.
MEO satellites have a larger
coverage.
These orbits are primarily
reserved for communications
satellites that cover the North and
South Pole.
 MEOs are placed in an elliptical (oval-shaped)
orbit.

17. Geosynchronous-Earth-Orbit (GEO)
 From the ground level
the satellite appears
fixed.
 GEO satellites have a 24
hour view of a particular
area.
 Coverage to 40% of area
Of planet by this
satellite

18. ADVANTAGES AND DISADVANTAGES OF SATELLITE:
ADVANTAGES : DISADVANTAGES :
 Make repeated
observations over a given
area .
 At a time satellites observe a
larger coverage area.
 Minimum Satellite lifetime
is about 10-15 years.
 Poor spatial resolution
in the polar regions.
 Launching satellites
into orbit is costly.

19. Uses of satellite:
 IT IS USED FOR LONG DISTANCE COMMUNICATION.
 IT IS SPEEDY AND RELIABLE.
 IT IS USED FOR WEATHER FORECASTING.
(study of atmosphere ,rain ,sunshine at any place at
perticular time)
 IT IS USED FOR TRANSMIT T.V. SIGNAL OVER LARGE
DISTANCE COMMUNICATION.
 POLAR SATELLITE IS USED FOR REMOTE SENSING.