satellite communication

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A
Seminar on INTRODUCTION TO SATELLITE
Presented By

SWAPNIL G. THAWARE
20100764
Under the Guidance of
Prof. HIVRE S. R.
Department Of Information technology
Engineering
Dr. Babasaheb Ambedkar Technological University,
LONERE-402 103
2011-2012
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CONTENTS

• Whats mean by satellite ?
• History of Satellites
• Layer Of Atmosphere
• 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
• Global position system
• Advantages And Disadvantages Of satellite
• Uses of satellite
• References

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whats mean by sATELLITE ?

• 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.

• Active satellites

• Passive Satellites

• Active satellites are complicated structures
  having a processing equipment called Transponder
  .
• An active satellite acts as a REPEATER

• Natural satellites
• artificial satellites.
• A passive satellite only reflects received
  signals back to earth.
• Ex.moon is a natural satellite of earth

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History of Satellites

• The world's first artificial satellite is the
  Sputnik 1
• was launched in 1957

• 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).
• Father of geostationary communication satellite
  is
• -HAROLD ROSEN
• (Aircraft engineer)

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Layer Of Atmosphere

• TROPOSPHERE
• STRATOSPHERE
• MESOSPHERE
• THERMOSPHERE
• EXOSPHERE

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• Generalized communication system

INFORMATION SOURCE
Uses of information
TRANNSMITTER
Receiver
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2
3
1
Channel
NOISE OCCUR

• 1 Message signal.
• 2 tranmitted signal.
• 3 received signal.
• 4 message signal.

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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.

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How Satellites Work

• A Earth Station sends message in GHz range
  (Uplink).
  
  
• Satellite Receive and retransmit signals back.
  (Downlink)
• Difference between Downlink and Uplink frequency
  is
• 2 GHz.

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Why geostationary satellite are launched 36,000
km from the center of the earth? 

• 1.Gravitational force attraction between any
  two objects, given by
• 2.Centrifugal forcean outward-directed force
  that normally balances the inward-directed
  centripital force

• There are two relevant forces involved in this
  problem

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Eqating that 2 eqn
Equate that 2 eqn
We know G 6.67 x 10-11 Nm2kg-2 me 5.97 x
1024 kg we 7.29 x 10-5 rad s-1
i.e.
Hence, substituting the above constants into
gives
As we know
The tangential velocity of the satellite (vs) is
related to its orbital period, T so,
Then T? and sqaring
R 35,786 km for center of earth Near about
36,000 km.
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How do satellites stay in orbit?

•   Satellites never fall into the Earth this
  because Earth is round and curves.

• Satellites stay in orbit due to the balance of
  two factors

• Velocity and
• Gravitational pull between the Earth and the
  satellite.

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Satellite Frequency Bands

• Different kinds of satellites use different
  frequency bands.
• LBand 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

• There is a inverse relationship between
  frequency and wavelength.

• As wavelength increases (and frequency
  decreases), larger antennas (satellite dishes)
  are necessary to gather the signal.

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C-band

• C-band is the most common frequency spectrums
  used by todays satellite.
• C-band satellite transmissions occupy the 4 to 8
  GHz frequency range.
• C-band antenna is approximately 2-3 meters in
  diameter

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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.

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TYPES OF ORBITS

• Low-Earth-Orbit (LEOs)
• Medium-Earth-Orbit (MEOs)
• Geostationary (GEOs)

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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.)

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Little LEOs Applications

• 0.8 GHz range
• Small, low-cost
• Used for short communications.

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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.

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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

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The Global Positioning System

• EQUATORIAL ORBIT
• POLAR CIRCULAR ORBIT
• INCLINED ORBIT

• EACH SATELLITE COVER 40 AREA
• SATELLITE MAKES AN ANGLE OF 120 WITH EACH OTHER.

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ADVANTAGES AND DISADVANTAGES OF SATELLITE

• DISADVANTAGES

• ADVANTAGES

• Make repeated observations over a given area .
• At a time satellites observe a larger coverage
• Minimum Satellite lifetime is about 10-15
  years.  

• Poor spatial resolution in the polar regions.
• Launching satellites into orbit is costly.

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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.

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REFERENCES

• http//en.wikipedia.org/wiki/Geosynchronous_satell
  ie
• Geostationary Satellite(Author- Louis E.Frenzel)
• (Edition- Third)
• (Publication- Tata McGraw-Hill)
• http//web.mit.edu/invent/iow/rosen.html

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-- gtgtBY SWAPNIL G. THAWARE