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Satellite Communication

K.M.PrabusankarlalDepartment of Electronics &

Communication

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Electronic Communication

Sending Receiving and Processing information through electronic system

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Electromagnetic Spectrum

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Communication System

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Modulation and Demodulation

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Olden days Systems

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The Radio Experiment

1897, Marconi sent the first ever wireless communication over open sea. The experiment, witnessed a message transversed over the Bristol Channel a distance of 6 kms. The message read "Are you ready"

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Transatlantic transmissions

12 December 1901, using a 152.4-metre (500 ft) kite-supported antenna for reception, the message was received at Signal Hill in St John's, Newfoundland (now part of Canada) signals transmitted by the company's new high-power station at Poldhu, Cornwall. The distance between the two points was about 3,500 kilometres

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Wave Propagation

Ground Wave Sky Wave Space Wave

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Sky Wave Propagation

Radio waves radiated at a high angle and reflected by these layers return to earth at a distance from the transmitter.

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How does a satellite orbit?

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Orbit Types

There are three major orbits: geosynchronous orbit (GEO), middle earth orbit (MEO), and low earth orbit (LEO). The majority of communications satelites in use are GEOs.

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Low Earth Orbit (LEO) LEO satellites are much closer to the earth

than GEO satellites, ranging from 500 to 1,500 km above the surface.

LEO satellites don’t stay in fixed position relative to the surface, and are only visible for 15 to 20 minutes each pass.

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Low Earth Orbit (LEO)

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Medium Earth Orbit (MEO) A MEO satellite is in orbit somewhere between

8,000 km and 18,000 km above the earth’s surface.

MEO satellites are similar to LEO satellites in functionality.

MEO satellites are visible for much longer periods of time than LEO satellites, usually between 2 to 8 hours.

MEO satellites have a larger coverage area than LEO satellites.

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Iridium of Motorola

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Iridium of Motorola

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Geostationary Earth Orbit (GEO)

These satellites are in orbit 35,863 km above the earth’s surface along the equator.

Objects in Geostationary orbit revolve around the earth at the same speed as the earth rotates. This means GEO satellites remain in the same position relative to the surface of earth.

• A GEO satellite’s distance from earth gives it a large coverage area, almost a fourth of the earth’s surface.

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Geostationary Earth Orbit (GEO)

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Artificial Satellites

The Soviet Union launched Sputnik 1 on Oct. 4, 1957. The world’s first artificial satellite

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Artificial Satellites

Sputnik-2 equipped with a rudimentary life support system to keep its passenger, a dog named Laika

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India’s First Satellite

Aryabhatta April 19, 1975 , Soviet Intercosmos rocket

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How do Satellites Work

Two Stations on Earth want to communicate through radio broadcast but are too far away to use conventional means.

The two stations can use a satellite as a relay station for their communication

One Earth Station sends a transmission to the satellite. This is called a Uplink.

The satellite Transponder converts the signal and sends it down to the second earth station. This is called a Downlink.

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GEO Communication Satellites

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Sections of a Satellite

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Satellite Frequency bands

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Launching Vehicles

PSLV GSLV

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Satellite Debris