This document discusses satellite communications, including a brief history and overview of key concepts. It describes how satellites are used to transmit radio signals for telecommunications by redirecting electromagnetic waves that are obstructed by the curvature of the Earth. The document outlines different types of satellite orbits and antenna designs used for communication. It notes advantages like providing connectivity over long distances uniformly, and disadvantages such as high costs and signal propagation delays.

2.  INTRODUCTION
 HISTORY
 EARTH STATION
 PDA
 TYPES OF PDA
 SATELLITE ORBIT
 ADVANTAGES
 DISADVANTAGES
 CONCLUSION

3. A communications satellite is an artificial satellite that relays
and amplifies through the use of a transponder, radio
telecommunications signals, between a source and a receiver.
Communications satellites are used for television, telephone,
radio, internet, and military applications. There are over
2,000 communications satellites in Earth’s orbit, used by
both private and government organizations. Wireless
communication uses electromagnetic waves to carry signals.
These waves require line-of-sight, and are thus obstructed by
the curvature of the Earth. In order to communicate over
great distances, satellites are used to redirect the signal.

4.  In Wireless World in 1945, Arthur C. Clarke foresaw that it would be
possible to provide complete coverage of World from just three satellites,
they could be placed at Geostationary orbit ie at an 35799 km above the
equator
 In 1960 USA launched two satellite Echo – I & Echo – II from cape
canaveral. These Satellite were Passive Satellite, could only reflect the
signal mechanically and could not receive, amplify,or change the
frequency before re-transmission.
 Afterwards Three INTELSAT SATELLITES are launched and used
for World wide Transmission. These Satellites are situated at 120 degree
apart from each other to cover entire World. Located at Pacific Ocean,
Atlantic Ocean, and Indian Ocean

5. •
EARTH STATION
Uplink
Downlink
Satellite
EARTH
STATIO
N
RECEI
VER

7. 1) Cassegrain (Feed at axis with Sub
reflector).
2) Gregorian (Feed at Prime focus).
3) Offset Fed (Feed away from axis)
4) Monopod

8. MICROWAVE DISHES SATELLITE TELEVISION
DISH
CASSEGRAIN SATELLITE
COMMUNICATION ANTENNA
GREGORIAN ANTENNA

9. ••
POLAR
GEOSYNCHRONOUS
ORBIT
INCLINED
ORBIT
NORTH
POLE
SOUTH
POLE

10.  THE ONLY MEANS TO PROVIDE MULTI ACCESS TWO
WAY COMMUNICATION
 THE COST OF TRANSMITTING INFORMATION
THROUGH SATELLITE IS INDEPENDENT OF DISTANCE
INVOLVED.
 SATELLITE CAN PROVIDE SIGNAL TO TERRESTRIAL
UNCOVERED POCKETS / AREA LIKE VALLEYS AND
MOUNTAINOUS REGIONS.
 SATELLITE CAN PROVIDE UNIFORM SIGNALS FOR
URBAN AND RURAL AREAS.

11. 1. VERY COSTLY
2. PROPAGATION DELAY
3. NOISE & INTERFERENCE

12. The primary mission of the panel was to review the field of
satellite communications technology and systems on a global
basis with a primary focus on Europe, Japan, Russia, and the
United States. It was not an explicit mission of the panel to
review the current and projected future markets for satellite
communications on a global basis. However, such an important
area could not be simply ignored. This section attempts to place
the results of the panel's global review of satellite
communications into a perspective of emerging global markets
over the next decade.