25-01-2012, 11:50 AM
Satellite Communication Systems
[attachment=16559]
TRANSMITTER CHAIN
Information to be transmitted is delivered
to the earth station via coaxial cable, fiber,
terrestrial microwave, or satellite. The
devices in the transmitter chain typically
consist of the multiplexer, the modulator,
the upconvertor, a high power amplifier,
and the antenna. The multiplexer
combines the individual channels onto a
single data stream. The information can
be encrypted and encoded with a forward
error correction code.
RECEIVER CHAIN
The devices in the receiver chain reverse
this process. The antenna receives the
modulated RF signals from the satellite.
The power level at the output terminals of
the antenna is about a picowatt. This
extremely low power level is comparable
to the sound level from a barely audible
mosquito.
EARTH STATION FACILITIES
A good example of a commercial earth
station facility is the Washington
International Teleport, located in
Alexandria, Virginia just inside the
Washington Capital Beltway. This facility
is a hub for voice, data, video, internet,
and other services to customers ranging
from major television broadcasters to
telemedicine and distance learning
providers.
