Satellite Microwave

Satellite Microwave

Physical Description A communication satellite is, in effect, a microwave relay
station. It is used to link two or more ground-based microwave transmitter/receivers,
known as earth stations, or ground stations. The satellite receives transmissions on
one frequency band (uplink), amplifies or repeats the signal, and transmits it on
another frequency (downlink). A single orbiting satellite will operate on a number of
frequency bands, called transponder channels, or simply transponders.
Applications The communication satellite is a technological revolution as important
as fiber optics. The following are among the most important applications for satellites:
• Television distribution
• Long-distance telephone transmission
• Private business networks
Because of their broadcast nature, satellites are well suited to television distribution
and are being used extensively in the United States and throughout the world for
this purpose. In its traditional use, a network provides programming from a centrallocation.
Programs are transmitted to the satellite and then broadcast down to a number of
stations, which then distribute the programs to individual viewers. One network, the
Public Broadcasting Service (PBS), distributes its television programming almost exclusively
by the use of satellite channels. Other commercial networks also make substantial
use of satellite, and cable television systems are receiving an ever-increasing proportion
of their programming from satellites.The most recent application of satellite technology
to television distribution is direct broadcast satellite (DBS), in which satellite video signals
are transmitted directly to the home user. The dropping cost and size of receiving
antennas have made DBS economically feasible, and DBS is now commonplace.
Satellite transmission is also used for point-to-point trunks between telephone
exchange offices in public telephone networks. It is the optimum medium for
high-usage international trunks and is competitive with terrestrial systems for many
long-distance intranational links.
Finally, there are a number of business data applications for satellite.The satellite
provider can divide the total capacity into a number of channels and lease these
channels to individual business users. A user equipped with antennas at a number of

sites can use a satellite channel for a private network. Traditionally, such applications
have been quite expensive and limited to larger organizations with high-volume
requirements.