Satellite Communications lecture - Satellite Communications...

Satellite Communications
Satellite Communications
Definitions:
Satellite
Is a celestial body that orbits around a planet (e.g., the moon is the earth satellite )
Satellite Communications
Is a microwave repeater in the sky that consist of a diverse combination of one or more of the following: receiver, transmitter, amplifier, regenerator,
filter, onboard computer, multiplexer, demultiplexer, antenna and other electronic communication circuits.
Transponder
It’s a satellite repeater, sometimes this term also used to specify the circuit capacity of the satellite.
1 Transponder is equal to 36 MHz Bandwidth
Satellite System
Is a system consisting of one or more satellite space vehicles, ground-based station to control the operation of the system, and a user network of
earth stations that provides the interface facilities for transmission and reception of terrestrial communication traffic through the satellite system.
Satellite Orbit
Inclined Orbit
Are virtually all orbits except those travel directly above the equator or directly over the North and South Poles.
Equatorial Orbit
When the satellite rotates in an orbit directly above the equator, usually in a circular path. It has an angle of inclination of 0º.
Polar Orbit
When the satellite rotates in a path that takes it over the North and South Poles in an orbit perpendicular to the equatorial plane. It has an angle of
inclination of 90º.
Types of Satellite
LEO ( Low Earth Orbit )
It’s a low orbiting satellite approximately 480 miles above the earth’s surface.
MEO ( Medium Earth Orbit )
Satellite with an altitude between 5000 km to 15,000 km
GEO ( Geosynchronous Earth Orbit )
Are high-latitude earth –orbit satellite with an altitude of 35,786 km

Satellite Communications
Satellite Orbital Patterns
Apogee
The point in an orbit that is located farthest from Earth.
Perigee
The point in an orbit that is located closest to Earth.
Major Axis
The line joining the perigee and apogee through the center of Earth: sometimes called line of apsides
Minor Axis
The line perpendicular to the major axis and halfway between the perigee and apogee ( Half the distance of the minor axis is called the semi-minor
axis.)
Kepler’s Law
A satellite remains in orbit because the centrifugal force caused by its rotation around earth is counterbalanced by earth’s gravitational pull.
First Law
The orbit of a planet around the sun is an ellipse.
Second Law
A straight line from the planet to the center of the sun sweeps out equal areas in equal time intervals as if goes around the orbit; the planet moves
faster when closer to the sun and slower when distant.
Third Law
The square of the period ( in years ) for one revolution about the sun equals the cube of the mean distance from the sun center, measured in an
astronomical units.