23-06-2012, 12:51 PM
Satellite Communication
Satellite Communication.ppt (Size: 4.8 MB / Downloads: 144)
Satellite
A satellite is an object that orbits another object (known as its primary). The term is often used to describe an artificial satellite (as opposed to natural satellites, or moons).
Because all objects exert gravity, the motion of the primary object is also affected by the satellite. (This observation allows for the discovery of extra solar planets.) If two objects are sufficiently similar in mass, they are generally referred to as a binary system rather than a primary object and satellite. The general criterion for an object to be a satellite is that the center of mass of the two objects is inside the other object.
All masses that are part of the solar system, including the Earth, are satellites of the Sun, or satellites of those objects, such as the Moon.
Why Use Satellite?
Satellite communication is just one example of wireless communication systems. Familiar examples of wireless systems are all around us, such as radio and television broadcasting and mobile and cordless telephones. These systems rely on a network of ground-based transmitters and receivers and for this reason they are often referred to as "terrestrial" systems.
One major use of satellites familiar to everyone is satellite television broadcasting.
Other applications of satellite communications include high speed internet, telephony and corporate networks for multinational businesses.
Satellite Communication
A communications satellite (sometimes abbreviated to comsat) is an artificial satellite stationed in space for the purposes of telecommunications using radio at microwave frequencies. Most communications satellites use geosynchronous orbits or near-geostationary orbits, although some recent systems use low Earth-orbiting satellites. A place on the ground with satellite dishes used to transmit to or receive from these is called an earth station.
Introduction
In 1962, the American telecommunications giant AT&T launched the world's first true communications satellite, called Telstar. Since then, countless communications satellites have been placed into earth orbit, and the technology being applied to them is forever growing in sophistication.
Selection of the band
The selection of the band is not something that individual service providers decide, but is rather chosen by large satellite operators based on different factors:
Availability: C-band is still the most widely available worldwide. Ku-band is becoming more available recently in regions which were less covered in the past (South America, Asia, Africa)
C-band is more prone to interference from other transmission services that share the same frequencies (adjacent satellites or terrestrial transmissions) than the higher bands
While the C-band technology is cheaper in itself, it requires larger dishes (1 to 3 m) than Ku- and Ka-band (0.6 to 1.8 m) and therefore imposes relatively higher (installation) costs on the end-user .
Types of Satellites
Astronomical satellites are satellites used for observation of distant planets, galaxies, and other outer space objects.
Communications satellites are artificial satellites stationed in space for the purposes of telecommunications using radio at microwave frequencies. Most communications satellites use geosynchronous orbits or near-geostationary orbits, although some recent systems use low Earth-orbiting satellites.
Satellite Communication.ppt (Size: 4.8 MB / Downloads: 144)
Satellite
A satellite is an object that orbits another object (known as its primary). The term is often used to describe an artificial satellite (as opposed to natural satellites, or moons).
Because all objects exert gravity, the motion of the primary object is also affected by the satellite. (This observation allows for the discovery of extra solar planets.) If two objects are sufficiently similar in mass, they are generally referred to as a binary system rather than a primary object and satellite. The general criterion for an object to be a satellite is that the center of mass of the two objects is inside the other object.
All masses that are part of the solar system, including the Earth, are satellites of the Sun, or satellites of those objects, such as the Moon.
Why Use Satellite?
Satellite communication is just one example of wireless communication systems. Familiar examples of wireless systems are all around us, such as radio and television broadcasting and mobile and cordless telephones. These systems rely on a network of ground-based transmitters and receivers and for this reason they are often referred to as "terrestrial" systems.
One major use of satellites familiar to everyone is satellite television broadcasting.
Other applications of satellite communications include high speed internet, telephony and corporate networks for multinational businesses.
Satellite Communication
A communications satellite (sometimes abbreviated to comsat) is an artificial satellite stationed in space for the purposes of telecommunications using radio at microwave frequencies. Most communications satellites use geosynchronous orbits or near-geostationary orbits, although some recent systems use low Earth-orbiting satellites. A place on the ground with satellite dishes used to transmit to or receive from these is called an earth station.
Introduction
In 1962, the American telecommunications giant AT&T launched the world's first true communications satellite, called Telstar. Since then, countless communications satellites have been placed into earth orbit, and the technology being applied to them is forever growing in sophistication.
Selection of the band
The selection of the band is not something that individual service providers decide, but is rather chosen by large satellite operators based on different factors:
Availability: C-band is still the most widely available worldwide. Ku-band is becoming more available recently in regions which were less covered in the past (South America, Asia, Africa)
C-band is more prone to interference from other transmission services that share the same frequencies (adjacent satellites or terrestrial transmissions) than the higher bands
While the C-band technology is cheaper in itself, it requires larger dishes (1 to 3 m) than Ku- and Ka-band (0.6 to 1.8 m) and therefore imposes relatively higher (installation) costs on the end-user .
Types of Satellites
Astronomical satellites are satellites used for observation of distant planets, galaxies, and other outer space objects.
Communications satellites are artificial satellites stationed in space for the purposes of telecommunications using radio at microwave frequencies. Most communications satellites use geosynchronous orbits or near-geostationary orbits, although some recent systems use low Earth-orbiting satellites.