chapter 5 satellite
TRANSCRIPT
Chapter 5
1
Introduction
2
Satellite Communication Systems
3
Basic operation of a communication satellite
between two earth stations
4
Satellite System Links
5
Satellite Transponder
6
Satellite Frequency Bands
7
Satellite Bandwidth
8
• Bandwidth of the satellite will determine the number of signals that can be transmitted • Wider bandwidth can allow many signals to be carried at a time • C-band has different frequencies for uplink≈ 500 MHz • Each transponder is assigned a bandwidth, eg : MEASAT-1 has a bandwidth of 36 MHz for each transponder (total of 12 transponders) • There are 4 MHz guard bands between channels that are used to minimize adjacent channel interference
Increasing Channel Capacity
9
• There is not enough spectrum space for satellite to use all the transponders unless some form of frequency reuse is employed • This method determined that half of the transponders use vertical polarization and another half uses horizontal polarization, with overlapping frequencies
Satellite Orbits
10
Satellite Orbits
11
Satellite Orbits – Orbital Path
12
• There are an infinite number of orbital paths, but only three are useful for communication satellite • Three paths that a satellite can follow as it rotates around the Earth : inclined, equatorial or polar
Polar Orbit
13
Equatorial Orbit
14
Inclined Orbit
15
Antenna Tracking and Adjustment
16
Azimuth Angle
17
Elevation Angle
18
Earth Station
19
Types of Satellites
Geostationary satellites - located 22,236
miles or 35,786 km from earth at the
geosynchronous orbit
Low Orbital Satellites (LEO) located 300 to
1500 km above earth
Medium Orbital Satellites (MEO) located
8000 to 20000 km from earth
20
Application of Geostationary Satellites
21