Matakuliah : H0122 / Dasar Telekomunikasi
Tahun
: 2008
Sistem Komunikasi Satelit
Pertemuan 9
Learning Outcomes
Mahasiswa dapat mendemonstrasikan kelebihan dan
kerugian sistem satelit serta aplikasi satelit untuk
navigasi.
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Outline Materi
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Pengertian sistem satelit
Komponen Sistem
Orbit Satelit
Aplikasi Sistem Komunikasi Satelit
GPS
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Satellite Systems
Inter Satellite Link (ISL)
Mobile User Link
(MUL)
Gateway Link
(GWL)
MUL
GWL
small cells
(spotbeams)
base station
or gateway
footprint
Data Network
PSTN: Public Switched
Telephone Network
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PSTN
GSM
User data
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Satellite Communication
• Satellites are launched and orbited for a variety of purposes but the
most common application is communication.
• Two Stations on Earth want to communicate but are too far away to
use conventional means, they can use a satellite as a relay station.
• Communication satellites are not originators of information but are
relay stations for earth sources.
• The transmitting station sends the information to the satellite (uplink),
which in turn retransmits it to the receiving station (downlink).
• The signal converter is called transponder.
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Classification
• Coverage area
• Global, regional, national
• Service type
• Fixed service satellite (FSS)
• Broadcast service satellite (BSS)
• Mobile service satellite (MSS)
• General usage
• Commercial, military, amateur, experimental
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Orbits
• Satellite orbits:
– Equatorial-orbit satellite
– Inclined-orbit satellite
– Polar-orbit satellite
• Footprint
– The signal satellite from a satellite is aimed at a specific area
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Categories
• Satellite categories
– GEO (Geosynchronous Earth Orbit)
– MEO (Medium-Earth Orbit)
– LEO (Low-earth orbit)
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Satellite Orbit Altitudes
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Satellite Communications
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Early satellite communications use C band in the range 3.7-4.2 GHz
Could interfere with terrestrial communications
Beamwidth is narrower with higher frequencies
Recent communications make greater use of Ku band
Ka band is now being used.
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Frequency Bands
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Band designation
Normal frequency range
(GHz)
L
S
C
X
Ku
K
Ka
V
W
millimeter (mm)
1–2
2–4
4–8
8 – 12
12 – 18
18 – 27
27 – 40
40 – 75
75 – 110
100 - 300
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GEO Orbit
• Originally proposed by Arthur C. Clarke.
• Circular orbits above the equator, angular separation about 2
degrees - allows 180 satellites.
• Orbital height above the earth about 36000km.
• Round trip time to satellite about 0.25 seconds.
• Requires more power for communications.
• SNR is worse because of the distances involved
• A few GEOs can cover most of the surface of the earth; polar
regions cannot be “seen” by GEO.
• Since they appear stationary, GEOs do not require tracking.
• GEOs are good for broadcasting to wide areas.
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Satellite Relay Link
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Transponder
• An earth station transmits information to the satellite.
• The satellite contains a receiver that picks up the transmitted
signal, amplifies it, and translates it on another frequency.
• The signal on the new frequency is then retransmitted to the
receiving stations back on earth.
• The transmitter-receiver combination in the satellite is known as a
transponder.
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Ground Stations
• The ground station, or earth station, is the terrestrial base of the
system.
• The ground station communicates with the satellite to carry out the
designated mission.
• The earth station consists of five major subsystems:
 The antenna subsystem
 The receive subsystem
 The transmit subsystem
 The ground control equipment (GCE) subsystem
 Power subsystem
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GPS
• Global Positioning Satellite (GPS)
– Altitude about 18.000 km
– Based on a triangulation principle
– Uses 24 satellite in six orbits
– Use in military forces
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Summary
• Telah dipelajari kategori satelit.
• Telah dipelajari aplikasi satelit komunikasi.
• Telah dipelajari subsistem satelit komunikasi.
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