Basic Satellite Communication Thaicom Customer and Network Services Department
Satellite Communication System Control & Monitoring Station Satellite Space Segment Uplink Signals Downlink Signals Receive Sites Transmit Sites Ground Segment
Satellite Communication Satellite amplifies the uplink signal from earth and beams back to earth Advantages : - Easy installation :: stand alone terminals, suitable for remote areas - Wide area coverage :: one-third of globe, suitable for broadcast applications Disadvantages: - Open System:: prone to interferences, security issues data encryption - Unavoidable natural phenomena like sun outage
Basic Satellite Configuration 1V Ku: 14GHz C: 6GHz LNA Down Converter I M U X 2V 12V O M U X Ku: 12GHz C : 4GHz Receiver Section High Power Amplifiers (Transponders) LNA : Low Noise Amplifier; amplifies the received uplink signal Down Converter: Frequency conversion from uplink to downlink frequency IMUX : Input Multiplexer OMUX : Output Multiplexer HPAs / Transponders : High Power Amplifier, amplifies the downlink signal
Satellite Orbits Types LEO : Low Earth Orbit Altitude : less than 2000 km. Approximately 30-90 minutes orbits around the earth. Applications : Satellite phone MEO : Medium Earth Orbit Altitude : ~8000 12000 km. Approximately 4-8 hours orbits around the earth Applications : High speed data transmission, GPS, etc. GEO : Geosynchronous Orbit Altitude : ~36000 km. 24 hours orbits around the earth (equal to earth orbits around itself). Lie in the equatorial plane. Applications : High Speed Internet, Live TV program, etc.
Thaicom Satellites & Footprints Thaicom-5 78.5 E 120 E ipstar [A] C-Band Global Beam [B] C-Band Regional Beam [C] Ku-Band Thailand Beam [D] Ku-Band Indochina Beam Beam Peak 38dBW Beam Peak 41 dbw Beam Peak 57 dbw Beam Peak 56 dbw (A) Spot Beam (B) Broadcast Beam (C) Shape Beam
Satellite Station Keeping Sun s Gravity Orbital Plane E N Solar Pressure W S Earth s Gravity Moon s Gravity Satellite cannot stay exactly at its orbital slot position due to many forces which are acting on it. Satellite controllers need to maneuver the satellite few times a day/week to keep satellite within the box Center of Box Time is the best time for earth stations to align the antennas (especially the big antennas due to small beam width) Satellite downlink signal level varies with 24 hours cycle
Sun Outage Orbital Plane What is Sun Outage? During the time when both the satellite and the sun are in the earth station's field of view, the energy from the sun can overpower the signal from the satellite. Also known as sun transit or sun fade. Bore Sight Does it affect to satellite services? Yes, sun outage causes total outage to all satellite services since signal is lost in noise. Can it be prevented? No, it is a natural phenomenon and occurs in all satellites What should earth stations do at that time? Sun outage effects the receive path (not transmit). Auto-tracking antennas should be in standby mode to prevent erroneous tracking.
Sun Outage (continue) How Often Does it Happens? How long does it last when occur? There are two sun outage seasons a year. Outage occur for few minutes (depending on antenna size) per day and this happens for few days. Difference location, different time of outage. Smaller Antenna Wider Beamwidth Longer Outage Time Online Sun Outage Prediction Program: http://tcns.thaicom.net/sunoutage.asp
Earth Station Uplink System (examples) Uplink Frequency Ranges for Thaicom-5 Standard C-Band : 5.927-6.403 GHz Extended C-Band : 6.432 6.723 GHz Baseband Signal (Voice, Data, Video, etc) Modem Upconverter HPA IF: 70MHz RF: 6 GHz (C- Band) L-Band Modem BUC L-Band: 0.95-1.45GHz RF: 6 GHz (C- Band)
Earth Station Downlink System (examples) L-Band ** IRD / Modem LNB Baseband Signal (Voice, Data, Video, etc) Modem Down Converter LNA IF Frequency Thaicom 5 Frequency Conversions U/L -2225 MHz=D/L (Std-C Band) U/L -3025 MHz=D/L (Ext-C Band) (conversion depends on satellite LO) RF: 4 GHz ** LNB Frequency Conversions (MHz) 5150-D/L=L-Band (Std-C Band) (GHz) 11.3 D/L=L-Band (Ku-Band) ( conversion depends on LO of LNB )
Thank You