1. SATELLITECOMMUNICATIONS byRodel P. Hacla, ECE

2. A satellite is an object put into orbit around the earth orany other planet in order to relay communication signalsor transmit scientific data 3. Kepplers Law -laws concerning the motions of planets formulated by German astronomer Johannes Kepler First Law the orbit of a planet around thesun is ellipse Second Law ( Law of areas)-orbital velocity Third Law (Law of Periods orHarminc Law) revolution function of distance 4. Types of Satellite Astronomical satellites Communicationsatellites Weather satellites Navigation satellites 5. Types of Satellite Astronomical satellites Communicationsatellites Weather satellites Navigation satellites 6. Communications Satellite A spacecraft placed inorbit around the earthwhich carries on boardmicrowave transmittingand receivingequipment capable ofrelaying signals fromone point to another. It uses microwavefrequency (1-100 Ghz) 7. Reasons for Using Microwave Frequency To penetrate the atmosphere To handle wideband signals encountered in present day communications To make practical use of high gain antennas aboard the spacecraft 8. Satellite Communications 9. Satellite Communications 10. Satellite Communications 11. Anatomy ofSatcom Terminal 12. Anatomy of SatcomTerminal 13. Satellite Service Categories1. Fixed Satellite Service (FSS) cover links between satellites and fixed (non moving earth stations)2. Mobile Service (MSS) cover links to stations that maybe in motion (mobile) including ships (maritime mobile-MMSS), aircraft (aeronautical mobile-AMSS),and land vehicles (land mobile LMSS)3. Broadcast Services include TV (DBS-TV) and audio (DBSA)4. Intersatellite Service satellite-to-satellite cross links 14. DVB 15. Satellite System Elements 16. Space Segment It contains the satellite and all terrestrialfacilities for control and monitoring of thesatellite This includes the tracking,telemetry, andcommand stations(TT&C) with satellitecontrol centerPayload It consists of thereceiving and transmitting antennasand all the electronic equipment thatsupports the transmission of carriersPlatform It consists of allsubsystems that permits the payloadto operate 17. Ground Segment It consists of all the earth stations mostoften connected to the end usersequipment by a terrestrial network, or incase of VSAT, directly connected to theend users equipment 18. Frequency Bands 19. Broad Categories of Satellites Passive Satellite Simply reflects a signal back to earth No gain devices on board to amplify or repeatthe signal Otherwise called bent pipe satellite(frequency translating RF repeater) Active Satellite Receives,amplifies,retransmits the signal Also called processing satellite (used indigital circuits where the signal is demodulatedto baseband and regenerates the signal) 20. Satellite Evolution1. Moon in the late 1940s became the first satellite transponder2. Sputnik 1 the first active earth satellite launched in 1957 by Russia.It transmitted telemetry information for 21 days3. Explorer 1 lunched by USA late that year. It transmitted telemetry information for nearly five months.4. Score a 150-lb conical shaped satellite.It is the first artificial satellite used for terrestrial communications5. Echo- a 100-ft diameter plastic balloon with aluminum coating.It achieved the first transatlantic transmission using a satellite. 21. Satellite Evolution6. Telstar 1- the first satellite to receive andtransmit simultaneously. It was damaged by theradiation of the newly discovered Van Allenbelts.7. Telstar II accomplished the first successfultransatlantic transmission of video8. Syncom 1- was the first attempt to place ageosynchronous satellite into orbit but was lostduring orbit injection9. Intelsat International TelecommunicationsSatellite Organization10. Early Bird the first Intelsat Satellite.Itprovided over 480 voice channels 22. Satellite Orbits The trajectory followed by the satellite inequilibrium between two opposing forces(gravitational force and inertial centrifugalforce) Maximum extension at apogee and minimumat perigee 23. Satellite Orbits(by inclination) 24. Satellite Orbits(By Inclination) Ascending Node Descending Node 25. Satellite Orbit(By Shape) Elliptical Orbit (64 deg inclination) Circular Inclined (Polar orbit) Circular orbit with Zero Inclination(Equatorial) 26. Geosynchronous OrbitGeosynchronous or GeostationaryNon synchronous SatelllitesPrograde or PosigradeRetrograde 27. Satellite Orbit (by Altitude) 28. Satellite Orbits(By Altitude and Shape) 29. Orbit Types by Altitude 30. LEO Circular or inclined orbit < 1400 km altitude Satellite travels across sky from horizon tohorizon in 5 to 15 mins =>needs hand off Earth station must track satellites Large constellation of Satellites (66 needed tocover earth) Requires complex architecture LEO sats need lower RF freq (low distances betsat and ground means lower antenna gains=>lowerfrequencies 31. LEO Applications Communications (voice and high speeddata) Iridium (comprises 66 LEO satellites) Globalstar (fourty-eight satellites) Teledesic (288 satellites for high speed dataservice) Military Surveillance Weather Atmosphere Studies Earth ObservationRemote Sensing Polar ice cap monitoring Tracking plantation changes Rescue and Search 32. MEOHEO Molniya Ellipso Tundra ICO (IntermediateCircular Orbit) CommunicationServices at High Odysseyaltitudes Navistar ArchemedisGEO Voice and DataDirect Broadcastcommunications RadiodeterminationFixed Satelite Serviceand radionavigationInersatellite Links 33. HEO 34. MEO Applications GPS is MEO satellite system GPS satellites broadcast pulsetrains with very accurate timesignals A receiver able to see fourGPS satellites can calculate itsposition within 30 m anywherein the world 24 satellites in clusters of four,12 hour orbital period 35. DisadvantagesAdvantages GEO GEO They suffer great Stationarydeal FSL due to No switchingdistancerequired Time delay They cover larger Congestionarea Coverage problem The effects of(about above 80Doppler shift are deg)negligible Lower angle ofelevation 36. GEO Applications Initial application-telephony Broadcasting (Direct TV) Point to multipoint Video Distribution for Cable TV Mobile Services Inmarsat (International MaritimeSatellite Org ) MSAT (Mobile Satellite) Weather Observation 37. Comparison of Orbit Types 38. Orbital Calculations Any satellite orbiting the earth needs to satisfy thisequation:11 4 x10v = (d + 6400)Where v = velocity in meters/second d = distance above the earths surface in km 39. Sample Problem 01Find the velocity and orbital period of a satellite in a circular orbita) 500 km above the earths surfaceb) 36,000 km above the earths surface 40. Classifications According toStabilization Method Spinner Satellite Use the angular momentum of its spinning body to provide roll and yaw stabilization Three-Axis Stabilizer The body remains fixed relative to earths surface Internal subsytem provides roll and yaw stabilization 41. Classifications According to Territorial Coverage Domestic Satellite Domsat Single country Regional Satellite Specific regions Global Satellite Earth 42. Look Angles Angle of Elevation The angle formed between the direction of travelof a wave radiated from earth station antenna andthe horizontal 5 degrees is the minimum acceptable angle ofelevation Azimuth The horizontal pointing angle of an antenna Measured in clockwise direction in degrees fromtrue north 43. Look Angles 44. Look Angles 45. PAS 4 72 APSTAR 2R 76.5Satellite Location THAICOM 3 78.5 ST 1 - 88 INSAT 1 93.7 ASIASAT 2 100.5 ASIASAT 3 105.5 BS 2 110 PALAPA C2 113 JCSAT 3 128 APSTAR 1A - 134 AGILA 2 146 MEASAT - 148 PAS 8 166 PAS 2 - 169 46. Footprint Spot Beams Small geographic area Zonal Coverage Less than one-third ofthe earths surface Earth Coverage One-third of theearths surface withapproximate antennabeamwidth of 17degrees. 47. Footprint 48. Spacing or Spatial IsolationFactors to be Considered: Bamwidths and sideloberadiation of both the earthsattion and satelliteantennas RF Carrier Frequency Encoding or modulationtechniques Acceptable limits ofinterference Transmit carrier powerNote: 3 to 5 deg is required 49. Frequency ReuseA way to increase the capacity of alimited bandwidth when an allocatedband is filled Methods Frequency Reuse Reducing antenna beamwidth so that different beams of the same frequency can be directed to different geographical areas on earth Dual Polarization (less effective because the atmosphere has a tendency to reorient or repolarize electromagnetic wave) 50. Satellite Communications 51. TVRO Diagram 52. Antenna Theory 53. Satellite System ParametersPath Loss CalculationsPR (dB) = + +d +f )GT (dBi) G R (dBi) (32.44 20log 20logPT 54. Sample Problem 2 Calculate the length of the path to ageostationary satellite from an earth stationwhere the angle of elevation is 30 degrees 55. Sample Problem 3 A satellite operates at 4 GHz with atransmitter power of 7 W and an antennagain of 40 dBi. The receiver has an antennagain of 30 dBi, and the path is 40,000 km.Calculate the signal strength at the receiver 56. Satellite System ParametersAntenna Calculations GAIN BEAMWIDTH 57. Sample Problem 4 A TVRO installation for use with C-bandsatellites (downlink at approximately 4GHz) has a diameter of about 3 m and anefficiency of about 55%. Calculate its gainand beamwidth. 58. Satellite System ParametersTransmit Power and Bit Energy 59. Sample Problem 5 For a total transmit power (Pt) of 1000 W,determine the energy per bit (Eb) for atransmission of 50 Mbps. 60. Satellite System ParametersEffective Isotropic Power (EIRP)-defined as an equivalent transmit power 61. Sample Problem 6 For an earth station transmitter wit anoutput power of 40 dBW (10,000), a back-off loss of 3 dB, a total branching loss andfeeder loss of 3 dB, and a transmit antennagain of 40 dB, determine EIRP 62. Satellite System Parameters Equivalent Noise Temperature 63. Sample Problem 7 A receiver has a noise figure of 1.5 dB.Find its equivalent noise temperature. 64. Satellite System ParametersNoise Density 65. Sample Problem 8 For an equivalent noise bandwidth of 10MHz and a total noise power of 0.0276 pW,determine the noise density and equivalentnoise temperature 66. Satellite System Parameters Carrier-to-Noise DensityRatio The average wideband carrier power-to-noisedensity ratio The wideband carrier power is the combinedcarrier power of the carrier and its associatedsidebands 67. Satellite System ParametersEnergy of Bit-Noise Density Ratio One of the most important and most often usedparameters when evaluating a digital radio system 68. Satellite System ParametersGain-to-Equivalent Noise TemperatureRatio Is a figure of merit used to represent the quality ofa satellite or an earth station receiver 69. Satellite System ParametersAntenna Noise Temperature (cont) 70. Sample Problem 9 A receiving antenna with a gain of 40 dBilooks at sky with a noise temperature of 15K. The loss between the antenna and theLNA input due to feedhorn is 0.4 dB, andthe LNA has a noise temperature of 40 K.calculate G/T (in dB). 71. Satellite System Link Equations 72. Downlink Equation 73. Sample Problem 10 A ground terminal receives a signal from satelliteat a distance of 38,000 km. The satelitte has atransmitter power of 50 watts and an antenna gainof 30 dBi. Assume losses between the satellitetransmitter and its antenna are negligible. Thefrequency is 12 Ghz. Calculate the carrier-to-noiseratio at the receiver for a bandwidth of 1 MHz. Teearth station is found to have G/T of 20.6 dB.