Electronic Communications Systems Wayne Tomasi Engr. E. B. Pioquinto Definition Satellite is a celestial body that orbits around a planet. Natural Satellite Artificial satellite Passive Active Engr. E. B. Pioquinto In 1954, the moon became the first passive satellite 1957, Russia launched Sputnik 1, the first active earth satellite which transmitted telemetry information for 21 days. 1958, NASA launched Score, which recorded and rebroadcasted Pres. Eisenhower Christmas message.Engr. E. B. Pioquinto Short History 1960, NASA launched Echo, a 100ft diameter balloon with aluminum coating which is used for the first transatlantic transmission. Also Courier, the first transponder type satellite which transmitted 3W of power for 17 days, was launched by DoD. 1962, AT&T launched Telstar I, the first satellite to simultaneously receive and transmit signals and was destroyed by Van Allen belt radiation . Engr. E. B. Pioquinto Short History 1963, Telstar II was launched and was the first to transmit transatlantic video signals. 1963, Syncom I was the first attempt to place geosynchronous satellite into orbit and was lost during injection. In 1964, Tokyo Olympics was broadcast using Syncom III which was launched in August 1964 1965, Intelsat (Early Bird) was the first commercial satellite with two transponders and a 25-MHz bandwidth to carry one TV and 480 voice channels. Engr. E. B. Pioquinto Short History In 1966, Soviet Union launched the first set of domestic satellites (Domsats), called Molniya lightning, which are owned operated and used by a single country. 1972, Anik little brother which is Canadas first commercial satellite was launched 1975, Western Unions Westar was launched Engr. E. B. Pioquinto Short History Satellites remain in orbit following German astronomer Johannes Keplers Laws. Keplers laws can be applied to any two bodies in space that interact through gravitation. 1. Satellites will orbit a primary body following an elliptical path 2. For equal intervals of time, a satellite will sweep out equal areas in the orbital plane, focused at the barycenter.Engr. E. B. Pioquinto Keplers laws 3. The square of the time of revolution of a planet divided by the cube of its mean distance from the sun gives a number that is the same for all planets (also known as Harmonic Law). Engr. E. B. Pioquinto 32AP = os) (kilometer axis semimajor= o) 56 23 ( daysidereal one of ratio the days earthsolarmeanMin H t Ps = = =9972 . 0 ) 24 ( axis ownits earth to of revolution one of time the to = = H tS42241.0979 constant= = AKeplers laws Engr. E. B. Pioquinto F1 F2 Center of Ellipse Semimajor Axis, Semiminor Axis, Keplers laws Engr. E. B. Pioquinto D1 V1 D2 V2 Earth orbit A1 A2 Keplers laws Satellite orbits based on direction of motion: Prograde orbit (or Posigrade): if the satellite orbiting is in the same direction as the Earths rotation (counterclockwise) and at angular velocity greater than that of Earth (s > e) Retrograde: if the satellite is orbiting in the opposite direction as the Earths rotation or in the same direction with an angular velocity less than that of the Earth (s < e) Engr. E. B. Pioquinto Satellite Orbits Satellite orbits based on altitude: Low Earth Orbit (LEO): Medium Earth Orbit (MEO): 6,000 to 12,000 miles above Earth Geosynchronous Earth Orbit (GEO): 22,300 miles above Earth. (Also Geostationary orbit, Clarke orbit) Engr. E. B. Pioquinto Satellite Orbits Engr. E. B. Pioquinto Polar Equatorial Inclined Equator geocenter Satellite Orbital Patterns Engr. E. B. Pioquinto Apogee 40,000 km Perigee 400 km Non-synchronous Orbits Engr. E. B. Pioquinto Angle of inclination Equatorial plane 0 Earths direction of rotation N Angle of Inclinition Semimajor axis: (distance from satellite revolving in the geosynchronous orbit to the center of the Earth) = 42,146 km. Earths equatorial radius: = 6378 km. Height above means sea level of satellite in Geosynchronuous orbit: = 35,768 km. Velocity of satellite in geosynchrounous orbit:= 6,840 mph.Engr. E. B. Pioquinto Geosynchronous Satellite Orbit Engr. E. B. Pioquinto Geosynchronous Satellite Orbit 1. Expensive tracking device is not required 2. Satellites are available all the time to earth stations under their footprint 3. No transmission breaks due to switching from one satellite to another 4. Effects of Doppler shift are negligible Engr. E. B. Pioquinto Advantages of Geosynchronous Satellites 1. They require sophisticated and heavy propulsion devices on board to keep them in a fixed orbit. 2. They introduce longer propagation delay 3. Because of the distance, they require higher transmit powers and more sensitive receivers Engr. E. B. Pioquinto Disadvantages of Geosynchronous Satellites Engr. E. B. Pioquinto ( ) 640010 411+=dvv = velocity of satellite in meters per second d = distance above earths surface(km) T = orbital period , time it takes a satellite to rotate around Earth(sec) gR2 = gravitational constant = 4 x 105km3/sec2 Orbital Calculation ( )23gRR d2 T+= t For optimized performance, direction of maximum gain (referred to as boresight) of an earth station must be pointed directly at a satellite. For good alignment, azimuth and angle of elevation of antennas (referred to as antenna look angles) must be determined. Engr. E. B. Pioquinto Antenna Look Angles Azimuth: horizontal angular distance from a reference direction, either the southern or northernmost point of the horizon. Azimuth is the turning of your satellite dish East and West or Left & Right. Engr. E. B. Pioquinto Antenna Look Angles Angle of elevation: the vertical angle formed between the direction of travel of an electromagnetic wave radiated from an earth station pointing directly toward a satellite and the horizontal plane. Engr. E. B. Pioquinto Antenna Look Angles Skew or Polarity: this is how much you turn your LNB. For positive skew, turn the LNB counter-clockwise. For negative skew, turn the LNB clockwise Engr. E. B. Pioquinto Antenna Look Angles Slant distance: (also satellite range) the line of sight distance between an earth station and the satellite. Engr. E. B. Pioquinto Antenna Look Angles Engr. E. B. Pioquinto ( )||.|

\| =| tantancos1EZLA( ) ( ) | |L ED L cos cos cos1 =|S E Ll l D =Antenna Look Angles Engr. E. B. Pioquinto El = antenna angle of elevationR = earths radius = 6378 H= satellite height in kmLE = earth station latitude DL = difference in longitude between satellite and earth station lE = earth station longituded = slant distance lS = satellite longitude ( ) ( )((

+ =| | sin ) tan(1tan1H RREl( ) ( ) ( ) El R H R El R d2 22cos sin + + =Antenna Look Angles Engr. E. B. Pioquinto Spinner Satellite SimpleLight Inexpensive Quick to build Satellite Classifications (Designs) Engr. E. B. Pioquinto 3-axis stabilized satellite More power More channels Longer lifetime More coverage Satellite Classifications (Designs) Footprint is the geographical representation of a satellite antennas radiation pattern. This is the area on earths surface that the satellite can receive from or transmit to. The size and shape of the satellites footprint depends on the orbital path, height and antenna used. Engr. E. B. Pioquinto Satellite radiation patterns (Footprints) Engr. E. B. Pioquinto Satellite radiation patterns (Footprints) Engr. E. B. Pioquinto Satellite radiation patterns (Footprints) Spot beam (or Zonal Beam): typically have proportionately higher EIRP and covers less than 10% of the earths surface Hemispherical beams: typically have EIRP that is 50% lower than spot beams and covers about 20% of the earths surface Earth (global) beam: has power levels considerably less than spot and hemispherical beam and covers about 42% of the earths surface Engr. E. B. Pioquinto Footprint Categories Engr. E. B. Pioquinto Modulator (FM, PSK, QAM) Mixer MW Gen. (6GHz 0r 14GHz) BPFHPABPF Up-converter Baseband in FDM or PCM/TDM To sat. Xponder Satellite Uplink Model Engr. E. B. Pioquinto LNAMixer MW Shift Oscillator (2GHz) BPFHPABPF Frequency Translator To other transponders From earth station 6 GHz to 14GHz To earth station 4 GHz to 12GHz Satellite Transponder Engr. E. B. Pioquinto From sat. xponder LNAMixer MW Gen. 4/12 GHz BPFBPF Down-converter Demod (FM, PSK, QAM) Basebandout Satellite Downlink Model ES1ES1 Engr. E. B. Pioquinto Earth Crosslink or intersatellite link Uplink/downlinkUplink/downlink Inter-satellite Link Engr. E. B. Pioquinto END Thank You