SATELLITE COMMUNICATION – an Overview A TECHNICAL SEMINAR BY V sasank chaitanya kumar,
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Introduction The never ending quest of communication engineer is to transmit maximum information in short time to the largest possible distance,this gave raise to many systems of communications. Disadvantages of exisiting broad band methods: Coaxial cables,Fiberoptics - Wiring problem Microwaves - LOS
Defination of satellite Satellite can be defined as a heavy object which goes around object in space due to the effect of mutual gravitational forces,used for broadband communication. Why satellites came into picture?? This is because the earth is like a sphere As we know radio waves travel in straight lines at micro wave frequenices A repeater is needed to convey signal over long distance Satellites are used to link places on earth that are thousands of miles a part
Need of satellite for long distance communication
Types of Satellites Active satellite It is one in which the signal is amplified and itsfrequency changed by transponder,before itsent back toearth. Example:communication,broadcasting satellites Passive satelliteThese type of satellites simply reflects or scatters themicro wave signal back to another stationExample:military and non profitable servieces
Satellite picturesOctober 1957, the first The first artificial passive In July 1962 active satelliteartificial satellite Sputnik satellite Echo-I of NASA was Telstar was developed and-I was launched by launched in August 1960. launchedformer Soviet Russia.
Advantages of Satellites The advantages of satellite communication over terrestrial communication are: The coverage area of a satellite greatly exceeds that of a terrestrial system. Transmission cost of a satellite is independent of the distance from the center of the coverage area. Higher Bandwidths are available for use.
Disadvantages of Satellites Launching satellites into orbit is costly. Satellite bandwidth is gradually becoming used up. There is a larger propagation delay in satellite communication than in terrestrial communication.
Satellite Transmission Bands Frequency Band Downlink Uplink C 3.7-4.2 GHz 5.92-6.42 GHz Ku 11.7-12.2 GHz 14.0-14.5 GHz Ka 17.7-21.2 GHz 27.5-31.0 GHzThe C band is the most frequently used. The Ka and Ku bands are reserved exclusivelyfor satellite communication but are subject to rain attenuation
Types of Satellite Orbits Based on the inclination, i, over the equatorial plane: Equatorial Orbits above Earth’s equator (i=0°) Polar Orbits pass over both poles (i=90°) Other orbits called inclined orbits (0°<i<90°) Based on Eccentricity Circular with centre at the earth’s centre Elliptical with one foci at earth’s centre
What is Apogee and Perigee?
Where satellites are placed?Satellite orbits are also classified in terms of the orbital height. These are:
s1Breif overview of orbits s2 s3
ELEMENTS OF SATELLITE COMMUNICATIONS SYSTEMTwo major elements of Satellite Communications Systems are: Space Segment Ground SegmentThe Space Segment includes: Means for launching satellite Satellite(Transponders) Power supply systemThe ground segment consists of: Earth Stations Rear Ward Communication links
Functioning of Transponder TO /FROM EARTH STATION
Power requriment Modern satellites use a variety of power means Solar panels are now quite efficient, so solarpower is used to generate electricity Batteries are needed as sometimes thesatellites are behind the earth - this happens abouthalf the time for a LEO satellite Nuclear power has been used - but notrecommended
Earth Station Block diagram
SATELLITE COMMUNICATION SERVICESDifferent Satellite Communications services are classified as one way link Two way link. One way link from transmitter Tx to receiver Rx on earth’ssurface
Examples of satellite services where the transfer ofinformation takes place through one way link are: Broadcast Satellite Service (Radio, TV, Data broadcasting) Data Collection Service (Hydro meteorological data collection) Space operations service, (Tracking, Telemetry, Command) Safety services (Search & Rescue, Disaster Warning) Earth Exploration Satellite Service (Remote Sensing) Radio Determination Satellite Service (Position location) Reporting Service (fleet monitoring)
Two-way Satellite Communications link Fixed Satellite Service (Telephone, telex, fax, high bit ratedata etc.) Mobile Satellite Service (Land mobile, Maritime, Aero-mobile,personal communications)Satellite News Gathering (Transportable and Portable )
Your Feedback on this session is Important 12/16/12 By Deepak 24 Poonam sasank