SATELLITE COMMUNICATION – an Overview A TECHNICAL SEMINAR BY V sasank chaitanya kumar,
SATELLITE COMMUNICATION – an Overview
A TECHNICAL SEMINARBY
V sasank chaitanya kumar,
Topics of presentation
introduction
Types of
satellites
Frequency
bands
Where these
are placed
Working
princple
application
s
SATELLITE
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 its frequency changed by transponder,before itsent back to earth. Example:communication,broadcasting satellites
Passive satellite These type of satellites simply reflects or scatters the micro wave signal back to another station Example:military and non profitable servieces
Satellite pictures
October 1957, the first artificial satellite Sputnik -I was launched by former Soviet Russia.
The first artificial passive satellite Echo-I of NASA was launched in August 1960.
In July 1962 active satellite Telstar was developed and launched
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
The C band is the most frequently used. The Ka and Ku bands are reserved exclusively for satellite communication but are subject to rain attenuation
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 GHz
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:
Breif overview of orbits
s1
s2 s3
ELEMENTS OF SATELLITE COMMUNICATIONS SYSTEM
Two major elements of Satellite Communications Systems are: Space Segment Ground Segment
The Space Segment includes: Means for launching satellite Satellite(Transponders) Power supply system
The ground segment consists of: Earth Stations Rear Ward Communication links
DVB-RCS
Outbound subscriber(target of interest)
Gateway stationCentral Hub
SatMon station
Functioning of Transponder
TO /FROMEARTH STATION
Power requriment
Modern satellites use a variety of power means
Solar panels are now quite efficient, so solar power is used to generate electricity
Batteries are needed as sometimes the satellites are behind the earth - this happens about half the time for a LEO satellite
Nuclear power has been used - but not recommended
Earth Station Block diagram
Earth stations
SATELLITE COMMUNICATION SERVICES
Different Satellite Communications services are classified as one way link Two way link.
One way link from transmitter Tx to receiver Rx on earth’s surface
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)
Examples of satellite services where the transfer of information takes place through one way link are:
Two-way Satellite Communications link
Fixed Satellite Service (Telephone, telex, fax, high bit rate data etc.)
Mobile Satellite Service (Land mobile, Maritime, Aero-mobile, personal communications)
Satellite News Gathering (Transportable and Portable )
04/10/23 By DeepakPoonamsasank
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