Satelliteis a body that rotates around orbit.
Satellite is used for communication,military, surveillance, etc.Asatellite communications is an artificial satellite positioned in space for thepurposes using micro frequencies. Mostly communications satellites using thenear geostationary orbits and some recent systems use low earth orbitingsatellites.
It provides a technology balancing to that of fiber optic submarinecommunication cables; they have a postponement in a propagation that is calleda path delay. It is of minimum 270ms. This is the time in which a radio signal cover35,800 kmfrom earth to satellite and satellite to earth to complete a trip. Satellite Internet networks average about 600to 800 millisecond delay which is about ten times more than that of a globalInternet link. This delay is a challenge to organization of Virtual privatenetworks over satellite internet connections. USE OF EM WAVES IN SATELLITECOMMUNICATIONEMwaves in Comsat are the firm emerging field of communication which comprises ofmany satellite relays.
In space wave communication the electromagnetic wavesare transferred from the antenna to reach the receiving antenna by two ways,first by direct way of propagation and secondly by reflecting from ground inthe earth’s troposphere region. Troposphereis the area of earth which is from earth surface to 16km. The 180 degree phase occursat the ground when wave reaches the reception antenna.
Thewaves abandon the transmitting antenna with same angle and at same time butthey arrive on reception antenna may be in phase or out phase because both ofthem are going on different path length.Theresultant wave at the reception end can be stronger or weaker than direct path.The signal strength can be measured by the vector addition of direct andindirect waves at receiving end. AsSpace wave propagation through troposphere so it is also known as troposphericpropagation.
Space propagation is generally in higher frequency because at highfrequency propagation of sky waves and ground waves both fail. Spacewave propagation at very high frequency, ultra high frequency and microwavesfrequencies is just limited to the line of sight distance and curving of earth.In line of sight distance transmitting antenna and receiving antenna canusually see each other. The range ofcommunication can also be increased by increasing the heights of transmittingand receiving antennas. The curving of earth and the height of the bothantennas conclude extreme range of communication through direct waves.Spacecommunication means the radio traffic between a ground station andsatellite. By using space communicationwe can extend the line of sight distance because it has capability to transmit microwavesof huge bandwidth.
MAIN COMPONENTS OF A SATELLITECOMMUNICATION SYSTEMSatellitecommunications consists of two main components· Thesatellite· Theground stationThe SatelliteThesatellite is composed of following parts:1. Thesatellite 2. Telemetry controls 3. The transponder Thekey purpose of satellite is to reflect signals.
Its main role is to pick signalfrom ground station. The transponder is made of receiving antenna, a broad bandreceiver and a high power amplifier. The ground station:Itis the installation sited on the earth. Its purpose is to communicate with thesatellites. It consists of a base band processor, uplink converter, high poweramplifier and a dish antenna. From this place data is transmitted to anorbiting satellite. WORKING OF A SATELLITESatelliteworks on the basis of Electromagnetic waves.
A satellite is kept in a space andit revolves around the orbit. It receives the signals from the station andspread them to all electronic devices. The frequency of waves should be smallto send the signals.
So that’s why microwaves are sent to satellite. Satellitegives links in two main ways. Firstly, it delivers point to point communicationbetween the ground stations. One earth station transfer signals to thesatellite station and next ground station receives them from the satellite.Secondly, satellite receives signals from one ground station and transmits tothem to the number of ground receivers.Asatellite uses the frequency of 5.
92 to 6.4 GHZ to transmit data from earth tosatellite. And to transfer data from satellite to earth the frequency of 3.7 to4.1 GHZ is used.
Uses of satellite communication:· Radio and Television Broadcasting· Marine Communications· Global Positioning Services· For communicating voice· In military applications· Providing internet surfing and communication of data throughinternet.