the important communication systems are introduced and their applications are briefly discussed. . . SATELLITE AND ITS COMMUNICATION The satellite communication is a mode of transmission of the signal between transmitter and receiver via satellite.
The message signal from the Earth station is transmitted to the satellite on board via an uplink (frequency band GHz), amplified by a transponder and then retransmitted to another Earth station via a downlink (frequency band GHz) (Figure . ). Applications Satellites are classified into different types based on their applications. Earth Earth receiving station Earth transmitting station Downlink Uplink Satellite (in geostationary orbit) Figure .
Satellite communication system - - - - - - - - Unit electronics and Communication the objects that are invisible to the human eye can be determined. Radar uses electromagnetic waves for communication. The electromagnetic signal is initially radiated into space by an antenna in all directions. When this signal strikes the targeted object, it gets reflected or reradiated in many directions.
This reflected (echo) signal is received by the radar antenna which in turn is delivered to the receiver. Then, it is processed and amplified to determine the geographical statistics of the object. The range is determined by calculating the time taken by the signal to travel from RADAR to the target and back. Applications Radars find extensive applications in many fields.
i) In military, it is used for locating and detecting the targets. ii) It is used in navigation systems such as ship borne surface search, air search and missile guidance systems. iii) Radars are used to measure precipitation rate and wind speed in meteorological observations. iv) It is employed to locate and rescue people in emergency situations.
. . MOBILE COMMUNICATION Mobile communication is used to communicate with others in different locations without the use of any physical connection like wires or cables. It allows the transmission over a wide range of area without the use of the physical link.
It enables the people to communicate with each other regardless of a particular location like office, house etc. It also provides communication access