WHAT IS RADAR?


                      WHAT IS  RADAR?


The word radar is coined from the phrase “Radio detection and Ranging”. It is basically an echo-ranging system in which electromagnetic energy in the from of high-power short-duration pulse are sent out at distant objects or targets. The reflected signal or the echo is received at the  transmitting station and analysis  to obtain information on the location of the targets.

Essentially, the radar system consists of a transmitter and receiver, both connected to a directional antenna through a switching arrangement, called a duplexer. A small portion of the pulse power generated by the transmitter excites the duplexer which disconnects the receiver from the antenna and connects the transmitter to the antenna. In most systems, the antenna scans  i,e.,  rotates to direct the radiated beam as desired. The scanning speed is small compared to the speed of light in free space, so that the antenna does not rotate significantly in the time taken by the radiated signal to return from a normal range of targets.

When the transmitted pulse is over, the duplexer disconnects the transmitter from the antenna and reconnects the receiver to the antenna. The reflected pulse are received and processed at the receiver which is invariably super heterodyne.  The demodulated   pulse   are   then fed to an indicator or a display device for analysis.  The transmission and reception of pulses continue as the antenna scans in a predetermined fashion.

In order that the target direction can be precisely found, the radar antenna must have the dimensions of a few wavelengths to produce sharp, narrow beams. Hence short wavelengths have to be used. The pulse-modulated UHF or microwave frequencies are employed in radar. The radar power is typically a few hundred kW.

USE OF RADAR


1)      Military use:

Detection of enemy ships or aircrafts by radar helps aiming of guns at them.
Radar also find applications in searching for submarines and in directing guided missiles.
Ballistic missiles can be detected by radar mounted on satellites.
Radar displays are employed to bomb ships or cities at night or under overcast conditions.

2)      CIVILIAN USE:


As  plains,  oceans, cities, mountains etc. reflect radar signals to different extents, useful information for navigation can be obtained from radar .
Such information is not influenced by darkness or whether conditions. Radar sets housed in ships can locate land, marker buoys, other ships etc. Radar are used in mapping, meteorology, air-traffic control at airports providing landing facilities, and by police forces for traffic speed control and prosecution of  offenders.

3)      Scientific use:


Radar are employed in finding map positions of islands. Valuable information on the distances and motions of different planetary bodies has been obtained with the aid of radar.

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