06-03-2013, 03:59 PM
Radio Detection and Ranging
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‘INTRODUCTION
Meaning of RADAR is “Radio Detection and Ranging ”radar is introduced in II world war , for detecting enemies movement.
Radar is an electromagnetic system which is used for detection of objects like aircraft ,sheep ,vehicles and other environmental effects.
RADAR transmitted an electromagnetic waves ,these waves strike on target signal and reflect back from the target is called echo signal, reflected signal received by radar it gives the presence of target .
The RADAR does not affected from rain, fog , darkness etc. in typical climate condition radar measure distance with high accuracy.
BASIC PRINCIPLE OF RADAR
Radar transmitter transmitted electromagnetic waves that is travel in free space by an antenna. The transmitted electromagnetic signal strike on target, and radiate from the target in the form of echo signal. This echo signal is collected by the radar receiver. The echo signal processed by radar receiver and determine the location and range of target. The range of target determined by measuring the time it takes for the transmitted signal to travel to target and return back to radar.
Transmitter: The transmitter may be microwave amplifier such as the klystron and might be a microwave oscillator such as the magnetron. The magnetron provides high average power. Controlled by pulse generator.
Antenna: Antenna is used for transmission and receiving for the signal. Antenna may be a parabolic reflector or planner array or electronically streered phased array.
Duplexer: Duplexer permits a single antenna can be used on time shared basis of both transmitting and receiving. when transmitter is in operating mode, the duplexer produces a short circuit at the input to the receiver, so that transmitting power flows to the antenna not to the receiver.
Other Application
(i) Continuous wave radar widely used by police for enforcing speed limit.
(ii) To determine height of aircraft above the horizon.
And the space craft have used radar for rendezvous and docking for landing on the moon.