21-07-2012, 04:09 PM
RADAR
RADAR.pptx (Size: 1.14 MB / Downloads: 168)
RAdio Detecting And Ranging
Radar measurement of range, or distance, is made possible because of the properties of radiated electromagnetic energy
This energy normally travels through space in a straight line, at a constant speed
Electromagnetic energy travels through air at approximately the speed of light
300,000 kilometers per second
186,000 statute miles per second
162,000 nautical miles per second
Radar Basic Principles
The radio-frequency (RF) energy is transmitted to and reflected from the reflecting object.
A small portion of the reflected energy returns to the radar set. This returned energy is called an ECHO, just as it is in sound terminology
Radar sets use the echo to determine the direction and distance of the reflecting object.
Main Classification of radar
There are two types of radar units.
1.Primary radar
2.Secondary radar
Primary radar are of two types
1.Pulse radar
2.Continuous wave radar
Continuous wave radar are of types
1.Unmodulated
2.Modulated
Primary radar
A primary radar transmits high frequency signals which are reflected at targets. A primary radar unit receives its own emitted signals as an echo.
A pulse radar units transmit a high frequency impulsive signal of high power. After this a longer break in which the echoes can be received follows before a new transmitted signal is sent out. Direction, distance and sometimes if necessary the altitude of the target can be determined from the measured antenna position and propagation time of the pulse signal.
A cw radar units transmit a high frequency signal continuously. The echo signal permanently is received and processed.