01-12-2012, 06:19 PM
RADAR
RADAR.pptx (Size: 2.28 MB / Downloads: 45)
What is RADAR ?
RADAR is an object detection system that uses electromagnetic waves
to identify the range,altitude,direction or speed of both moving and
fixed objects such as aircrafts,ships,motor vehicles,weather
formations and terrain.
Distance Determination
The distance is determined from the running time of the high frequency transmitted
signal and the propagation c0. The actual range of a target from the radar is known
as slant range. Slant range is the line of sight distance between the radar and the
object illuminated. Since the waves travel to a target and back, the round trip time is
dividing by two in order to obtain the time the wave took to reach the target.
Therefore the following formula arises for the slant range:
R = c0· t/2 where: c0 = speed of light = 3·108 m/s t = measured running time [s] R = slant range antenna - aim [m]
The distances are expressed in kilometers or nautical miles
(1 NM =1.852 km).
Elevation Angle
Altitude or height-finding search radars use a very narrow beam in
the vertical plane. The beam is mechanically or electronically
scanned in elevation to pinpoint targets.
The elevation angle is the angle between the horizontal plane and
the line of sight, measured in the vertical plane. The Greek letter
Epsilon (ε) describes the elevation angle. The elevation angle is
positive above the horizon (0° elevation angle), but negative below
the horizon.
Surface Movement Radar
The Surface Movement Radar (SMR) scans the airport surface to locate
the positions of aircraft and ground vehicles and displays them for air traffic controllers in bad weather. Surface movement radars operate in J- to X- Band and use an extremely short pulse-width to provide an
acceptable range-resolution.
Radar Absorbent Paint
One of the most commonly known types of RAM is iron ball paint. It contains tiny spheres coated with carbonyl iron or ferrite. Radar waves induce molecular oscillations from the alternating magnetic field in this paint, which leads to conversion of the radar energy into heat. The heat is then transferred to the aircraft and dissipated.