training course on weather radar systems - RTC, Regional Training ...

MODULE A- INTRODUCTION TO RADAR
The ASR system consists of two subsystems: primary surveillance radar and secondary
surveillance radar. The primary surveillance radar uses a continually rotating antenna mounted
on a tower to transmit electromagnetic waves, which reflect from the surface of aircraft up to 60
nautical miles from the radar. The radar system measures the time required for the radar echo to
return and the direction of the signal. From this data, the system can measure the distance of the
aircraft from the radar antenna and the azimuth or direction of the aircraft from the antenna. The
primary radar also provides data on six levels of rainfall intensity. The primary radar operates in
the range of 2700 to 2900 MHz.
The secondary radar, also called as the beacon radar, uses a second radar antenna attached to the
top of the primary radar antenna to transmit and receive aircraft data such as barometric altitude,
identification code, and emergency conditions. Military and commercial aircraft have
transponders that automatically respond to a signal from the secondary radar with an
identification code and altitude.
4.4. 3D Radars
A three-dimensional radar is capable of producing three-dimensional position data on a
multiplicity of targets (range, azimuth, and height). There are several ways to achieve 3D data. A
2D radar just provides azimuth and range information.
4.5. Senthetic Aperture Radars
SAR are being used in air and space-borne systems for remote sensing. The inherent high
resolution of this radar type is achieved by a very small beam width which in turn is generated by
an effective long antenna, namely by signal-processing means rather by the actual use of a long
physical antenna. This is done by moving a single radiating line of elements mounted e.g. in an
aircraft and storing the received signals to form the target picture afterwards by signal
processing. The resulting radar images look like photos because of the high resolution. Instead of
moving a radar relatively to a stationary target, it is possible to generate an image by moving the
object relative to a stationary radar. This method is called Inverse SAR (ISAR) or range Doppler
imaging.
4.6. Continuous Wave (CW) Radars
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TURKEY RADAR TRAINING 1.0 / ALANYA 2005