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

MODULE A- INTRODUCTION TO RADAR
2.3. Operation Principle of Radar
Operation principle of a radar is very simple in theory and very similar to the way which bats use
naturally to find their path during their flight (Figure-2.2). Bats use a type of radar system by
emitting ultra-sonic sounds in a certain frequency (120 KHz) and hearing the echoes of these
sounds. These echoes make them enable to locate and avoid the objects in their path.
Figure-2.2
In the radar systems, an electromagnetic wave generated by the transmitter unit is transmitted by
means of an antenna, and the reflected wave from the objects (echo) is received by the same
antenna, and after processing of the returned signal a visual indication is displayed on indicators.
After a radio signal is generated and emitted by a combination of a transmitter and an antenna, the
radio waves travel out in a certain direction in a manner similar to light or sound waves. If the
signals strike an object, the waves are reflected and the reflected waves travel in all directions
depending of the surface of the reflector. The term reflectivity refers to the amount of energy
returned from an object and is dependent on the size, shape, and composition of the object. A small
portion of the reflected waves return to the location of the transmitter originating them where they
are picked up by the receiver antenna. This signal is amplified and displayed on the screen of the
indicators,e.g. PPI (Plan Position Indicator). This simple approach can be achieved by means of
many complex process including hardware and software components.
TURKEY RADAR TRAINING 1.0 / ALANYA 2005 9