Radar, stands for Radio Detection and Ranging, is a technology used to detect and track objects in the surrounding environment. It works by emitting radio waves and analysing the signals that bounce back when they encounter objects. Radar consists of two main components: a transmitter and a receiver. The transmitter generates radio waves, which are electromagnetic waves similar to light waves but with much longer wavelengths.
Principle of Radar
The radar transmitter sends out short bursts of radio waves, often referred to as radar pulses. These pulses are directed into the desired area or towards a specific target. When the radio waves encounter an object, such as an aeroplane, they bounce off the object and return back to the radar system. This is known as the radar echo.
The receiver of the radar system detects the reflected radio waves and measures their time of flight, which is the time it takes for the waves to travel to the object and back. By knowing the speed of radio waves, the system can calculate the distance to the object. If the radar is able to use doppler principle, the radar system can not only detect the presence of objects but also estimate their distance, speed, direction, and even their size or shape in some cases.
Characteristics and Construction of Radar Systems
Radar uses narrow and directional beams in SHF and EHF bands. These systems have a movable antenna. If the aid is designed for a 360 degree picture the antenna is rotated around 360 degrees to get a 360 deg picture. Since the power transmitted by Radar is quite high Radar antennas obtain their power through wave guides instead of wires. Wave guides are vacuum filled flexible tubes of half wave lengths. Wave guides have low levels of resistance thereby provide greater power supply to the transmitter ariel.
Properties of Parabolic Radar Antenna
Radar systems use parabolic dish antenna to produce accurate parallel and directional waves. Parabolic antennas produce parallel waves using a parabolic reflector which are attached behind the transmitter. Waves beams produced are of equal path length and in the same phase as the transmitted wave. We had discussed in our earlier lessons about side lobes. The effect of side lobes is pronounced in parabolic dish antenna. Side lobes from parabolic dish may affect the functioning of radio aid.
Airborne Radar Antenna Properties
As we know it is not possible to carry a huge parabolic dish on board aircraft. Therefore radar antenna designed for aircraft are smaller and of different shape. Flat plate or Slotted planar array antenna are used in Airborne weather radars. This antenna transmits half length waves through slots in a metal plate instead of transmitting a single wave like ground radars. Flat plate antennas produce extremely narrow beams with high energy levels. These antennas reduce the formation of side lobes and consume lesser power as compared to parabolic dish antenna.