The radar (RADIO Detection And Ranging) uses electromagnetic (radio) waves to detect targets from a remote location, and determine characteristics of the targets, such as how far away they are and how fast they are moving. Other things that can be known are the size of the target, the direction of the target and the temperature and composition of atmospheric particles. Quantities which characterize radars are carrier frequency, operating frequency, operating power characteristics of radars are their range resolution and sensitivity.
History of RADAR
Nobody can be credited with “inventing” radar. It wasn’t until the early 20th century that a radar system was first built. One of the biggest advocations of radar technology was Robert Watson-Watt, a British scientist. Great Britain made a big effort to develop radar in the years leading up to World War Two. Some people credit them with being pioneers in the field. As it was, the early warning radar system (called “Chain Home”) that they built around the British Isles warned them of all aerial invasions. This gave the outnumbered Royal Air Force the edge they needed to defeat the German Luftwaffe during the Battle of Britain. After the Titanic ran into an iceberg and sank in 1912, people were interested in ways to make such happenings avoidable.
Development of RADAR
Radar was developed (c. 1935-40) independently in several countries as a military instrument for detecting aircrafts and ships. One of the earliest practical radar systems was devised (1934-35) by Sir Robert Watson-Watt, a Scots physicist. Although the technology evolved rapidly during World War II, radar improved immensely following the war, the principal advances being higher power outputs, greater receiver sensitivity, and improved timing and signal-processing circuits. In 1946 radar beams from the earth were reflected back from the moon. Radar contact was established with Venus in 1958 and with the sun in 1959, thereby opening a new field of astronomy – radar astronomy.
How does RADAR work?
The basic idea behind how a radar works is this: a radio pulse is transmitted into the air. It travels out at the speed of light, bounces off a target, and then returns back to the radar to be received. The transmitted signal is said to illuminate the target. When we receive a reflected pulse, we can measure how long the pulse took to travel out to the target and then back to us. Since we know the speed of light, we can then calculate how far away the target is. This is determining the target’s range.
Radar works on the Doppler principal of frequency shift. To know how fast a target is moving, it will actually change the frequency of the radar’s transmitted wave when it reflects it. When a radio wave with a particular frequency will travels out and bounces off a moving target, its frequency will become shifted in a predictable manner according to the speed of the target travelling.
Uses of RADAR
Air traffic control uses radar to track planes both on the ground and in the air, and also to guide planes in for smooth landings.
Police use radar to detect the speed of passing motorists. NASA uses radar to map the earth and other planets, to track satellites and space debris and to help with things like docking and maneuvering. The military uses it to detect the enemy and to guide weapons. Meteorologists use radar to track storms, hurricanes and tornadoes.