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THE FIRST USE OF RADAR
July 4, 2003
During World War II, battles were won by the side that was first to spot enemy airplanes, ships, or submarines. To give the Allies an edge, British and American scientists developed radar technology to "see" for hundreds of miles, even at night. The research that went into improving radar helped set the stage for post-war research into the transistor.
1940s radar relied on a semiconductor crystal, or "rectifier." Radar worked by sending out a radio wave and analyzing the reflected wave after it bounced off any objects in the air. The rectifier\'s job was to translate the reflected signal into the direct current necessary for visualization on the screen. These crystals often couldn\'t handle the quickness and intensity of a rapidly changing radar signal. They would burn out frequently. A number of institutions, including Purdue, Bell Labs, MIT, and the University of Chicago, joined forces to build better crystals.
Trying different semiconductors and doping with different materials, the researchers learned which combinations produced the best results. Of special importance to semiconductor researchers was Seymour Benzer\'s discovery at Purdue. He found that germanium crystals made the best detectors. (Germanium was used to make the first working transistor five years later.) Scientists also learned new techniques on how best to grow and dope the crystals.
Within the decade, this superb understanding of crystal growing would pay off in unexpected areas, not the least of which were the insights necessary to allow the solid state researchers at Bell Labs to grow the germanium semiconductors that were the heart of the first transistors and that was the base for better technologies.
The importance of radar
Radar, (radio detection and ranging), electronic and remote detection system, used to locate and identify objects beyond the range of vision. This name was used by allied forces during World War II for a variety of devices concerned with radio detection and position finding. Such devices not only indicate the presence and range of a distant object, called the target, but also determine its position in space, its size and shape, and its velocity and direction of motion.
Radar signals bounce of objects in their path, and the radar system detects the echoes of the signals that return. Radar can determine a number of properties of a distant object, such as its distance, speed, direction of motion, and shape. Radar can detect objects out of the range of sight and works in all weather conditions, making it a vital and versatile tool for many industries.
Radar originally developed as an instrument of war, today is used extensively in many peacetime pursuits, such as aiding navigation in the sea and air helping detect military forces, improving traffic safety, detecting weather patterns and providing scientific data.
One of radarís primary uses is a air traffic control both civilian and military. Large networks of ground-based radar systems help air traffic controllers keep track of aircraft and prevent midair collisions. Commercial and military ships also use radar as a navigation aid to prevent collisions between ships and to alert ships of obstacles, especially in bad weather conditions when visibility is poor.
Military forces around the world use radar to detect aircraft and missiles, troop movement, and ships at sea as well as to target various types of weapons. Radar is a valuable tool for the police in catching speeding motorists. In the world of science, meteorologists use radar to observe and forecast the weather.
Other scientists use radar for remote sensing applications, including mapping the surface of the earth from orbit, standing asteroids and investigating the surfaces of other planets and their moons.
How the radar works
Radar equipment consists of a transmitter, an antenna, a receiver, and an indicator. Radar relies on sending and receiving electromagnetic radiation, usually in the form of radio waves or microwaves. Electromagnetic radiation is energy that moves in waves at or near the speed of light (300,000 km/sec, 186,000 mi/sec). Unlike radio broadcasting, in which a transmitter sends out radio waves and receivers intercept them, radar transmitters and receivers are usually located in the same place.
The transmitter broadcasts a beam of electromagnetic waves by means of an antenna, which concentrates the waves into a shaped
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Radar, Continuous-wave radar, Doppler radar, Antenna, Radar signal characteristics, Radar gun
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