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What is radar?
"RADAR" is an acronym for RAdio Detection And Ranging, which is a broadcast beam and receiver, used primarily to detect the objects (such as aircraft) which are at a distance …that cannot be observed visually. It is one of the applications of microwaves. Radar is used along with advanced transponder technology in air traffic control. Smaller radar units have been used to measure the speed of cars and trucks on highways, using the Doppler effect (frequency shift for moving objects), although these have mostly been replaced with laser devices using the same principle. Radar is based on the principle that the RF signal at a high frequency is reflected back by reflective objects, typically large objects made from metal, composites, or rubberized materials. The distance between the radar antenna and the target can be measured by the delay time (microseconds, millionths of a second) between the broadcast and detected return. The reflected signal is known as a 'radio echo'. The time taken by the signal to travel one nautical mile is 6.18 micro seconds, so it requires 12.36 microseconds to reach and return from an object one nautical mile away. The formula to determine the distance of the object 'S' is S=T/12.34 where 'T' is the time taken for the transmission and reception of the signal. --- Radar is an acronym for RAdio Detection and Ranging. It uses RF transmission (radio frequency) in the microwave band to detect and range any detectable target within its range. It is an "active sensor" which emits RF waves that bounce off a target and are detected when the wave is received back. The time delay between transmission and detection produces its range given that the RF wave propagates at a uniform speed. Modern "stealth" aircraft use RF scattering, along with microwave-absorbing materials, to avoid detection by traditional radar. Some advanced planes have radar reflection signatures so low that they are less than those of small birds. (MORE)
