Radar

Radar (Radio Detection And Ranging) is an object-detection system that uses radio waves to determine the range, angle, or velocity of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio waves or microwaves that bounce off any object in their path. The object returns a tiny part of the wave's energy to a dish or antenna that is usually located at the same site as the transmitter.

History

Radar was secretly developed by several nations before and during World War II. The term RADAR was coined in 1940 by the United States Navy as an acronym for RAdio Detection And Ranging. The term radar has since entered English and other languages as a common noun, losing all capitalization.

Principles

A radar system has a transmitter that emits radio waves called radar signals in predetermined directions. When these come into contact with an object they are usually reflected or scattered in many directions. Radar signals are reflected especially well by materials of considerable electrical conductivity—especially by most metals, by seawater and by wet ground. Some of these make the use of radar altimeters possible. The radar signals that are reflected back towards the transmitter are the desirable ones that make radar work. If the object is moving either toward or away from the transmitter, there is a slight equivalent change in the frequency of the radio waves, caused by the Doppler effect.

Types of Radar

There are several types of radar systems, including:

• Continuous Wave Radar: This type of radar is used to determine the radial velocity of a target.
• Pulse Radar: This type of radar uses a high power output and a low duty cycle.
• Doppler Radar: This type of radar uses the Doppler effect to measure the velocity of a target.
• Synthetic Aperture Radar: This type of radar is used to create two-dimensional images or three-dimensional reconstructions of objects.

Applications

Radar has a wide range of applications, including:

• Aviation: Radar is used in air traffic control to guide planes both on the ground and through controlled airspace.
• Meteorology: Weather radars are used to detect precipitation, calculate its motion, and estimate its type (rain, snow, hail, etc.).
• Military: Radar is used for many purposes, such as air traffic control, navigation, surveillance, and weapon targeting.
• Space exploration: Radar is used to map the surface of planets and moons, and to detect distant objects in space.

See Also

• Radio waves
• Microwaves
• Doppler effect
• Radar altimeter
• Weather radar
• Air traffic control
• Space exploration

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