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The term "Radar" stands for radio detection and ranging. Thus, it is used for detecting and locating targets, which are capable of reflecting high frequency radio waves (microwaves), generally in the wavelength range from a fraction of a centimetre to some tens of centimetres. Radar detects its target by measuring the time interval between transmitted and received radio pulses. Hence, it provides information on the range, azimuth, and/or elevation of objects in the path of the transmitted pulse.
Working
The working of Radar system is based on Doppler effect. The system has a transmitter that emits radio waves. At the same time, these waves are reflected by the target, and detected by a receiver, typically in the same location as the transmitter. Even though the radio signal reflected back is usually very small, radio signals can easily be amplified, so radar can detect objects at ranges where other emission, such as sound or visible light, would be too weak to detect. Radar find application in many places, such as meteorological detection of precipitation, air traffic control, police detection of speeding traffic, and by the military.
Types of Radar
There are two Types of Radar Detectors:
1. Pulse radar
2. Continuous-wave radar
* Doppler Radar
* Frequency-Modulated Radar
Pulse Radar
Pulse Radar emits signals in within few millionths of a second with a powerful bursts or pulses. Pulse Radar determines distance (range) by calculating the time taken for radar wave to get to hit the target object and to come back (time of flight). The radar then divides that time in two (distances to the target). Since all radio waves travel at the same speed of light, this known speed multiplied by the time of flight can be used to determine distance. By continuing to track an object with pulse radar the speed of the object can also be determined.
Continuous-Wave Radar
Continuous-Wave Radar emits continuous signal instead of short bursts. There are two types of Continuous Wave Radar:
1. Doppler Radar
2. Frequency Modulated (FM radar)
a) Doppler Radar is used mostly to make precise speed measurements. Doppler Radar sends a continuous wave of a constant frequency. On striking some moving object, the frequency sent by radar changes and the new frequency is returned to the radar. This is used to determine the speed of the moving target. Examples of Doppler Radar - Decatur Police Radar Guns.
b) Frequency-Modulated Radar also transmits a continuous signal, but it rapidly increases or decreases the frequency of the signal at regular intervals. As a result FM Radar, unlike Doppler Radar, can determine distance (range) as well as velocity (speed).
Application of Radar
Commercial airliners fitted with radar devices that warn of obstacles in or approaching their path and give accurate altitude readings.
In a dense fog surrounding, Planes can land at airports equipped using radar-assisted ground-controlled approach (GCA) systems, in which the plane`s flight is observed on radar screens while operators radio landing directions to the pilot. A ground-based radar system for guiding and landing aircraft by remote control was developed in 1960.
Radar is used to measure distances and map geographical areas (shoran) and to navigate and fix positions at sea. Meteorologists use radar to study and warn against severe weather such as thunderstorms and tornado. Also, Radar can be used to study the planets and the solar ionosphere and to trace solar flares and other moving particles in outer space.
Radars are also widely used for defence purpose in form tracking and surveillance systems.
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