Question

List applications of Doppler Radar.

Answer 1

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Answer 2

RADAR, which stands for Radio Detection and Ranging, is a common method of detecting moving objects. For instance the police use Doppler radar to detect the speed of a moving vehicle. An Austrian physicist by the name of Doppler, first described the concept in the 19 th century. The Doppler effect describes what happens when a wave (sound, radio, etc.) hits a moving object.

For example, police use a radar detector to determine the speed of a car as it moves down the highway. Radar waves are transmitted from the police car at a certain frequency. Recall that waves have both amplitude and frequency. When the waves bounce off a moving object their frequency is effected. As the radio waves bounce of a car that is moving toward the detector the frequency of the wave decreases. If the waves bounce of a car moving away from the detector the frequency of the wave increases. The detector uses the difference in the transmitted and received wave frequencies to determine the speed of the car.

Radar technology has now been built into a new flashlight sized device that can detect human movement through a door or wall. The device can detect movement due to human respiration from up to three metres away. The device will prove useful for police in detecting criminals in an ambush situation, when doing bed checks in prisons or for determining the location of hostages in a building. The device could also be used to locate the survivors of an earthquake or avalanche.

Radar technology may also be used to detect land mines. NATO is spending millions to develop a device to identify and neutralize land mines. The basic technology consists of two antennas that focus radar energy to a point just below ground a few feet in front of the person carrying the antenna. The device is programmed to ignore signals that bounce back from the surface and to make buried objects shine brighter in the radar image. This allows the operator to actually detect the land mines without ever touching the ground.