Electronics Engineering
Electromagnetic Radiation

How do RADARs work?

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July 15, 2017 2:35AM

  1. the RADAR transmitter sends out a pulse of radio waves
  2. the radio waves bounce off objects
  3. the RADAR receiver picks up the reflected pulses of radio waves
  4. the round trip travel time is measured electronically or displayed on a 2D screen
  5. the travel time tells how far away the objects are

Most modern RADARs use radio waves in the microwave band but HF band, VHF band, and UHF band radio wave have also been used.

Older RADARs use a mechanically rotated or wobbled dish antenna, but many newer RADARs use a stationary Electronically Phased Array flat plane antenna (this type of antenna is another topic just by itself).

LIDARs work the same but use light wave pulses generated by LASERs instead of radio waves.
A basic summary of how radar works is that a pulse is transmitted and any return or echo is listened for. If a return is sensed, the timing between the transmission and the reception of the echo is used to determine how far away an object is. There are some other ways in which radar works as well.
Radar is something that is in use all around us, although it is normally invisible. Air traffic control uses radar to track planes both on the ground and in the air, and also to guide planes in for smooth landings. Police use radar to detect the speed of passing motorists. NASA uses radar to map the Earth and other planets, to track satellites and space debris and to help with things like docking and maneuvering. The military uses it to detect the enemy and to guide weapons.

Radio pulses are transmitted from the antenna, reflect back off objects, and are received again by the same antenna. The time is measured from transmission to reception and used to calculate distances to the objects. In most systems the time measurement & distance calculation are a single implicit operation done directly in the display by calibrating it in distance not time units.