Techee informAtion regarding radar technology and how it works..........

 Radar means:

Radar is an object-detection system that uses radio waves to determine the range, altitude, direction, or speed 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.

Radar was secretly developed by several nations before and duringWorld 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.

The modern uses of radar are highly diverse, including air traffic control, radar astronomy, air-defense systems, antimissile systems;marine radars to locate landmarks and other ships; aircraft anticollision systems; ocean surveillance systems, outer space surveillance and rendezvous systems; meteorological precipitation monitoring; altimetry and flight control systems; guided missile target locating systems; and ground-penetrating radar for geological observations. High tech radar systems are associated with digital signal processing and are capable of extracting useful information from very high noise levels.

Other systems similar to radar make use of other parts of the electromagnetic spectrum. One example is "lidar", which uses visible light from lasers rather than radio waves.

How radar works:

The Basic Idea:

The basic idea behind radar is very simple: a signal is transmitted, it bounces off an object and it is later received by some type of receiver.  This is like the type of thing that happens when sound echo's off a wall.  (Check out the image on the left)  However radars don't use sound as a signal.  Instead they use certain kinds of electromagnetic waves called radio waves and microwaves.  This is where the name RADAR comes from (RAdio Detection And Ranging).  Sound is used as a signal to detect objects in devices called SONAR (SOund NAvigation Ranging).  Another type of signal used that is relatively new is laser light that is used in devices called LIDAR (you guessed it...LIght Detection And Ranging).              Radio waves and microwaves are two types of electromagnetic waves.  Electromagnetic waves, which I will call EM waves, like all waves transport energy but can do so through a vacuum.  Sound waves and ocean waves require matter to transport energy but EM waves can do so without the presence of matter.  Because of this, satellites can use radars to work on projects outside of the Earth's atmosphere and on other planets.  Another useful thing about EM waves is that they travel at a constant speed through a vacuum called the speed of light abbreviated by the letter "c" (299,792,458 meters per second).  This is very useful to know to when doing ranging calculations.  To learn more about EM waves or waves in general, please visit The Physics Classroom.  Radio waves have wavelengths that are 10 cm and greater and microwaves have wavelengths that range from 10 cm to 1/10 of a mm.  (Check out the Electromagnetic Spectrum) Once the radar receives the returned signal, it calculates useful information from it such as the time taken for it to be received, the strength of the returned signal, or the change in frequency of the signal.  This information is then translated to reveal useful data: an image, a position or the velocity of your speeding car. Your Basic Radar System: A basic radar system is spilt up into a transmitter, switch, antenna, receiver, data recorder, processor and some sort of output display.  Everything starts with the transmitter as it transmits a high power pulse to a switch which then directs the pulse to be transmitted out an antenna.  Just after the antenna is finished transmitting the pulse, the switch switches control to the receiver which allows the antenna to receive echoed signals.  Once the signals are received the switch then transfers control back to the transmitter to transmit another signal.  The switch may toggle control between the transmitter and the receiver as much as 1000 times per second.             Any received signals from the receiver are then sent to a data recorder for storage on a disk or tape.  Later the data must be processed to be interpreted into something useful which would go on a display. Pulse Width and Bandwidth:             Some radar transmitters do not transmit constant, uninterrupted electromagnetic waves.  Instead, they transmit rhythmic pulses of EM waves with a set amount of time in between each pulse.  The pulse itself would consist of an EM wave of several wavelengths with some dead time after it in which there are no transmissions.  The time between each pulse is called the pulse repetition time (PRT) and the number of pulses transmitted in one second is called the pulse repetition frequency (PRF).  The time taken for each pulse to be transmitted is called the pulse width (PW) or pulse duration.  Typically they can be around 0.1 microseconds long for penetrating radars or 10-50 microseconds long for imaging radars (a microsecond is a millionth of a second).  In math language, the above can be said... PRT = 1 / PRF

Radar used in:

Radar is something that is in use all around us, although it is normally invisible. Air traffic controluses 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 satellitesand space debris ...

• Detect the speed of an object - This is the reason why police use radar.
• Map something - The space shuttle and orbiting satellites use something called Synthetic Aperture Radar to create detailed topographic maps of the surface of planets and moons.

All three of these activities can be accomplished using two things you may be familiar with from everyday life: echo and Doppler shift. These two concepts are easy to understand in the realm of sound because your ears hear echo and Doppler shift every day. Radar makes use of the same techniques using radio waves.

• Detect the presence of an object at a distance - Usually the "something" is moving, like an airplane, but radar can also be used to detect stationary objects buried underground. In some cases, radar can identify an object as well; for example, it can identify the type of aircraft it has detected.

Pics of objects detection......