RADAR TECHNOLOGY

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Transmitter
The radar transmitter produces the short duration high-power rf pulses of energy that are into space by the antenna.
Duplexer
The duplexer alternately switches the antenna between the transmitter and receiver so that only one antenna need be used. This switching is necessary because the high-power pulses of the transmitter would destroy the receiver if energy were allowed to enter the receiver.

Receiver
The receivers amplify and demodulate the received RF-signals. The receiver provides video signals on the output.
Radar Antenna
The Antenna transfers the transmitter energy to signals in space with the required distribution and efficiency. This process is applied in an identical way on reception.
Indicator of radar targets
The indicator should present to the observer a continuous, easily understandable, graphic picture of the relative position.


WHAT IS RADAR?
The word “Radar “is an acronym derived from the words Radio Detection And Ranging. It refers to the technique of using radio waves to detect the presence of objects in the atmosphere. Radar was designed shortly before World War II. Its primary purpose was to detect the presence of aircraft. Today, radar is used for a wide array of applications, but primarily to detect precipitation and other meteorological events.



. HISTORY OF RADAR
The history of radar starts with experiments by Heinrich Hertz in the late 19th century that showed that radio waves were reflected by metallic objects. The name radar comes from the acronym RADAR, coined in 1940 by the U.S. Navy .Several inventors, scientists, and engineers contributed to the development of radar .The first to use radio waves to detect "the presence of distant metallic objects" was Christian Hülsmeyer. Before the Second World War developments by the British, the Germans, the French, the Soviets and the Americans led to the modern version of radar.



5.1. TARGETS OF RADAR TECHNOLOGY
5.1.1. TARGET DETECTION
• Radars create an electromagnetic (EM) pulse that is focused by an antenna, and then transmitted through the atmosphere (Figure A).
• Objects in the path of the transmitted EM pulse, called "targets" or "echoes," scatter most of the energy, but some will be reflected back toward the radar (Figure B).
• The receiving antenna (normally also the transmitting antenna) gathers back-scattered radiation and feeds it to a "receiver."
• An EM pulse encountering a target is scattered in all directions. The larger the target, the stronger the scattered signal (Figure C).
• Also, the more targets, the stronger the return signal, that is, the targets combines to produce a stronger signal (Figure D).
• The radar measures the returned signal, generally called the "reflectivity."
• Reflectivity magnitude is related to the number and size of the targets encountered.