RADAR is an object-detection, electronic device that uses ultra-high frequency or microwave part of the radio frequency spectrum to determine the position or range of an object. It can also be used to detect the speed and direction of a moving object. It was secretly developed by many countries during the Second World War. The term RADAR was given by the United States of Navy inn1940.
RADAR sends an electromagnetic pulse, transmitted through the atmosphere. Objects which are called targets in the path of pulse will scatter most of the energy but some will be reflected back to the RADAR. Scattered radiation will go to the receiver. If there are more targets then scattered signals combine to form a stronger signal. The value of range, position, direction, and altitude is measured by these scattered signals.