RADAR is an acronym for radio detection and ranging. As the name itself suggests, a RADAR makes use of radio waves to detect and to find the range of the target object. A RADAR was first used in 1942 during the second world war by the US Navy. RADARs are advantageous as they have considerably superior penetration ability. This helps them remain unaffected by extreme weather conditions such as humidity, rain, snow, fog, etc. RADARs can be used flexibly during the daytime as well as during the nighttime. RADARs make use of electromagnetic waves for their operation, which can travel easily through the vacuum. This means that, unlike a SONAR, i.e., Sound Navigation and Ranging, the proper functioning of a RADAR does not require any medium. One of the biggest merits of using a RADAR includes its ability to target, detect, and locate multiple objects at the same time. The limitations of RADAR include its inability to determine optical characteristics such as colour, texture, etc. of the target object and the ineffectiveness to collect data and information about the target objects that are located in the deep sea. Also, the radio wave transmitted by the transmitter of a RADAR is much likely to get interrupted by the other signals present in the environment. The transmission of radio signals by the RADAR should not take place beyond the ionosphere. In such a case, the signal does not hit the target and directly gets deflected back to the earth. The operator of the RADAR needs to possess proper training and skills to analyse the data. A RADAR can be easily used for long ranges. The applications of a RADAR can be broadly categorized into two categories, namely, civilian applications and military applications. The civilian applications of a RADAR include vehicle speed detection RADARs, satellite surveillance devices, altimeters, navigation instruments, etc. Similarly, the RADAR can be used for a number of military applications such as object detection of enemy targets, locating landmines and submarines, shooting enemy ships and aircraft, dropping bombs at specific locations, directing guided missiles, etc. A RADAR finds its prime application in aeroplane blind landers to provide proper landing guidance to the pilot under extreme weather conditions, poor visibility, and during the nighttime to ensure a safe landing.
Working Principle of a RADAR
A RADAR typically works on the principle of tracing back a portion of the transmitted radio wave that gets reflected upon striking the surface of a rigid object. A radio wave is a form of electromagnetic wave that has a wavelength ranging from 30 cm to thousands of meters. The frequency level of radio waves lies between 3 hertz to 1 gigahertz. The radio bursts transmitted by the transmitter of a RADAR tend to travel towards and away from the target object at the speed of light; therefore, appear to exist for an extremely short duration of time. The portion of the radio wave that gets reflected back after hitting the target is known as echo. This echo signal contains the information required to determine the shape, size, location, angle, range, velocity, and various other characteristics of the target object. In simple words, the entire operation of a RADAR depends on the analysis of the reflected wave. A RADAR has the ability to detect the position and characteristics of static as well as moving objects. It can also tell whether the target object is moving away from or towards the RADAR. Usually, in a RADAR set, the transmitter antenna itself acts as the receiver antenna. The transmitted signal tends to lose a significant amount of energy after striking the target object, hence the reflected signal gets attenuated in the process and is required to be amplified after the reception. The amplification of the reflected signal is done up to several million times. The retraced signal after processing is further used to deflect the electron beam in the cathode ray tube. This causes a light indicator to appear on the display unit that points towards the direction of the target object. The display of a RADAR consists of a fluorescence layer that enables the glow of light to stay for a longer duration and change only after the next echo signal is received. The coordinates and the distance of the target get displayed directly with the help of the indicator tube. The angle at which the target moves towards or away from an object is determined by estimating the direction from which the reflected signal is obtained. The angular value of the target can be expressed by two components, namely azimuth angle and elevation angle. The azimuth angle is measured along the horizontal plane, while the elevation angle is measured along the vertical axis or the vertical plane.