RADAR

Electronics & Communication Engineering Department
Asansol Engineering College
Kanyapur, Sen Raleigh Road, Asansol 713304, Burdwan, India

Radar stands for ‘RADIO DETECTION AND RANGING’. It is basically an echo ranging system in which electromagnetic energy in the form of high power short duration pulses are sent out at distant targets. After this an echo is received at the transmitting station. This echo is the received signal from the long distant object. The echo is then analyzed to obtain information regarding the location of targets. 

COMPONENTS OF A RADAR SYSTEM:  

It consists of a transmitter and a receiver. Both the elements are connected to a directional antenna through a duplexer. Now what is a duplexer? It is a switching arrangement. It is excited by a small portion of the pulse power generated by the transmitter. The duplexer disconnects the receiver from the antenna and connects the transmitter to the antenna. The function of the antenna is to rotate in order to direct the radiated beam as necessary. When the transmitted pulse is over, the duplexer reconnects the receiver to the antenna. Now the reflected pulses are received and processed at the superheterodyne receiver. The demodulated pulses are then fed to the indicator for display purpose and analysis.

The main function of radar is to provide information on the elevation (vertical direction) and azimuth (horizontal direction) of the antenna, thus the position of the target can be found.

 The distance of the target can be calculated by from total time (t) taken by the pulse to travel to the target and return to its original initial point. Assuming ‘ c ‘ to be the velocity of light  in free space, the distance traversed by pulse is ‘ct’ meters. Now this is 2times the target distance, hence the distance to the target is ‘ct/2’ meters. 

RADAR RANGE EQUATION is d (max) = [{S P (t) G (t) ². λ²}/ (4π) ³ P (min)] ¼ 

d (max) = Maximum range.

λ = Wavelength.

G (t) = Power gain of the antenna relative to the isotropic radiator.

P (t) = Peak value of the transmitted pulsed power.

P (min) = Minimum power that can be detected by the receiver.

S = Effective area of the target. 

Fig.1- BASIC BLOCK DIAGRAM OF THE PULSED RADAR SET

APPLICATIONS OF RADAR: 

Radar finds its applications in various fields like: 

• MILITARY USES: enemy ships can be detected by radar which helps in direct targeting of the enemy ships or even aircrafts. Moreover radar displays are used in bomb ships or in cities at night. We are well aware of the satellites revolving in space used for communication purposes, but do we know that radar placed on a satellite helps in detecting the ballistic missiles.

• IN SUBMARINES: Radars are also used in finding submarines and in directing guided missiles.

• CIVILIAN USES: Useful information about navigations can be obtained from radars. Radar located or fixed in ships can be used to locate marker buoys, other ships, land etc.

• SCIENTIFIC USES:  Map positions of islands can be found out using radars. Furthermore information regarding the distance and motions of different planetary bodies can be obtained with the help of radar.

• OTHER USES: Radars are used in mapping, meteorology, air traffic control at airports providing landing facilities. Radars are also used by police forces for traffic speed control and prosecution of offenders.