RADAR RANGE EQUATION PREPARED BY: SAMUEL SIDDHESH MAYUR PRAJNA MAHESH

CONTENTS WHAT IS RADAR? PRINCIPLE OF RADAR HISTORY OF RADAR RADAR RANGE EQUATION THEORY CONCLUSION

WHAT IS RADAR? Radar is basically a means of gathering information about distant objects, or targets , by sending electromagnetic waves at them and analyzing the echoes. It was evolved during the years just before World War 2. At first, it was used as an all weather method of detecting approaching aircraft , and later for many purposes.

PRINCIPLE A radar dish or antenna, sends out pulses of radio waves or microwaves. These waves bounce off any object in their path, and return to the dish, which detects them. The time it takes for the reflected waves to return to the dish enables a computer to calculate how far away the object is, its radial velocity and other characteristics

HISTORY OF RADAR Several inventers, 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, who in 1904 demonstrated the feasibility of detecting the presence of a ship in dense fog.

RADAR RANGE EQUATION EXPLANATION To determine the maximum range of the radar set ,it is necessary to determine the power of the received echoes,& to compare it with the minimum power that the receiver can handle & display satisfactorily. If the transmitted pulsed power is ‘ Pt ’ (peak value) & the antenna is isotropic , then the power density at a distance ‘ r ’ from the antenna will be as given by following Eq.

However, antennas used in RADAR are directional, rather than isotropic However, antennas used in RADAR are directional, rather than isotropic. If Ap is the maximum power gain of the antenna used for transmission , so the power density at the target will be

The power intercepted by the target depends on it’s RADAR cross section , or effective area, If this area is ‘ S ’, the power impinging (impact) on the target will be

The target is not, of course, an antenna ; thus , its radiation may be thought of as omnidirectional. Accordingly, the power density of it’s radiation at the receiving antenna will be

Like the target , the receiving antenna intercepts a portion of the reradiated power , which is proportional to the cross-section area of the receiving antenna. However, it is capture area of the Receiving antenna that is used here,

Eq. no. A

where A0 = capture area of the receiving antenna. If the same antenna is used for both reception and transmission, then maximum power gain is given by

Eq. no. B

substituting Eq. A, B gives Eq. no. C

The maximum range rmax will be obtained when the received power is equal to the minimum receivable power of the receiver, Pmin. substituting this into Eq. C,& making r the subject of the equation ,we have

Eq. no. D

Eq. no. D1

Equations D& D1 represent two convenient forms of the radar equation, simplified to the extent that the minimum receivable power Pmin has not yet been defined. It should also be pointed out that idealized condition have been Employed. Since neither the effects of the ground nor other absorption & interface have been taken into account ,the maximum range in practice is often less than that indicated by the radar range equation.

CONCLUSION RADAR range equation is a basic equation used to find the range of a RADAR.

references WEBSITE: www.Wikipedia.com BOOK NAME: ELECTRONIC COMMUNICATION SYSTEMS [THIRD EDITION]

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