T H E R A D A R

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Outline1. Introduction to radar .2. History .3. Basic Radar Principles .4. Components Of Radar System .5. Types Of Radar .6. Factors Effects on Radar .7. Stealth Technology .8. Advantages & dis-Advantages .9. Application .10. Conclusion .

INTRODUCTION

RADIO DETECTION AND RANGING

“R A D A R”

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WORKING PROCESS OF RADAR

Bats use a basic form of RADAR.

They send sound waves that reflect of an object just as electric RADAR systems do.

HISTORYThe history of RADAR starts with experiments by Heinrich Hertz in the late 19th century.The first form of RADAR created by humans was the telemobilescope.

Telemobilescope ( The first form of RADAR )

It was mainly used to detect ships to avoid collisions

Radar Frequency Bands

Principle of Operation

Reflection of electromagnetic waves

Measurement of running time of transmitted pulses

Determining Range With Pulse Radar

2*tcRange

c = 3 x 108 m/sec

t is time to receive return

divide by 2 because pulse traveled to object and back

Doppler Effect• that the Doppler effect is the change in frequency

that occurs when a source and a target are in relative motion.

• The Doppler affect can be used in a CW radar in order to determine velocity.

Doppler effect theory• Fd = 2Vr

λFd = doppler shiftVr = relative velocity of target with respect to radar.

A basic Radar System

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 combine

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.

Duplexer• The duplexer is a waveguide switch• It passes the transmitted high-power pulses to the

antenna and the received echoes from the antenna to the receiver

• Duplexer switches automatically based on the timing control signal

Antenna System

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• Radiation from a directional source• The energy is focused in a given

directions• This allows the energy to travel

further, hence a gain, G, compared to the isotropic source

Antenna System• Coastal Surveillance and Vessel Traffic System radars are

usually fan or inverse-cosecant-squared beams

fan beam pattern

Inverse-cosecant-square beam pattern

TYPES OF RADAR

RADAR

PRIMARY

SECONDARY

CONTINIOUS

WAVEPULSE

MODULATE

UNMODU-LATE MTI DOPPL

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Factors That Affect Radar Performance• Signal Reception• Receiver Bandwidth• Pulse Shape• Power Relation• Beam Width• Pulse Repetition Frequency• Antenna Gain• Radar Cross Section of

Target

• Signal-to-noise ratio• Receiver Sensitivity• Pulse Compression• Scan Rate

• Mechanical• Electronic

• Carrier Frequency• Antenna aperture

Material.

Shape, Directivity and Orientation.

Active Cancellation.

Radar Absorbent Paint.

Stealth Technology

Material

Materials such as metal are strongly radar reflective and tend to produce strong signals. Wood and cloth (such as portions of planes and balloons used to be commonly made) or plastic and fibreglass are less reflective or indeed transparent to RADAR making them suitable for radomes. Even a very thin layer of metal can make an object strongly radar reflective .

Submarines have extensive usage of rubber mountings to isolate and avoid mechanical noises that could reveal locations to underwater passive sonar arrays.

Shape, Directivity and Orientation

The surfaces of the F-117A are designed to be flat and very angled. This has the effect that RADAR will be incident at a large angle (to the normal ray) that will then bounce off at a similarly high reflected angle; it is forward-scattered . The edges are sharp to prevent there being rounded surfaces. Rounded

surfaces will often have some portion of the surface normal to the RADAR source. As any ray incident along the normal will reflect back along the normal this will make for a strong reflected signal .

With purpose shaping, the shape of the target’s reflecting surfaces is designed such that they reflect energy away from the source .

Active Cancellation

With active cancellation, the target generates a radar signal equal in intensity but opposite in phase to the predicted reflection of an incident radar signal . This creates destructive interference between the reflected and generated

signals,resulting in reduced RCS .

Radar Absorbent Paint

The SR-71 Blackbird and other planes were painted with a special "iron ball paint“. This consisted of small metallic-coated balls. RADAR energy is converted to heat rather than being reflected.

One of the most commonly known types of RAM is iron ball paint. It contains tiny spheres coated with carbonyl iron or ferrite. Radar waves induce molecular oscillations from the alternating magnetic field in this paint, which leads to conversion of the radar energy into heat. The heat is then transferred to the aircraft and dissipated.

Interference

Noise.

Clutter.

Jamming.

Radiation Hazards and Precaution

SEA CLUTTER Sea clutter echoes are caused by reflection of the

radar pulse against the sea waves. The reflection is specular and conditions for the pulse to return to the scanner are favorable near the ship. At longer ranges the beam will be deflected away from the ship.

Marine radars are equipped with rejection systems to minimize the effect of sea clutter. This control is often named “Anti Clutter Sea” or “STC”.

Noise Signal noise is an internal source of random variations in the signal, which is

generated by all electronic components. Noise typically appears as random variations superimposed on the desired echo signal received in the radar receiver. The lower the

power of the desired signal, the more difficult it is to discern it from the noise ( similar to trying to hear a whisper while standing near a busy road .)

Noise figure is a measure of the noise produced by a receiver compared to an ideal receiver, and this needs to be minimized.

Noise is also generated by external sources, most importantly the natural thermal radiation of the background scene surrounding the target of interest.

There will be also flicker noise due to electrons transit, but depending on 1/f, will be much lower than thermal noise when the frequency is high .

PPI Scope

Jamming Radar jamming refers to radio frequency signals originating from

sources outside the radar, transmitting in the radar's frequency and thereby masking targets of interest. Jamming may be intentional, as with an electronic warfare (EW) tactic, or unintentional, as with friendly forces operating equipment that transmits using the same frequency range. Jamming is considered an active interference source, since it is initiated by elements outside the radar and in general unrelated to the radar signals.

ADVANTAGES OF MILITARY RADARS • All-weather day and night capability.

• Multiple target handling and engagement capability.

• Short and fast reaction time between target detection and ready to fire moment.

• Easy to operate and hence low manning requirements and stress reduction under severe conditions

• .• Highly mobile system, to be used in all kind of terrain

• Flexible weapon integration, and unlimited number of single air defence weapons can be provided with target data.

• Time - Radar can take up to 2 seconds to lock on

• Radar has wide beam spread (50 ft diameter over 200 ft range).

• Cannot track if deceleration is greater than one mph/second.

• Large targets close to radar can saturate receiver.

• Hand-held modulation can falsify readings.

DISADVANTAGES

Application

FIELDS OF APPLICATION

MILITARYREMOTE SENSINGAIR TRAFFIC CONTROLLAW ENFORCEMENT AND HIGHWAY SECURITYAIRCRAFT SAFETY AND NAVIGATIONSHIP SAFETYSPACEMISCELLANEOUS APPLICATIONS

MILITARY

IMPORTANT PART OF AIR DEFENCE SYSTEM,OPERATION OF OFFENSIVE MISSILES & OTHER WEAPONSTARGET DETECTION, TARGET TRACKING & WEAPON CONTROLTRACKS THE TARGETS, DIRECTS THE WEAPON TO AN INTERCEPT AND ASSESS THE EFFECTIVENESS OF ENGAGEMENTALSO USED IN AREA, GROUND & AIR SURVEILLANCE.

WEATHER OBSERVATION-T.V.REPORTINGPLANETARY OBSERVATIONBELOW GROUND PROBINGMAPPING OF SEA ICE

REMOTE SENSING

USED TO SAFELY CONTROL AIR TRAFFIC IN THE VICINITY OF THE AIRPORTS AND ENROUTEGROUND VEHICULAR TRAFFIC & AIRCRAFT TAXINGMAPPING OF REGIONS OF RAIN IN THE VICINITY OF AIRPORTS & WEATHER

AIR TRAFFIC CONTROL

RADAR IS FOUND ON SHIPS & BOATS FOR COLLISION AVOIDANCE & TO OBSERVE NAVIGATION, BUOYS WHEN THE VISIBILITY IS POORSHORE BASED RADARS ARE USED FOR SURVEILLANCE OF HARBOURS & RIVER TRAFFIC

SHIP SAFETY

CONCLUSION

RADAR is used to find velocity, range and position of the object.

LIDER is Advanced type of RADAR which uses visible light from LASER

Technology will continue to grow, and RADAR will advance with it.

Growth of RADAR technologies will be accompanied by a wider variety of applications.

RADAR in the future will most likely be as common as cell phone applications are today.

Q/A .?