Seminar Modern Academy

1. T H E R A D A R
4 1

2. Outline
1. 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 .

3. INTRODUCTION
RADIO DETECTION AND
RANGING
“R A D A R”
3

4. Bats use a basic form of RADAR.
 They send sound waves that
reflect of an object just as
electric RADAR systems do.

5. HISTORY
The 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

6. Radar Frequency Bands

7. Principle of Operation
 Reflection of electromagnetic waves
 Measurement of running time of transmitted pulses

8. Determining Range With Pulse Radar
2
*tc
Range 
c = 3 x 108 m/sec
t is time to receive return
divide by 2 because pulse traveled to object and back

9. 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.

10. Doppler effect theory
• Fd = 2Vr
λ
Fd = doppler shift
Vr = relative velocity of target with respect to radar.

11. A basic Radar System

12. 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."

13. 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.

14. 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

15. Antenna System
15
• 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

16. 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

17. RADAR
PRIMAR
Y
SECOND
ARY
CONTINIOUS
WAVE
PULSE
MODULAT
E
UNMODU-
LATE
MTI
DOPPLE
R

18. 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

19.  Material.
 Shape, Directivity and Orientation.
 Active Cancellation.
 Radar Absorbent Paint.
Stealth Technology

20. 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.

21. 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.

22. 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.

23. 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.

26. Interference
 Noise.
 Clutter.
 Jamming.

27. 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”.

28. 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.

29. PPI Scope

30. 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.

31. 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.

32. • 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

34. FIELDS OF APPLICATION
MILITARY
REMOTE SENSING
AIR TRAFFIC CONTROL
LAW ENFORCEMENT AND HIGHWAY
SECURITY
AIRCRAFT SAFETY AND NAVIGATION
SHIP SAFETY
SPACE
MISCELLANEOUS APPLICATIONS

35. MILITARY
IMPORTANT PART OF AIR DEFENCE SYSTEM,OPERATION
OF OFFENSIVE MISSILES & OTHER WEAPONS
TARGET DETECTION, TARGET TRACKING & WEAPON
CONTROL
TRACKS THE TARGETS, DIRECTS THE WEAPON TO AN
INTERCEPT AND ASSESS THE EFFECTIVENESS OF
ENGAGEMENT
ALSO USED IN AREA, GROUND & AIR SURVEILLANCE.

36. WEATHER OBSERVATION-T.V.REPORTING
PLANETARY OBSERVATION
BELOW GROUND PROBING
MAPPING OF SEA ICE
REMOTE
SENSING

37. USED TO SAFELY CONTROL AIR TRAFFIC IN THE
VICINITY OF THE AIRPORTS AND ENROUTE
GROUND VEHICULAR TRAFFIC & AIRCRAFT
TAXING
MAPPING OF REGIONS OF RAIN IN THE VICINITY
OF AIRPORTS & WEATHER
AIR TRAFFIC CONTROL

38. RADAR IS FOUND ON SHIPS & BOATS FOR
COLLISION AVOIDANCE & TO OBSERVE
NAVIGATION, BUOYS WHEN THE
VISIBILITY IS POOR
SHORE BASED RADARS ARE USED FOR
SURVEILLANCE OF HARBOURS & RIVER
TRAFFIC
SHIP SAFETY

39.  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.

40. Q/A .?