Study of Radar System + Bharat Electronics Limited

1. Training report on
Industrial training at
On the topic:-
STUDY OF RADAR SYSTEM
Submitted to:-
Submitted by:-
Atul Sharma, B.Tech IV year, ECE
Maharaja Agrasen Institute Of Technology,
GGSIPU
Under:- Mr. Aman Vohra
Start Date for Internship:-June 16th 2014
End Date for Internship:-July 26th 2014
1

2. Preface
This report documents the work done during the summer training at
Bharat Electronics limited, Ghaziabad, Uttar Pradesh under the
guidance of Mr. Aman Vohra . The report first shall give the
overview of tasks performed during the period of training .The
technical details about the RADAR and its various applications and
the conclusion drawn out of it.
Report shall also elaborate about the future scope of the Radar
Technology.
I have tried my best to keep the report simple yet technically correct. I
hope I succeed in my attempt.
2
Atul Sharma

3. Acknowledgement
On the very outset of this report, I would like to extend my sincere &
heartfelt obligation towards all the personages who have helped me in
this endeavour. Without their active guidance, help, cooperation &
encouragement, I would not have made headway in the project.
First and foremost, I would like to express my sincere gratitude to my
project guide, Mr. Aman Vohra.
I was privileged to experience a sustained enthusiastic and involved
interest from his side. This fuelled my enthusiasm even further and
encouraged me to boldly step into what was a totally dark and
unexplored expanse before me.
I would also like to thank Mr. Mohit Saxena who, instead of his busy
schedule, always guided me in right direction.
I extend my gratitude to Maharaja Agrasen Institute Of Technology
for giving me this opportunity.
3
Thank You
Atul Sharma

4. Table of Content
Introduction........................................................................................06
Historical Overview............................................................................07
Radar Basic Principles........................................................................09
Distance-determination............................................................10
Direction-determination...........................................................11
Maximum Unambiguous Range..............................................13
Minimal Measuring Range......................................................14
Radar Frequency Bands.....................................................................15
Waves and Frequency Ranges.................................................15
Free space Radar equations................................................................17
Radar Coverage..................................................................................19
Cone of Silence........................................................................19
Low-altitude Coverage.............................................................20
Classification of Radar systems.........................................................21
Classification Depending Upon Technology..........................23
Primary Radar..............................................................23
Secondary Radar..........................................................23
Continuous Wave Radar..............................................24
Pulse Radar..................................................................26
4

5. Classification on the basis of design........................................27
Air-defence Radars.....................................................27
Air traffic control (ATC)............................................28
Some Radar Sets................................................................................29
3-D Surveillance Radar (ROHINI).........................................29
Low Level Light-Weight Radar (ASHLESHA).....................30
Low Level Light-Weight Radar (BHARANI)........................31
Indra II....................................................................................32
3-D Tactical Control Radar....................................................33
Tactical Control Radar...........................................................34
Radar Devices...................................................................................35
Radar Antenna........................................................................35
Parabolic Antenna.....................................................35
Cassegrain Antenna...................................................36
Slot Antenna..............................................................36
Radar Transmitter...................................................................37
Radar Receiver........................................................................37
Radar Display..........................................................................37
Radar A- Scope...........................................................38
Radar B-Scopes...........................................................39
Plan-Position Indicator................................................40
Future Research..................................................................................41
Conclusion.........................................................................................42
Bibliography......................................................................................43
5

6. INTRODUCTION
RADAR is acronym for Radio Detection and Ranging. Today, the technology is
so common that the word has become Standard English noun. The development
of RADAR accelerated and spread in middle and late 1930s with first successful
demonstration in 1936. It uses electromagnetic waves in microwave region to
detect location, height, intensity and movements of targets. It operates by
radiating energy into space and detecting the echo signals reflected from an
object, or target. The reflected energy that is reflected to radar not only indicates
the presence of target, but by comparing the received echo signals with the
signals that were transmitted its location can be determined along with the other
target related information.
Radar is an active device. It utilizes its own radio energy to detect and track the
target. It does not depend on energy radiated by the target itself. The ability to
detect a target at great distances and to locate its position with high accuracy are
two of the chief attributes of radar.
Earlier radar development was driven by military necessities. But, radar now it
enjoys wide range of application. One of the most common is the police traffic
radar used for enforcing speed limits. Another is weather radar. Other most
famous application is air traffic control system.
6

7. HISTORICAL OVERVIEW
7
Neither a single nation nor a single
person is able to say, that he (or it) is
the inventor of the radar method.
One must look at the “Radar” than
an accumulation of many
developments and improvements
earlier, which scientists of several
nations parallel made share. There
are nevertheless some milestones
with the discovery of important
basic knowledge and important
inventions:
1865
The World War II RADAR,
’Wurzberg Rise’
The English physicist James Clerk
Maxwell developed his electro-magnetic
light theory (Description
of the electro-magnetic waves and
her propagation)
1886 The German physicist Heinrich
Rudolf Hertz discovers the electro-magnetic
waves and proves the
theory of Maxwell with that.
1904 The German high frequency
engineer Christian Hülsmeyer
invents the “Telemobiloskop” to the
traffic supervision on the water. He
measures the running time of
electro-magnetic waves to a metal
object (ship) and back. A calculation
of the distance is thus possible. This
is the first practical radar test.
Hülsmeyer registers his invention to
the patent in Germany and in the
United Kingdom.

8. 1917 The French engineer Lucien Lévy
invents the super-heterodyne
receiver. He uses as first the
denomination “Intermediate
Frequency”, and alludes the
possibility of double heterodyning.
1921
The invention of the Magnetron as
an efficient transmitting tube by the
US-American physicist Albert
Wallace Hull
1922
The American electrical engineers
Albert H. Taylor and Leo C.
Young of the Naval Research
Laboratory (USA) locate a wooden
ship for the first time.
1930
Lawrence A. Hyland (also of the
Naval Research Laboratory), locates
an aircraft for the first time.
1931
A ship is equipped with radar. As
antennae are used parabolic dishes
with horn radiators.
1936 The development of the Klystron by
the technicians George F. Metcalf
and William C. Hahn, both from
General Electric. This will be an
important component in radar units
as an amplifier or an oscillator tube.
1940
Different radar equipments are
developed in the USA, Russia,
Germany, France and Japan.
8

9. RADAR BASIC PRINCIPLE
9
The electronic principle on which
radar operates is very similar to the
principle of sound-wave reflection. If
you shout in the direction of a sound-reflecting
object (like a rocky canyon
or cave), you will hear an echo. If
you know the speed of sound in air,
you can then estimate the distance
and general direction of the object.
The time required for an echo to
return can be roughly converted to
distance if the speed of sound is
known. RADAR PRINCIPAL
Radar uses electromagnetic energy pulses. The radio-frequency (RF) energy is
transmitted to and reflected from the reflecting object. A small portion of the
reflected energy returns to the radar set. This returned energy is called an
ECHO, just as it is in sound terminology. Radar sets use the echo to determine
the direction and distance of the reflecting object. The word radar is a
contraction of
RAdio Detecting And Ranging
As implied by this contraction, radars are used to detect the presence of an aim
(as object of detection) and to determine its location. The contraction implies
that the quantity measured is range. While this is correct, modern radars are also
used to measure range and angle. The following figure shows the operating
principle of primary radar. The radar antenna illuminates the target with a
microwave signal, which is then reflected and picked up by a receiving device.
The electrical signal picked up by the receiving antenna is called echo or return.
The radar signal is generated by a powerful transmitter and received by a highly
sensitive receiver.

10. 10
Distance-determination
The radar transmits a short
radio pulse with very high
pulse power. This pulse is
focused in one direction only
by the directivity of the
antenna, and propagates in
this given direction with the
speed of light.
If in this direction is an
obstacle, for example an
airplane, Runtime measurement by radar
part of the energy of the pulse is scattered in all directions. A very small portion
is also reflected back to the radar. The radar antenna receives this energy and
the radar evaluates the contained information.
The distance we can measure with a simple oscilloscope. On the oscilloscope
moves synchronously with the transmitted pulse a luminous point and leaves a
trail. The deflection starts with the transmitter pulse. The luminescent spot
moves to scale on the oscilloscope with the radio wave. At this moment, in
which the antenna receives the echo pulse, this pulse is also shown on the
oscilloscope. The distance between the two shown pulses on the oscilloscope is
a measure of the distance of the aircraft.
Since the propagation of radio waves happens at constant speed (the speed of
light c0) this distance is determined from the runtime of the high-frequency
transmitted signal. The actual range of a target from the radar is known as slant
range. Slant range is the line of sight distance between the radar and the object
illuminated. While ground range is the horizontal distance between the emitter
and its target and its calculation requires knowledge of the target's elevation.
Since the waves travel to a target and back, the round trip time is dividing by
two in order to obtain the time the wave took to reach the target. Therefore the
following formula arises for the slant range:
R =
c0· t where:
c0 = speed of light = 3·108 m/s
t = measured running time [s]
R = slant range antenna
2
The distances are expressed in kilometre or nautical miles (1 NM = 1.852 km).

11. 11
Derivation of the equation
Range is the distance from the radar site to the target measured along the line of
sight.
v =
S
t
c0 =
2·R
t
The factor of two in the equation comes from the observation that the radar
pulse must travel to the target and back before detection, or twice the range.
R =
c0·t
in meters
2
Where c0= 3·108 m/s, is the speed of light at which all electromagnetic waves
propagate.
If the respective running time t is known, then the distance R between a target
and the radar set can be calculated by using this equation.
Direction-determination
The angular determination of the target is determined by the directivity of the
antenna. Directivity, sometimes known
as the directive gain, is the ability of the
antenna to concentrate the transmitted
energy in a particular direction. An
antenna with high directivity is also
called a directive antenna. By measuring
the direction in which the antenna is
pointing when the echo is received, both
the azimuth and elevation angles from
the radar to the object or target can be
determined. Direction-determination (bearing)

12. The accuracy of angular measurement is determined by the directivity, which is
a function of the size of the antenna.
Radar units usually work with very high frequencies. Reasons for this are:
 Quasi-optically propagation of these waves.
 High resolution (the smaller the wavelength, the smaller the objects the
12
radar is able to detect).
 Higher the frequency, smaller the antenna size at the same gain.
The True Bearing (referenced to true north) of a radar target is the angle
between true north and a line pointed directly at the target. This angle is
measured in the horizontal plane and in a clockwise direction from true north.
Variation of echo signal strength
The antennas of most radar systems are designed to radiate energy in a one-directional
lobe or beam that can be moved in bearing simply by moving the
antenna. As you can see, the shape of the beam is such that the echo signal
strength varies in amplitude as the antenna beam moves across the target. In
actual practice, search radar antennas move continuously; the point of
maximum echo, determined by the detection circuitry or visually by the
operator, is when the beam points direct at the target. Weapons-control and
guidance radar systems are positioned to the point of maximum signal return
and maintained at that position either manually or by automatic tracking
circuits.
In order to have an exact determination of the bearing angle, a survey of the
north direction is necessary. Therefore, older radar sets must expensively be
surveyed either with a compass or with help of known trigonometrically points.
More modern radar sets take on this task and with help of the GPS satellites
determine the north direction independently.

13. 13
Maximum Unambiguous Range
Second-sweep echo in a distance of 400 km
It becomes obvious that we cannot send out another pulse until a time window
has passed, in which we expect to see a return echo. The maximum measuring
distance Rmax of a radar unit isn't orientated only at the value determined in the
radar equation but also on the duration of the receiving time.
The radar timing system must be reset to zero each time a pulse is radiated. This
is to ensure that the range detected is measured from time zero each time. Echo
signals arriving after the reception time are placed either into the
 Following transmit time where they remain unconsidered since the radar
equipment isn't ready to receive during this time, or
 Into the following reception time where they lead to measuring failures
(ambiguous returns).
The maximum range at which a target can be located so as to guarantee that the
leading edge of the received backscatter from that target is received before
transmission begins for the next pulse. This range is called maximum
unambiguous range or the first range ambiguity. The pulse-repetition
frequency (PRF) determines this maximum unambiguous range of given radar
before ambiguities start to occur. This range can be determined by using the
following equations:
Rmax =
c0 · ( PRT - PW )
2
Where c0 is the speed of light with 3·108 m/s. The pulse width (PW) in these
equations indicates that the complete echo impulse must be received. The pulse

14. repetition time (PRT) of the radar is important when determining the maximum
range because target return-times that exceed the PRT of the radar system
appear at incorrect locations (ranges) on the radar screen. Returns that appear at
these incorrect ranges are referred as ambiguous returns or second-sweep
echoes.
14
Minimal Measuring Range
The Radars “blind range”
Monostatic pulse radar sets use the same antenna for transmitting and receiving.
During the transmitting time the radar cannot receive: the radar receiver is
switched off using an electronic switch, called duplexer. The minimal
measuring range Rmin (“blind range”) is the minimum distance which the target
must have to be detected. Therein, it is necessary that the transmitting pulse
leaves the antenna completely and the radar unit must switch on the receiver.
The transmitting time τ and the recovery time trecovery should are as short as
possible, if targets shall be detected in the local area.
Rmin =
c0·(τ + trecovery)
2

15. RADAR FREQUENCY BANDS
15
Waves and Frequency Ranges
The spectrum of the electric magnetic waves shows frequencies up to 1024 Hz.
This very large complete range is subdivided because of different physical
qualities in different subranges.
The division of the frequencies to the different ranges was competed on criteria
formerly, which arose historically and a new division of the wavebands which is
used internationally is out-dated and arose so in the meantime. The traditional
waveband name is partly still used in the literature,
Spectrum of EM waves
Since without that the correct frequency is known, a transformation isn't always
possible into the new wavebands. Often in the manufacturers documents are
published the traditional wavebands. Some radars and its frequency band Radar
systems work in a wide band of transmitted frequencies. The higher the
frequency of a radar system, the more it is affected by weather conditions such

16. as rain or clouds. But the higher the transmitted frequency, the better is the
accuracy of the radar system.
The figure shows, how the frequency bands are used .
some radars and its frequency band
16

17. FREE RADAR SPACE EQUATION
The radar range equation relates the range of radar to the characteristics of the
transmitter, receiver, antenna, target and the medium. Free space actually means
that there are no obstacles between radar antenna and the target. Also the free
space medium is transparent and homogenous with respect to the refractive
index at radar frequency.
If the power of a radar transmitter is denoted by Pt and if an isotropic antenna
(one which radiates uniformly in all the directions) then the power density at a
distance R from the radar is equal to the transmitted power divided by the
surface area of sphere of radius R i.e. power density at a distance R from the
isotropic source,
= Pt / 4ПR2 watts/m2
Radar usually employs directive antennas to direct the transmitted power Pt into
one particular direction. The gain G of an antenna is a measure of the increased
power radiated in the direction of the target as compared with the power that
would have been radiated from an isotropic antenna.
Power density at a distance R from directive antenna of power gain
= Pt.G / 4ПR2 watts/m2
The target intercepts the portion of transmitted power and radiates it in various
directions. A measure of the incident power intercepted by the target and
reradiated back in the direction of radar is denoted as the radar cross-section of
the target (б).
The total power intercepted by a target having an area ‘б’ is,
= (Pt .G / 4П R2).б watts
Where б is also defined as the area of the target as seen by the radar. It has units
of area in m2. б is a characteristic of a particular target and is a measure of its
size and shape.
The power density of echo signal at the radar station is
= (Pt .G.б / 4ПR2) . (1/4ПR2)
= Pt .G.б/ (4ПR2)2 watts
The radar antenna captures the portion of the echo power, if the effective area
of the receiving antenna is denoted by Ae, the power Pr received by the radar is
given by,
Pr = Pt .G.б.Ae / (4ПR2)2 watts
17

18. Maximum radar range is the distance beyond which the target cannot be
detected. It occurs when the received echo signal power Pr, just equals the
minimum detectable signal (Smin).
When Pr = Smin, R = Rmax
We get,
Smin = Pt .G.б.Ae / (4П)2 R4
max
Rmax = [Pt .G.б.Ae /(4П)2Smin]1/4
18
From the antenna theory, we know that
G = 4ПAe / λ2
Where λ= wavelength of the radiated energy,
Ae = effective area of receiving antenna,
G = transmitter gain
Since radar generally use the same antenna for both transmitter and receiver, the
above expression for G can be substituted in Rmax relation. Then,
Rmax = [Pt .G.б.Ae / (4П)2Smin]1/4
Rmax = [Pt .Ae
2.б / 4П.λ2Smin]1/4
Also, Ae = G.λ2 / 4П,
Rmax = [Pt(Gλ2/4П)2б / 4Пλ2Smin]1/4
Rmax = [Pt .G.λ2 .б / (4П)2 Smin]1/4
These are the two alternate form of maximum radar range equation.

19. 19
RADAR COVERAGE
The radar coverage describes area controlled by radar or radar network
airspace. In a two-dimensional radar is often used an antenna with a cosecant
square pattern. Its main beam direction forms a vertical rectangle with rounded
corners, which rotates about a vertical axis. Thus arises on the radar site a room
with the geometry of a flat cylinder within which the radar can locate an aerial
target. At an Air Surveillance Radar (ASR) (or referred to Terminal Area
Radar), this cylinder has a diameter of about 120 NM (220 km) and a height of
about 10,000 feet (or 3,000 m)
Cone of Silence
Radar is not designed to detect aircraft directly above the radar antenna. This
gap is known as the cone of silence. This gap or cone of silence is the inverted
cone mapped out by the rotating antenna as a result of the antenna back angle
being less than 90 degrees. Hence, the back angle is an important antenna
parameter. If the back angle is shallow then aircraft will fall outside radar cover
as they over-fly the
radar site. By most
radars the actual radius
of the cone of silence is
the double of the targets
height. This means, a
target in a height of
10,000 feet (or 3,000 m)
enters the cone of
silence in a range of 3¼
Radar coverage, located in middle of cone of silence
NM (6,000 m). Aircraft flying in a radar's cone of silence may, however, be
detected by another, or several other radar sites a hundred or so miles away due
to their overlapping coverage.

20. 20
Low-altitude Coverage
The flat cylinder has a relatively smooth lower surface in flat terrain. A
curvature of the outer edges upwards is in the order of half a degree. The low-altitude
coverage is limited by the shadow formed by the earth's curvature.
Uneven terrain such as hills or even mountains and valleys by shading also has
an impact on the size of the dead zone. Also this dead zone can be covered by
another radar. Despite a large number of organized in a radar network radar, a
space will always remain in extremely low altitude at which an
Vertical overlap of the radar coverage areas, above: a typical case of air defence, below a
typical case of air traffic control
aircraft can fly below the radar. In practice, however, this is for the pilot not as
easy as it must know exactly where to fly for to remain as far away from each
radar. In order to keep this lower limit as low as possible, but a very dense
network of radars must already be deployed. As you can imagine, countries in
mountainous regions have problems to establish a complete area with full radar
coverage. For the requirements of national defence, a number of smaller mobile
radar sets (as so-called Gap-filler) are established exactly in such gaps when
needed. Depending on the task, such overlap is done according to different
principles. For the air surveillance on behalf of the national defence a complete
radar coverage must be organized down to a height, for example, of 100 m. In
crisis or defence case that needs to be lowered even further. However, an
overlap to the cones of silence is not necessary.

21. CLASSIFICATION OF RADAR SYSTEMS
Depending on the desired information, radar sets must have different qualities
and technologies. One reason for these different qualities and techniques
radar sets are classified in
Classification of radar sets
Imaging Radar / Non-Imaging Radar
An Imaging Radar forms a picture of the observed object or area. Imaging
radars have been used to map the Earth, other planets, asteroids, other celestial
objects and to categorize targets for military systems.
Typically implementations of a Non-Imaging Radar system are speed gauges
and radar altimeters. These are also called scatterometers since they measure the
scattering properties of the object or region being observed. Non-Imaging
Secondary Radar applications are immobilizer systems in some recent private
cars.
21
Primary Radar
A Primary Radar transmits high-frequency signals which are reflected at targets.
The arisen echoes are received and evaluated. This means, unlike secondary
radar sets a primary radar set receive its own emitted signals as an echo again.
Secondary Radar
At these radar sets the airplane must have a transponder (transmitting
responder) on board and this transponder responds to interrogation by

22. transmitting a coded reply signal. This response can contain much more
information, than a primary radar set is able to acquire (E.g. an altitude, an
identification code or also any technical problems on board such as a radio
contact loss).
22
Pulsed Radars
Pulse radar sets transmit a high-frequency impulse signal of high power. After
this impulse signal, a longer break follows in which the echoes can be received,
before a new transmitted signal is sent out. Direction, distance and sometimes if
necessary the height or altitude of the target can be determined from the
measured antenna position and propagation time of the pulse-signal.
Continuous- Wave Radar
CW radar sets transmit a high-frequency signal continuously. The echo signal is
received and processed. The receiver need not to be mounted at the same place
as the transmitter. Every firm civil radio transmitter can work as a radar
transmitter at the same time, if a remote receiver compares the propagation
times of the direct signal with the reflected one. Tests are known that the correct
location of an airplane can be calculated from the evaluation of the signals by
three different television stations.
Unmodulated CW- Radar
The transmitted signal of these equipments is constant in amplitude and
frequency. These equipment is specialized in speed measuring. Distances
cannot be measured. E.g. they are used as speed gauges for police. Newest
equipments work in the laser frequency range and measure not only the speed.
Modulated CW- Radar
The transmitted signal is constant in the amplitude but modulated in the
frequency. This one gets possible after the principle of the propagation time
measurement with that again. It is an advantage of this equipment that an
evaluation is carried out without reception break and the measurement result is
therefore continuously available. These radar sets are used where the measuring
distance isn't too large and it's necessary a continuous measuring (e.g. an
altitude measuring in airplanes or as weather radar).
A similar principle is also used by radar sets whose transmitting impulse is too
long to get a well distance resolution. Often this equipment modulate its
transmitting pulse to obtain a distance resolution within the transmitting pulse
with the help of the pulse compression.

23. Classification Depending Upon Technology
23
Primary Radar
The following figure shows the operating principle of a primary radar set. The
radar antenna illuminates the target with a microwave signal, which is then
reflected and picked up by a receiving device. The electrical signal picked up by
the receiving antenna is called echo or return. The radar signal is generated by a
powerful transmitter and received by a highly sensitive receiver.
Block diagram of a primary radar
All targets produce a diffuse reflection i.e. it is reflected in a wide number of
directions. The reflected signal is also called scattering. Backscatter is the term
given to reflections in the opposite direction to the incident rays.
Radar signals can be displayed on the traditional plan position indicator (PPI) or
other more advanced radar display systems. A PPI has a rotating vector with the
radar at the origin, which indicates the pointing direction of the antenna and
hence the bearing of targets.
Secondary Radar
Radar was born in the due to the pressure of war. The need to detect “hostile”
aircraft led to a vast investment in intellect and money to develop RADAR.

24. 24
Classical Radar (now called Primary
Radar) by definition is a non co-operative
technology i.e. it needs no co-operation
from the “Target” being
detected. Why do we need a different
system then? As well as seeing “hostile”
aircraft it soon became apparent that
Radar was a good tool to see friendly
aircraft and hence control and direct
them. Large Vertical Aperture Antenna
As well as seeing “hostile” aircraft it soon became apparent that Radar was a
good tool to see friendly aircraft and hence control and direct them. If the
“friendly” aircraft is fitted with a transponder (transmitting responder), then
it sends a strong signal back as an “echo”. An active also encoded response
signal which is returned to the radar set then is generated in the transponder.
This proved very useful for the military in seeing their own aircraft clearly. In
this response can be contained much more information, as a primary radar unit
is able to acquire.
CONTINUOUS WAVE RADAR:
Continuous wave radars continuously transmit a high-frequency signal and the
reflected energy is also received and processed continuously. These radars have
to ensure that the transmitted energy doesn’t leak into the receiver (feedback
connection). CW radars measures radial velocity of the target using Doppler
Effect. If there is relative motion between the radar and the target, the shift in
carrier frequency (Doppler shift) of the reflected wave becomes a measure of
targets relative velocity. The block diagram of continuous wave radar is shown
Block diagram of continuous wave radar

25. The transmitter generates a continuous oscillations of frequency fo which is
radiated by radar antenna. A portion of this radiated energy is intercepted by
target and reradiated energy is collected by the receiver antenna. If the target is
moving with the velocity Vr relative to the radar, the received signal will be
shifted in frequency from the transmitted frequency fo by the amount fd. The
plus sign for an approaching target and minus sign for a receding target. The
received echo signal (fo±fd) enters the radar via the antenna and is mixed in a
detector mixer with a portion of a transmitter signal fo to produce the Doppler
frequency fd. The purpose of using a beat frequency amplifier is to eliminate
echo from stationary targets and to amplify the Doppler echo signal to a level
where it can operate an indicating device such as frequency meter.
ADVANTAGES:
1) It uses low transmitting power, low power consumption.
2) It has simple circuitry and it is small in size.
3) Unlike pulse radar CW radar is able to detect an aircraft inspite of fixed
objects.
DISADVANTAGES:
1) Practical application of CW radar is limited by the fact that several targets at
a given bearing tend to cause confusion.
2) Range discrimination can be achieved only by introducing very costly
complex circuitry.
3) It is not capable of indicating the range of target and can show only its
velocity.
25
CW RADARS TYPES
Unmodulated
An example of unmodulated CW radar is speed gauges used by the police. The
transmitted signal of these equipments is constant in amplitude and frequency.
CW radar transmitting unmodulated power can measure the speed only by using
the Doppler-effect. It cannot measure a range and it cannot differ between two
reflecting objects.
Modulated
Unmodulated CW radars have the disadvantage that they cannot measure range,
because run time measurements is not possible (and necessary) in unmodulated
CW-radars. This is achieved in modulated CW radars using the frequency
shifting method. In this method, a signal that constantly changes in frequency

26. around a fixed reference is used to detect stationary objects. Frequency is swept
repeatedly between two frequencies. On examining the received reflected
frequencies (and with the knowledge of the transmitted frequency), range
calculation can be done.
26
Pulse Radar
Pulse radar sets transmit a high-frequency Impulse signal of high power. After
this impulse signal, a longer break follows in which the echoes can be received,
before a new transmitted signal is sent out. Direction, distance and sometimes if
necessary the height or altitude of the target can be determined from the
measured antenna position and propagation time of the pulse-signal.
A monopulse secondary surveillance radar antenna (looks like a lattice fence)
mounted on top of an antenna of a primary radar (parabolic reflector)
These classically radar sets transmit a very short pulse (to get a good range
resolution) with an extremely high pulse-power (to get a good maximum range).
Pulse Radar using Pulse Compression
These radar sets transmit a relatively weak pulse with a longer pulse-width. It
modulates the transmitting signal to obtain a distance resolution also within the
transmitting pulse with help of the pulse-compression.
Monostatic / Bistatic Radars
Monostatic radars are deployed in a single site. Transmitter and receiver are
collocated and the radar uses the same antenna mostly. Bistatic radar consists of
a separated (by a considerable distance) transmitting and receiving sites.

27. Classification on the basis of design:
Radar systems may be divided into types based on the designed use. This
section presents the general characteristics of several commonly used radar
systems:
Classification of radar sets according its use
Although any and every radar can be abused as military radar, the necessary
distinction as military or civil radar has legal causes often.
27
Air-defence Radars
Air-Defence Radars can detect air
targets and determine their position,
course, and speed in a relatively
large area. The maximum range of
Air-Defence Radar can exceed 300
miles, and the bearing coverage is a
complete 360-degree circle. Diagram of Rotating radar pattern
Air-Defence Radars are usually divided into two categories, based on the
amount of position information supplied. Radar sets that provide only range and
bearing information are referred to as two-dimensional, or 2D, radars. Radar
sets that supply range, bearing, and height are called three-dimensional, or 3D,
radars. Air-Defence Radars are used as early-warning devices because they can
detect approaching enemy aircraft or missiles at great distances. In case of an
attack, early detection of the enemy is vital for a successful defence against
attack. Antiaircraft defences in the form of antiaircraft artillery (abbreviated to
“AAA”) missiles, or fighter planes must be brought to a high degree of
readiness in time to repel an attack. Range and bearing information, provided by
Air-Defence Radars, used to initially position fire-control tracking radar on a
target. Another function of the Air-Defence Radar is guiding combat air patrol
(CAP) aircraft to a position suitable to intercept an enemy aircraft. In the case of

28. aircraft control, the guidance information is obtained by the radar operator and
passed to the aircraft by either voice radio or a computer link to the aircraft.
28
Air traffic control (ATC)
It is a service provided by ground-based
controllers who direct aircraft on the
ground and through controlled airspace, and can
provide advisory services to aircraft in non-controlled
airspace. The primary purpose of
ATC worldwide is to prevent collisions,
organize and expedite the flow of traffic, and
provide information and other support
for pilots.
In some countries, ATC plays a security or
defensive role, or is operated by the military.
Since radar center control a large airspace area,
typically use long range radar that has the
capability are used, at higher altitudes, to see Air Surveillance Radar
aircraft within 200 nautical miles (370 km) of the radar antenna.

29. SOME RADAR SETS
ROHINI
29
3DSURVEILLANCE RADAR
The 3D Surveillance Radar is state-of-art radar designed to effectively play the role of
medium range surveillance radar mounted on a mobile platform. The radar operates in S-band
and is capable of Track-While- Scan [TWS] of airborne targets up to 150 Kms.
SALIENT FEATURES
 3D State of the art medium Range Surveillance Radar.
 TWS of airborne Targets upto 150 Kms.
 Configured as three mobile units mounted on three vehicles.
 Fully automated and controlled from Radar Console with user friendly GUI.
 Dedicated on-line BITE facility.
 Data remoting of Tracks and plots over LAN to remote stations.
 Data remoting of Digital data Link to remote data center.

30. ASHLESHA
Low Level Light-Weight Radar (LLLR) is an S-Band, 3D, light weight,
battery powered and compact sensor which provides 3D surveillance. This radar
is with multiple beams and electronic scanning capability in elevation and can
be rapidly deployed in various terrains like mountain tops, deserts and even
high rise buildings in urban areas to help carryout aerial surveillance at low and
medium altitudes. The radar would provide for detection and tracking of all
kinds of hostile aerial targets like fighter aircrafts, UAVs and helicopters.
30
SALIENT FEATURES
 S-Band 3D Surveillance of aerial targets flying at low and medium
altitudes.
 Automatic detection and tracking of:-Fixed wing aircrafts-Helicopter.
 Detection of hovering Helicopters.
 Low power consumption and mechanical ruggedness to operate in
extreme climatic conditions.
 Based on semi active array antenna using the state of art Transmit/
Receive Module (TRM) technology.
 Integrated IFF.
 Easily transportable by men, animal transport, etc.
 Highly modular for quick setup.
 Robust design and good testability/ maintainability features

31. BHARANI
Low Level Light-Weight Radar (LLLR) is a L-Band,2D, light weight,
battery powered and compact sensor which provides 2D surveillance solution to
alert Army Air Defence Weapon Systems mainly in mountainous terrain against
hostile aerial targets like UAVs, RPVs, hovering helicopters and fixed wing
aircraft flying at low and medium altitudes.
31
SALIENT FEATURES
 L-Band 2D Surveillance of aerial targets flying at low and medium
altitudes.
 Automatic detection and tracking of:-Fixed wing aircrafts-Helicopter-
UAVs
 Detection of hovering Helicopters.
 Target designation and distribution to Weapon Sites and Command
Centre.
 Integrated IFF.
 Easily transportable by men, animal transport, etc.
 Highly modular for quick setup.
 Remote operation and radar display through the Commander's Display
Unit (CDU).
 Separation of CDU from sensor head: 750 m

32. Indra II
INDRA II is L Band low-flying detection radar that caters to the vital gap
filling role in an air defence environment. It is a transportable and self-contained
system with easy mobility and deployment features. The system
consists mainly of an Antenna, Transmitter cabin and Display cabin mounted on
three separate vehicles.
32
SALIENT FEATURES
 Fully coherent system
 Frequency agility
 Pulse compression
 Track while scan for 2-D tracking
 Capability to handle 200 tracks
 Association of primary and secondary targets
 Full tracking capabilities for manoeuvring targets
 Multicolour PPI Raster Scan Display, presenting both MTI and Synthetic
Video
 Automatic target data transmission to a digital modem/networking of
radars
 Ease of transportation and fast deployment.

33. 3-D TACTICAL CONTROL RADAR
The 3D Tactical Control Radar is state-of-art medium range Surveillance
& Tracking radar designed to effectively play the role of medium range
surveillance radar mounted on a mobile platform. The radar operates in S-band
and is capable of Track-While-Scan [TWS] of airborne targets up to 90 Kms.
33
SALIENT FEATURES
 3D State of the art medium Range Surveillance and Tracking Radar.
 TWS of airborne Targets up to 90 Kms.
 Side-lobe blanking, Frequency agility and Jammer analysis.
 Integrated IFF & co-mounted antenna.
 Configured in two TATRA vehicles one for radar and second for power
source.
 Fully automated and controlled from Radar Console with user friendly
GUI.
 Dedicated facility.
 Facility for training controllers, operators & technical crew.
 Facility for automatic transmission of data to Target Data Receiver (co-located
with weapon system) up to a distance of 20 Km from radar using
optical line, wire line and secure VHF radio set.
 Data remoting of Tracks and plots over LAN to external networks - up to
500 m.

34. TACTICAL CONTROL RADAR
The Tactical Control Radar is an early warning, alerting and cueing
system, including weapon control functions. It is specially designed to be highly
mobile and easily transportable, by air as well as on the ground. This radar
minimises mutual interference of tasks of both air defenders and friendly air
space users. The command and control capabilities of the RADAR in
combination with an effective ground based air Defence provide maximum
operational effectiveness with a safe, efficient and flexible use of the airspace.
34
SALIENT FEATURES
 All weather day and night capability
 40 km range, giving a large coverage
 Multiple target handling and engagement capability
 Local threat evaluation and engagement calculations assist the
commander's decision making process, and give effective local fire
distribution.
 Easy to operate, and hence low manning requirements and stress
reduction under severe conditions
 Highly mobile system, to be used in all kinds of terrain, with short into
and out of action times (deployment/redeployment)
 Clutter suppression
 High resolution, which gives excellent target discrimination and allows
accurate tracking

35. RADAR DEVICES
35
RADAR ANTENNA
Antenna is a structure which serves as a transition between wave propagating in
free space, and the fluctuating voltages in the circuit to which it is connected.
An antenna either receives energy from an electromagnetic field or radiates
electromagnetic waves produced by a high frequency generator.
Parabolic Antenna
The parabolic dish antenna is the form most frequently used in the radar
engineering of installed antenna
types. A dish antenna consists of
one circular parabolic reflector and
a point source situated in the focal
point of this reflector. This point
source is called “primary feed” or
“feed”.
The circular parabolic (parabolic)
reflector is constructed of metal,
usually a frame covered by metal
mesh at the inner side.
Reflector (secondary radiator)
Feed (primary radiator)
Parabolic antenna
The width of the slots of the metal mesh has to be less than λ/10. This metal
covering forms the reflector acting as a mirror for the radar energy. According
to the laws of optics and analytical geometry, for this type of reflector all
reflected rays will be parallel to the axis of the parabolic which gives us ideally
one single reflected ray parallel to the main axis with no side lobes. The field
leaves this feed horn with a spherical wave front. As each part of the wave front
reaches the reflecting surface, it is shifted 180 degrees in phase and sent
outward at angles that cause all parts of the field to travel in parallel paths.

36. 36
The Cassegrain Antenna
A Cassegrain antenna is an antenna in
which the feed radiator is mounted at or
near the surface of a concave main reflector
and is aimed at a convex subreflector. Both
reflectors have a common focal point.
Energy from the feed unit (a feed horn
mostly) illuminates the secondary reflector,
which reflects it back to the main reflector,
which then forms the desired forward
beam.
Principle of a Cassegrain telescope
Slot Antenna
Slot radiators or slot antennas are antennas that are used in the frequency
range from about 300 MHz to 25 GHz.
Basic geometry of a slotted waveguide antenna
They are often used in navigation radar usually as an array fed by a waveguide.
But also older large phased array antennas used the principle because the slot
radiators are a very inexpensive way for frequency scanning arrays. Slot
antennas are an about λ/2 elongated slot, and excited in the center.

37. 37
Radar Transmitter
A radar transmitter generates
RF- energy necessary for
scanning the free space. The
often very large amount of
energy must be modulated
in a specific time pattern to
obtain a time reference for time Non-linear FM transmitting pulses
measurement of the signal
Radar Receiver
The function of the receiver is to take the weak echoes from the antenna system,
amplify them sufficiently, detect the pulse envelope, amplify the pulses, and
feed them to the indicator. The receivers used in radars are capable of accepting
weak echoes and increasing their amplitudes by a factor of 20 or 30 million.
Since radar frequencies are not easily amplified, a superheterodyne receiver
changes the radio frequency to an intermediate frequency for amplification.
Radar Display
Modern radar systems typically use some sort of faster scan display to produce
a map-like image. Early in radar development, numerous circumstances made
such displays difficult to produce. People ultimately developed several different
display types.
The radar system transmits a single pulse of electromagnetic radiation, a small
portion of which backscatter off targets (intended or otherwise) and return to the
radar system. The radar receiver converts all received electromagnetic radiation
into a continuous electronic analog signal of varying (or oscillating) voltage.

38. 38
Radar A- Scope
Principle of operation of an A-scope
The A-scope display, shown in the figure, presents only the range to the target
and the relative strength of the echo. Such a display is normally used in
weapons control radar systems. The bearing and elevation angles are presented
as dial or digital readouts that correspond to the actual physical position of the
antenna. The A-scope normally uses an electrostatic-deflection crt. The sweep is
produced by applying a sawtooth voltage to the horizontal deflection plates. The
electrical length (time duration) of the sawtooth voltage determines the total
amount of range displayed on the crt face.
The A- scope display is using in older radar sets only as monitoring
oscilloscope. In modern digital radar sets don't exist a similar video signal of the
backscatter. The target messages are transmitted to the displays as a digital
word. There isn't any possibility to get a synchronizing signal for these
asynchronous serial digital signals. Well, the oscilloscope can get an internal
trigger only. Therefore it is impossible to analyze the bit sequence with a simple
oscilloscope.

39. 39
Radar B-Scope
B - Scope
The B-Scope shows a picture like a Cartesian diagram. It provides a 2-D “top
down” representation of space. The horizontal axis (abscissa) typically
represents the measurement of the azimuth (bearing), and the vertical axis
(ordinate) represents the measurement of the range. Signals appear as bright
spots.
B-scope displays were common in airborne and fire-control radars in the 1950s
and 60s, which were mechanically or electronically scanned from side to side,
and sometimes up and down as well. The center of the bearing usually is
movable through hand wheels in fire-control radars. The antenna turntable then
is turned into the new direction. The screens middle is defined as the main
reception direction of the antenna normally. The bearing area is covered through
an electro-mechanical or electronic beam steering.
The used designation “B-scope” is ambiguous sometimes. The term refers to
two completely different types of scopes. In radar devices without measurement
of the azimuth angle, the term “B-scope” is also used (e.g.: Ground Penetration
Radars). The abscissa is a time coded scale then, and shows a history of the
pulse periods.

40. 40
PLAN-POSITION INDICATOR
It is an intensity-modulation type display system which indicates both range and
azimuthal angle of the target
simultaneously in polar coordinates.
The demodulated echo signal from
the receiver is applied to the grid of
the CRT which is biased slightly
beyond cut-off. Only when blips
corresponding to the targets occur, a
sawtooth current applied to a pair of
coils (on the opposite of the neck of
the tube) flows. Thus, a beam is
made to deflect radially outward
from the centre and also
continuously around the tube at the
same angular velocity as that of the
antenna. The brightness spot at any
point on the screen indicates the
presence of an object there. Plan Position Indicator
The distance of the bright spot radiating outward from the centre gives the range
or the distance of the target from the radar transmitter while the direction in
which the spot deflects at certain instant corresponds to the direction of radar
antenna (i.e. target direction) at that instant. Thus a map-like presentation is
obtained in true relationship to the polar-coordinates of the target scanned.
Normally PPI screens are circular with a diameter of 30 cm or 40 cm. Long-persistence
phosphorous are used to ensure that the PPI screen does not flicker.
Scanning speed is rather low (compared to the 60 fields/sec in TV), so that
various portions of the screen do not get dim between successive scans. The
resolution of the screen depends on the bandwidth of the antenna, pulse width,
the transmitter frequency and diameter of CRT beam.
Distortion of true map position will occur if PPI is used on an aircraft and its
antenna is not pointing straight down. Then computer processing is used to
correct for radar altitude, thus converting slant range into true range. However it
is expensive. PPI displays are used in search radars and especially when conical
scanning is employed.
With modern computer graphics, all of the displays could be made available on
a single screen either in time multiplexed form or in split screen presentation
format. Advanced concepts such as holographic display could become a reality
that would provide true 3-D displays.

41. Future Research:
The focus is in the use of radar for surveillance and environmental Electrical
and Electronic Engineering and the Discipline of Physics in the School of
Science together with various external organizations such as the Australian
Defence Science and Technology Organisation, the Bureau of Meteorology, the
Australian Antarctic Division and commercial companies such as Raytheon
Australia.
Key research themes in the Centre are in the area of radar systems and
technology, RF propagation and radar signal processing. The applications focus
for the Centre's research will be the areas of environmental and atmospheric
monitoring through radar sensing, surveillance and radar systems design.
Radar technology currently used to support tactical operations aboard Navy
ships will soon be adapted for a new purpose – weather detection. This state-of-the-
art phased array radar technology may help forecasters of the future provide
41

42. CONCLUSION
The six weeks of summer training at BEL, Ghaziabad unit generated a lot more
interest in my subject.
It made me more aware of the scope of Electronics & Communication
Engineering. It has also made me appreciative of an industrial work
environment.
Undergoing training on the indoor substation has helped me integrate
conceptual knowledge with real life application. I was fortunate to have
personal guidance from experienced professionals who took been interest in
explaining the working details of various equipments.
I feel that without this opportunity, my own understanding of this subject and
also the motivation to acquire more knowledge would have remained
incomplete. Well, regarding future scope I think my training has given me
enough motivation and an exposure that I will try to join defence services or get
linked up with the defence of the country.
“To know the technical know-how, industrial training is the best way to move
forward.”
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43. BIBLIOGRAPHY
[1] THE MAIN RESOURCES OF THE WORK WERE THE FACULTY OF
HRD DEPARTMENT.
43
[2] WEBSITE:
 http://www.bel-india.com
 http://www.radartutorial.eu/01.basics/radar%20Principle.en.html