1. 1
A PROJECT REPORT
ON
TRACKING RADAR
SYSTEM
BY
Ananya Mahalik, Regd No: 13010388, ETC, VSSUT, BURLA
PriyambadaPradhan, Regd No: 13010390, ETC, VSSUT, BURLA
ShrutiSmruti Mishra, Regd No: 13010399, ETC, VSSUT, BURLA
Pratibha Singh, Regd No: 13010395, ETC, VSSUT, BURLA
KshirabdhiTanayaPatra, Regd No: 122042, ECE, GITA, BHUBANESWAR
SailajaRoul, Regd No: 122081, ECE, GITA, BHUBANESWAR
In ITR, DRDO from 1st June 2015 to 30th June 2015 (30 days)
2. 2
CERTIFICATE
This is to certify that this project report entitled “TRACKING RADAR
SYSTEM” submitted to “INTEGRATED TEST RANGE, DEFENCE
RESEARCH and DEVELOPMENT ORGANISATON, CHANDIPUR,
ODISHA”, is the work done by ‘Priyambada Pradhan’, Department of Electronics
and Telecommunication Engineering, Veer Surendra Sai University of
Technology, Burla under the supervision of Mr. CHINMAY NAYAK, Scientist
“E”, RSG, ITR from 1st June 2015 to 30th June 2015. During this period she
worked under my guidance and supervision and she has successfully completed the
above project assigned by me. During the training she was sincere and showed
keen interest in doing her projects, thus completing it in stipulated time.
Mr. C K Nayak, Sc‘E’ Mr. Niladri Roy, Sc‘F’ Mr. C R Ojha, Sc‘F’
RSG, ITR GD (RAD & MET) GD (HR)
3. 3
CERTIFICATE
This is to certify that this project report entitled “TRACKING RADAR
SYSTEM” submitted to “INTEGRATED TEST RANGE, DEFENCE
RESEARCH and DEVELOPMENT ORGANISATON, CHANDIPUR,
ODISHA”, is the work done by ‘Shruti Smruti Mishra’, Department of
Electronics and Telecommunication Engineering, Veer Surendra Sai University of
Technology, Burla under the supervision of Mr. CHINMAY NAYAK, Scientist
“E”, RSG, ITR from 1st June 2015 to 30th June 2015. During this period she
worked under my guidance and supervision and she has successfully completed the
above project assigned by me. During the training she was sincere and showed
keen interest in doing her projects, thus completing it in stipulated time.
Mr. C K Nayak, Sc‘E’ Mr. Niladri Roy, Sc‘F’ Mr. C R Ojha, Sc‘F’
RSG, ITR GD (RAD & MET) GD (HR)
4. 4
CERTIFICATE
This is to certify that this project report entitled “TRACKING RADAR
SYSTEM” submitted to “INTEGRATED TEST RANGE, DEFENCE
RESEARCH and DEVELOPMENT ORGANISATON, CHANDIPUR,
ODISHA”, is the work done by ‘AnanyaMahalik’, Department of Electronics and
Telecommunication Engineering, Veer Surendra Sai University of Technology,
Burla under the supervision of Mr. CHINMAY NAYAK, Scientist “E”, RSG, ITR
from 1st June 2015 to 30th June 2015. During this period she worked under my
guidance and supervision and she has successfully completed the above project
assigned by me. During the training she was sincere and showed keen interest in
doing her projects, thus completing it in stipulated time.
Mr. C K Nayak, Sc‘E’ Mr. Niladri Roy, Sc‘F’ Mr. C R Ojha, Sc‘F’
RSG, ITR GD (RAD & MET) GD (HR)
5. 5
CERTIFICATE
This is to certify that this project report entitled “TRACKING RADAR
SYSTEM” submitted to “INTEGRATED TEST RANGE, DEFENCE
RESEARCH and DEVELOPMENT ORGANISATON, CHANDIPUR,
ODISHA”, is the work done by ‘Pratibha Singh’, Department of Electronics and
Telecommunication Engineering, Veer Surendra Sai University of Technology,
Burla under the supervision of Mr. CHINMAY NAYAK, Scientist “E”, RSG, ITR
from 1st June 2015 to 30th June 2015. During this period she worked under my
guidance and supervision and she has successfully completed the above project
assigned by me. During the training she was sincere and showed keen interest in
doing her projects, thus completing it in stipulated time.
Mr. C K Nayak, Sc‘E’ Mr. Niladri Roy, Sc‘F’ Mr. C R Ojha, Sc‘F’
RSG, ITR GD (RAD & MET) GD (HR)
6. 6
CERTIFICATE
This is to certify that this project report entitled “TRACKING RADAR
SYSTEM” submitted to “INTEGRATED TEST RANGE, DEFENCE
RESEARCH and DEVELOPMENT ORGANISATON, CHANDIPUR,
ODISHA”, is the work done by “Kshirabdhi Tanaya Patra”, Department of
Electronics and Communication Engineering, Gandhi Institute for Technological
Advancement, Bhubaneswar under the supervision of Mr. CHINMAY NAYAK,
Scientist “E”, RSG, ITR from 1st June 2015 to 30th June 2015. During this period
she worked under my guidance and supervision and she has successfully
completed the above project assigned by me. During the training she was sincere
and showed keen interest in doing her projects, thus completing it in stipulated
time.
Mr. C K Nayak, Sc‘E’ Mr. Niladri Roy, Sc‘F’ Mr. C R Ojha, Sc‘F’
RSG, ITR GD (RAD & MET) GD (HR)
7. 7
CERTIFICATE
This is to certify that this project report entitled “TRACKING RADAR
SYSTEM” submitted to “INTEGRATED TEST RANGE, DEFENCE
RESEARCH and DEVELOPMENT ORGANISATON, CHANDIPUR,
ODISHA”, is the work done by “Sailaja Roul”, Bachelor of Technology,
Department of Electronics and Communication Engineering, Gandhi Institute for
Technological Advancement, Bhubaneswar under the supervision of Mr.
CHINMAY NAYAK, Scientist “E”, RSG, ITR from 1st June 2015 to 30th June
2015. During this period she worked under my guidance and supervision and she
has successfully completed the above project assigned by me. During the training
she was sincere and showed keen interest in doing her projects, thus completing it
in stipulated time.
Mr. C K Nayak, Sc‘E’ Mr. Niladri Roy, Sc‘F’ Mr. C R Ojha, Sc‘F’
RSG, ITR GD (RAD & MET) GD (HR)
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ACKNOWLEDGEMENT
We have been part of the project “RADAR SYSTEM”. The project has required
our full involvement; however, it would not have been possible without the kind
support of many individuals. We would like to extend our sincere thanks to all of
them.
We hereby express our gratitude whole-heartedly to the Director, ITR Mr.
MVKV Prasad, Sc ‘H’ (OS) for allowing us to undergo our training at Integrated
Test Range. We are also grateful to Mr. C. R. OJHA, Sc ‘F’ and the whole HRD
team for assigning us the Radar System’s Group. We would also like to thank Mr.
Niladri Roy, Sc ‘F’, GD (RSG) ITR for providing us a friendly and co-operative
environment to work with.
Finally we would like to thank Mr Chinmay Nayak, Scientist ’E’, Mr. Mihir
Kumar Meher, Sc’D’ and Mr A.K.Pati, TO ‘D’ who was always there to clear our
doubts and guide us in every possible way to carry out this project .Our training
period has been a great opportunity for us and we came to know a lot about the
Tracking Radar Systems.
We would like to express our gratitude to all staff members of Radar System
Group for their kind co-operation and encouragement for the valuable guidance
they provided in their respective fields. Lastly, we thank almighty, our parents,
friends for their constant encouragement without which this project would not have
been possible.
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CONTENT
TOPIC Page No
1. Introduction to RADAR 10
2. Principle of RADAR 11
3. RADAR Range Equation 11
4. Types of RADAR 12
5. RADAR Bands 14
6. Gain Directivity of Antenna 14
7. RADAR Cross-section 15
8. Match Filtering 15
9. Range Ambiguity Resolution 16
10. Doppler Effect 17
11. Pulse Doppler Signal Processing 17
12. Radome 18
13. PCMC RADAR 19
14. RADAR Sub-system 20
15. RADAR Modulator 23
16. Continuous Wave RADAR 23
17. Types of Scan 23
18. Direct Digital Synthesizer 24
19. KAMA- N RADAR System 25
20. Skin Mode and Transponder Mode 26
21. PPI 27
22. Applications of RADAR 29
23. Conclusion 31
24. References 32
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1. INTRODUCTION TO RADAR
Radar is an object-detection system that uses radio waves to determine the range,
altitude, direction, or speed of objects. As the name suggests, RADAR first detects
if a target or source is present then finds out the range of the target. It can be used
to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather
formations, and terrain. The radar dish (or antenna) transmits pulses of radio waves
or microwaves that bounce off any object in their path. The object returns a tiny
part of the wave's energy to a dish or antenna that is usually located at the same site
as the transmitter.
Radar was secretly developed by several nations before and during World War II.
The term RADAR was coined in 1940 by the United States Navy as an acronym for
RAdioDetection AndRanging.
During the detection of the target by the RADAR, sometimes the RADAR shows
error. If the object or the target is not present but the RADAR shows its presence,
it is known as false detection. If the object or the target is present but the RADAR
does not show its presence, it is known as mis-detection.
The modern uses of radar are highly diverse, including air and terrestrial traffic
control, radar astronomy, air-defense systems, antimissile systems; marine radars
to locate landmarks and other ships; aircraft anticollision systems; ocean
surveillance systems, outer space surveillance and rendezvous systems;
meteorological precipitation monitoring; altimetry and flight control systems;
guided missile target locating systems; and ground-penetrating radar for geological
observations.
The parameters provided by the radar are:
R=range
Ɵ=elevation
Ø=azimuthal angle
T=time and
Vr=radial velocity
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2. PRINCIPLE OF RADAR
The principle of radar is that a transmitter sends out a radio signal, which will
scatter off anything back to a radio receiver, located near the transmitter, that it
encounters (land, sea ships, and aircrafts) and a small amount of energy is
scattered. We use directivity antenna so the direction of the antenna gives the angle
of the target. Radar not only informs about the current position but also the future
position with respectto time. It gives us the azimuth angle, elevation and the range
thus giving all the required coordinates needed to know the position of the target in
the space.
Range to Target
The range to a target is determined by the time it takes for the radar signal to
travel to the target and return back. It is given by
R=C*T/2
Where R=Range of the target
C=Velocity of light
T=Time
3. RADAR RANGE EQUATION
In the radar equation we relate the range of radar to that of the characteristics of
the transmitter, receiver, antenna, target, and environment. It is not only useful to
determinethe maximum distance from the radar to the target, but it can also be used
to serve both as a tool for under- standing radar operation and as a basis for radar
design.
WHERE, PT=Powerof transmitting antennae
SIGMA=Radar cross section
LS=Losses
SNR=signal to noise ratio
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Radars usually employ directive antennas to channel, or direct, the radiated power
Pt into some particular direction
4. TYPES OF RADAR
Basically there are two types of RADAR:
1: Continuous wave RADAR- The transmitter generates a continuous oscillation of
frequency (sine waves), that is radiated by the antenna and a portion of the radiated
energy is intercepted by the target and is scattered, some of it in the direction of the
radar, where it is collected by the receiving antenna.
2: Pulsed RADAR- The transmitter generates a discrete oscillation of frequency
(sine waves), that is radiated by the antenna and a portion of the radiated energy is
intercepted by the target and is scattered, some of it in the direction of the radar,
where it is collected by the receiving antenna.
TRACKING RADAR is of 4 types:
1. Conical Scanning: It is a sequential scanning system. Signal to noise ratio is
small. Angle and Range accuracy are inferior to that of monopulse radar. It is
not complex and has only one receiving channel and a single feed.
Ex: Kama-N Radar
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2. Monopulse Radar: In this radar, instead of switching the antenna position in
different directions sequentially we transmit the antenna beam simultaneously.
So, it is also called as simultaneous lobbing. More than one returned pulse is
required to locate a target accurately. Ex: PCMC Radar
3. Sequential Lobbing: In Sequential Lobbing the direction of antenna beam is
rapidly switched between two positions, so that the strength of echo from target
will fluctuate at the switching rate unless the target is exactly mid-way between
the two directions. The difference in amplitude of the echo signal at two
positions is a measure of angular displacement of the target from the switching
axis. An important feature of Sequential Lobbing is that the target position
accuracy can be far better than given by antenna beam width. Its operation is
simple, requires less equipment, one antenna and is cost effective.
4. Phased Array Radar: This is a multi target tracking radar, uses array antenna.
Antenna is not rotated but antenna beam is rotated electronically by excitation
pulse control. The scan rate is very fast and is a few microseconds.
Other types of RADAR:
Search radar
Target radar
Weather sensing radar
Navigational radar
Mapping radar
Road radar
Radar for biological research
Marine radar
Ground penetrating radar
Vessel traffic service radar
THE TYPE OF RADAR USED HERE IS TRACKING RADAR PC-MC RADAR
(PRECISION COHERENT C-BAND MONO PULSE RADAR)
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5. RADAR BANDS:
L BAND:1 TO 2 GHz frequency,
Wavelength: 15-30cm
Operation of log range air surveillance radar and its range is 400 km.
S BAND:2 TO 4 GHz frequency
Wavelength: 7.5-15cm
Used more in tropic and sub tropic climate and its terminal area is 100 km.
C BAND:4TO 8 GHz frequency
Wavelength: 3.75-7.5cm
It is referred to as G band. Much mobile military battlefield surveillance,
missile control uses this band.
X BAND:8 TO 12 GHz frequency
Wavelength: 2.4-3.75cm
This frequency band is used for maritime, civil and military navigational
radar.
Ku BAND: 12-18GHz frequency
Wavelength: 1.7-2.4cm
K BAND:18 – 26.5 GHz frequency
Wavelength: 1.1-1.7cm
Ka BAND:26.5-40GHz frequency
Wavelength: 0.75-1.1cm
Millimetre BAND:40-100GHz
Wavelength: 0.30-0.75cm
Radar application in this frequency band provides short range, very high
resolution and high data rate. It is also used for high capacity terrestrial
millimetre wave communication.
6. GAIN DIRECTIVITY OF AN ANTENNA
An ANTENNA is a device used to transmit electromagnetic waves to free
space. Thus it is a device which performs impedance matching. It is also a
transducer.
The power received by the antennae at a particular point =gain.
Directivity is mentioned because of direction of maximum power received.
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7. RADAR CROSS SECTION
It is the measure of a target’s ability to reflect radar signals in the direction
of the radar receiver. It is a measure of the ratio of the backscatter density in
the direction of the radar to the power density that is intercepted by the
target. Since the power is distributed on the shape of sphere, only a small of
this can be received by the radar. In short The RCS of a target can be told as
a comparison of the strength of the reflected signal from a target to the
reflected signal from a perfectly smooth sphere.
Factors affecting RCS:
The used material types. Metals are strongly radar reflective whereas plastic
or fibre is less reflective.
Radar absorbent paint. Radar energy->heat energy.
The target’s physical geometry and external features.
Designed to be flat and very angled such that radar will be incident at a large
angle that will bounce off at similar high reflected angle.
RCS for point like objects:-
TARGETS RCS(m2
) RCS(in dB)
Bird 0.01 -20
Man 1 0
Cabin Cruiser 10 10
Automobile 100 20
Truck 200 23
Corner Reflector 20379 43.1
8. MATCH FILTERING
Matched filtering is a process for detecting a known piece of signal or
wavelet that is embedded in noise. The filter maximises the SNR of the
signal being detected with respect to the noise. The figure below shows input
16. 16
S and noise N. The objective is to design a filter, H(t) that maximises the
SNR of the output y(t).
9. RANGE AMBIGUITY RESOLUTION
Pulse repetition frequency plays a major role in determining the maximum
range of the radar set. Sometimes the period between successive pulses
becomes too short, so an echo from a distant target may return after the
transmitter has emitted another pulse. This makes it difficult to find whether
the observed pulse is echo of the pulse just transmitted or the echo of the
preceding pulse. Thus leading to a situation called as range ambiguity.
Hence it becomes ambiguous to derive range information.
A high Pulse repetition frequency repeats resolution and range accuracy by
sampling the position of the target more often.
Range ambiguity resolution is the techniques used with medium pulse
repetition frequency (PRF) radar to contain range information for distances
that exceed the distance between transmit pulses. Medium PRF is selected so
that the reflection is always due to the previous pulse and to avoid
interference. The return signal from a reflection will appear to be arriving
from a distance less than the true range of the reflection when the
wavelength of the PRF is less than the range of the reflection. This causes
reflected signals to be folded, thus apparent range is a modulo function of
the true range.
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The maximum unambiguous range Rmax is the maximum distance radar
energy can travel round trip between pulses and still produce reliable
information. The maximum unambiguous range of any pulse radar can be
computed as:-
Rmax=c/(2*PRF)
Where c = speed of light.
10.DOPPLER EFFECT
Doppler shift depends upon whether the radar configuration is active or
passive. Active radar transmits a signal that is reflected back to the receiver.
Passive radar depends upon the object sending a signal to the receiver.
The Doppler frequency shift for active radar is as follows, where is
Doppler frequency, is transmitting frequency, is radial velocity, and
is the speed of light:
Passive radar is applicable to electronic countermeasures and radio
astronomy as follows:
11. PULSE-DOPPLER SIGNAL PROCESSING
18. 18
The rangesample axis represents individual samples taken in between each
transmit pulse. The range interval axis represents each successive transmit pulse
interval during which samples are taken. The fast Fourier transform process
converts time-domain samples into frequency domain spectra. This is sometimes
called the bed of nails.
Pulse-Doppler signal processingincludes frequency filtering in the detection
process. Thespacebetween each transmit pulse is divided into range cells or range
gates. Each cell is filtered independently much like the process used by a spectrum
analyzer to producethe display showing different frequencies. Each different
distance produces a different spectrum. These spectraare used to perform the
detection process. This is required to achieve acceptable performance in hostile
environments involving weather, terrain, and electronic countermeasures.
12.RADOME
It is defined as a structural, weather proofenclosure to protect an antenna. The
material that is used in building the radome allows us a relatively unattenuated
electromagnetic signal between the antenna inside the radome and outside
equipment.
A Radome protects the surfaces of the antenna from the effects of environmental
exposure. Radomes can be constructed in a number of shapes and sizes but the
spherical shape is the best and preferred due to its stability. The particular
frequency or application determines the use of a variety of construction materials.
The radome material is such that it minimally attenuates the electromagnetic signal
transmitted or received by the antenna.
Radome also protects the antenna surface or conceals the antenna electronic
equipment from public view. A radome should offer reliable protection with zero
signal loss.
Radome
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Radomes can be often in tens of metres in diameters.So a radome protects antenna
within from the wind,rain,ice,sand, and even ultraviolet rays.When the antenna
within are rotating we could also say that they protect people who otherwise might
get hurt by getting in the way.
13.PRECISION COHERENT MONOPULSE C-BAND RADAR (PCMC
RADAR)
The round-trip time for the radar pulse to get to the target and return is measured.
The distance is proportional to this time. Here, one antenna is used.
Duplexer
Rx RF
Range Angle
Channel Channel
Simplified Block Diagramof a pulsed RADAR
Antennae
Circulator High Power
Oscillator
Power
Modulator
TR Cell LNA
Mixer ,Band
pass Filter
Local
Oscillator
IF AmplifierSecond Diode
Detector
Video
Amplifier
RTSS ATSS
Angle DisplayDisplay
Data Record and
Transmission
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14. RADAR SUBSYSTEMS
Radar’s components are:
MODULATOR: In order to detect and track the target, electromagnetic
waves are sent via the modulator which consists of discrete sine waves. It
generates repetitive train of pulses (turned on and off).
DUPLEXER: The power sent by the radar is in the order of MW
(megawatts) but the power received is in the order of pW (Pico watts). But
there are chances power of higher watts may enter the receiver hence
causing damage to it. Hence, the duplexer is used to protect the receiver
from higher power during transmission. The duplexer used in the block
diagram of radar is a mechanical high power switch which separates
transmitted and received signal. The duplexer is also used to serve as a
channel to the returned echo signals to the receiver and not to the
transmitter. The duplexer consists of two gas-discharge devices, one known
as a TR (transmit-receive) and the other an ATR (anti-transmit-receive). The
TR is used to protect the receiver during transmission and the ATR directs
the echo signal to the receiver during reception. Solid-state ferrite circulators
and receiver protectors with gas-plasma TR devices and/or diode limiters are
also employed as duplexers.
Transmitted
Power
Received Power
MIXER & LO: At first stage a low noise RF amplifier is employed, such as
a parametric amplifier or a low-noise transistor. However, it is not always
desirable to employ a low-noise first stage in radar but the receiver input can
simply be the mixer stage, especially in military radars that must operate in a
noisy environment. Although a receiver with a low-noise front-end will be
more sensitive, the mixer input can have greater dynamic range, less
susceptibility to overload, and less vulnerability to electronic interference. The
21. 21
mixer and local oscillator (LO) convert the RF signal to an intermediate
frequency (IF). We have to change frequency of LO so as to keep IF constant
BPF: The Band Pass Filter can be used to attenuate a certain frequency and
allows a certain bandwidth.
For example: sin(wrxrft) * sin(wlot) =cos(wrxrf-wlo)t – cos(wrxrf + wlo)t
(Attenuated by the use BPF)
IF AMPLIFIER: The receiver is usually of the super heterodyne type. The
IF needs to be kept constant.
IF=R̃ F
IF amplifier pushes the signal to higher level so that it comes to the sensitivity
level of the second diode detector. Usually a typical IF amplifier for an air-
surveillance radar might have a centre frequency of 30 or 60 MHz and a
bandwidth of the order of one Megahertz. The IF amplifier is designed as a
matched filter, where its frequency-response function H(f) should maximize
the peak-signal-to-mean-noise-power ratio at the output. This will occur when
the magnitude of the frequency-response function | H(f)| is equal to the
magnitude of the echo signal spectrum |S(.f') |, and the phase spectrum of the
matched filter is the negative of the phase spectrum of the echo signal.
SECOND DIODE DETECTOR: The Second Diode Detector extracts the
pulse modulation, after the signal –to-noise ratio is maximised by the
Intermediate Frequency Amplifier and then sends the video signals to the video
amplifier. The output of the detector is called video signal. The first detector
diode is in the mixer.
VIDEO AMPLIFIER: It receives the video signals from the second
detector and amplifies it to a level so that it can be properly displayed using a
cathode ray tube(CRT).The common form of CRT used now a days is the PPI
i.e., Polar Plot Indicator
A TRANSMITTER that generates the radio signal with an oscillator such
as a klystron or a magnetron and controls its duration by a modulator.
A WAVEGUIDE that links the transmitter and the antenna.
22. 22
A RECEIVER knowing the shape of the desired received signal (a pulse),
an optimal receiver can be designed using a matched filter.
A display processor to produce signals for human readable output devices.
An electronic section that controls all those devices and the antenna to
perform the radar scan ordered by software.
A link to end user devices and displays.
Heart of a radar is a synchroniser because here in radar a high level of time
synchronisation is required (we need to know the time of receiving and
transmitting).also this synchroniser is in connection with all the components. The
circuit starts working, even the transmitter starts transmitting once it gets the sync
signal.
Synchroniser will generate the basic pulse repetition frequency. It produces
trigger pulses that start the transmitter, indicator sweep circuits and ranging
circuits. The function of the majority circuits in Radar are timing or control.
Signals are sent from the synchronizer simultaneously to the transmitter which
sends a new pulse and to the display which resets the return sweep.
The components in radar must operate together in a proper time, so every radar
needs a number of control pulses or triggers. In order to operate the various
subsystems, to generate synchronous time signals so that the subsystems work in a
synced way, we need synchroniser.
Synchroniser will provide the accumulated time of the day.
The basic Synchroniser circuit should meet the following three basic
requirements:-
It must be free running (astable). Because the synchroniser is the Heart of
the radar it must establish the zero time reference and the PRF.
It should be stable in frequency.
For accurate ranging, the PRF and its reciprocal, pulse repetition time (PRT)
must not change.
The frequency must be variable to enable the radar to operate at different
ranges.
23. 23
15.RADAR MODULATORS
MODULATORS act to provide the waveform of the PRF-pulse. There are two
different radar modulator designs:
HIGH VOLTAGE SWITCH for non-coherent keyed power-oscillators these
modulators consist of a high voltage pulse generator formed from a high
voltage supply, a pulse forming network, and a high voltage switch such as a
thyratron. They generate short pulses of power to feed, e.g., the magnetron.
This technology is known as pulsed power. In this way, the transmitted pulse
of PRF radiation is kept to a defined and usually very short duration.
HYBRID MIXERS, fed by a waveform generator and an exciter for a
coherent waveform. This waveform can be generated by low power/low-
voltage input signals. In this case the radar transmitter must be a power-
amplifier, e.g., a klystron tube .in this way, the transmitted pulse is
intrapulse-modulated and the radar receiver must use pulse compression
techniques.
16.CONTINUOUS WAVE (CW) RADAR
One way to obtain a distance measurement is based on the time-of-flight: transmit
a short pulse of radio signal (electromagnetic radiation) and measure the time it
takes for the reflection to return. Since radio waves travel at the speed of light,
accurate distance measurement requires high-performance electronics. In most
cases, the receiver does not detect the return while the signal is being transmitted.
Through the use of a duplexer, the radar switches between transmitting and
receiving at a predetermined rate. The distance resolution and the characteristics of
the received signal as compared to noise depend on the shape of the pulse. The
pulse is often modulated to achieve better performance using a technique known as
pulse compression. It uses two antennas.
PRF should be high to get better information. Range is measured at a minimum
rate, velocity and error at a faster rate.
17. TYPES OF SCAN
PRIMARY SCAN: A scanning technique where the main antenna aerial is
moved to produce a scanning beam, examples includes circular scan, sector
scan, etc.
24. 24
SECONDARY SCAN: A scanning technique where the antenna feed is
moved to produce a scanning beam, examples include conical scan,
unidirectional sector scan, lobe switching, etc.
PALMER SCAN: A scanning technique that produces a scanning beam by
moving the main antenna and its feed. A palmer scan is a combination of a
primary scan and a secondary scan.
CONICAL SCANNING: The radar beam is rotated in a small circle around
the "bore sight" axis, which is pointed at the target.
18. DIRECT DIGITAL SYNTHESISER
DIRECT DIGITAL SYNTHESIZER (DDS) is a type of frequency synthesizer used
for creating arbitrary waveforms from a single, fixed-frequency reference clock.
applications of DDS include: signal generation, local oscillators in communication
systems, function generators, mixers, modulators, sound synthesizers and as part of
a digital phase-locked loop.
A basic direct digital synthesizer consists of a frequency reference (often a crystal
or saw oscillator), a numerically controlled oscillator (NCO) and a digital-to-
analog converter (DAC). A DDS has many advantages over its analog counterpart,
the phase-locked loop (PLL), including much better frequency agility, improved
phase noise, and precise control of the output phase across frequency switching
transitions. Since a DDS is a sampled system, in addition to the desired waveform
at output frequency fout, nyquist images are also generated. In order to reject these
undesired images, a DDS is generally used in conjunction with an analog
reconstruction low pass filter .
BLOCK DIGRAM OF DDS
25. 25
BLOCK DIAGRAM OF A PC-MC RADAR
19. KAMA-N RADAR SYSTEM
KAMA-N RADAR SYSTEM is a conical scan target tracking radar and is
operational in the S‐band frequency range i.e. from 2 to 4 GHz. Transmitter is
oscillator type non‐coherent magnetron version. Antenna is parabolic with dipole
feed and Gregorian structure. Peak power is around 450 KW and gain for S‐band
is around 34dB. S‐band is a single pulse‐width and single band‐width system.
Beam width for S‐band is around 2.8 degrees. Accuracy in range is better than 8m
and in angle is better than 1.5 mill radian.
The electromagnetic waves are transmitted via the waveguide through the
antennae. The waves that strike the object or target and are reflected back to strike
with the antenna. The waves are then reflected in parallel and are assumed to meet
at infinity from the antenna irrespective of the position at which the reflected rays
struck it.
The rays then again strike the target and are reflected to the antennae. The disc of
the antenna is such that the rays irrespective of its position of striking is angled
towards the sub-reflector and is directed towards receiver channelled through the
waveguide.
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Servo System of KAMA N- RADAR
20. SKIN MODE AND TRANSPONDER MODE
Skin Mode is about the basic principle of RADAR. If the RADAR finds a target,
without a transponder code, it is declared a primary target. This target can be
shown as a coloured area on the display. The information about weather or ground
clutter (Dangerous obstacles) is represented in skin mode mostly. It operates totally
independently of the target aircraft i.e. no action from the aircraft is required for it
to provide a RADAR return.
But we have certain limitations in skin mode operation:
Enormous amount of power must be radiated to ensure return from the target
(MW). This is especially true if long range is desired.
Because of the small amount of energy returned at the receiver i.e. in Pico
Watts, returns may be easily disrupted due to such factors as changes of
target attitude or signal attenuation due to heavy rain. Hence, causing the
displayed target to fade.
Co-relation of a particular RADAR return with a particular target requires an
identification process.
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Another mode of operation called as the Transponder Mode which is also the
Identification Friend or Foe System which has been developed as a means of
identifying friendly aircraft from enemy. Here there is a transmitter attached on
board. The Transponder is a radio receiver and the transmitter operating on the
RADAR frequency. The target aircraft responds to interrogation by the ground
station by transmitting a coded reply signal.
The Advantages of Transponder Mode are:
The reply signal being transmitted from the target (Friend or Foe) is much
stronger when received at the ground station. Thus reducing problems of
signal attenuation.
The transmitting Power required by the ground station for a given range is
much minimised, thus providing considerable economy.
But the main disadvantage of Transponder mode is that it requires the target to
carry an operating transponder, thus making it a dependent surveillance system.
21.PPI
It is the Plan Position Indicator. Its co-ordinates are Range and Azimuth Angle.
This scope arranges the values around circles at equal angles which is often a good
way of comparing several sets of performance indicator.
It provides the location and direction of a target on a map like presentation that is
easy to interpret. The display is dark except when echo signals are present.
When scanning in PPI mode, the elevation angle of the radar is held constant and
the azimuth angle is varied, the returns are then mapped on a horizontal plane. If
the Radar rotates through 360 degree, then it is called a surveillance scan and if
less than 360 degree, it is known as sector scan.
If the target is going away, it is known as outbound and if approaching, then it is
known as inbound. The display is tuned for 30MHz but we can vary the LO
frequency.
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22. APPLICATION OF RADAR
The major areas of radar application are:
AIR TRAFFIC CONTROL (ATC): Radars are employed all-round the
globe for the purpose of safely controlling air traffic in the vicinity of
airports and en route. Aircraft and ground traffic at large airports are
monitored by the use of high-resolution radar. Radar has been used with
GCA (ground-control approach) systems to guide aircraft to a safe landing in
bad weather. It is also used in Ground Vehicular Traffic and aircraft taxing.
It also helps in mapping of regions of rain in the vicinity of airports and
weather.
AIRCRAFT NAVIGATION: The weather-avoidance radar used on aircraft
to outline regions of precipitation to the pilot is another useful facet of radar.
Radar is also used for terrain avoidance and terrain following.
SHIP SAFETY: Radar is used for enhancing the safety of ship travel by
warning of potential collision with other ships, and for detecting navigation
buoys, especially in poor visibility. In terms of numbers, this is one of the
larger applications of radar, but in terms of physical size and cost it is one of
the smallest. It has also proven to be one of the most reliable radar systems.
Shore-based radar of moderately high resolution is also used for the
surveillance of harbours as an aid to navigation.
SPACE: Space vehicles have used radar for rendezvous and docking, and
for landing on the moon. Some of the largest ground-based radars are for the
detection and tracking of satellites. Satellite-borne radars have also been
used for remote sensing.
REMOTE SENSING: All radars are remote sensors; however, as this term
is used it implies the sensing of geophysical objects, or the "environment."
For some time, radar has been used as a remote sensor of the weather. It was
also used in the past to probe the moon and the planets (radar astronomy).
LAW ENFORCEMENT: In addition to the wide use of radar to measure
the speed of automobile traffic by highway police, radar has also been
employed as a means for the detection of intruders.
DAY TO DAY APPLICATIONS: In road maintenance, it helps through
high performance electromagnetic roadway mapping and evaluation system.
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Ground Mapping RADAR is used in construction settings. They drag the
unit across the ground to determine if there are any objects or unstable soil
where they plan on building.
MILITARY: Many of the civilian applications of radar are also employed
by the military. The traditional role of radar for military application has been
for surveillance, navigation, and for the control and guidance of weapons. It
represents, by far, the largest use of radar. RADAR is an important part of
Air Defence System, operation of offensive missiles and other weapons.
Then target detection, target tracking and weapon control. It tracks the
targets, directs the weapon to an intercept and assesses the effectiveness of
engagement. It is also used in area, ground and air surveillance.
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23. CONCLUSION
RADAR is used to find velocity, range and position of the object. The advantage
of the RADAR is that it provides superior penetration capability through any
type of weather condition. LIDAR is an 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.
The above project of ours on the topic-radio detection and ranging gives a clear
idea about radar system and various parameters and theories related to it.
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24. REFERENCES
1. www.wikipedia.com
2. www.radartutorial.eu
3. www.meterologytraining.com
4. www.tpub.com
5. www.radomeservices.com
6. www.britannica.com
7. www.ww2010.atmos.uiuc.edu
8. Introduction to Radar System by Skolnik