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Radar is a system that uses electromagnetic waves to identify the range, altitude, direction, or speed of both moving and fixed objects such as aircraft, ships, motor vehicles, weather formations, and terrain. The termRADAR was coined in 1941 as an acronym for Radio Detection and Ranging.
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GLOBUS ENGINEERING COLLEGE, BHOPAL
SEMINAR REPORT
On
BASICS OF RADAR SYSTEM
SUBMITTED TO- SUBMITTED BY-
Mr. LALIT JAIN RAVINDRA MATHANKER [0130ec071046]
Dept. of Electronics AKIB KHAN [0130ec071004]
GEC, BHOPAL E.C. 4th
sem. GEC, BHOPAL
GLOBUS ENGINEERING COLLEGE, BHOPAL
ACKNOWLEDGMENT
We extend our heartiest thanks to Mr. Arvind Kaurav, HOD, Electronics Dept. for his support in accomplishment of this project successfully. Furthermore it was his valuable guidance which helped us immensely in various areas of troubleshooting.
We would also like to thank Mr. Anil Sharma, Principal, Globus Engg. College. He provides us an opportunity to present this paper.
We also thank to our faculties of Electronics Dept. who supported us
by their valuable knowledge.
Last but not the least we would like to extend thank to my seniors who
helped me to reveal various aspect of this project.
We also thank to Microsoft Corp. for production support.
RADAR ( Basics of the Radar System)
H
GLOBUS ENGINEERING COLLEGE, BHOPAL
GLOBUS ENGINEERING COLLEGE, BHOPAL
TABLE OF CONTENT
INTRODUCTION __________________1
HISTORY __________________2
PRINCIPLE OF RADAR __________________3
RADAR EQUATION __________________4
PERIPHERALS OF RADAR __________________5
CLASSIFICATION __________________6
RELATION TO DOPPLER EFFECT_________________7
PULSED RADAR SYSTEM __________________8
RADAR SIGNAL PROCESSING __________________9
DISPLAY BY RADAR _________________10
TACTICAL USE STAGES _________________11
RADAR FREQUENCY BANDS _________________12
APPLICATION _________________13
BIBILIOGRAPHY _________________14
GLOBUS ENGINEERING COLLEGE, BHOPAL
Page 1
BASICS OF RADAR SYSTEM
INTRODUCTION
Radar is a system that uses electromagnetic waves to identify the range,
altitude, direction, or speed of both moving and fixed objects such as
aircraft, ships, motor vehicles, weather formations, and terrain. The term
RADAR was coined in 1941 as an acronym for Radio Detection and
Ranging.
A radar system has a transmitter that emits either microwaves or radio
waves that are reflected by the target and detected by a receiver,
typically in the same location as the transmitter. Although the signal
returned is usually very weak, the signal can be amplified.
Radar can detect static or mobile objects or targets and is the most
effective method for guiding a pilot with regard to his location in space
and also for warning the approach of an enemy plane for similar
purposes.
GLOBUS ENGINEERING COLLEGE, BHOPAL
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HISTORY
• 1904 - Christian Hulsmeyer demonstrated detection of a ship in
dense fog.
• 1917 - Nikola Tesla first established principle for the first
primitive radar units.
• He stated, " by their [standing electromagnetic waves] use we
may produce at will, from a sending station, an electrical effect
in any particular region of the globe; [with which] we may
determine the relative position or course of a moving object,
such as a vessel at sea, the distance traversed by the same, or its
speed." • 1934 - American Dr. Robert M. Page tested the first monopulse
radar.
• 1934 - Soviet military engineer P.K.Oschepkov produced an
experimental apparatus RAPID.
• 1935 - British Robert Watson-Watt demonstrated to his superiors
the capabilities of a working prototype.
GLOBUS ENGINEERING COLLEGE, BHOPAL
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PRINCIPLE OF RADAR
The basis of the radar principle is that if an electromagnetic wave
encounters sudden changes in conductivity σ, permittivity ε or
permeability µ in the medium, a part of the electromagnetic energy gets
absorbed by the second medium and is re-radiated.
The significant change in atomic density between the object and what's
surrounding it will usually scatter radar (radio) waves. This is
particularly true for electrically conductive materials, such as metal and
carbon fiber, making radar particularly well suited to the detection of
aircraft and ships.
Electromagnetic radiation travels in empty space at a speed of 2.998 x
108 metres per second, and in air only slightly less rapidly. This speed is
denoted by the letter c.
GLOBUS ENGINEERING COLLEGE, BHOPAL
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Radar equation
The amount of power Pr returning to the receiving antenna is given by
the radar equation:
Where
Pt = transmitter power
Gt = gain of the transmitting antenna
Ar = effective aperture (area) of the receiving antenna
σ = radar cross section, or scattering coefficient, of the target
F = pattern propagation factor
Rt = distance from the transmitter to the target
Rr = distance from the target to the receiver.
In the common case where the transmitter and the receiver are at the
same location, Rt = Rr and the term Rt² Rr² can be replaced by R4, where
R is the range. This yields:
Maximum Radar Range (Rmax)
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)
GLOBUS ENGINEERING COLLEGE, BHOPAL
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PERIPHERALS OF RADAR
1. ANTENNAS 2. DUPLEXER 3. RADIO FREQUENCY SUBSYSTEM 4. DIGITAL WAVEFORM GENERATOR 5. FREQUENCY SYNTHESIZERS AND OSCILLATORS 6. MIXER 7. POWER AMPLIFIER 8. TRANSMITTER SUBSYSTEM 9. LOW NOISE AMPLIFIER 10. RECEIVER SUBSYSTEM 11. SIGNAL PROCESSING/DATA PROCESSING/CONTROL SUBSYSTEMS 12. ANTENNA POSITIONING SYSTEM 13. POWER SYSTEM
GLOBUS ENGINEERING COLLEGE, BHOPAL
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CLA SSIFICATION
Radar system can be broadly classified into two basic categories-
1. Continuous wave (CW) / Doppler Radars
2. Pulsed Radar
Continuous –Wave Radar
A continuous –Wave Radar transmits a continuous wave signal and is
generally useful in Doppler radars which utilizes the Doppler Effect. If
there is any relative motion between the radar and the target, the shift in
carrier frequency (Doppler Shift) of the reflected wave becomes a
measure of the target’s relative velocity and may be used to distinguish
moving targets from stationary targets. The Doppler Effect can be
experienced while standing near a train track. A change in frequency
(pitch) of the train whistle occurs as the train approaches and then moves
away. There are also radars that combine both of these effects.
Radar using the Doppler Effect principle is known as a Doppler
radar which is useful for navigation over Land Sea through aircraft or
ship.
GLOBUS ENGINEERING COLLEGE, BHOPAL
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Relation to Doppler-Effect
GLOBUS ENGINEERING COLLEGE, BHOPAL
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PULSED RADAR SYSTEM
A radar system is composed of many different subsystems. The
main subsystems were discussed in previous sections. In a pulsed radar
system, there is a portion of time devoted to transmission, and another
portion of time devoted to reception. The transmission time is called the
pulse width. A pulse is transmitted at regular intervals. The repetition
interval is called the pulse repetition interval (PRI). During transmission,
the transmitter produces a waveform. This is passed to the RF system,
through which the waveform is transmitted into the medium of
propagation. When the waveform reaches a target, it is reflected back
towards the radar. By then, the radar system should be in reception
mode. At this time, the reflected echo is intercepted by the RF system.
The echo is then passed to the receiver, which passes it on to the signal
processor. After signal processing, the data processor displays data for
the operator, through the HMI. Power and Control are provided to each
of the subsystems as necessary. The antenna is generally repositioned
after a certain number of pulse transmissions. A schematic of the radar
system is shown in Figure.
GLOBUS ENGINEERING COLLEGE, BHOPAL
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Radar signal processing
Distance measurement
One way to measure the distance to an object is to transmit a short pulse
of radio signal, and measure the time it takes for the reflection to return.
Since radio waves travel at the speed of light (300,000,000 meters per
second), 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 device called a duplexer, the
radar switches between transmitting and receiving at a predetermined
rate. The minimum range is calculated by measuring the length of the
pulse multiplied by the speed of light, divided by two. In order to detect
closer targets one must use a shorter pulse length.
GLOBUS ENGINEERING COLLEGE, BHOPAL
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Display by Radar
GLOBUS ENGINEERING COLLEGE, BHOPAL
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Tactical Use Stages
GLOBUS ENGINEERING COLLEGE, BHOPAL
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Radar frequency bands
The traditional band names originated as code-names during World War
II and are still in military and aviation use throughout the world in the
21st century. They have been adopted in the United States by the IEEE,
and internationally by the ITU. Most countries have additional
regulations to control which parts of each band are available for civilian
or military use.
Other users of the radio spectrum, such as the broadcasting and
electronic countermeasures (ECM) industries, have replaced the
traditional military designations with their own systems
Radar frequency bands
Band
Name
Frequency
Range
Wavelength
Range
Notes
HF 3–30 MHz 10–100 m coastal radar systems, over-the-horizon radar (OTH)
radars; 'high frequency'
P < 300 MHz 1 m+ 'P' for 'previous', applied retrospectively to early
radar systems
VHF 50–330 MHz 0.9–6 m very long range, ground penetrating; 'very high
frequency'
UHF 300–
1000 MHz
0.3–1 m very long range (e.g. ballistic missile early warning),
ground penetrating, foliage penetrating; 'ultra high
frequency'
L 1–2 GHz 15–30 cm long range air traffic control and surveillance; 'L' for
'long'
S 2–4 GHz 7.5–15 cm terminal air traffic control, long-range weather,
marine radar; 'S' for 'short'
C 4–8 GHz 3.75–7.5 cm Satellite transponders; a compromise (hence 'C')
between X and S bands; weather
GLOBUS ENGINEERING COLLEGE, BHOPAL
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APPLICATIONS
Civilian Application
1. Radar altimeters for determining the height of plane above ground.
2. Radar blind lander for aiding aircraft to land under poor visibility, at
night, under adverse weather condition etc.
3. Airborne radar for satellite surveillance.
4. Police radar for directing and detecting speeding vehicles.
5. Radars for determining the speed of moving target, (e.g the speed of a
cricket ball being bowled) automobiles, shells, guided missiles etc.
Military Application
1. Detection ad ranging of enemy target even at night.
2. Aiming guns at aircraft and ships.
3. Bombing ships, aircraft or cities even during overcast or at night.
4. Early warning regarding approaching aircraft or ships.
5. Directing guided missiles.
6. Searching for submarines, land masses and buoys.
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BIBLIOGRAPHY
Microwave & Radar Engineering, by M. Kulkarni.
Available:http://www.icsl.ucla.edu/aagroup/PDF_files/shcourse.PDF
Dao, A., Integrated LNA and Mixer Basics, National Semiconductor,
1993.
http://www.sss-mag.com/pdf/wirlna.pdf.
DC-DC Converter Tutorial, Sunnyvale, CA: Maxim Integrated
Products,2000.
http://www.maximic.com/appnotes.cfm/appnote_number/710.
McPherson, Donald, Receivers/Transmitters. Radar 101 Lecture
Series. Syracuse Research Corporation, Syracuse. 14 Nov. 2001.
Radar Principles, United States Navy Electrical Engineering Training
Series.
http://www.tpub.com/neets/book18/index.htm.
Reintjes, J. Francis and Godfrey T. Coate, Principles of Radar. New
York: McGraw-Hill, 1952.
Schuman, Harvey, Antennas. Radar 101 Lecture Series. Syracuse
Research Corporation, Syracuse. 24 Oct. 2001.
Skolnik, Merrill I., Introduction to Radar Systems. New York:
McGraw-Hill, 1980.
Thomas, Daniel, Signal/Data Processing. Radar 101 Lecture Series.
Syracuse Research h Corporation, Syracuse. 6 Nov. 2001.
