Radar :Radio Detection and Ranging Seminar report

SEMINAR REPORT On BASICS OF RADAR SYSTEM

SUBMITTED TOMr. LALIT JAIN Dept. of Electronics GEC, BHOPAL

GLOBUS ENGINEERING COLLEGE, BHOPAL

SUBMITTED BYRAVINDRA MATHANKER [0130ec071046] AKIB KHAN

[0130ec071004]

E.C. 4th sem. GEC, 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)


TABLE OF CONTENT  INTRODUCTION

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 HISTORY

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 PRINCIPLE OF RADAR

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 RADAR EQUATION

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 PERIPHERALS OF RADAR

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 CLASSIFICATION

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 RELATION TO DOPPLER EFFECT_________________7  PULSED RADAR SYSTEM

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 RADAR SIGNAL PROCESSING __________________9  DISPLAY BY RADAR

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 TACTICAL USE STAGES

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 RADAR FREQUENCY BANDS _________________12  APPLICATION

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 BIBILIOGRAPHY

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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.


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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.


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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.


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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)


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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


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CLA SSIFICATION Radar system can be broadly classified into two basic categories1. 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.


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Relation to Doppler-Effect


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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.


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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.


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Display by Radar


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Tactical Use Stages


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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


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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.


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Radar :Radio Detection and Ranging Seminar report

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