Reader for Students of Radio Engineering Department (Part 2)

Министерство образования и науки Украины Донецкий национальный технический университет Белянская Н. Г., Павлова Л.К., Шкарупа О. Г. Reader for Students of Radio Engineering Department (Part 2) Донецк, ДонНТУ, 2009 Министерство образования и науки Украины Донецкий национальный технический университет Белянская Н. Г., Павлова Л.К., Шкарупа О. Г. Reader for Students of Radio Engineering Department (Part 2) Утверждено на заседании кафедры английского языка протокол № 7 от 16 апреля 2009 Утверждено советом Института Международного Сотрудничества протокол № 11 от 21 апреля 2009 Учебное пособие для студентов третьего и четвертого курсов радиотехнического факультета.(часть 2). Донецк: ДонНТУ, 2009. – 77 стр. Составители: Белянская Н. Г., Павлова Л.К., Шкарупа О. Г. © Донецкий национальный технический университет Введение Данное учебное пособие предназначено для студентов третьего и четвертого курса радиотехнического факультета. Целью учебного пособия является развитие у студентов навыков чтения и понимания оригинальной технической литературы по специальности на 3 и 4 курсах. Также учебное пособие ставит задачу развить у студентов необходимые навыки устного общения на английском языке в объёме материала, предусмотренного программой, умение передать содержание прочитанного на английском языке, а также умение аннотировать и реферировать тексты. С этой целью даны разнообразные упражнения лексического характера, а также упражнения по содержанию текста. Учебного пособия состоит из 12 уроков. Каждый урок включает в себя текст и упражнения. На базе каждого текста разработаны предтекстовые и послетекстовые упражнения, даны технические термины, встречающиеся в тексте, и их перевод на русский язык. Послетекстовые упражнения ставят своей целью снять лексические и смысловые трудности. С целью проверки усвоения материала урока студентам предлагаются упражнения на перевод с русского языка на английский язык, а также упражнения на передачу содержания прочитанного. Авторы надеются, что данное учебное пособие поможет студентам приобрести умения и навыки, необходимые при чтении и понимании технической литературы по специальности. СONTENTS UNIT 1 Radar……………………………………………6 UNIT 2 Principles of Work of Radar……………………10 UNIT 3 Interference…………... ……………………… .16 UNIT 4 Jamming……………………………………… 22 UNIT 5 Distance Measurement………………………….28 UNIT 6 Phased array.........................................................34 UNIT 7 Air Surveillance Radar………………………....39 UNIT 8 Ground Based Radar……………………………44 UNIT 9 Сomponents of Electronic Warfare…………….49 UNIT 10 Electronic countermeasures…………………….54 UNIT 11 Electronic Intelligence………………………….59 UNIT 12 Electromagnetic pulse…………………………..64 GLOSSARY…………………………………………………...69 UNIT 1 Topic: Radar stations Text: Radar List of words: amplify - усилить attenuation – затухание dense fog – густой туман detect – обнаружить determine – определить emit - испускать feasibility – возможность frequency - частота map – нанести на карту precipitation – осадки propagate - распространяться receiver - приемник reflected отраженный shift - сдвиг target - цель transmitter - передатчик visible - видимый weak - слабый Read and translate the text. Radar is a system that uses radio waves to detect, determine the distance or speed, objects such as aircraft, ships, rain and map them. Speed detection is measured by the amount of Doppler Effect frequency shift of the reflected signal. A transmitter emits radio waves, which are reflected by the target, and detected by a receiver, typically in the same location as the transmitter. Although the radio signal returned is usually very small, radio signals can easily be amplified, so radar can detect objects at ranges where other emission, such as sound or visible light, would be too weak to detect. Radar is used in many contexts, including meteorological detection of precipitation, air traffic control, police detection of speeding traffic, and by the military. Several inventors, scientists, and engineers contributed to the development of radar. The use of radio waves to detect "the presence of distant metallic objects via radio waves" was first implemented in 1904 by Christian Hulsmeyer, who demonstrated the feasibility of detecting the presence of ships in dense fog and received a patent for radar as Reichspatent Nr. 165546. Another of the first working models was produced by Hungarian Zoltan Bay in 1936 at the Tungsram laboratory. The term RADAR was coined in 1941 as an acronym for Radio Detection and Ranging. This acronym of American origin replaced the previously used British abbreviation RDF (Radio Direction Finding). The term has since entered the English language as a standard word, radar. A radar system emits powerful pulses of radio waves and listens for any echoes. By analyzing the reflected signal, the reflector can be located and sometimes identified. Although radio waves can be easily generated at any desired strength, the amplitude of the signal returned is usually very small. However, radio signals can easily be detected and amplified many times, so radar is suited to detecting objects at very large ranges where other signals, such as sound or visible light, would be too weak to detect. Radio waves can propagate with less attenuation than light in many conditions, for example, through clouds, fog, or smoke, enabling detection and tracking in conditions that prevent the use of other means. (Source: Златніков В.Г. Практичний курс з вивчення іноземної мови. Київ,2006, стор.179) Ex 1.Answer the questions: 1.What is the function of radar? 2.Where do people use radars? 3.Who contributed to the development of radar? 4.What is the meaning of the acronym radar? 5.What are the principles of working of radars? Ex 2.Give Russian equivalents of the following words and word-combinations. Measure,amount,the same locationl,contribute,coin,replace,strength,identify,range, air traffic control,visible,implement. Ex 3.Use the word in brackets to form a word that fits in the space. 1.The radio signal…..is usually very small.( return) 2.Christian Hulsmeyer demonstrated the feasibility of…..the presence of ships in dense fog.( detect) 3.The reflector can be located by…..the reflected signal.( analyze) 4.Several inventors contributed to the…..of radar.(develop) 5.Radio waves can propagate with less…..than light in many conditions.(attenuate) Ex 4.Match the words with their definitions. word definition 1) propagate a) apparatus for receiving signals 2) transmitter b) create something new 3) radar c) a piece of equipment which emits 4) receiver radio waves 5) source d) electronic impulse in radio,TV,etc 6) frequency e) a system that uses radio waves to 7) invent detect objects 8) signal f) number of repetitions in a given time g) spread more widely h) place from which something comes Ex5.Fill in the gaps with the proper variant. 1. ….. inventors, scientists, and engineers contributed to the development of radar. a)several b)a lot of c)many 2.One of the first working radar models was produced by Zoltan Bay in….. . a)1935 b)1934 c)1936. 3.Speed detection is measured by the amount of Doppler Effect frequency shift of the…..signal . a)sawtooth b)reflected c)remote 4.Radar can detect objects at ranges where other emission, such as sound or visible light, would be too ….. to detect. a)strong b)weak c)powerful 5.The amplitude of the signal returned is usually ….. . a)large b)average c)very small 6.Radio waves can enable detection and tracking in conditions that ….. the use of other means. a)prevent b)favour c)meet Ex 6.Say if the following statements are true or false.Correct the false ones. 1.Radar is a system that uses radio waves for detecting and mapping objects. 2.A transmitter emits radio waves which are reflected by the target and detected by a receiver in the different location as the transmitter. 3.The term RADAR was coined in 1947. 4.A radar system emits powerful pulses of radio waves and listens for any echoes. 5.By analyzing the received signal, the reflector can be located and sometimes identified. 6.Although radio waves can be easily generated at any desired strength, the amplitude of the signal returned is usually very large. 7.Radio waves can’t propagate through clouds,fog,or smoke. Ex 7.Translate into English. 1.Радиоволны, испускаемые передатчиком, отражаются целью и обнаруживаются приемником. 2.Возвращаемый радиосигнал обычно очень слаб. 3.Радар используется в метеорологии, дорожной полицией для определения скорости движения транспорта, в авиации, а также вооруженными силами. 4.Анализируя отраженный сигнал, можно определить местонахождение отражателя. 5.Радиосигналы могут быть легко обнаружены и усилены во много раз. Ex 8.Give a summary of the text. UNIT 2 Topic: Radar stations Text: Principles of Work of Radar List of words: аperture – апертура,щель avoid - избегать bounce off - отпрыгнуть chaff – дипольный отражатель,дипольная помеха chirp - щебетать corner - угол cross section – поперечное сечение decline - снижаться density - плотность edge -край eliminate - край fibre - стекловолокно gain – коэффициент усиления odd looking – необычно выглядящий pathloss – потери на трассе precaution - предосторожность propagation factor – коэффициент передачи scatter - рассеиваться solid - твердый stealth – скрытый surface - поверхность vague – слабый, неясный vehicle – транспортное средство wavelet – малая волна Read and translate the text. Reflection Electromagnetic waves reflect (scatter) from any large change in the dielectric or diamagnetic constants. This means that a solid object in air or vacuum, or other 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 fibre, making radar particularly well suited to the detection of aircraft and ships. Radar absorbing material, containing resistive and sometimes magnetic substances, is used on military vehicles to reduce radar reflection. This is the radio equivalent of painting something a dark colour. Radar waves scatter in a variety of ways depending on the size (wavelength) of the radio wave and the shape of the target. If the wavelength is much shorter than the target's size, the wave will bounce off in a way similar to the way light is reflected by a mirror. If the wavelength is much longer than the size of the target, the target is polarized (positive and negative charges are separated), like a dipole antenna. This is described by Rayleigh scattering, an effect that creates the Earth's blue sky and red sunsets. When the two length scales are comparable, there may be resonances. Early radars used very long wavelengths that were larger than the targets and received a vague signal, whereas some modern systems use shorter wavelengths (a few centimeters or shorter) that can image objects as small as a loaf of bread or smaller. Short radio waves reflect from curves and corners, in a way similar to glint' from a rounded piece of glass. The most reflective targets for short wavelengths have 90° angles between the reflective surfaces. A structure consisting of three flat surfaces meeting at a single corner, like the corner on a box, will always reflect waves entering its opening directly back at the source. These so-called corner reflectors are commonly used as radar reflectors to make otherwise difficult to detect objects easier to detect, and are often found on boats in order to improve their detection in a rescue situation and to reduce collisions. For similar reasons, objects attempting to avoid detection will angle their surfaces in a way to eliminate inside corners and avoid surfaces and edges perpendicular to likely detection directions, which leads to "odd" looking stealth aircraft. These precautions do not completely eliminate reflection because of diffraction, especially at longer wavelengths. Half wavelength long wires or strips of conducting material, such as chaff, are very reflective but do not direct the scattered energy back toward the source. The extent to which an object reflects or scatters radio waves is called its radar cross section. 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 . a = 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: This shows that the received power declines as the fourth power of the range which means that the reflected power from distant targets is very, very small. The equation above with F = 1 is a simplification for vacuum without interference. The propagation factor accounts for the effects of multipath and shadowing and depends on the details of the environment. In a real-world situation, pathloss effects should also be considered. Other mathematical developments in radar signal processing include time-frequency analysis as well as the chirplet transform which makes use of the fact that radar returns from moving targets typically "chirp" (change their frequency as a function of time, as does the sound of a bird or bat). (Source: Златніков В.Г. Практичний курс з вивчення іноземної мови. Київ,2006, стор.182) Ex 1.Answer the questions: 1.What does usually scatter radar (radio) waves? 2.What material is used to reduce radar reflection? 3.What does radar waves scattering depend on? 4.What is the difference between early and modern radars? 5.What are corner reflectors used for? 6.What is radar equation used for?

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