Radiotechnical Communication Components. Радиотехнические средства связи. Учебное пособие

3.able

4.complex

5.dense

6.electric

7.intense

8.conductive

9.capable

10.special

11.flexible

Grammar

8. Translate into Russian the following sentences paying attention to Gerund constructions and their syntactic functions.

1.It was not until April 1961 that the world learnt about the first orbital flight made by Soviet cosmonaut Yuri Gagarin.

2.It was not until March 1966 that the first docking of one space vehicle with another was carried out but failed.

3.It was not until 1968 that the first command service module landed on the Moon and sent views of lunar surface to the Earth.

4.It was not until May 1969 that the first lunar landing was made by American astronauts Armstrong and Aldrin who collected soil and rock samples. They were reported to have stayed on the Moon 21 h 36 min.

5.It was not until June 1963 that the first woman cosmonaut Valentina Tereshkova orbited the Earth.

6.It was not until the 16th century that the English discovered large deposits of pure graphite.

7.It was not until 1779 that Swedish chemist Carl Scheele realized that graphite is a variety of carbon.

8.It was not until the end of the 19th century that German geologist Gottlob Werner gave the newly discovered substance a more appropriate name – graphite.

9.It was not until the 1950s and 1960s that over-the-horizon radar systems were developed and used as a part of early warning systems.

10.The U.S. Department of Defence was developing the Global Positioning System in the 1970s. But it was not until 1978 that the first GPS satellite was launched.

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Speaking

9.Write the plan of the text "Basic Parts of a Radar". Retell the text.

Writing

10.Write the summary of the text "Radar Application".

Lesson 3. Types of Radars

Preview

Before you read

1.What is the main function of radars?

2.What do you know about various types of radars?

Vocabulary

Reading

1. Read the text.

Types of Radars

Although there is no single way to characterize a radar, here we do so by means of what might be the major feature that distinguishes one type of radar from another.

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Pulse radar.

This is a radar that radiates a repetitive series of almost-rectangular pulses. It might be called the canonical form of a radar, the one usually thought of as a radar when nothing else is said to define a radar.

High-resolution radar.

High resolution can be obtained in the range, angle, or Doppler velocity coordinates, but high resolution usually implies that the radar has high range resolution. Some high-resolution radars have range resolutions in terms of fractions of a meter, but it can be as small as a few centimeters.

Pulse compression radar.

This is a radar that uses a long pulse with internal modulation (usually frequency or phase modulation) to obtain the energy of a long pulse with the resolution of a short pulse.

Continuous wave (CW) radar. This radar employs a continuous sine wave. It almost always uses the Doppler frequency shift for detecting moving targets or for measuring the relative velocity of a target.

FM-CW radar.

This CW radar uses frequency modulation of the waveform to allow a range measurement.

Surveillance radar.

Although a dictionary might not define surveillance this way, a surveillance radar is one that detects the presence of a target (such as an aircraft or a ship) and determines its location in range and angle. It can also observe the target over a period of time so as to obtain its track.

Moving target indication (MTI).

This is a pulse radar that detects moving targets in clutter by using a low pulse repetition frequency (PRF) that usually has no range ambiguities. It does have ambiguities in the Doppler domain that result in so-called blind speeds.

Pulse Doppler radar.

There are two types of pulse Doppler radars that employ either a high or medium PRF pulse radar. They both use the Doppler frequency shift to extract moving targets in clutter. A high PRF pulse Doppler radar has no ambiguities (blind speeds) in Doppler, but it does have range ambiguities. A medium PRF pulse Doppler radar has ambiguities in both range and Doppler.

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Tracking radar.

This is a radar that provides the track, or trajectory, of a target. Tracking radars can be further delineated as STT, ADT, TWS, and phased array trackers as described below.

Single Target Tracker (STT).

Tracks a single target at a data rate high enough to provide accurate tracking of a maneuvering target. A revisit time of 0.1 s (data rate of 10 measurements per second) might be "typical." It might employ the monopulse tracking method for accurate tracking information in the angle coordinate.

Automatic detection and tracking (ADT).

This is tracking performed by a surveillance radar. It can have a very large number of targets in track by using the measurements of target locations obtained over multiple scans of the antenna. Its data rate is not as high as the STT. Revisit times might range from one to 12 sec, depending on the application.

Track-while-scan (TWS).

Usually a radar that provides surveillance over a narrow region of angle in one or two dimensions, so as to provide at a rapid update rate location information on all targets within a limited angular region of observation. It has been used in the past for ground-based radars that guide aircraft to a landing, in some types of weapon-control radars, and in some military airborne radars.

Phased array tracker.

An electronically scanned phased array can (almost) "continuously" track more than one target at a high data rate. It can also simultaneously provide the lower data rate tracking of multiple targets similar to that performed by ADT.

Imaging radar.

This radar produces a two-dimensional image of a target or a scene, such as a portion of the surface of the earth and what is on it. These radars usually are on moving platforms.

Sidelooking airborne radar (SLAR).

This airborne sidelooking imaging radar provides high resolution in range and obtains suitable resolution in angle by using a narrow beamwidth antenna.

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Synthetic aperture radar (SAR).

SAR is a coherent imaging radar on a moving vehicle that uses the phase information of the echo signal to obtain an image of a scene with high resolution in both range and cross-range. High range resolution is often obtained using pulse compression.

Inverse synthetic aperture radar (ISAR).

IS AR is a coherent imaging radar that uses high resolution in range and the relative motion of the target to obtain high resolution in the Doppler domain that allows resolution in the cross-range dimension to be obtained. It can be on a moving vehicle or it can be stationary.

Weapon control radar.

This name is usually applied to a single-target tracker used for defending against air attack.

Guidance radar.

This is usually a radar on a missile that allows the missile to "home in," or guide itself, to a target.

Weather (meteorological) observation.

Such radars detect, recognize, and measure precipitation rate, wind speed and direction, and observe other weather effects important for meteorological purposes. These may be special radars or another function of surveillance radars.

Doppler weather radar.

This is a weather observation radar that employs the doppler frequency shift caused by moving weather effects to determine the wind; the wind shear (when the wind blows in different directions), which can indicate a dangerous weather condition such as a tornado or a downburst of wind; as well as other meteorological effects.

Target recognition.

In some cases, it might be important to recognize the type of target being observed by radar (e.g., an automobile rather than a bird), or to recognize the particular type of target (an automobile rather than a track, or a starling rather than a sparrow), or to recognize one class of target from another (a cruise ship rather than a tanker). When used for military purposes, it is usually called a non cooperative target recognition (NCTR) radar, as compared to a cooperative recognition system such as IFF (identification friend or foe), which is not a radar. When target recognition involves some part of the natural environment, the radar is usually known as a remote sensing (of the environment) radar.

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Multifunction radar.

If each of the above radars were thought of as providing some radar function, then a multifunction radar is one designed to perform more than one such function–usually performing one function at a time on a timeshared basis.

There are many other ways to describe radars, including land, sea, airborne, space-borne, mobile, transportable, air-traffic control, military, ground-penetrating, ultra-wideband, over the horizon, instrumentation, laser (or lidar), by the frequency band at which they operate (UHF, L, S, and so on), by their application, and so forth.

After-reading tasks

2. Answer the questions.

1.What does a pulse radar radiate?

2.What does a high resolution usually imply?

3.Which type of a radar uses a long pulse with internal modulation?

4.What kind of a radar employs a continuous sine wave?

5.Which type of a radar uses the phase information of the echo signal to obtain an image of a scene with high resolution in both range and crossrange?

6.What mechanisms does Doppler weather radar employ?

7.Which type of a radar is designed to perform more than one such function?

8.What type of a radar is mostly used for military purposes?

3. Translate the sentences from English into Russian.

1.A pulse radar might be called the canonical form of a radar.

2.A guidance radar is usually a radar on a missile that allows the missile to "home in," or guide itself, to a target.

3.Inverse synthetic aperture radar can be on a moving vehicle or it can be stationary.

4.In some cases, it might be important to recognize the type of target being observed by radar.

5.A phased array tracker is an electronically scanned phased array that can (almost) "continuously" track more than one target at a high data rate.

6.An airborne sidelooking imaging radar provides high resolution in range and obtains suitable resolution in angle by using a narrow beamwidth antenna.

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Speaking

4.Make the outline of the text. Speak about various types of radars and their functions.

5.Prepare a presentation about some types of radars that are particularly interesting to you, prove their importance and advantages.

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