1. system, a, has, radar, a, emits, that, transmitter, radio, waves

2. signal, amplified, returned, radio, the, be, can

3. contexts, in, is, many, radar, used

4. used, long, early, wavelengths, very, radars

5. object, extent, to, which, an, reflects, the, called, waves, is, its, radio, cross, radar, section

   11. Make up questions to words in italics:

       1. Some clutter may also be caused by a long radar waveguide between the radar transceiver and the antenna.

       2. Radar jamming refers to radio signals originating from sources outside the radar.

       3. Random polarization returns usually indicate a fractal surface.

       4. Radar systems must overcome different sources of unwanted signals.

       5. In the transmitter radar signal, the electric field is perpendicular to the direction of propagation.

   12. State whether the following statement are true or false. Use only evidence from the text.

       1. The term "radar" was coined in 1941 as an acronym for Radio Direction Finder.

       2. Radar is not used in meteorological detection of precipitation.

       3. Radars use horizontal, vertical, linear and circular polarization to detect different types of reflection.

       4. The ability of the radar system to overcome unwanted signals defines its signal-to-noise ratio.

       5. Signal noise is an external source of random variations in the signal.

XIII. Match the words and word - combinations from text 13a with their corresponding defini­tions:

1. radar cross section a. the ratio of a signal power to the noise

2. radar jamming power within the desired signal

3. signal - to - noise ratio b. an internal source of random variations in

4. clutter the signal generated by electronic com-

5. signal noise ponents

   100. the extent to which an object reflects radio waves

        4. radio frequency signals originating from sources outside the radar, transmitting in the radar's fre­quency and masking targets of interest

        5. actual radio frequency echoes returned from tar­gets uninteresting to the radar operators

14. Translate the following two-component and multicomponent terms into Ukrainian: dipole antenna, magnetic polarization, at random, unwanted signal, radar detector, signal-to-noise ra­tio, radio detection and ranging, radio direction finder, surface wave, dielectric constant, corner reflec­tor, radar jamming.

15. /

    Make up a plan of text 13A.

16. Annotate text 13a.

XVII. Retell text 13a.

Text 13B. Radar components

• надшрний шум

• фоновий шум

• батарея конденсатов

• неробочш перюд

• 1 .робочш цикл; 2. коефщент заповнення для по-

отдовносп 1мпульс1в

• цикл передач!

• послщовшсть iMnynbcie

• антенний перемикач

• перемютитися в початкове положения

• Notes:

  1. excessive noise

  2. background noise

  3. capacitor bank

  4. rest time

  5. duty cycle

  6. transmission cycle

  7. pulse train

  8. duplexer switch

  9. shift back

  10. vertical axis

  11. top-down view

  вертикальна вюь

• Transmitter

  перевериуте зображення

A practical radar system requires seven basic components as illustrated below:

Synchronizer

Duplexer Switch

Power Supply

Receiver

Display

Antennas

Transmitter. The transmitter creates the radio wave to be sent and modulates it to form the pulse train. The transmitter must also amplify the signal to a high power level to provide adequate range. The source of the carrier wave could be a Klystron, Traveling Wave Tube (TWT) or Magnetron. Each has its own characteristics and limitations.

Receiver. The receiver is sensitive to the range of frequencies being transmitted and provides amplifi­cation of the returned signal. In order to provide the greatest range, the receiver must be very sensitive without introducing excessive noise. The ability to discern a received signal from background noise depends on the signal-to-noise ratio (S/N).

Power Supply. The power supply provides the electrical power for all the components. The largest consumer of power is the transmitter which may require several kW of average power. The actual power transmitted in the pulse may be much greater than 1 kW. The power supply only needs to be able to provide the average amount of power consumed, not the high power level during the actual pulse transmission. Energy can be stored, in a capacitor bank for instance, during the rest time. The stored energy then can be put into the pulse when transmitted, increasing the peak power. The peak power and the average power are related by the quantity called duty cycle, DC. Duty cycle is the frac­tion of each transmission cycle that the radar is actually transmitting.

Synchronizer. The synchronizer coordinates the timing for range determination. It regulates that rate at which pulses are sent (i.e. sets PRF) and resets the timing clock for range determination for each pulse. Signals from the synchronizer are sent simultaneously to the transmitter, which send a new pulse, and to the display, which resets the return sweep.

Duplexer. This is a switch which alternately connects the transmitter or receiver to the antenna. Its purpose is to protect the receiver from the high power output of the transmitter. During the transmis­sion of an outgoing pulse, the duplexer will be aligned to the transmitter for the duration of the pulse, PW. After the pulse has been sent, the duplexer will align the antenna to the receiver. When the next pulse is sent, the duplexer will shift back to the transmitter. A duplexer is not required if the transmit­ted power is low.

Antenna. The antenna takes the radar pulse from the transmitter and puts it into the air. Furthermore, the antenna must focus the energy into a well-defined beam which increases the power and permits a determination of the direction of the target. The antenna must keep track of its own orientation which can be accomplished by a synchro-transmitter. There are also antenna systems which do not physically move but are steered electronically (in these cases, the orientation of the radar beam is known a pri­ori). The beam-width of an antenna is a measure of the angular extent of the most powerful portion of the radiated energy.

Display. The display unit may take a variety of forms but in general is designed to present the received information to an operator. The most basic display type is called an A-scan (amplitude vs. Time de­lay). The vertical axis is the strength of the return and the horizontal axis is the time delay, or range. The A-scan provides no information about the direction of the target.

The most common display is the PPI (plan position indicator). The A-scan information is converted into brightness and then displayed in the same relative direction as the antenna orientation. The result is a top — down view of the situation where range is the distance from the origin. The PPI is perhaps the most natural display for the operator and therefore the most widely used. In both cases, the syn­chronizer resets the trace for each pulse.