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Exercise 2exercise exercise
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Read and translate the international words:
Apparatus, system, channel, amplitude, modulation, unit, generators, electric filter, differential, limiter, compressors, correction, terminal, element, diode, transistor, transfer, spectrum, area, heterodyne, detector, receiver, conversion, process, principle of modulation, periodically, characteristics, radio, integrated, ordinary, balanced, crystal, professional, decameter, bipolar, unipolar, isolation, type.
EXERCISE 3
Find the Russian equivalents to the following words and word combinations in the box
| Multichannel system, frequency division of channels, amplitude modulation, a number of various devices, frequency converter, amplifier, differential system, amplitude limiter, electric filter, correction circuit, frequency spectrum, super heterodyne detector, intermediate frequency, diode, super high frequency, low noises, bipolar transistor, unipolar transistor, non-balanced converter, double balanced converter. |
Амплитудная модуляция, многоканальная система, преобразователь частоты, ограничитель амплитуд, множество различных устройств, биполярный транзистор, полевой транзистор, частотное разделение каналов, усилитель, промежуточная частота, СВЧ, выравнивающий контур, спектр частот, супергетеродинный приемник, электрический фильтр, диод, дифференциальная система, малые шумы, двойной балансный преобразователь, небалансный преобразователь.
EXERCISE 4
Read and translate the text using words and word combinations.
Words and word combinations to be remembered:
Thin-route systems – малоканальная система
unit – узел аппаратуры
transceiving devices – устройство приема и передачи сигналов
range extenders – сжиматель диапазона
range compressors –ограничитель диапазона
delineation circuits – выравнивающий контур
terminal units – оконечная аппаратура
nonlinear elements - нелинейные элементы
dead – пассивный
semiconductor –полупроводник
amplification – усиление
frequency spectrum transfer – перенос спектра частот
upwards / downwards – вверх/ вниз
fluctuation-carrier frequency – частота несущего колебания
at the output of the converter – на выходе преобразователя
line circuits with periodically changing characteristics – линейные цепи с периодически меняющимися параметрами
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integrated – интегральный
ordinary – простой
balanced - балансный
ring – кольцевой
unipolar –полевой
circuit isolation – развязка между цепями
Frequency converters
Apparatuses on multichannel and thin-route systems with frequency division of channels and amplitude modulation are comprised into a number of various devices commonly called units. Main units of a multichannel system with frequency division of channels and amplitude modulation are frequency converters, amplifiers, generators, electric filters and several special units – differential systems, transceiving devices, amplitude limiters, range extenders and range compressors, delineation circuits and correction circuits.
Frequency converters are one of the most important terminal units because they are the very devices to create multichannel systems with frequency division of channels and amplitude modulation. For this purpose in the converters there are used nonlinear elements: dead (semiconductor diodes) and active (transistors). There are also used frequency converters with electron tubes which help to obtain greater signal amplification.
Frequency converters are used to transfer frequency spectrum from one area into another. They are part of super heterodyne detector (a frequency converting receiver). The result of conversion is a new frequency value f called intermediate value. The intermediate frequency can be both higher and lower than signal frequency. In the first case the frequency conversion is upwards, in the other case it is downwards. In this process the frequency conversion principle of modulation is not broken, only fluctuation-carrier frequency is changed at the output of the converter.
To convert frequency there are used line circuits with periodically changing characteristics in radio receivers. The structural circuit consists of a converting element, heterodyne and filter. According to the type of a converting element the frequency converters are usually divided into diode, transistor and integrated converters. There is a different number of converting elements, so one can find the following types of converters: ordinary (with one converting element), balanced (two elements), and ring (4 elements).
Most SHF (super high frequency) receivers use crystal diodes as converting element. Crystals have fast response and comparatively low noises. But they have a drawback - they don’t have amplifying properties. Such converters are used in professional devices of decameter range.
Transistor converters use bipolar transistor, or unipolar transistor as converting element. Balanced converters are combination of two non-balanced converters. To increase channel isolation between a signal and a heterodyne there are used double balanced converters called ring converters. Such type converters have low noises and better amplitude characteristics. They are used in frequency range up to 100 MHz in professional decameter devices.
EXERCISE 5
Scan the text again and count how many times the words ‘converter’ and ‘amplitude modulation’ are used in different combinations. Also give 5 verbs, 5 adverbs and 5 nouns concerning the subject of the text. What verb is met in the text most often? In what voice?
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EXERCISE 6
Answer the questions about the text:
1. What units can be called the main units of a multichannel system?
2. Which elements are used in frequency converters?
3. Which other elements, beside non-linear are enabled in communication apparatuses? What is their advantage?
4. Why do radio engineers need frequency converters?
5. What is changed with the help of the frequency converters?
6. What elements does the circuit of a FC (frequency converter) consist of?
7. What types of FC can you name?
EXERCISE 7
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