Focused Practice

I. Answer the following questions:

1. How do the antenna of a handset and a base-station antenna differ?

2. Why does a handset that is in operation have a low frequency magnetic field?

3. What does the amount of heating produced in a living organism depend on?

4. In what cases is the frequency o the radiation taken into account?

5. Why does the possibility that MWR currently used in GSM mobile telephony can exert subtle non-thermal influences on a living organism arise?

6. What do the biological electrical activities that are vulnerable to interference from GSM radiation include?

II. Analyse the grammar structures under lined in the above text.

III. Speak on: Biological effects of mobile telephony.

SECTION VI

Measuring technique and equipment

Unit 54

Grammar: The Participle. The Attribute

Word List:

1. analog analyzer	аналоговый анализатор
2. network analyzer	анализатор сети
3. signal analyzer	анализатор сигналов
4. LCR-meter	измеритель индуктивности, ёмкости и сопротивления
5. spectrum analyzer	анализатор спектра
6. DSP technology – Digital Signal Processing technology	цифровая обработка сигналов
7. intermediate frequency	промежуточная частота
8. down conversion	понижение частоты, преобразование «вниз»
9. duplexer	антенный переключатель
10. copler	направленный ответвитель
11. attenuator	аттенюатор, ослабитель
12. port	порт (выход/вход)
13. impedance	импеданс, полное входное сопротивление
14. transfer function	передаточная характеристика
15. RF-radio frequency	радиочастота
16. microwaves	СВЧ волны
17. optical frequencies	частоты оптического диапазона
18. directly digitizing signals	прямая оцифровка сигналов
19. linear range	линейная область

Signal and Network Analyzers Span the Spectrum from Audio to Light

Analog analyzers fit into two broad categories – network analyzers, which characterize impedances and transfer functions, and signal analyzers, which characterize signal properties. Network analyzers comprise vector and scalar units, as well as impedance, resistance, and LCR meters. Signal analyzers are even more diverse, including at least a dozen instrument types. Spectrum analyzers are among the instruments in the signal-analyzer category. Based on the dollar volume of sales they generate, spectrum analyzers are by far the most important analog signal analyzers.

Despite their importance at RF, microwave, and optical frequencies, analog signal and network analyzers include several instrument types that operate at much lower – even subsonic – frequencies. Today, most of these low-frequency instruments are based on DSP technology.

DSP can also extend the capabilities of higher frequency analyzers. Directly digitizing signals above approximately 1 GHz is still beyond the state of the art, however. So, most high-frequency analyzers that use DSP digitize signals only after translating them to a lower intermediate frequency. The translation, called “down-conversion”, involves mixing the unknown signal with a locally generated signal at a slightly different frequency.

Network analyzers characterize the (frequency-dependent) impedance or scattering parameters of active and passive networks, such as amplifiers, mixers, duplexers, filters, couplers, attenuators, and many other system components. The networks can have one port (input or output) or many ports.

In general, if you know the input characteristics of each of a component’s ports and the transfer characteristics from any port to each of the others, you have the information you need to use the component in a high-frequency system, such as a radar or communications system. In most cases, you make measurements on active components, such as amplifiers, in their linear range. Nonlinear components usually require signal analyzers to determine distortion performance.