Unit 6 An antenna

1. Match the English words and phrases with their Ukrainian equivalents.

1) a transducer a) провідник

2) transmit or receive b)електромагнітне випромінювання

3) electromagnetic radiation c) передбачене теорією

4) radioequipment d) передача

5) wireless e) антена

6) for short distances f) підключити до терміналу

7) conductor g) перетворювач

8) in transmission h) радіообладнання

9) an aerial i) безпровідний

10) connect to the terminal j) передавати або приймати

11) predicted by the theory k) на короткі відстані

2. Translate the following groups of words of the same root. Choose 6-8 words and make your own sentences:

industry — industrial; to invent — inventor — invention; to detect — detection; to measure —measurement— measurable; to combine — combination; to achieve — achievement; to apply — application — applicable; to vibrate — vibration; frequency — frequently; to distinguish — distinguished; to use —usage — useful — useless; to compare — comparison — comparative; to succeed — success — successful; to explain— explanation; to pass — passage; to machine — machine.

3. Translate the following words and word combinations into English. Choose 4-5 words and make your own sentences:

електромагнітне випромінювання, космічний простір, електричний струм, провідник, двосторонній радіозв'язок, засвідчувати існування, елементарна антена, приймач (датчик), радіоканал, пристрій, гранична напруга, робочі канали, передача даних зі швидкістю, чутливiсть приймача, потужнiсть передавача.

4. Match up the words in column a with the words in column b to form meaningful phrases, translate them into Ukrainian.

Column A Column B

1. the speed of a) elements

2. electromagnetic b) aerial element

3. oscillating current of c) light

4. magnetic d) the electrons

5. antenna e) waves

6. wireless computer f) field

7. receiving g) all equipment

8. the power of h) electrons

9. essential components of j) an electromagnetic wave

10. the charge of i) networks

5. Read the text and translate it into Ukrainian.Use a dictionary if necessary. An antenna

An antenna is a transducer that transmits or receives electromagnetic waves. Antennas convert electromagnetic radiation into electric current, or vice versa. Antennas generally deal in the transmission and reception of radio waves, and are a necessary part of all radio equipment. Antennas are used in systems such as radio and television broadcasting, point-to-point radio communication, wireless LAN, cell phones, radar, and spacecraft communication. Antennas are employed in air or outer space, but can also be operated under water or even through soil and rock at certain frequencies for short distances.

An antenna is an arrangement of one or more conductors. In transmission, an alternating current is created in the elements by applying a voltage at the antenna terminals, causing the elements to radiate an electromagnetic field. In reception, the inverse occurs: an electromagnetic field from another source induces an alternating current in the elements and a corresponding voltage at the antenna's terminals. Some receiving antennas (parabolic, horn) incorporate shaped reflective surfaces to collect the radio waves striking them and direct or focus them onto the actual conductive elements.

The first rudimentary antennas were built in 1888 by Heinrich Hertz in his pioneering experiments to prove the existence of electromagnetic waves predicted by the theory of James Clerk Maxwell. Hertz placed the emitter dipole in the focal point of a parabolic reflector. The words antenna and aerial are used interchangeably; but usually a rigid metallic structure is termed an antenna and a wire format is called an aerial. A Hertzian antenna is a set of terminals that does not require the presence of a ground for its operation. A loaded antenna is an active antenna having an elongated portion of appreciable electrical length and having additional inductance or capacitance directly in series or shunt with the elongated portion so as to modify the standing wave pattern existing along the portion or to change the effective electrical length of the portion. An antenna grounding structure is a structure for establishing a reference potential level for operating the active antenna. It can be any structure closely associated with the ground which is connected to the terminal of the signal receiver or source opposing the active antenna terminal. There are two fundamental types of antenna directional patterns, which, with reference to a specific two dimensional plane or vertical.

The bandwidth of an antenna is the range of frequencies over which it is effective, usually centered on the resonant frequency. The bandwidth of an antenna may be increased by several techniques, including using thicker wires, replacing wires with cages to simulate a thicker wire, tapering antenna components (like in a feed horn), and combining multiple antennas into a single assembly and allowing the natural impedance to select the correct antenna. Small antennas are usually preferred for convenience, but there is a fundamental limit relating bandwidth, size and efficiency. The polarization of an antenna is the orientation of the electric field of the radio wave with respect to the Earth's surface and is determined by the physical structure of the antenna and by its orientation. It has nothing in common with antenna directionality terms: "horizontal", "vertical" and "circular". Thus, a simple straight wire antenna will have one polarization when mounted vertically, and a different polarization when mounted horizontally.

There are many variations of antennas. The isotropic radiator is a purely theoretical antenna that radiates equally in all directions. It is considered to be a point in space with no dimensions and no mass. The dipole antenna is simply two wires pointed in opposite directions arranged either horizontally or vertically, with one end of each wire connected to the radio and the other end hanging free in space. The Yagi-Uda antenna is a directional variation of the dipole with parasitic elements added which are functionality similar to adding a reflector and lenses (directors) to focus a filament light bulb. The random wire antenna is simply a very long wire with one end connected to the radio and the other in free space, arranged in any way most convenient for the space available. The horn is used where high gain is needed, the wavelength is short (microwave) and space is not an issue. Horns can be narrow band or wide band, depending on their shape. The parabolic antenna consists of an active element at the focus of a parabolic reflector to reflect the waves into a plane wave. Like the horn it is used for high gain, microwave applications, such as satellite dishes. The patch antenna consists mainly of a square conductor mounted over a groundplane. Another example of a planar antenna is the tapered slot antenna (TSA), as the Vivaldi-antenna.