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5. Answer the following questions:

1. What do antennas convert into electric current? 2. In what systems are antennas used? 3. How many fundamental types of antenna are there? 4. What is grounding structure of antenna? 5. How many variations of antennas are there? 6 Where is the horn used? 7. Where is the parabolic antenna used? 8. What is a bandwidth? 9. Does a Hertzian antenna require the presence of a ground for its operation?

6. Match the first part (1-7) of the sentence with the second part (a-g):

1. The isotropic radiator is

2. The dipole antenna is

3. The Yagi-Uda antenna is

4. The random wire antenna is

5. The horn is

6. The parabolic antenna

7. The patch antenna is

a) used where high gain is needed, the wavelength is short (microwave) and space is not an issue.

b) a radio frequency antenna consisting of a wire whose length does not bear a relation to the wavelength of the radio waves used, but is typically chosen more for convenience.

c) a popular antenna type, consists of a square conductor mounted over a groundplane.

d) a radio antenna that can be made by a simple wire, with a center-fed driven element.

e) a theoretical point source of waves which exhibits the same magnitude or properties when measured in all directions.

f) a directional antenna system consisting of an array of a dipole and additional closely coupled parasitic elements.

g) a high-gain reflector antenna used for radio, television and data communications, and also for radiolocation (radar).

7. Read the supplementary text, translate and entitle it:

A parabolic antenna is an antenna that uses a parabolic reflector, a surface with the cross-sectional shape of a parabola, to direct the radio waves. The most common form is shaped like a dish and is popularly called a dish antenna or parabolic dish. The main advantage of a parabolic antenna is that it is highly directive; it functions analogously to a searchlight or flashlight reflector to direct the radio waves in a narrow beam, or receive radio waves from one particular direction only. Parabolic antennas have some of the highest gains, that is they can produce the narrowest beam width angles, of any antenna type. They are used as high-gain antennas for point-to-point radio, television and data communications, and also for radiolocation (radar), on the UHF and microwave (SHF) parts of the radio spectrum. The relatively short wavelength of electromagnetic radiation at these frequencies allows reasonably sized reflectors to exhibit the desired highly directional response. With the advent of TVRO and DBS satellite television dishes, parabolic antennas have become a ubiquitous feature of the modern landscape. They are also widely used for terrestrial microwave relay links, ground based and airborne radar antennas, wireless WAN/LAN links, satellite and spacecraft communication antennas, and radio telescopes.