Antenna and Microwave Engineering MCQs with answers Page - 6

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Q. What is the beam width for a half wave dipole antenna?

• (A) 90°
• (B) 180°
• (C) 50°
• (D) 250°

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Correct answer - Option (A)

Explanation:

the beam width is measured between the points on the radiation curve that are 3 db down from the maximum amplitude of the curve. the maximum amplitude of the pattern occurs at 0° and 180°. the 3-db down points are 70.7 percent of the maximum. the angle formed with two lines extending from the center of the curve to these 3-db points is the beam width. the beam width is 90°. the smaller the beam width angle, the more directional the antenna.

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Q. What does the beam width of an antenna tell us?

• (A) signal strength
• (B) signal power
• (C) directivity
• (D) degradation

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Correct answer - Option (C)

Explanation:

the measure of an antenna’s directivity is beam width, the angle of the radiation pattern over which a transmitter’s

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Q. What is the power radiated by the antenna with gain called as?

• (A) critical power
• (B) transverse power
• (C) effective radiated power
• (D) transmitted power

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Correct answer - Option (C)

Explanation:

the power radiated by an antenna with directivity and therefore gain is called the effective radiated power (erp).

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Q. What is the radiation pattern of an isotropic radiator?

• (A) doughnut
• (B) sphere
• (C) hemisphere
• (D) circular

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Correct answer - Option (B)

Explanation:

an isotropic radiator is a theoretical point source of electromagnetic energy. the e and h fields radiate out in all directions from the point source, and at any given distance from the point source, the fields form a sphere.

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Q. What is the impedance of the folded dipole antenna?

• (A) 50Ω
• (B) 100Ω
• (C) 300Ω
• (D) 20Ω

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Correct answer - Option (C)

Explanation:

a popular variation of the half- wave dipole is the folded dipole. like the standard dipole, it is one-half wavelength long. however, it consists of two parallel conductors connected at the ends with one side open at the center for connection to the transmission line. the impedance of this

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Q. Which of the following antennas produce a vertical radiation pattern?

• (A) dipole antenna
• (B) yagi antenna
• (C) marconi antenna
• (D) hertz antenna

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Correct answer - Option (C)

Explanation:

the same effect as dipole antenna can be achieved with a one-quarter wavelength antenna or marconi antenna. a vertical dipole with the doughnut-shaped radiation pattern, in which one-half of the pattern is below the surface of the earth. this is called a vertical radiation pattern.

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Q. The members of the antenna family which are made of wires of certain value in terms of operating wavelength are called:

• (A) loop antennas
• (B) wire antennas
• (C) dipole antenna
• (D) slot antennas

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Correct answer - Option (C)

Explanation:

wires of half wavelength are termed as dipoles. their radiation resistance is about 73 Ω. if only half of this length is used, then it is called quarter-wave monopole with a radiation resistance of 36.5 Ω.

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Q. The antenna in which location of the feed determines the direction of the lobe are:

• (A) wire antenna
• (B) loop antenna
• (C) helical antenna
• (D) horn antenna

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Correct answer - Option (A)

Explanation:

in a wire antenna, the location of the feed determines the direction of the lobe and the orientation of the wire determines the polarization. these wires can be thick or thin. thickness of the wire determines the radiation resistance of the antenna.

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Q. Based on the size of the loops, loop antennas are classified as small and large loops. This is the only classification of loop antenna.

• (A) true
• (B) false
• (C) ---
• (D) ---

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Correct answer - Option (B)

Explanation:

loop antennas are classified based on various antenna parameters. to name a few, small and large loops, circular and square loops, loops having single or multi turns, loops with turns wound using a single wire or multiple wires.

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Q. Antenna that does not belong to the horn antenna family among the following are:

• (A) pyramidal horn
• (B) conical horn
• (C) bi-conical horn
• (D) none of the mentioned

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Correct answer - Option (D)

Explanation:

all of the above mentioned antennas belong to the horn antenna family. horn antennas may be made of pointed or rounded waveguides. the waveguides may contain disc at an end or some dielectric.

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