Antenna and Microwave Engineering MCQs with answers Page - 2

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Q. The number of patterns radiation pattern required to specify the characteristic are :

• (A) three
• (B) four
• (C) two
• (D) five

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Correct answer - Option (A)

Explanation:

the three patterns required are, θ component of the electric field as the function of the angles as θ and φ, the φ component of the electric field as the function of the angles θ and φ, the phase of these fields as a functions of the angle φ and θ .

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Q. The beam width of the antenna pattern measured at half power points is called:

• (A) half power beam width
• (B) full null beam width
• (C) beam width
• (D) none of the mentioned

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Correct answer - Option (A)

Explanation:

the beam width of an antenna measure at half of the maximum power received by an antenna or the 3 db beam width of the antenna is termed as half null beam width.

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Q. An antenna has a field pattern E (θ) =cos θ. cos 2θ. The first null beam width of the antenna is:

• (A) 450
• (B) 900
• (C) 1800
• (D) 1200

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Correct answer - Option (B)

Explanation:

half power beam width of the antenna is obtained by equating the field pattern of the antenna to 0.707 (half power point) and finding θ. 2θ gives the value of beam width. twice the half power beam width gives the first null beam width. with the same steps applied, the half power beam width of the antenna is 450. first null beam width is 900.

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Q. The solid area through which all the power radiated by the antenna is:

• (A) beam area
• (B) effective area
• (C) aperture area
• (D) beam efficiency

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Correct answer - Option (A)

Explanation:

the beam area is the solid angle through which all of the power radiated by the antenna would stream if p (θ, φ) maintained its maximum value over beam area and zero elsewhere. this value is approximately equal to the angles subtended by the half power points of the main lobe in the two principal planes.

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Q. A is a device that converts a guided electromagnetic wave on a transmission line into a plane wave propagating in free space.

• (A) transmitting antenna
• (B) receiving antenna
• (C) radar
• (D) mixer

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Correct answer - Option (A)

Explanation:

a transmitting antenna is a device that converts a guided electromagnetic wave on a transmission line into a plane wave propagating in free space. it appears as an electrical circuit on one side, provides an interface with a propagating plane wave.

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Q. Dipole antennas are an example for:

• (A) wire antennas
• (B) aperture antennas
• (C) array antennas
• (D) none of the mentioned

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Correct answer - Option (A)

Explanation:

dipoles, monopoles, oops, yagi-uda arrays are all examples for wire antennas. these antennas have low gains, and are mostly used at lower frequencies.

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Q. antennas consist of a regular arrangement of antenna elements with a feed network

• (A) aperture antennas
• (B) array antennas
• (C) printed antennas
• (D) wire antennas

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Correct answer - Option (B)

Explanation:

array antennas consist of a regular arrangement of antenna elements with a feed network. pattern characteristics such as beam pointing angle and side lobe levels can be controlled by adjusting the amplitude and phase excitation of array elements.

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Q. A parabolic reflector used for reception with the direct broadcast system is 18 inches in diameter and operates at 12.4 GHz. The far-field distance for this antenna is:

• (A) 18 m
• (B) 13 m
• (C) 16.4 m
• (D) 17.3 m

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Correct answer - Option (D)

Explanation:

far field distance for a reflector antenna is given by 2d2/λ. d is the diameter and λ is the operating signal wavelength.

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Q. of an antenna is a plot of the magnitude of the far field strength versus position around the antenna.

• (A) radiation pattern
• (B) directivity
• (C) beam width
• (D) none of the mentioned

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Correct answer - Option (A)

Explanation:

radiation pattern of an antenna is a plot of the magnitude of the far field strength versus position around the antenna. this plot gives the detail regarding the region where most of the energy of antenna is radiated, side lobes and beam width of an antenna.

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Q. Antennas having a constant pattern in the azimuthal plane are called

• (A) high gain antenna
• (B) omni directional antenna
• (C) unidirectional antenna
• (D) low gain antenna

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Correct answer - Option (B)

Explanation:

omni directional antennas radiate em waves in all direction. if the radiation pattern for this type of antenna is plotted, the pattern is a constant signifying that the radiated power is constant measured at any point around the antenna.

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