Antenna Class Test

Analyze the behavior of an antenna in the near-field region and identify which quantity dominates in this zone.

• Reactive fields

• radiated fields

• impedance

• Gain

Analyze the behavior of an antenna in the far-field region and identify which quantity dominates in this zone.

• reactive field

• radiated field

Identify the parameter that defines the ratio of maximum radiation intensity to average radiation intensity of an antenna

• Radiation pattern

• Directivity

• impedance

• Efficiency

Apply the relation between gain and directivity to determine the gain of an antenna with a directivity of 8 dBi and an efficiency of 0.75.

• 6.75dBi

• 9.25dBi

• 1.25dBi

• 3.25dBi

Analyze how beam area influences the directivity of an antenna system: An antenna has a beam solid angle of 1.5 steradians.
Compare this with another antenna having a beam solid angle of 0.8 steradians.
Which antenna has higher directivity, and why?

• Both antennas have the same directivity, since beam area doesn’t affect it.

• The antenna with 1.5 sr beam area, because directivity increases with beam area.

• The antenna with 0.8 steradians beam area, because directivity is inversely proportional to beam area.

• Directivity is independent of beam area and depends only on gain.

Identify the directivity value of an isotropic antenna?

• 0

• 1

• 2

• 3

Evaluate the maximum effective aperture of a microwave antenna with a directivity of 900.

• 71.6 m²

• 7 λ² m²

• 6 λ² m²

• 71.6 λ² m²

Analyze the primary function of the director element in a Yagi-Uda antenna.

• Reflects energy away from the source

• Increases forward gain by focusing radiation

• Matches the impedance of the feedline

Evaluate why a Yagi-Uda antenna is more effective than a dipole in point-to-point communication systems.

• Requires no alignment with the signal direction

• Has a simpler construction

• Provides higher gain and better directivity

• Covers a wider frequency range

Determine the spacing required between the reflector and the driven element in a Yagi-Uda antenna operating at 300 MHz.

• 15-25%

• 100%