Which of the following antenna is used as a standard reference for calculating directive gain?

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ESE Electronics 2011 Paper 2: Official Paper
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  1. Half wave dipole
  2. Infinitesimal dipole
  3. Elementary doublet
  4. Isotropic antenna

Answer (Detailed Solution Below)

Option 4 : Isotropic antenna
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Detailed Solution

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Concept:

  • The gain of an antenna is the ratio of the radiation intensity in a given direction to the radiation intensity that would be obtained if the power were radiated isotropically.
  • The gain of an antenna takes the directivity into account.
  • The term antenna gain describes how much power is transmitted in the direction of peak radiation to that of an isotropic source.

Isotropic source: It radiates equally in all directions.

F1 S.B Madhu 27.07.20 D5

Mathematically, the gain is defined as:

G = ηeD

ηe = Antennas efficiency

D = Directivity of the antenna

Since the value of ηe lies between 0 and 1, the directive gain of the antenna lies between 0 and the directivity of the antenna.

26 June 1

Directivity: The ratio of the radiation intensity in a given direction from an antenna to the radiation intensity averaged over all directions is termed as directivity.

Antenna's Efficiency: Antenna's Efficiency is the ratio of the radiated power of the antenna to the input power accepted by the antenna.

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