Frequently Asked Questions On Antenna Theory With Answers -13.


This page contains basic questions and short notes on some of the keywords on antenna theory:


61) What is a loop antenna?

A loop antenna is a radiating coil of any convenient cross-section of one or more turns carrying radio frequency current. It may assume any shape (e.g. rectangular, square, triangular and hexagonal).


62) Give an expression of radiation resistance of a small loop?

Radiation resistance of a small loop is given by
Rr = 31,200 ( A / λ2 )2


63) How to increase the radiation resistance of a loop antenna?

The radiation resistance of a loop antenna can be increased by:

  • Increasing the number of turns.
  • Inserting a ferrite core of very high permeability with loop antenna’ s circumference which will rise the magnetic field intensity called ferrite loop.



64) What are the types of loop antennas?

Loop antennas are classified into:

  • Electrically Small (Circumference < λ / 10 )
  • Electrically Small (Dimension comparable to λ )


65) What are Electrically Small loop antennas?

Electrically Small loop antennas is one in which the overall length of the loop is less than one-tenth of the wavelength. Electrically Small loop antennas have small radiation resistances that are usually smaller than their loop resistances. They are very poor radiators and seldom employed for transmission in radio communication.



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