Frequently Asked Questions On Antenna Theory With Answers -17.

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


81) What is meant by diversity reception?

To minimize the fading and to avoid the multi path interference the technique used are diversity
reception. It is obtained by three ways:

• Space diversity reception.
• Frequency diversity reception.
• Polarization diversity.

82) Define Space diversity Reception?

This method exploits the fact that signals received at different locations do not fade together. It requires antennas spaced at least 100λ apart are preferred and the antenna which high signal strength at the moment dominates.


83) Define frequency diversity Reception?

This method takes advantage of the fact that signals of slightly different frequencies do not fade synchronously. This fact is utilized to minimize fading in radio telegraph circuits.


84) Define polarization diversity reception?

It is used in normally in microwave links, and it is found that signal transmitted over the same path in two polarization have independent fading patterns. In broad band dish antenna system, Polarization diversity combined with frequency diversity reception achieve excellent results.


85) What is meant by Faraday's rotation?

Due to the earth’ s magnetic fields, the ionosheric medium becomes anisotropic and the incident plane wave entering the ionosphere will split into ordinary and extra ordinary waves/modes.

When these modes re-emerge from the ionosphere they recombine into a single plane wave again. Finally the plane of polarization will usually have changed, this phenomenon is known as Faraday's rotation.