Antenna Theory - FAQ's With Answers - 1.


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


1) Define an antenna?

Antenna is a transition device or a transducer between a guided wave and a free space wave or vice-versa. Antenna is also said to be an impedance transforming device.


2) What is meant by radiation pattern?

Radiation pattern is the relative distribution of radiated power as a function of distance in space .It is a graph which shows the variation in actual field strength of the EM wave at all points which are at equal distance from the antenna. The energy radiated in a particular direction by an antenna is measured in terms of FIELD STRENGTH. (E Volts/m)


3) Define Radiation intensity?

The power radiated from an antenna per unit solid angle is called the radiation intensity U (watts per steradian or per square degree). The radiation intensity is independent of distance.


4) Define Beam efficiency?

The total beam area (WA) consists of the main beam area (WM) plus the minor lobe area (Wm).
Thus WA = WM+ Wm.

The ratio of the main beam area to the total beam area is called beam efficiency.
Beam efficiency (SM) = WM / WA.


5) Define Directivity?

The directivity of an antenna is equal to the ratio of the maximum power density P (q,f)max to its average value over a sphere as observed in the far field of an antenna.

D = P (q,f)max / P(q,f)av. Directivity from Pattern.

D = 4p / WA. Directivity from beam area (WA).


ALSO READ:

- Effective Aperture & Directivity Of A Short Dipole Antenna.

- What is Polarization & What Are It's Different Types?

- What are the different types of aperture?

- Define different types of aperture?

- Define Aperture efficiency?

- What is meant by effective height?

- What are the field zones?

- ...Return To Antenna Theory FAQ's Main Page.


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