Friday, 14 October 2016

Getting Started With Antenna

Antenna - An antenna is a device for converting electromagnetic radiation in space into electrical currents in conductors or vice-versa, depending on whether it is being used for receiving or for transmitting, respectively.

Types Of Antenna:
Radio Antenna- A radio antenna is defined as the structure which is associated with the transition between the guided wave and free space wave. It means it convert electron into photon.

Isotopic Antenna - The antenna which radiates equal power in all direction. The power which is radiated is generally in the shape of sphere.

Isotropic Antenna - The antenna which radiates energy in a particular direction is known as isotropic antenna.
Example - FM transmission

Radiation Pattern- The shape in which the antenna radiates its energy is known as the radiation pattern.
                                                                OR
Radiation patten is a representation of variation of power or field as a function of theta of phi.
Note- 3 dB power is known as HPBW(Half power band width) and is given by
                                                        E = 0.7071067
Radiation Intensity - The power radiated from antenna per unit solid angle is called radiation intensity which is denoted by U.

Note- 1 steradian = 3282.8064 square degree

Beam efficiency- The beam efficiency is defined as the ratio of the main lobe beam area to the total lobe beam area.

Stray factor- The ratio of the minor lobe area to the to the main lobe area is known as the stray factor.

Directivity- Directivity of an antenna is equal to the ratio of the maximum power radiated to its average value over a sphere which is observed in far field antenna.


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