Antenna

In this world there are many type of antenna ,because it has wide range of application in broadcasting and communication field i.e radio broadcasting ,television broadcasting, mobile communication,microwave communication,satellite communication ,military communication etc.

We must have the knowledge about antenna type, characteristics, wave radiations pattern,installations of antenna.If you are going to installation of antenna then you must take attention about those and following parameters:

1. antenna gain
2. efficiency of antenna
3. impedance matching
4. input power
5. output power
6. bandwidth
7. polarizations

Fundamental theory of antenna is that it is a kind of transducer.Transducer is a electronics devices which convert one form of energy into other form of energy ,i.e non-electrical into electrical and vice-verse.

Antenna convert electrical signal into electromagnetic wave and vice-verse at output and input respectively.
Generally 73ohm impedance antenna is used in radio receiver. For commercial purpose 50ohm
antenna is used in receiver and for consumer purpose 75ohm antenna is used in receiver.
According to the construction of antenna they are following type:

• dipole antenna

• folded dipole antenna

• yagi antenna

• parabolic dish antenna

• helical antenna

• microwave antenna

According to wave radiations pattern they are following type:

1. uni-directional antenna
2. bi-directional antenna
3. Omani-directional antenna

In uni-directional antenna ,wave propagation is only one particular direction.

In bi-directional antenna,wave propagates in two opposite direction.

In Omani-directional antenna,wave propagates in all rounds or all direction.

Although those all are known ,you must know about wave propagation in the space.There are following type of wave propagation:

• ground wave propagation

• space wave propagation

1. straight wave propagation(line of sight i.e LOS )

• sky wave propagation

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