WIRELESS ANTENNA

WHAT IS ANTENNA :

                                             "It's a electromechanical structure which is used to transmit and receive  electromagnetic signals into space" .

HOW THE NAME ANTENNA COINED:

                              We know that in communication we require a electrical signal to be transmitted in the wire. But we cannot link long distances due to requirement of high infrastructure . And maintaing of these electrical cables is very difficult or we can say almost impossible .

                     So avoid this problem the scientists decided to use free space as the medium . But we all know that free space cannot be used to transmit electrical signals .

         NOW Scientists thought of something which will convert the electrical signal to electromagnetic signals and radiate it in free space 

And this is how "Antenna" was come into picture.

HOW ANTENNA WORKS:

                                             According to source theorem we know that "Maximum power will be transfered between source and destination if there is equal load on both sides or there should be matching in impedance ".

                        So what if there is mismatch in impedances , Suppose we have sent 1 watt power and the power reached to destination is 0.9 watt . 

          The question arises that where that 0.1 watt of power has gone. The Answer to this question is that " LEAKAGE CURRENT" .

The 0.1 watt will be converted to leakage power and it will be in terms of "RADIATION". Which is basically a electromagnetic waves.

The below figure shows "reflection signal and radiation"

"Production of Radiation by using waveguide "

                                                                                 

But the problem is that it is only small amount of radiation which can cover very small distance of about 100 meters .

CHALLENGES:

1) The radiation cover very small distance .

2) To increase radiation we may think of increasing power but it should be kept in mind that the human and other living cells will be affected due to more powerful radiation so we can no more increase power level.

USE OF ANTENNA TO SOLVE THIS:

Now the concept of antenna came that , If we increase the width of waveguide at destination side we can get more radiation's  with the same input power of 1 watt ( just for example purpose) .

HOW RADIATION INCREASE WITH INCREASE IN WIDTH OF WAVEGUIDES END:

                                   Basically radiation is nothing but leakage current . so as conducting medium increase the amount of leakage current will increase and automatically the amount of radiation will increase.

The below figures shows amount of radiation for various antenna widths .

Note: It is to be pointed that the width is increased in small amounts for comparison purpose.

"small amount of radiation for small antenna width"

"Amount of radiation increase with increase in antenna width"

"Radiation further increase with antenna width"

  BUT up to what extent we can increase the width of antenna .

The limit for that is " not more than 90 degree".

                    Because anything beyond this will lead to same results as original width of waveguide . it is shown in below figure .

                                          

"It is maximum amount of tapering limit for antenna beyond which the results will be similar to original waveguide".

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