What is Antenna? Explain in relation with electromagnetism.

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INTRODUCTION:

Antenna is basically a device which gets conversion of energy that we have in wired medium that we have in terms of current and voltage to the wireless medium in terms of Electric and Magnetic field, where it is acting as transmitting antenna and on another hand it is working as receiving antenna when the conversion goes back Electric and Magnetic field back to the voltage and current form.

An antenna can be called as a transducer that converts the radio frequencies that recurrent electromagnetic waves which are then radiated into space. In the process of the transmission, oscillating radio frequency is applied to the antenna terminals and the antenna radiates the energy from the current as electromagnetic waves (radio waves).

BASIC STRUCTURE:

In an antenna, an oscillating current of the electrons is driven outside by the transmitter that will create a Magnetic field (oscillating) wave in the surroundings of the antenna elements while electrons’ charge creates either and electric field (oscillating) with the element.

This field radiates outside the antenna into the space as a moving EM field wave.

Antenna reciprocity could be used for both transmission and receiving. In two way communication send antenna can be used as transmitter and receiver.

WORKING:

Say we have an electric signal, so how do we convert it into electromagnetic wave? By using the principles of electromagnetic induction and by using a closed conductor, we can generate a fluctuating magnetic and electric field in its surroundings. In transmitting signals, the fluctuating field around the source is not usable. The electromagnetic field here doesn’t propagate, instead, it just fluctuates in the surroundings of the source.

For an antenna to work, the electromagnetic waves should get separated from their source and they must be propagated. And that is made possible when we make a proper arrangement for the oscillating charges (positive and negative) in a dipole. This is how we make antenna as a transmitter. Here we know that frequency of the signal that is transmitted will be same as frequency of the applied voltage signal for making wave propagation possible.

(This image shows the process of separation of propagated waves through dipole)

If the above process is done reversely, means that if a propagated electromagnetic field hits the antenna back, it is called an antenna receiver.

For both the processes we must consider that the size of the antenna should be half of the wavelength of the propagated waves.

NEED OF ANTENNAS:

Antennas gives us so many reasons to use them but the most common benefit is that we can transfer data wirelessly through signals, where it is nearly impossible with another method.

Taking a simple example of an aeroplane: A pilot needs to get in touch with the Air Traffic Control Officer frequently. Now imagine a cable/ wire tied from aeroplane to the ATC towers for making their communication possible. Surely, it is not an effective way. SO this is how, antennas make our communication wireless.

DIFFERENT TYPES OF ANTENNA AND THEIR APPLICATIONS:

TYPE OF ANTENNA	APPLICATIONS
Wire antennas	Ships, Air Crafts, Automobiles
Array antennas	Used to control radiation patterns
Micro strip antennas	Satellites, missiles, cars, mobiles
Lens antennas	High frequency application
Reflector antennas	Microwave communication
Aperture antennas	Air-craft, space-craft