An antenna is a device used for transmitting or receiving electromagnetic waves. It is a crucial component in engineering systems such as radio communication, broadcasting, television, radar, navigation, electronic warfare, remote sensing, and radio astronomy. All systems that use electromagnetic waves to transfer information rely on antennas to function. Additionally, for transmitting energy through electromagnetic waves, non-signal energy radiation also requires antennas.
Main Functions of an Antenna
1. Conversion Function: An antenna converts guided waves (current and voltage) propagating along transmission lines into electromagnetic waves propagating in unbounded media, and vice versa.
2. Energy Focusing: An antenna focuses its electromagnetic energy in the desired direction or pattern to improve the efficiency of signal transmission and reception.
Radio Waves and Microwaves
Radio waves and microwaves are electromagnetic waves with frequencies between approximately 20 MHz and 200 GHz. They can freely pass through space. On Earth, they mainly pass through the Earth's atmosphere, which is very similar to free space. Maxwell's equations describe how electromagnetic waves are generated by charges and currents and how they propagate through space.
IEEE Definition of Antenna
The IEEE defines an antenna as a part of a transmitting or receiving system designed to radiate or receive electromagnetic waves. To send radio waves from one location to another, you need something to accomplish this, and that is precisely the role of an antenna.
Important Parameters of Antennas
One of the most important parameters of an antenna is how it focuses electromagnetic energy. Almost all antennas emit and receive radio waves in the desired pattern or direction. For example, a broadcast tower can radiate signals in all directions but typically does not radiate upwards or downwards since there is usually no one trying to receive broadcasts directly above or below the tower.
Simple Definition
An antenna is a part of a transmitting or receiving system designed to transmit or receive electromagnetic waves.
With an antenna, we can effectively transmit and receive electromagnetic waves, thereby enabling the transfer of information and the radiation of energy.