An antenna is a probing directional device for transmitting and receiving electromagnetic waves. Antennas are made of conductive materials. Microwave antennas are becoming ubiquitous in modern life. The wireless communications from mobile phones, Wi-Fi, and satellite systems are all examples of microwave antennas.
The wire antennas are the most common and cheapest type of antennas. They are used in many applications, such as radio and television broadcasting, radar, and satellite communications. They are usually made of a straight metal wire. There are also the dipole, loop, and helix. The loop antennas may be of any closed surface, such as a circle, square, or any other closed shape.
Array antennas is used when certain frequencies are required to be transmitted or received. A common array is the Yagi-Uda, which is made of reflector and director elements. A feed element is used to transmit and receive signals. The array gives more directionality and gain in one direction, while, minimizing the loss of signal. The Yagi-Uda array is commonly used in mobile phones, Wi-Fi, and satellite systems.
The aperture antennas are used for higher frequencies, such as those used in satellite communications and radar. The aperture of the antenna is the area where the signal is transmitted or received. They are useful for aircraft and satellite communications, and can be coated to avoid interference.