Antenna is an electrical device which is used to convert current into radio waves.
It is used to transmit the information from one place to another via signal over a long distance. Generally it is used in transmitter and receiver or may one its depend upon the application. The transmitter sends the electrical signal to the antenna and antenna receive this signal and convert them into a signal or waves and passes through the receiver antenna then receiver antenna receives the signal and amplify it in order to get good strength of the signal.
In olden antennas are used in only in radio communication . But now a days it is used in everywhere like television,satellite,military etc. depends upon the application different types of antenna is used each as its own features advantages as well as disadvantages. Mainly there are three types that are used most for communication they are parabolic antenna,yogi antenna,dipole antenna.
Parabolic antenna are generally called as dish antenna. It is widely used in television and satellite for good reception and bandwidth. It consist of a dish , ground support and ground plate. The radiation from the antenna is focused on a focus point and transmit the waves there is also a back radiation occur in this antenna to reduce that the dish is used to reflect back the radiation so the receiver can receive the signal without any loss. Yardage antenna are used only in home televisions because it is a high gain antenna. That improves the signal strength . It consists of one active element and few passive element.
Dipole antenna are made with two identical or symmetry metal wire rod. The driving current from the transmitter is applied, or for receiving antennas the output signal to the receiver is taken between the two halves of the antenna.