Antenna is a metal device (in the form of a bar or wire) that functions to send and receive radio waves. Antenna is the tool to emit radiation or receive radio waves [IEEE Standard Definition]. Based on two standard definition above, an antenna is a conductor or a conductor group, which is responsible for radiating energy electromagnetic radiation into the air and free to collect (receive) electromagnetic energy from another free air.
Antenna change electrical energy from a transmitter into the system of energy and emit electromagnetic radiation into the air. Conversely, an antenna gathered energy electricity will be distributed to the recipient's system. Free air known as the air interface.
How does the antenna?
Radiation is a disturbance that occurred in the electromagnetic field which propagates out from the source of interference. Interference itself derived from sources that flow changed in that time has accelerated the flow of distribution. An electric current or static electric current that moves with constant speed in the straight channel transmission can not emit radiation.
However, a flow that moves with constant speed can be experienced on the radiation conditions below:
• meet the end of the channel transmission.
• find a channel transmission, which trap.
• transmission lines have shaped curve.
• transmission lines to meet the discontinue.
Meanwhile, a flow that can emit radiation accelerated despite creeping through the transmission lines straight.