In radio engineering, an antenna or aerial is the interfacebetween radio waves propagating through space and electric currents moving inmetal conductors, used with a transmitter or receiver. In transmission, a radiotransmitter supplies an electric current to the antenna's terminals, and theantenna radiates the energy from the current as electromagnetic waves (radiowaves). In reception, an antenna intercepts some of the power of a radio wavein order to produce an electric current at its terminals that is applied to areceiver to be amplified. Antennas are essential components of all radioequipment.
An antenna is an array of conductors (elements),electrically connected to the receiver or transmitter. Antennas can be designedto transmit and receive radio waves in all horizontal directions equally(omnidirectional antennas), or preferentially in a particular direction(directional, or high-gain, or “beam” antennas). An antenna may include componentsnot connected to the transmitter, parabolic reflectors, horns, or parasiticelements, which serve to direct the radio waves into a beam or other desiredradiation pattern.