A device comprising an arrangement of wires, metal rods, and so on for radiating and receiving radio signals.A transmitting antenna converts electrical current to electromagnetic radio waves projected into free space or a waveguide.A receiving antenna converts electromagnetic radio waves into electric current.An antenna commonly performs both transmit and receive functions.The transmitters and receivers used in free space optics (FSO) also can be characterized as antennas. See also free space, FSO, and waveguide.