What is an antenna and what is its basic function?

An antenna is a transducer that converts electrical signals into electromagnetic waves for transmission, or vice versa for reception. It serves as the interface between the transmission line and free space. Key functions include: radiating RF energy efficiently, providing directional characteristics (gain), matching impedance between transmitter/receiver and free space (377 ohms), and operating at specific frequency bands. The antenna's size is typically related to the wavelength of the operating frequency.