Antenna Theory: Part I

An antenna is a structure that provides a means for an electromagnetic guided wave on a transmission line to become a free-space wave (i.e. transmiting) and vice versa (i.e. receiving). The antenna has become a commonplace/essential part of the technology we use today. Antennas can be found in cars, planes, portable computers, cellular phones, and even in food packaging for RFID purposes.

The basic principle behind an antenna is that radiation is produced by an accelerated charge. In most practical cases, the charge is sinusodially accelerated and the resulting radiated field will only occur at the oscillation frequency.