Antenna design
Antenna design- Foundations

An antenna is a device that couples a high-frequency current or voltage generator to an electromagnetic wave radiated into space. As this coupling is reciprocal, the antenna can both create radiation when supplied with power (transmitting antenna) and, conversely, collect energy when immersed in an electromagnetic field (receiving antenna).

We also speak of an aerial, a radiating element, a transducer between free space and a guided structure, or a "spatial filter"...

This transduction between the guided structure, where energy is controlled, and free space, where energy is radiated, is a first important characteristic of antennas. This medium can be characterized by its impedance, which represents its inertia...