Antenna

A conductor designed to translate an alternating current into or from an electromagnetic field. An antenna transmits when it radiates an electromagnetic field in response to an applied alternating current. An antenna receives when it induces an alternating current in response to an ambient electromagnetic field. Antennas generally exhibit a high degree of reciprocity -- that is, their behavior as transmitters and receivers is the same in most situations. For example, an antenna that transmits most effectively in a certain direction will also receive signals most effectively from the same direction.

In RFID, antennas come in two general types. Inductive antennas are coils that use magnetic coupling; they are most commonly encountered in low-frequency and high-frequency tags and readers, but are also used in ultra-high-frequency near-field tags. Most UHF and microwave tags use variants of the dipole antenna, and are radiatively coupled to the reader antenna, which is often a patch antenna or (less frequently) a Yagi-Uda antenna.

See Also

Important antenna concepts in RFID system design include Mono-Static vs. Bi-Static, Resonant Frequency, Bandwidth and Gain.

Tag antenna manufacturing techniques include Etching, Foil Stamping, and Screen Printing.