unantenna

Unantenna is a term that appears in several contexts to denote devices or concepts that are not conventional transmitting or receiving antennas. There is no single, universally accepted definition. In some discussions, unantenna refers to a device whose primary function is not radiation of a signal but interaction with ambient electromagnetic fields in non-radiative ways, such as sensing, energy harvesting without emitting, or field manipulation through near-field effects. In other uses, the term is employed more metaphorically to describe structures that alter field distributions without acting as radiating elements.

Possible interpretations include passive field sensors that couple to external RF fields via capacitive or inductive coupling, metamaterial or metasurface devices that redirect or localize energy without a traditional radiation pattern, or quantum sensors that detect fields without conventional antenna operation. Some proponents emphasize a distinction between unantennas and conventional antennas by noting the absence of a defined far-field radiation pattern or a standard input–output transfer function.

In scientific and engineering discourse, the term is not standardized and has received skepticism, especially in claims of energy harvesting or communication without a radiating element. Critics point to the need for clear definitions, measurements, and adherence to established antenna theory.

See also: antenna, near-field communication, metamaterials, rectenna, energy harvesting, sensor.