A Van Atta array is a type of passive retrodirective

phased array antenna In antenna theory, a phased array usually means an electronically scanned array, a computer-controlled array of antennas which creates a beam of radio waves that can be electronically steered to point in different directions without moving th ...

which redirects (rather than reflects) a signal back in the direction from which it came. It was first described by L. C. van Atta in his 1959 patent. The signal can be modulated by the redirecting host for purposes such as

radio-frequency identification Radio-frequency identification (RFID) uses electromagnetic fields to automatically identify and track tags attached to objects. An RFID system consists of a tiny radio transponder, a radio receiver and transmitter. When triggered by an electromag ...

and traffic control (radar target echo enhancement). A 2023 paper describes the extension of the van Atta antenna principle to underwater acoustic communication.

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See also