US 6,127,928 · Granted 2000-10-03

Method and apparatus for locating and tracking documents and other objects

An apparatus and method are described for a radio frequency document control system that enables the location of documents, such as office files, to be automatically and rapidly identified. A host transceiver, controlled via a PC, transmits a coded RF signal, at a first frequency, to individually addressable, low cost, local exciters/transceivers located on shelves and/or in drawers. The local exciters, which may be sequentially addressed, retransmit the coded RF signal at a second frequency via an antenna. A passive radio frequency identification tag, containing the same code as that transmitted by the local exciter and attached to a document, such as a file folder, when in the vicinity of the antenna of the local exciter, is energized by the RF field and modulates the second frequency signal from the local exciter. The second frequency signal modulated by the energized tag is then directly received by the host transceiver. A PC, coupled to the host transceiver, enables the system to automatically and rapidly identify, down to a specific shelf or drawer, the location of tagged documents in an office environment.

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