A method of radio-identifying a plurality of passive transponders which transmitan individual code to a common reader that controls an anti-collision protocol

摘要

A method is disclosed of radio-identifying a plurality of objects, each provided with a passive transponder (3) transmitting an individual code to a common reader (4), the latter remote-powering the transponders and handling an anti-collision protocol for code blocks issuing simultaneously from the transponders. The simultaneous transmission of the blocks is produced in a transcoding step whereby the codes are associated in a biunique way with the position of a pulse within a frame. For each pulse read, the protocol creates a node associated with the original code. Thereafter, the reader broadcasts a serial information containing the position inside the extended code and the contents of one of the blocks read. The transponders compare these fields with a local pointer to the read address of a memory word that contains the code blocks, and with the pointed block. Only those transponders for which a match is ascertained will transmit a subsequent block. The aggregate of all these originate further nodes which are joined to a previous one by an equal number of branches of a search tree that discloses all of the existing codes once it has been gone through. IMAGE