3m Innovative Properties Company

Seth A Lieffort

Edward D Goff

Ronald David Jesme

Thomas C Mercer

Leroy Stolberg

A radio frequency identification (RFID) system is described that utilizes a substantially-contiguous conductive shield to shape an electromagnetic field formed by an antenna for communication with RFID tags. The antenna and the conductive shield have substantially planar forms, and may be mounted to a surface of a check-in/check-out area. The conductive shield is positioned around the antenna and within a plane parallel to the antenna, e.g., within the same plane. The conductive shield shapes the electromagnetic field to extend substantially in a direction perpendicular to the antenna, and prevents the electromagnetic field from forming substantially over the conductive shield.

Field-shaping shielding for radio frequency identification (RFID) system

A multi-loop antenna is described having a plurality of conductive loops to produce an electromagnetic field for radio frequency identification (RFID) communication with RFID tags. The conductive loops are spaced apart at least a distance that is selected based on a dimension of the RFID tags with which the antenna communicates. In this manner, the loops are positioned and spaced in a manner that reduces the size of the holes within the resulting magnetic field. In addition, the configuration of the described dual-loop antenna increases the coverage of the antenna, and decreases inter-winding capacitance, thereby increasing overall read range achieved by the antenna.

Multi-loop antenna for radio frequency identification (RFID) communication

Techniques for detecting radio-frequency identification (RFID) tags are disclosed. For example, an exit control system is described that detects unauthorized removal of articles from a protected facility. A series of antennas are setup to produce interrogation corridors located near the exit of the protected area. RFID tags are attached to the articles to be protected. Each tag includes information that uniquely identifies the article to which it is affixed and status information as to whether the articles removal from the facility is authorized. The RF reader outputs RF signals through the antennas to create electromagnetic fields within the interrogation corridors. The reader outputs RF power from a single port to the multiple antennas via a splitter/combiner. In this way, a single RF reader with only one transmitter/receiver port simultaneously interrogates multiple antennas. A variety of techniques are described by which the reader can detect the removal of an unauthorized article.

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Eagan, MN, United States of America

Seth A Lieffort