A directional radio-frequency identification (RFID) tag reader has been designed to facilitate finding a specific object among many objects in a crowded room. The device could be an adjunct to an electronic inventory system that tracks RFID-tagged objects as they move through reader-equipped doorways. Whereas commercial RFID-tag readers do not measure directions to tagged objects, the device is equipped with a phased-array antenna and a received-signal-strength indicator (RSSI) circuit for measuring direction. At the beginning of operation, it is set to address only the RFID tag of interest. It then continuously transmits a signal to interrogate that tag while varying the radiation pattern of the antenna. It identifies the direction to the tag as the radiation-pattern direction of peak strength of the signal returned by the tag. An approximate distance to the tag is calculated from the peak signal strength. The direction and distance can be displayed on a screen. A prototype containing a Yagi antenna was found to be capable of detecting a 915.5-MHz tag at a distance of Å15 ft (Å4.6 m).

This work was done by Pedro J. Medelius, John D. Taylor, and John J. Henderson of Dynacs, Inc., for Kennedy Space Center.

In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to:

Lynne R. Henkiel, KSC Industry Liaison

KSC Technology Programs &

Commercialization Office

Mail Code YA-C1

Kennedy Space Center, FL 32899

Phone: (321) 867-8130

Fax: (321) 867-2050

E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Refer to KSC-12348, volume and number of this NASA Tech Briefs issue, and the page number.