Impinj, Inc.

Intel Corporation

Kurt Eugene Sundstrom

Christopher J Diorio

Scott A Cooper

Todd E Humes

John D Hyde

Paul F Dietrich

Jayasuryan Iyer

Alberto Pesavento

Sandesh Doddameti

Balaji Shyamkumar

Daniel Bowman

Ernest T Tsui

Aanand Esterberg

Richard B Nicholls

Andrew Friefeld

Amir Sarajedini

Gregory T Kavounas

Ronald A Oliver

Vadim Gutnik

Michael H Thomas

David Ord

David D Dressler

Dan Bowman

An RFID-based item tracking system may use statistical methods to determine whether a tag or tagged item that does not respond when inventoried is present in a particular zone or reader antenna field-of-view. In one embodiment, the item tracking system may determine an observability of an item based on one or more initial trials. Upon not detecting the item in one or more subsequent trials, the item tracking system may estimate whether the item is still present based on the observability.

RFID-based item presence detection

Embodiments are directed to restricting access to Radio Frequency Identification (RFID) tag information based on location. Access to RFID tag information may be restricted at the reader level, at the requester level, and at the network level. When reader-level restrictions exist, devices may be prevented from inventorying tags and retrieving information from tags. When requester-level restrictions exist, a requester or device may be prevented from receiving tag information from inventoried tags or a network. When network-level restrictions exist, a network may discard or otherwise restrict tag information received from devices.

Location-based access to RFID tag information

RFID readers may be configured to recover multiple, collided RFID tag signals. An RFID reader may receive a collided reply waveform including at least first and second tag responses. The reader may determine that the collided reply waveform contains multiple tag responses and recover the first and second tag responses from the collided reply waveform. The reader may first recover the first tag response, reconstruct the first tag response, and subtract the reconstructed first tag response from the collided reply waveform to form a modified tag response. The reader may then recover the second tag response from the modified tag response.

Weak RFID tag signal recovery from collisions

Embodiments are directed to sequential encoding for RFID tags. An encoding line transports an RFID tag from the reading zone of a first reader to the reading zone of a second reader. The first reader communicates with the tag, writes a portion of an identifier to the tag, and sends a tag write status to the second reader. The second reader, situated after the first reader, communicates with the tag, receives the tag write status from the first reader, then determines a remaining portion of the identifier to be written to the tag based on the tag write status. The second reader then attempts to write the remaining portion to the tag. If the attempt fails, the second reader initiates an error-handling procedure.

Sequential encoding for RFID tags

RFID readers may be configured to recover weak RFID tag signals from collisions with stronger RFID tag signals. An RFID reader may receive a combined tag response including a strong tag response and a weak tag response. The reader recovers the strong and weak tag responses using source separation. In one example, the reader may recover the strong tag response from the combined tag response and remove the recovered tag response from the combined tag response to form a modified tag response. The reader may then recover the weak tag response from the modified tag response.

RFID tags, tag circuits, and methods are provided that reject at least in part the distortion caused to wireless signals by interference in the environment. When the received RF wave is converted into an unfiltered input (), a filtered output () is generated that does not include an artifact feature deriving from the distortion. The filtered output is used instead of the unfiltered input, which results in tag operation as if there were less interference in the environment, or none at all.

Interference rejection in RFID tags

Growing community of inventors

Seattle, WA, United States of America

Kurt Eugene Sundstrom