Localization Using Virtual Antenna Arrays in Modulated Backscatter Rfid Systems

Abstract

A localization method for use in a tag communication system includes associating a supertag having a plurality of tags with an item, reading backscatter signals from the tags of the plurality of tags to provide a plurality of backscatter signals, estimating a signal parameter of the backscatter signals of the plurality of backscatter signals to provide a plurality of derived signal parameters, and localizing the item in accordance with the plurality of derived signal parameters. The backscatter signals are read by a tag reader having a single antenna and the item is localized in accordance with an antenna array technique performed upon the plurality of derived signal parameters. The backscatter signals are read with an antenna array to provide a further plurality of derived signal parameters for each tag of the plurality of tags, and the item is localized in accordance with the further pluralities of derived signal parameters.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of Invention[0002]This invention relates to security tags and, more particularly, to localizing security tags and security tag readers.[0003]2. Description of Related Art[0004]U.S. Patent Publication No. 2002 / 0145563 A1, filed on Jan. 26, 2001 by Kane, discloses the use of time of arrival information and phase difference information in backscatter signals for precisely localizing a subject, and precisely monitoring the gait of the subject. In the Kane system the backscatter signals are produced by a plurality of RFID tags positioned at different locations on the body of the subject to be monitored. Additionally, Kane teaches a plurality of receiving antennas for receiving the signals from the tags on the body of the subject, and performing separate phase difference calculations.[0005]U.S. Pat. No. 7,009,561, issued on Mar. 7, 2006 to Menache, discloses an RF motion tracking system including a stationary RF transmitter and a plurality of stat...

AI Technical Summary

Benefits of technology

This patent describes a way to use virtual antenna arrays to improve asset tracking and localization. By arranging tags in an array and measuring the signals they reflect, a reader can achieve high accuracy in localization. The added benefit of additional information from different signals and travel times allows for better identification of tags and positioning of a reader. This method can be combined with others to further enhance localization capabilities. Overall, this technology can provide low-cost infrastructure for accurate navigation or localization in areas like stores or warehouses.

Problems solved by technology

However, in Menache the marker tags are distributed over a number of items, and are thus not disposed on a single tag device.

Furthermore, the marker tags in the Menache system do not maintain a known geometric relationship with respect to each other.

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