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Researchers Submit Patent Application, "Phase-Based Ranging for Backscatter Rfid Tags", for Approval

July 23, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- From Washington, D.C., VerticalNews journalists report that a patent application by the inventors Zhou, Chenming (Pittsburgh, PA); Griffin, Joshua D. (Pittsburgh, PA), filed on January 1, 2013, was made available online on July 10, 2014.

The patent's assignee is Disney Enterprises, Inc.

News editors obtained the following quote from the background information supplied by the inventors: "Embodiments presented in this disclosure generally relate to identifying a location of an RF tag and, more specifically, to determining a range of the tag using continuous wave radar.

"Typical radio frequency identification (RFID) tags or RF tags include a microprocessor functionally connected to an antenna. The microprocessor stores and processes relevant data that may include unique data for identifying a specific item associated with the RF tag. The microprocessor also modulates a radio frequency (RF) signal that is transmitted or backscattered via the antenna. An external tag reader captures the data signal transmitted by the RF tag.

"RF tags can be classified as 'active' or backscatter devices. Active tags use an internal power source to actively transmit a modulated signal to the tag reader. Backscatter tags, in contrast, do not actively transmit modulated signals to the tag reader but modulate the electromagnetic waves scattered from the tag's antenna. The signal that is scattered originates from the tag reader. Backscatter tags can be classified as 'passive' (without any onboard power source) or 'semi-passive' (includes an internal power source but still communicates with the tag reader via modulated backscatter and does not actively transmit a signal to the tag reader). Passive RF tags are powered by the incident signal transmitted by the tag reader. Passive and semi-passive tags are typically less expensive than active tags but have shorter functional ranges than active RF tags. Backscatter tags typically operate in the ultra-high frequency (UHF) or microwave frequency bands.

"In some cases, the external tag reader may be configured to determine the distance between the reader and the RF tag. Conventional ranging techniques, such as received signal strength (RSS) for either active or passive RF tags, work over relatively large areas but suffer from poor accuracy. Time of flight or frequency modulated continuous wave radar may also be used to determine the separation distance but these techniques work poorly for short distance applications because of the difficulties of measuring the small round trip time or frequency delay. Instead RF phase-based ranging techniques are preferred when high accuracy is required."

As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventors' summary information for this patent application: "One embodiment of the present disclosure is a method of performing phase-based ranging techniques. The method includes estimating a plurality of first distances between a RF tag and an RF tag reader using a continuous-wave (CW) ranging technique and estimating a plurality of second distances between the RF tag and the RF tag reader using a multi-frequency continuous-wave (MFCW) ranging technique. The method includes performing spatial averaging based on the pluralities of first and second distances to mitigate the effects of an error associated with the plurality of second distances.

"Another embodiment of the present disclosure is a RF tag reader. The tag reader includes an antenna and CW logic configured to estimate a plurality of first distances between a RF tag and the antenna using a CW ranging technique and MFCW logic configured to estimate a plurality of second distances between the RF tag and the antenna using a MFCW ranging technique. The tag reader includes spatial averaging logic configured to perform spatial averaging based on the pluralities of first and second distances to mitigate the effects of an error associated with the plurality of second distances.

"Another embodiment of the present disclosure is a RF receiver. The receiver includes an antenna and CW logic configured to estimate a plurality of first distances between a RF transmitter and the antenna using a CW ranging technique and MFCW logic configured to estimate a plurality of second distances between the RF transmitter and the antenna using a MFCW ranging technique. The RF receiver also includes spatial averaging logic configured to perform spatial averaging based on the pluralities of first and second distances to mitigate the effects of an error associated with the plurality of second distances.

BRIEF DESCRIPTION OF THE DRAWINGS

"So that the manner in which the above recited aspects are attained and can be understood in detail, a more particular description of embodiments of the invention, briefly summarized above, may be had by reference to the appended drawings.

"It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

"FIG. 1 is an RFID system, according to one embodiment disclosed herein.

"FIG. 2 illustrates a backscatter link of a backscatter channel, according to one embodiment disclosed herein.

"FIG. 3 is a RFID system configured to perform continuous wave ranging, according to one embodiment disclosed herein.

"FIG. 4 is a chart illustrating locating a RFID tag based on various continuous wave techniques, according to one embodiment disclosed herein.

"FIG. 5 is a chart illustrating the frequency spreading and accuracy tradeoff in dual-frequency continuous wave radar, according to one embodiment disclosed herein.

"FIG. 6 is a method of performing spatial averaging to identify a distance a signal propagates, according to one embodiment described herein.

"FIG. 7 is a chart illustrating spatial averaging a combined continuous-wave ranging system, according to one embodiment disclosed herein."

For additional information on this patent application, see: Zhou, Chenming; Griffin, Joshua D. Phase-Based Ranging for Backscatter Rfid Tags. Filed January 1, 2013 and posted July 10, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=5475&p=110&f=G&l=50&d=PG01&S1=20140703.PD.&OS=PD/20140703&RS=PD/20140703

Keywords for this news article include: Electronics, Microprocessors, Disney Enterprises Inc..

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Source: Electronics Newsweekly


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