WO2007105128A1 - Systeme et procede de lecture d'etiquettes electroniques - Google Patents

Systeme et procede de lecture d'etiquettes electroniques Download PDF

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Publication number
WO2007105128A1
WO2007105128A1 PCT/IB2007/050662 IB2007050662W WO2007105128A1 WO 2007105128 A1 WO2007105128 A1 WO 2007105128A1 IB 2007050662 W IB2007050662 W IB 2007050662W WO 2007105128 A1 WO2007105128 A1 WO 2007105128A1
Authority
WO
WIPO (PCT)
Prior art keywords
readers
signals
frequency
frequencies
reader
Prior art date
Application number
PCT/IB2007/050662
Other languages
English (en)
Inventor
Hendrik Lodewyk Van Eeden
Hendrik Van Zyl Smit
Original Assignee
Ipico Innovation Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ipico Innovation Inc. filed Critical Ipico Innovation Inc.
Publication of WO2007105128A1 publication Critical patent/WO2007105128A1/fr

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Classifications

    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
    • G06K7/0008—General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
    • G06K7/10—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
    • G06K7/10009—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves
    • G06K7/10316—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves using at least one antenna particularly designed for interrogating the wireless record carriers
    • G06K7/10356—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves using at least one antenna particularly designed for interrogating the wireless record carriers using a plurality of antennas, e.g. configurations including means to resolve interference between the plurality of antennas

Definitions

  • THIS INVENTION relates generally to wireless communications, and particularly to a system for and method of reading electronic tags, specifically RFID tags.
  • Regional spectrum regulations limit power output from an RFID (Radio Frequency Identification) reader, also known as an interrogator; for example in FCC in the USA, UHF (Ultra High Frequency) RFID readers are limited to 4 W EIRP (Effective Isotropic Radiated Power) and in European countries UHF readers are limited to 500 mW ERP (Effective Radiated Power) or 2 W ERP. Similar limits apply at other carrier frequencies and in other regions.
  • the regulatory power limit limits the maximum reading range of a reader, or limits reliability of a reader at a specific range.
  • RFID tags also known as transponders
  • transponders it is often required to read RFID tags, also known as transponders, from multiple orientations.
  • the article might obstruct or absorb the RF beam, making it difficult to read and identify all the articles successfully from just one side.
  • the conventional method to read from multiple orientations or to cover a wider area is to split a signal from a single reader between multiple antennas. This results in a 3 dB reduction in power at each antenna, if two antennas are used. Due to the regulatory limits, it is not possible to increase the power output of the reader to compensate for the loss. The net result is that reading range is decreased or penetration is reduced in areas where beams from the antennas do not overlap.
  • the signal from a single reader can be multiplexed between multiple antennas. In this case, there is no reduction in power, but total reading time is increased.
  • the signal radiated from the antennas will have exactly the same frequency and a fixed phase relationship. This results in a fixed interference field with stationary nulls, caused by destructive interference, and peaks, caused by constructive interference, in the field. In the worst case, null paths result and if a tagged article moves along a null path, it is possible for the tagged article to move past the reader without being detected. In fact, due to the effect of destructive interference, the use of two or more readers in the same zone operating in the same or similar channels (i.e. at the same or similar frequencies) is generally discouraged.
  • a system for interrogating electronic tags including: at least two readers, a first reader being operable to transmit into a zone in which the electronic tags may be present a signal at a first frequency, and a second reader being operable to transmit into the zone a signal at a second frequency which is different from the first frequency, the first and second frequencies being close to each other.
  • the transmitted signals may interfere with each other, causing peaks from constructive interference and nulls or valleys from destructive interference, thereby creating an interference field.
  • the interaction between the signals transmitted by the respective readers, in use may create a dynamic interference field in the zone, peaks and nulls or valleys of the interference field at a fixed spatial point being time-varying.
  • the rate of change or the frequency of the interference field (e.g. at a fixed spatial point) may be the difference between the first and second frequencies.
  • the period of the difference between the first and second frequencies may be at least twice as long as a period of data packets transmitted back, in use, to the readers by the electronic tags.
  • the period of the interference field (which is the inverse of the frequency of the interference field) may be greater than twice the period of the data packets transmitted by the electronic tags. If, for example, a packet or message from the electronic tag is 300 ⁇ s long, the period of the difference in frequency between the signals transmitted by the first and second readers is preferably at least 600 ⁇ s, the difference between the first and second frequencies therefore being at most 1.67 kHz, for example being less than 1 kHz.
  • the difference between the first and second frequencies is therefore preferably low enough to allow for packets from the electronic tags to be successfully transmitted to the readers.
  • the system may include a plurality of electronic tags in the form of RFID tags, for example in the form of passive RFID tags.
  • the RFID tags may include an energy storage medium, for example being used to power the RFID tags through the nulls of the interference field.
  • the first and second readers may be operable to transmit their respective signals at different frequencies from a frequency at which the electronic tags backscatter their signals, thereby to minimise interference between the reader-transmitted signals and the backscattered signals.
  • the readers are operable to use a memory-less protocol and individual transmissions from the electronic tags are short enough to be successfully transmitted in a peak of the interference field.
  • the readers may transmit in a TTO (Tags Talk Only) or TTF (Tags Talk First) protocol.
  • TTO Tags Talk Only
  • TTF Tags Talk First
  • the readers may transmit in iP-X protocol mode (which is a commonly used RFID TTO protocol).
  • the first and second readers may be operable to transmit their respective signals at different strengths.
  • destructive interference may cause only valleys or dips on the interference field, rather than nulls.
  • the interference field may have dips instead of nulls.
  • the invention extends to a method of interrogating electronic tags, the method including: transmitting into a zone in which the electronic tags may be present by a first reader a signal at a first frequency; and transmitting into the zone by a second reader a signal at a second frequency which is different from the first frequency, the first and second frequencies being close to each other.
  • the method may include creating a dynamic interference field in the zone, peaks and nulls or valleys of the interference field at a fixed spatial point being time- varying.
  • a period of the difference between the first and second frequencies (i.e. the inverse of the difference between the first and second frequencies) transmitted respectively by the first and second readers may be at least twice as long as a period of data packets transmitted to the readers by the electronic tags. More particularly, the difference between the first and second frequencies transmitted respectively by the first and second readers may be at most 1.67 kHz, for example being less than 1 kHz.
  • Transmitting the respective signals may include transmitting the respective signals at different frequencies from a frequency at which the electronic tags backscatter their signals, thereby to minimise interference between the reader- transmitted signals and the backscattered signals.
  • the readers may use a memory-less protocol.
  • the readers may use a TTO or TTF protocol.
  • the method may include transmitting the respective signals from the first and second readers at different strengths.
  • Figure 1 shows a schematic view of a system for reading electronic tags, in accordance with the invention.
  • FIGS 2 to 4 show graphs of waveforms generated by a system in accordance with the invention.
  • reference numeral 10 generally indicates a system in accordance with the invention.
  • the system 10 includes a first electronic reader 12.1.
  • the first reader 12.1 includes an antenna 14.1 and is operable to transmit a signal, schematically indicated by reference numeral 16.1 , at a first frequency.
  • the system 10 further includes a second electronic reader 12.2 which includes an antenna 14.2 and which is operable to transmit a signal, schematically indicated by reference numeral 16.2, at a second frequency.
  • the first frequency and the second frequency are different from each other, but are relatively close together (further described below).
  • a plurality of articles 18 have electronic tags, in the form of RFID tags 20, operatively attached thereto or integrated therewith.
  • the articles 18 may be in a zone 17, at least temporarily, into which the signals 16.1 , 16.2 are transmitted.
  • Each reader 12.1 , 12.2 is preferably operated at the regulatory power limit.
  • the system 10 operates in a UHF bandwidth.
  • the first reader 12.1 transmits the signal 16.1 at a frequency of 915.3 MHz into the zone 17, and the second reader 12.2 transmits the signal 16.2 at a frequency of 915.3002 MHz into the zone 17.
  • the difference between the two frequencies is therefore 200 Hz.
  • the two signals 16.1 , 16.2 are transmitted at the same strength, i.e. having the same ERP, for example 1 W.
  • an interference field is created.
  • An interference field or pattern at a fixed spatial point is shown in Figure 2 (the frequencies of the signals 16.1 , 16.2 are not necessarily to scale and are shown for illustrative purposes only) and is generally indicated by reference numeral 30.
  • a series of peaks 32 and nulls 34 are created, respectively due to constructive interference and destructive inference from the two signals 16.1 , 16.2, the interference field 30 thus being time-varying.
  • the frequency of the interference field 30 is the difference between the first frequency and the second frequency, i.e. 200 Hz.
  • the peaks 32 have an amplitude of the sum of the amplitude of the signals 16.1 , 16.2, which in this case results in a peak amplitude of twice the regulatory limit, thereby extending the range and/or penetrative power of the system 10.
  • the system 10 may find particular application in TTO or TTF protocols, for example the iP-X protocol.
  • TTO or TTF protocols for example the iP-X protocol.
  • iP-X protocol no data is transmitted from reader 12.1 .
  • the readers 12.1 , 12.2 operate in iP-X protocol at a baud rate of 256 kbit/s. As the interference pattern is fluctuating at 200 Hz, peaks will last for about 2.5 ms (half the period of 5 ms), which is long enough to allow the transmission of
  • the interference field 30 gives a better spatial coverage.
  • the readers 12.1 , 12.2 of the system 10 are dual frequency readers, which transmit signals 16.1 , 16.2 in the band 119 kHz to 135 kHz, but receive backscatter from the tags 20 in the 6.8 MHz ISM band.
  • the readers 12.1 , 12.2 have a master/slave relationship.
  • the master reader 12.1 operates at 125 kHz, while the slave reader 12.2 operates at 126 kHz.
  • the resulting interference pattern has a frequency of 1 kHz, i.e. a period of 1 ms.
  • the signals 16.1 , 16.2 are of equal strength, and the interference pattern is similar to the interference pattern 30 of Figure 2. Both readers execute the iP- X protocol at a baud rate of 128 kbit/s, with ID and data packets of 600 ⁇ s in length.
  • the RFID tags 20 backscatter data at a 6.8 MHz frequency and are thus independent of the fluctuating 125/126 kHz energising signal 16.1 , 16.2.
  • Peak strengths in the interference field 30 are twice the strength that could be achieved with a single reader or with split or multiplexed antennas from a single reader, resulting in faster charge-up times and longer reading ranges of the RFID tags 20. Due to the phase relationship between the two signals 16.1 , 16.2 shifting all the time, there is no fixed cancellation of the signals 12.1 , 12.2 at any fixed spatial point. Therefore, no fixed null paths, which act as blind spots, are present.
  • Figure 3 shows an interference pattern 40 caused by the readers 12.1 , 12.2 transmitting signals 16.1 , 16.2 of unequal strengths (for example 1 W and 0.5 W, or at a point in space which is closer to one reader 12.1 than to the other 12.2). Due to one signal 16.2 being weaker than the other signal 16.1 , the two signals 16.1 , 16.2 never completely cancel each other out, with the result that there are no nulls in the interference pattern, simply valleys or dips 44. As can be seen, there are still peaks 42, although they are not as pronounced as the peaks 32 of Figure 2.
  • Figure 4 shows an interference pattern 50 caused by four readers (not shown) transmitting signals at different frequencies.
  • the interference pattern 50 is at a point in space equidistant from four equal strength readers, or otherwise at a point in space where all four signals are of the same strength.
  • the invention as exemplified provides an improved system for and method of reading RFID tags with multiple readers by creating a dynamic or time-varying interference signal. Further, because of constructive interference, the maximum signal power may be increased above the regulatory limits of a single reader.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Artificial Intelligence (AREA)
  • Computer Vision & Pattern Recognition (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Electromagnetism (AREA)
  • General Health & Medical Sciences (AREA)
  • Near-Field Transmission Systems (AREA)

Abstract

La présente invention concerne un système (10) et un procédé pour interroger des étiquettes électroniques (20). Le système (10) comprend au moins deux dispositifs de lecture (12.1 , 12.2) , un premier dispositif de lecture (12.1 ) pouvant être activé pour transmettre, dans une zone (17) dans laquelle les étiquettes électroniques (18) peuvent être présentes, un signal (16.1) à une première fréquence et un second dispositif de lecture (12.2) pouvant être activé pour transmettre dans la zone (17) un signal (16.2) à une seconde fréquence différente de la première fréquence, les première et seconde fréquences étant proches l'une de l'autre, de sorte que les valeurs nulles stationnaires dans le champ d'interrogation sont évitées du fait de ce battement de fréquences.
PCT/IB2007/050662 2006-03-10 2007-03-01 Systeme et procede de lecture d'etiquettes electroniques WO2007105128A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
ZA2006/02066 2006-03-10
ZA200602066 2006-03-10

Publications (1)

Publication Number Publication Date
WO2007105128A1 true WO2007105128A1 (fr) 2007-09-20

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106662632A (zh) * 2014-06-06 2017-05-10 Zih公司 改进利用多个位置技术的实时位置系统的方法、装置和计算机程序产品
EP2564467B1 (fr) 2010-04-26 2017-10-25 Cambridge Enterprise Limited Systèmes d'interrogation d'étiquettes rfid
JP2021528029A (ja) * 2019-04-19 2021-10-14 エヌイーシー ラボラトリーズ アメリカ インクＮＥＣ Ｌａｂｏｒａｔｏｒｉｅｓ Ａｍｅｒｉｃａ， Ｉｎｃ． クラウド化されたｒｆｉｄの読み取り

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6060815A (en) * 1997-08-18 2000-05-09 X-Cyte, Inc. Frequency mixing passive transponder
WO2005043447A1 (fr) * 2003-10-27 2005-05-12 Zih Corp Lecteur pour transpondeurs rfid, et procede correspondant

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6060815A (en) * 1997-08-18 2000-05-09 X-Cyte, Inc. Frequency mixing passive transponder
WO2005043447A1 (fr) * 2003-10-27 2005-05-12 Zih Corp Lecteur pour transpondeurs rfid, et procede correspondant

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
CHING LAW, LAYI LEE, KAI-YEUNG SIU: "Efficient memoryless protocol for tag identification", 2000, ACM PRESS, NEW YORK, ISBN: 1-58113-301-4, XP002434450 *
COLLINS, JONATHAN: "New System's Tags Talk First, and Fast", RFID JOURNAL, 15 December 2005 (2005-12-15), XP002434448, Retrieved from the Internet <URL:http://www.rfidjournal.com/article/articleprint/2045/-1/1> [retrieved on 20070522] *

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2564467B1 (fr) 2010-04-26 2017-10-25 Cambridge Enterprise Limited Systèmes d'interrogation d'étiquettes rfid
EP2564467B2 (fr) † 2010-04-26 2020-10-28 Cambridge Enterprise Limited Systèmes d'interrogation d'étiquettes rfid
CN106662632A (zh) * 2014-06-06 2017-05-10 Zih公司 改进利用多个位置技术的实时位置系统的方法、装置和计算机程序产品
JP2021528029A (ja) * 2019-04-19 2021-10-14 エヌイーシー ラボラトリーズ アメリカ インクＮＥＣ Ｌａｂｏｒａｔｏｒｉｅｓ Ａｍｅｒｉｃａ， Ｉｎｃ． クラウド化されたｒｆｉｄの読み取り
JP7220286B2 (ja) 2019-04-19 2023-02-09 エヌイーシー ラボラトリーズ アメリカ インク クラウド化されたｒｆｉｄの読み取り

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