Adjusting RFID waveform shape in view of signal from another reader Number:7,436,308 from the United States Patent and Trademark Office (PTO) owispatent

Title: Adjusting RFID waveform shape in view of signal from another reader

Abstract: Systems, software, devices, and methods are described for an RFID reader system to communicate with RFID tags. RF energy encountered in conjunction with using a selected channel is detected. The RF energy can be a signal from another RFID reader. The detected signal is used to adjust a waveform shaping parameter. RF waves can be transmitted from the reader to the RFID tags and RF waves can be backscattered from the RFID tags. At least some of the RF waves transmitted to or backscattered from the RFID tags have a waveform with a shape according to the adjusted waveform shaping parameter.

Patent Number: 7,436,308 Issued on 10/14/2008 to Sundstrom,   et al.

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Inventors:	Sundstrom; Kurt E. (Woodinville, WA), Diorio; Christopher J. (Shoreline, WA), Humes; Todd E. (Shoreline, WA), Dietrich; Paul (Seattle, WA)
Assignee:	Impinj, Inc. (Seattle, WA)
Appl. No.:	11/412,192
Filed:	April 25, 2006

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Related U.S. Patent Documents

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	Application Number	Filing Date	Patent Number	Issue Date
	60678903	May., 2005
	60709253	Aug., 2005
	60715917	Sep., 2005
	60751328	Dec., 2005

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Current U.S. Class:	340/572.4 ; 340/10.1; 340/10.3; 340/572.1; 455/106; 455/108; 455/189.1
Current International Class:	G08B 13/14 (20060101)
Field of Search:	340/572.4,572.1,10.1,825.69,568.1,10.3 331/175 455/106,108,189.1 702/107

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References Cited [Referenced By]

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U.S. Patent Documents

3938316	February 1976	Morokawa et al.
4454483	June 1984	Baylor
5117756	June 1992	Goffin, II
5438694	August 1995	Muri et al.
5565858	October 1996	Guthrie
5583819	December 1996	Roesner et al.
5649295	July 1997	Shober et al.
5649296	July 1997	MacLellan et al.
5686902	November 1997	Reis et al.
5701127	December 1997	Sharpe
5751220	May 1998	Ghaffari
5867535	February 1999	Phillips et al.
5912632	June 1999	Dieska et al.
5940006	August 1999	MacLellan et al.
5952922	September 1999	Shober
6023198	February 2000	McKinney et al.
6043748	March 2000	Touchton et al.
6046683	April 2000	Pidwerbetsky et al.
6064320	May 2000	d'Hont et al.
6127928	October 2000	Issacman et al.
6130623	October 2000	MacLellan et al.
6243013	June 2001	Duan et al.
6259991	July 2001	Nysen
6356161	March 2002	Nolan et al.
6388532	May 2002	Babcock
6404325	June 2002	Heinrich et al.
6472943	October 2002	Soong et al.
6600905	July 2003	Greeff et al.
6603391	August 2003	Greeff et al.
6639509	October 2003	Martinez
6664860	December 2003	Fallisgaard et al.
6784789	August 2004	Eroglu et al.
6917291	July 2005	Allen
7026935	April 2006	Diorio et al.
7091828	August 2006	Greeff et al.
7120550	October 2006	Diorio et al.
7253719	August 2007	Diorio et al.
7283037	October 2007	Diorio et al.
7304579	December 2007	Diorio et al.
2002/0167405	November 2002	Shanks et al.
2003/0174049	September 2003	Beigel et al.
2005/0099269	May 2005	Diorio et al.
2005/0099270	May 2005	Diorio et al.
2006/0261952	November 2006	Kavounas et al.
2006/0261953	November 2006	Diorio et al.
2006/0261954	November 2006	Dietrich et al.
2006/0261955	November 2006	Humes et al.

Foreign Patent Documents

	WO02/065380		Aug., 2002		WO
	WO-2005048312		May., 2005		WO
	WO-2005048612		May., 2005		WO

Other References

"U.S. Appl. No. 10/824,049 Notice of allowance mailed Nov. 9, 2005", 5 pgs. cited by other . "U.S. Appl. No. 10/824,049, Preliminary Amendment filed Jun. 23, 2005", 6 pgs. cited by other . "U.S. Appl. No. 10/824,049, Preliminary Amendment filed Jul. 13, 2004", 2 pgs. cited by other . "U.S. Appl. No. 10/824,049, Preliminary Amendment filed Oct. 11, 2005", 11 pgs. cited by other . "U.S. Appl. No. 10/824,049, Supplemental Notice of Allowability mailed Feb. 3, 2006", 3 pgs. cited by other . "U.S. Appl. No. 10/985,518, Final Office Action mailed Mar. 2, 2007", 6 pgs. cited by other . "U.S. Appl. No. 10/985,518, Non-Final Office Action mailed Jun. 28, 2006", 13 pgs. cited by other . "U.S. Appl. No. 10/985,518, Notice of Allowance mailed Jun. 5, 2007", 4 pgs. cited by other . "U.S. Appl. No. 10/985,518, Preliminary Amendment filed Jun. 23, 2005", 6 pgs. cited by other . "U.S. Appl. No. 10/985,518, Response filed May 2, 2007 to Final Office Action Mar. 2, 2007", 5 pgs. cited by other . "U.S. Appl. No. 10/985,518, Reponse filed Sep. 28, 2006 to Non-Final Office Action mailed Jun. 28, 2006", 9 pgs. cited by other . "U.S. Appl. No. 11/411,657, Preliminary Amendment filed Aug. 28, 2006", 3 pgs. cited by other . "U.S. Appl. No. 11/411,657, Preliminary Amendment filed Oct. 29, 2007", 5 pgs. cited by other . "U.S. Appl. No. 11/412,170, Preliminary Amendment filed Aug. 28, 2006", 3 pgs. cited by other . "U.S. Appl. No. 11/412,170, Preliminary Amendment filed Oct. 29, 2007", 5 pgs. cited by other . "U.S. Appl. No. 11/412,171, Preliminary Amendment filed Aug. 28, 2006", 3 pgs. cited by other . "U.S. Appl. No. 11/412,171, Preliminary Amendment filed Oct. 29, 2007", 5 pgs. cited by other . "U.S. Appl. No. 11/412,172, Preliminary Amendment filed Aug. 28, 2006", 3 pgs. cited by other . "U.S. Appl. No. 11/412,172, Preliminary Amendment filed Oct. 29, 2007", 5 pgs. cited by other . "International Search Report, for Application No. PCT/US04/37387, date mailed Mar. 24, 2005", 18 Pages. cited by other . "Part 1 Technical requirements and methods of measurements [Electromagnetic compatibility and radio spectrum Matters (ERM); Radio Frequency Identification Equipment operating in the band 865 MHz to 868 MHz with power levels up to 2 W]", ETSI EN 302 208-1 V1.1.1 (Sep. 2004), 1-52. cited by other . "Part 2 Harmonized EN under article 3.2 [Electromagnetic compatibility and radio spectrum Matters (ERM); Radio Frequency Identification Equipment operating in the band 865 MHz to 868 MHz with power levels up to 2 W]", ETSI EN 302 208-2 V1-1.1, (Sep. 2004), 1-17. cited by other . Finkenzeller, Klaus , "Fundamental Operating Principles", RFID Handbook; Fundamentals and Applications in Contactless Smart Cards and Identification, John Wiley & Sons, Ltd ; ISBN 0-470-84402-7,(2003),29-59. cited by other . EPCglobal, Inc. "Specification for RFID Air Interface-EPC Radio-Frequency Identity Protocols Class-1 Generation-2 UHF RFID Protocol for Communications at 860 MHz-960 MHz, Version 1.1.0." (a.k.a "The Gen 2 Spec".) EPCglobal Inc., Dec. 17, 2005. <http://www.epcglobalinc.org>. cited by other . EPCglobal Inc. "Specification for RFID Air Interface-EPC Radio-Frequency Identity Protocols Class-1 Generation-2 UHF RFID Protocol for Communications at 860 MHz-960 MHz, Version 1.0.8." EPCglobal Inc., Dec. 14, 2004. <http://www.epcglobalinc.org>. cited by other . Declaration of Stacy L. Jones authenticating attached Website Materials as accessed and posted at http://www.autoid.org/SC31/sc.sub.--31.sub.--wg4.sub.--sg3.htm on Sep. 1, 2006. cited by other . "U.S. Appl. No. 11/411,657 Notice of Allowance mailed Mar. 25, 2008", NOAR, 17 pgs. cited by other . "U.S. Appl. No. 11/412,172, Notice of Allowance mailed Feb. 28, 2008", NOAR, 14 pgs. cited by other . "U.S. Appl. No. 11/412,172 Supplemental Notice of Allowability mailed Apr. 17, 2008", SNOA, 4pgs. cited by other.

Primary Examiner: Hofsass; Jeff
Assistant Examiner: Yacob; Sisay
Attorney, Agent or Firm: Schwegman, Lundberg & Woessner, P.A.

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Parent Case Text

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CLAIMS OF PRIORITY

This application claims the benefit under 35 U.S.C. .sctn. 119(e) of U.S. Provisional Application Ser. No. 60/678,903 filed May 4, 2005 entitled "RECORDING USAGE DATA ABOUT RFID CHANNELS".

This application claims the benefit under 35 U.S.C. .sctn. 119(e) of U.S. Provisional Application Ser. No. 60/709,253 filed Aug. 17, 2005 entitled "PREVENTING COMMUNICATION CONFLICT AMONG RFID READERS".

This application claims the benefit under 35 U.S.C. .sctn. 119(e) of U.S. Provisional Application Ser. No. 60/715,917 filed Sep. 9, 2005 entitled "RFID READER SYSTEM CHANGING MODES IN RESPONSE TO DETECTING POSSIBLE TAG READ ERRORS".

This application claims the benefit under 35 U.S.C. .sctn. 119(e) of U.S. Provisional Application Ser. No. 60/751,328 filed Dec. 16, 2005 entitled "RECORDING USAGE DATA ABOUT RFID CHANNELS".

The entire content of each of the above applications is incorporated herein by reference.

CROSS REFERENCE TO RELATED APPLICATIONS

This application may be associated with U.S. application Ser. No. 10/824,049 filed on Apr. 13, 2004, entitled "METHOD AND APPARATUS TO CONFIGURE AN RFID SYSTEM TO BE ADAPTABLE TO A PLURALITY OF ENVIRONMENTAL CONDITIONS".

This application may be associated with U.S. application Ser. No. 10/985,518 filed on Nov. 10, 2004, entitled "RFID TAGS ADJUSTING TO DIFFERENT REGULATORY ENVIRONMENTS, AND RFID READERS TO SO ADJUST THEM AND METHODS".

This application may be associated with U.S. application Ser. No. 11/195,468 filed on Aug. 1, 2005, entitled "PREVENTING COMMUNICATION CONFLICT WITH OTHER RFID READERS".

This application may be associated with U.S. application Ser. No. 11/388,235 filed on Mar. 26, 2006, entitled "ERROR RECOVERY IN RFID READER SYSTEMS".

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Claims

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The claimed invention is:

1. An RFID reader system comprising: an antenna; and an operational processing block coupled to the antenna and operable to select a first one of a plurality of communication channels; identify RF energy detected within the selected channel as a reader system signal from another RFID reader system; decode the identified reader system signal; adjust an own waveform shaping parameter responsive to the decoded reader system signal; and cause the antenna to transmit to RFID tags first RF waves in the selected channel such that second RF waves are backscattered from the RFID tags in response to the first RF waves, in which at least some of one of the first RF waves and the second RF waves have a waveform with a shape according to the adjusted own waveform shaping parameter.

2. The system of claim 1, in which the RF waves having a waveform with a shape according to the adjusted own waveform shaping parameter are the first waves.

3. The system of claim 1, in which the RF waves having a waveform with a shape according to the adjusted own waveform shaping parameter are the second waves.

4. The system of claim 1, in which the own waveform shaping parameter controls a choice of a modulation format.

5. The system of claim 1, in which the own waveform shaping parameter controls a choice of a preamble.

6. The system of claim 1, in which the own waveform shaping parameter controls a choice of a signal encoding.

7. The system of claim 6, in which the own waveform shaping parameter communicates one or a combination: of a data rate, a mode, attributes of a calibration pulse, a rise time, a fall time, a pulse shaping, a pulse width, and a preamble.

8. The system of claim 1, in which the own waveform shaping parameter represents a protocol parameter for an RFID system according to a communications protocol.

9. The system of claim 8, in which the protocol parameter includes a command for a tag to change its state machine.

10. The system of claim 8, in which the protocol parameter includes a command for a tag to respond in a certain manner according to the protocol.

11. The system of claim 1, in which the operational processing block is further operable to interpret an other waveform shaping parameter from the decoded reader system signal, and the own waveform shaping parameter is adjusted responsive to the other waveform shaping parameter.

12. The system of claim 11, in which the other waveform shaping parameter controls a choice of a modulation format.

13. The system of claim 11, in which the other waveform shaping parameter controls a choice of a signal encoding.

14. The system of claim 13, in which the other waveform shaping parameter communicates one or a combination of a data rate, a mode, attributes of a calibration pulse, a rise time, a fall time, a pulse width, and a preamble.

15. The system of claim 11, in which the other waveform shaping parameter represents an other protocol parameter for an RFID system according to a communications protocol.

16. The system of claim 15, in which the other protocol parameter includes a command for a tag to change its state machine.

17. The system of claim 15, in which the other protocol parameter includes a command for a tag to respond in a certain manner according to the protocol.

18. The system of claim 11, in which the other waveform shaping parameter includes an interpreted Q parameter suitable for controlling how an RFID tag generates a random number during an inventorying session, and the own waveform shaping parameter encodes a transmitted Q parameter whose value is determined from a value of the interpreted Q parameter.

19. The system of 18 in which the value of the transmitted Q parameter is the equal to that of the interpreted Q parameter.

20. The system of 18 in which the other waveform shaping parameter does not include a corresponding ACK command, and the transmitted Q parameter has value of zero.

21. An RFID reader system operable to communicate with RFID tags, comprising: selecting means for selecting a first one of a plurality of communication channels; detecting means for detecting RF energy within the selected channel; identifying means for identifying the detected RF energy as a reader system signal from another RFID reader system; decoding means for decoding the identified reader system signal; adjusting means for adjusting an own waveform shaping parameter responsive to the decoded reader system signal; and antenna means for transmitting to the RFID tags first RF waves in the selected channel and for receiving second RF waves backscattered from the RFID tags in response to the first RF waves, at least some of one of the first and second RF waves having a waveform with a shape according to the adjusted own waveform shaping parameter.

22. The system of claim 21, in which the RF waves having a waveform with a shape according to the adjusted own waveform shaping parameter are the first waves.

23. The system of claim 21, in which the RF waves having a waveform with a shape according to the adjusted own waveform shaping parameter are the second waves.

24. The system of claim 21, in which the own waveform shaping parameter controls a choice of a modulation format.

25. The system of claim 21, in which the own waveform shaping parameter controls a choice of a preamble.

26. The system of claim 21, in which the own waveform shaping parameter controls a choice of a signal encoding.

27. The system of claim 21, further comprising: interpreting means for interpreting from the decoded reader system signal an other waveform shaping parameter, and in which the own waveform shaping parameter is adjusted responsive to the other waveform shaping parameter.

28. The system of claim 27, in which the other waveform shaping parameter represents an other protocol parameter for an RFID system according to a communications protocol.

29. The system of claim 28, in which the other protocol parameter includes a command for a tag to change its state machine.

30. The system of claim 28, in which the other protocol parameter includes a command for a tag to respond in a certain manner according to the protocol.

31. The system of claim 27, in which the other waveform shaping parameter includes an interpreted Q parameter suitable for controlling how an RFID tag generates a random number during an inventorying session, and the own waveform shaping parameter encodes a transmitted Q parameter whose value is determined from a value of the interpreted Q parameter.

32. An article comprising: a storage medium, the storage medium having instructions stored thereon, in which when the instructions are executed by at least one component of an RFID reader system that is operable to communicate with RFID tags, they result in: selecting a first one of a plurality of communication channels; detecting RF energy within the selected channel; identifying the detected RF energy as a reader system signal from another RFID reader system; decoding the identified reader system signal; adjusting an own waveform shaping parameter responsive to the decoded reader system signal; and transmitting to the RFID tags first RF waves in the selected channel and receiving second RF waves backscattered from the RFID tags in response to the first RF waves, at least some of one of the first and second RF waves having a waveform with a shape according to the adjusted own waveform shaping parameter.

33. The article of claim 32, in which the RF waves having a waveform with a shape according to the adjusted own waveform shaping parameter are the first waves.

34. The article of claim 32, in which the RF waves having a waveform with a shape according to the adjusted own waveform shaping parameter are the second waves.

35. The article of claim 32, in which the own waveform shaping parameter controls a choice of a modulation format.

36. The article of claim 32, in which the own waveform shaping parameter controls a choice of a preamble.

37. The article of claim 32, in which the own waveform shaping parameter controls a choice of a signal encoding.

38. The article of claim 37, in which the own waveform shaping parameter communicates one or a combination: of a data rate, a mode, attributes of a calibration pulse, a rise time, a fall time, a pulse shaping, a pulse width, and a preamble.

39. The article of claim 32, in which the own waveform shaping parameter represents a protocol parameter for an RFID system according to a communications protocol.

40. The article of claim 39, in which the protocol parameter includes a command for a tag to change its state machine.

41. The article of claim 39, in which the protocol parameter includes a command for a tag to respond in a certain manner according to the protocol.

42. The article of claim 32, in which when the instructions are executed, they further result in: interpreting from the decoded reader system signal an other waveform shaping parameter, and in which the own waveform shaping parameter is adjusted responsive to the other waveform shaping parameter.

43. The article of claim 42, in which the other waveform shaping parameter controls a choice of a modulation format.

44. The article of claim 42, in which the other waveform shaping parameter controls a choice of a signal encoding.

45. The article of claim 44, in which the other waveform shaping parameter communicates one or a combination of a data rate, a mode, attributes of a calibration pulse, a rise time, a fall time, a pulse width, and a preamble.

46. The article of claim 42, in which the other waveform shaping parameter represents an other protocol parameter for an RFID system according to a communications protocol.

47. The article of claim 46, in which the other protocol parameter includes a command for a tag to change its state machine.

48. The article of claim 46, in which the other protocol parameter includes a command for a tag to respond in a certain manner according to the protocol.

49. The article of claim 42, in which the other waveform shaping parameter includes an interpreted Q parameter suitable for controlling how an RFID tag generates a random number during an inventorying session, and the own waveform shaping parameter encodes a transmitted Q parameter whose value is determined from a value of the interpreted Q parameter.

50. The article of claim 49, in which the value of the transmitted Q parameter is the equal to that of the interpreted Q parameter.

51. The article of claim 49, in which the other waveform shaping parameter does not include a corresponding ACK command, and the transmitted Q parameter has value of zero.

52. A method for an RFID reader system to communicate with RFID tags, comprising: selecting a first one of a plurality of communication channels; detecting RF energy within the selected channel; identifying the detected RF energy as a reader system signal from another RFID reader system; decoding the identified reader system signal; adjusting an own waveform shaping parameter responsive to the decoded reader system signal; and transmitting to the RFID tags first RF waves in the selected channel and receiving second RF waves backscattered from the RFID tags in response to the first RF waves, at least some of one of the first and second RF waves having a waveform with a shape according to the adjusted own waveform shaping parameter.

53. The method of claim 52, in which the RF waves having a waveform with a shape according to the adjusted own waveform shaping parameter are the first waves.

54. The method of claim 52, in which the RF waves having a waveform with a shape according to the adjusted own waveform shaping parameter are the second waves.

55. The method of claim 52, in which the own waveform shaping parameter controls a choice of a modulation format.

56. The method of claim 52, in which the own waveform shaping parameter controls a choice of a preamble.

57. The method of claim 52, in which the own waveform shaping parameter controls a choice of a signal encoding.

58. The method of claim 57, in which the own waveform shaping parameter communicates one or a combination: of a data rate, a mode, attributes of a calibration pulse, a rise time, a fall time, a pulse shaping, a pulse width, and a preamble.

59. The method of claim 52, in which the own waveform shaping parameter represents a protocol parameter for an RFID system according to a communications protocol.

60. The method of claim 59, in which the protocol parameter includes a command for a tag to change its state machine.

61. The method of claim 59, in which the protocol parameter includes a command for a tag to respond in a certain manner according to the protocol.

62. The method of claim 52, further comprising: interpreting from the decoded reader system signal an other waveform shaping parameter, and in which the own waveform shaping parameter is adjusted responsive to the other waveform shaping parameter.

63. The method of claim 62, in which the other waveform shaping parameter controls a choice of a modulation format.

64. The method of claim 62, in which the other waveform shaping parameter controls a choice of a signal encoding.

65. The method of claim 64, in which the other waveform shaping parameter communicates one or a combination of a data rate, a mode, attributes of a calibration pulse, a rise time, a fall time, a pulse width, and a preamble.

66. The method of claim 62, in which the other waveform shaping parameter represents an other protocol parameter for an RFID system according to a communications protocol.

67. The method of claim 66, in which the other protocol parameter includes a command for a tag to change its state machine.

68. The method of claim 66, in which the other protocol parameter includes a command for a tag to respond in a certain manner according to the protocol.

69. The method of claim 62, in which the other waveform shaping parameter includes an interpreted Q parameter suitable for controlling how an RFID tag generates a random number during an inventorying session, and the own waveform shaping parameter encodes a transmitted Q parameter whose value is determined from a value of the interpreted Q parameter.

70. The method of 69 in which the value of the transmitted Q parameter is the equal to that of the interpreted Q parameter.

71. The method of 69 in which the other waveform shaping parameter does not include a corresponding ACK command, and the transmitted Q parameter has value of zero.

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Description

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FIELD

The present disclosure relates to Radio Frequency IDentification (RFID) systems, and more particularly, to apparatus, methods, software, and systems to improve the performance of RFID systems, for example responsive to the presence of RF energy in communication channels.

BACKGROUND

Radio Frequency IDentification (RFID) systems typically include RFID tags and RFID readers (the latter are also known as RFID reader/writers or RFID interrogators). RFID systems can be used in many ways for locating and identifying objects to which the tags are attached. RFID systems are particularly useful in product-related and service-related industries for tracking large numbers of objects being processed, inventoried, or handled. In such cases, an RFID tag is usually attached to an individual item, or to its package.

In principle, RFID techniques entail using an RFID reader to interrogate one or more RFID tags. The reader transmitting a Radio Frequency (RF) wave performs the interrogation. A tag that senses the interrogating RF wave responds by transmitting back another RF wave. The tag generates the transmitted back RF wave either originally, or by reflecting back a portion of the interrogating RF wave in a process known as backscatter. Backscatter may take place in a number of ways.

The reflected-back RF wave may further encode data stored internally in the tag, such as a number. The response is demodulated and decoded by the reader, which thereby identifies, counts, or otherwise interacts with the associated item. The decoded data can denote a serial number, a price, a date, a destination, other attribute(s), any combination of attributes, and so on.

An RFID tag typically includes an antenna system, a power management section, a radio section, and frequently a logical section, a memory, or both. In earlier RFID tags, the power management section included an energy storage device, such as a battery. RFID tags with an energy storage device are known as active tags. Advances in semiconductor technology have miniaturized the electronics so much that an RFID tag can be powered solely by the RF signal it receives. Such RFID tags do not include an energy storage device, and are called passive tags.

A reader algorithm has been described in the prior art, whereby an RFID reader chooses a channel, and then first listens to see if another radio-frequency device is operating in it ("listen-before-talk"). If no other radio-frequency device is operating there, the reader operates in that channel. If another radio-frequency device is operating in the channel, the reader moves to a different channel, and again listens, and so on. While this type of algorithm may sometimes be useful in locating an available channel for communication, improvements are needed for RFID operation in the presence of interference and/or noise.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of components of an RFID system.

FIG. 2 is a diagram showing components of a passive RFID tag, such as a tag that can be used in the system of FIG. 1.

FIG. 3 is a conceptual diagram for explaining a half-duplex mode of communication between the components of the RFID system of FIG. 1.

FIG. 4 is a block diagram of a whole RFID reader system according to embodiments.

FIG. 5 is a block diagram of components of an RFID environment according to present embodiments.

FIG. 6A is a flowchart illustrating a method according to present embodiments.

FIG. 6B is a flowchart illustrating an optional variation of the method of FIG. 6A.

FIG. 6C is a flowchart illustrating another optional variation of the method of FIG. 6A.

FIG. 7 illustrates examples of amplitude shift keying (ASK) modulation, and phase reversal amplitude shift keying (PR-ASK) modulation that can be used for RFID communication.

FIGS. 8A and 8B illustrate example reader system RF-power transmit masks that can be used for RFID communication.

FIG. 9 illustrates Tari value, pulse width (PW), and data-1 to data-0 length ratio relative to signals that can be used for RFID communication.

FIG. 10 illustrates FM0 symbols and FM0 sequences that can be used for RFID communication.

FIG. 11 illustrates FM0 preambles that can be used for RFID communication.

FIG. 12 illustrates possible Miller subcarrier sequences that can be used for RFID communication.

FIG. 13 illustrates possible Miller preambles with and without an additional pilot tone.

FIG. 14 is a flowchart illustrating a method according to embodiments.

FIG. 15A is a flowchart illustrating a method according to embodiments.

FIG. 15B is a flowchart illustrating an optional variation of the method of FIG. 15A.

FIG. 15C is a flowchart illustrating another optional variation of the method of FIG. 15A.

FIG. 16 is a flowchart illustrating a method according to embodiments.

FIG. 17A is a flowchart illustrating a method according to embodiments.

FIG. 17B is a flowchart illustrating an optional variation of the method of FIG. 17A.

DETAILED DESCRIPTION

Various embodiments of the present invention will be described in detail with reference to the drawings, where like reference numerals represent like parts and assemblies throughout the several views. Reference to various embodiments does not limit the scope of the invention, which is limited only by the scope of the claims attached hereto. Additionally, any examples set forth in this specification are not intended to be limiting and merely set forth some of the many possible embodiments for the claimed invention.

Throughout the specification and claims, the following terms take at least the meanings explicitly associated herein, unless the context clearly dictates otherwise. The meanings identified below are not intended to limit the terms, but merely provide illustrative examples for the terms. The meaning of "a," "an," and "the" includes plural reference, the meaning of "in" includes "in" and "on." The term "connected" means a direct electrical connection between the items connected, without any intermediate devices. The term "coupled" means either a direct electrical connection between the items connected or an indirect connection through one or more passive or active intermediary devices. The term "circuit" means either a single component or a multiplicity of components, either active and/or passive, that are coupled together to provide a desired function. The term "signal" means at least one current, voltage, charge, temperature, data, or other measurable quantity. The terms "RFID reader" and "RFID tag" are used interchangeably with the terms "reader" and "tag", respectively, throughout the text and claims.

FIG. 1 is a diagram of components of a typical RFID system 100, incorporating aspects of the invention. An RFID reader 110 transmits an interrogating Radio Frequency (RF) wave 112. RFID tag 120 in the vicinity of RFID reader 110 may sense interrogating RF wave 112, and generate wave 126 in response. RFID reader 110 senses and interprets wave 126.

Reader 110 and tag 120 exchange data via wave 112 and wave 126. In a session of such an exchange, each encodes, modulates, and transmits data to the other, and each receives, demodulates, and decodes data from the other. The data is modulated onto, and decoded from, RF waveforms.

Encoding the data in waveforms can be performed in a number of different ways. For example, protocols are devised to communicate in terms of symbols, also called RFID symbols. A symbol for communicating can be a delimiter, a calibration symbol, and so on. Further symbols can be implemented for ultimately exchanging binary data, such as "0" and "1", if that is desired.

Tag 120 can be a passive tag or an active tag, i.e. having its own power source. Where tag 120 is a passive tag, it is powered from wave 112.

FIG. 2 is a diagram of an RFID tag 220, which can be the same as tag 120 of FIG. 1. Tag 220 is implemented as a passive tag, meaning it does not have its own power source. Much of what is described in this document, however, applies also to active tags.

Tag 220 is formed on a substantially planar inlay 222, which can be made in many ways known in the art. Tag 220 also includes two antenna segments 227, which are usually flat and attached to inlay 222. Antenna segments 227 are shown here forming a dipole, but many other embodiments using any number of antenna segments are possible.

Tag 220 also includes an electrical circuit, which is preferably implemented in an integrated circuit (IC) 224. IC 224 is also arranged on inlay 222, and electrically coupled to antenna segments 227. Only one method of coupling is shown, while many are possible.

In operation, a signal is received by antenna segments 227, and communicated to IC 224. IC 224 both harvests power, and decides how to reply, if at all. If it has decided to reply, IC 224 modulates the reflectance of antenna segments 227, which generates the backscatter from a wave transmitted by the reader. Coupling together and uncoupling antenna segments 227 can modulate the reflectance, as can a variety of other means.

In the embodiment of FIG. 2, antenna segments 227 are separate from IC 224. In other embodiments, antenna segments may alternately be formed on IC 224, and so on.

The components of the RFID system of FIG. 1 may communicate with each other in any number of modes. One such mode is called full duplex. Another such mode is called half-duplex, and is described below.

FIG. 3 is a conceptual diagram 300 for explaining the half-duplex mode of communication between the components of the RFID system of FIG. 1, especially when tag 120 is implemented as passive tag 220 of FIG. 2. The explanation is made with reference to a TIME axis, and also to a human metaphor of "talking" and "listening". The actual technical implementations for "talking" and "listening" are now described.

RFID reader 110 and RFID tag 120 talk and listen to each other by taking turns. As seen on axis TIME, when reader 110 talks to tag 120 the communication session is designated as "R.fwdarw.T", and when tag 120 talks to reader 110 the communication session is designated as "T.fwdarw.R". Along the TIME axis, a sample R.fwdarw.T communication session occurs during a time interval 312, and a following sample T.fwdarw.R communication session occurs during a time interval 326. Of course interval 312 is typically of a different duration than interval 326--here the durations are shown approximately equal only for purposes of illustration.

According to blocks 332 and 336, RFID reader 110 talks during interval 312, and listens during interval 326. According to blocks 342 and 346, RFID tag 120 listens while reader 110 talks (during interval 312), and talks while reader 110 listens (during interval 326).

In terms of actual technical behavior, during interval 312, reader 110 talks to tag 120 as follows. According to block 352, reader 110 transmits wave 112, which was first described in FIG. 1. At the same time, according to block 362, tag 120 receives wave 112 and processes it. Meanwhile, according to block 372, tag 120 does not backscatter with its antenna, and according to block 382, reader 110 has no wave to receive from tag 120.

During interval 326, tag 120 talks to reader 110 as follows. According to block 356, reader 110 transmits a Continuous Wave (CW), which can be thought of as a carrier signal that ideally encodes no information. As discussed before, this carrier signal serves both to be harvested by tag 120 for its own internal power needs, and also as a wave that tag 120 can backscatter. Indeed, during interval 326, according to block 366, tag 120 does not receive a signal for processing. Instead, according to block 376, tag 120 modulates the CW emitted according to block 356, so as to generate backscatter wave 126. Concurrently, according to block 386, reader 110 receives backscatter wave 126 and processes it.

In the above, an RFID reader/interrogator may communicate with one or more RFID tags in any number of ways. Some such ways are called protocols. A protocol is a specification that calls for specific manners of signaling between the reader and the tags.

One such protocol is called the Specification for RFID Air Interface-EPC.TM. Radio-Frequency Identity Protocols Class-1 Generation-2 UHF RFID Protocol for Communications at 860 MHz-960 MHz, which is also colloquially known as "the Gen2 Spec". The Gen2 Spec has been ratified by EPCglobal, which is an organization that maintains a website at: <http://www.epcglobalinc.org/> at the time this document is initially filed with the USPTO.

It was described above how reader 110 and tag 120 communicate in terms of time. In addition, communications between reader 110 and tag 120 may be restricted according to frequency. One such restriction is that the available frequency spectrum may be partitioned into divisions that are called channels. Different partitioning manners may be specified by different regulatory jurisdictions and authorities (e.g. FCC in North America, CEPT in Europe, etc.).

The reader 110 typically transmits with a transmission spectrum that lies within one channel. In some regulatory jurisdictions the authorities permit aggregating multiple channels into one or more larger channels, but for all practical purposes an aggregate channel can again be considered a single, albeit larger, individual channel.

Tag 120 can respond with a backscatter that is modulated directly onto the frequency of the reader's emitted CW, also called baseband backscatter. Alternatively, Tag 120 can respond with a backscatter that is modulated onto a frequency, developed by Tag 120, that is different from the reader's emitter CW, and this modulated tag frequency is then impressed upon the reader's emitted CW. This second type of backscatter is called subcarrier backscatter. The subcarrier frequency can be within the reader's channel, can straddle the boundaries with the adjacent channel, or can be wholly outside the reader's channel.

A number of jurisdictions require a reader to hop to a new channel on a regular basis. When a reader hops to a new channel, it may encounter RF energy that could interfere with communications in it.

Embodiments of the present disclosure can be useful in different RFID environments, for example, in the deployment of RFID readers in sparse- or dense-reader environments, in environments with networked and disconnected readers such as where a hand-held reader may enter the field of networked readers, in environments with mobile readers, or in environments with other interference sources. It will be understood that the present embodiments are not limited to operation in the above environments, but may provide improved operation in such environments.

FIG. 4 is a block diagram of a whole RFID reader system 400 according to embodiments. System 400 includes a local block 410, and optionally remote components 470. Local block 410 and remote components 470 can be implemented in any number of ways. It will be recognized that reader 110 of FIG. 1 is the same as local block 410, if remote components 470 are not provided. Alternately, reader 110 can be implemented instead by system 400, of which only the local block 410 is shown in FIG. 1.

Local block 410 is responsible for communicating with the tags. Local block 410 includes a block 451 of an antenna and a driver of the antenna for communicating with the tags. Some readers, like that shown in local block 410, contain a single antenna and driver. Some readers contain multiple antennas and drivers and a method to switch signals among them, including sometimes using different antennas for transmitting and for receiving. And some readers contain multiple antennas and drivers that can operate simultaneously. A demodulator/decoder block 453 demodulates and decodes backscattered waves received from the tags via antenna block 451. Modulator/encoder block 454 encodes and modulates an RF wave that is to be transmitted to the tags via antenna block 451.

Local block 410 additionally includes an optional local processor 456. Processor 456 may be implemented in any number of ways known in the art. Such ways include, by way of examples and not of limitation, digital and/or analog processors such as microprocessors and digital-signal processors (DSPs); controllers such as microcontrollers; software running in a machine such as a general purpose computer; programmable circuits such as Field Programmable Gate Arrays (FPGAs), Field-Programmable Analog Arrays (FPAAs), Programmable Logic Devices (PLDs), and any combination of one or more of these; and so on. In some cases the decoding function in block 453, the encoding function in block 454, or both may be performed instead by processor 456.

Local block 410 additionally includes an optional local memory 457. Memory 457 may be implemented in any number of ways known in the art. Such ways include, by way of examples and not of limitation, nonvolatile memories (NVM), read-only memories (ROM), random access memories (RAM), any combination of one or more of these, and so on. Memory 457, if provided, can include programs for processor 456 to run, if provided.

In some embodiments, memory 457 stores data read from tags, or data to be written to tags, such as Electronic Product Codes (EPCs), Tag Identifiers (TIDs) and other data. Memory 457 can also include reference data that is to be compared to the EPC codes, instructions and/or rules for how to encode commands for the tags, modes for controlling antenna 451, and so on. In some of these embodiments, local memory 457 is provided as a database.

Some components of local block 410 typically treat the data as analog, such as the antenna/driver block 451. Other components such as memory 457 typically treat the data as digital. At some point there is a conversion between analog and digital. Based on where this conversion occurs, a whole reader may be characterized as "analog" or "digital", but most readers contain a mix of analog and digital functionality.

If remote components 470 are indeed provided, they are coupled to local block 410 via an electronic communications network 480. Network 480 can be a Local Area Network (LAN), a Metropolitan Area Network (MAN), a Wide Area Network (WAN), a network of networks such as the internet, and so on. In turn, local block 410 then includes a local network connection 459 for communicating with network 480.

There can be one or more remote component(s) 470. If more than one, they can be located at the same place with each other, or in different places. They can access each other and local block 410 via network 480, or via other similar networks, and so on. Accordingly, remote component(s) 470 can use respective remote network connections. Only one such remote network connection 479 is shown, which is similar to local network connection 459, etc.

Remote component(s) 470 can also include a remote processor 476. Processor 476 can be made in any way known in the art, such as was described with reference to local processor 456.

Remote component(s) 470 can also include a remote memory 477. Memory 477 can be made in any way known in the art, such as was described with reference to local memory 457. Memory 477 may include a local database, and a different database of a Standards Organization, such as one that can reference EPCs.

Of the above-described elements, it is advantageous to consider operational processing block 490. Block 490 includes those that are provided of the following: local processor 456, remote processor 476, local network connection 459, remote network connection 479, and by extension an applicable portion of network 480 that links connection 459 with connection 479. The portion can be dynamically changeable, etc. In addition, block 490 can decode RF waves received via antenna 451, and cause antenna 451 to transmit RF waves according to what it has processed. It can even be said that block 490 can receive RF waves, in which case it is meant that block 490 can receive data about the waves, and so on.

Block 490 includes either local processor 456, or remote processor 476, or both. If both are provided, remote processor 476 can be made such that it operates in a way complementary with that of local processor 456. In fact, the two can cooperate. It will be appreciated that block 490, as defined this way, is in communication with both local memory 457 and remote memory 477, if both are present.

Accordingly, block 490 is location agnostic, in that its functions can be implemented either by local processor 456, or by remote processor 476, or by a combination of both. Some of these functions are preferably implemented by local processor 456, and some by remote processor 476. Block 490 accesses local memory 457, or remote memory 477, or both for storing and/or retrieving data.

Block 490, along with all of the circuits described in this document may be implemented as circuits in the traditional sense. All or some of them can also be implemented equivalently by other ways known in the art, such as by using one or more processors, DSPs, FPGAs, FPAAs, PLDs, combination of hardware and software, etc.

Reader system 400 operates by block 490 generating communications for RFID tags. These communications are ultimately transmitted by antenna block 451, with modulator/encoder block 454 encoding and modulating the information on an RF wave. Then data is received from the tags via antenna block 451, demodulated and decoded by demodulator/decoder block 453, and processed by processing block 490.

Embodiments of the disclosure provide an RFID reader that is capable of the methods described below. In some embodiments software is provided for controlling an RFID reader that operates as per the described methods. The software is not limed to physical locations and can be implemented as a standalone module or as a collection of cooperating distributed modules. The described embodiments may be performed in many ways, including by devices that can perform the described methods. Such devices can be implemented in many ways, as will be obvious to a person skilled in the art in view of the present description.

The operations of this description, such as those of block 490, may be implemented by one or more devices that include logic circuitry. The device(s) perform functions and/or implement methods as described in this document. The device(s) may include a processor that may be programmable for a general purpose, and/or may include a dedicated element or elements such as a microcontroller, microprocessor, DSP, etc. For example, the device(s) may be a digital-computer-like element, such as a general-purpose computer selectively activated or reconfigured by a computer program stored in the computer or in its memory. Alternately, the device may be implemented by an FPGA, FPAA, PLD, Application Specific Integrated Circuit (ASIC), etc.

Moreover, methods are described below. The methods and algorithms presented herein need not be associated with any particular computer or other apparatus. Rather, various general-purpose machines may be used with programs in accordance with the teachings herein, or it may prove more convenient to construct more specialized apparatus to perform the required method steps. The required structure for a variety of these machines will become apparent from this description.

In all cases there should be borne in mind the distinction between methods provided in this description, and methods of operating a computing machine. This description relates both to methods in general, and also to methods for operating a computing machine for processing electrical or other such physical signals to generate other desired physical signals.

Programs are additionally included in this description, as are methods of operation of the programs. A program is generally defined as a group of steps leading to a desired result, due to the nature of the elements in the steps and their sequence. A program is usually advantageously implemented as a sequence of steps for a computing machine, such as a general-purpose computer, a special-purpose computer, a microprocessor, etc.

Storage media are additionally included in this description. Such media, individually or in combination with others, have stored thereon instructions of a program made according to the invention. A storage medium according to the invention is a computer-readable medium, such as a memory, and is read by the computing machine mentioned above.

Performing the steps or instructions of a program requires manipulation of physical quantities. Usually, though not necessarily, these quantities may be transferred, combined, compared, and otherwise manipulated or processed according to the steps or instructions, and they may also be stored in a computer-readable medium. These quantities include, for example, electrical, magnetic, and electromagnetic charges or particles, states of matter, and in the more general case can include the states of any physical devices or elements. It is convenient at times, principally for reasons of common usage, to refer to information represented by the states of these quantities as bits, data bits, samples, values, symbols, characters, terms, numbers, or the like. It should be borne in mind, however, that all of these and similar terms are associated with the appropriate physical quantities, and that these terms are merely convenient labels applied to these physical quantities, individually or in groups.

This detailed description is presented largely in terms of flowcharts, algorithms, and symbolic representations of operations on data bits on and/or within at least one medium that allows computational operations, such as a computer with memory. Indeed, such descriptions and representations are the type of convenient labels used by those skilled in programming and/or the data processing arts to effectively convey the substance of their work to others skilled in the art. A person skilled in the art of programming may use these descriptions to readily generate specific instructions for implementing a pr