Method, system, and apparatus for remote data calibration of a RFID tag population

• US 6,956,509 B2
• Filed: 08/26/2004
• Issued: 10/18/2005
• Est. Priority Date: 02/12/2001
• Status: Expired due to Term

• Current Assignee: Symbol Technologies, LLC (Zebra Technologies Corporation)
• Original Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Inventors: Bandy, William R., Powell, Kevin J., Shanks, Wayne E., Arneson, Michael R.
• Primary Examiner(s): WAMSLEY, PATRICK G
• Application Number:
  US10/926,269
• Publication Number:
  US 20050040974A1
• Time in Patent Office: 418 Days
• Field of Search: 341/53, 235/375, 705/28, 340/10.2, 340/10.3, 340/10.32, 340/10.33, 340/505, 340/572.1, 340/572.3, 340/572.7, 340/825.52, 342/42, 342/44
• US Class Current: 341/53
• CPC Class Codes: G06K 17/00 Methods or arrangements for effecting co-operative working between equipments covered by two or more of main groups G06K1/00 - G06K15/00, e.g. automatic card files incorporating conveying and reading operations
• CPC Class Codes: G06K 19/0713 the arrangement including a power charge pump
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• CPC Class Codes: G06K 19/07749 the record carrier being capable of non-contact communication, e.g. constructional details of the antenna of a non-contact smart card
• CPC Class Codes: G06K 19/07767 the first and second communication means being two different antennas types, e.g. dipole and coil type, or two antennas of the same kind but operating at different frequencies
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• CPC Class Codes: G06K 7/10039 interrogator driven, i.e. synchronous
• CPC Class Codes: G06K 7/10069 the collision being resolved in the frequency domain, e.g. by hopping from one frequency to the other frequency hopping or spread spectrum techniques H04B7/00
• CPC Class Codes: G06K 7/10108 interrogating only those RFIDs that fulfill a predetermined requirement, e.g. selecting all RFIDs having the same speed and moving in a cloud like fashion, e.g. on the same train; interrogating only RFIDs having a certain predetermined temperature, e.g. in the same fridge, another possibility being the active ignoring of a group of tags that fulfill a predetermined requirement, equivalent to the Boolean NOT operation
• CPC Class Codes: G06K 7/10356 using a plurality of antennas, e.g. configurations including means to resolve interference between the plurality of antennas
• CPC Class Codes: G08B 13/2485 Simultaneous detection of multiple EAS tags
• CPC Class Codes: G11C 5/142 Contactless power supplies, e.g. RF, induction, or IR
• CPC Class Codes: H04L 7/0331 with a digital phase-locked loop [PLL] processing binary samples, e.g. add/subtract logic for correction of receiver clock H04L7/0337 takes precedence

Abstract

A method, system, and apparatus for remotely calibrating data symbols received by a radio frequency identification (RFID) tag population are described. Tags are interrogated by a reader, which may be located in a network of readers. The reader transmits data symbols to the tags. Tags respond to the interrogations with symbols that each represent one or more bits of data. To calibrate the tags, the reader transmits a plurality of pulses of different lengths to the tag population. The tags receive the plurality of pulses. A characteristic of each pulse, such as a pulse length, is stored by the tags. The stored pulse lengths are used to define different data symbols that are subsequently received by the tags from the reader.

Claims

1. A method for defining data symbols in a radio frequency identification (RFID) tag device, comprising:

(a) receiving a first calibration pulse on an input signal;

(b) detecting a physical characteristic of the received first calibration signal; and

(c) storing the detected physical characteristic of the received first calibration signal as a stored first characteristic;

wherein a received data symbol is determined to be a first data value if a physical characteristic of the received data symbol has a first predetermined relationship with the stored first characteristic; and

wherein the received data symbol is determined to be a second data value if the physical characteristic of the received data symbol has a second predetermined relationship with the stored first characteristic.

2. The method of claim 1, further comprising:

(d) receiving a second calibration signal;

(e) detecting a physical characteristic of the received second calibration signal; and

(f) storing the detected physical characteristic of the received second calibration signal as a stored second characteristic;

wherein the received data symbol is determined to be the second data value if the physical characteristic of the received data symbol has the second predetermined relationship with the stored first characteristic and a first predetermined relationship with the stored second characteristic.

3. The method of claim 2, wherein the received data symbol is determined to be a third data value if the physical characteristic of the receive data symbol has a second predetermined relationship with the stored second characteristic.

4. The method of claim 3, wherein the physical characteristic of the received first calibration signal is a length of a pulse portion of the received first calibration signal, and wherein the physical characteristic of the received second calibration signal is a length of a pulse portion of the received second calibration signal, wherein step (b) comprises:

detecting the length of the pulse portion of the received first calibration signal;

wherein step (c) comprises;

storing the detected length of the pulse portion of the received first calibration signal;

wherein step (e) comprises;

detecting the length of the pulse portion of the received second calibration signal; and

wherein step (f) comprises;

storing the detected length of the pulse portion of the received second calibration signal.

5. The method of claim 4, wherein the physical characteristic of the received data symbol is a length of a pulse portion of the received data symbol;

wherein the received data symbol is determined to be the first data value if the length of the pulse portion of the received data symbol is less than the stored length of the pulse portion of the received first calibration signal;

wherein the received data symbol is determined to be the second data value if the length of the pulse portion of the received data symbol is greater than the stored length of the pulse portion of the received first calibration signal and less than the stored length of the pulse portion of the received second calibration signal; and

wherein the received data symbol is determined to be the third data value if the length of the pulse portion of the received data symbol is greater than the stored length of the pulse portion of the received second calibration signal.

6. The method of claim 3, further comprising:

(g) defining the first data value as a 0 bit; and

(h) defining the second data value as a 1 bit; and

(i) defining the third data value as a Null bit.

7. The method of claim 3, further comprising:

(g) defining the first data value as a 1 bit; and

(h) defining the second data value as a 0 bit; and

(i) defining the third data value as a Null bit.

8. The method of claim 1, wherein the physical characteristic of the received first calibration signal is a length of a pulse portion of the received first calibration signal, wherein step (b) comprises:

detecting the length of the pulse portion of the received first calibration signal; and

wherein step (c) comprises;

storing the detected length of the pulse portion the received first calibration signal.

9. The method of claim 8, wherein the physical characteristic of the received data symbol is a length of a pulse portion of the received data symbol;

wherein the received data symbol is determined to be the first data value if the length of the pulse portion of the received data symbol is less than the stored length of the pulse portion of the received first calibration signal; and

wherein the received data symbol is determined to be the second data value if the length of the pulse portion of the received data symbol is greater than the stored length of the pulse portion of the received first calibration signal.

10. The method of claim 1, further comprising:

(d) defining the first data value as a 0 bit; and

(e) defining the second data value as a 1 bit.

11. The method of claim 1, further comprising:

(d) defining the first data value as a 1 bit; and

(e) defining the second data value as a 0 bit.

12. A system for defining data symbols in a radio frequency identification (RFID) tag device, comprising:

means for receiving a first calibration pulse on an input signal;

means for detecting a physical characteristic of the received first calibration signal; and

means for storing the detected physical characteristic of the received first calibration signal as a stored first characteristic;

means for determining a received data symbol to be a first data value if a physical characteristic of the received data symbol has a first predetermined relationship with the stored first characteristic, or to be a second data value if the physical characteristic of the received data symbol has a second predetermined relationship with the stored first characteristic.

13. The system of claim 12, further comprising:

means for receiving a second calibration signal;

means for detecting a physical characteristic of the received second calibration signal; and

means for storing the detected physical characteristic of e received second calibration signal as a stored second characteristic;

wherein said means for determining comprises means for determining the received data symbol to be the second data value if the physical characteristic of the received data symbol has the second predetermined relationship with the stored first characteristic and a first predetermined relationship with the stored second characteristic.

14. The system of claim 13, wherein said means for determining further comprises means for determining the received data symbol to be a third data value if the physical characteristic of the received data symbol has a second predetermined relationship with the stored second characteristic.

15. The system of claim 14, wherein the physical characteristic of the received first calibration signal is a length of a pulse portion of the received first calibration signal, and wherein the physical characteristic of the received second calibration signal is a length of a pulse portion of the received second calibration signal.

16. The system of claim 15, wherein the physical characteristic of the received data symbol is a length of a pulse portion of the received data symbol;

wherein said means for determining comprises means for determining the received data symbol to be the first data value if the length of the pulse portion of the received data symbol is less than the stored length of the pulse portion of the received first calibration signal, to be the second data value if the length of the pulse portion of the received data symbol is greater than the stored length of the pulse portion of the received first calibration signal and less than the stored length of the pulse portion of the received second calibration signal, or to be the third data value if the length of the pulse portion of the received data symbol is greater than the stored length of the pulse portion of the received second calibration signal.

17. The system of claim 12, wherein the physical characteristic of the received first calibration signal is a length of a pulse portion of the received first calibration signal, wherein said means for detecting comprises:

means for detecting the length of the pulse portion of the received first calibration signal; and

wherein said means for storing comprises;

means for storing the detected length of the pulse portion of the received first calibration signal.

18. The system of claim 12, wherein the physical characteristic of the received data symbol is a length of a pulse portion of the received data symbol;

wherein said means for determining comprises means for determining the received data symbol to be the first data value if the length of the pulse portion of the received data symbol is less than the stored length of the pulse portion of the received first calibration signal, or to be the second data value if the length of the pulse portion of the received data symbol is greater than the stored length of the pulse portion of the received first calibration signal.