System, method and computer program product for calibrating interrogator signal strength and/or tag response range setting

• US 9,087,226 B2
• Filed: 06/09/2006
• Issued: 07/21/2015
• Est. Priority Date: 06/09/2006
• Status: Expired due to Fees

• Current Assignee: Zest Labs, Inc.
• Original Assignee: Intelleflex Corporation
• Inventors: Batra, Naresh, Nandu, Heena
• Primary Examiner(s): Negron, Daniell L
• Assistant Examiner(s): Tang, Son M
• Application Number:
  US11/423,414
• Publication Number:
  US 20070290802A1
• Time in Patent Office: 3,329 Days
• Field of Search: 340/10.31, 340/10.4, 340/572.1, 342/450, 342/451, 342/465
• US Class Current: 1/1
• 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: H04B 17/21 for calibration; for correcting measurements
• CPC Class Codes: H04B 5/77 for interrogation

Abstract

A system, method and computer program product according to one embodiment are provided for calibrating an RFID interrogator. A signal is sent from an interrogator to a calibration device. A backscatter signal is received from the calibration device. The backscatter from the calibration device is analyzed. An outgoing signal strength of the interrogator is adjusted based on the analysis. In a system, method and computer program product according to another embodiment, the interrogator is set to selectively respond to tags returning a backscatter signal strength selected based on the analysis. In a system, method and computer program product according to another embodiment, comparison criteria is selected based on the analysis of the backscatter signal. An RF device is instructed to store the comparison criteria, which is then used by the RF device to selectively respond to an interrogator signal having at least a desired strength.

Claims

1. A method, comprising:

sending a plurality of outgoing signals from an interrogator to a calibration device, wherein each of the outgoing signals has a different outgoing signal strength;

for each of the outgoing signals, storing in a table the outgoing signal strength of the outgoing signal;

for each of the outgoing signals, receiving a corresponding backscatter signal from the calibration device such that a plurality of backscatter signals are received from the calibration device, wherein each of the backscatter signals has a different backscatter signal strength;

for each of the received backscatter signals, storing in the table the backscatter signal strength of the backscatter signal, wherein each of the stored backscatter signal strengths is stored in association with the stored outgoing signal strength of the corresponding outgoing signal that prompted the backscatter signal having the backscatter signal strength;

analyzing the table;

selecting from the table one of the backscatter signal strengths based on the analysis;

setting the interrogator to selectively respond to tags returning backscatter responses having at least the selected backscatter signal strength;

receiving backscatter responses from several tags that are positioned within an effective communication range of the interrogator,

wherein the backscatter responses from the tags that are positioned within the effective communication range of the interrogator comprise;

one or more signals characterized by a signal strength greater than or equal to the selected backscatter signal strength, and

one or more signals characterized by a signal strength less than the selected backscatter signal strength;

selectively responding only to those of the several tags that a backscatter response having at least the selected backscatter signal strength.

2. The method as recited in claim 1,

wherein the table contains historical data.

3. The method as recited in claim 1, wherein the analysis of the table includes analyzing the corresponding backscatter signals for each of the different outgoing signal strengths.

4. The method as recited in claim 1, wherein the table is analyzed at a specified time increment.

5. The method as recited in claim 1, wherein the table is analyzed upon detecting a change in an environmental condition.

6. The method as recited in claim 1, further comprising not responding to the tags returning a backscatter response below the selected backscatter signal strength, wherein the effective communication range of the interrogator is farther than a distance between the interrogator and the calibration device, wherein the tags returning the backscatter response below the selected backscatter signal strength are within the effective communication range.

7. The method as recited in claim 6, wherein an outgoing signal strength used by the interrogator during the receiving the backscatter responses from the several tags that are within the effective communication range of the interrogator at a present outgoing signal strength is the same outgoing signal strength used to selectively respond only to those of the several tags that return the backscatter response having at least the selected backscatter signal strength.

8. The method as recited in claim 1, wherein an outgoing signal strength used by the interrogator during the receiving the backscatter responses from the several tags that are within the effective communication range of the interrogator at a present outgoing signal strength is the same outgoing signal strength used to selectively respond only to those of the several tags that return the backscatter response having at least the selected backscatter signal strength.

9. A method for setting a response comparison criteria for a Radio Frequency (RF) device, comprising:

sending a signal from an interrogator to a calibration device;

receiving a backscatter signal from the calibration device;

analyzing the backscatter from the calibration device;

selecting comparison criteria based on the analysis of the backscatter signal, wherein the comparison criteria includes a minimum allowable interrogator signal level and a maximum allowable interrogator level; and

instructing an RF device to store the comparison criteria, such that the RF device stores the minimum allowable interrogator signal level and the maximum allowable interrogator level,

wherein the comparison criteria is used by the RF device to selectively respond to an interrogator signal having at least the minimum allowable interrogator signal level and less than or equal to the maximum allowable interrogator level.

10. The method as recited in claim 9, wherein the calibration device is located at a known distance from an antenna of the interrogator.

11. The method as recited in claim 9, wherein the calibration device is coupled to a fixed power supply.

12. The method as recited in claim 9, wherein the calibration device is a semi-passive RFID tag.

13. The method as recited in claim 9, wherein the calibration device is a passive RFID tag.

14. The method as recited in claim 9, wherein results of the analysis are maintained in a table.

15. The method as recited in claim 9, wherein results of the analysis are maintained in a table, and

wherein the results of the analysis include analysis of backscatter at differing interrogator power levels.

16. The method as recited in claim 9, further comprising sending a plurality of signals from the interrogator to the RF device, the signals comprising:

interrogator signals having a signal strength less than the minimum allowable interrogator signal level, and

interrogator signals having a signal strength greater than or equal to the minimum allowable interrogator signal level and less than or equal to the maximum allowable interrogator level, and

wherein the RF device selectively responds only to the interrogator signals having the signal strength greater than or equal to the minimum allowable interrogator signal level and less than or equal to the maximum allowable interrogator level, and

wherein each selective response by the RF device is based on comparing the sent interrogator signal to the stored comparison criteria.

17. A Radio Frequency Identification (RFID) system, comprising:

an interrogator sending a plurality of outgoing signals, wherein each of the outgoing signals has a different outgoing signal strength; and

a calibration device backscattering the outgoing signals from the interrogator;

wherein the system is operable such that, for each of the outgoing signals, a table stores the outgoing signal strength of the outgoing signal;

wherein the system is operable such that for each of the outgoing signals, the interrogator receives a corresponding backscatter signal from the calibration device such that a plurality of backscatter signals are received from the calibration device, wherein each of the backscatter signals has a different backscatter signal strength;

wherein the system is operable such that, for each of the received backscatter signals from the calibration device, the table stores the backscatter signal strength of the backscatter signal, wherein each of the stored backscatter signal strengths is stored in association with the stored outgoing signal strength of the corresponding outgoing signal that prompted the backscatter signal having the backscatter signal strength;

wherein the table is analyzed,

wherein the interrogator is set

to selectively respond only to RFID tags returning a backscatter signal having at least a desired strength when the interrogator sends a second outgoing signal at a predetermined strength, and

to not respond to the RFID tags within an effective communications range of the interrogator but returning a backscatter signal below the desired strength when the interrogator sends the second outgoing signal at the predetermined strength,

wherein the desired strength is selected based on the analysis of the table, and the desired strength corresponds, in the table, to the predetermined strength of the second outgoing signal sent by the interrogator.

18. The system as recited in claim 17, wherein each of the RFID tags within the effective communications range of the interrogator are configured to emit a backscatter signal in response to receiving the second outgoing signal at the predetermined strength,

wherein each emitted backscatter signal from one of the RFID tags is one of a plurality of backscatter signals from the RFID tags,

wherein the plurality of backscatter signals from the RFID tags comprise:

one or more backscatter signals from one or more of the RFID tags characterized by a signal strength greater than or equal to the desired strength, and

one or more backscatter signals from one or more of the RFID tags characterized by a signal strength below the desired strength.

19. A Radio Frequency Identification (RFID) system, comprising:

an interrogator configured to send an outgoing signal;

a calibration device configured to backscatter the interrogator signal; and

a plurality of RFID tags,

wherein the RFID tags are set to selectively respond to an interrogator signal having at least a minimum allowable interrogator signal level, and less than or equal to a maximum allowable interrogator level, wherein the minimum allowable interrogator signal level and the maximum allowable interrogator signal level are selected based on an analysis of a signal backscattered from the calibration device to the interrogator.

20. The system as recited in claim 19, wherein the interrogator signal has at least the minimum allowable interrogator signal level,

wherein at least one of the RFID tags that selectively responds to the interrogator signal emits a backscatter signal having a desired backscatter signal strength,

wherein the desired backscatter signal strength is greater than or equal to a strength of the backscatter from the calibration device, and

wherein the interrogator is further set to selectively respond only to backscatter signals having at least the desired backscatter signal strength.

21. A computer program product comprising a non-transitory computer useable medium including a non-transitory computer readable program, wherein the computer readable program when executed on a computing device causes the computing device to:

send a plurality of outgoing signals from an interrogator to a calibration device, wherein each of the outgoing signals has a different outgoing signal strength;

for each of the outgoing signals, store in a table the signal strength of the outgoing signal;

for each of the outgoing signals, receive a corresponding backscatter signal from the calibration device such that a plurality of backscatter signals are received from the calibration device, wherein each of the backscatter signals has a different backscatter signal strength;

for each of the received backscatter signals from the calibration device, store in the table the backscatter signal strength of the backscatter signal, wherein each of the stored backscatter signal strengths is stored in association with the stored outgoing signal strength of the corresponding outgoing signal that prompted the backscatter signal having the backscatter signal strength;

analyze the table; and

set the interrogator to selectively respond only to RFID tags returning a backscatter signal strength selected based on the analysis when the interrogator sends second outgoing signals at a predetermined strength,

wherein the predetermined strength is sufficient to enable effective communications with REID tags that return a backscatter signal below the selected strength when the interrogator sends the second outgoing signals at the predetermined strength, and

wherein the selected backscatter signal strength corresponds, in the table, to the predetermined strength of the second outgoing signals sent by the interrogator.

22. A computer program product comprising a non-transitory computer useable medium including a non-transitory computer readable program, wherein the computer readable program when executed on a computing device causes the computing device to:

send a signal from an interrogator to a calibration device;

receive a backscatter signal from the calibration device;

analyze the backscatter from the calibration device;

select comparison criteria based on the analysis of the backscatter signal, wherein the comparison criteria includes a minimum allowable interrogator signal level and a maximum allowable interrogator level; and

instruct an RF device to store the comparison criteria, such that the RF device stores the minimum allowable interrogator signal level and the maximum allowable interrogator level,

wherein the comparison criteria is used by the RF device to selectively respond to an interrogator signal having at least the minimum allowable interrogator signal level and less than or equal to the maximum allowable interrogator level.

23. The computer program product as recited in claim 22, wherein the computer readable program when executed on a computing device further causes the computing device to:

send a plurality of signals from the interrogator to at least the RF device, the signals comprising;

interrogator signals having a signal strength less than the minimum allowable interrogator signal level, and

interrogator signals having a signal strength greater than or equal to the minimum allowable interrogator signal level and less than or equal to the maximum allowable interrogator level, and

wherein the RF device selectively responds only to the interrogator signals having the signal strength greater than or equal to the minimum allowable interrogator signal level and less than or equal to the maximum allowable interrogator level, and

wherein each selective response by the RF device is based on comparing the sent interrogator signal to the stored comparison criteria.

24. A Radio Frequency Identification (RFID) system, comprising:

an interrogator configured to send a plurality of outgoing signals to a calibration device, and receive a corresponding backscatter signal from the calibration device for each of the outgoing signals, such that a plurality of backscatter signals are received from the calibration device;

wherein the system is operable such that each of the outgoing signals has a different outgoing signal strength,

wherein the system is operable such that, for each of the outgoing signals, a table stores the outgoing signal strength of the outgoing signal,

wherein the system is operable such that each of the backscatter signals has a different backscatter signal strength,

wherein the system is operable such that, for each of the received backscatter signals from the calibration device, the table stores the backscatter signal strength of the backscatter signal, wherein each of the stored backscatter signal strengths is stored in association with the stored outgoing signal strength of the corresponding outgoing signal that prompted the backscatter signal having the backscatter signal strength,

wherein the table is analyzed,

wherein the interrogator is set to selectively respond only to RFID tags returning a backscatter signal having at least a desired strength that is selected based on the analysis of the table,

wherein the interrogator is configured to receive backscatter responses from several RFID tags that are positioned within an effective communication range of the interrogator;

wherein the interrogator is configured to selectively respond only to those of the several RFID tags that return a backscatter response having at least the desired strength.

25. The system as recited in claim 24, wherein the desired strength is selected based on the analysis, and is equal to one of the backscatter signal strengths of one of the backscatter signals received from the calibration device.

26. The system as recited in claim 24, wherein the interrogator is configured to not respond to the RFID tags returning a backscatter response below the desired strength.

27. The system as recited in claim 26, wherein an outgoing signal strength used by the interrogator during the receiving the backscatter responses from the several RFID tags that are within the effective communication range of the interrogator at a present outgoing signal strength is the same outgoing signal strength used to selectively respond only to those of the several RFID tags that return the backscatter response having at least the desired strength.

28. The system as recited in claim 24, wherein an outgoing signal strength used by the interrogator during the receiving the backscatter responses from the several RFID tags that are within the effective communication range of the interrogator at a present outgoing signal strength is the same outgoing signal strength used to selectively respond only to those of the several RFID tags that return the backscatter response having at least the desired strength.

29. The system as recited in claim 24, wherein the backscatter responses include signals having less than the desired strength, and wherein the interrogator is further configured to selectively not respond to the signals having less than the desired strength.

30. A method, comprising:

sending a plurality of outgoing signals from an interrogator to a calibration device, wherein each of the outgoing signals has a different outgoing signal strength;

for each of the outgoing signals, storing in a table the outgoing signal strength of the outgoing signal;

for each of the outgoing signals, receiving a corresponding backscatter signal from the calibration device such that a plurality of backscatter signals are received from the calibration device, wherein each of the backscatter signals has a different backscatter signal strength;

for each of the received backscatter signals from the calibration device, storing in the table the backscatter signal strength of the backscatter signal, wherein each of the stored backscatter signal strengths is stored in association with the stored outgoing signal strength of the corresponding outgoing signal that prompted the backscatter signal having the backscatter signal strength;

analyzing the table; and

setting the interrogator to selectively respond only to RFID tags returning a backscatter signal strength selected based on the analysis when the interrogator sends second outgoing signals at a predetermined strength,

wherein the predetermined strength is sufficient to enable effective communications with RFID tags that return a backscatter signal below the selected strength when the interrogator sends the second outgoing signals at the predetermined strength.

31. The method as recited in claim 30, wherein the backscatter signal strength selected based on the analysis is equal to one of the backscatter signal strengths of one of the backscatter signals received from the calibration device.

32. The method as recited in claim 30, wherein the interrogator is configured to not respond to the RFID tags returning a backscatter response below the selected backscatter signal strength.

33. The method as recited in claim 30, further comprising:

receiving one or more returning backscatter signals from the RFID tags, at least some of the returning backscatter signals being below the selected strength;

analyzing the one or more returning backscatter signals; and

selectively not responding to the returning the backscatter signals below the selected strength.

34. A Radio Frequency Identification (RFID) system, comprising at least one interrogator configured to:

send a plurality of calibration signals from the interrogator to a calibration device, wherein each of the calibration signals has a different calibration signal strength;

receive a plurality of calibration backscatter signals from the calibration device in response to the calibration device receiving the calibration signals, wherein each of the calibration backscatter signals corresponds to one of the calibration signals, and each of the calibration backscatter signals has a different calibration backscatter signal strength;

wherein the system is operable such that, for each of the calibration signals, a table stores the calibration signal strength of the calibration signal;

wherein the system is operable such that for each of the received calibration backscatter signals from the calibration device, the table stores the calibration backscatter signal strength of the calibration backscatter signal, wherein each of the stored calibration backscatter signal strengths is stored in association with the stored calibration signal strength of the corresponding calibration signal that prompted the calibration backscatter signal having the calibration backscatter signal strength;

analyze the table;

define an interrogator signal strength based on the analysis;

select a backscatter signal strength based on the analysis, wherein the selected backscatter signal strength corresponds, in the table, to the interrogator signal strength defined based on the analysis;

set the interrogator to;

send signals at the interrogator signal strength; and

selectively respond to tags returning backscatter responses having at least the selected backscatter signal strength;

send one or more signals from the interrogator to a plurality of tags, each signal being characterized by the interrogator signal strength;

receive a backscatter response signal from at least one of the tags in response to the tag receiving the one or more signals from the interrogator, each backscatter response signal being characterized by a backscatter response signal strength;

receive backscatter responses from the tags; and

selectively respond only to those of the plurality of tags that return a backscatter response having at least the selected backscatter signal strength.

35. The method as recited in claim 34, wherein the interrogator is set to selectively respond to one or more tags located within an effective communication range of the interrogator based on one or more of the interrogator signal strength and the backscatter response signal strength.

36. The method as recited in claim 34, wherein the interrogator is set to selectively respond to one or more tags located within an effective communication range of the interrogator based on the interrogator signal strength and the backscatter response signal strength.