Ramped interrogation power levels

• US 20070018793A1
• Filed: 07/20/2005
• Published: 01/25/2007
• Est. Priority Date: 07/20/2005
• Status: Active Grant

• Current Assignee: Zest Labs, Inc.
• Original Assignee: Intelleflex Corporation
• Inventors: Stewart, Roger, Bemiss, William
• Granted Patent: US 8,872,633 B2
• Time in Patent Office: Days
• US Class Current: 340/10.300
• 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 7/10029 the collision being resolved in the time domain, e.g. using binary tree search or RFID responses allocated to a random time slot
• CPC Class Codes: G06K 7/10356 using a plurality of antennas, e.g. configurations including means to resolve interference between the plurality of antennas

Abstract

A method for communicating with a plurality of radio frequency (RF) devices includes transmitting a first signal at a first power level, interrogating RF devices responding to the first signal, instructing the responding RF devices to change state, and transmitting a second signal at a second power level higher than the first power level. The RF devices responding to the first signal do not respond to the second signal upon changing state.

Claims

1. A method for communicating with a plurality of radio frequency (RF) devices, comprising:

transmitting a first signal at a first power level;

interrogating RF devices responding to the first signal;

instructing the responding RF devices to change state; and

transmitting a second signal at a second power level higher than the first power level,

wherein one or more of the RF devices responding to the first signal do not respond to the second signal upon changing state.

2. The method of claim 1, wherein the second power level is a maximum power level allowed by law.

3. The method of claim 1, further comprising interrogating RF devices responding to the second signal, instructing the RF devices responding to the second signal to change state, and transmitting a third signal at a third power level higher than the second power level.

4. The method of claim 3, wherein the third power level is a maximum power level allowed by law.

5. The method of claim 1, wherein the RF devices responding to the first signal enter a sleep mode upon changing state.

6. The method of claim 1, wherein the RF devices responding to the first signal enter a nonresponsive mode upon changing state.

7. The method of claim 1, wherein the first power level is selected to provide a predetermined effective interrogation range from a transmitter transmitting the signals, wherein the second power level is selected to provide a larger predetermined effective interrogation range from a transmitter transmitting the signals.

8. The method of claim 1, wherein a time period of transmission of the fist signal is about the same as a time period of transmission of the second signal.

9. The method of claim 1, wherein a time period of transmission of the fist signal is different than a time period of transmission of the second signal.

10. The method of claim 1, wherein a time period of transmission of the first signal is dependent upon a result of a protocol search.

11. The method of claim 10, wherein the time period of transmission of the first signal is dependent upon a number of the RF devices responding to the first signal.

12. The method of claim 1, wherein a variation in a backscattering power level of the RF devices located within a maximum effective communication range is less than about 100:

1.

13. The method of claim 1, wherein a backend system selects an amount of time to remain at each power level.

14. The method of claim 1, wherein a backend system selects each power level.

15. The method of claim 1, wherein a Radio Frequency Identification (RFID) reader performs the method, wherein the RF devices are RFID tags.

16. A method for communicating with a plurality of radio frequency (RF) devices, comprising:

transmitting a signal at a first power level;

continuously increasing the signal to a second power level;

interrogating RF devices responding to the signal;

instructing at least some of the responding RF devices to change state such that the RF devices do not respond to the signal upon changing state.

17. The method of claim 16, wherein the RF devices responding to the first signal enter a sleep mode upon changing state.

18. The method of claim 16, wherein the RF devices responding to the first signal enter a nonresponsive mode upon changing state.

19. The method of claim 16, further comprising stepping to a third power level greater than the second power level.

20. The method of claim 16, further comprising initially transmitting at a third power level smaller than the first power level and stepping to the first power level.

21. The method of claim 16, wherein a speed that the power level is increased from the first to the second power level is about constant.

22. The method of claim 16, wherein a speed that the power level is increased from the first to the second power level varies.

23. The method of claim 16, wherein a time period of transmission at the first power level is dependent upon a number of the RF devices responding to the first signal.

24. The method of claim 16, wherein a variation in a backscattering power level of the RF devices located within a maximum effective communication range is less than about 100:

1.

25. The method of claim 16, wherein a backend system selects an amount of time before the power level is increased from the first to the second power level.

26. The method of claim 16, wherein an RFID reader performs the method, wherein the RF devices are RFID tags.

27. A method for communicating with a plurality of radio frequency (RF) devices, comprising:

transmitting a series of signals, each sequential signal being transmitted at an increased power level; and

at each power level;

singulating RF devices responding to the signal;

instructing the responding RF devices to change to an unresponsive state.

28. The method of claim 27, wherein the unresponsive state is a sleep mode.

29. The method of claim 27, wherein a time period of transmission of each signal is about the same.

30. The method of claim 27, wherein a time period of transmission of each signal is different.

31. The method of claim 27, wherein a time period of transmission of each signal is dependent upon a result of a protocol search.

32. The method of claim 27, wherein a variation in a backscattering power level of the RF devices located within a maximum effective communication range is less than about 100:

1.

33. The method of claim 27, wherein a backend system selects an amount of time to remain at each power level.

34. The method of claim 27, wherein a backend system selects each power level.

35. The method of claim 27, wherein a Radio Frequency Identification (RFID) reader performs the method, wherein the RF devices are RFID tags.

36. The method of claim 27, wherein a backend system controls performance of the method, wherein the RF devices are RFID tags.

37. A system for communicating with a plurality of radio frequency (RF) devices, comprising:

a first reader;

a second reader spaced apart from the first reader;

a plurality of first tags closer to the first reader than the second reader;

a plurality of second tags closer to the second reader than the first reader;

wherein the first reader uses a combination of varying a transmitting power level when communicating with the first tags and instructing the first tags to become nonresponsive such that backscatter signals from the first tags received by the second reader are always less than a minimum effective backscatter signal from any second tag at the second reader.

38. A system for communicating with a plurality of radio frequency (RF) devices, comprising:

a first reader having a first effective communication range;

a second reader spaced apart from the first reader and having a second effective communication range;

a plurality of first tags closer to the first reader than the second reader;

a plurality of second tags closer to the second reader than the first reader;

wherein the first reader uses a combination of varying a transmitting power level when communicating with the first tags and instructing the first tags to become nonresponsive such that the first reader and the second reader are operable in a same communications channel at a distance from each other of about 10 times the first effective communications range.

39. A system for communicating with a plurality of radio frequency (RF) devices, comprising:

a first reader having a first effective communication range;

a second reader spaced apart from the first reader and having a second effective communication range;

a plurality of first tags closer to the first reader than the second reader;

a plurality of second tags closer to the second reader than the first reader;

wherein the first reader uses a combination of varying a transmitting power level when communicating with the first tags and instructing the first tags to become nonresponsive such that the first reader and the second reader are operable in a same communications channel at a distance from each other of about 10 times the second effective communications range.

40. A radio frequency (RF) reader configured to sequentially control its output levels in coordination with interrogation of tags.

41. A radio frequency (RF) system, comprising:

a plurality of RF readers;

a plurality of RF tags in communication with the readers;

a reader network coordinator that controls and coordinates a multiplicity of RF readers to minimize backscatter jamming between the tags and the readers.

42. A radio frequency (RF) system, comprising:

a plurality of RF readers;

a plurality of RF tags in communication with the readers;

a reader network coordinator that controls and coordinates a multiplicity of RF readers to minimize forward link jamming between the tags and the readers.

43. A reader that controls both a variable output level thereof and a protocol such that the output level depends on a result of a protocol search.

44. A method for communicating with radio frequency (RF) devices, comprising:

listening for a signal;

if no signal is present, sending a query;

interrogating RF devices responding to the query.

45. The method of claim 44, further comprising, if a signal is detected during the listening, waiting for a period of time and repeating the method.

46. The method of claim 45, wherein the period of time is a random value.

47. The method of claim 44, further comprising waiting for a period of time and repeating the method if no RF device respond to the query.

48. The method of claim 47, wherein the period of time is a random value.

49. The method of claim 44, further comprising adjusting a power level used during the interrogation from a first level to a second level.

50. The method of claim 44, wherein a Radio Frequency Identification (RFID) reader performs the method, wherein the RF devices are RFID tags.

51. The method of claim 44, wherein a backend system determines when to listen for the signal.

52. A method for communicating with Radio Frequency Identification (RFID) devices, comprising:

coordinating sending of queries by a plurality of RFID interrogators such that the queries do not temporally overlap each other;

further coordinating sending of the queries by the plurality of RFID interrogators such that the queries do not temporally overlap with a communication between one of the interrogators and an RF device.

53. A method for communicating with Radio Frequency Identification (RFID) devices, comprising:

coordinating sending of queries by a plurality of RFID interrogators such that the queries do not temporally overlap each other;

adjusting a power level of one of the interrogators communicating with an RF device such that the communication do not interfere with simultaneously performed queries.

54. A method for communicating with Radio Frequency Identification (RFID) devices, comprising:

coordinating sending of queries by a plurality of RFID interrogators such that the queries do not temporally overlap each other;

adjusting a power level of the interrogators sending queries such that the queries do not interfere with a simultaneously performed communication between one of the interrogators and an RF device.