Electronic identification label and interrogator for use therewith

• US 20040217171A1
• Filed: 04/29/2003
• Published: 11/04/2004
• Est. Priority Date: 04/29/2003
• Status: Active Grant

• Current Assignee: Round Rock Research LLC
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: Blakley, Daniel Robert, Way, Olan, Betrabet, Chinmay, Weng, Jian-Gang, deVos, John A.
• Granted Patent: US 7,014,112 B2
• Time in Patent Office: Days
• US Class Current: 235/451
• 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 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer

Abstract

A method of conveying information from an electronic identification label to an interrogator includes coupling energy from an external field into a resonant circuit of the electronic identification label. The method also includes the electronic identification label periodically storing and discharging an amount of the coupled energy wherein the period that the electronic identification label stores and discharges the energy conveys information about the electronic identification label to the interrogator.

Claims

1. A method of conveying information from an electronic identification label to an interrogator, comprising:

coupling energy from an external field to a resonant circuit of the electronic identification label;

the electronic identification label periodically storing and discharging an amount of the coupled energy; and

wherein the period of the storing and discharging conveys information about the electronic identification label to the interrogator.

2. The method of claim 1, additionally comprising the interrogator exciting an external field-generating device;

and

the interrogator counting the changes per unit time in the input impedance of the external field-generating device that occur when the electronic identification label periodically stores and discharges the amount of the coupled energy.

3. The method of claim 1, wherein the periodic storing and discharging step further comprises storing electrical charge on at least one capacitor within an energy storage device associated with the electronic identification label.

4. The method of claim 3, wherein the periodic storing and discharging step further comprises switching a resistor to the energy storage device associated with the electronic identification label.

5. The method of claim 4, wherein the resistor is a conductive trace to ground.

6. The method of claim 1, further comprising latching the resistor to the energy storage device to bring about a substantially complete discharge of the energy storage device.

7. The method of claim 1, wherein the energy storage device associated with the electronic identification label is at least one capacitor in an astable multivibrator circuit.

8. The method of claim 1, further comprising:

coupling energy from the external field into a second resonant circuit of the electronic identification label; and

the electronic identification label periodically storing and discharging an amount of the energy coupled into the second resonant circuit,

wherein the period during which the electronic identification label stores and discharges the energy coupled into the second resonant circuit conveys timing information to the interrogator that accompanies the information about the electronic identification label.

9. The method of claim 8, wherein the information about the electronic identification label is measured by way of measuring a change in the input impedance to a field-generating device operating at a first frequency, and wherein the timing information is measured by way of measuring a change in the input impedance to a field-generating device operating at a second frequency.

10. A method of interrogating an electronic identification label, comprising:

placing the electronic identification label within a coupling distance of a first and second field-generating device, the electronic identification label having first and second resonant circuits operating at a corresponding first and second frequency;

counting changes in the input impedance of the first field-generating device and the changes in the input impedance of the field-generating device; and

comparing the number of changes in the input impedance of the first field-generating device to the number of changes in the input impedance of the second field-generating device.

11. The method of claim 10, wherein the changes in the input impedance of the first field-generating device are brought about by switching a resistor in parallel with elements of the first resonant circuit.

12. The method of claim 11, wherein switching of the resistor into the first resonant circuit is performed substantially simultaneously with the discharge of energy stored on a storage device coupled to the first resonant circuit.

13. The method of claim 10, wherein the change in the input impedance of the second resonant circuit is brought about by switching a resistor in parallel with elements of the second resonant circuit.

14. The method of claim 13, wherein switching of the resistor into the second resonant circuit is performed substantially simultaneously with the discharge of energy stored on a storage device coupled to the second resonant circuit.

15. The method of claim 10, wherein the change in the input impedance of the first field-generating device is brought about by creating a substantially open circuit in the first resonant circuit.

16. The method of claim 10, wherein the change in the input impedance of the second field-generating device is brought about by creating a substantially open circuit in the second resonant circuit.

17. An electronic identification label, comprising:

first and second resonant circuits;

first and second energy storage devices coupled to a corresponding resonant circuit, for storing energy coupled into the first and second resonant circuits;

first and second switching devices placed between the first and second resonant circuits and the corresponding energy storage device; and

first and second circuit elements that are periodically coupled and decoupled from the corresponding resonant circuits by way of the corresponding first and second switching devices, wherein

the rate at which the second circuit element is coupled and decoupled from the second resonant circuit compared to the rate at which the first circuit element is coupled and decoupled from the first resonant circuit conveys information from the electronic identification label to an interrogator.

18. The electronic identification label of claim 17, wherein at least one of the first and second energy storage devices is a capacitor.

19. The electronic identification label of claim 17, wherein at least one of the first and second switching devices includes at least one transistor.

20. The electronic identification label of claim 17, wherein at least one of the first and second circuit elements is a resistor.

21. The electronic identification label of claim 20, wherein at least one of the first and second switching devices periodically couple the resistor to the corresponding energy storage device, thereby removing a substantial portion of energy from the corresponding energy storage device.

22. An electronic identification label, comprising:

means for wirelessly receiving energy at a predetermined frequency from an external source;

means for storing the received energy; and

means for periodically coupling and decoupling a circuit element into and out of the means for wirelessly receiving energy, wherein

the period of the coupling and decoupling is determined by the amount of energy that can be stored in the means for storing the coupled energy.

23. The electronic identification label of claim 22, wherein the means for wirelessly receiving energy is a resonant circuit.

24. The electronic identification label of claim 22, wherein the period of the coupling and decoupling of the circuit element conveys information about the electronic identification label to an interrogator.

25. The electronic identification label of claim 22, further comprising:

second means for wirelessly receiving energy at a second predetermined frequency;

means for storing the received energy received by the second means for wirelessly receiving energy;

second means for periodically coupling and decoupling a circuit element into and out of the second means for wirelessly receiving energy, wherein

the period of the coupling and decoupling of the circuit element into and out of the second means for wirelessly receiving energy is used to derive timing information used to measure the information about the electronic identification label.

26. An interrogator for use with an electronic identification label;

comprising;

a field-generating device that radiates energy at a first frequency to the electronic identification label;

a sensor that senses the changes in the quality factor of the electronic identification label at the first frequency;

a field-generating device that radiates energy at a second frequency to the electronic identification label;

a sensor that senses the changes in the quality factor of the electronic identification label at the second frequency; and

a processor that determines the respective number of changes in the quality factor at the first and second frequencies and compares the two numbers.

27. The interrogator of claim 26, wherein changes in the quality factor of the electronic identification label at the first frequency are measured as changes in the input impedance of the field-generating device operating at the first frequency.

28. The interrogator of claim 26, wherein the processor uses the count of the changes in the quality factor at the first frequency to define a data frame, within which the count of the changes in the quality factor at the second frequency are measured.

29. The interrogator of claim 26, wherein the processor uses the count of the changes in the quality factor at the second frequency to extract information about the electronic identification label.

30. The interrogator of claim 26, wherein the field-generating device is an inductor that generates a magnetic field.

31. A method of interrogating an electronic identification label, comprising the steps of:

coupling energy from an external field into a resonant circuit of an electronic identification label;

storing and discharging an amount of the energy coupled to the resonant circuit according to a period;

conveying a signal that represents the period to a memory device; and

the memory device outputting a plurality of binary digits clocked by way of the signal representing the period.

32. The electronic identification label of claim 31, further comprising the memory device dividing the signal that represents the period and wherein the binary digits output from the memory device have a period based on the divided signal.

33. The method of claim 32, further comprising coupling energy from the external field to a second resonant circuit of the electronic identification label, an amount of the energy coupled to the second resonant circuit being supplied to the memory device.

34. The method of claim 31, wherein the output of the memory device is used to control the coupling of a resistor to a second resonant circuit.

35. The method of claim 34, wherein the coupling and decoupling of the resistor to the second resonant circuit influences the input impedance to a device that generates the external field.

36. An electronic identification label comprising:

a resonant circuit that receives an amount of energy from a field-generating device;

an energy storage device that stores and discharges energy received from the resonant circuit according to a period; and

a memory device that accepts a signal representing the period and outputs a code at a bit rate derived from the period, wherein

the period is a function of a coupling distance of the field-generating device to the electronic identification label.

37. The electronic identification label of claim 36, wherein the code output from the memory device is used to control the coupling and decoupling of a resistive device into and out of a second resonant circuit.

38. The electronic identification label of claim 37, wherein the second resonant circuit receives an amount of energy from a second field-generating device within the coupling distance to the second resonant circuit.

39. An interrogator for use with an electronic identification label;

comprising;

first and second field-generating devices that convey energy to the electronic identification label;

first and second impedance sensors, each coupled to a corresponding one of the first and second field-generating devices; and

a processor, coupled to the first and second impedance sensors, which uses the timing of changes in the input impedance of the first sensor to establish a time base for reading changes in the input impedance of the second sensor.

40. The interrogator of claim 39, further comprising a first and second signal generator for generating signals at a first and second frequency for coupling to the first and second field-generating devices.

41. The interrogator of claim 39, wherein the first and second field-generating devices are inductive devices.