Position determination based on phase difference

• US 7,045,996 B2
• Filed: 01/30/2003
• Issued: 05/16/2006
• Est. Priority Date: 01/30/2003
• Status: Expired due to Term

• Current Assignee: Valtrus Innovations Limited (f/k/a Dolya Holdco 9 Limited) (Key Patent Innovations Limited)
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: Pradhan, Salil, Lyon, Geoff M., Patel, Chandrakant
• Primary Examiner(s): Ledynh, Bot
• Assistant Examiner(s): Whittington, Kenneth J.
• Application Number:
  US10/354,112
• Publication Number:
  US 20040150387A1
• Time in Patent Office: 1,202 Days
• Field of Search: 324/207.16, 324/207.18, 324/233, 324/236, 324/207.15, 324/207.11, 324/207.12, 342/42, 342/46, 342/464, 342/450, 257/100, 336/115, 340/10.1, 340/10.2, 340/10.3, 340/10.4, 340/10.5, 340/10.6, 340/539.23, 340/572.6, 340/825.49
• US Class Current: 324/207.16
• CPC Class Codes: G01D 21/00 Measuring or testing not otherwise provided for
• CPC Class Codes: H04B 5/263 Multiple coils at either side
• CPC Class Codes: H04B 5/77 for interrogation

Abstract

A method for determining position of a device includes generating at least two, time-varying, magnetic fields using inductive elements, wherein the fields have differing phases. The method further includes detecting a signal modulated on top of the fields, wherein the signal is generated from the device, and determining a position of the device based on a phase difference of the signal from the device and a reference signal.

Claims

1. A method for determining position of a device comprising steps of:

generating at least two, time-varying, magnetic fields using inductive elements, wherein the at least two fields have differing phases;

detecting a signal, wherein the signal includes data from the device that is modulated on the at least two fields; and

determining a position of the device based on a phase difference of the signal from the device and a reference signal.

2. The method of claim 1, wherein the step of determining a position further comprises determining a position in a single dimension.

3. The method of claim 1, wherein the inductive elements are a pair of coils, and the step of generating at least two fields comprises steps of:

generating a first, time-varying magnetic field with one coil of the pair of coils; and

simultaneously generating a second, time-varying magnetic field with a second coil of the pair of magnetic fields, the second field having a different phase from the first field.

4. The method of claim 3, wherein the first and second fields have the same frequency.

5. The method of claim 1, wherein the signal modulated on the at least two fields is a signal having approximately the same phase as a magnetic field detected by the device in proximity of the inductive elements, the magnetic field detected by the device having components of the at least two, generated, time-varying, magnetic fields.

6. The method of claim 1, wherein the device is a tag.

7. The method of claim 1, wherein the reference signal comprises one of the at least two magnetic fields.

8. An apparatus for detecting position of a device, the apparatus comprising:

an oscillator and driver circuit;

a first inductive element energized by the oscillator and driver circuit to generate a first time-varying magnetic field at a first phase;

a second inductive element energized by the oscillator and driver circuit to generate a second time-varying magnetic field at a second phase;

circuitry associated with detecting and demodulating a signal from the device, wherein the signal includes data from the device that is modulated on the first and second magnetic field; and

processing circuitry determining a position of the device based on a phase difference between the signal and a reference signal.

9. The apparatus of claim 8, wherein the reference signal is one of the first and second time-varying magnetic fields.

10. The apparatus of claim 8, wherein the position is a position in a single dimension.

11. The apparatus of claim 8, wherein the inductive elements are a pair of coils.

12. The apparatus of claim 8, wherein the first and second time-varying fields have approximately the same frequency.

13. The apparatus of claim 8, wherein the signal from the device is a signal having the same phase as a magnetic field detected by the device in proximity of the inductive elements, the magnetic field detected by the device having components of the first and second, time-varying, magnetic fields.

14. The apparatus of claim 8, wherein the circuitry for detecting and demodulating comprises one of the first and second inductive elements.

15. A system for detecting a position of a tag, the system comprising:

at least one reader including inductive elements for generating at least two, time-varying, magnetic fields, wherein the at least two fields have differing phases;

at least one tag including an inductive element for coupling a magnetic field, the coupled magnetic field having components of the at least two, time-varying, magnetic fields, wherein the tag is operable to modulate a signal on the magnetic field, the signal having a phase approximately equal to the coupled magnetic field and the signal including data from the tag that is modulated on the magnetic fields wherein

the at least one reader is operable to receive the modulated signal and determine a position of the tag based on a phase differene, between the signal and a reference signal.

16. The system of claim 15, wherein the reference signal is one of the first and second time-varying magnetic fields.

17. The system of claim 15, wherein the at least one tag comprises circuitry for generating the signal.

18. The system of claim 17, wherein the tag is in proximity of the reader such that the coupling of the magnetic field by the inductive element of the tag is such to generate sufficient energy to energize the circuitiy for generating the signal.

19. An apparatus determining position of a device comprising:

means for generating at least two, time-varying, magnetic fields using inductive elements, wherein the at least two fields have differing phases;

means for detecting a signal, wherein the signal includes data from the device that is modulated on top of the at least two fields; and

means for determining a position of the device based on a phase difference of the signal from the device and a reference signal.

20. The apparatus of claim 19, wherein the reference signal comprises one of the at least two magnetic fields.

21. A system comprising:

at least one electronic device housed in a rack;

a tag connected to the at least one electronic device; and

at least one reader operable to generate an interrogation signal for interrogating the tag using a first inductive element generating a first time-varying magnetic field at a first phase and a second inductive element generating a second time-varying magnetic field at a second phase and operable to interrogate the tag to determine a position of the tag in the rack, wherein the tag generates a signal in response to being interrogated by the at least one reader, wherein the signal includes data from the tag that is modulated on the first and second magnetic fields for transmission to the reader, and the at least one reader is operable to determine the position of the tag based on a phase difference between the signal generated by the tag and a reference signal.

22. The system of claim 21, wherein the reference signal is one of the first time-varying magnetic field and the second time-varying magnetic field.

23. The system of claim 21, wherein the position is a position along a vertical axis of the rack.