Near field electromagnetic positioning system and method

• US 7,298,314 B2
• Filed: 10/04/2004
• Issued: 11/20/2007
• Est. Priority Date: 08/19/2002
• Status: Active Grant

• Current Assignee: GaN Corporation
• Original Assignee: Q-Track Corporation
• Inventors: Schantz, Hans Gregory, Langford, David Wesley
• Primary Examiner(s): Lobo; Ian J.
• Application Number:
  US10/958,165
• Publication Number:
  US 20050046608A1
• Time in Patent Office: 1,142 Days
• Field of Search: 342/90, 342/125, 342/174
• US Class Current: 342/125
• CPC Class Codes: G01S 11/06 using intensity measurements
• CPC Class Codes: G01S 13/75 using transponders powered from received waves, e.g. using passive transponders , or using passive reflectors
• CPC Class Codes: G01S 5/0027 of actual mobile position, i.e. position determined on mobile
• CPC Class Codes: G01S 5/0081 Transmission between base stations
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location
• CPC Class Codes: H04B 5/24 Inductive coupling

Abstract

A system and method for electromagnetic position determination utilizing a calibration process. For calibration, a transmitter is positioned at multiple locations in an area of interest and multiple receivers receive and record signal characteristics from the transmitter to generate a calibration data set. The unknown position of a transmitter may be determined by receiving signals from the transmitter by multiple receivers. A locator data set is generated based on the comparison between two received signal characteristics determined for each receiver. The locator data set is compared with the calibration data set to determine the unknown position. In one embodiment, the signal comparisons are the differences between electric and magnetic field phase. Further embodiments utilize signal amplitude differences. A reciprocal method utilizing a single receiver and multiple transmitter locations is disclosed. A further method is disclosed for determining position by utilizing signals available from existing installed wiring such as power wiring.

Claims

1. A system for determining a position of an object, said system comprising:

a transmitter located with said object, said transmitter producing a beacon signal;

a plurality of receivers for receiving said beacon signal;

each of said receivers of said plurality of receivers having a respective known receiver position;

each of said receivers of said plurality of receivers comprising;

means for receiving a first signal characteristic of said beacon signal;

means for receiving a second signal characteristic of said beacon signal; and

a comparison unit for comparing said first signal characteristic and said second signal characteristic to generate a first comparison result;

said system for determining a position further comprising;

a database comprising calibration data, said calibration data representing a plurality of positions associated with respective predicted comparison results; and

a control processor,

said control processor finding among said predicted comparison results of said calibration data a minimal error point, said minimal error point being a predicted comparison result of said respective predicted comparison results matching most closely said first comparison result, said position of said object being determined based on said position associated with said minimal error point.

2. The system as in claim 1, wherein

said first signal characteristic of said beacon signal is an electric field characteristic, and said means for receiving said first signal characteristic is responsive to the phase of said electric field characteristic, and

said second signal characteristic of said beacon signal is a magnetic field characteristic, and said means for receiving said second signal characteristic is responsive to the phase of said magnetic field characteristic.

3. The system as in claim 2, wherein said first comparison result is the difference between said phase of said electric field characteristic and said phase of said magnetic field characteristic.

4. The system as in claim 1, wherein

said first signal characteristic of said beacon signal is an electric field characteristic, and

said means for receiving said first signal characteristic is responsive to the magnitude of said electric field characteristic, and

said second signal characteristic of said beacon signal is a magnetic field characteristic, and

said means for receiving said second signal characteristic is responsive to the magnitude of said magnetic field characteristic.

5. The system as in claim 1, wherein said first signal characteristic and said second signal characteristic comprise near field signal characteristics.

6. The system as in claim 1, further including a lanyard attached to said transmitter for carrying said transmitter wherein at least one antenna for transmitting said beacon signal is embedded in said lanyard.

7. The system as in claim 6, wherein said at least one antenna is a single element whip antenna.

8. The system as in claim 6, wherein said at least one antenna is a “

V”

dipole.

9. The system as in claim 6, wherein said at least one antenna is a loop antenna.

10. The system as in claim 6, wherein said at least one antenna is a high reactance antenna including reactive loading.

11. A system for determining a position of an object, said system comprising:

a transmitting means located with said object, said transmitting means producing a beacon signal;

a receiving means for receiving said beacon signal at a plurality of fixed locations;

said receiving means further comprising;

a first receiver for receiving a first signal characteristic of said beacon signal;

a second receiver for receiving a second signal characteristic of said beacon signal; and

a first comparison means for comparing said first signal characteristic and said second signal characteristic to generate a signal comparison result;

said system further comprising;

a database comprising a calibration data set, said calibration data set representing a plurality of positions associated with respective predicted comparison results;

a control processor,

said control processor finding among said predicted comparison results of said calibration data set a minimal error point, said minimal error point being a predicted comparison result of said respective predicted comparison results matching most closely said signal comparison result, said position of said object being determined based on said position associated with said minimal error point.

12. A method for determining an unknown position of a beacon transmitter comprising:

1) generating a plurality of calibration data sets, each calibration data set of said plurality of calibration data sets generated by;

a) transmitting a calibration transmission from a known transmitter position corresponding to each said calibration data set; and

b) receiving said calibration transmission at a plurality of known receiver positions, each said calibration data set comprising a plurality of comparison values comparing two received signal characteristics of said calibration transmission at each receiver position of said plurality of known receiver positions;

2) generating a positioning data set, said positioning data set generated by;

a) transmitting a positioning transmission from said beacon transmitter at said unknown position; and

b) receiving said positioning transmission at said plurality of known receiver positions, said positioning data set comprising a plurality of comparison values comparing two received signal characteristics of said positioning transmission at each receiver position of said plurality of known receiver positions; and

3) determining said unknown position of said beacon transmitter based on a position corresponding to a calibration data set of said plurality of calibration data sets most closely matching said positioning data set.

13. The method of claim 12, wherein said two received signal characteristics of said positioning transmission are near field signal characteristics.

14. The method of claim 12, wherein said two received signal characteristics of said positioning transmission include measurements of an E field phase and an H field phase.

15. The method according to claim 12, wherein matching said position data set includes the step of minimizing an error criterion between said position data set and said calibration data set.

16. The method according to claim 12, further including generating a plurality of predicted data sets based on said plurality of calibration data sets;

wherein determining said unknown position further includes refining said unknown position based on a position corresponding to a predicted data set most closely matching said positioning data set.

17. The method according to claim 12, wherein the unknown position is further refined by interpolation based on said plurality of calibration data sets and said positioning data set.

18. The method of claim 12, wherein said plurality of calibration data sets and said positioning data set are stored as vectors;

wherein said step of determining said unknown position includes determining a magnitude of a vector difference between said positioning data set and at least one data set of said plurality of calibration data sets.

19. The method of claim 18, wherein the value of at least one position in said calibration set of measurements is determined by a method based on Laplace'"'"'s equation:

∇

²φ

=∂

²φ

/∂

x²+∂

²φ

/∂

y²=0.

20. The method of claim 12, wherein said two received signal characteristics of said positioning transmission for each said transmission from include an E field magnitude and an H field magnitude.

21. The method of claim 12, further including at least a portion of pre-existing wiring within a building, wherein said receiver is coupled to said pre-existing wiring.

22. The method of claim 21, wherein said preexisting wiring includes AC power wiring and said receiver is coupled to said AC power wiring.

23. The method of claim 12, further including at least a portion of pre-existing wiring within a building, wherein said transmitter is coupled to said pre-existing wiring.

24. The method of claim 12, wherein said step of transmitting a calibration transmission from a known transmitter position corresponding to each said calibration data set includes moving at least one calibration transmitter between at least two positions of said known positions.

25. The method of claim 12, wherein said step of receiving said plurality of calibration transmissions from said plurality of known receiver positions includes moving at least one receiver between at least two positions of said plurality of known receiver positions.

26. A method for determining an unknown position of a locator receiver comprising:

1) generating a plurality of calibration data sets, each calibration data set of said plurality of calibration data sets generated by;

a) transmitting a plurality of calibration transmissions from known transmitter positions; and

b) receiving said plurality of calibration transmissions at a known receiver position corresponding to each said calibration data set, each said calibration data set comprising a plurality of comparison values comparing two received signal characteristics of each said calibration transmission at each transmitter position of said plurality of known transmitter positions;

2) generating a positioning data set, said positioning data set generated by;

a) transmitting a plurality of positioning transmissions from said known transmitter positions; and

b) receiving said plurality of positioning transmissions said unknown position of said locator receiver, said positioning data set comprising a plurality of comparison values comparing two received signal characteristics of each said positioning transmission of said plurality of positioning transmissions; and

3) determining said unknown position of said locating receiver based on a position corresponding to a calibration data set of said plurality of calibration data sets most closely matching said positioning data set.

27. The method of claim 26, wherein said two received signal characteristics of each said positioning transmission of said plurality of positioning transmissions are near field signal characteristics.

28. The method of claim 26, wherein said two received signal characteristics of each said positioning transmission of said plurality of positioning transmissions include an E field phase and an H field phase.

29. The method of claim 26, wherein said two received signal characteristics of each said positioning transmission of said plurality of positioning transmissions include an E field magnitude and an H field magnitude.

30. The method of claim 26, further including at least a portion of pre-existing wiring within a building, wherein said receiver is coupled to said pre-existing wiring.

31. The method of claim 30, wherein said preexisting wiring includes AC power wiring and said receiver is coupled to said AC power wiring.

32. The method of claim 26, further including at least a portion of pre-existing wiring within a building, wherein said transmitter is coupled to said pre-existing wiring.

33. The method of claim 26, wherein said step of transmitting a plurality of calibration transmissions from known transmitter positions includes moving at least one transmitter between at least two positions of said plurality of known transmitter positions.

34. The method of claim 26, wherein said step of receiving said plurality of calibration transmissions from a first plurality of known receiver positions includes moving at least one receiver between at least two positions of said known receiver positions corresponding to each said calibration data set.