Near field electromagnetic positioning system and method

• US 20050046608A1
• Filed: 10/04/2004
• Published: 03/03/2005
• 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
• Granted Patent: US 7,298,314 B2
• Time in Patent Office: Days
• US Class Current: 342/127
• 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;

said receivers having known positions;

said receivers further comprising;

a first receiver for receiving a first signal;

a second receiver for receiving a second signal; and

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

said system further comprising;

a database comprising calibration data;

a control processor for collecting said first results from said plurality of receivers,

said control processor further for comparing said first results with said calibration data for generating a position measurement.

2. The system as in claim 1 wherein

Said first receiver is responsive to E field phase, and

Said second receiver is responsive to H field phase.

3. The system as in claim 2 wherein said first result is the difference between said E field phase and said H field phase.

4. The system as in claim 1 wherein

Said first receiver is responsive to E field magnitude

Said second receiver is responsive to H field magnitude.

5. The system as in claim 1 wherein said first receiver and said second receiver receive near field signals from said transmitter.

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

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

8. The system as in claim 6 wherein said antenna is a “

V”

dipole.

9. The system as in claim 6 wherein said antenna is a loop antenna.

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

11. A method for determining a position of an object, said method utilizing a transmitter located with said object, said method comprising:

transmitting from a plurality of known transmitter positions;

receiving at a plurality of first known receiver positions;

recording a comparison between two signal characteristics received at said plurality of first known receiver positions to generate a calibration set of measurements;

transmitting from said position located with said object;

receiving at a plurality of second known receiver positions, said second known receiver positions related to said first known receiver positions;

recording said comparison between two signal characteristics received at said second known receiver positions to generate a second set of measurements;

comparing said second set of measurements to said calibration set of measurements to determine said position of said object.

12. The method of claim 11 wherein said signal characteristics are near field signal characteristics.

13. The method of claim 11 wherein said signal characteristics include an E field and an H field;

wherein said comparison between two signal characteristics is the phase difference between said E field and said H field.

14. The method of claim 11 wherein said calibration set of measurements and said second set of measurements are stored as arrays, said arrays comprising vectors, each said vector comprising the set of data associated with one of said transmitter locations, wherein said step of comparing includes determining the magnitude of the vector difference between said second set of measurements and said calibration set of measurements.

15. The method of claim 14 wherein said vector differences are computed in parallel.

16. The method of claim 14 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.

17. The method of claim 11 wherein said signal characteristics include an E field magnitude and an H field magnitude and wherein said comparison between two signal characteristics is the difference between said E field magnitude and said H field magnitude.

18. The method of claim 11 further including at least a portion of pre-existing wiring within a building, wherein said receiver is coupled to said pre-existing wiring.

19. The method of claim 18 wherein said preexisting wiring includes AC power wiring and said receiver is coupled to said AC power wiring.

20. The method of claim 11 further including at least a portion of pre-existing wiring within a building, wherein said transmitter is coupled to said pre-existing wiring.

21. The method of claim 11 wherein said step of transmitting from a plurality of known transmitter positions includes moving at least one transmitter between at least two positions of said plurality of known transmitter positions.

22. The method of claim 11 wherein said step of receiving from a plurality of first known receiver positions includes moving at least one receiver between at least two positions of said plurality of first known receiver positions.

23. A method for determining a position of an object, said method utilizing a receiver located with said object, said method comprising:

transmitting from a plurality of known transmitter positions;

receiving at a plurality of first known receiver positions;

recording a comparison between two signal characteristics received at said plurality of first known receiver positions to generate a calibration set of measurements;

transmitting from a plurality of second known transmitter positions, said second known transmitter positions related to said first known transmitter positions;

receiving at said position located with said object;

recording said comparison between two signal characteristics received at said position located with said object, said characteristics resulting from signals transmitted from said second known transmitter positions, said recording to generate a second set of measurements;

comparing said second set of measurements to said calibration set of measurements to determine said position of said object.

24. The method of claim 23 wherein said signal characteristics are near field signal characteristics.

25. The method of claim 23 wherein said signal characteristics include an E field and an H field;

wherein said comparison between two signal characteristics is the phase difference between said E field and said H field.

26. The method of claim 23 wherein said calibration set of measurements and said second set of measurements are stored as arrays, said arrays comprising vectors, each said vector comprising the set of data associated with one of said transmitter locations, wherein said step of comparing includes determining the magnitude of the vector difference between said second set of measurements and said calibration set of measurements.

27. The method of claim 26 wherein said vector differences are computed in parallel.

28. The method of claim 26 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.

29. The method of claim 23 wherein said signal characteristics include an E field magnitude and an H field magnitude and wherein said differences are between said E field magnitude and said H field magnitude.

30. The method of claim 23 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 23 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 23 wherein said step of transmitting from a plurality of 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 23 wherein said step of receiving from a plurality of first known receiver positions includes moving at least one receiver between at least two positions of said plurality of first known receiver positions.

35. A method for calibrating an electromagnetic position determination system comprising:

transmitting from a plurality of known transmitter positions;

receiving at a plurality of known receiver positions;

recording a comparison between two signal characteristics received at said plurality of known receiver positions to generate a calibration set of measurements.

36. 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 portable receiving means, portable for moving said receiving means among multiple locations.

said receiving means further comprising;

a first receiver for receiving a first signal;

a second receiver for receiving a second signal; and

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

said system further comprising;

a database comprising calibration data;

a collection means to collect said signal comparison results from said receiving means at each of said multiple locations,

a second comparison means for comparing said signal comparison result with said calibration data for generating a position measurement.