Methods and apparatus for high resolution positioning

• US 7,292,189 B2
• Filed: 09/08/2005
• Issued: 11/06/2007
• Est. Priority Date: 09/10/2004
• Status: Expired due to Fees

• Current Assignee: Worcester Polytechnic Institute
• Original Assignee: Worcester Polytechnic Institute
• Inventors: Michalson, William R., Duckworth, R. James, Orr, John A., Cyganski, David
• Primary Examiner(s): Tarcza; Thomas H.
• Assistant Examiner(s): Mull; Fred H.
• Application Number:
  US11/223,079
• Publication Number:
  US 20060244661A1
• Time in Patent Office: 789 Days
• Field of Search: 342/387, 342/453, 342/463, 342/465, 455 412- 413
• US Class Current: 342/465
• CPC Class Codes: G01S 5/0218 Multipath in signal reception
• CPC Class Codes: G01S 5/06 Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements G01S5/12 takes precedence

Abstract

The invention relates to a method of signal analysis that determines the location of a transmitter and to devices that implement the method. The method includes receiving by at least three receivers, from a transmitter, a first continuous-time signal having a first channel. The first channel includes a first plurality of signal carriers having known relative initial phases and having known frequencies which are periodically spaced and which are orthogonal to one another within a first frequency range. The signal analysis method also includes determining the phase shifts of the carriers of the first channel resulting from the distance the carriers traveled in reaching the first receiver. Analysis of the phase shifts yields time difference of arrival information amongst the receivers, which is further processed to determine the location of the transmitter.

Claims

1. A method of signal analysis, comprising:

receiving, by at least three receivers, from a transmitter physically decoupled from at least one of the three receivers, a plurality of signal components corresponding to a first continuous-time signal having a first channel including a first plurality of carriers having known relative initial phases and having known frequencies which are orthogonal to one another within a first frequency range;

determining, for at least one of the plurality of signal components, the phase shifts of the carriers of the first channel resulting from the distance the carriers traveled in reaching the receivers; and

determining the location of the transmitter based on the determined carrier phase shifts.

2. The method of claim 1, wherein the frequencies of the carriers in the first channel are periodically spaced.

3. The method of claim 1, wherein the location determination includes determining the time difference of arrival of the signals at the receivers.

4. The method of claim 1, wherein the first continuous-time signal further comprises additional channels, the additional channels including a plurality of carriers having known relative initial phases and having known frequencies that are periodically spaced and orthogonal to one another within distinct frequency ranges.

5. The method of claim 4, comprising determining phase shifts of the plurality of carriers in the additional channels, and wherein the location is determined based on the determined phase shifts of at least two channels of the first continuous-time signal.

6. The method of claim 4, wherein the frequencies of the channels are selected to lie between frequency ranges restricted by the government for other uses.

7. The method of claim 1, wherein the carriers comprise unmodulated sine waves.

8. The method of claim 1, comprising identifying, based at least in part on the determined phase shifts, a most-direct path signal component arriving at one of the receivers by a most-direct path, and wherein the location determination is based upon analysis of the most-direct path signal component.

9. The method of claim 1, wherein the location determination includes determining, based at least in part on evaluating a plurality of potential location solutions, a most-direct path signal component arriving at one of the receivers by a most-direct path.

10. The method of claim 1, further comprising synchronizing the at least three receivers.

11. The method of claim 1, comprising determining a time delay by applying an algorithm from a class of a modern spectral analysis algorithms to the determined phase shifts.

12. The method of claim 11, wherein the algorithm is a state space algorithm.

13. The method of claim 12, wherein the state space algorithm includes forming a matrix including the magnitudes and phases of the first plurality of carriers and performing a plurality of matrix decompositions upon the matrix.

14. The method of claim 1, comprising decoding the first-continuous time signal using a predetermined decoding key corresponding to a coding scheme applied by the transmitter.

15. The method of claim 14, wherein the decoding key comprises a pseudo-random noise pattern.

16. The method of claim 1, comprising transmitting the determined transmitter location to the transmitter.

17. A transmitter location system comprising:

a first receiver having a first location for receiving a plurality of signal components to a continuous-time signal, sent by a transmitter, the signal having at least one channel, the channel comprising a plurality of carriers having known relative initial phases and having frequencies which are orthogonal to other frequencies within that channel;

second and third receivers having a second and third locations known relative to the first location for receiving the continuous-time signals; and

a processor configured to;

for each receiver, determine the differences in phase shifts in the carriers of at least one of the channels of the signal components;

for each receiver, selecting one of the plurality of signal component as a most-direct path signal component based on the determined phase shifts; and

determine the location of the transmitter based on the determined phase shifts and the relative receiver locations.

18. The transmitter location system of claim 17, wherein the frequencies of the carriers in the at least one channel are spaced periodically over a distinct frequency range.

19. The transmitter location system of claim 17, wherein the transmitter broadcasts the channels at frequencies selected to be between frequency ranges restricted by the government for other uses.

20. The transmitter location system of claim 17, wherein the carrier frequencies comprise unmodulated sine waves.

21. The transmitter location system of claim 17, wherein the processor determines a time delay by applying an algorithm from a class of a modern spectral analysis algorithms to the determined phase shifts.

22. The transmitter location system of claim 21, wherein the modern spectral analysis algorithm applied by the processor is a state space algorithm.

23. The transmitter location system of claim 22, wherein the processor is configured to form a matrix including the magnitudes and phases of the plurality of carriers of one of the analyzed channels and to perform a plurality of matrix decompositions upon the matrix using the state space algorithm.

24. The transmitter location system of claim 22, wherein the processor is configured to form a matrix including the magnitudes and phases of the plurality of carriers of at least two of the analyzed channels and to perform a plurality of matrix decompositions upon the matrix using the state space algorithm.

25. The transmitter location system of claim 17, wherein the processor is further configured to decode at least one of the continuous-time signals using a known decoding key corresponding to a coding scheme applied by the transmitter.

26. The transmitter location system of claim 25, wherein the coding scheme comprises modulating the channel with pseudo random noise.

27. The transmitter location system of 17, including a locatable transmitter comprising:

a signal store for storing a signal channel, the channel comprising a plurality of carriers having known relative initial phases and having frequencies which are orthogonal to other frequencies within that channel and which are spaced periodically over a distinct frequency range; and

an amplifier in communication with the store for transmitting a signal.

28. The transmitter location system of claim 27, wherein the signal store stores a plurality of signal channels.

29. The transmitter location system of claim 27, wherein the locatable transmitter further comprises an oscillator in communication with the signal store and an amplifier for modulating the stored signal channel to a base band frequency.

30. The transmitter location system of claim 27, wherein the oscillator is configured to oscillate at multiple frequencies thereby providing for frequency hopping.

31. A locatable transmitter comprising:

a signal store for storing a signal channel, the channel comprising a plurality of carriers having known relative initial phases and having frequencies which are orthogonal to other frequencies within that channel;

a first oscillator in communication with the signal store for modulating the signal channel at a first base band frequency to generate a first transmission channel;

a second oscillator in communication with the signal store for modulating the signal channel at a second base band frequency to generate a second transmission channel; and

an amplifier in communication with the first and second oscillators for broadcasting a location signal including the linear combination of the first and second transmission channels.

32. The locatable transmitter of claim 31, wherein the frequencies of the carriers in the signal channel are spaced periodically over a distinct frequency range.

33. The locatable transmitter of claim 31, further including an encoder in communication with the amplifier for encoding the broadcast signal with a predetermined code prior to transmission of the location signal.

34. The locatable transmitter of claim 33, wherein the predetermined code comprises a pseudo-random noise pattern.

35. The locatable transmitter of claim 31, wherein the frequencies of the first and second oscillators are variable and are controlled to provide for frequency hopping.

36. A communications device comprising:

a base band signal generator for generating a base band signal including a first plurality of carriers having known relative initial phases and having known frequencies which are orthogonal to one another within a first frequency range;

an oscillation module in communication with the base band signal generator for modulating the base band signal to generate a set of transmission channels;

a data modulation controller configured to select a subset of the transmission channels as data transmission channels; and

a data modulator for modulating data into the data transmission channels, wherein the unselected channels can be analyzed by a receiver to determine the location of the communications device.

37. The communications device of claim 36, wherein the frequencies of the carriers are periodically spaced with the first frequency range.

38. The communications device of claim 36, wherein the data modulator is configured to modulate each of the selected channels independently with data.

39. The communications device of claim 36, wherein the data modulation controller is configured to dynamically select a number of transmission channels as data transmission channels, based at least in part on instructions received from a receiver.

40. The communications device of claim 36, wherein the data modulation controller is configured to dynamically select a number of transmission channels as data transmission channels, based at least on the environment that the communications device is broadcasting in.

41. The communications device of claim 36, wherein the data modulator is configured to modulate a data transmission channel with at least one of user vital sign data and environmental data.

42. The communications device of claim 36, wherein the data modulator is configured to modulate a data transmission channel with synchronization data.

43. A communications device comprising:

a demodulation module for demodulating a plurality of signal channels of a plurality of received signal components, each channel including a plurality of carriers having known relative initial phases and having known frequencies which are orthogonal to one another within a distinct frequency range;

a signal analysis module configured to

determine a most-direct path signal component from the plurality of received signal components sent by a transmitter to the communications device;

determine the distance between the communications device and the transmitter; and

recover data modulated into at least one of the received channels;

provide requested data bandwidth instructions to the receiver.

44. The communications device of claim 43, wherein the frequencies of the carriers within each channel are periodically spaced within their corresponding distinct frequency ranges.

45. The method of claim 43, wherein the signal analysis module is configured to determine a location of the transmitter based on the determined distance.

46. The method of claim 45, wherein the signal analysis module is configured to transmit the determined transmitter location to the transmitter.

47. A method of providing variable bandwidth data communication comprising:

generating a base band channel including a plurality of carriers having known relative initial phases and having known frequencies which are orthogonal to one another within a frequency range;

modulating the base band channel to a plurality of base frequencies to generate a set of transmission channels;

selecting a subset of the transmission channels for encoding data to form data transmission channels;

combining and broadcasting the selected and unselected transmission channels, wherein the unselected transmission channels can be analyzed by a receiver to determine the location of the source of the broadcast.

48. The method of claim 47, wherein the frequencies of the base band channel are periodically spaced within the frequency range.

49. The method of claim 47, wherein each of the selected channels is independently modulated with data.

50. The method of claim 47, further comprising dynamically determining the number of transmission channels to be selected as data transmission channels, based at least in part on instructions received from the receiver.

51. The method of claim 47, further comprising dynamically determining the number of transmission channels to be selected as data transmission channels, based at least on the broadcast environment.

52. The method of claim 47, wherein the data includes at least one of user vital signs and environmental data.

53. The method of claim 47, wherein the data includes synchronization data.