Method and system for locating a geographical position using broadcast frequency modulation signals

• US 20090322603A1
• Filed: 06/30/2008
• Published: 12/31/2009
• Est. Priority Date: 06/30/2008
• Status: Active Grant

• Current Assignee: Right Weigh, Inc.
• Original Assignee: Right Weigh, Inc.
• Inventors: Liao, Henry H.
• Granted Patent: US 7,990,314 B2
• Time in Patent Office: Days
• US Class Current: 342/357.29
• CPC Class Codes: G01S 19/48 by combining or switching between position solutions derived from the satellite radio beacon positioning system and position solutions derived from a further system
• CPC Class Codes: G01S 5/021 Calibration, monitoring or correction G01S5/0252 takes precedence
• CPC Class Codes: G01S 5/10 Position of receiver fixed by co-ordinating a plurality of position lines defined by path-difference measurements , e.g. omega or decca systemsG01S5/12 takes precedence ; beacons and receivers cooperating therewith G01S1/306, G01S1/308

Abstract

A method and system for locating and positioning using broadcast frequency modulation (FM) signals, is provided. One implementation involves receiving FM stereo signals from three FM stations at one or more receivers, each stereo signal including a modulated 19 KHz FM pilot tone; and determining a geographical position at each receiver based on the phase difference of the demodulated pilot tones in the received FM signals.

Claims

1. A method of positioning, comprising:

one or more receivers receiving FM stereo signals from three FM stations, said stereo signal including a FM modulated 19 KHz pilot tone; and

determining a geographical position at each receiver based on the phase difference of the demodulated pilot tones in the received FM signals.

2. The method of claim 1 further including:

said receivers performing phase bias corrections for the demodulated pilot tones in the FM signals to obtain phase corrected pilot tones, and determining a geographical position at a receiver from the phase corrected pilot tones by performing Time Difference of Arrival (TDOA) hyperbolic triangulation.

3. The method of claim 2 further including:

one or more base station (BS) and/or reference station (RS), each computing pilot tone phase arrival differences based on synchronized pilot tones, and measuring the phase differences from unsynchronized received pilot tones, to determine multiple station to station unsynchronized pilot tone biases pairs, each base station (BS) and/or reference station (RS) comprising a FM stereo receiver, a transceiver and a processor.

4. The method of claim 2 wherein a receiver comprises a mobile unit (MU), the method further including the mobile unit receiving phase biases corrections from either base station or reference station, and measuring phase differences between the pilot tones, and wherein determining a geographical position at the mobile station based on the measured phase differences with received phase biases corrections.

5. The method of claim 4 wherein the mobile unit comprises a FM stereo receiver, a processor and a transceiver, configured for performing two way communications to transmit phase measurement pairs to base stations or reference stations for determining geographical position of each mobile unit.

6. The method of claim 3 further including:

providing a local area map divided into finite grid points with surveyed geographical positions for each grid point, each grid point corresponding to computed phase differences of the pilot tones pairs at that grid point.

7. The method of claim 6 further including determining geographical position of a mobile unit by, for each grid point, determining a difference between the computed pilot tone phase differences at the grid point and computed phase differences at the base station or reference station, to form position double differencing pairs corresponding to a Cartesian (x, y) grid point coordinate relative to a base station or reference station at origin of the Cartesian plane, whichever is proximate to said grid point, and storing the coordinates in a look-up table corresponding to said double differencing pairs for determining the geographical position of the mobile unit.

8. The method of claim 7 further including receiving measured phase difference pairs from the mobile unit, and forming measured double difference pairs based on the measured phase difference pairs the mobile unit and the measured phase differences pairs at the base station or reference station, and comparing said double differencing pairs with the computed double differencing pairs in the look-up table to determine nearest grid point position coordinate (x, y) relative to the base station or reference station at origin.

9. The method of claim 8 further comprising:

when radio station positions are not precisely known, performing pre-survey at finite grid points in horizontal and vertical coordinates surrounding the base station or reference station at origin of the Cartesian plane, obtaining double differencing pairs of measured pilot tone phase differences of finite grid points relative to the base station or reference station by subtracting the double difference pairs in consecutive grid point to obtain the triple grid differencing pairs for interpolation, and generating a position look-up table using non-uniform differences interpolation using the triple grid difference pairs.

10. The method of claim 9, with either known or unknown radio station positions, performing pre-survey at each finite grid point surrounding the base station or reference station to obtain triple grid difference pairs from said measured or computed double differencing pairs, averaging horizontal and vertical triple grid differencing pairs into triple grid difference parameters to form a 2 by 2 matrix, then with the measured double differencing pairs of mobile unit as two inputs, multiplying unknown Cartesian coordinate (x, y) of a mobile unit by said 2 by 2 matrix to form two simultaneous equations and solving to determine (x, y) coordinate of each mobile unit.

11. The method of claim 10 further including:

transmitting said pre-surveyed triple differencing 2×

2 matrix parameters from the base station or reference station to a mobile unit, wherein the mobile units performs position determination.

12. The method of claim 2 further including performing sequential and repetitive phase measurement of the pilot tone phases of three FM stations to determine relative phase differences in order to perform TDOA hyperbolic positioning.

13. The method of claim 2 further including performing dead reckoning for assisting a GPS receiver whenever GPS signals are insufficient, using latest GPS position fix as the reference position to continue step by step TDOA hyperbolic positioning using FM pilot tone signals.

14. The method of claim 13 wherein dead reckoning further includes:

obtaining TDOA pairs and rate of change pairs of pilot tone differences pairs measurement in consecutive steps, to form a measurement vector input in a Kalman computation of position and velocity vector.

15. The method of claim 13 wherein dead reckoning further includes:

obtaining double differencing of TDOA pairs, and rate of change of double differencing TDOA pairs in consecutive steps measurements, to form a measurement vector input in a Kalman computation of position and velocity vector.

16. The method of claim 1 wherein an FM receiver is integrated with a GPS receiver for performing complementary positioning for outdoor and indoor positioning.

17. The method of claim 1 wherein determining geographical position further includes using multiple of 19 KHz pilot tones derivative at 57 KHz pilot tone or other FM sub-carriers pilot tone for determining geographical position.

18. The method of claim 1 further including receiving more than three FM station signals and determining geographical position therefrom.

19. The method of claim 1 further including utilizing said geographical position technique for E-911 service to locate cell phone units indoor or outdoor.

20. The method of claim 1 further including utilizing said geographical position technique for cell phone or other communication devices for location based services.

21. The method of claim 1 further including utilizing said geographical position technique for asset tracking and personal tracking.

22. The method of claims 1 wherein the FM stations include low power FM transmitters providing sinusoidal or periodic pilot tone modulation.

23. The method of claim 1 further including receiving FM signals from four or more FM station signals and determining three-dimensional geographical position based on the received signals.

44. The method of using FM pilot tones phase differences of claim 1, wherein at least three broadcasted FM pilot tones detected phase differences changes between two time periods are used for motion detection of mobile unit and the object attached.

45. The mobile unit using the method of claim 44, wherein an FM stereo receiver receiving at least three FM demodulated pilot tones, and detecting the phase difference changes among pilot tones in consecutive time period are used to detect the motion of the MU and the object attached.

24. A system for positioning, comprising:

a base station including a communication module configured for receiving FM stereo signals from three or more FM stations, said stereo signal including a FM modulated 19 KHz pilot tone; and

a positioning module configured for determining a geographical position at the receiver based on the phase difference of the demodulated pilot tones in the received FM signals.

25. The system of claim 24 wherein the positioning module is further configured for performing phase bias corrections for the demodulated pilot tones in the FM signals to obtain phase corrected pilot tones, and determining a geographical position at a receiver from the phase corrected pilot tones by performing Time Difference of Arrival (TDOA) hyperbolic triangulation.

26. The system of claim 25 wherein the positioning module is further configured for computing pilot tone phase arrival differences based on synchronized pilot tones, and measuring the phase differences from unsynchronized received pilot tones, to determine multiple station to station unsynchronized pilot tone biases pairs.

27. The system of claim 26 further including a local area map divided into finite grid points with surveyed geographical positions for each grid point, each grid point corresponding to computed phase differences of the pilot tones pairs at that grid point.

28. The system of claim 27 wherein the positioning module is further configured to determine geographical position of a mobile unit by, for each grid point, determining a difference between the computed pilot tone phase differences at the grid point and computed phase differences at the base station, to form position double differencing pairs corresponding to a Cartesian (x, y) grid point coordinate relative to a base station at origin of the Cartesian plane, and storing the coordinates in a look-up table corresponding to said double differencing pairs for determining the geographical position of the mobile unit.

29. The system of claim 28 wherein the positioning module is configured for obtaining measured phase difference pairs from the mobile unit, and forming measured double difference pairs based on the measured phase difference pairs the mobile unit and the measured phase differences pairs at the base station, and comparing said double differencing pairs with the computed double differencing pairs in the look-up table to determine nearest grid point position coordinate (x, y) relative to the base station at origin.

30. The system of claim 29 wherein:

when radio station positions are not precisely known, the positioning module utilizing a pre-survey map at finite grid points in horizontal and vertical coordinates surrounding the base station at origin of the Cartesian plane, and obtaining double differencing pairs of measured pilot tone phase differences of finite grid points relative to the base station by subtracting the double difference pairs in consecutive grid point to obtain the triple grid differencing pairs for interpolation, and generating a position look-up table using non-uniform differences interpolation using the triple grid difference pairs.

31. The system of claim 30, with either known or unknown radio station positions, the positioning module using a pre-survey at each finite grid point surrounding the base station to obtain triple grid difference pairs from said measured or computed double differencing pairs, averaging horizontal and vertical triple grid differencing pairs into triple grid difference parameters to form a 2 by 2 matrix, then with the measured double differencing pairs of mobile units as two inputs, multiplying unknown Cartesian coordinate (x, y) of a mobile unit by said 2 by 2 matrix to form two simultaneous equations and solving to determine (x, y) coordinate of each mobile unit relative to base station at origin.

32. The system of claim 31 wherein the communication module is further configured for transmitting said pre-surveyed triple differencing 2×

2 matrix parameters from the base station to a mobile unit, wherein the mobile unit performs position determination.

33. The system of claim 25 wherein the positioning module is further configured for performing sequential and repetitive phase measurement of the pilot tone phases of three FM stations to determine relative phase differences in order to perform TDOA hyperbolic positioning.

34. The base station of claim 24 wherein the base station functions as a reference station.

35. The system of claim 24, wherein a reference station comprises a fixed cell phone tower linking to a cellular base station and the system further includes a cellular mobile unit, wherein position determination can be performed either at the cellular base station or at the cellular mobile unit.

36. The system of claim 24, wherein the base station comprises one or more low power FM transmitters, and implementing sinusoidal or periodical pilot tone FM modulation.

37. A mobile unit for positioning, comprising:

a communication module configured for receiving FM stereo signals from three or more FM stations, said stereo signal including a FM modulated 19 KHz pilot tone, the communication module further configured for receiving phase bias corrections from a base station or reference station; and

a positioning module configured for measuring phase differences between the pilot tones, and determining a geographical position based on the measured phase differences with the received phase bias corrections.

38. The mobile unit of claim 37 wherein the communication module comprises a transceiver configured for performing two way communications to transmit phase measurement pairs to a base station or reference station for determining geographical position of the mobile unit.

39. The mobile unit of claim 37 wherein the positioning module is further configured for performing sequential and repetitive phase measurement of the pilot tone phases of three FM stations to determine relative phase differences in order to perform TDOA hyperbolic positioning.

40. The mobile unit of claim 37 wherein the positioning module is further configured for performing dead reckoning for assisting a GPS receiver whenever GPS signals are insufficient, using latest GPS position fix as the reference position to continue step by step TDOA hyperbolic positioning using FM pilot tone signals.

41. The mobile unit of claim 40 wherein the positioning module is further configured for dead reckoning by obtaining TDOA pairs and rate of change pairs of pilot tone differences pairs measurement in consecutive steps, to form a measurement vector input in a Kalman computation of position and velocity vector.

42. The mobile unit of claim 40 wherein the positioning module is further configured for dead reckoning by obtaining double differencing of TDOA pairs, and rate of change of double differencing TDOA pairs in consecutive steps measurements, to form a measurement vector input in a Kalman computation of position and velocity vector.

43. The mobile unit of claim 40 wherein the communication module comprises an FM receiver is integrated with a GPS receiver for performing complementary positioning for outdoor and indoor positioning.