Navigation and positioning system and method using uncoordinated beacon signals

• US 5,499,032 A
• Filed: 12/15/1993
• Issued: 03/12/1996
• Est. Priority Date: 12/22/1992
• Status: Expired due to Term

• Current Assignee: Terrapin Corporation
• Original Assignee: Terrapin Corporation
• Inventors: Kelley, David C., Greenbaum, Louis A., Cisneros, Joseph
• Primary Examiner(s): Blum, Theodore M.
• Application Number:
  US08/168,851
• Time in Patent Office: 818 Days
• Field of Search: 342/363, 342/357, 342/394, 342/442, 342/463, 342/457, 364/449, 455/12.1
• US Class Current: 342/463
• CPC Class Codes: G01S 5/0009 Transmission of position information to remote stations involving assistance data G01S5/0236
• CPC Class Codes: G01S 5/0063 of measured values, i.e. measurement on base station and position calculation on mobile
• CPC Class Codes: G01S 5/009 Transmission of differential positioning data to mobile
• 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
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location
• CPC Class Codes: H04B 7/1855 using a telephonic control signal, e.g. propagation delay variation, Doppler frequency variation, power variation, beam identification

Abstract

A positioning system uses a multiplicity of commercial broadcast stereo FM radio signal transmitters, at known fixed locations, each of which transmits a beacon signal having a phase that is un-synchronized with the phases of the beacon signals of the other transmitters. All the beacon signals have a frequency approximately equal to a 19 KHz. A fixed position observer unit, positioned at a known location, receives the beacon signals from all the transmitters in the vicinity, determines their relative phases, and broadcasts data representing these relative phases. Mobile units, at unknown locations, receive these broadcast values, as well as beacon signals from at least three radio transmitters. Each mobile unit includes phase detection circuitry that detects the phases of the beacon signals at the mobile receiver'"'"'s current position. This is accomplished using a single radio signal receiver. A digital phase-locked loop, coupled to the radio signal receiver, generates a phase error signal for each beacon signal. The phase error signals are then used to compute a distinct phase value for each beacon signal. In the preferred embodiment, each mobile receiver includes a computer for computing its location based on the broadcast relative phase values and the detected phases. In yet another embodiment a common timing signal is provided to the fixed observer unit and to the mobile units in order to establish a common time basis throughout the positioning system, thereby facilitating determination of an initial position for each mobile unit.

Claims

1. In a positioning system that makes use of a multiplicity of transmitters, at known fixed locations, each of which transmits a beacon signal having a phase that is un-synchronized with the phases of the beacon signals of the other transmitters;

each of said beacon signals having a frequency that is approximately equal to a predetermined target frequency;

the combination comprising;

a first receiver, at a known location relative to the locations of said multiplicity of transmitters, which (A) receives said beacon signals, (B) determines the relative phases of said beacon signals, and (C) broadcasts data representing said relative phases;

a second receiver, at an unknown location, which receives said broadcast data from said first receiver and at least three of said beacon signals, said second receiver including phase detection circuitry for detecting the phases of said beacon signals at the location of said second receiver, and computation means for computing the location of said second receiver based on said broadcast values and said detected phases; and

initialization means for providing a common timing signal to said first and second receivers in order to establish a common time basis therebetween, said initialization means including means for determining an initial estimate of said unknown location using said common time basis.

2. The positioning system of claim 1, said initialization means including a reference transmitter for broadcasting said common timing signal;

said first receiver including first means for receiving said common timing signal;

said second receiver including second means for receiving said common timing signal.

3. The positioning system of claim 2, said first receiver including a first reference clock and means for identifying a first receipt time, registered by said first reference clock, corresponding to receipt of said common timing signal by said first receiver;

said second receiver including a second reference clock and means for identifying a second receipt time, registered by said second reference clock, at which said common timing signal is received by said second receiver wherein said first and second reference clocks are un-synchronized.

4. The positioning system of claim 3, said first receiver including means for communicating said first time to said second receiver;

said initialization means including;

means for determining a time difference between said first and second receipt times, and

means for calculating said estimate of said unknown location at least partially on the basis of said time difference.

5. In a positioning system that makes use of a multiplicity of transmitters, at known fixed locations, each of which transmits a beacon signal having a phase that is un-synchronized with the phases of the beacon signals of the other transmitters;

each of said beacon signals having a frequency that is approximately equal to a predetermined target frequency;

the combination comprising;

a first receiver, at a known location relative to the locations of said multiplicity of transmitters, which (A) receives said beacon signals, (B) determines the relative phases of said beacon signals, and (C) generates a set of phase data representing said relative phases;

a second receiver, at an unknown location, which receives at least three of said beacon signals, said second receiver including phase detection circuitry for detecting the phases of said beacon signals at the location of said second receiver;

computation means, coupled to said second receiver for receiving from said second receiver values corresponding to said detected beacon signal phases, coupled to said first receiver for receiving said broadcast phase data, and including means for computing the location of said second receiver based on said broadcast phase values and said detected beacon signal phases; and

initialization means for providing a common timing signal to said first and second receivers in order to establish a common time basis therebetween, said initialization means including means for determining an initial estimate of said unknown location using said common time basis.

6. The positioning system of claim 5, said initialization means including a reference transmitter for broadcasting said common timing signal;

said first receiver including first means for receiving said common timing signal;

said second receiver including second means for receiving said common timing signal.

7. The positioning system of claim 6, said first receiver including a first reference clock and means for identifying a first receipt time, registered by said first reference clock, corresponding to receipt of said common timing signal by said first receiver;

said second receiver including a second reference clock and means for identifying a second receipt time, registered by said second reference clock, at which said common timing signal is received by said second receiver wherein said first and second reference clocks are un-synchronized.

8. The positioning system of claim 7, said first receiver including means for communicating said first time to said second receiver;

said initialization means including;

means for determining a time difference between said first and second receipt times, and

means for calculating said estimate of said unknown location at least partially on the basis of said time difference.

9. In a positioning system that makes use of a multiplicity of transmitters, at known fixed locations, each of which transmits a beacon signal having a phase that is un-synchronized with the phases of the beacon signals of the other transmitters;

each of said beacon signals having a frequency that is approximately equal to a predetermined target frequency;

the combination comprising;

a first receiver, at a known location relative to the locations of said multiplicity of transmitters, which (A) receives said beacon signals, (B) determines the frequency and relative phases of said beacon signals, and (C) which broadcasts values corresponding to said frequencies and relative phases;

a second receiver, at an unknown location, which receives said broadcast values from said first receiver and at least four of said beacon signals, said second receiver including phase detection circuitry for detecting the phases of said beacon signals at the location of said second receiver, and computation means for computing the location of said second receiver based on said broadcast values and said detected phases; and

initialization means for providing a common timing signal to said first and second receivers in order to establish a common time basis therebetween, said initialization means including means for determining an initial estimate of said unknown location using said common time basis.

10. A method of determining a mobile unit'"'"'s position with respect to the positions of a multiplicity of transmitters that are positioned at known fixed locations, wherein each transmitter transmits a beacon signal having a phase that is un-synchronized with the phases of the beacon signals of=the other transmitters;

each of said beacon signals having a frequency which is approximately equal to a predetermined target frequency;

the steps of the method comprising;

at a known location relative to the locations of said multiplicity of transmitters, receiving said beacon signals, determining the relative phases of said beacon signals, and broadcasting phase data representing said relative phases;

at a mobile unit'"'"'s location, receiving said broadcast phase data and at least three of said beacon signals, detecting the phases of said beacon signals at the location of said mobile unit, and computing the location of said mobile unit based on said broadcast phase data and said detected phases; and

providing a common timing signal to said first and second receivers, said common timing signal being used in said location computing step to provide an initial time value estimate for a time parameter used by said location computing step.

11. The method of claim 10, further including the steps of:

broadcasting said common timing signal;

at said known location, receiving said common timing signal and identifying a first time of receipt of said common timing signal at said known location in accordance with a time registered by a first reference clock at said known location; and

at said unknown location, receiving said common timing signal and identifying a second time of receipt of said common timing signal at said unknown location in accordance with a time registered by a second reference clock at said unknown location wherein said first and second reference clocks are un-synchronized.

12. The method of claim 11, further including the steps of:

determining a time difference between said first and second receipt times, and

calculating said estimate of said unknown location at least partially on the basis of said time difference.

13. A method of determining a mobile unit'"'"'s position with respect to the positions of a multiplicity of transmitters that are positioned at known fixed locations, wherein each transmitter transmits a beacon signal having a phase that is un-synchronized with the phases of the beacon signals of the other transmitters;

each of said beacon signals having a frequency which is approximately equal to a predetermined target frequency;

the steps of the method comprising;

at a known location relative to the locations of said multiplicity of transmitters, receiving said beacon signals, determining the relative phases of said beacon signals, and generating phase data representing said relative phases;

at a mobile unit'"'"'s location, receiving said at least three of said beacon signals and detecting the phases of said beacon signals at the location of said mobile unit;

receiving said generated phase data, and computing the location of said mobile unit based on said phase data and said detected phases; and

providing a common timing signal to said first and second receivers, said common timing signal being used in said location computing step to provide an initial time value estimate for a time parameter used by said location computing step.