Position fixing system utilizing plural commercial broadcast transmissions and having frequency correction

• US 4,054,880 A
• Filed: 01/19/1976
• Issued: 10/18/1977
• Est. Priority Date: 01/19/1976
• Status: Expired due to Term

• Current Assignee: E-Systems LLC
• Original Assignee: E-Systems LLC
• Inventors: Shearer, Harry D., Dalabakis, Eli J.
• Primary Examiner(s): Wilbur, Maynard R.
• Assistant Examiner(s): Berger, Richard E.
• Application Number:
  US05/650,006
• Time in Patent Office: 638 Days
• Field of Search: 343/112 D, 343/112 TC, 343/112 R, 235/150.27
• US Class Current: 342/464
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location

Abstract

A radio navigation, position locating and signaling arrangement employs three operative channels per vehicle for receiving three commercial radio transmissions. Each channel includes feedback circuitry for maintaining a constant phase relationship between a replica of the received broadcast carrier and a reference oscillation, both reduced in frequency. An accumulator in each channel records the number of pulses added and/or deleted from the reference pulse train to provide a measure of the radial distance travelled by a vehicle with respect to the corresponding fixed radio transmitters. Common central station equipment processes the reported vehicle accumulated coordinate pulse counts, and corrects such vehicle coordinate fixing information for frequency error in the non-cooperative commercial transmissions and in the vehicle mounted local reference oscillations.

Claims

1. In combination in displacement determing apparatus for determining displacement information utilizing the phase of a carrier wave, said displacement determining apparatus including means for selecting said carrier wave, divider means for reducing the frequency of said carrier wave, a reference oscillator, phase locked loop means connected to said divider means and said reference oscillator means, said phase locked loop means including phase comparator means, and pulse adding and deleting means for selectively adding pulses to and deleting pulses from the pulse wave supplied by said reference oscillator, accumulator means connected to said pulse adding and deleting means, the improvement comprising:

common station equipment for correcting the contents of said accumulator means for frequency variations in said carrier wave, said common station equipment correcting means comprising;

a. additional means for selecting said carrier wave,

b. a common station oscillator,

c. an up-down counter,

d. additional phase locked loop means connected to the ouputs of said common station oscillator and said additional carrier wave selecting means for changing the state of said up-down counter means in a direction which reflects any changes in frequency of the wave being monitored, and

e. means responsive to pulses in said accumulator means and the state of said up-down counter for algebraically combining the pulses of said up-down counter with the contents of said accumulator means to correct the contents of said accumulator means for variations in frequency of said selected carrier wave.

2. A combination as in claim 1 further comprising elapsed time means for providing a signal dependent upon the time elapsed since said accumulator means was last initialized multiplier means connected carried to said elapsed time means for multiplying said elapsed time signal with a constant dependent upon any frequency deviation of said reference oscillator means, and means for correcting the contents of said accumulator means comprising means for linearly combining the contents of said accumulator means and the output of said multiplier means.

3. A combination as in claim 1, wherein said phase locked loop means further comprises additional divider means connected intermediate said phase comparator means and said pulse adding and deleting means.

4. A combination as in claim 1, wherein said phase comparator means supplies an analog output voltage, first threshold means for signalling said pulse adding and deleting means to add a pulse into the pulse wave supplied by said reference oscillator, and second threshold means for signalling said adding and deleting means to delete a pulse from the pulse wave supplied by said reference oscillator.

5. A combination as in claim 1, wherein said carrier wave selecting means includes an additional phase locked loop.

6. A combination as in claim 1, wherein said carrier wave selecting means includes a bandpass filter.

7. A combination as in claim 1, further comprising first and second additional displacement determining apparatus substantially similar to said displacement determining apparatus, said common station means further comprising additional means for correcting the contents of said accumulator means of said first and second additional displacement determining apparatus.

8. A combination as in claim 1 wherein said common station equipment further comprises additional divider means for reducing the frequency of said selected carrier wave, and wherein said common station additional phase locked loop means includes additional phase comparator means, and additional pulse adding and deleting means for selectively adding pulses to and deleting pulses from the pulse wave supplied from said common station reference oscillator.

9. In combination in a radio position monitoring system for identifying the position of at least one vehicle employing phase measurements from a radiated transmission, said vehicle including counter means for measuring phase displacement relative to said transmission responsive to vehicle translation relative to said transmission, the improvement comprising:

common station equipment comprising;

a. means for receiving and storing the count state of said counter means for each vehicle,

b. means for receiving said transmission,

c. a reference oscillator,

d. divider means for reducing said received transmission and said reference oscillator to a like frequency,

e. a bidirectional error counter,

f. phase detector means responsive to phase displacement between the like frequency signals produced by said divider means for selectively advancing said bidirectional counter in an amount and direction dependent upon the phase displacement between said like frequency signals supplied by said divider means, and

g. linear combining means for algebraically combining the vehicle reported count state from said storage means therefor and the contents of said bidirectional counter.

10. A combination as in claim 9 further comprising elapsed time means for providing a signal dependent upon the time elapsed since said system was last initialized, multiplier means connected to said elapsed time means for multiplying said elapsed time signal with a constant reflecting the error rate for the contents of said vehicle counter means, said linear combining means including means for algebraically combining the vehicle reported count state from said storage means therefor with the ouput of said multiplier means.

11. In combination in common station means for correcting coordinate count vehicle positional information determined by vehicles disposed in a field subjected to plural radiated transmissions, there being i such vehicles and j such transmissions, where i and j are independent position integers, means for receiving each transmission, an oscillator, means connected to said oscillator and to said transmission receiving means for providing j apparent motion correction signals dependent upon frequency variations of said transmissions, storage means for storing i.j coordinate count values determined by the i vehicles, first iteratively operative linear summing means for algebraically combining said j apparent motion correction signals and said j coordinate count values supplied by said storage means therefor determined by any one vehicle, and second iteratively operative means effecting serial operation of said first iteratively operative linear summing means for each of the i vehicles.

12. In combination in displacement determining apparatus for determining displacement information utilizing the phase of a carrier wave, radiated over a field, said displacement determining apparatus comprising means for selecting said carrier wave, divider means for reducing the frequency of said carrier wave, a reference oscillator, phase locked loop means connected to said divider means and said reference oscillator means, said phase locked loop means including phase comparator means, pulse adding and deleting means for selectively adding pulses to and deleting pulses from the pulse wave supplied by said reference oscillator, and accumulator means connected to said pulse adding and deleting means, the improvement comprising:

common station equipment comprising;

a. means for storing the count state of said accumulator means, additional means for selecting said carrier wave,

b. means for determining frequency deviations of said carrier wave supplied by said additional carrier wave selecting means, and

c. coordinate correcting means for correcting the count contents of said accumulator means stored in said storage means thereof responsive to the carrier wave deviation signaled by said carrier frequency deviation detecting means.