Instantaneous radiopositioning using signals of opportunity
First Claim
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1. A method of instantaneously determining an unknown position using radio signals from a plurality of transmitters having widely distributed and known positions, the signals from different transmitters having respectively different radio frequencies, said frequencies being widely distributed, comprising:
- (a) measuring the phases of said radio signals having said different radio frequencies arriving concurrently at said unknown position, to obtain a first set of phase-measurement data;
(b) measuring the phases of said radio signals having said different radio frequencies arriving concurrently at a known reference position, almost simultaneously with their arrival at said unknown position, to obtain a second set of phase-measurement data; and
(c) combining said first and second data sets to determine said unknown position.
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Abstract
Instantaneous radio positioning method and system. Signals from a plurality of spatially distributed transmitters are received at a known reference position and at an unknown position to be determined. A composite of the radio signals, simultaneously including a component signed from each of the transmitters, is digitized and then processed to measure phases that is then digitized. Ambiguity is resolved by finding the location in parameter space of the maximum of an ambiguity function related to sets of phase-measurement data. Position is determined at a point in time without keeping track of phase history.
142 Citations
29 Claims
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1. A method of instantaneously determining an unknown position using radio signals from a plurality of transmitters having widely distributed and known positions, the signals from different transmitters having respectively different radio frequencies, said frequencies being widely distributed, comprising:
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(a) measuring the phases of said radio signals having said different radio frequencies arriving concurrently at said unknown position, to obtain a first set of phase-measurement data;
(b) measuring the phases of said radio signals having said different radio frequencies arriving concurrently at a known reference position, almost simultaneously with their arrival at said unknown position, to obtain a second set of phase-measurement data; and
(c) combining said first and second data sets to determine said unknown position. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 26, 27)
said radio signals arrive at said unknown position via ground-wave propagation from said plurality of transmitters.
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3. The invention of claim 1, wherein:
said transmitters operate independently.
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4. The invention of claim 1, wherein:
said radio signals are transmitted with random phases.
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5. The invention of claim 1, wherein:
said first set of phase measurement data refers to a first instant of concurrent-signal-arrival at the unknown position, said second set of phase measurement data refers to a second instant of concurrent-signal-arrival time at the reference position, and the departure from simultaneity of said first and second instants is determined simultaneously with said determination of said unknown position.
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6. The invention of claim 5, further comprising:
resolving position ambiguity related to the integer-cycle ambiguity inherent in said phase measurements.
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7. The method of claim 5 further comprising forming an ambiguity function of the sets of phase-measurement data in a spatial parameter space and finding the location of the maximum of the ambiguity function.
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8. The method of claim 7 wherein the ambiguity function is a sum, over all of the transmitters, of a periodic function of the phase-measurement data.
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9. The method of claim 8 wherein the periodic function has a period of a cycle of phase.
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10. The method of claim 9 wherein the periodic function is a cosine.
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11. The method of claim 8 wherein the periodic function is (½
- +½
cosine θ
)n where θ
is a phase and n is greater than 1.
- +½
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12. The method of claim 1 wherein a composite of said radio signals, simultaneously including a component signal from each of the transmitters, is digitized and then processed to measure said phases.
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13. The method of claim 1 further comprising providing a repeater system allowing the phases of the signals to be measured away from where the signals are received.
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14. The method of claim 7 wherein the ambiguity function is
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( x ^ , y ^ , t ^ ) = ∑ j = 1 J W r j cos ( θ j - θ ^ j ( x ^ , y ^ , t ^ ) ) ·
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26. The method of claim 5, further comprising determining said unknown position by:
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evaluating a function of said first and second sets of phase measurement data and of a trial value of said unknown position;
searching a range of said trial values to find an extreme value of said function; and
determining said unknown position from the trial value for which said extreme value is found.
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27. The invention of claim 26 further comprising downweighting discordant members of said first and second sets of phase measurement data in the evaluation of said function.
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15. Radiopositioning system for instantaneously determining an unknown position comprising:
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a plurality of spatially distributed transmitters at known locations, the transmitters. transmitting signals, wherein the signals from different transmitters have respectively different radio frequencies, the different radio frequencies being widely distributed;
a first receiver located at the unknown position adapted to receive said signals having said different radio frequencies and to determine their phases to generate a first set of phase-measurement data;
a second receiver located at a known reference position adapted to receive the same signals having said different radio frequencies and to determine their phases at the known reference position to generate a second set of phase-measurement data; and
computing apparatus operating on the first and second sets of phase-measurement data to determine the unknown position. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
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28. A method of instantaneously determining an unknown position, comprising:
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collecting a composite of radio signals arriving simultaneously at said position from a plurality of transmitters having widely distributed and known positions, the signals from different transmitters having respectively different radio frequencies, said frequencies being widely distributed;
forming a digital representation of said composite of said radio signals having said different radio frequencies;
processing said digital representation to derive a first data set representing phases of signals received from each of said plurality of transmitters; and
combining said first data set with a second data set representing phases of signals received at a known position from the same said plurality of transmitters, to determine said unknown position with respect to said known position. - View Dependent Claims (29)
computing a spectrum of said digital representation; and
finding peaks in said spectrum;
deriving said first set of phase data from said peaks.
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Specification
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Current AssigneeMassachusetts Institute of Technology
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Original AssigneeMassachusetts Institute of Technology
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InventorsHall, Timothy D., Counselman, III, Charles C.
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Primary Examiner(s)Issing, Gregory C.
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Application NumberUS09/765,313Publication NumberTime in Patent Office690 DaysField of Search342/357.14, 342/464, 342/463US Class Current342/464CPC Class CodesG01S 5/10 Position of receiver fixed ...
