METHODS AND APPARATUS FOR PRECISE POSITIONING OF LOCATIONS

• US 3,715,758 A
• Filed: 07/07/1970
• Issued: 02/06/1973
• Est. Priority Date: 07/10/1969
• Status: Expired due to Term

• Current Assignee: Friedhelm K. Sender
• Original Assignee: Friedhelm K. Sender
• Inventors: Sender, Friedhelm K.
• Primary Examiner(s): Feinberg, Samuel
• Assistant Examiner(s): Berger, Richard E.
• Application Number:
  US05/052,893
• Time in Patent Office: 945 Days
• Field of Search: 343/112,112D,15LS,105
• US Class Current: 342/463
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location

Abstract

A radio location system employing at least two fixedly installed transmitters operating on substantially continuous carrier frequencies and a fixedly installed reference transceiver suitably located to receive the carrier frequencies from each of the transmitters. A station receiver is located at the location that is to be precisely positioned which synthesizes the frequencies of the two transmitters and determines position by developing traveltime information to the receiver, these synthesized carrier frequencies being absolutely determined with respect to an atomic clock. A similar atomic clock in the reference transceiver similarly determines synthesized frequencies and their error with respect to the transmitted frequencies. These error corrections are converted to digital form and transmitted to the station receiver for correcting the developed traveltime information and hence developing precision positioning information.

Claims

1. A radio navigation system for determining the location of a station, comprising a first transmitter station fixedly disposed at a first location for generating a first preselected frequency;

a second transmitter station fixedly disposed at a second location for generating a second preselected frequency;

a reference transceiver fixedly disposed at a third different location for receiving said first and second frequencies, and including a precision frequency standard, said transceiver developing first and second error correction signals with respect to the signals of said frequency standard; and

a receiver located at the station for receiving said first and second frequencies and said error correction signals, and including a precision frequency standard operating at a known relation to said frequency standard of said reference transceiver, for determining the position of said receiver with respect to said first and second transmitter stations, said error correction signals correcting for operational deviations of said station receiver precision frequency standards from said first and second preselected frequencies.

2. The system described in claim 1, wherein said first and second frequencies occupy a single frequency channel.

3. The system described in claim 2, wherein said first and second frequencies are both sums of coherent frequencies.

4. The system described in claim 3, wherein said reference transceiver and station receiver precision frequency standards generate synchronized and equal output frequencies.

5. The system described in claim 4, wherein said reference transceiver and station receiver each include a divider chain having a plurality of stages responsive to the output frequency of the frequency standard associated therewith and each delivering a fraction of said output frequency within a time period within which the other of said stages do not deliver any of said output frequencies, and combining means responsive to said divider chain for combining delivered fractions of said associated frequency standard into a preselected frequency for phase comparison with said preselected freqUencies from said first and second transmitter stations.

6. The receiver station described in claim 5, wherein said combining means further generates a fixed frequency difference relative to said selected one of said partial frequencies generated by said first and second transmitter stations.

7. The system described in claim 6, wherein the respective initial frequency of the preceding stage in each of said divider chains is divided by a factor of two in each of the subsequent stages therein.

8. The system described in claim 1, wherein said reference transceiver and station receiver precision frequency standards comprise atomic clocks.

9. The system described in claim 1, wherein said station is a mobile receiver station.

10. A radio navigation system as set forth in claim 1, wherein said reference transceiver includes a synthesizer for internally generating a first reference signal at approximately said first preselected frequency and a second reference signal at approximately said second preselected frequency, and comparison means for selecting and comparing said synthesized reference signals with said preselected frequencies for creating said error correction signals;

and wherein said receiver station includes a synthesizer synchronized with said transceiver for internally generating a first signal at approximately said first preselected frequences and a second signal at approximately said second preselected frequency, and comparing means for selecting and comparing said signals synthesized in said station receiver with said preselected frequencies for determining position of said receiver, said error correction signals correcting for deviation said station receiver synthesizer fails to approximate said first and second frequencies.

11. A radio navigation system for determining the location of a station, comprising a first transmitter station fixedly disposed at a first location and generating a first identifiable signal of a preselected frequency, a second transmitter station fixedly disposed at a second location for generating a second identifiable signal of a preselected frequency, a reference transceiver fixedly disposed at a third different location for receiving said first and second identifiable signals and including a precision frequency standard, said transceiver developing first and second error correction signals of said preselected frequency with respect to the signal of said frequencies standard, and a receiver located at the station for receiving said first and second identifiable signals and said error correction signals, and including a precision frequency standard operating at a known relation to said frequency standard in said reference transceiver, for determining the position of said receiver with respect to said first and second transmitter stations, said error correction signals correcting for operational deviation of said station receiver precision frequency standard with respect to said preselected frequency.

12. A radio navigation system for determining the location of a mobile station, comprising a pair of transmitter stations at different fixed locations operating at respective carrier frequencies, a transceiver at a third fixed location, including a first precision frequency standard, and means for developing a digital error signal between said frequency standard and said received carrier frequencies, and a mobile receiver including a second precision frequency standard synchronized with said first frequency standard, and means for developing traveltime information from said received respective carrier frequencies and transmitting said traveltime information to said transmitter stations controlled by said second precision frequency standard, said means utilizing said digital error signal for improving said traveltime information.

13. The system described in claim 12, wherein said first and second precision frequency standards aRe essentially identical.

14. A radio navigation system for determining the location of a mobile station, comprising a pair of transmitter stations at different fixed locations operating at respective carrier frequencies, a transceiver at a third fixed location, including a first precision frequency standard, and means for developing an error signal between said frequency standard and said received carrier frequency, and a mobile receiver including a second precision frequency standard synchronized with said first frequency standard, means for developing traveltime information from said received respective carrier frequencies and transmitting said traveltime information to said transmitter station controlled by said second precision frequency standard, a unilateral low band width communication channel for transmitting said error signal from said transceiver to said mobile receiver, said means utilizing said error signal for improving said traveltime information.

15. A radio navigation receiver for determining the location of a station from received first and second carrier waves transmitted from first and second fixedly located transmitters and a third fixedly located transmitter including an atomic clock synchronously operating with an atomic clock at the radio navigation receiver and developing error correction data of said atomic clock with respect to said first and second carrier waves, said receiver comprising derivative frequency and phase means for receiving the error correction data from said third transmitter and adjusting the frequency and phase of a signal related to the atomic clock frequency of said station receiver to equal nearly exactly the carrier waves from the first and second transmitters, and frequency and phase comparison means for developing the apparent difference in phase between the received carrier waves from said first and second transmitters and said corrected frequency signal related to the atomic clock frequency of said station receiver.

16. A method of navigation, comprising generating a first preselected frequency at a first fixed location, generating a second preselected frequency functionally related to and synchronous with said first frequency at a second fixed location, generating at a third fixed location error signals resulting from error signals received from said preselected frequencies received at said third fixed location and indicative of the difference between said first and second preselected frequencies and synthesized signal frequencies derived from an atomic clock, generating at a station location to be determined third and fourth frequencies derived from an atomic clock synchronously operating with the atomic clock at said third location, correcting said third and fourth frequencies in accordance with said error signals, detecting said first and second frequencies at said station location to be determined, simultaneously selecting one of said detected frequencies while suppressing the other of said detected frequencies, and comparing a function of said detected frequencies with said third and fourth frequencies.

17. The method described in claim 16, wherein said error signals are converted to digital signals and broadcast to said station receiver via a low band broadcast channel.

18. The method described in claim 17, including the step of determining the traveltime of said detected frequencies between said station location and the respective ones of said first and second locations as a function of a preselected common frequency.

19. The method described in claim 18, including the steps of transmitting a first frequency related signal from said first location as a function of said first preselected frequency and said common preselected frequency, transmitting a second frequency related signal from said second location as a function of said second preselected frequency and said common preselected frequency, detecting said frequency related signals at said station location, and simultaneously selecting one of said detected frequency related signals and suppressing the other of said detected frequency related signals.