MOBILE LOCATOR SYSTEM FOR METROPOLITAN AREAS

• US 3,680,121 A
• Filed: 01/02/1970
• Issued: 07/25/1972
• Est. Priority Date: 01/02/1970
• Status: Expired due to Term

• Current Assignee: Miguel A. Merigo, Roy E. Anderson
• Original Assignee: Miguel A. Merigo, Roy E. Anderson
• Inventors: Anderson, Roy E., Merigo, Miguel A.
• Primary Examiner(s): Quarforth, Carl D.
• Assistant Examiner(s): Potenza, J. M.
• Application Number:
  US05/000,361
• Time in Patent Office: 935 Days
• Field of Search: 343/105,112TC,6.5LC,7.5
• US Class Current: 342/457
• CPC Class Codes: G01S 3/72 Diversity systems specially adapted for direction-finding
• CPC Class Codes: G01S 5/06 Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements G01S5/12 takes precedence

Abstract

A locator system is disclosed wherein the vehicle whose location is unknown transmits a short, modulated radio frequency pulse. Receiving stations about the periphery of the area being serviced phase compare the received signal with a standard time reference signal. The phase difference is used to determine the arrival time differences at the known locations of the receiving stations from which the location of the vehicle may be determined. The wavelength of the modulating signal is generally greater than the maximum distance encountered in the service area. The effects of multipath reflections are minimized by utilizing a space dispersed antenna.

Claims

1. A method for locating a vehicle comprising the steps of positioning at least three receiving stations about the periphery of the area in which said vehicle may be located;

initiating narrow band transmission from said vehicle of a tone modulated signal, receiving said modulated signal at said receiving stations, and comparing the times of arrival of said modulated signal and a time reference signal to obtain range difference information so that the specific location of said vehicle within said area can be determined.

2. The method as set forth in claim 1 wherein said comparing step comprises receiving a locally generated television signal, deriving from said television signal said time reference signal, and comparing said derived time reference signal with said received modulated signal to obtain range difference information from which said vehicle may be specifically located within said area.

3. The method as set forth in claim 2 comprising the additional steps of performing said receiving, deriving, and comparing steps at said receiving station, and conveying said information from each receiving station to a central station where the specific vehicle location may be determined.

4. The method as set forth in claim 1 further comprising the steps of generating a time reference signal, and communicating said time reference signal to said receiving stations.

5. The method as set forth in claim 1 wherein said initiation is accomplished in response to voice request.

6. The method as set forth in claim 1 wherein said initiation is in response to an identification coded request.

7. The method as set forth in claim 1 wherein said initiation is accomplished automatically on a programmed basis.

8. The method as set forth in claim 1 wherein said initiation includes the step of modulating a carrier frequency with a signal whose modulating wavelength is longer than the largest dimension of said area being served.

9. The method as set forth in claim 1 wherein the duration of said initiated transmission is on the order of 64 cycles of the modulating signal.

10. The method as set forth in claim 1 including the step of providing a space dispersed antenna system for use with said receiving stations thereby minimizing the effects of multipath reflections.

11. The method as set forth in claim 10 wherein said providing step is performed at each receiving station.

12. The method as set forth in claim 1 including the step of determining the specific location of said vehicle within said area.