Method and apparatus for improving the accuracy of a vehicle location system

• US 3,886,554 A
• Filed: 04/23/1973
• Issued: 05/27/1975
• Est. Priority Date: 04/23/1973
• Status: Expired due to Term

• Current Assignee: Edward F. Handy, William V. Braun
• Original Assignee: Edward F. Handy, William V. Braun
• Inventors: Braun, William V., Handy, Edward F.
• Primary Examiner(s): Tubbesing, T. H.
• Assistant Examiner(s): Buczinski, S. C.
• Application Number:
  US05/353,286
• Time in Patent Office: 764 Days
• Field of Search: 343/112R,112TC,103,102,114,115
• US Class Current: 342/457
• CPC Class Codes: G01S 3/72 Diversity systems specially adapted for direction-finding
• CPC Class Codes: G01S 5/04 Position of source determined by a plurality of spaced direction-finders

Abstract

Method and apparatus for improving the accuracy of a vehicle location system, particularly of a phase ranging type, by reducing the effects of multipath propagation through the use of a variable pattern antenna for the vehicle transmitter. Separate range measurements are made using each antenna pattern, and the measurements are averaged to provide a more accurate reading.

Claims

1. The method of locating the position of a vehicle comprising the steps of:

radiating a radio signal from the vehicle in a predetermined radiation pattern;

switching the directivity of said radiation pattern to a predetermined sequence of radiation patterns;

receiving said radio signal in said sequence of radiation patterns at two geographically spaced receiving sites;

comparing the signals received at said two sites to determine the location of said vehicle.

2. The method recited in claim 1 wherein the step of receiving said radio signal includes the steps of;

receiving a first signal radiated in a first radiation pattern at each of said receiving sites, and receiving a second signal radiated in a second radiation pattern at each of said receiving sites.

3. The method recited in claim 2 wherein said step of comparing said signals includes the steps of;

comparing said fiirst signals received at said sites to provide a first location reading, comparing said second signals received at said sites to provide a second location reading, and determining said location in response to said first and second location readings.

4. The method recited in claim 3 wherein the step of radiating the radio signal includes the step of modulating said radio signal with a predetermined frequency tone, the step of receiving said radio signals includes the step of detecting said tone at each of said receiving sites, and the step of comparing said received signals includes the step of comparing the phases of the tones detected at each site to determine said location readings.

5. The method recited in claim 4 wherein said location is determined by the step of automatically determining the average of said location readings, and displaying a location indicative of said average.

6. In a vehicle location system for locating a vehicle emploYing a mobile transmitter for transmitting radio signals, and a plurality of receiving sites for receiving and comparing the signals received thereby from the mobile transmitter, an antenna system comprising;

a plurality of radiating elements mounted on said vehicle; and

means for selectively applying radio signals to said elements in a predetermined sequence connected to said transmitter and to said elements.

7. An antenna system as recited in claim 6 further including control means connected to said transmitter and to said selective application means for rendering said transmitter operative to provide radio signals for a predetermined time interval, said selective application means being responsive to said control means for applying said radio signals to said elements in said predetermined sequence during said predetermined time interval.

8. An antenna system as recited in claim 7 further including phase shifting means coupled to said selective application means for varying the phase of the radio signals applied to said radiating elements.

9. A system for locating the position of a vehicle within a predetermined geographic area including in combination:

radio transmitting means carried by the vehicle for providing radio signals;

variable radiation pattern antenna means connected to said radio transmitting means for receiving said radio signals from said transmitting means and radiating said signals from the vehicle in a sequentially switched plurality of different directivity radiation patterns;

a plurality of receiving means for receiving the radio signals from said radio transmitting means;

means coupled to said receiving means for comparing the radio signals, received in the plurality of different radiation patterns by each of said receiving means, to provide an indication of the location of said vehicle.

10. A vehicle location system as recited in claim 9 including control means coupled to said transmitting means and to said variable radiation pattern antenna means for rendering said transmitting means operative and for sequentially varying the radiation pattern to cause said radio signals to be radiated in said plurality of different directivity radiation patterns.

11. A vehicle location system as recited in claim 10 wherein said comparing means includes means for providing a plurality of location readings in response to said radio signals, each location reading corresponding to a different radiation pattern and means for combining said location readings to provide said indication of vehicle location.

12. A vehicle location system as recited in claim 11 wherein said variable radiation pattern antenna means includes a plurality of radiating elements, and said control means includes means coupled to said elements for selectively applying said radio signals to said elements in a predetermined sequence to vary said radiation pattern.

13. A vehicle location system as recited in claim 12 wherein said control means further includes phase shift means for varying the phase of the radio signals applied to said elements.

14. A vehicle location system as recited in claim 13 wherein said transmitting means includes means for modulating said radio signal with a predetermined frequency tone, and each of said receiving means includes means for demodulating said radio signal to detect the predetermined frequency tone.

15. A vehicle location system as recited in claim 14 wherein said comparing means includes means connected to each of said demodulating means for comparing the phases of said detected tones to provide one of said location readings in response to each comparison.

16. A vehicle location system as recited in claim 15 wherein said combining means includes means for deriving the average of said location readings.