Simple mobile object position detecting system

• US 6,269,302 B1
• Filed: 12/01/1998
• Issued: 07/31/2001
• Est. Priority Date: 12/01/1997
• Status: Expired due to Fees

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Yoshida, Yasuharu
• Primary Examiner(s): NGUYEN, TAN QUANG
• Application Number:
  US09/201,823
• Time in Patent Office: 973 Days
• Field of Search: 701/217, 701/220, 701/223, 701/117, 701/118, 701/207, 705/13, 340/928, 340/937, 340/938, 340/947, 340/943, 342/74, 342/76, 342/81, 342/454, 342/457
• US Class Current: 701/207
• CPC Class Codes: G01S 3/48 the waves arriving at the antennas being continuous or intermittent and the phase difference of signals derived therefrom being measured
• CPC Class Codes: G01S 5/0249 Determining position using measurements made by a non-stationary device other than the device whose position is being determined
• CPC Class Codes: G08G 1/017 identifying vehicles G08G1/015, G08G1/054 take precedence
• CPC Class Codes: H01Q 1/3225 Cooperation with the rails or the road
• CPC Class Codes: H01Q 1/3233 particular used as part of a sensor or in a security system, e.g. for automotive radar, navigation systems

Abstract

In a mobile object position detecting system for detecting a position of a mobile object having a transmitter, an elongated antenna system is provided for receiving a radio wave signal from the transmitter and outputting first and second electrical signals from first and second ends of the antenna system, respectively. A position detector calculates the position of the mobile object in accordance with a difference in time between the first and second electrical signals.

Claims

1. A mobile object position detecting system for detecting a position of a mobile object having a transmitter, comprising:

an elongated antenna system that receives a direct radio wave signal from said transmitter and outputs first and second electrical signals from first and second ends of said antenna system, respectively, wherein said elongated antenna system emphasizes a surface wave mode; and

a position detector, coupled to the first and second ends of said antenna system, that calculates the position of said mobile object in accordance with a difference in time between said first and second electrical signals.

2. The system as set forth in claim 1, wherein said antenna system comprises:

a plurality of antenna elements coupled in series and closely arranged in a row; and

a plurality of branching/combining units coupled in a series, each of said branching/combining units coupled to one of said antenna elements,

said position detector coupled to two of said branching/combining units located at ends of the series of said branching/combining units.

3. The system as set forth in claim 1, wherein said position detector comprises:

first and second receivers coupled to said first and second ends, respectively, of said antenna system;

a phase comparator, coupled to said first and second receivers, that compares a phase of an output signal of said first receiver with a phase of an output signal of said second receiver; and

a position calculating unit, coupled to said phase comparator, that calculates the position of said mobile object in accordance with an output signal of said phase comparator.

4. The system as set forth in claim 3, wherein said position detector further comprises an initial phase adjusting unit, coupled between said phase comparator and one of said first and second receivers.

5. The system as set forth in claim 4, wherein a delay time of said initial phase adjusting unit is determined so that the output signal of said phase comparator shows a phase difference between inputs of said phase comparator is zero when said mobile object is located at a center of said antenna system.

6. The system as set forth in claim 5, wherein said position detector calculates the position of said mobile object by

7. The system as set forth in claim 1, wherein said position detector comprises:

first and second receivers coupled to said first and second ends, respectively, of said antenna system;

first and second edge detectors, coupled to said first and second receivers, respectively, to detect edges of output signals of said first and second receivers; and

a counter coupled to said first and second edge detectors, to start a counting operation of pulses of a clock signal upon receipt of an output signal of one of said first and second edge detectors and to stop said counting operation upon receipt of an output signal of the other of said first and second edge detectors.

8. The system as set forth in claim 7, wherein said position detector further comprises an initial phase adjusting unit, coupled between one of said first and second receivers and one of said first and second edge detectors.

9. The processor as set forth in claim 8, wherein a delay time of said initial phase adjusting unit is determined so that the output value of said counter shows zero when said mobile object is located at one of said first and second ends of said antenna system.

10. The system as set forth in claim 1, wherein said antenna system comprises a leakage coaxial conductor constructed by an external conductor and a center conductor penetrating said external conductor, said external conductor having zigzag perforated slots.

11. The system as set forth in claim 10, wherein said leakage coaxial conductor comprises an outer conductor and an inner conductor within said outer conductor, said outer conductor having perforated slots.

12. The system as set forth in claim 11, wherein said perforated slots are zigzag.

13. The system as set forth in claim 1, wherein said antenna system comprises a leakage waveguide.

14. The system as set forth in claim 1, wherein said mobile object is a vehicle, so that said mobile object position detecting system is constructed as an electronic toll collection system.

15. The system of claim 1, wherein said antenna system is positioned at least one of directly below and in a path of said mobile object, and no soundproof wall is required.

16. A mobile object position detecting system for detecting a position of a mobile object having a transmitter, comprising:

first and second antennas, located apart from each other, that receives a radio wave signal from said transmitter and output first and second electrical signals, respectively; and

a position detector, coupled to said first and second antennas, that calculates the position of said mobile object in accordance with a difference in time between said first and second electrical signals.

17. The system as set forth in claim 16, wherein said position detector comprises:

first and second receivers coupled to said first and second antennas, respectively;

a phase comparator, coupled to said first and second receivers, that compares a phase of an output signal of said first receiver with a phase of an output signal of said second receiver; and

a position calculating unit, coupled to said phase comparator, that calculates the position of said mobile object in accordance with an output signal of said phase comparator.

18. The system as set forth in claim 17 wherein said position detector further comprises an initial phase adjusting unit, coupled between said phase comparator and one of said first and second receivers.

19. The system as set forth in claim 18, wherein a delay time of said initial phase adjusting unit is determined so that the output signal of said phase comparator shows a phase difference between inputs of said phase comparator is zero when said mobile object is located at a center of said antenna system.

20. The system as set forth in claim 19, wherein said position detector calculates the position of said mobile object by

21. The system as set forth in claim 16, wherein said position detector comprises:

first and second receivers coupled to said first and second antennas, respectively;

first and second edge detectors, coupled to said first and second receivers, respectively, to detect edges of output signals of said first and second receivers; and

a counter coupled to said first and second edge detectors, to start a counting operation of pulses of a clock signal upon receipt of an output signal of one of said first and second edge detectors and to stop said counting operation upon receipt of an output signal of the other of said first and second edge detectors.

22. The system as set forth in claim 21, wherein said position detector further comprises an initial phase adjusting unit, coupled between one of said first and second receivers and one of said first and second edge detectors.

23. The system as set forth in claim 22, wherein a delay time of said initial phase adjusting unit is determined so that the output value of said counter shows zero when said mobile object is located at one of said first and second antennas.

24. The system as set forth in claim 16, wherein said mobile object is a vehicle, so that said mobile object position detecting system is constructed as an electronic toll collection system.

25. A method of detecting a position of a mobile object, comprising:

establishing communication with the mobile object via a first portion of an antenna system substantially positioned in a path of travel of said mobile object;

registering said communication in a personal computer; and

generating said transmitting a sampling signal to a position detector, wherein said sampling signal is determined by calculating a mobile object position.

26. The method of claim 25, further comprising receiving said calculated mobile object position in said personal computer and comparing said calculated mobile object position to a predetermined range of values.

27. The method of claim 26, further comprising completing a transaction for said mobile object if said calculated mobile object position falls within said predetermined range.

28. The method of claim 27, wherein said completing said transaction comprises electronically collecting a toll.

29. The method of claim 27, further comprising imaging and identifying said mobile object.

30. The method of claim 26, further comprising requesting an operator of said mobile object to complete a task if said calculated vehicle position does not fall within said predetermined range.

31. The method of claim 25, further comprising simultaneously conducting said determining, registering and generating steps to calculate an adjacent mobile object position for an adjacent mobile object positioned proximally to said mobile object via a second portion of said antenna system.

32. The method of claim 31, further comprising computing a distance between said mobile object and said adjacent mobile object in accordance with said calculated adjacent method object position.

33. The method of claim 25, further comprising detecting a phase difference between an input signal received from said mobile object and a second object to determine a distance between said first mobile object and said second object.