Mobile object identification device

• US 5,774,795 A
• Filed: 07/17/1995
• Issued: 06/30/1998
• Est. Priority Date: 07/20/1994
• Status: Expired due to Fees

• Current Assignee: Nippondenso Co., Ltd. (DENSO Corporation)
• Original Assignee: Nippondenso Co., Ltd. (DENSO Corporation)
• Inventors: Ando, Toshihide
• Primary Examiner(s): Urban, Edward F.
• Assistant Examiner(s): ARTHUR JEANGLAUDE, GERTRUDE
• Application Number:
  US08/503,091
• Time in Patent Office: 1,079 Days
• Field of Search: 455/56.1, 455/54.1, 455/54.2, 455/61, 455/106, 455/62, 455/63, 455/68, 455/127, 455/59, 455/502, 455/510, 455/517, 455/522, 455/524, 455/562, 340/928, 342/42, 342/44, 342/51
• US Class Current: 455/106
• CPC Class Codes: G07B 15/063 using wireless information transmission between the vehicle and a fixed station identification of vehicles G08G
• CPC Class Codes: G08G 1/017 identifying vehicles G08G1/015, G08G1/054 take precedence

Abstract

A communication area for an antenna disposed on a toll collection gate and a communication area for a responder unit (IU) mounted on an automobile are arranged to coincide with each other. Communication failure in overlapping areas where a plurality of communication areas are formed in a toll collection area is prevented. When an IU receives a pilot signal-wave, a carrier-radio-wave-signal is subsequently transmitted thereto. The IU modulates the carrier-radio-wave-signal with a responding data-signal and transmits the modulated-carrier-radio-wave as a responding signal-wave. In this system, the output power of the responding signal-wave is attenuated during the round trip of the carrier-radio-wave. Therefore, the output power thereof is decreased from an original level when the pilot signal-wave is transmitted. On the other hand, when other signal waves are transmitted, their output power are restored to the original level, thereby equalizing the power of the responding signal of the IU and that of the communication signals from the antenna. Thus, steady communication is ensured.

Claims

1. A mobile object identification device for a communication area where information is exchanged between a mobile object and a station comprising:

an antenna control unit having an antenna disposed at said station for repeatedly transmitting a communication signal-wave, which includes a pilot signal and an interrogatory signal in a portion of a cycle time of said communication signal-wave and an unmodulated carrier-radio-wave through said antenna toward said communication area, and for receiving a responding signal-wave from said communication area in another portion of said cycle time; and

a responder unit mounted on said mobile object for transmitting said responding signal-wave when receiving said pilot signal and said unmodulated carrier-radio-wave subsequently, said responder unit including;

a receiving circuit receiving said unmodulated carrier-radio-wave from said communication area,

a control circuit generating a responding data-signal, and

a transmitting circuit modulating said unmodulated carrier-radio-wave with said responding data-signal and transmitting a modulated carrier-radio-wave as said responding signal-wave;

wherein

said antenna control unit comprises;

means for decreasing output power of said antenna to a prescribed level while said antenna control unit is transmitting said pilot signal of said communication signal-wave, said prescribed level being lower than the level of the output power of said antenna while said antenna control unit is transmitting said unmodulated carrier-radio-wave, to thereby decrease said communication area, and

means for switching said pilot signal to said interrogatory signal when an acknowledgment of said pilot signal is received by said antenna control unit.

2. A mobile object identification device claimed in claim 1 further comprising a gate for toll collection, wherein said antenna is disposed on said gate.

3. A mobile object identification device claimed in claim 2, wherein said antenna control unit further comprises means for transmitting said unmodulated carrier-radio-wave subsequent to said interrogatory signal.

4. A mobile object identification device claimed in claim 3 further comprising a signal-processing-circuit for processing data for said toll collection when receiving said responding signal-wave.

5. A mobile object identification device claimed in claim 2, wherein said antenna control unit further comprises a plurality of antennas disposed on said gate.

6. A mobile object identification device claimed in claim 5, wherein said antenna control unit further comprises a means for generating a plurality of said carrier-radio-waves having different frequencies and respectively assigning said carrier-radio-waves to said plurality of antennas corresponding to said communication areas overlapping with one another.

7. A mobile object identification device claimed in claim 6, wherein said means for generating a plurality of carrier-radio-waves having different frequencies further comprises circuit means for supplying said communication signal-waves to said plurality of antennas at different times.

8. A mobile object identification device claimed in claim 4, wherein said responder unit includes a communication program which controls said responder unit to stop communication for a given period after said toll collection process has been completed.

9. A mobile object identification device claimed in claim 4, wherein said responder unit includes a communication program which controls said responder unit to stop communication until a given running distance after said toll collection process has been completed.

10. A mobile object identification device claimed in claim 3, wherein said responder unit includes a communication program which controls said responder unit to stop communication until it has received said pilot signal-wave.

11. A mobile object identification device claimed in claim 10, wherein

said antenna control unit includes a plurality of antennas;

and

said responder unit includes a communication program which controls said responder unit to prohibit communication with other antennas when it has received a pilot signal-wave from one of said plurality of antennas.

12. A mobile object identification device claimed in claim 10, wherein:

said antenna control unit comprises means for transmitting a pilot signal-wave and an unmodulated-carrier-radio-wave; and

said means for transmitting said pilot signal-wave and interrogatory signal-wave transmit said pilot signal-wave at a power level lower than said interrogatory signal-wave.

13. A mobile object identification device claimed in claim 10, wherein:

said antenna control unit comprises means for transmitting an unmodulated-carrier-radio-wave; and

said means for transmitting said unmodulated-carrier-radio-wave transmits said unmodulated carrier-radio-wave at the same power level as said interrogatory signal-wave.

14. A mobile object identification device claimed in claim 1, wherein

said antenna control unit further comprises a plurality of antennas disposed on a gate.

15. A mobile object identification device claimed in claim 14, wherein

said antenna control unit further comprises means for generating a plurality of carrier-radio-waves having different frequencies, and respectively assigning said plurality of carrier-radio-waves to said plurality of antennas corresponding to said communication areas which overlap with one another.

16. A mobile object identification device claimed in claim 15, wherein

said means for generating a plurality of said carrier-radio-waves having different frequencies further comprises circuit means for supplying said communication signal-waves to said antennas at different times.

17. A mobile object identification device claimed in claim 1, wherein said pilot signal indicates that said mobile object has entered said communication area.

18. A mobile object identification device claimed in claim 1, wherein said unmodulated carrier-radio-wave is transmitted after said pilot signal.

19. A mobile object identification device claimed in claim 1, wherein

said mobile object is mounted on an automobile, and

said station is disposed at a toll road for toll collection.

20. A mobile object identification device as claimed in claim 1, wherein said antenna control unit transmits said pilot signal and said unmodulated carrier-radio-wave successively.

21. A mobile object identification device for exchanging information between a mobile object and a station comprising:

an antenna control unit having an antenna disposed at said station for repeatedly transmitting a communication signal-wave, which includes a pilot signal and an interrogatory signal in a portion of a cycle time of said communication signal-wave, and an unmodulated carrier-radio-wave through said antenna toward a first communication area, and for receiving a responding signal-wave from a second communication area in another portion of said cycle time; and

a responder unit mounted on said mobile object for transmitting said responding signal-wave when receiving said pilot signal and said unmodulated carrier-radio-wave subsequently, said responder unit including;

a receiving circuit receiving said unmodulated carrier-radio-wave from said first communication area,

a control circuit generating a responding data-signal, and

a transmitting circuit modulating said unmodulated carrier-radio-wave with said responding data-signal and transmitting a modulated carrier-radio-wave as said responding signal-wave;

wherein

said antenna control unit comprises;

means for decreasing output power of said antenna to a prescribed level lower than said unmodulated carrier-radio-wave while said antenna control unit is transmitting said pilot signal of said communication signal-wave, said prescribed level being lower than the level of the output power of said antenna while said antenna control unit is transmitting said unmodulated carrier-radio-wave, to thereby decrease said first communication area so that the first communication area of said pilot signal coincides with the second communication area of said responding signal-wave, and

means for switching said pilot signal to said interrogatory signal when an acknowledgment of said pilot signal is received by said antenna control unit.

22. A mobile object identification device claimed in claim 21, further comprising a gate for toll collection, wherein said antenna is disposed on said gate.

23. A mobile object identification device claimed in claim 22, wherein said antenna control unit comprises means for transmitting said unmodulated carrier-radio-wave subsequent to said interrogatory signal-wave.

24. A mobile object identification device claimed in claim 23, further comprising a signal-processing-circuit for processing data for said toll collection when receiving said responding signal-wave.

25. A mobile object identification device claimed in claim 22, wherein said antenna control unit further comprises a plurality of antennas disposed on said gate.

26. A mobile object identification device claimed in claim 25, wherein said antenna control unit further comprises means for generating a plurality of carrier-radio-waves having different frequencies, and respectively assigning said carrier-radio-waves to said plurality of antennas corresponding to said communication areas which overlap with one another.

27. A mobile object identification device claimed in claim 26, wherein said means for generating a plurality of carrier-radio-waves having different frequencies further comprises circuit means for supplying said communication signal-waves to said plurality of antennas at different times.

28. A mobile object identification device claimed in claim 24, wherein said responder unit includes a communication program which controls said responder unit to stop communication for a given period after said toll collection process has been completed.

29. A mobile object identification device claimed in claim 24, wherein said responder unit includes a communication program which controls said responder unit to stop communication until a given running distance after said toll collection process has been completed.

30. A mobile object identification device claimed in claim 22, wherein said antenna control unit comprises means for transmitting said pilot signal and an unmodulated carrier-radio-wave successively, and an interrogatory signal-wave after receiving said responding signal-wave from said responder unit.

31. A mobile object identification device claimed in claim 30, wherein said responder unit includes a communication program which controls said responder unit to stop communication until it has received said pilot signal-wave.

32. A mobile object identification device claimed in claim 31, wherein said responder unit includes a communication program which controls said responder unit to prohibit communication with other antennas when it has received a pilot signal-wave from one of said antennas.

33. A mobile object identification device claimed in claim 31, wherein said means for transmitting said pilot signal-wave and interrogatory signal wave transmit said pilot signal-wave at a power level lower than said interrogatory signal-wave.

34. A mobile object identification device claimed in claim 31, wherein said means for transmitting said unmodulated carrier-radio-wave transmits said unmodulated carrier-radio-wave at the same power level as said interrogatory signal-wave.

35. A mobile object identification device claimed in claim 21, wherein said pilot signal indicates that said mobile object has entered said communication area.

36. A mobile object identification device claimed in claim 21, wherein said unmodulated carrier-radio-wave is transmitted after said pilot signal.

37. A mobile object identification device claimed in claim 21, wherein

said mobile object is mounted on an automobile, and

said station is disposed at a toll road for toll collection.

38. A mobile object identification device as claimed in claim 21, wherein said antenna control unit transmits said pilot signal and said unmodulated carrier-radio-wave successively.

39. A mobile object identification device where information is exchanged between a mobile object and a station comprising:

an antenna control unit having an antenna disposed at said station for repeatedly transmitting a communication signal-wave which includes a pilot signal and an interrogative signal in a portion of a cycle time of said communication signal-wave through said antenna toward a first communication area and receiving a responding signal-wave from a second communication area in another portion of said cycle time; and

a responder unit mounted on said mobile object for transmitting said responding signal-wave when receiving said communication signal-wave, said responder unit including

a circuit for transmitting said responding data-signal as said responding signal-wave;

wherein

said antenna control unit comprises;

means for decreasing output power of said antenna to a prescribed level while said antenna control unit is transmitting said pilot signal of said communication signal-wave, said prescribed level being lower than the level of the output power of said antenna while said antenna control unit is transmitting said interrogative signal, to thereby decrease the first communication area, and

means for switching said pilot signal to said interrogative signal when an acknowledgment of said pilot signal is received by said antenna control unit.

40. A mobile object identification device claimed in claim 39, wherein said means for decreasing output power of said antenna decreases said output power so that said first communication area of said pilot signal coincides with said second communication area of said responding signal-wave.

41. A mobile object identification device claimed in claim 39, wherein

said antenna control unit further comprises a plurality of antennas disposed on a gate.

42. A mobile object identification device claimed in claim 41, wherein

said antenna control unit further comprises means for generating a plurality of carrier-radio-waves having different frequencies, and respectively assigning said carrier-radio-waves to said plurality of antennas corresponding to said communication areas which overlap with one another.

43. A mobile object identification device claimed in claim 42, wherein

said means for generating said carrier-radio-waves having different frequencies further comprises circuit means for supplying said communication signal-waves to said plurality of antennas at different times.

44. A mobile object identification device claimed in claim 39, wherein said pilot signal indicates that said mobile object has entered said communication area.

45. A mobile object identification device claimed in claim 39, wherein an unmodulated carrier-radio-wave is transmitted by said antenna control unit after said pilot signal is transmitted by said antenna control unit.

46. A mobile object identification device claimed in claim 39, wherein said interrogative signal causes said responder unit to read data stored therein and transmit said stored data.

47. A mobile object identification device claimed in claim 39, wherein

said mobile object is mounted on an automobile, and

said station is disposed at a toll road for toll collection.

48. A mobile object identification device as claimed in claim 39, wherein said antenna control unit transmits said pilot signal and an unmodulated carrier-radio-wave successively.