OPTIMUM PSEUDO RANDOM SEQUENCE DETERMINING METHOD, POSITION DETECTION SYSTEM, POSITION DETECTION METHOD, TRANSMISSION DEVICE AND RECEPTION DEVICE

• US 20110261654A1
• Filed: 08/29/2008
• Published: 10/27/2011
• Est. Priority Date: 08/30/2007
• Status: Active Grant

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Kajitani, Hiroshi, Miyamoto, Junichi
• Granted Patent: US 8,427,905 B2
• Time in Patent Office: Days
• US Class Current: 367/125
• CPC Class Codes: G01S 11/14 using ultrasonic, sonic, or infrasonic waves
• CPC Class Codes: G01S 11/16 using difference in transit time between electrical and acoustic signals
• CPC Class Codes: G01S 5/18 using ultrasonic, sonic, or infrasonic waves

Abstract

To enable precise calculation of a propagation time of a direct wave which arrives fastest from an ultrasonic generation source without being affected by a reflected wave of an ultrasonic signal.

A plurality of ultrasonic signals generated based on a plurality of M sequences different from each other are propagated from a transmission side to a reception side, whereby the reception side generates model waveforms of the plurality of M sequences, executes correlation processing between each model waveform and a waveform of each ultrasonic signal and detects a secondary peak of a correlation value which appears when both waveforms partly coincide with each other to determine an M sequence which generates a smallest secondary peak among secondary peaks detected by all the correlation processing as an optimum M sequence. The transmission side sends out an electromagnetic signal and an ultrasonic signal modulated by an optimum M sequence generated based on an initial condition of the optimum M sequence to the reception side. The reception side calculates a correlation value between the ultrasonic signal and a model waveform of the ultrasonic modulated by the optimum M sequence, detects a first primary peak of the calculated correlation value and calculates an ultrasonic propagation time from a time point of the reception of the electromagnetic signal and a time point of the detection of the primary peak.

Claims

1. An optimum pseudo random sequence determining method, comprising the steps:

a) sending, from a transmission side, an ultrasonic signal modulated by data of a pseudo random sequence generated based on data which defines a pseudo random sequence having high self-correlativity;

b) receiving the ultrasonic signal at a reception side, generating an ultrasonic model waveform of a pseudo random sequence of said ultrasonic signal and executing processing of correlation between the ultrasonic model waveform and the received ultrasonic signal to detect a correlation waveform; and

c) with respect to data of different pseudo random sequences, repeatedly executing said Steps (a) and (b), detecting said correlation waveform in plural, detecting a smallest secondary peak among secondary peaks appearing in each correlation waveform when said ultrasonic model waveform and the received ultrasonic signal coincide in part and determining data of a pseudo random sequence corresponding to the smallest secondary peak as data of an optimum pseudo random sequence.

2. The optimum pseudo random sequence determining method according to claim 1, wherein at said Step (b), a largest secondary peak appearing in each said correlation waveform is detected and at said Step (c), a peak with a smallest value among a plurality of largest secondary peaks appearing in all the correlation waveforms is detected as said smallest secondary peak.

3-4. -4. (canceled)

5. A position detection system including at least one transmission device and a reception device for detecting a position of said transmission device, wherein

said transmission device transmits a first ultrasonic signal modulated by data of a pseudo random sequence having high self-correlativity,

said reception device generates an ultrasonic model waveform of a pseudo random sequence of said first ultrasonic signal received, obtains a correlation value between a waveform of said first ultrasonic signal received and said ultrasonic model waveform generated, determines data which defines an optimum pseudo random sequence with which a secondary peak of said correlation value becomes the smallest and assigns the data to said transmission device,

said transmission device simultaneously sends a trigger signal indicative of transmission timing and a second ultrasonic signal modulated by data of a pseudo random sequence generated based on data which defines an optimum pseudo random sequence assigned by said reception device, and

said reception device executes correlation processing between a waveform of a second ultrasonic signal received and an ultrasonic model waveform of a pseudo random sequence of said second ultrasonic signal to specify an arrival time of said ultrasonic signal and calculates a propagation time of the ultrasonic from an arrival time point of said trigger signal and the specified arrival time to detect a position of said transmission device based on said ultrasonic propagation time calculated.

6. The position detection system according to claim 5, wherein

said reception device determines data which defines a plurality of pseudo random sequences, starting with a sequence with which a secondary peak of said correlation value is the smallest, and assigns the data which defines the plurality of pseudo random sequences to the plurality of said transmission devices.

8. The position detection system according to claim 5, wherein

said reception device determines a characteristic polynomial in addition to data which defines said pseudo random sequence, and

said transmission device generates an ultrasonic signal modulated by data of said pseudo random sequence by using the data which defines said pseudo random sequence and said characteristic polynomial.

9. The position detection system according to claim 5, wherein

said transmission device transmits a plurality of first ultrasonic signals modulated by data of a plurality of pseudo random sequences different from each other which have high self-correlativity,

said reception device generates an ultrasonic model waveform of a pseudo random sequence of said first ultrasonic signal, executes correlation processing between each ultrasonic model waveform and a waveform of each first ultrasonic signal to detect a secondary peak of a correlation value, determines data of a pseudo random sequence which generates a smallest secondary peak among secondary peaks detected in all the correlation processing as data of an optimum pseudo random sequence and assigns the data to said transmission device,

said transmission device simultaneously sends a trigger signal indicative of transmission timing and a second ultrasonic signal modulated by data of an optimum pseudo random sequence assigned by the reception device, and

said reception device calculates a correlation value between a waveform of a second ultrasonic signal received and an ultrasonic model waveform of a pseudo random sequence of said second ultrasonic signal, detects a primary peak of the calculated correlation value and calculates an ultrasonic propagation time from a time point of reception of said trigger signal and a time point of detection of the primary peak to detect a position of said transmission device based on said ultrasonic propagation time calculated.

10. The position detection system according to claim 9, wherein

said reception device generates an ultrasonic model waveform of a pseudo random sequence of the plurality of the first ultrasonic signals, executes correlation processing between each ultrasonic model waveform and a waveform of each first ultrasonic signal to detect a secondary peak of a correlation value, determines data of a plurality of pseudo random sequences, starting with a sequence with which a secondary peak detected in all the correlation processing is the smallest, and assigns the data of the plurality of pseudo random sequences to each said transmission device different from each other.

12. The position detection system according to claim 9, wherein said reception device detects a largest secondary peak of each said correlation value to detect a peak with a smallest value among a plurality of largest secondary peaks of all the correlation values as said smallest secondary peak.

13. The position detection system according to claim 9, wherein

said transmission device simultaneously sends said trigger signal including data which defines a pseudo random sequence and an ultrasonic signal modulated by data of a pseudo random sequence generated based on the data which defines the pseudo random sequence, and

said reception device generates an ultrasonic model waveform of an ultrasonic signal modulated by data of a pseudo random sequence generated based on data which defines a pseudo random sequence that is included in a received trigger signal, detects a plurality of correlation values between the ultrasonic model waveform and the received ultrasonic signal, detects a largest secondary peak appearing in the vicinity of a primary peak from the plurality of correlation values and obtains said secondary peak in plural with respect to data of different pseudo random sequences to determine data of a pseudo random sequence corresponding to a smallest secondary peak among the plurality of secondary peaks as data of said optimum pseudo random sequence.

14. The position detection system according to claim 9, wherein

said transmission device sends said trigger signal including data which defines a pseudo random sequence differing in each transmission cycle and data indicative of a characteristic polynomial differing in each transmission cycle, and

said reception device generates said ultrasonic model waveform based on the data which defines a pseudo random sequence and the characteristic polynomial data that are included in said trigger signal received.

21. The position detection system according to claim 9, wherein with n cycles of an ultrasonic signal assigned to one bit of data of said pseudo random sequence, said transmission device modulates a phase of the ultrasonic and with n cycles of an ultrasonic signal assigned to one bit of the data of said pseudo random sequence, said reception device modulates a phase of the ultrasonic signal to generate said ultrasonic signal model waveform, thereby detecting a largest secondary peak from among peaks appearing not later than (n−

1) cycles before a primary peak of said correlation value.

7. (canceled)

11. (canceled)

15-20. -20. (canceled)

22-23. -23. (canceled)

24. A position detection method, wherein

at least one transmission device executes the step of transmitting a first ultrasonic signal modulated by data of a pseudo random sequence having high self-correlativity,

a reception device for detecting a position of said transmission device executes the step of generating an ultrasonic model waveform of a pseudo random sequence of said first ultrasonic signal received, obtaining a correlation value between a waveform of said first ultrasonic signal received and said ultrasonic model waveform generated, determining data which defines an optimum pseudo random sequence with which a secondary peak of said correlation value becomes the smallest and assigning the data to said transmission device,

said transmission device executes the step of simultaneously sending a trigger signal indicative of transmission timing and a second ultrasonic signal modulated by data of a pseudo random sequence generated based on data which defines an optimum pseudo random sequence assigned by said reception device, and

said reception device executes the step of executing correlation processing between a waveform of a second ultrasonic signal received and an ultrasonic model waveform of a pseudo random sequence of said second ultrasonic signal to specify an arrival time of said ultrasonic signal, calculating a propagation time of the ultrasonic from an arrival time point of said trigger signal and the specified arrival time and detecting a position of said transmission device based on said ultrasonic propagation time calculated.

25. The position detection method according to claim 24, wherein

a reception device for detecting a position of said transmission device executes the step of determining data which defines a plurality of pseudo random sequences, starting with a sequence with which a secondary peak of said correlation value is the smallest, and assigning the data which defines the plurality of pseudo random sequences to the plurality of said transmission devices.

27. The position detection method according to claim 24, wherein

said reception device executes the step of determining a characteristic polynomial in addition to data which defines said pseudo random sequence, and

said transmission device executes the step of generating an ultrasonic signal modulated by data of said pseudo random sequence by using the data which defines said pseudo random sequence and said characteristic polynomial.

28. The position detection method according to claim 24, wherein

said transmission device executes the step of sending out a plurality of first ultrasonic signals modulated by data of a plurality of pseudo random sequences different from each other which have high self-correlativity,

said reception device for detecting a position of said transmission device executes the step of generating an ultrasonic model waveform of a pseudo random sequence of said first ultrasonic signal, executing correlation processing between each ultrasonic model waveform and a waveform of each first ultrasonic signal to detect a secondary peak of a correlation value, determining data of a pseudo random sequence which generates a smallest secondary peak among secondary peaks detected in all the correlation processing as data of an optimum pseudo random sequence and assigning the data to said transmission device,

said transmission device executes the step of simultaneously sending a trigger signal indicative of transmission timing and a second ultrasonic signal modulated by data of an optimum pseudo random sequence assigned by the reception device, and

said reception device executes the step of calculating a correlation value between a waveform of a second ultrasonic signal received and an ultrasonic model waveform of a pseudo random sequence of said second ultrasonic signal, detecting a primary peak of the calculated correlation value, calculating an ultrasonic propagation time from a time point of reception of said trigger signal and a time point of detection of the primary peak to detect a position of said transmission device based on said ultrasonic propagation time calculated.

29. The position detection method according to claim 28, wherein

said reception device for detecting a position of said transmission device executes the step of generating an ultrasonic model waveform of a pseudo random sequence of the plurality of the first ultrasonic signals, executing correlation processing between each ultrasonic model waveform and a waveform of each first ultrasonic signal to detect a secondary peak of a correlation value, determining data of a plurality of pseudo random sequences, starting with a sequence with which a secondary peak detected in all the correlation processing is the smallest, and assigning the data of the plurality of pseudo random sequences to each said transmission device different from each other.

31. The position detection method according to claim 28, wherein said reception device detects a largest secondary peak of each said correlation value to detect a peak with a smallest value among a plurality of largest secondary peaks of all the correlation values as said smallest secondary peak.

32. The position detection method according to claim 28, wherein

said transmission device executes the step of simultaneously sending said trigger signal including data which defines a pseudo random sequence and an ultrasonic signal modulated by data of a pseudo random sequence generated based on the data which defines the pseudo random sequence, and

said reception device executes the step of generating an ultrasonic model waveform of an ultrasonic signal modulated by data of a pseudo random sequence generated based on data which defines a pseudo random sequence that is included in a received trigger signal, detecting a plurality of correlation values between the ultrasonic model waveform and the received ultrasonic signal, detecting a largest secondary peak appearing in the vicinity of a primary peak from the plurality of correlation values and obtaining said secondary peak in plural with respect to data of different pseudo random sequences to determine data of a pseudo random sequence corresponding to a smallest secondary peak among the plurality of secondary peaks as data of said optimum pseudo random sequence.

33. The position detection method according to claim 28, wherein

said transmission device executes the step of sending said trigger signal including data which defines a pseudo random sequence differing in each transmission cycle and data indicative of a characteristic polynomial differing in each transmission cycle, and

said reception device executes the step of generating said ultrasonic model waveform based on the data which defines a pseudo random sequence and the characteristic polynomial data that are included in said trigger signal received.

40. The position detection method according to claim 28, wherein with n cycles of an ultrasonic signal assigned to one bit of data of said pseudo random sequence, said transmission device modulates a phase of the ultrasonic and with n cycles of an ultrasonic signal assigned to one bit of the data of said pseudo random sequence, said reception device modulates a phase of the ultrasonic signal to generate said ultrasonic signal model waveform, thereby detecting a largest secondary peak from among peaks appearing not later than (n−

1) cycles before a primary peak of said correlation value.

26. (canceled)

30. (canceled)

34-39. -39. (canceled)

41-68. -68. (canceled)