Ultrasonic measuring apparatus and ultrasonic measuring method

• US 7,617,731 B2
• Filed: 11/09/2006
• Issued: 11/17/2009
• Est. Priority Date: 07/18/2006
• Status: Active Grant

• Current Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Wang, Yong, Hashimoto, Masahiko, Suginouchi, Takehiko
• Primary Examiner(s): Williams; Hezron
• Assistant Examiner(s): MILLER, ROSE MARY
• Application Number:
  US11/718,001
• Publication Number:
  US 20090145232A1
• Time in Patent Office: 1,104 Days
• Field of Search: 736/02, 702/159
• US Class Current: 73/602
• CPC Class Codes: G01S 15/003 Bistatic sonar systems; Multistatic sonar systems
• CPC Class Codes: G01S 15/325 using transmission of coded signals, e.g. of phase-shift keyed [PSK] signals
• CPC Class Codes: G01S 7/536 Extracting wanted echo signals
• CPC Class Codes: H04B 11/00 Transmission systems employing sonic, ultrasonic or infrasonic waves

Abstract

An ultrasonic measuring method includes the steps of: receiving ultrasonic waves, which have been transmitted by a spread spectrum technique using mutually different codes, at first and second receivers, thereby generating first and second received signals, respectively; generating interference signals, of which the amplitudes are equal to or greater than respective threshold values, from the first and second received signals that have been despread with a code that has been used to spread any of the ultrasonic waves other than a desired one; removing the spread interference signals from the first and second received signals; calculating maximum correlation values between the first and second despread received signals for the respective threshold values; selecting one of the threshold values, at which the greatest one of the maximum correlation values has been obtained, as a threshold value for canceling interference; and calculating the propagation distance or propagation azimuth of the desired ultrasonic wave by the amount of time it has taken for the first and second received signals to arrive.

Claims

1. An ultrasonic measuring method for estimating at least one of the propagation distance and the propagation azimuth of a desired ultrasonic wave, which is one of a number of ultrasonic waves that have been transmitted by a spread spectrum technique using mutually different codes, the method comprising the steps of:

(A1) receiving the ultrasonic waves, which have been transmitted by the spread spectrum technique using the mutually different codes, at first and second receivers, thereby generating first and second received signals, respectively;

(B1) despreading the first and second received signals with a code that has been used to spread any of the ultrasonic waves other than the desired one, thereby generating at least one despread signal;

(C1) extracting a plurality of signals, of which the amplitudes are equal to or greater than respective threshold values, from the despread signal using the threshold values, thereby generating mutually different interference signals for the respective threshold values;

(D1) spreading the interference signals with the code that has been used to spread the ultrasonic wave other than the desired one and then removing the interference signals from the first and second received signals, thereby generating first and second received signals, from which the interference signals have been removed, for the respective threshold values;

(E1) despreading the first and second received signals, from which the interference signals have been removed, with the code of the desired ultrasonic wave, thereby generating first and second despread received signals, from which the interference signals have been removed, for the respective threshold values;

(F1) calculating maximum correlation values between the first and second despread received signals for the respective threshold values;

(G1) determining at which of the threshold values the greatest one of the maximum correlation values has been obtained; and

(H1) calculating at least one of the propagation distance and the propagation azimuth of the desired ultrasonic wave by the amount of time it has taken for the first and second despread received signals, associated with the threshold value determined, to reach the first and second receivers.

2. The method of claim 1, wherein using a plurality of preset threshold values, the steps (C1) through (F1) are performed on the respective threshold values in parallel with each other.

3. The method of claim 1, wherein the codes are M-sequence pseudo spread codes.

4. The method of claim 1, wherein 0 and 180 degree phases of the ultrasonic waves are allocated to the codes.

5. The method of claim 1, wherein the maximum correlation value between the first and second despread received signals is calculated by finding correlation between complex numbers.

6. An ultrasonic measuring method for estimating at least one of the propagation distance and the propagation azimuth of a desired ultrasonic wave, which is one of a number of ultrasonic waves that have been transmitted by a spread spectrum technique using mutually different codes, the method comprising the steps of:

(A2) receiving the ultrasonic waves, which have been transmitted by the spread spectrum technique using the mutually different codes, at first and second receivers, thereby generating first and second received signals, respectively;

(B2) despreading the first and second received signals with a code that has been used to spread any of the ultrasonic waves other than the desired one, thereby generating at least one despread signal;

(C2) extracting a signal, of which the amplitude is equal to or greater than a threshold value, from the despread signal using the threshold value, thereby generating an interference signal;

(D2) spreading the interference signal with the code that has been used to spread the ultrasonic wave other than the desired one and then removing the interference signal from the first and second received signals, thereby generating first and second received signals, from which the interference signal has been removed;

(E2) despreading the first and second received signals, from which the interference signal has been removed, with the code of the desired ultrasonic wave, thereby generating first and second despread received signals, from which the interference signal has been removed;

(F2) calculating a maximum correlation value between the first and second despread received signals;

(G2) performing the steps (B2) through (F2) with the threshold values changed;

(H2) repeatedly performing the step (G2) until a difference between the maximum correlation value and its previous value becomes equal to or smaller than a predetermined value; and

(I2) calculating at least one of the propagation distance and the propagation azimuth of the desired ultrasonic wave by the amount of time it has taken for the first and second despread received signals, associated with the threshold value at which the difference between the maximum correlation value and its previous value becomes equal to or smaller than the predetermined value, to reach the first and second receivers.

7. The method of claim 6, wherein the step (H2) includes determining the threshold value by the difference between the maximum correlation value and its previous value.

8. An ultrasonic measuring apparatus for estimating at least one of the propagation distance and the propagation azimuth of a desired ultrasonic wave, which is one of a number of ultrasonic waves that have been transmitted by a spread spectrum technique using mutually different codes, the apparatus comprising:

first and second receivers for receiving the ultrasonic waves, which have been transmitted by the spread spectrum technique using the mutually different codes, thereby generating respective received signals;

first and second interference canceling sections that are connected to the first and second receivers, the canceling sections despreading the received signals with a code that has been used to spread any of the ultrasonic waves other than the desired one, thereby generating at least one despread signal;

extracting a plurality of signals, of which the amplitudes are equal to or greater than respective threshold values, from the despread signal using the threshold values, thereby generating mutually different interference signals for the respective threshold values;

spreading the interference signals with the code that has been used to spread the ultrasonic wave other than the desired one and then removing the interference signals from the received signals, thereby generating received signals, from which the interference signals have been removed, for the respective threshold values;

despreading the received signals, from which the interference signals have been removed, with the code of the desired ultrasonic wave, thereby generating despread received signals, from which the interference signals have been removed, for the respective threshold values;

a correlating section for calculating maximum correlation values between the despread received signals, which have been generated by the first and second interference canceling sections and from which the interference signals have been removed, for the respective threshold values;

a selecting section for selecting one of the threshold values at which the greatest one of the maximum correlation values for the respective threshold values has been obtained; and

a distance/azimuth calculating section for calculating at least one of the propagation distance and the propagation azimuth of the desired ultrasonic wave by the amount of time it has taken for the despread received signals, which are associated with the threshold value selected and from which the interference signals have been removed, to reach the first and second receivers.

9. The ultrasonic measuring apparatus of claim 8, wherein by using a plurality of preset threshold values, the first and second interference canceling sections generate the despread received signals, from which the interference signals have been removed, for the respective threshold values.

10. The ultrasonic measuring apparatus of claim 8, wherein the codes are M-sequence pseudo spread codes.

11. The ultrasonic measuring apparatus of claim 8, wherein 0 and 180 degree phases of the ultrasonic waves are allocated to the codes.

12. The ultrasonic measuring apparatus of claim 8, wherein the correlating section calculates the maximum correlation value between the first and second despread received signals by finding correlation between complex numbers.

13. An ultrasonic measuring apparatus for estimating at least one of the propagation distance and the propagation azimuth of a desired ultrasonic wave, which is one of a number of ultrasonic waves that have been transmitted by a spread spectrum technique using mutually different codes, the apparatus comprising:

first and second receivers for receiving the ultrasonic waves, which have been transmitted by the spread spectrum technique using the mutually different codes, thereby generating respective received signals;

a threshold value changing section for updating and sequentially generating threshold values in accordance with an instruction;

first and second interference canceling sections that are connected to the first and second receivers, the canceling sections despreading the received signals with a code that has been used to spread any of the ultrasonic waves other than the desired one every time the threshold value is updated, thereby generating at least one despread signal;

extracting a signal, of which the amplitude is equal to or greater than a threshold value, from the despread signal using the threshold value, thereby generating an interference signal;

spreading the interference signal with the code that has been used to spread the ultrasonic wave other than the desired one and then removing the interference signal from the received signals, thereby generating received signals, from which the interference signal has been removed;

despreading the received signals, from which the interference signal has been removed, with the code of the desired ultrasonic wave, thereby generating despread received signals, from which the interference signal has been removed;

a correlating section for calculating a maximum correlation value between the despread received signals, which have been generated by the first and second interference canceling sections and from which the interference signal has been removed, for the respective threshold values;

a correlation peak value determining section for calculating a difference between the maximum correlation value and its previous value and instructing the threshold value changing section to select the threshold value if the difference is equal to or smaller than a predetermined value and to update the threshold value if the difference is greater than the predetermined value; and

a distance/azimuth calculating section for calculating at least one of the propagation distance and the propagation azimuth of the desired ultrasonic wave by the amount of time it has taken for the despread received signals, which are associated with the threshold value selected and from which the interference signal has been removed, to reach the first and second receivers.

14. The ultrasonic measuring apparatus of claim 13, wherein the correlation peak value determining section instructs the threshold value changing section to change the threshold values according to the difference between the maximum correlation value and its previous value.