JP5371038B2 - Propagation time measuring device, propagation time measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus and a method for measuring a propagation time, for carrying out a high-precise measurement by using a small number of wave transmitting/receiving elements at a small count of measurement frequencies, in measuring the propagation time of a wave motion. <P>SOLUTION: The apparatus includes: a vector generating section for generating a vector V3 by adding vectors V2 to each other on the basis of a Kronecker product of an Nth orthogonal matrix U1 and a number, N, of vectors V1 having a length of M; a modulating section for carrying out a modulating operation on the basis of the vector V3 and a carrier wave; a demodulating section for generating a vector V4 by demodulating a signal arising when an output of the modulating section is propagated through a propagation path; a vector calculating section for calculating a vector V5 on the basis of a multiplication of the vector M3 by a matrix U3, by using the matrix U3 obtained by a Kronecker product of an Nth orthogonal matrix U2 and an Mth unit matrix; a correlation operating section for deriving a vector V6 by executing a correlation operation between the vector V5 and the vector V1; an adding section for calculating a vector V7 by adding the vectors V6 to each other; and a detecting section for detecting the propagation time on the basis of a peak in the vector V7. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a propagation time measuring apparatus and a propagation time measuring method for measuring the propagation time of a wave.

  The basic principle of ultrasonic propagation time measurement is the use of the straightness and constant speed of the ultrasonic wave. The time required for the pulse ultrasonic wave transmitted by the transmitter to be reflected by the object and received by the receiver is calculated. taking measurement. For example, there is a technique for measuring the propagation time by performing a cross-correlation process between a transmission signal and a reception signal using an M-sequence signal. (For example, refer nonpatent literature 1 and nonpatent literature 2). In this technique, the S / N ratio is improved by using the autocorrelation characteristics of the M-sequence signal as compared with a method using a chirp wave or the like.

T. Tanzawa, N. Kiyohiro, S. Kotani, H. Mori, "The ultrasonic range finder for outdoor mobile robots," International Conference on Intelligent Robots and Systems-Volume 3, pp. 3368, 1995. T. Yamamoto, R. Kijima, "Ultrasonic distance measurement system using Direct Sequence Spread Spectrum," Proceedings of the Virtual Reality Society of Japan Annual Conference (CD-ROM), pp. 3B3-3, 2006.

  However, in order to realize high-accuracy measurement and long-distance measurement, in order to reduce the influence of noise, averaging by repeated measurement of signals and simultaneous multipoint measurement by many transducers are necessary.

  The present invention has been made to solve the above-described problems, and in the measurement of the propagation time of a wave, a propagation time measurement apparatus and a propagation time measurement that realize high-precision measurement with a small number of transducers and a small number of measurements. It aims to provide a method.

  In order to solve the above-described problem, one aspect of the present invention is a propagation time measurement apparatus that measures a propagation time of a wave, and is a predetermined vector having a length M of N (N is an integer of 2 or more) different from each other. N vectors V2 based on the Kronecker product of V1 and each row vector of the Nth-order orthogonal matrix U1 are added together to generate a vector V3, and modulation is performed based on the vector V3 and the carrier wave. A modulation unit to perform, a demodulation unit that demodulates a signal whose output from the modulation unit has propagated through the propagation path to be a vector V4, each row vector of the Nth-order orthogonal matrix U2 based on the orthogonal matrix U1, and an Mth-order unit matrix A vector calculation unit that calculates N vectors V5 based on multiplication of the vector M3 and the matrix U3 using N matrices U3 obtained by the Kronecker product, and each of the N vectors V5 and N vectors A correlation calculation unit that calculates N vectors V6 by performing a correlation calculation with each of 1, a summation unit that adds N vectors V6 together to calculate one vector V7, and a peak in the vector V7 And a detection unit for detecting the propagation time based on

  Another aspect of the present invention is a propagation time measurement method for measuring the propagation time of a wave, which is different from N (N is an integer of 2 or more) predetermined vectors V1 of length M and N-order orthogonality. N vectors V2 based on the Kronecker product with each row vector of the matrix U1 are added to generate one vector V3, and modulation is performed based on the vector V3 and the carrier wave, and the result of the modulation propagates through the propagation path The signal M is demodulated into a vector V4, and N matrices U3 obtained by a Kronecker product of each row vector of the Nth-order orthogonal matrix U2 and the Mth-order unit matrix based on the orthogonal matrix U1 are used. N vectors V5 are calculated based on the multiplication of N, and the N vectors V6 are calculated by performing a correlation operation between each of the N vectors V5 and each of the N vectors V1, and the N vectors V6 same An addition unit for calculating a single vector V7 by adding, to execute detecting a propagation time on the basis of the peaks in the vector V7.

  According to the present invention, high-precision measurement can be realized with a small number of transducers and a small number of measurements in the measurement of wave propagation time.

It is a block diagram which shows the structure of an ultrasonic propagation time measuring apparatus. It is a block diagram which shows the structure of a modulation part. It is a block diagram which shows the structure of a demodulation part. It is a wave form diagram which shows an example of the measurement result by an ultrasonic propagation time measuring apparatus.

  Embodiments of the present invention will be described below with reference to the drawings.

  In the following embodiments, an ultrasonic propagation time measuring device to which the propagation time measuring device of the present invention is applied will be described.

  The ultrasonic wave propagation time measurement apparatus according to the present embodiment performs super multidimensional signal superimposition that superimposes N (N is an integer of 2 or more) signals on one signal, thereby performing a pair of elements and a single transmission / reception. Then, N times of sound wave propagation time is measured.

  In the present embodiment, a ZCZ (Zero Correlation Zone) sequence is used as a measurement signal, and an IDFT (inverse discrete Fourier transform) matrix is used as an orthogonal sequence for chip interleaving processing.

  As the measurement signal, a sequence having excellent autocorrelation characteristics such as an M sequence (maximal length sequences), a Gold sequence, or a completely complementary sequence may be used. Here, the series having excellent autocorrelation characteristics is, for example, a series in which the ratio of the level other than the peak to the peak level of the autocorrelation function is a predetermined ratio or less. An IDFT (discrete Fourier transform) matrix, a DFT matrix, a unitary matrix, a complete complementary sequence, or the like may be used as an orthogonal sequence for predetermined chip interleaving processing.

  The configuration of the ultrasonic propagation time measuring apparatus in the present embodiment will be described below.

  FIG. 1 is a block diagram showing the configuration of the ultrasonic propagation time measuring apparatus 1. The ultrasonic propagation time measuring apparatus 1 in this embodiment includes a modulation unit 2, a transmitter 3 (Transmitter), a receiver 4 (Receiver), and a demodulation unit 5.

  FIG. 2 is a block diagram illustrating a configuration of the modulation unit 2. The modulation unit 2 includes a ZCZ sequence output unit 11 (ZCZ Sequences), an IDFT matrix output unit 12 (IDFT Matrix), a multiplication unit 13 (Kronecker Product), an addition unit 14, a guard interval addition unit 15 (Add Guard Interval), and orthogonal modulation. Part 16 (Quadrature modulation).

  FIG. 3 is a block diagram showing the configuration of the demodulator 5. The demodulation unit 5 includes a quadrature detection unit 22 (Quadrature detection), a matched filter 23 (Matched Filter), a ZCZ sequence output unit 24 (ZCZ Sequences), N correlation calculation units 25 (Correlation), an averaging calculation unit 26, a propagation It has a time detector 27 (Propagation Time Detection).

  The ultrasonic propagation time measurement process by the ultrasonic propagation time measurement apparatus 1 will be described below.

The ZCZ sequence output unit 11 outputs a vector X _i (i = 1, 2,... N) of a ZCZ sequence having a length M (M is an integer of 2 or more) stored in advance. The IDFT matrix output unit 11 outputs a vector f _i (i = 1, 2,... N) of each row of an N-th order IDFT matrix stored in advance.

Next, the multiplication unit 13 calculates a vector s _i (i = 1, 2,... N) of length MN that is a Kronecker product of f _i and x _i . By the processing of the multiplication unit 13, the spectrum of x _i is spread. s _i is expressed by the following equation (1).

That is, s _i is represented by a Kronecker product of f _i and x _i .

Next, the adding unit 14 multiplexes by adding s _i with _i ranging from 1 to N to obtain a vector u of length MN.

  Next, the guard interval adding unit 15 adds a guard interval (cyclic prefix) to u and sets it to u ′, thereby performing pseudo-periodicization having pseudo-periodicity.

  Next, the quadrature modulation unit 16 multiplies the carrier part cos (ωt) by using the real part of u ′ as the I channel and multiplies the carrier sin (ωt) by using the imaginary part of u ′ as the Q channel, and multiplies the I channel. The result and the multiplication result of the Q channel are added.

  Next, the transmitter 3 converts the electrical signal output from the modulation unit 2 into an ultrasonic wave and transmits it to the propagation path 6. Here, the propagation path 6 is assumed to be a multipath environment. Next, the wave receiver 4 converts the ultrasonic wave received from the propagation path 6 into an electric signal and inputs the electric signal to the demodulator 5.

  Next, the quadrature detection unit 22 removes unnecessary frequency components from the output of the receiver 4 by the BPF and distributes them to two. Next, the quadrature detection unit 22 multiplies the distributed one by a carrier wave cos (ωt), removes an unnecessary high-frequency component by the LPF to make an I channel, and multiplies the other distributed by a carrier wave sin (ωt) to obtain an LPF. Thus, an unnecessary high-frequency component is removed to obtain a Q channel, and a vector r having a length MN in which the I channel is a real part and the Q channel is an imaginary part is obtained.

The matched filter 23 is a matched filter of N row vectors in a matrix Z _i of N rows and MN columns stored in advance, and a vector obtained by multiplying r by Z _i (i = 1, 2,... N). y _i 'is calculated, and a vector having a length M at the center of y _i ' is defined as y _i . N order DFT matrix G _N at i-th row vector of the g _i (i = 1, 2, ... N) and when, Z _i, using the g _i and M order unit matrix I _M, the following equation It is represented by (2).

That is, Z _i is represented by a Kronecker product of g _i and I _M.

According to the matched filter 23, the spectrum of the received signal is despread and separated into N signals that have been multiplexed. That is, N length M vectors y _{i in} which the impulse response H of the propagation path 6 is superimposed on the N length M vectors x _i are calculated. This two x _i where i is different, but have the property that the periodic cross-correlation is zero at all shifts.

Next, similarly to the ZCZ sequence output unit 11, the ZCZ sequence output unit 24 outputs a previously stored ZCZ sequence vector x _i (i = 1, 2,... N) of length M.

Next, the correlation calculation unit 25 performs a correlation calculation between y _i and x _i to obtain a periodic autocorrelation c _i (i = 1, 2,... N). Here, c _i corresponds to the impulse response H of the propagation path 6.

Next, the averaging calculation unit 26 averages ci by adding _i between 1 and N, and outputs the averaged result as a vector d indicating the impulse response of the propagation path 6.

  Next, the propagation time detector 27 detects the peak of the direct wave from the waveform of d, and calculates the propagation time that is the delay time of the direct wave.

  The separation accuracy (time resolution) of the direct wave and the reflected wave in the measurement result is determined by the number of bits transmitted per unit time.

FIG. 4 is a waveform diagram showing an example of a measurement result obtained by the ultrasonic propagation time measuring apparatus 1. This figure shows the waveforms of c ₁ , c ₂ , c _N , and d in order from the top. In this figure, the horizontal axis represents the sample number, and the vertical axis represents the relative amplitude with the peak level being 1.

c ₁ , c ₂ ,. . . c _N is a waveform indicating an impulse response of the same propagation path 6, and includes a direct wave peak, a reflected wave peak, and a noise component, respectively. Since the noise component has randomness, c ₁ , c ₂ ,. . . noise component in c _N are different from each other. On the other hand, d is c ₁ , c ₂ ,. . . Each sample c _N are averaged waveform. The propagation time Δt is detected from the peak of the direct wave at d. Therefore, the influence of the noise component in d is reduced. For example, assuming that N is 64 as a value that allows sufficient simulation and actual measurement, the SN ratio can be expected to be improved by about 10 dB by the averaging of the present embodiment when compared with the measurement result when the averaging is not performed. .

c ₁ , c ₂ ,. . . c _N are transmitted from the transmitter 3 at the same time and simultaneously reach the receiver 4 through the same multipath propagation path 6, so that c ₁ , c ₂ ,. . . c _N are fully synchronized with each other. Although a synchronization error may occur in the method of performing repetitive measurement, no synchronization error occurs in this embodiment.

  In underwater acoustic measurement, precise measurement of sound wave propagation time is performed using a large number of arrays mainly in the deep sea area. This is because it is easy to separate multipaths and it is necessary to install many devices to ensure accuracy. According to the system of the present embodiment, it is possible to perform precise acoustic measurement in any environment with a simple measurement system. Further, the system of this embodiment can be applied to the field of acoustic communication. For example, it can be used for channel estimation for channel equalization.

  According to the present embodiment, N times of sound wave propagation time can be measured by a pair of elements and one transmission / reception. Moreover, according to this Embodiment, the temperature, the flow velocity, etc. in every place can be measured accurately. Thereby, this Embodiment can contribute to elucidation of the complicated flow field in an estuary etc., the temperature in the air, the wind direction, the flow field in a multiphase flow, etc.

  Note that the ZCZ sequence output units 11 and 24 may generate a ZCZ sequence from the calculation formula. The IDFT matrix output unit 12 may generate an IDFT matrix from the calculation formula. The modulation unit 2 may be configured to output a prestored waveform at any output of the multiplication unit 13, the addition unit 14, the guard interval addition unit 15, and the quadrature modulation unit 16.

  Each function of the ultrasonic propagation time measuring apparatus may be realized by hardware or software. When implemented by software, the ultrasonic wave propagation time measurement apparatus has a processor such as a CPU (Central Processing Unit) and a DSP (Digital Signal Processor) and a storage unit, and the processor executes a program stored in the storage unit. By doing so, each function of the ultrasonic propagation time measuring device is realized.

  In this embodiment, an ultrasonic wave is used as a wave to be propagated, but a sound wave, vibration, light, electromagnetic wave, or the like in another band may be used.

  The vector generation unit corresponds to the ZCZ sequence output unit 11, the IDFT matrix output unit 12, the multiplication unit 13, the addition unit 14, and the guard interval addition unit 15 in the embodiment. The modulation unit corresponds to the quadrature modulation unit 16 in the embodiment. The demodulation unit corresponds to the quadrature detection unit 22 in the embodiment. The vector calculation unit corresponds to the matched filter 23 in the embodiment. The adder corresponds to the averaging calculator 26 in the embodiment. The detection unit corresponds to the propagation time detection unit 27 in the embodiment.

The vector V1 corresponds to x _i in the embodiment. The orthogonal matrix U1 corresponds to the Nth-order IDFT matrix (N row vectors f _i ) in the embodiment. The vector V2 corresponds to s _i in the embodiment. The vector V3 corresponds to u in the embodiment. The vector V4 corresponds to r in the embodiment. The orthogonal matrix U2 corresponds to the Nth-order DFT matrix (N row vectors g _i ) in the embodiment. The matrix U3 corresponds to Z _i in the embodiment. The vector V5 corresponds to y _i in the embodiment. The vector V6 corresponds to c _i in the embodiment. The vector V7 corresponds to d in the embodiment.

  The present invention can be implemented in various other forms without departing from the spirit or main features thereof. Therefore, the above-described embodiment is merely an example in all respects and should not be interpreted in a limited manner. The scope of the present invention is shown by the scope of claims, and is not restricted by the text of the specification. Moreover, all modifications, various improvements, substitutions and modifications belonging to the equivalent scope of the claims are all within the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Ultrasonic propagation time measuring apparatus 2 Modulator 3 Transmitter 4 Receiver 5 Demodulator 11 ZCZ sequence output unit 12 IDFT matrix output unit 13 Multiplier 14 Adder 15 Guard interval addition unit 16 Orthogonal modulator 22 Orthogonal detector 23 Matched Filter 24 ZCZ sequence output unit 25 Correlation calculation unit 26 Averaging calculation unit 27 Propagation time detection unit

Claims (6)

A propagation time measuring device for measuring the propagation time of a wave,
The elements of N vectors V2 based on the Kronecker product of N different (N is an integer of 2 or more) predetermined vector V1 of length M and each row vector of Nth-order orthogonal matrix U1 are added, A vector generation unit for generating one vector V3;
A modulation unit that performs modulation based on the vector V3 and the carrier wave;
A demodulating unit that demodulates a signal having an output of the modulating unit propagated through a propagation path into a vector V4;
Using N matrices U3 obtained by the Kronecker product of each row vector of the Nth-order orthogonal matrix U2 based on the orthogonal matrix U1 and the Mth-order unit matrix, N vectors V5 based on the multiplication of the vector M3 and the matrix U3 A vector calculation unit for calculating
A correlation calculation unit that performs a correlation calculation between each of the N vectors V5 and each of the N vectors V1 to calculate N vectors V6;
An adder that adds elements of N vectors V6 to calculate one vector V7;
A propagation time measurement device comprising: a detection unit that detects propagation time based on a peak in vector V7. The vector V1 is a series in which the ratio of the level other than the peak to the peak level of the autocorrelation function is equal to or less than a predetermined ratio.
The propagation time measuring device according to claim 1. The vector V1 is one of a ZCZ series, an M series, a Gold series, and a completely complementary series.
The propagation time measuring device according to claim 2. The orthogonal matrix U1 is one of an inverse discrete Fourier transform matrix, a discrete Fourier matrix, a unitary matrix, and a complete complementary sequence,
The orthogonal matrix U2 is one of an inverse discrete Fourier transform matrix, a discrete Fourier matrix, a unitary matrix, and a complete complementary sequence.
The propagation time measuring device according to any one of claims 1 to 3. A vector V6 represents a waveform in which the autocorrelation function of the vector V1 and the impulse response of the propagation path are superimposed,
N vectors V6 are synchronized with each other,
The propagation time measuring device according to any one of claims 1 to 4. A propagation time measurement method for measuring the propagation time of a wave,
The elements of N vectors V2 based on the Kronecker product of N different (N is an integer of 2 or more) predetermined vector V1 of length M and each row vector of Nth-order orthogonal matrix U1 are added, Generate one vector V3,
Modulate based on vector V3 and carrier wave,
The signal whose modulation result has propagated through the propagation path is demodulated into a vector V4,
Using N matrices U3 obtained by the Kronecker product of each row vector of the Nth-order orthogonal matrix U2 based on the orthogonal matrix U1 and the Mth-order unit matrix, N vectors V5 based on the multiplication of the vector M3 and the matrix U3 To calculate
A correlation operation between each of the N vectors V5 and each of the N vectors V1 is performed to calculate N vectors V6;
By adding elements of the number N of vectors V6 calculates one vector V7,
Detecting the propagation time based on the peak in vector V7;
Propagation time measurement method to do that.

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