JP2852196B2 - Underwater acoustic signal direction calculator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an underwater acoustic signal azimuth calculation apparatus, and more particularly to an OMNI having uniform directivity in all directions.
A combination of a hydrophone, an NS hydrophone having a maximum sensitivity axis of eight-shaped directivity in the north-south direction, and an EW hydrophone having a maximum sensitivity axis of eight-shaped directivity in the east-west direction, and using the hydrophone in combination with the target The present invention relates to an underwater acoustic signal azimuth calculation device that calculates the azimuth of arrival of a target signal captured by a directional sonobuoy for obtaining the azimuth of a sound.

[0002]

2. Description of the Related Art As shown in FIG. 2A, this kind of conventional underwater acoustic signal azimuth calculating apparatus has a uniform OMNI in all directions.
An OMNI hydrophone as a first hydrophone having a directivity pattern PI and outputting a first reception signal;
As shown in FIG. 2B, the second direction having the maximum sensitivity axis of the NS directivity pattern P2 having a figure-of-eight directivity in the north-south direction of the magnetic direction.
NS as a second hydrophone that outputs a received signal of
A hydrophone and a third hydrophone that has a maximum sensitivity axis of an EW directivity pattern P3 having a figure-eight pattern in the east-west direction of the magnetic direction as shown in FIG. 2C and outputs a third reception signal. Utilizing a directional sonobuoy including an EW hydrophone as the first, a first reception signal (hereinafter, referred to as an OMNI reception signal) received by the OMNI hydrophone and a second reception signal (hereinafter, NS) received by the NS hydrophone A received signal) and a third received signal (hereinafter, referred to as an EW signal) received by the EW hydrophone, and the arrival direction of the target signal is calculated based on the three received inputs.

[0003] The basics of azimuth determination will be described with reference to FIG.

That is, for the same target T, the NS directivity pattern P2 and the EW directivity pattern P3 share a common target T.
Are received via the directivity of the figure 8 which is orthogonal to each other, so that the amplitude ratio of the two inputs corresponds to the direction of arrival, and by determining the existence quadrant of this direction of arrival, the magnetic north is set to the 0 degree direction. The direction of arrival in rectangular coordinates can be determined. The coordinates of the arrival direction are determined by the 0MNI shown in FIG.
The directivity pattern P1 is used as a reference pattern, and the solid lines shown in FIGS. 2B and 2C are in phase with the reference pattern and the dotted lines are out of phase, and are obtained from these phase relationships.

FIG. 3 is a block diagram of a conventional underwater acoustic signal azimuth calculating apparatus. The OMNI received signal (S _OM ) 101, NS received signal (S _NS ) 102 and EW received signal (S _EW ) 103 are inputted. FFT (Fast Fourier)
Transform), an FFT circuit 4 for analyzing the frequency, a quadrant judging circuit 5 for judging the quadrant of the arrival direction of the target signal based on the phase relationship between the S _NS 102 and the S _EW 103 with respect to the S _OM 101, and S _NS 102 and S S _EW 103
And a azimuth calculating circuit 6 for calculating the azimuth of arrival of the target signal based on the amplitude information of the target signal and the determination quadrant of the quadrant determination circuit 3.

[0006] The FFT circuit 4 includes S _OM 101, S _NS 102
And _SEW 103, perform a frequency analysis by Fourier transform, and convert a signal having temporal continuity at a constant frequency from the real component Re and the complex component Im of the target signal to the amplitude spectrum A and the phase spectrum P of the target signal. And outputs them to the azimuth calculation circuit 6 and the quadrant determination circuit 5, respectively.

The amplitude spectrum A and the phase spectrum P for the target signal are obtained by the following equations (1) and (2), respectively. A = (Re ² + Im ² ) ^1/2 (1) P = tan ⁻¹ (Re / Im) (2) In the quadrant determination circuit 5, the OMN output from the FFT circuit 4
Phase spectrum P _OM of each received signal of I, NS and EW
OMN upon receiving 401, P _NS 402 and P _EN 403
The quadrant of the azimuth of arrival of the target signal is determined based on the phase relationship between the I, NS, and EW received signals, and the result of the determination is output to the azimuth calculation circuit 6 as a quadrant output Q501. Specifically, this quadrant output Q501 designates 0 degrees, 90 degrees, 180 degrees, and 270 degrees, which are the start angles of the first, second, third, and fourth quadrants.

As is apparent from FIG. 2, the quadrant designated by the quadrant output Q501 is the first to fourth quadrants shown in the following (1) to (4), that is, (1) _PNS 402 and _PEW 403, Is also in phase with P _OM 401, Q 501 is 0 degree in the first quadrant, and (2) Q 501 is 9 when P _NS 402 is in phase opposite to P _OM 401 and P _EW 403 is in phase with P _OM 401.
When the second quadrant is at 0 degree, (3) when both P _NS 402 and P _EW 403 are out of phase with P _OM 401, Q501 is at 180 degree in the third quadrant, and (4) P _NS 402 is _equal to P _OM 401. When the phase is the same and P _EW 403 is out of phase with P _OM 401, Q 501 is 2
Specify the fourth quadrant at 70 degrees.

The azimuth calculation circuit 6 includes a quadrant output Q501 and F
Receiving the amplitude spectra A _NS 404 and A _EW 405 of the NS reception signal and the EW reception signal output from the FT circuit 4, the following equation (3) is executed to calculate the arrival direction B of the target signal. B = Q + tan ^-1 (A _EW / A _NS ) (3)

This conventional underwater acoustic signal direction calculation device targets a target signal having a constant frequency and time continuity, and employs a Fourier transform for frequency analysis. The spectrum can be obtained by storing the phase information of each of the OMNI reception signal, NS reception signal, and EW reception signal of the directional sonobuoy as it is, whereby the arrival of the signal necessary for calculating the arrival direction of the target signal can be obtained. The correct judgment of the quadrant could be made.

However, the conventional underwater acoustic signal compass
Signal required for calculating the direction of arrival
Ignore or classify ambient noise when long duration reception is possible.
It is possible to separate. For example, as shown in FIG.
And the time length of observation data is T.
At the data amplitude As, almost symmetrically around the time t ₀
And cloth, or past the previous position noise length of time -Tn and the present time t ₀
Noise amplitude An exists between the subsequent posterior time length + Tn
In the case, the data amplitude of the observation data to be set to the observation time T
The average of the power of As × Ts and the power of the noise amplitude An × 2Tn
Can be distinguished when the difference from the average is large, that is, when the S / N is large.
But the duration Ts for the observation time length T
If the target signal is short, it is difficult to distinguish it from ambient noise because it is averaged with the time length corresponding to the length of the data extraction section of the Fourier transform, making it impossible to calculate the azimuth of the target signal. was there.

An object of the present invention is to solve the above-mentioned problems,
It is an object of the present invention to provide an underwater acoustic signal azimuth calculation device capable of calculating an azimuth even with a target signal having a short duration.

The underwater acoustic signal azimuth calculating apparatus according to the present invention comprises a first hydrophone having a uniform directivity in all directions and a second hydrophone having a maximum sensitivity axis having a directivity figure of eight in the north-south direction. And a third hydrophone having an eight-shaped directivity maximum sensitivity axis in the east-west direction and an underwater acoustic signal azimuth calculation device for calculating the azimuth of arrival of a target signal included in a reception signal acquired by a directional sonopuy. , The first
And an eye included in each of the second and third received signals.
At time Δt from the current time to distinguish between the target signal and the surrounding noise
Between the previous received signal and Δt (same as Δt above)
J) To take multiple correlations with the received signal after time
A first cross-correlation coefficient between a first received signal received by the first hydrophone and a second received signal received by the second hydrophone after the target signal is specified by And a second cross-correlation coefficient between the first received signal and the third received signal received by the third hydrophone are obtained, and the first and second cross-correlation coefficients are subjected to frequency analysis to obtain respective amplitudes. A cross-correlation processing circuit that outputs a spectrum and a transfer spectrum; a quadrant determination circuit that determines a quadrant in an arrival direction of the target signal based on the phase spectrum output by the cross-correlation processing circuit; An arrival direction calculation circuit for calculating an arrival direction of the target signal based on the output amplitude spectrum and a quadrant judgment result of the quadrant judgment circuit.

Further, in the underwater acoustic azimuth calculating apparatus according to the present invention, the quadrant judging circuit may determine whether the phase spectra of the first and second cross-correlations are in phase but opposite in phase. The quadrature including the azimuth of the target signal is determined by using a combination of the cross-correlation phase spectrum of one and the phase existence quadrant as a determination condition.

Further, the underwater acoustic azimuth calculation device of the present invention is
The azimuth calculation circuit determines an arrival azimuth of the target signal based on an angle in a quadrant expressed based on a ratio of amplitude spectra of the first and second cross-correlations and a quadrant judgment result of the quadrant judgment circuit. Having.

[0015]

Next, the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of one embodiment of the present invention. The underwater acoustic signal direction calculation device shown in FIG. 1 receives the OMNI, NS, and EW received signals, takes a cross-correlation between the OMNI received signal and the NS and EW received signals, and then performs a frequency analysis by Fourier transform of the cross-correlated signal. A quadrature determination circuit 2 for inputting a phase spectrum of a cross-correlation signal output from the cross-correlation processing circuit 1 to determine a quadrant of an arrival direction of a target signal, and an output of the cross-correlation processing circuit 1 And a direction calculation circuit 3 for determining the direction of arrival of the target signal based on the amplitude spectrum of the cross-correlation signal and the quadrant information output from the quadrant determination circuit 2.

The cross-correlation processing circuit 1 has the following (4),
S of the OMNI reception signal represented by the equations (5) and (6)
_OM 101, S _NS 102 of the _NS reception signal and S _EW 103 of the EW reception signal are input, and the cross-correlation between S _OM 101 and SNS 102 and between S _OM 101 and S _EW 103 is obtained. Then, the cross-correlation result is subjected to Fourier transform. Perform frequency analysis.

If the Fourier transform is applied to a target signal having a short duration as it is, the target signal is averaged with a time length corresponding to the length of the data cutout section, so that it becomes difficult to distinguish it from ambient noise. Although it is conceivable to apply autocorrelation processing to the received target signal as preprocessing, the phase information of the target signal is lost in this case. Are remarkably improved to avoid the above-mentioned problem.
Here, means for avoiding the problem implemented in the present embodiment is shown in FIG.
The description will be made stably with reference to FIG. As described above, a certain time t
How to extract the time length Ts of observation data from ₀
In order to do this sensibly, rise and fall the observation data.
A slightly wider Ts ≒ T is optimal, while FIG.
As shown in (b), when the front position is symmetric with respect to time t ₀
Time -t _1, -t _2, -t ₃ and the rear position of the time + t _1, +
By taking the autocorrelation with t ₂ and + t ₃ respectively,
The cutout time is ideally the center of the observation data time length Ts
Definition autocorrelation related to the target signal when there is a t ₀ to
Is obtained. Section in which t ₀ deviates from the center of time length Ts
Between the noise component at −t ₄ and the data at + t ₂
The autocorrelation is slightly shifted in the process
However, the cut-out time (corresponding to the observation time T) must be reduced.
Makes clear the distinction between ambient noise and the target signal.
Can be. Thus, first, each OMN, NS, EW signal
After each autocorrelation, the OMN and NS signals and
And OMN and EW signal are correlated. That is, equation (9)
Equations (12) indicate that the OMN1 received signal 101, NS
The same signal included in the reception signal 102 and the EW reception signal 103
After extracting the target signal, the mutual amplitude spectrum
_{A 0 - N, A 0 -} E and the phase spectrum P ₀ - _N, P ₀ -
₅ cross-correlation signals are calculated.

S _OM = Asin ωt (4) S _NS = Asin (ωt + θ ₁ ) cosB (5) S _EW = Asin (ωt + θ ₂ ) sinB (6) The above (4) to (6) The equation shows that in the first quadrant shown in FIG. 2, a target T exists in a direction of B degrees east of magnetic north, and A is the intensity of the target signal and S _NS 102 with reference to the phase of S _OM 101.
And the phase difference between S _EW 103 and θ _EW 103 are θ ₁ and θ ₂ , respectively.

S _OM 101 and S _NS 102, S _OM 101 and S
Cross-correlation with _EW 103 (S _ON and S _OE are given by the following equations (7) and (8), respectively): S _ON = A ₂ cosB sin (ωt−ωτ / 2) sin (ωt + ωt / 2 + θ ₁ ) (7) S _OE = A ₂ sinB sin (ωt−ωτ / 2) sin (ωt + ωτ / 2 + θ ₂ ) (8) Cross-correlation S _ON and S _OE amplitude spectrum A _ON and A _OE and phase spectrum P _ON and P _OE are expressed by the following equations (9) and (10), and equations (11) and (12), respectively.

[0020]

[0021]

[0022]

[0023]

The symbol-in the expressions (9) to (12) indicates an averaging process.

The amplitude spectrum A _ON 10 of the cross-correlation result
6 is supplied to the azimuth calculation circuit 3 with A _OE 107, and the phase spectra P _ON 104 and P _OE 105 are supplied to the quadrant determination circuit 2 respectively.

In the quadrant determination circuit 2, the cross-correlation processing circuit 1
, The phase spectrum P _ON 104 of the cross-correlation signal between S _OM 101 and S _NS 102 and the phase spectrum P _OE 105 of the cross-correlation signal between S _OM 101 and S _EW 103 are input to P _ON 104 and P _OE. The phase relationship with 105 is determined,
The azimuth calculation circuit 3 uses the determination result as a quadrant output Q201.
Output to The quadrants designated by the quadrant output Q201 are the following four types (A), (B), (C) and (D).

That is, (A) P _ON 104 and P _OE 1
05 is in phase and P _ON 104 is -π / 2 ≦ P
_{When ON} ≦ π / 2, Q201 = 0 degree designates the first quadrant. (B) P _ON 104 and P _OE 105 are in opposite phases, and P _ON 104 is π / 2 <P _ON <3. / 2π when Q201 = 90 degrees specifies the second quadrant,
(C) P _ON 104 and P _OE 105 are in phase and P
_{When ON} 104 is in the range of π / 2 <P _ON <3 / 2π, specify the third quadrant with Q201 = 180 degrees, (D) P _ON
104 and P _OE 105 are in opposite phase and P _ON 104
Is in the range of -π / 2 ≦ P _ON ≦ π / 2 when Q201
= Specify the fourth quadrant at 270 degrees.

The basic background of the above-described quadrant determination by (A) to (D) is that the concept of quadrant determination described with reference to FIG. 2 is applied to a cross-correlation area.
The OMNI reception signal captured by the OMNI directivity pattern P1 and the NS reception signal and the EW reception signal captured by the NS directivity pattern P2 and the EW directivity pattern P3 are in the same polarity state. 1
Corresponds to the case of a quadrant.

Based on the quadrant output Q201 output from the quadrant determination circuit 2 and the amplitude spectra A _ON 106 and A _OE 107 output from the cross-correlation processing circuit 1, the azimuth calculation circuit 3 arrives at the target by the following equation (13). The direction B is calculated. B = Q + tan ^-1 (A0-E / AO-N) (13) In this way, even for a signal having a short duration, the noise immunity can be remarkably improved by the cross-correlation, and the direction of arrival can be reliably grasped. .

[0030]

As described above, according to the present invention, the azimuth of a target signal received by a directional sonobuoy having omnidirectional directivity and two figure-of-eight directivities having maximum sensitivity directions in east-west and north-south directions. Is calculated, the target signal of the target signal is calculated based on the amplitude spectrum and the phase spectrum obtained by the Fourier transform in which the cross-correlation between the received signal based on the omnidirectional directivity and the received signals based on the two figure-shaped directivities is preprocessed. By obtaining the azimuth, there is an effect that a target signal having a short duration can be remarkably improved in a noise ratio and an accurate azimuth can be determined.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 shows OMNI directivity (a), NS of directivity sonobuoy
It is a figure which shows directivity (b) and EW directivity (c).

FIG. 3 is a configuration diagram of a conventional underwater acoustic signal direction calculation device.

FIG. 4 is an explanatory diagram for explaining a conventional technique and an embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 cross-correlation processing circuit 2 quadrant determination circuit 3 azimuth calculation circuit 4 FFT circuit 5 quadrant determination circuit 6 azimuth calculation circuit 7 frequency analysis circuit 8 autocorrelation circuit 9 FFT circuit

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasushi Sasaki 2-4-16-203 Oyamaguchi, Shirai-machi, Inba-gun, Chiba Prefecture (72) Inventor Masanori Abe 5-7-1 Shiba, Minato-ku, Tokyo NEC Corporation In-company (56) References JP-A-6-201811 (JP, A) JP-A-5-87903 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01S 3/80- 3/86 G01S 5/18-5/30 G01S 7/52-7/64 G01S 15/00-15/96

Claims (3)

(57) [Claims] 1. A first hydrophone having a uniform directivity in all directions, a second hydrophone having a maximum sensitivity axis having a directivity of eight in the north-south direction, and a directivity of eight in the east-west direction. Underwater acoustic signal azimuth calculating apparatus for calculating the azimuth of arrival of a target signal included in a received signal obtained by a directional sonobuoy having a third hydtophone having a maximum sensitivity axis of the first hydrophone A first cross-correlation between a first received signal and a second received signal received by the second hydrophone; and a first cross-correlation between the first received signal and the third received signal.
Cross-correlation processing for obtaining a second cross-correlation with a third received signal received by the hydrophone of the first embodiment, frequency-analyzing the results of the first and second cross-correlations, and outputting an amplitude spectrum and a phase spectrum, respectively. A quadrature determination circuit that determines a quadrant of an arrival direction of the target signal based on the phase spectrum output from the cross-correlation processing circuit; and a quadrature determination circuit that outputs the amplitude spectrum and the quadrant determination circuit output from the cross-correlation processing circuit. A direction-of-arrival calculation circuit for calculating the direction of arrival of the target signal based on the quadrant determination result, wherein the first N received signal SOM is SOM = Asin ωt and the second received signal SNS is SNS = Asin (ωt + θ1) c
osB The third received signal SEW is calculated as SEW = Asin (ωt + θ2) s
inB where A is the intensity of the target signal and the direction of B degrees from magnetic north to east
It is assumed that there is a target in SNS and SNS based on the phase of SOM.
Each θ1 a phase difference of SEW and, .theta.2, when the said first cross-correlation SO-N is SO-N = A2 cosB s
in (ωt−ωτ / 2) sin (ωt + ωt / 2 + θ1
), The second cross-correlation SO-E is: SO-E = A2 sinB s
in (ωt−ωτ / 2) sin (ωt + ωτ / 2 + θ2
A) Underwater acoustic signal azimuth calculation device characterized by being obtained by: 2. The phase determination circuit according to claim 1, wherein the quadrature determination circuit determines a phase relationship between whether the phase spectra of the first and second cross-correlations are in phase but opposite phases, and a phase of the phase spectrum of the first cross-correlation. 2. The underwater acoustic signal azimuth calculation device according to claim 1, wherein a quadrant including the azimuth of the target signal is determined using a combination with a presence quadrant as a determination condition. 3. The arrival of the target signal based on an angle in a quadrant expressed based on a ratio of amplitude spectra of the first and second cross-correlations and a quadrant judgment result of the quadrant judging circuit. The azimuth calculating device according to claim 1, wherein the azimuth is determined.