JPS6343714B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for calculating the direction of an underwater acoustic signal, and in particular, the underwater acoustic signal that has been propagated is divided into an x-axis direction signal and a y-axis direction signal and received by a sensor, and these x-axis components are A composite signal consisting of an orthogonal modulated wave obtained by orthogonally modulating the signal and the y-axis component signal with a carrier frequency and a carrier phase pilot for indicating the phase of the carrier frequency is transmitted to a remote processor. , relates to an azimuth calculation method for calculating the azimuth of an underwater acoustic signal based on the transmitted signal.

Generally, an underwater acoustic signal received by a sensor is divided into an x-axis direction signal and a y-axis direction signal, and the received signals are transmitted and processed by a processor located at a remote location. Calculate the direction from which the underwater acoustic signal propagated.

Below, underwater acoustic signals received by the sensor will be explained with reference to FIG.

FIG. 1 is a diagram for explaining an underwater acoustic signal in the present invention and the prior art. When an underwater acoustic signal a propagates from a direction forming an azimuth θ with the x-axis, the sensor detects an x-axis direction signal a _x and a y Axial signal a _y
and receive it separately.

The underwater acoustic signal a is simultaneously generated from multiple directions with different intensities and frequencies and is received by the sensor. Therefore, underwater acoustic signal a is received as a set of underwater acoustic signals a(1) to a(N), and has the relationship of equation (1) with K-th underwater acoustic signal a(K). .

a= _N 〓 ^K=1 a(K) …(1) Also, the x-axis direction signal a _x (K) of the underwater acoustic signal a(K),
For the y-axis direction signal a _y (K), the following equations (2) and (3) are used.
The relationship is as follows.

a _x = _N 〓 ^K=1 a _x (K) …(2) a _y = _N 〓 ^K=1 a _y (K) …(3) Now, the K-th underwater acoustic signal a(K) has a signal frequency of If ω _K , phase difference α _K , and intensity A _K are expressed as equation (4).

a _(K) = A _K sin (ω _K t + α _K … (4) If this underwater acoustic signal a _(K) propagates from the direction θ _K , its x-axis direction signal a _x(K) and y-axis direction signal a _y(K) are expressed by equations (5) and (6), respectively.

a _{x (K)} = A _K sin (ω _K t + α _K ) cosθ _K … (5) a _{y (K)} = A _K sin (ω _K t + α _K ) sin θ _K … (6) This x-axis direction signal a _x and The y-axis direction signal a _y is
When they are received separately by the sensor and the processor is located at a remote location, in order to transmit the x-axis direction signal a _x and the y-axis direction signal a _y from the sensor to the processor,
The sensor orthogonally modulates the x-axis direction signal a _x and the y-axis direction signal a _y at a carrier frequency ω to generate an orthogonally modulated wave S(t) shown in equation (7).

S(t)= _N 〓 ^K=1 S _K (t)...(7) Here, since the orthogonally modulated wave S _K (t) is orthogonally modulated, it becomes as shown in equation (8).

S _K (t) = a _{x (K)} cosωt−a _y(K) sinωt = A _K sin (ω _K t + α _K )・cos (ωt + θ _K ) …(8) The conventional method for calculating the direction of underwater acoustic signals is as follows: Along with the orthogonal modulated wave S(t) obtained as described above, a carrier phase pilot P(t) is used to confirm the phase information during demodulation, and a frequency pilot F is used to confirm the frequency information. Using (t),
These three signals are combined and sent from the sensor to the processor as a transmission composite signal b.

Here, the transmitted composite signal b is expressed as in equation (9), and the carrier phase pilot P(t) is
As in equation (10), the frequency pilot F(t) is expressed as in equation (11).

b=S(t)+P(t)+F(t)...(9) P(t)=Bcosωt...(10) F(t)=Ccos(ωt/2)...(11) Next, conventional underwater acoustics A method for calculating the direction of a signal will be explained with reference to the drawings.

FIG. 2 is a block diagram showing an example of a conventional method for calculating the direction of an underwater acoustic signal.

The transmission composite signal b transmitted from the sensor is sent to a transmission signal separation circuit 1 and a frequency conversion signal extraction circuit 2.
and are supplied in parallel.

This transmission signal separation circuit 1 is a circuit for removing the frequency pilot F(t) from the transmission composite signal b to obtain the transmission signal c shown in equation (12). contains filters.

c=S(t)+P(t)...(12) Moreover, the frequency conversion signal extraction circuit 2 extracts the first frequency conversion signal shown in equation (13) from the transmission composite signal b.
₁ and _{a second frequency conversion signal 2 shown} in equation (14) whose phase is shifted by 90 degrees from the first frequency conversion 1. , a phase shift circuit 5 , and a phase error removal circuit 6 .

₁ = cosωt...(13) ₂ = sinωt...(14) The transmitted transmission composite signal b is first supplied to the frequency pilot separation circuit 3 including a filter that allows only the frequency pilot F(t) to pass (15)
A frequency pilot d shown by the formula is created.

d=cos(ωt/2) (15) This frequency pilot d is multiplied by the multiplier circuit 4, and since a phase error occurs during multiplication, it becomes the multiplied wave _e1 shown in equation (15A).

e ₁ = cos (ωt +) ... (15A) This harmonic wave e ₁ is supplied to the phase shift circuit 5 and its phase is shifted by 90°, resulting in a phase shift signal e ₂ shown in equation (16).
becomes.

e ₂ = sin (ωt +) ... (16) Next, the transmission signal c, the harmonic e ₁ , and the phase shift signal
e ₂ is supplied to the phase error removal circuit 6 to eliminate the phase difference, and by determining the accurate frequency and phase of the carrier wave, the first frequency-converted signal ₁ and the second frequency-converted signal ₂ are obtained. .

The first frequency-converted signal ₁ and the second frequency-converted signal ₂ are supplied to a multiplier circuit 7, where they are multiplied by the transmission signal c, respectively, to produce the first demodulated signal g ₁ and ( The second demodulated signal _g2 shown in equation 18) is obtained.

g ₁ = {S(t)+P(t)} cosωt...(17) g ₂ = {S(t)+P(t)}tinωt...(18) Here, the first demodulated signal g ₁ and the second The demodulated signal g ₂ is represented as a set of a first demodulated signal g ₁ (K) and a second demodulated signal g ₂ (K), respectively, and the first demodulated signal g ₁ (K) and the second demodulated signal The signal g ₂ (K) is expressed by equations (19) and (20), respectively.

Note that the demodulated signal of the carrier phase pilot appears as a frequency double the carrier frequency.

g ₁ (K)=A _K ′sin (ω _K t+α _K )cosθ _K = (A _K ′/2)・cosθ _K ×e ^j 〓 ^Kt (sinαt−jcosα _K ) +e ^-j 〓 ^Kt (sinα _K +jcosα _K ) …(19) g ₂ (K)=A _K ′sin (ω _K t+α _K ) sinθ _K = (A _K ′/2) sinθ _K ×e ^j 〓 ^Kt (sinα _K −jcosα _K ) +e ^-j 〓 ^Kt (sinα _K + jcosα _K ) ...(20) The first demodulated signal g ₁ and the second demodulated signal g ₂ obtained in this way are supplied to the frequency analyzer 8 and the analysis bandwidth is within |ω| Although frequency analysis is limited to the Kth signal frequency ω _K ,
If there are signal frequencies ω ₁ −ω _N from the first to the Nth, frequency analysis is performed for all of them. Therefore, the carrier phase pilot demodulated signal is frequency doubled and is therefore removed during frequency analysis. That is, by improving the S/N ratio of the signal and converting it into a frequency, the signal frequency ω ₁ to ω _N
Frequency analysis is performed on multi-directional signals of each direction θ ₁ to θ _N .

The first demodulated signal _g1 and the second demodulated signal _g2 are supplied to a frequency analyzer 8, where the first demodulated signal _g1 is a real number input and the second demodulated signal _g2 is an imaginary number input, such as a microcomputer, etc. Frequency analysis is performed using FFT. Therefore, the first demodulated signal g ₁ (K)
As a result of frequency analysis, the frequency spectrum F(ω _K ) in the positive region and the frequency spectrum F(−ω _K ) in the negative region are (21) corresponding to the second demodulated signal g ₂ (K).
and (22).

F(ω _K )=(A _K ′/2) ×(sinα _K cosθ _K +cosα _K sinθ _K ) +j(−cosα _K cosθ _K +sinα _K sinθ _K ) …(21) F(−ω _K )=(A _K '/2) × (sinα _K cosθ _K − cosα _K sinθ _K ) +j (cosα _K cosθ _K + sinα _K + sinθ _K )...(22) Therefore, the frequency analysis section 8 calculates the real part of the frequency spectrum F(ω _K ) and The real number signal ReF (ω _K ) shown in equation (23) and the imaginary number signal ImF (ω _K ) shown in equation (24 ₎ are generated corresponding to the imaginary part, respectively, and the real part and Real signal shown in equation (25) corresponding to each imaginary part
ReF (−ω _K ) and the imaginary signal ImF shown in equation (26)
(−ω _K ) is generated.

ReF (ω _K ) = (A _K ′/2) × (sinα _K cosθ _K + cosα _K sinθ _K ) … (23) ImF (ω _K ) = (A _K ′/2) × (−cosα _K cosθ _K + sinα _K θ _K ) …(24) ReF(−ω _K )=(A _K ′/2) ×(sinα _K cosθ _K −cosα _K sinθ _K )…(25) ImF(−ω _K )=(A _K ′/2 ) × (cosα _K cosθ _K + sinα _K sinθ _K ) …(26) Therefore, the frequency analysis section 8 outputs the real number signal ReF
(ω _K ) is the first real signal ma ₁ shown in equation (27), and the imaginary signal ImF (ω _K ) is (28)
The first imaginary signal m _b1 shown in the formula and the real signal ReF
The second real signal m _a2 shown in equation (29) as a set of (-ω _K ), and the second imaginary signal m _b2 shown in equation (30) as a set of imaginary signals ImF (-ω _K ). Output.

m _a1 = _N 〓 ^K=1 ReF(ω _K ) …(27) m _b1 = _N 〓 ^K=1 ImF(ω _K ) …(28) m _a2 = _N 〓 ^K=1 ReF(−ω _K ) …( 29) m _b2 = _N 〓 ^K=1 ImF(−ω _K )) …(30) These first real signal m _a1 and first imaginary signal
m _b1 , the second real number signal m _a2 , and the second imaginary number signal m _b2 are supplied to the power spectrum creation unit 9 and corresponding to the respective signal frequencies ω ₁ to ω _N , first (31)
The x-axis component real signal X _R (ω _{K )} shown in equation (32), the x-axis component imaginary signal X _I (ω _K ) shown in equation (32), and y shown in equation (33)
The axis component real number signals Y _R (ω _K ) and (ω _K ) and the y axis component imaginary number signal Y _I (ω _K ) shown in equation (34) are created.

X _R (ω _K ) = ReF (ω _K ) + ReF (−ω _K ) = A _K ′sinα _K cosθ _K … (31) X _I (ω _K ) = ImF (ω _K ) − ImF (−ω _K ) = −A _K ′cosα _K cosθ _K … (32) Y _B (ω _K ) = ImF (ω _K ) + ImF (−ω _K ) = A _K ′sinα _K cosθ _K … (33) Y _I (ω _K ) = ReF (ω _K )−FeF(−ω _K ) = A _K ′cosα _K sinθ _K … (34) Furthermore, in the power spectrum creation section 9, (35)
A first power spectrum P ₁ (K) shown in equation (36) and a second power spectrum P ₂ (K) shown in equation (36) are created.

P ₁ (K)=√{ _R ( _K )} ² +{ _I ( _K )} ² =A _K ′cosθ _K …(35) P ₂ (K)=√{ _R ( _K )} ² +{ _I ( _K )} ² = A _K ′sinθ _K … (36) Therefore, from the power spectrum creation unit 9, as a set of first power spectra R ₁ (K) (37)
The first power spectrum P ₁ and the second power spectrum shown in Eq.
A second power spectrum P ₂ shown in equation 4(38) is output as a set of power spectra P ₂ (K).

P ₁ = _N 〓 ^K=1 P ₁ (K) …(37) P ₂ = _N 〓 ^K=1 P ₂ (K) …(38) The first power spectrum P ₁ and the first power spectrum created in this way The power spectra P ₂ of 2 are each supplied to the azimuth calculation unit 10 in correspondence with the frequency, the azimuth is calculated, and the azimuth signal p shown in equation (39) is output.

p= _N 〓 ^K=1 θ _K …(39) Here, the orientation θ _K is determined by the first power spectrum P ₁ (K) and the second power spectrum P ₂ (K) according to equation (40). It is calculated as follows.

θ _K =tan ^-1 {P ₂ (K)/P ₁ (K)} …(40) As described above, by using the conventional underwater acoustic signal azimuth calculation method, the azimuth θ _K with respect to the signal frequency ω _K is calculated.
is generated.

In other words, the conventional method for calculating the direction of an underwater acoustic signal separates the frequency pilot F(t) included in the transmitted composite signal b, and calculates the vertical harmonic signal e 1 and the shifted harmonic signal e ₁ having the accurate frequency and phase of the carrier signal ω. phase signal e ₂
In order to obtain this, a frequency conversion signal extraction circuit 2 having a plurality of circuit configurations is required.

An object of the present invention is to provide a method for calculating the direction of an underwater acoustic signal that does not require a frequency conversion signal extraction circuit.

The underwater acoustic signal azimuth calculation method of the present invention is for instructing an orthogonally modulated wave obtained by orthogonally modulating an x-axis component signal and a y-axis component signal of a received underwater acoustic signal with a carrier frequency and the phase of the carrier frequency. a first frequency-converted signal having a frequency close to that of the carrier phase pilot necessary for receiving and demodulating the underwater acoustic signal transmitted in the form of a composite signal consisting of a carrier phase pilot; a frequency-converted signal generating means for generating a second frequency-converted signal having a phase difference of 90 degrees from the first frequency-converted signal; and a first demodulated signal by multiplying the composite signal and the first frequency-converted signal. a multiplier for generating a second demodulated signal by multiplying the synthesized signal and the second frequency-converted signal; the first demodulated signal is a real input, and the second demodulated signal is an imaginary input; a frequency analysis section that performs frequency analysis and generates an analysis result consisting of a first real number signal, a first imaginary number signal, a second real number signal and a second imaginary number signal, and the first frequency converted signal and the second imaginary number signal. The difference frequency between the conversion frequency included in the frequency conversion signal of The phase difference between the frequency-converted signal and the carrier phase pilot is determined, and the analysis result is frequency-shifted and corrected using the difference frequency, and the phase angle is determined from the analysis result for each frequency of the underwater acoustic signal. and azimuth calculation means for correcting the phase angle by the phase difference to obtain the azimuth for each frequency.

The principle of the underwater acoustic signal azimuth calculation method of the present invention is based on the first frequency conversion including the carrier frequency ω, which was conventionally extracted according to the frequency pilot included in the transmission composite signal and transmitted. A first frequency-converted signal and a second frequency-converted signal containing a converted frequency ω' approximate to the signal and the second frequency-converted signal are internally generated, and after multiplication is performed using these signals, frequency analysis is performed. The first frequency-converted signal is shifted by the difference frequency Δω (=ω'-ω) between the carrier frequency ω and the converted frequency ω' generated as a result of this analysis, and the first frequency-converted signal is changed to the second frequency-converted signal.
The correct orientation is obtained by correcting the phase error ′ with respect to the phase of the carrier frequency ω mixed in when the frequency signal of ω is generated.

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 3 is a block diagram showing an embodiment of the present invention, in which a frequency conversion signal generation circuit 11 and a multiplication circuit 7 are shown.
, a frequency analysis section 8 , and an azimuth calculation section 10 .

In the frequency conversion signal generation circuit 11, the carrier frequency ω
(41)
A second frequency converted signal ₂ ' shown in equation (42) having a phase difference of 90° from the first frequency converted signal ₁ ' shown in the equation (42 ₎ is generated. Here, the frequency conversion signal generation circuit 11 converts the carrier frequency ω from the transmission composite signal sent out from the sensor.
, so the frequencies and phases of ₁ and ₂ above are slightly different. ₁ ′=cos(ω′t′)…(41) ₂ ′=sin(ω′t+′)…(42) Here, between the difference frequency △ω between the carrier frequency ω and the conversion frequency ω′, ( 43) It looks like the formula.

ω'=ω+△ω...(43) The multiplier circuit 7 multiplies the transmission signal c sent from the sensor by each of the aforementioned first frequency-converted signal ₁ ' and second frequency-converted signal ₂ '. Then, a first demodulated signal g ₁ ' shown in equation (44) and a second demodulated signal g ₂ ' shown in equation (45) are generated.

Note that, unlike the conventional example shown in FIG. 2, the transmission composite signal sent from the sensor is the transmission signal c obtained by removing the frequency pilot d from the transmission composite signal b in this embodiment. This is because the frequency pilot d is independently generated in the form of the first and second frequency conversion signals f ₁ ' and f ₂ ' described above.

g ₁ ′={S(t)+P(t)}・cos(ω′t+′) = _N 〓 ^K=1 g ₁ ′(K) …(44) g ₂ ′={S(t)+P(t )}・sin(ω′t+′) = _N 〓 ^K=1 g ₂ ′(K) …(45) Here, the first demodulated signal g ₁ ′(K) and the second demodulated signal g ₂ ′( K) are expressed by the following equations (46) and (47), respectively. Furthermore, a phase error accompanying demodulation is further mixed in, resulting in a phase error of ``.

The frequency analysis unit 8 receives the first demodulated signal g ₁ ′ as a real input, and the second demodulated signal g ₂ ′ as an imaginary input.
Perform frequency analysis.

Therefore, as a result _of frequency analysis, _the frequency spectra F′(ω _K △ω), F ′(ω _K −△
ω) and the frequency spectrum F′(−ω _K +
△ω) and (−ω _K −△ω) are obtained as in equations (48) to (51).

F′(ω _K +△ω)=(A _K ′/2) {sin(α _K +θ _K −
″) −jcos(α _K +θ _K −″)} …(48) F′(ω _K −△ω)=0 …(49) F′(−ω _K +△ω)=(A _K ′/2) {sin(α _K −θ _K
+″) +jcos(α _K −θ _K +″)} …(50) F′(−ω _K −△ω)=0 …(51) Therefore, the frequency analyzer 8 calculates the frequency spectrum.
Corresponding to the real part and imaginary part of F′(ω _K +△ω), the real number signal ReF′(ω _K +
△ω), and the frequency spectrum F′(−ω _K +△
Real number signals ReF' (-ω _K +Δω) and ImF' (-ω _K +Δω) shown in equation (54) are generated corresponding to the real part and imaginary part of ω), respectively.

ReF′(ω _K +△ω)= (A _K ′/2) sin(α _K +θ _K −″) …(52) ImF′(ω _K +△ω)= −(A _K ′/2) cos( α _K +θ _K −″) …(53) ReF′(−ω _K +△ω)= (A _K ′/2) sin(α _K −θ _K +″) …(54) ImF′(−ω _K + △ω) = (A _K ′/2) cos (α _K −θ _K +″) … (55) Therefore, the frequency analysis section 8 outputs a real number signal.
The first real signal m _a1 ′ shown in equation (56) as a set of ReF′(ω _K +△ω) and the imaginary signal ImF′(ω _K +△ω)
The first imaginary signal shown in equation (57) as a set of
m _b1 ′, the second real signal m _a2 ′ shown in equation (58) as a set of real signals ReF′ (−ω _K +△ω), and a set of imaginary signals ImF′ (−ω _K +△ω) Then, the second imaginary signal m _b2 ' shown in equation (59) is output.

m _a1 ′= _N 〓 ^K=1 ReF′(ω _K +△ω) …(56) m _b1 ′= _N 〓 ^K=1 ImF′(ω _K +△ω) …(57) m _a2 ′= _N 〓 ^K=1 ReF′(−ω _K +△ω) …(58) m _b2 ′= _N 〓 ^K=1 ImF′(−ω _K +△ω) …(59) These first real signals m _a1 ′ , a first imaginary signal m _b1 ′, a second real signal m _a2 ′, and a second imaginary signal m _b2 ′ are supplied to the azimuth calculating section 12 .

In the azimuth calculating section 12, first, a differential frequency Δω and a phase error' between the carrier frequency ω and the conversion frequency ω' are determined.

That is, the difference frequency △ω is such that the signal frequency ω _K is the carrier frequency ω, the phase difference α _K is π/2, and the orientation θ _K
The carrier frequency pilot P(t) where is “0”
required from.

In other words, the frequency spectra F′(△ω) and F′(−△ω) for the difference frequency △ω are (60), respectively.
(61).

F′(△ω)=cos″+jsin″…(60) F′(−△ω)=cos″−jsin″…(61) Therefore, the first real signal ReF′(△ω ) and the first imaginary signal ImF'(Δω) are shown as (62) and (63), respectively.

ReF'(△ω)=cos''...(62) ImF'(△ω)=sin''...(63) Therefore, the phase error'' is obtained according to (64).

″=tan ^-1 {ImF′(△ω)/ReF′(△ω) …(64) Next, if we calculate the phase angle β ₁ from equations (52) and (53) above, we get equation (65). becomes, also, (54),
If we calculate the phase angle β ₂ from equation (55), we get equation (66).

β ₁ =−(α _K +θ _K −″)=tan ^-1 {ReF′ (ω _K +△ω)/ImF′(ω _K +△ω)} (65) β ₂ = α _K −θ _K +″ = tan ^-1 {ReF′ (−ω _K +△ω)/ImF′ (−ω _K +△ω)} (66) Therefore, the phase angle γ is as shown in equation (67).

γ=−(β ₁ +β ₂ )/2=θ _K −″… (67) Therefore, the orientation θ _K is as shown in equation (68).

θ _K =γ+″ =tan ^-1 {ImF′(△ω)/ReF′(△ω)} −1/2tan ^-1 {ReF′(ω _K +△ω) /ImF′(ω _K +△ω) }=1/2tan ^-1 {ReF′(−ω _K +△ω)/ImF′(−ω _K +△ω)}
...(68) As is clear from equation (68), in the direction calculation method of this embodiment, the first real number signal of the frequency analysis result is
m _a1 ′ and the first imaginary signal m _b1 ′, and the second real signal m _a2 ′ and the second imaginary signal m _b2 ′.
The orientation θ _K can be found by using only the set of ReF′(ω _K +△ω), the set of ImF′(−ω _K +△ω), and the set of ImF′(−ω _K +△ω). , so it is not necessary to determine the power spectrum independently.

As shown above, a frequency conversion signal generation circuit 11 is used instead of the frequency conversion signal extraction circuit 2 shown in FIG.
By adding , the frequency conversion signal extraction circuit 2 consisting of the frequency pilot separation circuit 3, multiplier circuit 4, phase shift circuit 5, and phase error removal circuit 6 is no longer necessary, and the input from the sensor is also the quadrature modulated wave S(t).
and carrier wave phase pilot P(t) are all that is required.

In the underwater acoustic signal azimuth calculation method of the present invention, the azimuth calculation section calculates the difference frequency △ω between the carrier frequency ω and the conversion frequency ω′ that is uniquely generated during demodulation, and then divides the demodulated signal by this difference frequency. By additionally having functions for shifting and correcting the phase error between ω and ω′ and correcting it, a processor conversion signal generation circuit can be used instead of a frequency conversion signal extraction circuit with a complicated circuit configuration. can be used, there is an effect that a frequency conversion signal extracting circuit having a complicated circuit configuration is unnecessary and the circuit configuration can be simplified.

That is, the method for calculating the direction of an underwater acoustic signal according to the present invention uses a frequency-converted signal close to the carrier frequency, performs frequency analysis using complex number input in a band centered on this signal, and uses the result to perform direction calculation and demodulation. By configuring it to do this, it is possible to simplify the circuit for calculating the direction.

[Brief explanation of drawings]

Fig. 1 is a diagram for explaining underwater acoustic signals according to the present invention and the prior art, Fig. 2 is a block diagram showing an example of the conventional technology, and Fig. 3 is a block diagram showing an embodiment of the present invention. . 1... Transmission signal separation circuit, 2... Frequency conversion signal extraction circuit, 3... Frequency pilot separation circuit,
4... Multiplication circuit, 5... Transfer circuit, 6... Phase error removal circuit, 7... Multiplication circuit, 8... Frequency splitting section, 9... Power spectrum creation section, 10...
Azimuth calculation unit, 11...frequency conversion signal generation circuit,
12...Azimuth calculation unit, a...Underwater acoustic signal, a _x ...
...x-axis direction signal, a _y ...y-axis direction signal, b ... transmission composite signal, c ... transmission signal, d ... frequency pilot, e ₁ ... harmonic, e ₂ ... phase shift signal, ₁ ,
₁ '...first frequency converted signal, ₂ , ₂ '...second
frequency converted signals, g ₁ , g ₁ ′...first demodulated signals,
g ² , g ² ′...second demodulated signal, m _a1 , m _a2 , m _a1 ′,
m _a2 ′……real number signal, m _b1 , m _b2 , m _b2 ′, m _b2 ′……
Imaginary signal, P ₁ ...first power spectrum, P ₂
...Second power spectrum, q...Direction signal,
ω...carrier frequency, ω _K ...signal frequency, ω′...
...Conversion frequency, △ω...Difference frequency, ′,
″…Phase error, θ _K …Azimuth.

Claims (1)

[Claims] 1. A composite signal format consisting of an orthogonally modulated wave obtained by orthogonally modulating the x-axis component signal and y-axis component signal of the received underwater acoustic signal with a carrier frequency, and a carrier wave phase pilot for indicating the phase of the carrier frequency. a first frequency-converted signal having a frequency close to the carrier phase pilot necessary for receiving and demodulating the underwater acoustic signal transmitted by the carrier wave; and a phase having a phase difference of 90 degrees from the first frequency-converted signal. a frequency-converted signal generating means for generating a second frequency-converted signal, which generates a first demodulated signal by multiplying the composite signal and the first frequency-converted signal; a multiplier for generating a second demodulated signal by multiplying the converted signal;
frequency analysis means for performing frequency analysis using the demodulated signal of the first imaginary number as an imaginary input to generate an analysis result consisting of a first real number signal, a first imaginary number signal, a second real number signal and a second imaginary number signal; A difference frequency between the conversion frequency included in the frequency conversion signal and the second frequency conversion signal and the carrier frequency is determined based on the analysis result, and an arc of the ratio between the first real number signal and the first imaginary number signal at this difference frequency. The phase difference between the first frequency-converted signal and the carrier phase pilot is determined by the arctangent, and the analysis result is frequency-shifted and corrected by the difference frequency, and the analysis is performed for each frequency of the underwater acoustic signal. and azimuth calculation means for calculating the phase angle from the result and correcting the phase angle for each frequency by the phase difference to calculate the azimuth for each frequency, thereby calculating the azimuth of the received underwater acoustic signal. A method for calculating the direction of underwater acoustic signals.