JPH04118575A - Measuring elevation angle - Google Patents

Abstract

PURPOSE:To measure an elevation angle of a signal source at a high precision by calculating an excessive level based on a result of frequency analysis of a phasing beam output, and outputting an elevation angle at which the excessive level becomes the largest. CONSTITUTION:A frequency analyzer 23a performs frequency division to an output ya(t) from a level phaser 22a by an FFT or the like, and outputs an output za(f0) for a bin including a frequency f0 of a subject signal source and outputs za(f-2), z0(f-1), za(f1), za(f2) each for two bins before and after that to a power calculator 24a. The power calculator 24a performs a power calculation process to the outputs za(f-2), za(f-1), za(f0), za(f1), za(f2) in a plural ranges, and as a result, it outputs ¦za(f-2)¦<2>, ¦za(f-1)¦<2>, ¦za(f0)¦<2>, ¦za(f1)¦<2>, ¦za(f2)¦<2> to an excessive level calculator 25a. A peak detector 26 compares the outputs ra(f0) - ra(f0) of the excessive level calculators 25a - 25e to output the largest elevation angle of them to an output terminal 27. The elevation angle for the subject signal source can thus be measured at a high precision.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention is directed to a sensor array that receives a narrowband signal from a signal source existing in water or the like, and measures the arrival angle of the narrowband signal. It is related to the measurement method.

(Prior Art) Conventionally, as a method of measuring the arrival elevation angle of a broadband signal from a signal source using a sensor array, the output of each phased beam formed in the elevation direction is frequency-analyzed, and the absolute level of the target frequency is determined. Based on the heave characteristics, the maximum heave angle was taken as the arrival heave angle. An example is shown in FIG.

FIG. 2 is a block diagram showing an example of an elevation angle measuring device used in the conventional elevation angle measuring method using a surface array.

This elevation angle measuring device targets narrowband signals and uses a surface array 1 consisting of 4 stave (horizontal) x 5 stack (fir) sensors as a sensor array, and generates 5 phased beams in the elevation direction. This is a device that measures the elevation angle when no formation occurs.

The surface array 1 has a structure as shown in FIG.
It is composed of 20 sensors in 5 stacks of staves 1a to 1d.

The staves 1a to 1d of the surface array 1 are connected to elevation phasers 2a to 2d, respectively, which perform phasing in the elevation angle, and furthermore, horizontal phasers 3a to 3a, which perform phasing in the horizontal direction, are connected to the output side thereof.
3e are connected to each other. Each horizontal phaser 3a~3
A peak detector 6 is connected to the output side of e through frequency analyzers 4a to 4e and power calculators 5a to 5e, and an output terminal 7 is connected to the output side of the peak detector 6.

Next, a method for measuring the elevation angle of a signal source using this elevation angle measuring device will be explained.

For example, a narrowband signal from a signal source in seawater is received by the area array 1. The signal input to the surface array 1 at time t is converted into an electric signal for each of the staves 1a to 1d, and then input to the first to fourth amplitude phasers 2a to 2d.

The first heave phaser 2a receives five signals 5a1(t), 5a2(t), 5a3() from the stave 1a of the surface array 1.
t>, 5a4(t), and 5a5(1), five rotation directions θ8. θ5. θ. , θ4. A beam is formed by performing phasing at θ8.

Then, the output xaa(1) in the first vertical phasing direction θ8 is sent to the horizontal phaser 3a, and the output xaa in the second vertical phasing direction θ
b(t) to the horizontal phasing device 3b, and the third vertical phasing direction θ
The output x ac (t) is sent to the horizontal phasing device 3c, and the output Xad (t) in the fourth phasing direction θ4 is sent to the horizontal phasing device 3c.
d, the output x (t) of the fifth vertical phasing direction θ is outputted to the horizontal phasing device 3e, e ae , respectively. For example, the beam output x (t) in the first phase phasing direction θ is expressed by the following equation a
aa Ru.

However, the time compensation l for ω ・; shading coefficient τ−; S , (t)
al amount, which is determined by the principal axis direction θ of the beam to be formed.The second, third, and fourth amplitude phaser 2b, 2c.

2d also have staves lb and lc, respectively.

The signal input to 1d is phased to form a beam in the same five rotational directions as the first phaser 2a, and its outputs xba(t) to xbe(t), X. a(t)~x
(t), Xda(t) to xd e e(t) are output to the horizontal phasing devices 3a to 3e in each vertical phasing direction.

The horizontal phaser 3a outputs x from the vertical phaser 2a to 2d.
Using (t) to y (t) is output to the frequency analyzer 4a. Similarly, the horizontal phasers 3b to 3e perform horizontal phasing in the same direction using the outputs of the vertical phasers 2a to 2d to form one beam, resulting in yb(t) to ye( t) to the frequency analyzers 4b to 4e, respectively.

The frequency analyzer 4a outputs the output ya (from the horizontal phaser 3a).
Fast Fourier transform (hereinafter referred to as FFT) for
Perform frequency division and divide the frequency into bins containing the frequency of the signal source to be measured (unit of frequency division by FFT)
The output z (f) is outputted to the power calculator 5a. Similarly, the frequency analyzers 4b to 4e also have horizontal phasers 3b to 3e.
The outputs yb(1) to y(t) are subjected to frequency division, and the outputs of frequency bins zb(f) to ze(f) are output to the power calculators 5b to 5e.

The power calculator 5a calculates the output Za from the frequency analyzer 4a.
(f) is output to the power calculation detector 6 in the complex domain. Similarly, the power calculators 5b to 5e also calculate the output zb(f>~z e
(Perform power calculation processing in the complex domain for f >,
As a result, 1zb(f>2~IZ(fil2) is output to the peak detector 6.

The peak detector 6 outputs 1z of the power calculators 5a to 5e.
(fil ~+Z (f)+2 for a
e to perform comparison processing, detect the maximum value, and output the elevation angle that takes the maximum value to the output terminal 7 as the measurement value of the elevation angle of the signal source.

(Problem M to be Solved by the Invention) However, the above-described method for measuring the elevation angle has the following problems.

FIGS. 4(a) and 4(b) are diagrams explaining the problems of the prior art.

As shown in FIG. 4(a), consider a case where the elevation angle of a signal source 11 is measured by a surface array 1 using a hydrophone underwater, for example. As shown in FIG. 4(b), when the level of ambient noise in the direction of the sea surface 11, that is, the level of the sea surface noise 11a, is higher than that in the direction of the signal source 10 due to the influence of waves, etc., the level of the signal source 10 is lower than that of the sea surface. It is masked (shielded) by the noise 11a. Therefore, the peak detector 6
has a problem in that it cannot detect the elevation angle θ8 of the signal source 10 and outputs the sea surface direction θ as the measured value of the elevation angle of the signal source 10.

The present invention solves the problem that the conventional technology had, in that the level of the signal source is masked by relatively broadband noise such as sea surface noise, making it impossible to measure the elevation angle with high precision. A method for measuring elevation angle is provided.

(Means for Solving the Problems) In order to solve the above problems, the present invention uses a sensor array in which a plurality of sensors are arranged, and uses a plurality of phasing signals in the vertical direction for a narrowband signal from a signal source. In the elevation angle measuring method of forming a beam, frequency-analyzing the phased output of each phased beam, and measuring the arrival angle of arrival of the narrowband signal from the frequency analysis result, the following measures were taken. It is something.

In other words, focusing on the fact that the narrowband signal from the signal source has a level only at the frequency where it exists, the target frequency is determined based on the frequency analysis results of each phased beam output formed in the vertical direction. The surplus level is obtained by subtracting the level of the neighboring frequency from the level of . Then, the arrival elevation angle of the narrowband signal is measured from the peak of the elevation characteristic of the surplus level.

(Function) According to the present invention, since the elevation angle measuring method is configured as described above, the surplus level is calculated from the frequency analysis result of each phased beam output formed in the elevation direction. The maximum elevation angle is output as the measurement result. As a result, even if there is a high level of directional noise, the influence of the noise is removed, and the elevation angle of the target signal source can be measured with high accuracy. Therefore, the above problem can be solved.

(Embodiment) FIG. 1 is a block diagram showing the configuration of an elevation angle measuring device using a method for measuring an elevation angle of a narrowband signal, showing a first embodiment of the present invention.

This elevation angle measuring device uses, for example, four sensors as a sensor array.
Using a surface array 20 consisting of 5 stacks of stave sensors, 5 phased beams are formed in the vertical direction, and 2 bins are set before and after the bin containing the target frequency as bins for surplus level calculation. This is a device that measures elevation angles.

FIG. 5 is a diagram showing the structure of the surface array 20.

As shown in this figure, the surface array 20 is composed of 20 sensors of 4 staves x 5 stacks. In Fig. 5, 20a is the leftmost stave, 20b is the second stave from the left, 20c is the third stave from the left, 20
d is the rightmost stave.

First to fourth phase shifters 21a to 21d are connected to each stave 20a to 20d, respectively. Each elevation phaser 21a to 21d uses the output of each stave 20a to 20d to adjust the arrival time of the elevation angle in the elevation direction, that is, performs elevation phasing, and Elevation phase direction θ
~θ output Xa e aa(t)~x(t), xba(t)~xbe e(t), x(t)~x(t), xdaca
ce (1>~Xde(t)) to the horizontal phaser 22a to 22e, respectively, and is composed of a delay circuit, an adder, and the like.

The horizontal phasing devices 22a to 22e are horizontal phasing devices 21a to 21
Using the output of d, horizontally phase each of the five beams, that is, adjust the arrival time in the horizontal direction with respect to the direction in which the signal source to be measured exists, and each phased output y (t) ~ y
(t) to the frequency analyzers ae 23a to 23e, respectively, and is composed of a delay circuit, an adder, and the like.

The frequency analyzers 23a to 23e are horizontal phasers 22a to 2
2e is frequency-divided by FFT or the like to obtain the frequency f of the signal source to be measured. The outputs za(fo) to ze(fo) of the bin containing bin, and the outputs of the two bins before and after it (za(f 2).

z (f >, z (f >, za(f
2>) a −1a 1 ~(ze(f 2>, ze(f ,>, Ze(fl
>, Ze(f2>) to the power calculators 24a to 24e.

The power calculators 24a to 24e are connected to a peak detector 26 via respective surplus level calculators 25a to 25e, and an output terminal 27 is connected to the output side thereof.

Each power calculator 24a to 24e is connected to each frequency analyzer 23.
The outputs of a to 23e are subjected to power calculation processing in multiple regions, and the processing result is IZa(fz (f )12
This is a circuit that outputs the value to each of the surplus level calculators 25a to 25e, and is composed of a multiplier, an adder, and the like. Each of the surplus level calculators 25a to 25e includes power calculators 24a to 2
This circuit calculates the surplus levels from the outputs of 4e and provides the calculation results r (f ) to r e (f O> to the peak detector 26. The peak detector 26 is
This is a circuit that compares the outputs of the surplus level calculators 25a to 25e, detects the maximum value, and outputs the elevation angle that takes the maximum value to the output terminal 27 as the elevation angle measurement value of the signal source. It is made up of.

FIG. 6 is a circuit diagram of the surplus level calculator 25a in FIG. 1.

This surplus level calculator 25a includes an average processor 30 that calculates the average level ma(fo) of the power calculator 2, and a subtracter of the average level ma(fo) from the output 1za(f)1 of the power calculator 24a. Subtraction result r a (f o
>, and a subtracter 31 for calculating . The other surplus level calculators 25b to 25e also have the same circuit configuration.

Next, a method for measuring the elevation angle using the elevation angle measuring device configured as described above will be explained.

In FIG. 1, a narrowband signal from a signal source is received by an area array 20. In FIG. The signal input to the surface array 20 at time t is converted into an electrical signal every 20a to 20e, and is input to the first to fourth amplitude phasers 21a to 21d.

The first vertical phaser 21a is connected to the staple 2 of the surface array 20.
Using the five signals from 0a, phasing is performed in five vertical directions to form a phased beam, and the output x (t) in the first vertical phasing direction θ is sent to the horizontal phasing a aa phaser. 22a is the output Xab(
t> to the horizontal phasing direction 22b, the output x (t) in the third phasing direction θ to the horizontal phasing device 22CaC, and the output x a d(t
) to the horizontal phasing device 22d, and the fifth vertical phasing direction θ.

The outputs x (t) of e are outputted to the horizontal phaser 22e, respectively. Second, third and fourth phaser 21b
, 21c, and 21d are similarly stave 20b,
The signals input to 20c and 20d are phased to form phased beams in the same five vertical directions as the first vertical phaser 21a, and the output X (Kei) ~ x be (t)
.

The horizontal phasing device 22a performs horizontal phasing in the direction where the signal source to be measured exists using the outputs x(t) to A beam is formed and the result y (t) is output to the frequency analyzer 23a. Similarly, the horizontal phasers 22b to 22d perform horizontal phasing in the same direction using the outputs of the vertical phasers 21a to 21d to form one phased beam, and as a result, yb(t) y (t) are output to frequency analyzers 23b to 23e, respectively.

The frequency analyzer 23a receives the output y from the horizontal phaser 22a.
(t) is frequency-divided using FFT or the like to obtain the frequency f of the signal source to be measured. The output of the bin containing za(fo)
and the output za (f 2 >, za
(f1), za(fl), and za(f2> are output to the power calculator 24a.

Similarly, the frequency analyzers 23b to 23e also output yb(t) to y (t
) is frequency-divided and the output of that frequency bin (
zb (f 2>, Zb (f 1), Zb (f□)
, Z5 (fl), Zb (f2>) ~ (ze(f-
2), ze(f 1>, ze(f>, z (f
>, ze(f2>) is output to the power calculation Oel earthenware 24b to 24e.

The power calculator 24a calculates the output za of the frequency analyzer 23a.
(f 2), za (f-1>, za (f>, z (
Perform power calculation processing in the complex Oal domain for f>, za(f2>, and the result is 1za2)1
2 is output to the surplus level calculator 25a.

Similarly, the power calculators 24b to 24e calculate the outputs (zb (f2), Zb
(f 1), 2b (f□), zb (fl), Zb
(f2)) ~ (ze(f-2), Ze(f >,
ze(fo>, ze(fl>, Ze2) 12) is output to the surplus level calculators 25b to 25e.

In the surplus level calculator 25a, as shown in FIG. Bin output 1za(fo)l
is input to the subtracter 31. The average processor 30 is 1z
a(f-2)21. lz(f)l,1
The average level of za(fl) la −1 Za(f2)1 is calculated, and the calculation result ma(fo) is output to the subtracter 31 .

The subtracter 31 subtracts the output ma(fo>) of the average processor 30 from the output I Za(fo>1) of the bin containing the target layer wavenumber from the power calculator 24a, and the subtraction result ra
(fo) is output to the peak detector 26 in FIG. Similarly, the other surplus level calculators 25b to 25e calculate the outputs (lz (f
> 12. ! zb -2b (f)l, lz (f)12.1z-
1b Ob 2) Using 12), the surplus level r b (f □ >~re(fo
> is calculated and output to the peak detector 26 in FIG.

The peak detector 26 includes surplus level calculators 25a to 25e.
The outputs ra(fo> to re(fo)) are compared, the maximum value is detected, and the elevation angle having the maximum value is outputted to the output terminal 27 as the elevation angle measurement value of the signal source.

As described above, this embodiment has the following advantages.

In this example, the frequency analysis results of each beam output formed in the vertical direction (Za (f-2), Za (f), z
a(f□), za(fl), Zci(f2))～(z
e(f 2), ze(f , >.

Find the power from z8(fo), ze(fl), ze(f2)), and from that power, calculate the surplus level r(f)~re with respect to the level of the frequency near the level of the target frequency.
Calculate (fo). Then, the surplus level ra(f.) ~
The elevation angle at which re(fo) is the maximum is output as the measurement result. Therefore, even if there is a high level of directional noise, if it is near the target frequency and has a relatively wide band, its influence can be accurately removed, and the elevation angle of the target signal source can be determined with high precision. It can be measured by

FIG. 8 is a block diagram of a configuration of an elevation angle measuring device using an elevation angle measuring method showing a second embodiment of the present invention.
Elements common to those in the figures are given the same reference numerals.

In this elevation angle measurement device, a surface array 120 with a different structure
A vertical phaser 121 is connected to the output side of the surface array 120 via horizontal phasers 122a to 122e, and frequency analyzers 23a to 23e are connected to the output side thereof. In other words, the connection order of the vertical phasing device and the horizontal phasing device is switched.

FIG. 8 is a diagram showing the structure of the surface array 120 in FIG. 7. This surface array 120 is composed of 20 sensors in 4 staves x 5 stacks, where 120a is the top stack, 120b is the second stack from the top, and 120C is the second stack from the top.
is the third stack from the top, 120d is the fourth stack from the top, and 120e is the bottom stack.

A method of measuring the elevation angle using the elevation angle measuring device as described above will be explained.

The signal input to the surface array 120 at time t is transmitted to the first to fifth horizontal phasers 122 for each stack 120a to 120e.
a to 122e. First horizontal phaser 122a
performs phasing in one direction using the four signals from the stack 120a of the areal array 120 to form a phased beam--and outputs the result x(t) to the tilt phaser 121. . Second, third, fourth and fifth horizontal phaser 122b
Similarly, stacks 120b to 122e respectively
The signal input to 0e is phased to form a phased beam in one direction, and its output x b (t ) x (t
), xd(t), and xe(t) are output to the swing phaser 121. The vertical phaser 121 is a horizontal phaser 122a to 12
Using the outputs x (t) to Xe(t) of 2e, a phase alignment is performed at five elevation angles θ to θ to form a phased beam. The result ya(1)
~y (t) respectively through frequency analyzers 23a to 23e.
Output to. After the frequency analyzers 23a to 23e,
Processing is performed in the same manner as in the first embodiment shown in FIG.

This second embodiment has substantially the same advantages as the first embodiment.

Figure 9 shows the surplus level calculator 2 in Figure 1 or Figure 7.
FIG. 5 is another circuit configuration diagram of 5a.

This surplus level calculator 25a includes an average processor 32.33.
, a comparator 34, and a subtracter 35. The other surplus level calculators 25b to 25e have similar configurations.

In this surplus level calculator 25a, the power calculator 24a
Output 1za(f 2)l , lza average processor 3
2, and the output IZa(f) of the bin having a higher frequency than the bin containing the target frequency fO. lz
(f) 12 is input to the average processor 1a2 33. Further, the output lz(f)12 of the bin containing the target frequency f0 is input to the subtracter 35.

In the average processor 32] Za(f-2) 2Za(f-1
) 12 average level mNa(fo) is calculated, and comparator 3
Output to 4. Similarly, the average processor 33 calculates l za(f
l>12. l Za(f2>2 average level mua(f
o) is calculated and output to the comparator 34. The comparator 34 is
The output of the average processor 32.33 zj! (fo) and Zua (fO) are compared, and the one with the lower level is selected and output to the subtracter 35. The subtracter 35 receives the target frequency f from the power calculator 24a. The output of the bin containing za(
The output of the comparator 34 is subtracted from f□)l, and the result r a (f○) is output to the peak detector 26 .

When such surplus level calculators 25a to 25e are used, even when a second signal source exists near the target frequency, the comparator 34 calculates the average level on the lower side of the level where no signal source exists. Since it is selected, its influence can be removed.

Note that the present invention is not limited to the illustrated embodiment, and various modifications are possible. Examples of this modification include the following.

(:) In the above embodiment, the surface arrays 20, 120 of 4 staves x 5 stacks are used as the sensor array, but the present invention can be applied to sensor arrays with any number of staves and stacks. Further, the sensor array is not limited to a planar array, and can be applied to an array of any shape such as a linear array that performs vertical phasing.

(ii) If the signal source is underwater, the sensor array may be configured with an acoustic/electrical transducer, but if the signal source is in the air, it may be configured by converting radio waves, ultrasonic waves, etc. into electrical signals. If the configuration is configured to convert, it is also possible to measure the elevation angle with respect to the signal source.

(iii) Each component block in the elevation angle measuring device shown in FIGS. 1 and 7 is configured by an individual circuit.
The method of the present invention can also be applied to a configuration in which execution is performed under program control using a processor.

(Effects of the Invention) As described in detail above, according to the present invention, from the frequency analysis results of each beam output formed in the vertical direction, the surplus level of the level of the target frequency with respect to the level of the neighboring frequencies is determined, The elevation angle at which the surplus level is maximized is output as the measurement result. Therefore, even if there is a high level of directional noise, if it is near the target frequency and has a relatively wide band, its influence can be accurately removed, and the elevation angle of the target signal source can be determined with high precision. can be measured.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the configuration of an elevation angle measuring device using the elevation angle measuring method according to the first embodiment of the present invention, and Fig. 2 is a structural block diagram of the elevation angle measuring device using the conventional elevation angle measuring method. Figure 3 is a structural diagram of the surface array in Figure 2, Figure 4 (
a>, (b) are diagrams explaining the problems of the prior art, FIG. 5 is a structural diagram of the surface array in FIG. 1, FIG. 6 is a circuit configuration diagram of the surplus level calculator in FIG. 1, FIG. 7 is a block diagram of the configuration of an elevation angle measuring device using the elevation angle measuring method according to the second embodiment of the present invention, FIG. 8 is a structural diagram of the surface array in FIG. 7, and FIG. FIG. 7 is another circuit configuration diagram of the surplus level calculator in FIG. 1 or FIG. 7; 20.120.・,,, surface array, 21a to 21d
. 121...Flip phasing device, 22a to 22e, 12
2a-122e...Horizontal phaser, 23a-23
e Frequency analyzer, 24a to 24e Power calculator, 25a to 25e Surplus level calculator, 26 Peak detector. Surface array in Figure 1. Surplus level calculator in Figure 1. Figure 6.

Claims (1)

[Claims] A sensor array in which a plurality of sensors are arranged is used to form a plurality of phased beams in the vertical direction with respect to a narrow band signal from a signal source, and a phased output of each phased beam. In the elevation angle measurement method, the elevation angle of arrival of the narrowband signal is measured based on the frequency analysis result, from the level of the frequency to be measured to the level of nearby frequencies. A method for measuring an elevation angle, comprising: obtaining a surplus level by subtraction, and measuring an arrival elevation angle of the narrowband signal from a peak of an elevation characteristic of the surplus level.