JP3139420B2 - Signal detection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal detection system, and more particularly, to a signal detection system for detecting a signal which is generated by a sound source existing in water and whose frequency is temporally unstable.

[0002]

2. Description of the Related Art Conventionally, this kind of signal detection system is used for detecting a signal generated by a sound source existing in water.

FIG. 4 is a block diagram showing a configuration example of a conventional signal detection system.

In this conventional example, as shown in FIG. 4, when an acoustic signal is input in water, a spectrum analysis section 1 analyzes the spectrum of the acoustic signal and outputs the analysis result.
An azimuth calculating unit 10 for calculating an arrival direction of an acoustic signal for each frequency cell based on an analysis result of the spectrum analyzing unit 1; and a display unit for displaying the analysis result of the spectrum analyzing unit 1 and the calculation result of the azimuth calculating unit 10. 11 is comprised.

[0005] A signal detection operation in the signal detection system configured as described above will be described below.

When an acoustic signal is input underwater, first,
In the spectrum analyzer 1, the input acoustic signal is
The signal level is converted to a signal level for each frequency, and is temporally integrated to emphasize a frequency-stable signal.

Next, the azimuth calculation unit 10 calculates the arrival and departure of the acoustic signal for each frequency based on the integration result in the spectrum analysis unit 1.

After that, the processing results of the spectrum analyzing section 1 and the azimuth calculating section 10 are sent to the display section 11, and the display section 11 displays the signal level and the signal azimuth with respect to the signal frequency.

FIG. 5 is a diagram showing an energy level (hereinafter referred to as a frequency versus level format) with respect to the frequency of the acoustic signal displayed on the display unit 11 shown in FIG. Expressed by the vertical position.

FIG. 6 is a diagram showing the direction of arrival (hereinafter referred to as a frequency versus direction format) with respect to the frequency of the acoustic signal displayed on the display unit 11 shown in FIG. The azimuth is represented by the display position.

In the above-described signal detection method, a sound source exists in water, and a signal of a specific frequency (hereinafter, referred to as a narrow band signal) is continuously generated when the level of an acoustic signal emitted from the sound source is equal to or higher than a predetermined value. If the frequency portion is emitted, the frequency portion is displayed at a higher level than the other frequency portions in the frequency versus level format as shown in FIG. Because the narrowband signal is frequency-constant, it is coordinated by integration, and its direction of arrival is also determined in one direction.On the other hand, it is noise that exists in frequency parts other than the narrowband signal frequency, and the noise is the frequency. This is because, since it is random in nature, it is not emphasized by integration, and its arrival direction is also randomly determined in one direction.

[0012]

However, in the conventional signal detection system as described above, since the analysis resolution at the time of spectral analysis of the input underwater acoustic signal is narrow, the width is large in the circumferential algebra direction. The signal is dispersed into a plurality of frequency cells, and the signal level in each of the frequency cells decreases. In addition, since the frequency is not stable, the effect of integration is not sufficiently obtained and the signal is buried in noise.

[0013] Therefore, there is a problem that a wide-range signal which is unstable in the frequency direction generated by an underwater sound source cannot be detected.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and detects an unstable and wide signal in the frequency direction generated by an underwater target. It is an object of the present invention to provide a signal detection method capable of performing the above.

[0015]

In order to achieve the above object, the present invention provides a signal detection system for detecting a signal level and a direction of arrival of an audio signal based on an input wideband signal. the wide band signal
In a signal detection method for extracting a frequency band in which an audio signal is detected and detecting a signal level and an arrival direction of the audio signal only from the signal energy in the extracted frequency band, a signal for each frequency cell of the audio signal Enel
Spectrum analyzing means for calculating the energy,
The sound based on the signal energy calculated by the analyzing means.
Extract the frequency band of the sound signal and apply it to the extracted frequency band.
Frequency selection means to output only the signal energy
And a signal of a frequency cell output from the frequency selecting means.
Combines energy as a scalar quantity and creates a scalar energy
Energy calculating means for outputting the energy as energy,
Signal energy of frequency cell output from number selection means
Based on the direction of arrival of the acoustic signal for each frequency cell
Azimuth calculating means for calculating, and azimuth calculated by the azimuth calculating means.
Vector consisting of signal arrival directions for each frequency cell
Vector that synthesizes and outputs vector energy
Vector synthesizing means, and the vector output from the vector synthesizing means.
Vector energy magnitude and total energy calculator
Based on the magnitude of the scalar energy output from the stage
Detection to determine the presence or absence of a sound source that emits an acoustic signal
Determining means .

[0016]

[0017] The spectrum analyzing means may be an FFT.
The signal energy of each frequency cell of the acoustic signal is calculated by using the technique described in (1).

Further, the frequency selecting means divides a frequency band of the acoustic signal into a plurality of bands, selects a corresponding band from the signal energies calculated by the spectrum analyzing means, and selects only the signal energy in the band. It is characterized by outputting.

Further, the plurality of bands are determined in advance.

The detection determining means compares the magnitude of the vector energy output from the vector synthesizing means with the magnitude of the scalar energy output from the total energy calculating means, and the ratio is equal to or greater than a preset value. When it is, it is characterized as detecting.

(Operation) In the present invention configured as described above, only the signals of the frequency cells in the band in which the wideband signal is detected are extracted, and the energy is calculated for each of the extracted signals of the frequency cells. The calculated energies of the frequency cells are combined as a scalar quantity to obtain scalar energy. In addition, a signal arrival direction is calculated for the extracted signal of each frequency cell, and further, a direction in which the calculated arrival direction is set as the direction and a vector that increases the energy of each frequency cell calculated earlier is calculated for each frequency cell. Create and combine these vectors to determine the vector energy. Then, a ratio between the scalar energy and the vector energy is obtained in order to normalize the noise level, and when the ratio is equal to or larger than a predetermined value, it is determined that a wideband signal is detected.

As a result, it is possible to detect a wide band signal which cannot be detected because of being buried in noise in the conventional method.

[0023]

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

FIG. 1 is a block diagram showing the configuration of an embodiment of the signal detection system of the present invention.

In this embodiment, as shown in FIG. 1, when an acoustic signal emitted from a sound source in water is input, the spectrum of the acoustic signal is analyzed, and the signal energy of each frequency cell of the input acoustic signal is calculated. A spectrum analysis unit 1 to be calculated and a frequency band of an acoustic signal emitted from a sound source are divided into a plurality of bands, and a corresponding band (hereinafter, referred to as a wide band band) is selected from the signal energy calculated by the spectrum analysis unit 1. A frequency selection unit 3 that outputs only the signal energy in the band, a total energy calculation unit 2 that combines the signal energies of the frequency cells output from the frequency selection unit 3 as a scalar amount, and outputs the scalar energy, Based on the signal energy of the frequency cell output from the selection unit 3, the arrival direction of the acoustic signal An azimuth calculation unit 4 that calculates for each frequency cell, a vector formed by the signal energy of the frequency cell calculated by the spectrum analysis unit 1 and the signal arrival azimuth of the frequency cell calculated by the azimuth calculation unit 4, A vector synthesis unit 5 that synthesizes over all the frequency cells of the selected wideband band and outputs it as vector energy, and a magnitude of the vector energy output from the vector synthesis unit 5 and output from the total energy calculation unit 2 A detection determination unit 6 that compares the magnitude of the scalar energy with the magnitude of the scalar energy and determines that the detection is performed when the ratio is equal to or greater than a preset value. In this embodiment, the number of wideband bands is n. F _3-1 , f _3-2 , f _3-n in the frequency selector 3 represent the average frequency of the wideband signal emitted by the target, and △ f _3-1 , Δf _3-2 , Δ
f _3-n represents the signal width of the wideband signal, and these values are set in advance.

The signal detection operation in the signal detection system configured as described above will be described below.

When an acoustic signal is input underwater, first,
East and west, north and south directions
Acoustic signal direction is calculated, the frequency analysis of <br/> been using techniques such as FFT, east and west, for each frequency is the north-south direction of the signal energy
And then the calculated east-west, north-south signal energy
By synthesizing the energy, the signal energy for each frequency cell is calculated.

Next, the frequency selection unit 3 applies a window to a preset frequency band that matches the wideband signal generated by the target, and extracts only frequency cells in the wideband band.

FIG. 2 is a diagram showing an output image of the frequency selector 3 shown in FIG. 1 in a frequency-to-level format.

In FIG. 2, the processing band 7 is the processing band in the frequency selection unit 3-1, the processing band 8 is the processing band in the frequency selection unit 3-2, and the processing band 9 is the frequency selection unit 3
-N is the processing band.

Next, in the total energy calculating section 2, the energies of all the frequency cells extracted by the frequency selecting section 3 are added as a scalar quantity, the energy of the entire wide band is calculated and output as scalar energy. You.

The azimuth calculating unit 4 calculates the east, west, north and south calculated by the spectrum analyzing unit 1 for each frequency cell in the wide band band extracted by the frequency selecting unit 3.
Based on the signal energy in the direction, the signal arrival direction is calculated using a well-known formula . Then, the calculated arrival direction is set as the direction, and the vector is output to the vector synthesis unit 5 as vector information having the energy calculated by the spectrum analysis unit 1 as a magnitude.

Then, in the vector synthesizing unit 5, the respective vectors output from the azimuth calculating unit 4 are synthesized, and the energy (vector energy) and the arrival azimuth of only the signal in the wide band band are obtained.

FIG. 3 is a diagram for explaining a vector synthesizing operation in the vector synthesizing section 5 shown in FIG.

Note that V _3-1 , V _3-2 , and V _3-n are vectors output from the azimuth calculation unit 4, respectively.

First, V _3-1 and V _3-2 are synthesized (Equation 1).
Thereafter, V _3-n is synthesized (Equation 2).

V _3-1 + V _3-2 = (V _3-1 + V _3-2 ) (Equation 1) (V _3-1 + V _3-2 ) +... + V _3-n = (V _3-1 + V _3-2 +... + V _3-n ) (Equation 2) Then, in the detection determination section 6, the vector energy output from the vector synthesis section 5 and the total energy calculation section 2
Is compared with the scalar energy output from the controller, and when the ratio between the two is greater than or equal to a preset value, it is determined that detection is performed.

The reason is as follows.

When the input acoustic signal does not include a wideband signal emitted by the underwater target, each wideband band contains only noise. Since the arrival direction of the noise is random, when the vector synthesis is performed by the vector synthesis unit 5, the magnitude (vector energy) of the output vector becomes a value close to zero. Conversely, if a wideband signal is included, the direction of arrival of the signal is relatively stable, and the magnitude (vector energy) of the output vector of the vector synthesizing unit 5 is a value having a certain level.

On the other hand, since the processing in the total energy calculation unit 2 is scalar synthesis, it is not affected by the arrival direction of the signal, and the result is the sum of the energy of the signal generated by the sound source and the energy of the noise. . Therefore, the noise level is normalized by taking the ratio between the vector energy and the scalar energy (sum of energy).

[0041]

As described above, in the present invention,
Only the signals in the band in which the wideband signal is detected are extracted, the energy and the direction of arrival of the signals in those bands are obtained, and the wideband signal is detected from the information. And a wide signal can be detected.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a signal detection system according to the present invention.

FIG. 2 is a diagram illustrating an output image of a frequency selection unit illustrated in FIG. 1 in a frequency-to-level format.

FIG. 3 is a diagram for explaining a vector combining operation in a vector combining unit 5 shown in FIG. 1;

FIG. 4 is a block diagram showing a configuration example of a conventional signal detection method.

FIG. 5 is a diagram showing an energy level with respect to a frequency of an acoustic signal displayed on the display unit shown in FIG. 4;

6 is a diagram showing an arrival direction with respect to a frequency of an acoustic signal displayed on the display unit shown in FIG. 4;

[Explanation of symbols]

 Reference Signs List 1 spectrum analysis unit 2 total energy calculation unit 3,3-1,3-2,3-n frequency selection unit 4 azimuth calculation unit 5 vector synthesis unit 6 detection determination unit 7,8,9 processing area

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01S 3/00-3/86 G01S 5/18-5/30 G01S 7/52-7/64 G01S 15 / 00-15/96 G01H 3/08

Claims (5)

(57) [Claims] 1. A signal detection method for detecting a signal level and a direction of arrival of an audio signal based on an input wideband signal, wherein a frequency band in which the audio signal based on the wideband signal is detected is extracted. Detecting the signal level and the direction of arrival of the audio signal only from the signal energy in the extracted frequency band, and calculating the signal energy of each frequency cell of the audio signal.
Spectrum analysis means, and the signal energy calculated by the spectrum analysis means.
Extracting the frequency band of the sound signal based on the extracted
Circuit that outputs only signal energy in the
A wave number selecting unit, and a signal energy of a frequency cell output from the frequency selecting unit.
Combining lugie as a scalar quantity, scalar energy
Total energy calculating means for outputting the signal of the frequency cell output from the frequency selecting means.
The direction of arrival of the acoustic signal is determined based on the energy
And azimuth calculating means for calculating for each cell, the signal for each frequency cell, which is calculated by the direction calculating unit arrives
Combines vectors composed of incoming directions,
Vector synthesis means for outputting as energy,
Magnitude of vector energy output from the torque combining means
And the scalar output from the total energy calculating means
An acoustic signal is emitted based on the amount of energy
And a detection determining means for determining the presence or absence of a sound source . 2. The signal detection method according to claim 1 , wherein said spectrum analysis means calculates the signal energy of each frequency cell of said acoustic signal using an FFT technique. 3. A signal detection method according to claim 1 or claim 2, wherein the frequency selection means divides the frequency band of the acoustic signal has a plurality of bands, the signal energy which has been calculated in the spectral analysis means A signal detection method, wherein a corresponding band is selected from the above, and only the signal energy in that band is output. 4. The signal detection method according to claim 3 , wherein the plurality of bands are determined in advance. 5. A signal detection method according to any one of claims 1 to 4, wherein the detection determining means is output from the size and the total energy calculation means of the output vector energy from said vector combining means A signal detection method that compares the magnitude of the scalar energy with the magnitude of the scalar energy and determines that the detection is performed when the ratio is equal to or greater than a preset value.