JP2009150662A - Method and device for detecting target signal and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means for easily recognizing a target signal by lessening the azimuth errors and separating noise. <P>SOLUTION: A method for detecting the target signal by frequency-analyzing a receiving acoustic signal with a frequency analysis 101, calculates azimuth vectors in each frequency with an azimuth calculation preprocessing part 102, and calculates the incoming azimuth of the target signal from the azimuth vectors in each frequency calculated by an azimuth calculation post-processing part 103. Then, the azimuth calculation post-processing part 103 calculates addition vectors, by adding the azimuth vector included in a frequency band width, set previously at each shift position, while shifting only the frequency shift width set previously to the azimuth vectors between a previously set upper-limit frequency and lower-limit frequency; selects the addition vectors indicating the maximum vector out of the addition vectors calculated at each shift position; and outputs the azimuth of the selected addition vectors and vector values to a display processing part 104 as a target azimuth and as the degree of concentration. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a target signal detection method, apparatus, and program, and more particularly to a technique for analyzing and displaying a received underwater acoustic signal.

  By receiving and processing an acoustic signal generated from a sound source existing in water, the arrival direction of the acoustic signal is detected, the arrival direction information is converted into a luminance level, and on the plane of the azimuth axis and the time axis A technique for displaying is proposed in Patent Document 1 and the like.

  FIG. 4 is a block diagram illustrating an example of processing of a received acoustic signal related to the present invention, and FIG. 5 is a block diagram illustrating an example of a method of calculating an arrival direction of an acoustic signal.

  The target signal display processing device shown in FIG. 4A measures a direction by using a level calculation unit 401 that measures the level of an acoustic signal received by a plurality of directional beams, and the level and phase information of the acoustic signal of each beam. The target signal is displayed in luminance on the plane of the azimuth axis and the time axis based on the azimuth calculation processing unit 402, the level measurement result output from the level calculation unit 401, and the azimuth measurement result output from the azimuth calculation processing unit 402. The display processing unit 403 is configured.

  Further, another acoustic signal display processing device shown in FIG. 4B includes a frequency analysis unit 410 that performs frequency analysis on an acoustic signal received by a plurality of directional beams, and a level calculation that measures the level of the acoustic signal for each frequency. Unit 411, an azimuth calculation processing unit 412 that calculates an azimuth for each frequency based on the level and phase information of the acoustic signal of each beam, and a level measurement result and an azimuth calculation processing unit 412 for each frequency output from level calculation unit 411 The display processing unit 413 extracts a high-level signal from the azimuth measurement result for each frequency output from, and displays the target signal in luminance on the plane of the azimuth axis and the time axis.

  As shown in FIG. 5, the calculation of the arrival direction of the acoustic signal includes the OMNI signal having the same sensitivity in all directions (hereinafter referred to as omnidirectionality) and the NS signal that forms the directivity of figure 8 in the north-south direction. The azimuth can be calculated from the level and phase relationship of the EW signal that forms the figure 8 directivity in the east-west direction. In FIG. 5, the NS signal and the EW signal indicated by broken lines indicate that the phase is reversed when compared with the OMNI signal.

  For example, in FIG. 5, when an acoustic signal arrives from the direction of 120 degrees, the NS signal level is OA [0.5] and the EW signal level is OB [0.866]. The numbers in [] indicate the level values of the NS signal and the EW signal when the level of the OMNI signal is 1. In this case, the phase relationship is based on the OMNI signal, the NS signal has an opposite phase, and the EW signal has the same phase.

  From this, the quadrant is determined by the phase relationship, and the azimuth is calculated by the following equation. The quadrant is obtained by dividing the plane into four by the north-south axis and the east-west axis. A plane corresponding to 0 to 90 degrees is a quadrant 1, and a plane corresponding to 90 to 180 degrees is from quadrants 2 and 180 degrees. A plane corresponding to 270 degrees is defined as quadrant 3, and a plane corresponding to 270 degrees to 360 degrees is defined as quadrant 4.

θ = | Tan ⁻¹ (OA / OB) | +90 (quadrant number −1)
Quadrant 1: NS signal (same phase), EW signal (same phase)
Quadrant 2: NS signal (anti-phase), EW signal (in-phase)
Quadrant 3: NS signal (reverse phase), EW signal (reverse phase)
Quadrant 4: NS signal (in phase), EW signal (in reverse phase)

  Substituting each value into the above equation, a result of θ≈120 is obtained. Therefore, the arrival direction of the acoustic signal is obtained by measuring the level and phase of the OMNI signal, the NS signal that forms the 8-shaped directivity in the north-south direction, and the EW signal that forms the 8-shaped directivity in the east-west direction. be able to.

  In the method shown in FIG. 4B, in which the frequency analysis is performed and the direction is calculated for each frequency, the level of noise distributed over a wide band is reduced by the narrow band analysis. / N is improved, but when the received signal is a wideband signal, the signal level is also dispersed and lowered in each band, so the effect of improving the S / N cannot be obtained. For such broadband underwater acoustic signals, techniques for improving S / N and facilitating detection have been proposed in Patent Documents 2 to 3 and the like.

  For example, in Patent Document 2, a signal azimuth value and a power spectrum value for each frequency are generated from a received signal of directivity sonobuoy, a signal vector for each frequency is synthesized based on these signal azimuth and power spectrum values, and these signal vectors Is added to all frequencies to obtain a sum signal vector of all frequencies, and then the signal exceeding the threshold level of this sum signal vector is detected. The sum of the levels is obtained by vector addition and the signal component direction is stored, and the noise component is random at each frequency, so that the level becomes 0 by vector addition of all frequencies, The S / N is improved.

  Further, in Patent Document 3, a spectrum analysis unit that calculates signal energy for each frequency cell of an acoustic signal, and a frequency band of the acoustic signal is extracted and extracted based on the signal energy calculated by the spectrum analysis unit. Frequency selection means for outputting only signal energy in the selected frequency band, total energy calculation means for synthesizing the signal energy of the frequency cell outputted from the frequency selection means as a scalar quantity, and outputting as scalar energy, and the frequency selection means Based on the signal energy of the frequency cell output from the azimuth calculation means for calculating the arrival direction of the acoustic signal for each frequency cell, and the signal arrival direction for each frequency cell calculated by the direction calculation means. Vector synthesis hand that synthesizes a vector and outputs it as vector energy And a detection determination unit that determines the presence or absence of a sound source that emits an acoustic signal based on the magnitude of the vector energy output from the vector synthesis unit and the magnitude of the scalar energy output from the total energy calculation unit. Thus, the same effect is obtained.

JP 2000-98016 A JP-A-8-152465 Japanese Patent Laid-Open No. 11-52038

  Among target signal display processing devices that analyze underwater acoustic signals, there are target signal display processing devices that detect and display signals with a certain frequency bandwidth characteristic, especially short-time signals and transient signals. In the case of a time signal or a transient signal, energy is generally dispersed in a frequency band of a certain width as a signal characteristic. Therefore, a short-time signal can be obtained using the target signal display processing device shown in FIG. When a transient signal detection process is performed, there are problems that an azimuth error increases and a display luminance range becomes small so that the azimuth of the signal cannot be emphasized.

  That is, in the method of calculating the azimuth by directly using the received signal shown in FIG. 4A, since the reception frequency bandwidth is generally larger than the bandwidth of a short-time signal or a transient signal, a band having only a noise component. As a result, the S / N ratio decreases and the azimuth error (deviation) increases. In addition, since a sufficient level of luminance information cannot be obtained due to a decrease in the SN ratio, the luminance change becomes small and the signal direction cannot be emphasized.

  Further, in the method of calculating the azimuth for each frequency by performing the frequency analysis shown in FIG. 4B, the signal energy is distributed to each frequency, and the azimuth (one sample) of only the frequency having a large level is adopted to obtain the signal. Since detection is performed, the energy of a signal having a characteristic of a certain frequency bandwidth cannot be sufficiently used, and as a result, an azimuth error (deviation) increases. Further, since signal accumulation is performed for frequency analysis, temporal smoothing is performed. As a result, level fluctuation is reduced and luminance change is reduced. There is a method of increasing the display luminance with a small level fluctuation, but in this case, the fluctuation due to noise is also highlighted, so that it is difficult to distinguish the signal from the target from the noise.

  In addition, in the case of the target signal display processing devices described in Patent Documents 2 to 3, basically, the configuration is such that vector addition is performed for the entire frequency-analyzed band. This is effective when detecting broadband signals, but there is no signal even when detecting signals with certain frequency bandwidth characteristics, especially short-time signals and transient signals. Since the signal including all the bands (bands including only the noise component) is output, the S / N ratio is lowered as a result.

  The objective of this invention is providing the target signal detection method, apparatus, and program which can solve the subject mentioned above.

  The target signal detection method of the present invention performs frequency analysis on a received signal, calculates a direction vector for each frequency analyzed by the frequency analysis, and calculates an arrival direction of the target signal from the calculated direction vector for each frequency. A target signal detection method, wherein a predetermined frequency bandwidth is set at each shift position while shifting a predetermined frequency shift width with respect to the azimuth vector between a predetermined lower limit frequency and an upper limit frequency. Adding the azimuth vectors included in the vector to calculate an addition vector, selecting an addition vector indicating the maximum vector value from the addition vectors calculated at the respective shift positions, and selecting the azimuth of the selected addition vector and A vector value is output as target significant information.

  A target signal detection apparatus according to the present invention includes a frequency analysis unit that performs frequency analysis on a received signal, an azimuth calculation preprocessing unit that performs azimuth calculation for each frequency analyzed by the frequency analysis unit, and outputs an azimuth vector for each frequency. A target signal detection apparatus comprising: an orientation calculation post-processing unit that inputs an orientation vector for each frequency calculated by the orientation calculation pre-processing unit and calculates an arrival direction of the target signal, the post-azimuth calculation post-processing A target signal processing frequency region setting means for setting a lower limit frequency, an upper limit frequency, a frequency bandwidth, and a frequency shift width, and between the lower limit frequency and the upper limit frequency set by the target signal processing frequency region setting means. The azimuth vector included in the set frequency bandwidth is added at each shift position while shifting by the set frequency shift width at A vector addition means, a maximum addition vector selection means for selecting an addition vector indicating the maximum vector value from the addition vectors obtained at the respective shift positions by the vector addition means, and a selection vector selected by the maximum addition vector selection means. And a target signal output means for outputting the direction of the addition vector and the addition vector value as target significant information.

  The program of the present invention is a program for causing a computer to execute processing for calculating the arrival direction of a target signal from a received signal that has been frequency-analyzed into an azimuth vector for each frequency. The azimuth vector between the upper limit frequency and the upper limit frequency is shifted by a preset frequency shift width while adding the azimuth vector included in the preset frequency bandwidth at each shift position to obtain an addition vector. Processing to calculate, processing to select an addition vector indicating the maximum vector value from the addition vectors calculated at each shift position, and output the direction and vector value of the selected addition vector as target significant information Processing is executed.

  The first effect is that the azimuth error is small when the target signal is a short-time signal or a transient signal. The reason for this is that, regarding the azimuth calculation, the azimuth in which the target signal is concentrated is obtained as significant information by adding the vector of the azimuth calculation result obtained in the frequency analysis resolution unit and extracting the vector value (maximum) azimuth. .

  The second effect is that the signal is highlighted and displayed. The reason for this is that, with regard to azimuth calculation, the vector addition of the signal band of the azimuth calculation result obtained in the resolution unit of frequency analysis and the calculation result of azimuth concentration are displayed as luminance, and for noise, the azimuth calculation result for each frequency This is because when the vectors are added, the vector becomes small (close to zero), and the signal becomes large because the signal is concentrated in a specific direction.

  FIG. 1 is a functional block diagram of a target signal display processing apparatus showing an embodiment of the present invention.

  A target signal display processing apparatus 100 according to the present embodiment includes a frequency analysis unit 101, a direction calculation pre-processing unit 102, a direction calculation post-processing unit 103, and a display processing unit 104. The frequency analysis unit 101 and the azimuth calculation preprocessing unit 102 are the same circuits as the frequency analysis unit 410 and the azimuth calculation processing unit 412 in FIG.

  The frequency analysis unit 101 receives the received acoustic signal, performs frequency analysis, and outputs the frequency analysis result to the azimuth calculation preprocessing unit 102. The azimuth calculation pre-processing unit 102 performs azimuth calculation for each frequency from the input frequency analysis result based on the level and phase relationship of each beam shown in FIG. 5 and outputs the azimuth calculation result for each frequency to the azimuth calculation post-processing unit 103. To do.

  The azimuth calculation post-processing unit 103 calculates an azimuth for each frequency bandwidth of the target signal to be calculated and its concentration degree from the azimuth calculation result for each input frequency, and the azimuth with the maximum concentration degree is obtained from the calculation. And the degree of concentration is extracted as significant information of the target signal, and the orientation and the degree of concentration extracted are output to the display processing unit 104. The display processing unit 104 converts the concentration level into luminance information and displays it on the plane of the azimuth axis and the time axis based on the input azimuth and concentration level.

  For example, as shown in FIG. 2, the target signal display processing device 100 includes a data bus 110, an A / D converter 111 that converts a received acoustic signal into digital data and connects the digital data, a CPU 112, a ROM, and a RAM. It can be realized as a configuration including the storage unit 113, the display unit 200, and the input unit 300 and the input / output interface unit 114 that connects the data buses.

  In this case, the received acoustic signal converted into digital data is temporarily stored in the RAM of the storage unit 113. The ROM of the storage unit 113 stores a program for executing the target signal display process of the present embodiment. The CPU 112 reads the program stored in the ROM and stores it in the RAM according to the program. The target signal display process of this embodiment is performed with respect to the digital reception sound signal which is present. Therefore, the CPU 112 and the storage unit 113 have a function as a computer for executing the target signal display processing program of the present embodiment.

  FIG. 3 is a diagram illustrating an outline of processing of the azimuth calculation post-processing unit 103 according to the present embodiment. The operation of this embodiment will be described below with reference to FIGS.

  The frequency analysis unit 101 receives the received acoustic signal, performs frequency analysis, and outputs the frequency analysis result to the azimuth calculation preprocessing unit 102. When the azimuth is calculated from the OMNI signal, NS signal, and EW signal, the frequency of each of the three signals is analyzed and the result is output. In the case of a system in which a plurality of directional beams are formed on the entire circumference and the azimuth is calculated, frequency analysis is performed on all the beams.

  The azimuth calculation pre-processing unit 102 performs azimuth calculation for each frequency based on the level and phase relationship of each beam based on the frequency analysis result input from the frequency analysis unit 101, and the azimuth calculation post-processing unit 103 performs the frequency calculation for each frequency. Azimuth calculation result (azimuth vector for each frequency) is output. When calculating a direction by forming a plurality of directional beams around the entire circumference, a method of calculating the direction based only on the level is used. Briefly, it is possible to adopt a method of calculating an azimuth vector for each frequency by extracting a high-level beam and obtaining a peak level by quadratic curve approximation or the like from the relationship between signal levels on both sides thereof.

  The azimuth calculation post-processing unit 103 uses the azimuth vector for each frequency input from the azimuth calculation pre-processing unit 102 to calculate the azimuth for each fixed frequency bandwidth and its concentration, The degree of concentration is extracted as significant information of the target signal, and the extracted orientation and degree of concentration are output to the display processing unit 104. The operation of the azimuth calculation post-processing unit 103 will be specifically described with reference to FIG.

  In order to process only the frequency band that matches the target signal (transient signal) from the received signal, the lower limit frequency and upper limit frequency that are assumed to be input of the target signal (transient signal) are set (for example, the lower limit frequency is 200 Hz, the upper limit frequency) For example, 2000 Hz). Further, the frequency bandwidth of the target signal (transient signal) is set (for example, the frequency bandwidth is 200 Hz). Further, a frequency shift width is set in order to perform the azimuth vector addition process while shifting between the band frequencies within the upper and lower limit frequency ranges (for example, a frequency shift width of 100 Hz) (S1).

  If this frequency shift width is too large, there is a possibility that the target signal cannot be properly captured. If it is too small, the processing load becomes large. There is. These setting values can be set by the operator from the input unit 300, and the setting data is stored in the RAM or the like of the storage unit 113. The CPU 112 reads out the set value from the RAM and refers to it when executing the processing program of the present embodiment.

  After the parameter setting is completed, the azimuth vector for each frequency included in the range of 200 Hz to 400 Hz (the first frequency bandwidth 200 Hz) is added from the azimuth vectors for each frequency input from the azimuth calculation preprocessing unit 102. Then, the direction of the addition vector (signal orientation) and the magnitude of the addition vector (azimuth concentration) are obtained (S2). When the azimuth is concentrated in a specific azimuth, the direction indicates an average azimuth, and the vector size indicates the azimuth concentration. On the other hand, when the azimuth is uniformly distributed due to noise or the like, the addition vector approaches the center, and the vector size (azimuth concentration) decreases.

  In the azimuth vector addition process of this embodiment, the azimuth calculation result (azimuth vector) for each frequency is normalized to all “1” and added in the azimuth direction. Yes. This means that if there is a large signal (narrowband signal) at a specific frequency within the frequency band to be added, the direction of the signal to be received (transient signal) may depend on the direction of this narrowband signal. In order to prevent this, if such influence is small, the direction calculation result (direction vector) for each frequency may be added as it is.

  Subsequently, based on the setting parameter, the frequency is shifted by 100 Hz (S3), and the direction vector for each frequency input from the direction calculation pre-processing unit 102 is set to a range of 300 Hz to 500 Hz (next frequency bandwidth 200 Hz). An addition process of the azimuth vectors for each frequency included is performed to determine the direction of the addition vector (signal azimuth) and the magnitude of the addition vector (azimuth concentration) (S2).

  In the same manner, addition processing of azimuth vectors for each frequency included in the range of the frequency bandwidth 200 Hz while shifting the frequency by 100 Hz from the azimuth vectors for each frequency input from the azimuth calculation preprocessing unit 102 is performed from 1800 Hz to A total of 16 azimuth vector addition processes are repeated until the azimuth vector addition process for each frequency included in the range of 2000 Hz is completed (S2 to S4).

  After the azimuth vector addition process up to the set upper limit frequency (2000 Hz) is completed (S4, YES), among the obtained 16 addition vector values, the value of the addition vector that maximizes the vector size and The direction of the addition vector is selected as significant information, and the frequency band for which the maximum addition vector value is obtained is extracted (S5).

  The direction of the addition vector selected as the significant information and the value of the addition vector are output to the display processing unit 104 as the target orientation and the degree of concentration (S6). The display processing unit 104 generates data for displaying the concentration level as luminance on the plane of the azimuth axis and the time axis based on the input azimuth and concentration level, and outputs the data to the display unit 200. The display unit 200 receives the data from the display processing unit 104, converts the concentration level into a luminance level, and displays it on the plane of the azimuth axis and the time axis.

  In the present embodiment, the setting parameters shown in parentheses are merely examples, and the present invention is not limited to them. The lower limit frequency, the upper limit frequency, the frequency bandwidth, and the frequency shift width are the reception target signals (transient Signal) can be appropriately changed and set in accordance with the expected frequency range, frequency band characteristics, processing capability, and the like.

  According to the present embodiment, since the direction vector addition processing is performed in advance by predicting the frequency band characteristics and frequency range of the reception target signal (transient signal), the target signal detection efficiency can be improved and the direction vector addition is performed. Since the S / N is also improved by the processing, the display luminance range can be enlarged and the signal orientation can be emphasized and displayed.

  In the above-described embodiment, an acoustic signal generated from a sound source existing in water is applied as a reception signal, but the present invention is an acoustic signal generated from a sound source existing in the air or a radio signal such as a radar signal. It can also be applied to.

It is a functional block diagram of the target signal display processing device showing an embodiment of the present invention. It is a schematic block diagram which shows the structure in the case of implement | achieving the target signal display processing apparatus of this embodiment by software. It is a figure which shows the process outline | summary of the azimuth calculation post-processing part of this embodiment. It is a figure which shows the structure relevant to this invention. It is a figure which shows the concept of an example of an azimuth | direction calculation method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Target signal display processing apparatus 101,410 Frequency analysis part 102 Direction calculation pre-processing part 103 Direction calculation post-processing part 104,403,413 Display processing part 401,411 Level calculation part 402,412 Direction calculation processing part

Claims (12)

A target signal detection method for performing frequency analysis on a received signal, calculating a direction vector for each frequency analyzed by the frequency analysis, and calculating an arrival direction of the target signal from the calculated direction vector for each frequency,
The azimuth vector included in the preset frequency bandwidth at each shift position is shifted with respect to the azimuth vector between the preset lower limit frequency and the upper limit frequency by a preset frequency shift width. Addition is performed to calculate an addition vector, an addition vector indicating the maximum vector value is selected from the addition vectors calculated at the respective shift positions, and the direction and vector value of the selected addition vector are used as target significant information. A target signal detection method comprising: outputting a target signal.   The lower limit frequency and the upper limit frequency, and the frequency bandwidth are set to a lower limit frequency and an upper limit frequency at which target target signal input is assumed and a frequency bandwidth at which frequencies from the target signal are concentrated. The target signal detection method according to claim 1.   3. The target signal detection according to claim 1, wherein in the addition processing of the azimuth vectors included in the frequency bandwidth, all the magnitudes of the azimuth vectors for each frequency are normalized to 1 and added. Method.   The target signal detection method according to claim 1, wherein the output target significant information is displayed by a luminance level on a plane of a time axis and an azimuth axis.   The target signal detection method according to claim 1, wherein the received signal is an underwater acoustic signal. A frequency analysis unit that performs frequency analysis on the received signal, a direction calculation preprocessing unit that calculates a direction for each frequency analyzed by the frequency analysis unit and outputs a direction vector for each frequency, and a calculation by the direction calculation preprocessing unit A target signal detection device comprising an orientation calculation post-processing unit that inputs an orientation vector for each frequency and calculates an arrival direction of the target signal,
The azimuth calculation post-processing unit is
Target signal processing frequency region setting means for setting a lower limit frequency and an upper limit frequency, a frequency bandwidth, and a frequency shift width, and
The azimuth included in the set frequency bandwidth at each shift position while shifting by the set frequency shift width between the lower limit frequency and the upper limit frequency set by the target signal processing frequency region setting means Vector addition means for adding vectors;
Maximum addition vector selection means for selecting an addition vector indicating the maximum vector value from the addition vectors obtained at the respective shift positions by the vector addition means;
A target signal detection device comprising target signal output means for outputting the direction of the addition vector selected by the maximum addition vector selection means and the addition vector value as target significant information.   7. The vector addition means according to claim 6, wherein the vector addition means comprises means for normalizing all magnitudes of the azimuth vectors for each frequency output from the azimuth calculation preprocessing section and performing addition processing. Target signal detection device.   7. A display unit for inputting target significant information output from the target signal output means and performing display converted into a luminance level on a plane composed of a time axis and an azimuth axis. Or the target signal detection device according to 7.   The target signal detection device according to claim 6, wherein the reception signal is an underwater acoustic signal. A program for causing a computer to execute processing for calculating an arrival direction of a target signal from a reception signal subjected to frequency analysis into an orientation vector for each frequency,
The computer shifts the azimuth vector between a preset lower limit frequency and an upper limit frequency by a preset frequency shift width, and is included within a preset frequency bandwidth at each shift position. A process of calculating the addition vector by adding the azimuth vectors, a process of selecting an addition vector indicating the maximum vector value from the addition vectors calculated at the respective shift positions, an azimuth of the selected addition vector, and A program for executing a process of outputting a vector value as target significant information.   The program according to claim 10, wherein the process of calculating the addition vector is a process of normalizing and adding all the magnitudes of the azimuth vectors for each frequency to one. 12. The program according to claim 10, further comprising a process of converting the output significant information of the target into a luminance level and displaying it on a plane of time axis and azimuth axis.

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