JP6048637B2 - Active sonar device and signal processing method thereof - Google Patents

Description

  The present invention relates to an active sonar device and a signal processing method thereof, and more particularly to a method of calculating a signal S / N ratio of a target reverberation sound from a correlation processing result.

  As is well known in this technical field, a sonar device refers to a device for obtaining information about an object in the sea using underwater sound waves. The sonar device is roughly classified into an active sonar device and a passive sonar device.

  The principle of the active sonar device is the same as Yamabi. In other words, the active sonar device knows the distance between the device and the target from the time difference until it makes a sound from itself and the sound is reflected back from the target and the reflected sound is heard. Is the principle. In other words, the active sonar device refers to a device for evaluating the influence of a sound wave emitted by the device on a certain distant object and obtaining information related to the object.

  In more detail, the basic principle of an active sonar device is that multiple arrays are arranged, and a sonic wave is generated on its own after phasing processing to provide transmission and reception directivity in a specific direction. Then, the received signal is subjected to signal processing, echo sound (echo) from the target contained in the received signal is detected, and the direction and distance of the target are specified based on the detected sound.

  In a conventional active sonar apparatus, replica correlation processing is used as a method for detecting an echo signal from a received signal. Here, “replica correlation” is a signal processing method for calculating the degree of correlation between a signal (replica signal) that is a sample of a signal transmitted by itself and a received signal, and is also referred to as cross-correlation processing. At this time, if the replica correlation is repeated while shifting the time with respect to the received signal, the cross-correlation processing result becomes the maximum value at the time when the replica signal and the received signal are most similar, that is, the time when the echo is received. The active sonar apparatus detects an echo signal by this cross-correlation process.

  Conventionally, various active sonar devices have been proposed. For example, Japanese Patent Laid-Open No. 2008-232861 (Patent Document 1) discloses that in order to cope with the Doppler shift, only the time portion at which the echo signal is detected is cut out and subjected to replica correlation processing, and noise other than the signal processing interval is detected. An active sonar device is disclosed which eliminates the effects.

  By the way, the background noise level is constantly changing due to random noise. In addition, the sound transmitted by itself may become a strong reverberation due to seabed reflection, and a strong signal is generated at an unpredictable time on the actual sea surface. As a result, the cross-correlation processing result is a relatively large value even at that time. Therefore, it is difficult to detect an echo signal by setting a threshold value with a simple fixed value. Therefore, in any processing system, a process for extracting a difference from background noise and an S / N ratio (Signal / Noise ratio) is essential.

  In general, AGC (automatic gain control) processing for estimating a background noise level from currently acquired data by statistical processing such as moving average and normalizing the value is well known (for example, patent document). 2, see Patent Document 3). However, in Patent Document 2 and Patent Document 3, replica correlation processing is not performed.

  In the conventional technique, PDAGC (post detection automatic gain control) processing has been used for the cross-correlation processing result between the transmission signal (replica signal) and the reception signal. This is a method of calculating the S / N ratio by using the average value of the past N points of data as an estimated value of the background noise level and normalizing with the estimated value of the cross correlation processing result.

JP 2008-232861 A Japanese Patent No. 2995374 Japanese Patent No. 4737882

  However, the method of estimating the background noise level by statistical processing always depends on past data. For this reason, there is a problem that an echo signal cannot be normally detected when a suddenly strong signal or abnormal value is mixed.

  More specifically, on the actual sea surface, a strong signal is generated at an unpredictable time due to reverberation due to the sound transmitted by itself or a sudden change in background noise level. Therefore, in the method of using the average value of the past N points of data as the estimated value of the background noise level, which is the conventional PDAGC method, the estimated noise level inevitably increases near the time when the signal level is high. There is a problem that a blind zone in which no detection is detected occurs (see FIG. 4).

[Object of invention]
An object of the present invention is to solve a blind zone problem in which a signal S / N ratio is not detected in signal S / N calculation processing in active sonar signal processing, and to maintain stable signal S / N detection accuracy.

Signal processing method of the present invention is a signal processing method for calculating a signal S / N ratio from the replica correlation processing result obtained by the replica correlation processing between the replica signal and the received signal of the transmission signal, the reception channel ( The signal level increase / decrease ratio is obtained by dividing the time t + Δt (Δt: time resolution) data by the time t data with respect to the replica correlation processing result for each reception direction) , and the signal level increase / decrease ratio is differentiated. A differential processing step to output as data , and a value less than 1.0 is forcibly set to 1.0 with respect to the differential data , and only the positive change amount in the direction in which the signal level increases is extracted, and the data after extraction processing an extraction processing step of outputting, to extract processed data, by integrating only the interval of more than 1 for each section, and calculates a one cross integration value, the one cross-integral value Including a one cross-integration processing step of outputting Wath integrated data, and the S / N ratio calculation process step of calculating a signal S / N ratio of the target echo from the integration data.

  According to the present invention, it is possible to calculate a signal S / N ratio in which a blind zone caused by a sudden strong signal does not occur.

It is a block diagram which shows the whole structure of the active sonar signal processing part (signal S / N ratio calculation part) in the active sonar apparatus which concerns on one embodiment of this invention. It is a figure which shows the example of input data (correlation process result) for showing the effectiveness of this invention. FIG. 3 is an enlarged view of an echo portion of an example of input data (correlation processing result) in FIG. 2. It is a figure which shows the example which showed the trouble at the time of using a conventional method. It is a figure which shows the actual example of the differential data (differentiation process result) obtained by performing a differentiation process with the differentiation process part with respect to the input data (correlation process result) shown in FIG. FIG. 6 is a diagram illustrating an example of post-extraction processing data (extraction processing result) obtained by performing extraction processing on the input data (differential processing result) illustrated in FIG. 5 by an extraction processing unit. It is a figure which shows the actual example of the integration data (one cross integration process result) obtained by performing a one cross integration process by the one cross integration process part with respect to the input data (extraction process result) shown in FIG. Signal S / N ratio data (signal S / N ratio calculation processing) obtained by performing S / N ratio calculation processing by the S / N ratio calculation processing unit on the input data (one-cross integration processing result) shown in FIG. It is a figure which shows the example of a result.

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

  Although not shown, an active sonar device to which the embodiment of the present invention is applied receives a transmitter that converts a transmission signal into a sound wave and transmits the underwater acoustic signal including a reflected sound wave from a target. A receiver that converts the received signal, a replica correlation processing unit that performs the replica correlation processing using the received signal as a replica signal and outputs a replica correlation processing result, and a target echo from the replica correlation processing result And a signal S / N ratio calculation unit for calculating the signal S / N ratio of

  The present invention relates to an improvement of a signal S / N ratio calculation unit in an active sonar device. The signal S / N ratio calculation unit is called an active sonar signal processing unit.

[Description of configuration]
FIG. 1 is a block diagram showing the overall configuration of an active sonar signal processing unit according to an embodiment of the present invention.

  The active sonar signal processing unit according to the embodiment of the present invention includes a differentiation processing unit 1, an extraction processing unit 2, a one-cross integration processing unit, and an S / N ratio calculation processing unit 4.

  The differential processing unit 1 calculates an increase / decrease ratio of the signal level of the replica correlation processing result, and outputs differential data. More specifically, the differential processing unit 1 calculates the signal increase / decrease ratio between the time t and the time t + Δt with respect to the replica correlation processing result of the data in a specific direction (reception channel) received by the active sonar device, Differential data representing the signal increase / decrease ratio is output.

  The extraction processing unit 2 extracts only the positive change amount from the differential data and outputs the post-extraction processing data. More specifically, the extraction processing unit 2 forcibly sets a value less than 1.0 to 1.0 for the differential data, and extracts only a positive change amount.

  The one-cross integration processing unit 3 calculates the one-cross integration value from the extracted data, and outputs integration data representing the one-cross integration value. In other words, the one-cross integration processing unit 3 calculates the one-cross integration value by integrating the extracted data after every interval exceeding 1.

  The S / N ratio calculation processing unit 4 calculates the signal S / N ratio of the target echo from the integration data. More specifically, the S / N ratio calculation processing unit 4 calculates a decibel value (= 20 log (integral value)) with respect to the integral data to thereby calculate a signal S / N ratio in the time axis direction of a specific direction (reception channel). Is calculated.

[Description of operation]
Next, the operation of the active sonar signal processing unit shown in FIG. 1 will be described.

  The differential processing unit 1 calculates a signal increase / decrease ratio in the time axis direction according to the following formula 1, and outputs differential data.

ここで、t：時刻 Δｔ：時間分解能である。

Here, t: time Δt: time resolution.

  The extraction processing unit 2 compulsorily sets a value less than 1.0 to 1.0 according to the following formula 2 for the differential data, and extracts only a positive change amount.

  The one-cross integration processing unit 3 performs integration for each section where the signal increase ratio exceeds 1.0 according to the following formula 3, and calculates the total increase ratio (one-cross integration value).

  The S / N ratio calculation processing unit 4 calculates a signal S / N ratio in the time axis direction by calculating a decibel value (= 20 log (integral value)) according to the following equation (4).

  Next, an embodiment of the active sonar signal processing unit shown in FIG. 1 will be described.

  It is assumed that a replica correlation processing result between a transmission signal (replica signal) and a reception signal is input from a distance 0 [yd] to 2500 [yd] in a specific direction (reception channel).

  FIG. 2 is a diagram showing the replica correlation processing result (input data). In FIG. 2, the horizontal axis indicates the distance [yd], and the vertical axis indicates the voltage [V].

  FIG. 3 is an enlarged view showing the echo portion of FIG. In FIG. 3, the part of distance 1500 [yd]-25000 [yd] of FIG. 2 is expanded. It can be seen from FIG. 3 that there are two echo signals, Echo 1 and Echo 2. Echo 1 is present at approximately 2000 [yd], and Echo 2 is present at approximately 2400 [yd].

  The differential processing unit 1 calculates the signal increase ratio according to the above-described formula 1.

  FIG. 5 is a diagram showing differential data (partial processing result) obtained by the differential processing unit 1. In FIG. 5, the horizontal axis indicates the distance [yd], and the vertical axis indicates the signal increase ratio.

  The extraction processing unit 2 extracts only the positive change amount by the above-described formula 2.

  FIG. 6 is a diagram illustrating post-extraction data (extraction process result) obtained by the extraction processing unit 2. In FIG. 6, the horizontal axis indicates the distance [yd], and the vertical axis indicates the signal increase ratio.

  The one-cross integration processing unit 3 performs integration for each section in which the signal increase ratio exceeds 1.0 according to the above-described Equation 3, and calculates the total increase ratio.

  FIG. 7 is a diagram showing integration data (one-cross integration processing result) obtained by the one-cross integration processing unit 3. In FIG. 7, the horizontal axis represents the distance [yd], and the vertical axis represents the total signal increase ratio.

  The S / N ratio calculation processing unit 4 calculates a decibel value by the above-described equation 4.

  FIG. 8 is a diagram illustrating a signal S / N ratio calculation processing result obtained by the S / N ratio calculation processing unit 4. In FIG. 8, the horizontal axis indicates the distance [yd], and the vertical axis indicates the signal S / N ratio [dB]. From FIG. 8, it can be seen that the echo 1 exists at about 2000 [yd] and the echo 2 exists at about 2400 [yd]. Further, from FIG. 8, in the present embodiment, even an echo of about 1 dB can be calculated.

  The effect of this embodiment (example) will be described.

  By performing the S / N ratio calculation process using this embodiment (example), a blind zone caused by a sudden strong signal does not occur, and even a signal S / N ratio of about 1 dB is detected. It becomes possible to do. The reason is that, in the processing in this embodiment (example), the signal increase / decrease ratio in the time axis direction is directly calculated by differential processing, not the processing of estimating the background noise level or the like from the input data, and the positive change by the extraction processing Only the amount is extracted, the total increase ratio is calculated by the one-cross integration process, the decibel conversion is performed on the total increase ratio by the S / N ratio calculation process, and the signal S / N ratio in the time axis direction is calculated. Because. That is, it is possible to directly calculate the increase ratio of the signal level in the input data without estimating the noise level or the like.

  The active sonar signal processor (signal S / N ratio calculator) shown in FIG. 1 can be realized by a computer. As is well known, the computer includes a central processing unit (CPU), a storage device such as a RAM for storing data, and a program memory (ROM) for storing a program. Then, by reading the program stored in the program memory (ROM), the CPU performs the functions of the differentiation processing unit 1, the extraction processing unit 2, the one-cross integration processing unit 3, and the S / N ratio calculation processing unit 4. Realize.

  As mentioned above, although this invention was demonstrated with reference to embodiment (Example), this invention is not limited to the said embodiment (Example). Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

  A part or all of the above embodiment can be described as in the following supplementary notes, but is not limited to the following.

(Supplementary note 1) A transmitter that converts a transmission signal into a sound wave and transmits it, a receiver that receives an underwater acoustic signal including a reflected sound wave from a target and converts it into a reception signal, and the reception signal A replica correlation processing unit that performs replica correlation processing using the transmission signal as a replica signal and outputs a replica correlation processing result, and a signal S / N that calculates a signal S / N ratio of a target reverberation sound from the replica correlation processing result In an active sonar device configured with an N ratio calculation unit, the signal S / N ratio calculation unit includes:
A differential processing unit for calculating an increase / decrease ratio of the signal level of the replica correlation processing result and outputting differential data;
An extraction processing unit that extracts only positive variation from the differential data and outputs data after extraction processing;
A one-cross integration processing unit that calculates a one-cross integration value from the extracted data and outputs integration data representing the one-cross integration value;
An S / N ratio calculation processing unit for calculating the signal S / N ratio of the target echo from the integrated data;
An active sonar device comprising:

(Additional remark 2) The said differential process part calculates the increase / decrease ratio with respect to the data of the time t and the time t + (DELTA) t ((DELTA) t: time resolution) with respect to the said replica correlation process result for every receiving channel (reception direction). The active sonar device according to appendix 1, characterized by:

(Supplementary note 3) In the supplementary note 1 or 2, the extraction processing unit forcibly sets a value less than 1.0 to 1.0 and extracts only a positive change amount with respect to the differential data. The active sonar device described.

(Supplementary Note 4) The one-cross integration processing unit calculates the one-cross integral value by integrating only the sections exceeding 1 for each piece of the post-extraction processing data. 4. The active sonar device according to any one of items 1 to 3.

(Supplementary Note 5) The S / N ratio calculation processing unit calculates a decibel value (= 20 log (integral value)) with respect to the integral data to thereby calculate the signal S / in the time axis direction of a specific direction (reception channel). The active sonar device according to any one of appendices 1 to 4, wherein an N ratio is calculated.

(Supplementary Note 6) A signal processing method for calculating a signal S / N ratio from a replica correlation processing result obtained by replica correlation processing between a replica signal of a transmission signal and a reception signal,
A differential processing step of calculating a signal level increase / decrease ratio of the replica correlation processing result and outputting differential data;
An extraction process step of extracting only positive change amount from the differential data and outputting post-extraction data;
A one-cross integration processing step of calculating the one-cross integration value from the extracted data and outputting integration data representing the one-cross integration value;
An S / N ratio calculation processing step of calculating the signal S / N ratio of the target echo from the integral data;
A signal processing method comprising:

(Additional remark 7) The said differentiation process step calculates the increase / decrease ratio with respect to the data of the time t and the time t + (DELTA) t ((DELTA) t: time resolution) with respect to the said replica correlation process result for every receiving channel (reception direction). The signal processing method according to appendix 6, wherein:

(Supplementary note 8) In the supplementary note 6 or 7, the extraction processing step forcibly sets a value less than 1.0 to 1.0 and extracts only a positive change amount with respect to the differential data. The signal processing method as described.

(Supplementary note 9) The supplementary note 6 is characterized in that the one-cross integration processing step calculates the one-cross integral value by integrating only the intervals exceeding 1 for each piece of the post-extraction processing data. The signal processing method of any one of thru | or 8.

(Supplementary Note 10) The S / N ratio calculation processing step calculates the decibel value (= 20 log (integral value)) for the integral data, thereby the signal S / in the time axis direction of a specific direction (reception channel). 10. The signal processing method according to any one of appendices 6 to 9, wherein an N ratio is calculated.

(Supplementary note 11) A signal processing program for causing a computer to calculate a signal S / N ratio from a replica correlation processing result obtained by replica correlation processing between a replica signal of a transmission signal and a reception signal,
A differential process for calculating an increase / decrease ratio of the signal level of the replica correlation processing result and outputting differential data;
An extraction process for extracting only the positive change amount from the differential data and outputting the data after the extraction process;
One-cross integration processing for calculating the one-cross integration value from the extracted data, and outputting integration data representing the one-cross integration value;
S / N ratio calculation processing for calculating the signal S / N ratio of the target echo from the integration data;
Signal processing program for executing

(Additional remark 12) The said differentiation process makes the said increase / decrease ratio with respect to the data of the time t and the time t + (DELTA) t ((DELTA) t: time resolution) with respect to the said replica correlation process result for every receiving channel (reception direction) to the said computer. The signal processing program according to appendix 11, wherein the signal processing program is calculated.

(Additional remark 13) The said extraction process makes the said computer force the value below 1.0 to 1.0 with respect to the said differential data, It is made to extract only a positive variation | change_quantity, The additional remark 11 characterized by the above-mentioned. Or the signal processing program of 12.

(Supplementary Note 14) The one-cross integration process is characterized in that the computer calculates the one-cross integration value by integrating only the sections exceeding 1 with respect to the data after the extraction process for each section. The signal processing program according to any one of appendices 11 to 13.

(Supplementary Note 15) In the S / N ratio calculation process, the computer calculates the decibel value (= 20 log (integral value)) with respect to the integral data, so that the specific direction (reception channel) in the time axis direction is 15. The signal processing program according to any one of appendices 11 to 14, wherein the signal S / N ratio is calculated.

The present invention has a possibility of being used in a signal processing function relating to an active sonar device.

1 differential processing unit 2 extraction processing unit 3 one-cross integration processing unit 4 S / N ratio calculation processing unit

Claims (4)

A transmitter that converts a transmission signal into a sound wave and transmits it, a receiver that receives an underwater acoustic signal including a reflected sound wave from a target, and converts it into a reception signal; and the reception signal, A replica correlation processing unit that performs replica correlation processing using a transmission signal as a replica signal and outputs a replica correlation processing result, and a signal S / N ratio calculation unit that calculates a signal S / N ratio of a target echo sound from the replica correlation processing result And the signal S / N ratio calculation unit includes:
An increase / decrease ratio of the signal level obtained by dividing the data of time t + Δt (Δt: time resolution) by the data of time t with respect to the replica correlation processing result for each reception channel (reception direction) , and the signal level the increase or decrease ratio and differential processing unit for outputting a differential data,
An extraction processing unit that forcibly sets a value less than 1.0 to 1.0 for the differential data , extracts only a positive change amount in a direction in which the signal level increases, and outputs data after extraction processing; ,
A one-cross integration processing unit that calculates a one-cross integral value by integrating only the section exceeding 1 for each section after the extraction processing, and outputs integral data representing the one-cross integral value;
An S / N ratio calculation processing unit for calculating the signal S / N ratio of the target echo from the integrated data;
An active sonar device comprising: The S / N ratio calculation processing unit calculates the signal S / N ratio in the time axis direction of a specific direction (reception channel) by calculating a decibel value (= 20 log (integration value)) for the integration data. The active sonar device according to claim 1 , wherein: A signal processing method for calculating a signal S / N ratio from a replica correlation processing result obtained by replica correlation processing between a replica signal of a transmission signal and a reception signal,
An increase / decrease ratio of the signal level obtained by dividing the data of time t + Δt (Δt: time resolution) by the data of time t with respect to the replica correlation processing result for each reception channel (reception direction) , and the signal level A differential processing step for outputting the increase / decrease ratio of as differential data;
An extraction processing step for forcibly setting a value less than 1.0 to 1.0 for the differential data , extracting only a positive change amount in a direction in which the signal level increases, and outputting post-extraction data; ,
A one-cross integration processing step of calculating a one-cross integration value by integrating only the section exceeding 1 for each piece of the post-extraction processing data, and outputting integration data representing the one-cross integration value;
An S / N ratio calculation processing step of calculating the signal S / N ratio of the target echo from the integral data;
A signal processing method comprising: The S / N ratio calculation processing step calculates the signal S / N ratio in the time axis direction of a specific direction (reception channel) by calculating a decibel value (= 20 log (integral value)) with respect to the integral data. The signal processing method according to claim 3 , wherein:

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