JPH1138127A - Device and method for detecting target in reverberation and recording medium having recorded in-reverberation target detecting program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable an active SONAR device to effectively extract reflected signals from a target in reverberation. SOLUTION: The disclosed active SONAR device is provided with a TVG (time variable gain) amplifying section 4, which sends transmitting signals composed of electric signals to the underwater after converting the signals into acoustic signals, converts underwater acoustic signals into received signals composed of electric signals, and performs gain correction on the received signals based on the time-sequential damping characteristic of reverberation and detects a target from the output of the amplifier section 4. The SONAR device is also provided with a signal processing means 7a which performs target detection from the output error between white noise identified with the reverberation output of the amplifying section 4 and the output of the section 4 based on the received signals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for detecting a target in a reverberation and a storage medium storing a program for detecting a target in a reverberation. The present invention relates to an apparatus and a method for detecting a target within reverberation, and a storage medium storing a program for detecting a target within reverberation.

[0002]

2. Description of the Related Art In an active sonar apparatus, the direction, distance, shape, and the like of a target in water are detected by transmitting an acoustic signal into the water and receiving a reflected signal from the target. At this time, since there is reflection (hereinafter referred to as reverberation) from the sea surface, the sea floor, or a microorganism in the sea, detection of a reflected signal from a target object may be hindered. Therefore, on the receiving side, it is necessary to suppress reverberation and effectively extract a reflected signal from a target object from within the reverberation,
For this purpose, various reverberation target detection apparatuses have been proposed.

[0003] Conventionally, as a target detecting device for reverberation of this kind, as disclosed in Japanese Patent Application Laid-Open No. 1-280273, for example, a time variable gain (TVG) amplifier is used to generate a time series of signal levels of reverberation. In some cases, the attenuation characteristic is compensated and the reverberation is suppressed using a variable band rejection filter (notch filter), thereby helping to improve the target signal detection capability.

FIG. 5 is a block diagram schematically showing an electrical configuration of the target detection apparatus in reverberation described in the publication. This target apparatus for detecting a target within reverberation includes a transmission signal generation unit 1, an amplification unit 2, a transmission / reception unit 3, a TVG amplification unit 4, a band rejection filter 5
And a target detection unit 6. The transmission signal generator 1 generates an electric signal that is an original signal of an active sonar transmission wave. The amplification unit 2 includes a transmission signal generation unit 1
To amplify the output signal to generate a transmission signal. Transceiver 3
Converts a transmission signal consisting of an electric signal into an acoustic signal,
The signal is transmitted underwater, and the underwater acoustic signal is received and converted into a reception signal composed of an electric signal. The TVG amplifier 4
The gain of the received signal is corrected based on the reverberation time-series attenuation characteristics, and the received signal is amplified.

The band rejection filter 5 is composed of a variable band rejection filter such as a notch filter, for example.
The output of the G amplifying unit 4 suppresses frequency components in a reverberation band. The reverberation frequency usually has a certain band spread with respect to the transmission frequency. The frequency band, attenuation rate, and the like of the band rejection filter 5 may be variable. The target detecting unit 6 outputs an output signal indicating target detection to a received signal in which the attenuation characteristic is corrected and the frequency component of the reverberation band is suppressed, by a change in the signal level, and the like, based on the direction of the transducer, Occurs according to the reception delay time corresponding to the target distance.

[0006] In the prior art shown in FIG.
Stabilization of the received signal level by the G amplifying unit, etc.
The reverberation band in the received signal is suppressed by a filter or the like, but the attenuation characteristic (TVG characteristic) of the TVG amplifier is used.
Also, the filter coefficient value that determines the frequency characteristic of the notch filter is fixedly determined, or a plurality of characteristic values are switched and used.

[0007] As another method, a neural network having a learning ability is used in an active sonar device when using a frequency-modulated ultrasonic wave as a transmission signal and detecting a reflected wave from a target from a received signal. Be prepared, by performing pattern recognition of the received information,
There has been proposed an apparatus for discriminating whether a received signal is a reflected wave from a target or a reverberation based on a minute difference in the structure of the received signal (for example, Japanese Patent Application Laid-Open No. 5-29711).
No. 4).

[0008]

However, in the former prior art, it was difficult to remove the effect of reverberation from the received signal and to reliably detect the target signal. This is because, despite the fact that the signal level and frequency characteristics of reverberation change every moment in accordance with the marine environment, the processing performed as a reverberation countermeasure is performed using the characteristics assumed in advance. Is attributed to Also, in the latter conventional technique, a complex and underdeveloped device such as a neural network having learning ability is used.
It is inevitable that the active sonar device becomes complicated and becomes an expensive and large-scale device.

The present invention has been made in view of the above-described circumstances, and has been developed in spite of a change in the state of the marine environment and the like.
It is an object of the present invention to provide a reverberation target detection apparatus and method capable of performing stable reverberation target detection, and a storage medium storing a reverberation target detection program.

[0010]

In order to solve the above-mentioned problems, a target detection apparatus for reverberation according to the present invention converts a transmission signal composed of an electric signal into an acoustic signal and transmits the signal to the underwater, and transmits the underwater acoustic signal. A gain correction unit that converts the signal into a reception signal composed of an electric signal and performs gain correction on the reception signal based on a reverberation time-series attenuation characteristic, and performs target detection based on an output of the gain correction unit; The active sonar device is characterized in that signal processing means for performing target detection based on an error output between the white noise identified as the reverberation output of the gain correction means and the output of the gain correction means based on the received signal is provided.

According to a second aspect of the present invention, in the reverberation target detecting apparatus according to the first aspect, the signal processing means comprises:
White noise generating means for generating white noise, an adaptive band-pass filter for identifying the white noise with respect to the reverberation signal output of the gain correcting means, and an error between the output of the gain correcting means and the output of the adaptive band-pass filter Subtraction means for determining
Filter coefficient control means for sequentially optimizing filter coefficients of the adaptive band-pass filter according to the error output; and target detection means for generating an output signal indicating target detection when the error output exceeds an arbitrary threshold value It is characterized by comprising.

According to a third aspect of the present invention, there is provided the apparatus for detecting an intra-reverberation target according to the second aspect, wherein the white noise is provided between the output of the white noise generating means and the input of the adaptive band-pass filter. It is characterized in that a band-pass filter for limiting is inserted.

According to a fourth aspect of the present invention, there is provided a method for detecting a target within reverberation, comprising the steps of: converting a transmission signal comprising an electric signal into an acoustic signal and transmitting the signal into water; and converting the underwater acoustic signal into a reception signal comprising an electric signal. Performing a gain correction on the received signal based on a reverberation time-series attenuation characteristic; generating white noise; and identifying the white noise as received reverberation by an adaptive band-pass filter. Subtracting the output of the adaptive bandpass filter from the gain-adjusted received signal; sequentially optimizing the filter coefficients of the adaptive bandpass filter using an error of the subtracted output; Generating an output signal indicating the target detection based on the error of (i).

According to a fifth aspect of the present invention, there is provided the method for detecting a target within reverberation according to the fourth aspect, wherein after the step of generating the white noise, the white noise is passed through a band-pass filter to thereby adjust the adaptive band. It is characterized by including a step of inputting to a pass filter.

According to a sixth aspect of the present invention, there is provided a recording medium storing a reverberation target detection program for detecting a reverberation target in an active sonar apparatus by a computer.
A transmission signal composed of an electric signal is converted into an acoustic signal and transmitted to the water, an acoustic signal in the water is converted into a received signal composed of an electric signal, and the received signal is gained based on a reverberation time-series attenuation characteristic. The adaptive band-pass filter is corrected by an error signal obtained by subtracting the output of the adaptive band-pass filter from the received signal after the gain adjustment while generating white noise and passing the adaptive band-pass filter. By successively optimizing coefficients, white noise after passing through the adaptive band-pass filter is assimilated into the reverberation signal after the gain correction, and an output signal indicating target detection is generated by an instantaneous output of the subtraction error. And

According to a seventh aspect of the present invention, there is provided a storage medium storing the reverberation target detection program according to the sixth aspect, wherein the program causes a computer to pass the generated white noise through a band-pass filter. And inputting the signal to the adaptive band-pass filter.

[0017]

According to the present invention, a white noise identified as a reverberation output of a gain correction means such as a TVG amplifier and the like and an output of the gain correction means based on a received signal are provided for reverberation which changes momentarily according to the marine environment. The target detection is performed by the error output of. For example, by identifying an adaptive band-pass filter (ie, simulating the marine environment by the adaptive band-pass filter), a reverberation prediction signal is obtained as an output of the adaptive band-pass filter. To detect the instantaneous error signal to detect the target. Therefore, according to the present invention, an output signal indicating target detection other than reverberation components included in a received signal can be extracted without being affected by the marine environment.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. The description will be made specifically using an embodiment. First Embodiment FIG. 1 is a block diagram showing an electric configuration of a reverberation target detection apparatus according to a first embodiment of the present invention. As shown in FIG. 1, the target detection device for reverberation in this example includes a transmission signal generator 1, an amplifier 2, a transmitter / receiver 3, and a TVG amplifier 4.
And a signal processing means 7a. The transmission signal generator 1 generates an electric signal that is an original signal of a transmission wave in the active sonar device. The amplification unit 2
The output signal of the transmission signal generator 1 is amplified to a required power level. The transmission / reception unit 3 is formed of an electro-acoustic converter, converts a transmission signal into an acoustic signal and sends the signal underwater, and converts an underwater acoustic signal into an electric signal to be a reception signal. As shown in FIG. 1, the signal processing means 7a includes a white noise generator 8, an adaptive bandpass filter 9, and a subtractor 10.
And a target detection unit 12 and a filter coefficient control unit 12. The white noise generator 8 generates white noise, which is a signal having a uniform spectrum over an infinite frequency range. The adaptive bandpass filter 9 is
It is a bandpass filter whose passband characteristics can be adaptively determined by controlling its filter coefficients.
The subtracter 10 subtracts the output signal of the adaptive bandpass filter 9 from the output signal of the TVG amplifier 4 to generate an error output. When the error output from the subtraction unit 10 exceeds an arbitrary threshold, the target detection unit 12 outputs an output signal indicating target detection according to the direction of the transducer 3 and the reception delay time corresponding to the target distance. Occur. The filter coefficient control unit 12
According to the error output from the subtraction unit 10, the filter coefficients of the adaptive bandpass filter 9 are successively optimally controlled.

Next, the operation of this example will be described with reference to FIGS. FIG. 2 is a flowchart showing the operation processing procedure of this example, and FIG. 3 is a waveform chart showing signals of various parts in the configuration of FIG. Transmission signal generator 1
Generates an electric signal that is an original signal of the transmission wave in the active sonar device (step SP101),
Amplifies the output signal of the transmission signal generator 1 to a required power level (step SP102) and supplies the signal to the transmission / reception unit 3 as a transmission signal composed of an electric signal. The transmitting / receiving section 3
The transmission signal is converted into an acoustic signal and transmitted into the water (step SP103), and the underwater acoustic signal is converted into a reception signal which is an electric signal (step SP104) and output.

The attenuation characteristic of the received signal is affected by the water depth, the sea state (wind class), the state of the microorganisms in the sea, and the like. The effect is, as shown in FIG. Appears as fluctuations. Since the TVG amplifier 4 corrects the received signal level based on the basic attenuation characteristic that can be assumed in advance (step SP105), in the corrected received signal, a level change based on the basic reverberation attenuation characteristic is removed. However, the level change based on the variation of the basic attenuation characteristic described above remains as shown in FIG.

On the other hand, the white noise generator 8 receives the signal from the transmitter / receiver 3 (step SP103),
The white noise is generated in parallel with the attenuation correction in (step SP105) (step SP106). The adaptive band-pass filter 9 performs an operation of identifying the white noise generated by the white noise generator 8 (step SP106) with respect to the reception reverberation after the attenuation characteristic correction from the TVG amplifier 4 (step SP107). The subtractor 10 subtracts the reverberation received from the TVG amplifier 4 and the white noise from the adaptive bandpass filter 9 (step S).
P108) Obtain an error value. Note that the output from the adaptive bandpass filter 9 has the same frequency and phase as the reverberation received from the TVG amplifier 4 after the adaptive bandpass filter 9 is optimally controlled. Filter coefficient control unit 12
, The filter coefficient of the adaptive band-pass filter 9 is calculated such that the error value from the subtraction unit 10 becomes the minimum in the next subtraction, and the feedback control is performed by setting the filter coefficient in the adaptive band-pass filter 9. Then, the characteristics of the adaptive band-pass filter 9 are optimized (step SP109), and the output of the adaptive band-pass filter 9 changes with the lapse of time t (t0, t1, t2) in FIG.
As shown in FIG. 3B, the signal level is identified as the signal level of the reverberation reception, and the frequency characteristics are also identified as shown in FIGS. 3C and 3D.

When such identification is completed (FIG. 4)
From (t2) of (b), the adaptive bandpass filter 9 simulates the marine environment affecting reverberation, and the output of the adaptive bandpass filter 9 becomes a reverberation prediction signal. On the contrary,
The instantaneous target signal during the received reverberation with respect to the reverberation prediction signal of the identification result appears as an error signal. The adaptive bandpass filter 9 attempts to identify this error signal as well,
Since there is a delay in the identification operation, the error signal is output from the subtraction unit 10 and supplied to the target detection unit 12. When the error signal exceeds an arbitrary threshold value, the target detection unit 12 performs target detection (step SP110), and outputs an output signal indicating the target detection to the direction of the transducer and the reception delay time corresponding to the target distance. Output according to.

As described above, according to the configuration of this example, when extracting a reflected signal from a target in reverberation, a reverberation characteristic is predicted using an applied band-pass filter. Despite a change in the marine environment or the like that greatly affects characteristics, detection of a target in reverberation can be stably performed.

Second Embodiment FIG. 4 is a block diagram showing an electrical configuration of a reverberation target detecting apparatus according to a second embodiment of the present invention. The configuration of this example is significantly different from that of the first embodiment described above in that the band-pass filter 13 is provided between the white noise generator 8 and the adaptive band-pass filter 9 in the signal processing means 7b.
Is interposed. The other points are substantially the same as those in the first embodiment, and therefore, in FIG.
The same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

In this example, the band pass filter 13
Performs an operation of restricting the white noise from the white noise generator 8 in accordance with the sonar reception band and inputting the band noise to the adaptive band-pass filter 9.

According to the configuration of the second embodiment, the band of the signal input to the adaptive band-pass filter 9 is reduced, and as a result, the adaptive time of the adaptive band-pass filter 9 is shortened.
The identification time for the reception reverberation of the adaptive bandpass filter 9 can be reduced.

Although the embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and there are design changes and the like that do not depart from the gist of the present invention. Are also included in the present invention. For example, the target device for detecting reverberation in reverberation of this example may be entirely or partially configured as a hardware or may be configured as software. The signal processing units 7a and 7b) include a CPU (central processing unit), an internal storage device such as a ROM and a RAM, and an FDD.
(Flexible disk driver), HDD (hard disk driver), a computer having an external storage device such as a CD-ROM driver, an input device such as a keyboard and a mouse, and a display device are preferable. It is preferable that a recording medium such as an FD (flexible disk), an HD (hard disk), or a CD-ROM has a reverberation target detection program for causing a computer to execute the processing of the above-described embodiment (FIG. 2). The recording medium may be a semiconductor memory or another recording medium. In such a configuration, the reverberation target detection program is read into the computer from the recording medium, and controls the operation of the computer. Computer
When the intra-reverberation target detection program runs, it functions as an adaptive band-pass filter, a subtraction unit, a target detection unit 11, a filter count control unit 12, and the like.

[0028]

As described above, according to the configuration of the present invention, in the active sonar apparatus, when extracting the reflected signal from the target in the reverberation, the signal processing means is provided, and the gain of the TVG amplifier or the like is provided. The target detection is performed based on the error output between the white noise identified as the reverberation output of the correction unit and the output of the gain correction unit based on the received signal. In this case, for example, prediction of the reverberation characteristics is performed using an adaptive bandpass filter. The target detection is performed by generating white noise identified in the reverberation output of the gain correction means. Target detection can be performed stably.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an electrical configuration of a first embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of the embodiment.

FIG. 3 is a waveform chart showing signals of respective parts in the embodiment.

FIG. 4 is a block diagram showing an electrical configuration of a second embodiment of the present invention.

FIG. 5 is a block diagram illustrating an electrical configuration of a conventional in-reverberation target detection apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transmission signal generation part 2 Amplification part 3 Transmission / reception part 4 TVG amplification part (gain correction means) 7a, 7b Signal processing means 8 White noise generation part (white noise generation means) 9 Adaptive bandpass filter 10 Subtraction part (subtraction means) DESCRIPTION OF SYMBOLS 11 Target detection part (target detection means) 12 Filter coefficient control part (filter coefficient control means) 13 Band-pass filter

Claims (7)

[Claims] 1. A transmission signal composed of an electric signal is converted into an acoustic signal and transmitted to the underwater, and the underwater acoustic signal is converted into a received signal composed of an electric signal. In an active sonar apparatus comprising a gain correction means for performing gain correction based on characteristics and performing target detection by an output of the gain correction means, based on a white noise identified as a reverberation output of the gain correction means and a received signal. A reverberation target detection apparatus, comprising: signal processing means for performing target detection based on an error output from gain correction means output. 2. The signal processing means comprising: a white noise generating means for generating white noise; an adaptive band-pass filter for identifying the white noise with respect to a reverberation signal output of the gain correcting means; Subtraction means for obtaining an error between the output and the output of the adaptive band-pass filter; filter coefficient control means for sequentially optimizing the filter coefficients of the adaptive band-pass filter in accordance with the error output; 2. A reverberation-in-reverberation target detecting apparatus according to claim 1, further comprising target detecting means for generating an output signal indicating target detection when the value is exceeded. 3. A target in reverberation according to claim 2, wherein a band-pass filter for band-limiting the white noise is inserted between an output of the white noise generating means and an input of the adaptive band-pass filter. Detection device. 4. A step of converting a transmission signal consisting of an electric signal into an acoustic signal and sending the signal underwater, a step of transforming the underwater acoustic signal into a reception signal consisting of an electric signal, and Performing gain correction based on a time-series attenuation characteristic, generating white noise, identifying the white noise as received reverberation by an adaptive band-pass filter, and performing the adaptation from the received signal after the gain adjustment. Subtracting the output of the band-pass filter, sequentially optimizing the filter coefficients of the adaptive band-pass filter using the error of the subtracted output, and generating an output signal indicating target detection by the error of the subtracted output. A method for detecting a target in reverberation. 5. The reverberation target according to claim 4, further comprising a step of passing the white noise through a band-pass filter and inputting the white noise to the adaptive band-pass filter after the step of generating the white noise. Detection method. 6. A recording medium on which a program for detecting a target in reverberation in an active sonar device by a computer is recorded. The program converts a transmission signal composed of an electric signal into an acoustic signal by a computer. It is transmitted to the water, the underwater acoustic signal is converted into a received signal composed of an electric signal, and the received signal is subjected to gain correction based on a reverberation time-series attenuation characteristic, and white noise is generated to generate an adaptive band. The adaptive bandpass filter is successively optimized by an error signal obtained by subtracting the output of the adaptive bandpass filter from the received signal after the gain adjustment while passing the signal through the passband filter. The white noise after passing through the filter is assimilated into the reverberation signal after the gain correction, and the target is detected by the instantaneous output of the subtraction error. Storage medium in which a reverberation within the target detection program characterized by generating an output signal indicative. 7. The program according to claim 6, wherein the program causes the computer to cause the generated white noise to pass through a band-pass filter and input to the adaptive band-pass filter. Storage media.