JP3576890B2 - Sonar device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a sonar device, and particularly to a sonar device having a reverberation suppression circuit immediately after transmission to underwater or the like.
[0002]
2. Description of the Related Art A sonar device that transmits a sound wave to a target such as underwater and receives a reflected wave from the target such as a school of fish to detect the presence, position, size, and the like of the target is widely used. In addition, a sonar device having a reverberation suppressing unit in water immediately after transmission is also well known, and is disclosed, for example, in "Active sonar device" in JP-A-4-116488. FIG. 6 shows a block diagram of such a conventional technique.
[0003]
The sonar device shown in FIG. 6 includes a transmission circuit 1, a transducer 3, an amplification circuit 5, a reverberation suppression circuit 7, and a phasing circuit 9. The reverberation suppression circuit 7 includes a multiplication circuit 71, a filter circuit 72, an A / D (analog-digital) converter 73, a detection circuit 74, a time division switching circuit 75, three time division integration circuits 76a, 76b, 76c (hereinafter collectively referred to as 76), three memory circuits 77a, 77b, and 77c (hereinafter collectively referred to as 77), a timing pulse generation circuit 78, a time series switching circuit 79, a multiplication level conversion circuit 80 and D A / A (digital-analog) converter 81 is included.
[0004]
In a sonar device including such components, a transmission signal 2 output from a transmission circuit 1 is input to a transmitter / receiver 3, where it is converted into a sound wave and transmitted underwater. After that, the sound wave reflected by the target is received by the transducer 3. Here, it is converted into a transmission / reception signal 4 which is an electric signal. Then, the signal is amplified by an amplifier circuit 5 and output to a reverberation suppression (TVG: time variable gain) circuit 7 as an amplified output signal 6.
[0005]
The reverberation suppression circuit 7 limits the band of the amplified output signal 6 by the filter circuit 72. Then, the data is converted into digital data by the A / D conversion circuit 73 according to the output timing signal of the timing pulse generation circuit 78. Thereafter, the signal is detected by the detection circuit 74 and is output to the time division integration circuit 76 while being switched every unit time by the time division switching circuit 75 in accordance with the output timing signal of the timing pulse generation circuit 78. Then, it is integrated for each unit time and stored in the memory circuit 77.
[0006]
The time-division reverberation level integrated and stored for each time unit is switched by the time series switching circuit 79 for each elapsed time according to the output timing signal of the timing pulse generation circuit 78, and is output. Then, the signals are converted by the multiplication level conversion circuit 80 into conversion suppression levels corresponding to the respective levels. The converted conversion suppression level is converted to analog data by the D / A conversion circuit 81. Then, the multiplied signal is multiplied by the amplified signal output 6 in the multiplying circuit 71 and output to the phasing circuit 9 as the multiplied circuit output signal 8 in which reverberation is suppressed.
[0007]
[Problems to be solved by the invention]
The conventional sonar device described above has several problems. First, if the transmission level is reduced during the state where the detection is continuously performed by the sonar device, the suppression amount is too large, and the S / N (signal-to-noise ratio) deteriorates in the reception signal processing. Conversely, when the transmission level is increased, the amount of suppression is smaller than the reverberation level, and the received signal is saturated during reception processing. It is known that, when the sonar device transmits a transmission signal, the reverberation level generated greatly differs depending on the level of the transmission level as shown in FIG. In the conventional sonar device shown in FIG. 6, the reverberation suppression circuit 7 stores the integration result of the reverberation characteristics in the memory circuit 77 immediately after the previous transmission. Therefore, when the received signal level suddenly decreases as shown in FIG. 8, a large difference occurs in the suppression level due to a delay in following the integration result, resulting in excessive suppression as shown in FIG. This is because
[0008]
Second, as shown in FIG. 10, when an echo from a target is mixed in a received signal in a region where reverberation suppression is required immediately after transmission, the target device echo itself is used in the conventional apparatus of FIG. Is erroneously recognized as a signal level to be suppressed, resulting in a reverberation suppression processing result as shown in FIG. 11, which adversely affects the reception processing. The reason is that, in the conventional device shown in FIG. 6, the received signal is integrated in the time-division integrator circuit 76 and stored in the memory circuit 77 every time lapse, and the reverberation level is used for the received signal using the stored reverberation level. This is a configuration for performing suppression. If the target remains at the same position at a short distance, the echo of the target itself is output as the suppression level as a result of the integration processing. As a result, the output suppression amount is processed not for the target reverberation but for the target echo, and the signal level of the target echo is reduced to make the reception processing difficult.
[0009]
Third, in the case of the conventional device, the circuit scale is relatively large, and miniaturization is difficult and expensive. The reason is that the reception signal is stored by switching every time, and it is necessary to have the time division integration circuit 76 and the memory circuit 77 for every switching time for time division.
[0010]
[Object of the invention]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a sonar device that overcomes or improves the above-described various problems in the above-described reverberation suppression process of the conventional sonar device.
[0011]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the sonar device according to the present invention employs the following characteristic configuration.
[0016]
( 1 ) an average value calculation circuit that measures a received signal of a sound wave including reverberation after transmitting the sound wave to underwater, measures a reverberation level immediately after transmission, and outputs an average value per unit time;
An A / D conversion circuit for A / D converting the average value and outputting digital data;
A suppression characteristic memory circuit for determining a start address based on a reverberation level immediately after transmission equal to the digital data and reading out a previously stored suppression characteristic as a reverberation suppression signal;
A multiplication circuit for controlling an input signal by the reverberation suppression signal.
[0017]
( 2 ) A reverberation suppression characteristic using time as an address for a suppression amount from immediately after transmission to a certain time later is stored in a memory in advance, and a start position of the suppression level is determined from a reverberation level in a received signal immediately after transmission. A sonar device for reading reverberation suppression characteristics from the memory from an address corresponding to the start position to suppress reverberation.
[0018]
(3) dereverberation characteristics the storage, from the maximum level reverberation level value of expected when transmitting the maximum transmission level was up to the reverberation level value when sufficient time after the transmission has passed above (2) Sonar equipment.
[0019]
( 4 ) The sonar apparatus according to ( 2 ), wherein the reverberation level in the received signal immediately after transmission for determining the start address of the suppression level is an average value of the reverberation levels.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the configuration and operation of a preferred embodiment of the sonar device according to the present invention will be described in detail.
[0021]
FIG. 1 shows a block diagram of a preferred embodiment of a sonar device according to the invention. The same reference numerals are used for the components corresponding to the components in FIG. 6 for convenience. This sonar device includes a transmission circuit 1, a transducer 3, an amplification circuit 5, a reverberation suppression circuit 7, and a phasing circuit 9. The reverberation suppression circuit 7 is the same as the sonar device of FIG. 6 in that it includes a multiplication circuit 71, a filter circuit 72, a detection circuit 74, an A / D conversion circuit 73, a timing pulse generation circuit 78, and a D / A converter 81. It is. However, the reverberation suppression circuit 7 of the sonar device of the present invention includes an average value calculation circuit 91, a suppression characteristic memory circuit 92, and a counter circuit 93.
[0022]
The sonar device of FIG. 1 will be described. The transmission signal 2 output from the transmission circuit 1 is input to the transducer 3. After being converted into a sound wave by the transducer 3 and brought into water, the transmission signal 2 reflected by the target is received by the transducer 3. Then, the signal is converted into a received signal 4 which is an electric signal, and is amplified by the amplifier circuit 5. The amplified output signal 6 from the amplifier circuit 5 is output to a reverberation suppression (TVG) circuit 7.
[0023]
Next, the reverberation suppression circuit 7 limits the band of the amplified output signal 6 by the filter circuit 72 according to the transmission timing signal of the timing pulse generation circuit 78, and outputs the filter output signal to the detection circuit 74. The detection circuit 74 performs detection and outputs a detection output signal. This detection output signal is input to the average value calculation circuit 91, and calculates the average value of the reverberation level immediately after transmission. The average value output from the average value calculation circuit 91 is digitally converted by the A / D conversion circuit 73 and output as a signal after A / D conversion.
[0024]
The value of the A / D converted digital data signal after the A / D conversion is set as a start address in a suppression characteristic memory circuit (ROM, read only memory) 92. Then, it outputs suppression characteristic data corresponding to each timing of the timing signal generated by the counter circuit 93 activated by the transmission timing signal. The suppression characteristic data is input to the D / A conversion circuit 81 and output as an analog D / A converted output signal.
[0025]
The analog output signal after D / A conversion from the D / A conversion circuit 81 is input to the multiplication circuit 71. Then, the multiplying circuit 71 multiplies the amplified signal output 6 from the amplifying circuit 5 by the D / A-converted signal, and outputs the result to the phasing circuit 9 as a reverberation-suppressed multiplying circuit output 8.
[0026]
Next, the operation of the sonar device of the present invention shown in FIG. 1 will be described with reference to FIGS. FIG. 2 shows an example of the reverberation suppression characteristics of the suppression characteristics memory (92 in FIG. 1) used in the present invention. FIG. 3 shows an output conceptual diagram of the suppression characteristic. FIG. 4 shows the result of the reverberation suppression processing when the transmission level is changed in the present invention. FIG. 5 shows the result of the reverberation suppression processing when echoes from a target are mixed in the present invention.
[0027]
The reverberation suppression circuit 7 of the sonar apparatus shown in FIG. 1 obtains an average value by the average value calculation circuit 91 after band limitation of the input signal by the filter circuit 72 and detection by the detection circuit 74. Further, the data is converted into digital data by the A / D conversion circuit 73. The reverberation level immediately after transmission represented by the digital data is converted and set as a reverberation suppression characteristic start address stored in the suppression characteristic memory circuit 92.
[0028]
The reverberation suppression memory circuit 92 stores reverberation suppression characteristics from a high level to a low level (that is, a suppression amount from immediately after transmission to a certain time later) as shown in FIG. The reverberation characteristics to be stored are from the maximum reverberation level value expected when the maximum transmission level is transmitted to the reverberation level value when a sufficient time has elapsed after transmission.
[0029]
As shown in FIG. 3, a start address corresponding to the amount of suppression is set in the suppression characteristic memory circuit 92. By adding the timing pulse, the amount of reverberation suppression after the start point can be sequentially transmitted. Therefore, if the start position of the suppression level can be determined from the reverberation level in the received signal immediately after the transmission, the reverberation suppression processing can be performed with the suppression amount suitable for the reverberation situation. Therefore, as shown in FIG. 4, even when the transmission level is changed, it is possible to follow the change and perform the optimal reverberation suppression processing.
[0030]
When a signal from a target object exists during reverberation reception, an echo is included in the received signal. However, since the amount of suppression is determined by the reverberation suppression characteristics stored in the memory, even if the target echo exists, the reverberation suppression processing can be performed without any influence as shown in FIG. Become.
[0031]
That is, as apparent from FIG. 3, the start address of the suppression characteristic memory stored in the suppression characteristic memory circuit 92 is determined from the average value output calculated by the average value calculation circuit 91. Starting from this start address, the suppression level is determined. By determining the suppression level from the reverberation level immediately after transmission, it is possible to set the suppression amount in accordance with the reverberation occurrence situation. The output suppression level is multiplied by the amplification circuit output signal from the amplification circuit 5 in the multiplication circuit 71. Thereby, the output signal level can be controlled to reduce inconvenience such as saturation due to reverberation.
[0032]
The preferred embodiment of the sonar device according to the present invention has been described above in detail. However, the present invention should not be limited to only the specific embodiment example, and it can be easily understood by those skilled in the art that various modifications can be made according to specific applications.
[0033]
【The invention's effect】
As apparent from the above description, the sonar device of the present invention has various remarkable effects as follows. First, even if the transmission output is changed during reception, optimal reverberation suppression can always be performed. Further, even when a target signal exists during reverberation reception, processing can be performed without the target echo affecting the suppression processing. Furthermore, since the circuit scale is small, a small and inexpensive sonar device can be obtained.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a preferred embodiment of a sonar device according to the present invention.
2 is a reverberation suppression characteristic diagram of the suppression characteristic memory circuit in FIG. 1;
FIG. 3 is an output conceptual diagram of a suppression characteristic memory circuit.
FIG. 4 is a diagram illustrating a result of a reverberation suppression process when the transmission level is changed in the sonar device of FIG. 1;
5 is a diagram illustrating a result of a reverberation suppression process when a target echo is mixed in the sonar device of FIG. 1;
FIG. 6 is a block diagram showing a configuration of a conventional sonar device.
7 is a graph showing reverberation attenuation characteristics of the sonar device of FIG. 6 at a high transmission level and a low transmission level.
FIG. 8 is a diagram showing a delay in following the reverberation suppression level when the transmission level changes from high to low in FIG. 6;
FIG. 9 is a diagram illustrating a result of a reverberation suppression process when a tracking delay occurs in FIG. 6;
FIG. 10 is a diagram showing an echo from a target and a reverberation attenuation characteristic in FIG. 6;
FIG. 11 is a diagram illustrating a result of a reverberation suppression process when echoes from a target are mixed in FIG. 6;
[Explanation of symbols]
REFERENCE SIGNS LIST 1 transmission circuit 3 transmitter / receiver 5 amplifier circuit 7 dereverberation circuit 71 multiplier circuit 72 filter circuit 73 A / D conversion circuit 74 detection circuit 78 timing pulse generation circuit 81 D / A conversion circuit 91 average value calculation circuit 92 suppression characteristic memory circuit 93 counter circuit

Claims (4)

An average value calculation circuit that measures a received signal of a sound wave including reverberation after transmitting the sound wave to underwater, measures a reverberation level immediately after transmission, and outputs an average value per unit time,
An A / D conversion circuit that A / D converts the average value and outputs digital data;
A suppression characteristic memory circuit for determining a start address based on a reverberation level immediately after transmission equal to the digital data and reading out a previously stored suppression characteristic as a reverberation suppression signal;
A multiplication circuit for controlling an input signal by the reverberation suppression signal. The reverberation suppression characteristic with the time as an address for the amount of suppression from immediately after transmission to a certain time later is stored in a memory in advance, and the start position of the suppression level is determined from the reverberation level in the received signal immediately after transmission. A reverberation suppressing characteristic by reading a reverberation suppressing characteristic from the memory from an address corresponding to the reverberation. 3. The sonar according to claim 2, wherein the stored reverberation suppression characteristic ranges from a maximum reverberation level value expected when a maximum transmission level is transmitted to a reverberation level value at a time when a sufficient time has elapsed after transmission. 4. apparatus. The sonar apparatus according to claim 2, wherein the reverberation level in the received signal immediately after transmission for determining the start address of the suppression level is an average value of the reverberation level.

Images