JPS6363075B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sonar device, and particularly to a sonar device that emits a transmitted acoustic pulse and generates a video signal consisting of distance information, azimuth information, and amplitude information regarding a sonar target from a received signal obtained in response to the transmitted acoustic pulse, and a received signal. It outputs an audible audio signal obtained by converting it to an audible frequency, and uses this information to display sonar targets,
The present invention relates to an active sonar device for listening to sounds.

An active sonar device transmits a transmission acoustic pulse at a transmission repetition period corresponding to the transmission range, and inputs a reception signal using the rest period of the transmission repetition as a reception period, thereby obtaining information about the sonar target. well known.

In conventional sonar devices of this type, each time an echo of a sonar target is input, distance information, azimuth information, amplitude information, etc. of the sonar target are extracted from the echo, and these are transferred to a CRT (cathode).
Ray Tube) or a video display circuit such as a recorder, these are displayed as video signals.

Also, normally, sonar equipment converts the received signal from the sonar target into an audible frequency and uses the signal obtained as an audio signal for listening, and uses this audio signal for listening (hereinafter referred to as audio signal) to recognize the audible sound of the sonar target. We are trying to

However, regarding the output of sonar target information by the above-mentioned conventional sonar apparatus of this type, apart from the amplitude information used for the echo video signal, there are the following problems regarding the azimuth signal and the audio signal.

In other words, the azimuth signal from a conventional sonar device uses the azimuth information extracted from the echo every time it detects an echo from the sonar reception signal, and therefore it is not affected by the reverberation level or the relative relationship between the sonar device and the sonar target. It is easily affected by changes in target position or temporal changes in sound wave propagation conditions. The ratio S/R between the signal level S and the reverberation level R, especially in an operating environment where the reverberation level R is large.
This tendency is remarkable when the radial angle is small, and the variation in the azimuth information obtained for each transmitted acoustic pulse emission becomes large. In addition, since the frequencies of the signal level S and the reverberation level R are almost the same, it is difficult to separate them using a filter, etc. Therefore, the sonar target signal displayed on the image screen of a CRT etc. becomes an image that varies in the azimuth direction. The disadvantage is that the brightness of the image is relatively reduced due to the variation, and the signal is often missed.

In addition, the audio signals from conventional sonar devices use a received signal converted to a frequency of 800 to 1000 Hz, which is the easiest for humans to hear, using a heterodyne circuit. Sonar targets are identified by hearing based on the difference in tone due to the difference in sound.

What influences the timbre of this audio signal is the Doppler frequency of the sonar target present in the received signal. This Doppler frequency f _D is expressed by the following equation (1).

f _D =2v/c·f ₀ (1) In equation (1), v is the relative velocity between the sonar device and the target, c is the sound wave propagation speed, and f ₀ is the frequency of the transmitted acoustic pulse.

As is clear from equation (1), the Doppler frequency f _D decreases in proportion to the frequency f ₀ of the transmitted acoustic pulse and the relative speed between the sonar device and the target; for example, f ₀ =
When 2KHz and v=1kt (knot), f _D is approximately 1.38Hz
The disadvantage is that it becomes impossible to recognize the sonar target audibly due to the difference in tone due to the Doppler frequency difference.

An object of the present invention is to eliminate the above-mentioned drawbacks, to significantly improve the accuracy of azimuth information of a sonar target in a sonar device using an active transmission/reception method, and to significantly improve the auditory recognition function using audio signals in the low Doppler frequency region. Therefore, it is an object of the present invention to provide a sonar device that can greatly improve sonar detection accuracy.

The device of the present invention emits a transmitted acoustic pulse, and from a received signal obtained in response thereto, a video signal consisting of distance information, azimuth information, and amplitude information regarding a sonar target, and an audible sound obtained by converting the received signal into an audible frequency. In a sonar device that outputs an audio signal for use in audio signals, the azimuth information sample values obtained by sampling the azimuth information of the N reception signals specified in advance at a sampling frequency set in advance are each N pieces in the same sample order. an average azimuth calculation circuit that calculates the average value; and a level rectangle that presets the waveform of the received signal including the frequency component of the transmitted acoustic pulse and the Doppler frequency component by level clipping each time the received signal is input. out of the odd integer multiple components of the received signal frequency included in this rectangular wave, a prespecified odd integer multiple component is extracted and synthesized with a preset audible frequency to produce the audible audio signal. and an audio signal generation circuit that outputs.

Next, the present invention will be explained in detail with reference to the drawings.
FIG. 1 is a block diagram showing one embodiment of the present invention.

The embodiment shown in FIG. 1 includes a phase detection circuit 1, an average direction calculation circuit 2, switching circuits 3-1 and 3-2,
It is configured with an adder circuit 4, a received wave integration circuit 5, an audio frequency conversion circuit 6, an audio signal generation circuit 7, an audio signal amplification circuit 8, etc., of which the average direction calculation circuit 2 and the audio signal generation circuit 7 are the main circuit. This part is related to the invention, and the other constituent parts are typical constituent circuits according to the conventional method shown together with this part.

In the embodiment shown in Fig. 1, the sonar device receives by a spirit beam reception method, but the reception method by the sonar device may be any method other than the split beam reception method. It doesn't matter if it's something.

Now, in FIG. 1, the right receiving beam output 101-A and the left receiving beam output 101-B obtained through the right receiving beam and the left receiving beam constituting the split beam are respectively output from the phase detection circuit 1 and the adder circuit 4. is supplied to

This split beam reception method has recently become well known as one of the sonar reception methods, and the split beam reception method is one of the sonar reception methods. A set of receiving beams, that is, a plurality of split beams, which have equal reception directional characteristics on the left and right sides in the azimuth, are formed in advance, and reception is performed through a group of these plural split beams. The phase difference of the sonar target due to these two receiving beams is obtained by cross-correlation calculation of the received signals received by the common range of the two right and left receiving beams forming a split beam directed toward the It is also well known that the azimuth of a sonar target can be obtained via phase difference.

The phase detection circuit 1 is a circuit that obtains azimuth information of a sonar target from a received signal obtained by such a split beam reception method, and includes a split beam output multiplication circuit, a correlation integration circuit, an arithmetic operation circuit, and a trigonometric function. It is equipped with an arithmetic circuit, etc., multiplies the input right reception beam 101-A and left reception beam 101-B, and then sends this to a correlation integration circuit to perform correlation integration and obtain a cross-correlation output of the two inputs,
Direction information is obtained as follows using four arithmetic operations and trigonometric function operation circuits.

That is, if the phases of the right receiving beam output 101-A and the left receiving beam output 101-B are respectively φ _R and φ _L , the phase φ _RL of the correlation output obtained by cross-correlating these two receiving beam outputs and the above As is well known, the following equation (2) holds between φ _R and φ _L.

φ _RL =φ _R −φ _L ...(2) However, equation (1) corresponds to the case where φ _R >φ _L. It is also well known that θ is expressed by the following equation (3), where θ is the azimuth angle of the sonar target toward which the split beam is directed.

θ=sin ^-1 {λ(φ _R −φ _L )/2πd} ...(3) In equation (3), λ is the wavelength of the transmitted acoustic pulse, and d is the center of the right and left receiving beams that make up the split beam. It is the position interval.

The phase detection circuit 1 performs calculations according to equations (2) and (3), obtains an output signal with a voltage level corresponding to the azimuth angle θ, and outputs this as the azimuth signal 102. In conventional sonar devices, this is directly sent to a display circuit (not shown) and used as azimuth information, but the time constant of the correlation integration circuit described above depends on the level of its output signal, that is, the azimuth signal 102. is made sufficiently small to accommodate changes in the azimuth angle θ, and is therefore susceptible to fluctuations due to normal reverberation or noise, and this tendency increases as the S/R ratio decreases.

Right receive beam output 10 sent to adder circuit 4
1-A and left reception beam output 101-B are thereby subjected to addition processing, and these two inputs are superimposed to output addition output data 401 as amplitude information of the reception signal, which is sent to the detection and integration circuit 5 and the audio signal. The signal is supplied to a frequency conversion circuit 6 and an audio signal generation circuit 7, respectively.

The detection and integration circuit 5 includes an envelope detection circuit, an integration circuit, etc., and performs envelope detection every time the addition output data 401 is input, and then inputs it to an integration circuit having a time constant approximately equal to the pulse width of the transmitted acoustic pulse. After being integrated, it is sent to a display circuit or the like via an output line 5001 as a video signal as display information including amplitude information and distance information.

The audio frequency conversion circuit 6 processes the input addition output data 401 as follows, and obtains an audio signal 601 from this input.

That is, the audio frequency conversion circuit 6 is equipped with a frequency mixer circuit, etc., and when inputted with addition output data 401, outputs an audio signal 601 of an audible frequency using a heterodyne frequency conversion method that mixes this with a local oscillation signal of a preset frequency. . When the input addition output data 401 includes an echo, an echo component having a fundamental frequency f ₀ of the transmitted acoustic pulse with a Doppler frequency f _D and a reverberation component having a frequency component f _R approximately equal to this fundamental frequency f ₀ are the main frequency components, and other frequency components include noise having a temporally random distribution. Therefore, when the preset audible frequency is f _A , (f ₀ - f _A ) is input to the frequency mixer circuit as the frequency of the local oscillation signal, and this and the above-mentioned addition output data 401 are frequency-mixed and output. (f _A + f _D ) is obtained as a frequency component.
In the case of this embodiment, f _A is set to 800 Hz, so that the audio signal 601 is output as 800 Hz shifted by the Doppler frequency f _D , and this audio signal 601 is transmitted to the listening circuit (not shown). ) and the video signal 5001 output from the detection and integration circuit 5.
It is also used for sonar target recognition.

Note that the Doppler frequency f _D gives a frequency deviation with respect to f _A so that it is numerically added to the audible frequency f _A as either plus or minus depending on the state of relative motion between the sonar target and the sonar device. . In the case of so-called remote Doppler, which occurs when the distance between the sonar target and the sonar device increases, the Doppler frequency f _D is added as a minus to the audible frequency f _A , and this occurs when the distance decreases. In the case of so-called proximity Doppler, the Doppler frequency f _D is added as a plus to the audible frequency f _A.

Although the above is a common means of generating azimuth signals, video signals and audio signal outputs by conventional sonar devices, the azimuth signals and audio signals obtained in such conventional methods each have drawbacks as described above. .

Therefore, in this embodiment, in addition to these conventional circuits, an average direction calculation circuit 2 and an audio signal generation circuit 7 are provided.
The above-mentioned drawbacks are eliminated as follows.

The average azimuth calculation circuit 2 includes a memory circuit 21 and an average value calculation circuit 22, and the memory circuit 21 receives the azimuth signal 1 input from the phase detection circuit 1.
Under the control of the system control program received via the system bus line 1001, N units of 02 are sequentially stored in the memory via the built-in A/D converter. The built-in A/D converter samples the azimuth signal 102 at a sampling frequency with a preset period, so that all N azimuth signals 102 are stored in the memory as digital quantities with the same number of samples. Further, the N direction signals 102 are N received signals obtained in response to the transmitted acoustic pulses, in this embodiment, the right receive beam signal 101-A and the left receive beam signal 101 of the aforementioned split beam, respectively. -B
This is obtained in response to

FIG. 2 is a bearing signal characteristic diagram A showing the content of the bearing signal in the embodiment of FIG. 1, and its average bearing signal characteristic diagram B.

The operation of the direction calculation circuit 2 in the embodiment shown in FIG. 1 will be explained below with reference to FIG.

N direction signals 10 input to the memory circuit 21
₂ is input as azimuth signals S ₁ , S ₂ , .
These azimuth signals have a range of distances when the central azimuth of the transmitted beam of the transmitted acoustic pulse is 0 and the azimuth angles to the right and left of this central azimuth are expressed as voltage levels + and - corresponding to these azimuths, respectively. Over the corresponding reception time, a reverberant azimuth signal a and an echo azimuth signal E containing noise are obtained as + or - voltage levels corresponding to the magnitude of the azimuth shifted clockwise or counterclockwise from the center of the transmitted beam, respectively. , the echo azimuth signal E is extracted from the received signal along with the video signal over a period of time determined by the transmitted acoustic pulse width, the posture of the sonar target, etc., but these azimuth signals are usually The level is obtained while changing with time t.

These azimuth signals S ₁ , S ₂ , . _. .
It is digitized as a sample every t ₀ and stored in memory. For example, 1 of echo direction information E
part is stored as an orientation information sample corresponding to sampling period t ₀ as shown in FIG. 2A.

Under normal operating conditions of the sonar device, such echo azimuth information E included in the azimuth signal 102 output from the phase detection circuit 1 is transmitted at approximately the same time or with a significant time difference once an echo is captured. The general situation is that the sonar target and the sonar device become more likely to be detected continuously, and the relative positional relationship between the sonar target and the sonar device gradually approaches a constant state, making it easier to shift to the low Doppler region. It is.

On the other hand, the echo azimuth information except for the echo azimuth information E shown in FIG. 2A is mainly reverberant azimuth information a containing noise, and all of these are generated randomly both temporally and quantitatively.

Now, the _second
In Figure A, each sample value of the azimuth signals S ₁ , S ₂ ...S _N is added in correspondence with the sampling order, and this is divided by N to obtain the respective average value.
When the calculation shown in equation (4) is executed, the results are essentially different for the reverberant component and the echo component, and the average value of the azimuth signal of the reverberation component, which has randomness, is almost 0, and the azimuth signal of the echo component is By averaging, the fluctuation becomes extremely small.

Φ(t ₀ )=1/N N _N 〓 ⁿ⁼¹ φ _o (t ₀ ) ...(4) In equation (4), φ _o (t ₀ ) is the nth sample of the direction signal, and Φ(t ₀ ) indicates the average value of N samples of the azimuth signals S ₁ , S ₂ . . . _SN .

The memory circuit 21 is connected to the system bus line 100
Under the control of the system control program received via 1, the azimuth signal of FIG.
Each sample value of S ₁ , _{S 2} , .

The average value calculation circuit 22 outputs the input sample values of the azimuth information data to the system bus line 10.
Under the control of the system program received through the 01, the calculation shown in equation (4) is executed for each of the same sampling order of the azimuth signals S ₁ , _{S 2} . Send to 3-1.

FIG. 2B is a characteristic diagram of the average azimuth signal obtained in this manner. As a result of the average value calculation, the average reverberant azimuth signal a′ including noise has temporal randomness, so the azimuth information becomes almost zero level, and the echo average azimuth signal E′ due to the echo is based on the transmitted acoustic pulse width and the sonar target. Time to respond to posture etc.
Provided as direction information at a nearly constant level.

The switching circuit 3-1 includes an analog gate circuit, a relay circuit, etc., and receives an operation mode signal 1 via an operation control console (not shown) of the sonar device.
Either the average direction signal 201 or the direction signal 102 inputted by 002 is switched and output to the CRT of the display circuit via the output line 3001.
The azimuth of the video signal 5001 input to the horizontal and vertical deflection circuits and displayed on the CRT via these horizontal and vertical deflection circuits matches the azimuth angle corresponding to + or - indicated by the average azimuth signal 201. The horizontal and vertical deflection amounts are corrected so that In this way, by displaying the video signal 5001 in accordance with the average azimuth signal having a substantially constant value, the displayed azimuth of the video signal, which is normally dispersed in response to variations in the azimuth signal, can be made to be approximately close to the true value. Aggregate video signal display level,
Therefore, display brightness can be increased and display with high accuracy can be achieved.

Note that the time T ₀ shown in Fig. 2 is determined to correspond to the distance range of the sonar device, and therefore the phase information shown in Fig. 2 and the distance information corresponding to the respective distance ranges are also determined. It is clear that there are.

FIG. 3 is an azimuth signal display diagram showing an example of the display of the azimuth signal shown in FIG.

Figure 3A is a conventional direction signal display diagram, which corresponds to the direction signal S1 in Figure 2A, and Figure 3B is a diagram showing the direction signal _S1 in Figure 2A.
FIG. 3 is an average azimuth signal display diagram of FIG. B;

On part P of a circular image display screen such as a CRT, there is an image corresponding to the direction signal shown in S1 of FIG. _2A in FIG. In Fig. 3B, an image corresponding to the azimuth signal shown in Fig. 2B is displayed.
In the case of Figure A, a reverberant azimuth signal a containing noise appears at a relatively high level in the azimuth signal, and fluctuations due to these reverberations, noise, etc. appear temporally randomly in the echo azimuth information E, and this tendency is similar to S/ This becomes more noticeable as the R and S/N ratios become smaller.

The display of other azimuth signals shown in FIG. 2A basically has the same tendency as that shown in FIG. 3A.

On the other hand, in the average azimuth signal display of this embodiment shown in FIG. 3B, which corresponds to FIG. As the echo average azimuth information E' reaches the almost zero level, fluctuations are greatly suppressed and the echo average direction information E' is displayed as having a nearly constant value.

Now, the addition output data 401 output from the addition circuit 4 is also sent to the audio signal generation circuit 7.

The audio signal generation circuit 7 includes a clipper circuit 71,
It is configured to include a BPF (Band Pass Filter) 72, an audio frequency conversion circuit 73, and the like.

Each time the clipper circuit 71 receives the summation output data 401, it level clips the summation output data 401 by limiting amplification, and converts the waveform included in this summation output into a rectangular wave having a preset level.

As mentioned above, the addition output 401 has a reverberation frequency f _R approximately equal to the transmitted acoustic pulse fundamental frequency f ₀ , and when an echo is input thereto, the fundamental frequency f ₀ exists including the Doppler frequency f _D , and therefore the frequency component is It can be regarded as approximately (f ₀ +f _D ).

When an echo exists, _the clipper output 711 output from the clipper circuit ₇₁ is converted into a frequency component by using the above-mentioned rectangular wave conversion. f ₀ + f _D ), 5 (f ₀ + f _D ), ... (2n + 1)
(f ₀ +f _D ) is output.

The BPF 72 is an arbitrary integer odd multiple frequency component specified in advance among these (f ₀ + f _D ) integer odd multiple frequency components, in this example, 5 (f ₀ + f _D )
with the center frequency and the bandwidth Bwo of the fundamental frequency f ₀
This is a bandpass filter configured with a passband of 5 times 5Bwo, and therefore, the BPF output 721 has frequency components of 5 (f ₀ +f _D ).

This BPF output 721 is then sent to the audio frequency conversion circuit 73, and the local oscillation frequency (5f ₀ −f _A ) is
The signals are frequency-mixed by a frequency mixing circuit, and an audio signal 731 of (f _A +5f _D ) is output as an output frequency component by so-called heterodyne frequency conversion. The above f _A is the same frequency as f _A in the local oscillation frequency (f ₀ +f _A ) of the audio frequency conversion circuit 6, and in this embodiment, 800 Hz is used as the audible frequency as described above.

Therefore, in the audio signal 731, 5f _{D, which is five times the Doppler frequency f D ,} is added and superimposed on f _A of 800 Hz as a positive or negative amount corresponding to distant Doppler or close Doppler, for example, as described above. As in the example, the fundamental frequency f ₀ of the transmitted acoustic pulse is
2KHz, and when the relative speed between the sonar device and the sonar target is 1 knot, 5f _D is approximately 6.9Hz.
It is superimposed on f _A of 800 Hz, and the difference in tone due to the superposition of this expanded Doppler frequency is sufficiently distinguishable and audible to normal sonar operators, and it is also By doing so, the auditory recognition function will be greatly expanded, especially in operating environments with low S/R and S/N ratios and in low Doppler frequency conditions. In addition, considering that human hearing characteristics have a higher ability to separate and recognize sound sources by using frequency differences, that is, differences in timbre, than by separating and recognizing sound sources based on level differences at the same frequency, it is important to use such expanded Doppler frequencies. It can be said to be extremely effective.

The audio signal 731 is input to the switching circuit 3-2 together with the audio signal 601 output from the audio frequency conversion circuit 6.

Switching circuit 3-2 has substantially the same contents as switching circuit 3-1, and outputs either of these two inputs via output line 321 under the control of an operating mode control signal received via control line 1002. The signal is sent to the audio signal amplification circuit 8.

The audio signal amplification circuit 8 amplifies the input thus supplied to a predetermined level and outputs it as an audio signal to a listening circuit (not shown) via an output line 8001.

In this way, it is possible to output a more accurate azimuth signal than conventional sonar devices, as well as output an audio signal by superimposing the expanded Doppler frequency. Low S/R,
Significant improvements in signal-to-noise ratio and these capabilities for operation in low Doppler frequency conditions could be achieved. In particular, the operation of a sonar device in a low Doppler frequency state is an operational state that often occurs during the so-called sonar target holding period, in which a sonar target is captured by the sonar device and detection by the sonar device continues after that. Therefore, especially during this period, the improvement in the accuracy of direction recognition and the expansion of the hearing recognition range will greatly improve the detection performance of sonar.

The present invention provides an azimuth information output circuit in a sonar device that samples azimuth information corresponding to each of N reception signals specified in advance at a sampling frequency set in advance, and in the sampling order of sample values obtained thereby. A means for taking the average value of and outputting it as average azimuth information is also used, and an audio signal output circuit is also used for expanding the Doppler frequency by an integer-odd number and using it as an audio signal for listening. The basic feature is that the direction signal and the audio signal are obtained from the signal, and various modifications of the embodiment of the present invention shown in FIG. 1 are possible.

For example, in this embodiment, the Doppler frequency expanded by the audio signal generation circuit 7 shown in FIG. 1 is five times the fundamental Doppler frequency included in the received echo, but this It is clear that it can be implemented in exactly the same way even if it is doubled.

Furthermore, the average azimuth calculation circuit 2 and the audio signal generation circuit 7 shown in FIG. It is also clear that using only one of them can be easily implemented by changing the system program.

Furthermore, in the embodiment shown in FIG. 1, it is assumed that the received signal is acquired by a split reception method, but it is clear that this can be implemented in almost the same way even if the received signal is acquired by any other reception method. All of the above can be easily implemented without detracting from the spirit of the present invention.

As explained above, according to the present invention, in a sonar device, the azimuth information corresponding to each of N prespecified received signals is sampled at a preset sampling frequency, and the average value is calculated for each sampling order. In addition, the Doppler frequency of the echo contained in the received signal is expanded to an integer-odd multiple and superimposed on a preset audible frequency, which is used as an audio signal. By processing the received signal in parallel with the conventional azimuth and audio signal output circuit, the azimuth calculation accuracy and the auditory recognition range are greatly improved and expanded, and especially low S/R, S/N ratio and low The present invention has the advantage that a sonar device can be realized which can significantly improve these functions in the Doppler frequency operating state, and therefore can significantly improve the detection ability.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention;
Figure 2A is a bearing signal sampling characteristic diagram in the embodiment of Figure 1, Figure 2B is an average bearing signal characteristic diagram of Figure 2A, and Figures 3A and B are bearing signals in Figure 2A and B. FIG. 3 is an azimuth signal display diagram showing an example of a display. DESCRIPTION OF SYMBOLS 1... Phase detection circuit, 2... Average direction calculation circuit, 3-1, 3-2... Switching circuit, 4... Addition circuit, 5... Detection integration circuit, 6, 73... Audio frequency conversion circuit, 7...Audio signal generation circuit, 8...Audio signal amplification circuit, 21...Memory circuit, 22...
Average value calculation circuit, 71... Clipper circuit, 72...
…BPF.

Claims (1)

[Claims] 1. A video signal consisting of distance information, azimuth information, and amplitude information regarding the sonar target from a received signal obtained by emitting a transmitted acoustic pulse, and an audible audio signal obtained by converting the received signal to an audible frequency. In the output sonar device, calculate the average value of the azimuth information sample values obtained by sampling the azimuth information of the N received signals specified in advance at a sampling frequency set in advance, respectively, for each N sample value in the same sample order. and an average azimuth calculation circuit that converts the waveform of the received signal including the frequency component of the transmitted acoustic pulse and the Doppler frequency component into a rectangular wave of a preset level by level clipping each time the received signal is input. Audio signal generation for extracting a prespecified odd integer multiple component from among the odd integer multiple components of the received signal frequency included in the rectangular wave, and synthesizing this with a preset audible frequency to output the audible audio signal. A sonar device comprising a circuit.