JPH07253469A - Instrument for measuring frequency characteristic of fish - Google Patents

Abstract

PURPOSE:To obtain an instrument which can measure the relation between the frequency-and reflecting strength characteristic of a single fish or a school of fish. CONSTITUTION:An instrument for measuring frequency characteristic of fish is provided with transmitters-receivers 1-1 to 1-N having the same directional pattern and different transmission-reception frequencies and arranged on a straight line perpendicular to the direction of their directional axes by orienting the directional axes in the same direction transmitters-receivers 2-1 to 2-N corresponding to the transmitters-receivers 1-1 to 1-N and measures the relation between the frequency and reflecting strength characteristic of fishes in such a way that the instrument transmits pulse-like exciting signals of the same level to the transmitters-receivers at the frequencies fixed to each transmitter-receiver based on a timing signal from a timing circuit 4 at such timing that reflected sounds from the fishes do not overlap upon another in time and receives signals generated when reflected waves from the fishes are received. Then the instrument sends the receiving level of the received signals to a display 3 and the display 3 displays the receiving level in corresponding to the frequencies.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring the frequency-reflection intensity characteristic of a single fish or a school of fish in water.

[0002]

2. Description of the Related Art Conventionally, frequency selection in a fish finder or a fish finder sonar has been performed such that a low frequency is used to detect a distant fish school and a high frequency is used to detect a fish school in a short distance. There is.

This is suitable for detecting a school of fish over a wide azimuth range at a long distance because the directional characteristics can be widened at a low frequency and the attenuation in water is small, while the attenuation in water is increased at a high frequency. Although it is large, it has a sharp directivity and is suitable for accurately detecting a school of fish in a short distance.

However, how the reflection intensity of a single fish or a school of fish itself changes from a low frequency to a high frequency, and further, the change of the reflection intensity when the frequency is changed depending on the fish species. There is no conventional device that measures how different aspects (patterns of change) are.

[0005]

On the other hand, it is very important to determine what kind of fish or school of fish has been detected in a fishing operation in order to determine the fish net to be used and the method of casting net. Therefore, the fish type is determined based on the fish speed, the movement pattern, the shape and shade characteristics of the fish school image, the depth, the sea area, the season, and other information from the image of the fish finder or sonar. Therefore, there is a case where it is unavoidable to rely on experience and intuition, and there is a possibility that the judgment may be wrong.

In view of such a situation, an object of the present invention is to give a strong clue to fish species determination by focusing on the difference in frequency vs. reflection intensity characteristics of each fish species and by grasping the frequency characteristics thereof. It is an object of the present invention to provide a frequency response device for fish that makes determination more reliable.

[0007]

The present invention has the following means for achieving the above object. That is, in the fish frequency characteristic measuring device of the present invention, firstly, a plurality of transducers having different specified transmission and reception frequencies but having the same directional characteristics at the frequencies have the same directional axis direction. A group of transducers arranged on one straight line that is perpendicular to the direction of the directional axis; and an excitation signal of the same level at the frequency determined for each transducer, which is provided corresponding to each transducer. A plurality of transmitters / receivers for transmitting the received signals from the corresponding transmitters / receivers; a timing circuit for sequentially performing transmission so that received signals from the respective transmitters / receivers do not overlap in time; An apparatus for displaying a frequency characteristic of fish, comprising: an indicator for displaying a received output level from the vessel corresponding to a transmission / reception frequency.

Secondly, by receiving the received signals from the two wave-receiving elements having a specific interval in the arrangement direction of the wave-receivers for each wave-receiver, and detecting the phase difference between the two signals. , The displacement angle from the directional axis of the reflection target is detected for each transducer, and the reception output level of each transceiver is corrected to the output level in the directional axis direction from the displacement angle and the directional characteristics of each transducer. The above-mentioned first fish frequency characteristic measuring device having a level correction circuit for sending to a display device.

[0009]

The operation of the above means will be described below. In the device of the present invention, a plurality of wave transmitters / receivers having the same directional characteristics and different wave transmission / reception frequencies are arranged on a straight line which has the same directional axis direction and is perpendicular to the directional axis direction. The transmitter / receiver transmits and receives the excitation signal of the same level of the frequency defined by each transmitter / receiver, and receives the reflected wave from a single fish or a group of fish (hereinafter simply referred to as a fish) which is a reflection target. To wave. The waves are sequentially transmitted by the timing circuit so that the received signals do not overlap in time, so that the received signals having different frequencies are not mixed and received.

If the distance to the fish is sufficiently larger than the distance between the transducers, it can be considered that the directions of the fish seen from the transducers are the same. Therefore, the difference in the level of the received signal in each wave receiver, that is, the difference in the reception output level of the transceiver is due to the difference in frequency. Since the display unit displays the received output level corresponding to each frequency, it is possible to know the frequency versus reflection intensity characteristic of fish (simply referred to as frequency characteristic).

Next, if the distance to the fish is so short that the difference in direction when the fish is seen from each of the transducers cannot be ignored, the level difference due to the difference in direction is corrected. Therefore, by the level correction circuit, for each transducer, from the phase difference of the received signals from the two receiving elements having a specific interval in the arrangement direction of the transducer, the direction of the fish from the direction of the directional axis. Since it is possible to know how much the displacement is, and from that and the known directional characteristics of the transducer, the received output level can be corrected to the output level in the direction of the directivity axis and sent to the display unit. It is possible to know the difference in the received output level due to the difference in frequency, that is, the frequency characteristic.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the configuration of an embodiment of the present invention. In 1-1 to 1-N, the directional characteristics are the same when transmitting and receiving at the predetermined transmission and reception frequencies of f ₁ , f ₂ , ... f _N , respectively (N (≧ 2)) It is a transceiver.

Reference numerals 2-1 to 2-N denote transceivers connected to the respective transducers, and send pulse-shaped excitation signals of the frequencies determined by the corresponding transducers to the transducers at the same level. Also, the reception signal of the sound wave received by the receiver is received and a signal in which the reception level information is maintained is output. The excitation output of each transceiver is sequentially output by the timing signal from the timing circuit 4 at appropriate time intervals so that the reflected signals from the fish do not overlap in time.

The received signal resulting from the reflection from the fish thus obtained is sent to the display 3. The display device 3 displays the levels of the received signals input in the order of the excitation timings in association with the frequencies of f ₁ , f ₂ , ... F _N which are known in advance.

As a concrete display format, a horizontal axis is a frequency and a vertical axis is an amplitude level on a CRT display, and a level value corresponding to the frequency is plotted, and a broken line or a graph on a curve is drawn. Although typical, the present invention is not limited to this, and may be of any type as long as the change in the reception level with respect to the change in frequency is easily visible.

FIG. 2 shows a configuration in which a level correction circuit is added to the configuration of FIG. This is because when the distance between the transducer group and the fish is short and the difference in the direction in which the fish faces due to the distance between the transducers cannot be ignored, the level actually received by each transducer and the orientation of the transducer From the characteristics, it is a circuit that corrects the reflection from the same fish to a level that should be obtained when received from the directional axis direction. By doing so, it is intended to eliminate the difference in the receiving level due to the difference in the receiving direction.

Now, as shown in FIG. 3, it is assumed that the reflected wave from the direction of the displacement angle θ from the directional axis direction arrives at the two wave receiving elements with the wave receiving surface oriented in the directional axis direction and having a distance d. Then, the sound wave reaching the wave receiving element 6 lags behind the sound wave reaching the wave receiving element 7 by the distance d ′, so that the phase of the wave receiving signal of the wave receiving element 6 is the same as that of the wave receiving signal of the wave receiving element 7. It lags behind the phase by that amount. The phase difference φ is expressed by Equation 1.

[0018]

[Equation 1]

Therefore, if the phase difference φ can be known, the displacement angle θ can be obtained by the equation 2 which is a modification of the equation 1.

[0020]

[Equation 2]

On the other hand, since the ratio of the received wave level in the direction of the directivity axis to the received wave level at each displacement angle is obtained from the directivity characteristic, if the displacement angle and the received wave level in that direction are known, the directivity is determined from the directivity characteristic. It is possible to obtain the received wave level in the axial direction. FIG. 4 is a diagram showing the configuration of the level correction circuit 5 which performs the above correction.

The received signals received by the two receiving elements are subjected to amplification and other processing and then applied to the phase difference detector 8, where the phase difference φ is detected. The signal of the detected phase difference φ is applied to the displacement angle calculator 9. The displacement angle calculator 9 calculates the displacement angle θ by performing the calculation of Expression 2. The calculated displacement angle θ is added to the correction calculator 10. The directional characteristics of the transmitter / receiver are input to the correction calculator 10, and the received output level from the transmitter / receiver is corrected by the directional characteristics and the displacement angle θ. The corrected reception level that has been corrected as received is sent to the display. The operation of the display device 3 is the same as in the case of FIG.

[0023]

As described above, in the device of the present invention, a plurality of transducers having the same directional characteristics and different transmitting and receiving frequencies are arranged on one straight line perpendicular to the direction of the directional axis, and the received signal is received. Receive the reflected waves from the same fish so that they do not overlap in time, and display the received output level, and the corrected received output level when the displacement angle cannot be ignored, in correspondence with the transmitted and received frequencies. Since this is done, the frequency versus reflection intensity characteristic of the fish can be measured, which has the advantage of making the determination of the fish species even more reliable than in the past.

[Brief description of drawings]

FIG. 1 is a diagram showing a basic configuration of an embodiment of a device of the present invention.

FIG. 2 is a configuration diagram in which a level correction circuit is added to the basic configuration of the embodiment of the device of the present invention.

FIG. 3 is a diagram illustrating that a phase difference occurs between received signals of two receiving elements when the arrival direction of a sound wave is displaced from the directional axis direction.

FIG. 4 is a diagram showing a specific configuration example of a level correction circuit.

[Explanation of symbols]

 1-1 to 1-N Transducer 2-1 to 2-N Transceiver 3 Display 4 Timing circuit 5 Level correction circuit 6 Wave receiving element 7 Wave receiving element 8 Phase difference detector 9 Displacement angle calculator 10 Correction calculation vessel

Claims (2)

[Claims] 1. A plurality of transmitters / receivers having different specified transmission / reception frequencies but having the same directivity characteristics at the frequencies are arranged on one straight line which has the same directivity axis direction and is perpendicular to the directivity axis direction. An array of transducers arranged; each of the transducers is provided with an excitation signal of the same level at the frequency determined for each transducer, and is transmitted from the corresponding transducer. A plurality of transceivers that receive the received signals; a timing circuit that sequentially performs transmission so that the received signals from the respective transceivers do not overlap in time; and the reception output level from each transceiver as the transmission and reception frequency An apparatus for displaying frequency characteristics of fish, comprising: 2. Each of the wave transmitters / receivers receives wave received signals from two wave receiving elements having a specific interval in the arrangement direction of the wave transmitters / receivers, and detects the phase difference between the two signals to thereby obtain the respective signals. The displacement angle from the directional axis of the reflection target for each transducer is detected, and the received output level of each transceiver is corrected to the output level in the directional axis direction from the displacement angle and the directional characteristics of each transducer. The fish frequency characteristic measuring device according to claim 1, further comprising a level correction circuit for sending to a display.