JPS58118975A - Fish shoal quantity measuring method - Google Patents

Abstract

PURPOSE:To eliminate instantaneously an interference component between each fish body, and to measure exactly a fish shoal quantity at every receiving, by adding and averaging instantaneous power of receiving acoustic pressure of each carrier frequency by use of an ultrasonic pulse which makes plural frequencies to be a carrier wave. CONSTITUTION:Plural ultrasonic pulses which make different frequencies to be a carrier wave are transmitted through transmitting and receiving devices 3-3'' tuned to each frequency, and are received by the transmitting an receiving devices 3-3'' at each frequency. Subsequently, they are propagated, attenuated and corrected by Sensitive Time Constant circuits 7-7'', and after that, a detecting output of each carrier frequency is averaged and added by an adding circuit 9, and instantaneous power of receiving acoustic pressure is detected by a square-law circuit 10. By instantaneous power being close to a fundamental component by which an interference component between each fish body has been eliminated instantaneously, the fish shoal quantity can be measured exactly at every receiving.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of measuring the amount of a school of fish, and more particularly to an integral method of measuring the amount of a school of fish using a plurality of ultrasonic pulses.

The conventional fish school mass measurement method using an integral method using ultrasonic waves is a method in which the average number density of a school of fish is obtained from the power of the received sound pressure of the reflected echo from a school of fish in the water. The tail number density is automatically obtained by correcting the attenuation due to the propagation of the received sound pressure power and then processing it in consideration of the electroacoustic coefficient and single reflectance. That is, if the average number density of tails is n.

is given by Here, it is the output voltage of the preamplifier, the received sound pressure Pj, and the receiving sensitivity M of the receiver.

It is expressed by the following equation using the receiver gain Gr.

E,=P, -MG, ・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・・・・・・・
(2) When there are many fish within the pulse width, the average fish number density n changes irregularly from moment to moment due to the interference component caused by the interference of sound waves between fish bodies. As a result, the average number of fish density also fluctuates.

The instantaneous value prn of the received sound pressure of the reflected echo from a school of fish is a value obtained by combining the sound pressure of the reflected echo from a single fish within the pulse width for the total number N of fish within the pulse width, and is given by a quadratic equation.

p = ΣPri sin (ωt+ψl)...
・・・・・・・・・・・・Mountain・“・・・・・・・°(3
1r i+1 oxta. The instantaneous value Pr2 of the power of the received sound pressure based on the total number of waves existing within the pulse width is given by the following equation.

Here, Pri and Prj are the reflection intensities of fish i and fish j, respectively, and ψ1. ψj is the initial phase of fish 1 and fish j in carrier wave ω.

1-, (The first term of equation 41 is 2 of the reflection from each fish body.
The second term corresponds to the basic component of the instantaneous value of the power of the received sound pressure, and the second term is an interference component caused by interference between fish bodies, and is a component that changes irregularly.

In such conventional methods, since a single frequency is used as a carrier wave, it is impossible to remove interference components instantaneously. By aligning and averaging the interference components, the fundamental component was obtained. However, this method has the disadvantage that it takes time to obtain the basic component of the received sound pressure power. There is a possibility that the basic components themselves may be averaged, making it difficult to accurately detect the amount of fish.

The present invention solves two or more problems.

Ultrasonic pulses with multiple frequencies as carrier waves are transmitted simultaneously or in a time-division manner, and the received sound pressure power for each carrier frequency is added and averaged to align the time axes and perform a set average operation on the received sound pressure power. The purpose of this is to instantly remove interference components caused by sound wave interference between fish bodies and accurately determine the amount of fish at each reception.

An embodiment of the present invention shown in the drawings will be explained in detail below.

In a block circuit diagram showing an embodiment of the present invention.

1 is a transmission pulse generation circuit, 2 to 2" are power amplification circuits for transmission, 3 to 3" are transducers, 4 to 4" are amplification circuits for filtering, and 5 to 5" are for each frequency. 6 to 6" are preamplifier circuits, and 7 to 7" are STC circuits for correcting propagation attenuation.

8 to 8" are linear detection circuits, 9 is an addition circuit that adds the received voltage for each frequency, 10U square circuit, 11 is an integration circuit,
12 is an A/D conversion circuit, 13 is an arithmetic unit, and 14 is a display unit.

Next, to explain the operation of this block circuit, it is assumed that transmission pulses with multiple frequencies as carrier waves are simultaneously transmitted from separate transmitters, and reception is performed using separate receivers for each frequency. However, the present invention is not limited to this, and it is also possible to perform the transmission/reception in a time-division manner, and the combined liquid of each frequency is
It's okay to have IJ.

First, create a transmission pulse generator circuit 1, and then create a power amplification circuit 2.
A plurality of ultrasonic pulses having different frequencies as carrier waves are transmitted through transducers 3 to 3'' tuned to each frequency after being amplified in power by 2''. 3" is received for each frequency. The received sound pressure for each frequency is amplified to an appropriate level for filtering by 4 to 4", and filtered by a 5 to 5" filter circuit. , and is amplified to a predetermined level by preamplifier circuits 6 to 6'' to obtain Er in equation (2).

Next, 7 to 7" S T C (Sensitive Ti
After the propagation attenuation is corrected in the 8-8'' linear detection circuit, the detection output for each carrier frequency is added and averaged in the 9-addition circuit.The added and averaged DC component is squared by a 10 squared circuit.

Instantaneous power of received sound pressure can be obtained. This instantaneous power has interference components removed and has a value close to the fundamental component. This means that cos (ψl - ψj) in the interference component of equation (4) is determined by the phase difference in the carrier waves of white fish 1 and j fish in the pulse, and the more frequencies used, the more cos
This is because the average value of (ψi→j) approaches zero, and the interference component can be ignored.

As a result, the fundamental component of the received sound pressure power can be obtained instantaneously, without aligning the time axes from transmission and performing collective averaging as in the conventional method. The output of the squaring circuit is time-averaged around the distance Xe of interest by the 11 integrating circuit, and then
2, the signal is converted into a digital signal and sent to the arithmetic unit 13. In the calculation section 13.

The average run density n is calculated by performing the calculation on the right side of equation (1). In addition, the output of the integrating circuit 11 is
4, and the instantaneous power (σ) fundamental component of the received sound pressure is displayed in analog form. On the display unit 14, r[ and the calculation result of the calculation unit 13 are also displayed at the same time.

As explained above, according to the present invention, ultrasonic pulses having a plurality of frequencies as carrier waves are used.

Add and average the instantaneous power of the received sound pressure for each carrier frequency.
By instantly removing interference components using Js, the effect of obtaining an accurate amount of fish each time is obtained is 1().

[Brief explanation of the drawing]

FIG. 1 is a bronch circuit diagram for explaining an embodiment of the method for measuring the amount of fish according to the present invention. l...Transmission pulse generation circuit, 2~2''...power amplification circuit, 3~3''...transducer/receiver, 4~4''...amplifier circuit. 5~5''... Filter circuit, 6~6''...preamplifier circuit, 7~7''...STC circuit, 8~8''...linear detection circuit, 9...addition circuit, 10...2nd power circuit,
11... Integrating circuit, 12... A/D conversion circuit, 13
...Arithmetic section, 14...Display section. Patent applicant Japan Radio Co., Ltd.

Claims (1)

[Claims] To remove the interference component of the received sound pressure power caused by mutual sound wave interference between fish bodies, measure the basic component of the received sound pressure power corresponding to the amount of fish school, and correct the electroacoustic coefficient with respect to the basic component. A method for measuring the amount of fish schools, comprising means for simultaneously or time-divisionally transmitting a plurality of ultrasonic pulses having a plurality of frequencies as carrier waves, a means for correcting propagation attenuation of received sound pressure power of the plurality of frequencies; and means for adding and averaging the corrected power, thereby instantly removing the interference component and accurately measuring the amount of fish each time it is received.