JPH01257288A - Fish detector - Google Patents

Abstract

PURPOSE:To make it possible to increase received power equivalently without increasing the value of the peak transmitting power of an ultrasonic wave pulse, by arranging a binary phase modulator, a correlator and the like in a pseudo-noise signal (PN) generator. CONSTITUTION:A reference pulse PR is outputted from an ultrasonic wave oscillator 10 and introduced into one input terminal of a binary phase modulator 12. A received signal is reflected by underwater objects such as the school of fish and returned. After the signal is received with a transducer 20, the signal is amplified in a receiver amplifier 22 through a duplexer 18. The signal is introduced into one input terminal of a correlator 24. At this time, PN codes are inputted into the other input terminal of the correlator 24 from a PN code generator 14. Therefore, the received signal which agrees with the PN code of the transmitted wave is detected from the received signals by the correlation action in the correlator 24. Only the signal related to the underwater objects is introduced into a signal processor 26. In the processor 26, the image data of the underwater objects are stored in a frame memory. Thereafter, the image signal is sent into a display 28. Thus, the received power can be increased equivalently.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a fish finder that transmits and receives ultrasonic waves to determine and detect the presence of schools of fish in the sea. When repeatedly transmitting ultrasonic pulses from an installed ultrasonic transducer, the ultrasonic pulses are modulated with a pseudo-noise signal and transmitted, and the received signal reflected from the underwater object and returned to the transducer and the pseudo-noise signal are The present invention relates to a fish finder configured to correlate with noise signals and display images of underwater objects on a display.

[Background of the Invention] Conventionally, underwater acoustic equipment has been widely used to confirm objects existing underwater. A good example of this would be a fish finder. The fish finder uses a transducer consisting of a single vibrating element or a plurality of vibrating elements arranged in an appropriate shape to repeatedly emit sound waves, especially ultrasonic pulses, into the water in a predetermined range, and the waves are reflected from underwater objects. For example, a CRT (
This is a device that displays images on a cathode ray tube. In other words, focusing on the fact that the intensity of reflected echoes from underwater objects such as schools of fish is proportional to the size and density of the schools of fish, etc., a color is displayed on a display such as a CRT according to the amplitude level of the signal wave related to the reflected echoes. The presence of schools of fish, etc. is determined or confirmed by displaying the information or displaying it in shading on recording paper.

Incidentally, in such a fish finder, it is desired that the fish school detection distance, display resolution, and interference avoidance ability be high. In other words, when the detection distance is long, it is possible to detect schools of fish from a long distance and over a wide area, so the probability of overlooking or losing sight of a school of fish is extremely reduced.In addition, when the display resolution is high, schools of fish can be detected from a distance or in deep water. The possibility of identifying the fish species increases, and if it is the desired fish species, the time to cast the net can be started earlier.Furthermore, if the interference avoidance ability is high, it is possible to identify the fish school position according to the own fish finder. Both of these abilities are expected to contribute to increasing the catch.

Therefore, in order to meet these demands, we increased the peak transmission power value of the transmitted ultrasonic pulse to extend the detection distance.
On the other hand, efforts are being made to narrow the pulse width of the transmitted ultrasonic pulse in order to improve the distance resolution, and to make the frequency of the transmitted ultrasonic pulse variable in order to improve the ability to avoid interference.

However, in order to increase the peak transmission power value, it is necessary to increase the voltage of the transmitter circuit and ensure sufficient creepage distance, which leads to an increase in manufacturing costs due to increases in component material costs, etc. This has the disadvantage of increasing the size. Also,
Since the transmission pulse width and the peak transmission power value are in an antinomic relationship, an attempt to narrow the transmission pulse width causes the disadvantage that the power value emitted into the water decreases. Furthermore, various components are required to make the frequency variable, and it is important to simultaneously satisfy these components and improve performance.In other words, it is necessary to limit increases in cost and increase the size of the equipment to improve performance. This is proving to be an extremely difficult problem to improve.

[Object of the Invention] The present invention has been made to overcome the above-mentioned disadvantages, and when transmitting ultrasonic pulses into the water from a transducer constituting a fish finder, the ultrasonic pulses are converted into pseudo noise. The pulse width is increased by modulating the signal (PsendonoiseCodes, hereinafter referred to as PN code), and in this way
An image of the underwater object is displayed on the display by repeatedly transmitting N-code modulated ultrasonic pulses and correlating the received signal reflected from the underwater object and returned to the transducer with the PN code. It is an object of the present invention to provide a fish finder configured as follows, thereby making it possible to equivalently increase reception power without increasing the peak transmission power value of ultrasonic pulses.

[Means for Achieving the Object] In order to achieve the above object, the present invention repeatedly transmits an ultrasonic pulse as a transmission wave from a transducer, and the transmission wave is reflected from an underwater object to cause the transmission and reception to occur. In a fish finder that displays received waves returning to a wave detector on a display, a modulator and a correlation processor connected to a pseudo-noise signal generator are arranged, and a transmitted wave is generated from the pseudo-noise signal generator. The present invention is characterized in that the signal is modulated by a pseudo-noise signal, the received wave is correlated with the pseudo-noise signal, and the output signal is displayed on a display.

[Embodiments] Next, preferred embodiments of the fish finder according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic block diagram of a fish finder according to this embodiment, and the fish finder includes an ultrasonic oscillator 10. As shown in FIG. A reference pulse P output from the ultrasonic oscillator 10,
I is introduced into one input terminal of the binary phase modulator 12. A PN code from a PN code generator 14 is introduced into the other input terminal of the binary phase modulator 12. The binary phase modulator 12 modulates the reference pulses P and I with a PN code to obtain a PN code-modulated ultrasonic transmission pulse PUN (
A PN modulated ultrasonic transmission pulse (hereinafter referred to as a PN modulated ultrasonic transmission pulse) is introduced into the power amplifier 16. The power amplifier 16 amplifies the PN modulated ultrasonic transmission pulse P and introduces it into the transducer 20 via the transmitter/receiver switch 18 . Then, when the amplified PN modulated ultrasonic transmission pulse PIIN is applied to a large number of transducers (not shown) constituting the transducer 20, the transducer 20
Ultrasonic transmission pulses are emitted in a predetermined range (depression angle, turning angle) from the vehicle.

The reception signal reflected from an underwater object (not shown) such as a school of fish and returned is received by the ultrasonic transducer constituting the transducer 20 and then passed through the transmission/reception switch 18 to the reception amplifier 22. will be introduced in

The received signal introduced into the receiving amplifier 22 is amplified and introduced into one input terminal of the correlator 24 . In this case, the other input terminal of the correlator 24 is connected to the PN code generator 14.
Since the PN code is introduced from
Then, due to the correlation effect, the PN of the transmitted wave is determined from the received signal.
A received signal matching the code is detected and only the signal related to the underwater object is introduced into the signal processor 26. The signal processor 26 records image information related to the underwater object in a frame memory (not shown) constituting the signal processor 26, and then records the image information on the underwater object.
The video signal is sent to a display device 28 such as the following.

The fish finder according to the present invention is basically constructed as described above, and its functions and effects will be explained next.

The ultrasonic oscillator 10 using a Colpitts type, Hartley type, crystal oscillator, etc. has a gated oscillator configuration, and its output signal, the reference pulse PR, is as shown in FIG. Width P. This is a waveform gated by A, and its repetition period is T. Such a reference pulse P, is a binary phase modulator 1
is introduced into one input terminal of 2. On the other hand, a PN code, which is a digital signal, is introduced into the other input terminal of the binary phase modulator 12 from a PN code generator 14 . Therefore, the binary phase modulator 12 performs so-called PN code modulation, in which the reference pulse PR is binarized according to the PN code. The PN code modulated reference pulse is amplified, for example, by a push-pull type power amplifier 16 into a PN modulated ultrasonic transmission pulse PLAH of KW order.

Here, the PN modulated ultrasonic transmission pulse P is shown in FIG. In this case, the horizontal axis of FIG. 2 represents time, and the vertical axis represents the peak transmission power level. That is, in this embodiment, the transmission pulse width P□ of the PN modulated ultrasonic transmission pulse PUN is the pulse width P of the reference pulses P and I. Since it is extended six times compared to A, the state is equivalent to when six types of transmission pulses are emitted at once, and the power amplification factor of the power amplifier 16 is the same as that of the conventional technology. Therefore, it can be said that the peak transmission power value of the transmission pulse is equivalently increased six times. In other words, the detection distance capability has been expanded six times.

On the other hand, reference numeral 32 in FIG. 2 indicates an ultrasonic transmission pulse according to the prior art having a peak transmission power value equivalent to the PN modulated ultrasonic transmission pulse PIIN. in this case,
As mentioned above, it is technically difficult to narrow the pulse width and increase the transmission power level, so as the transmission power level increases, the pulse width becomes smaller than the transmission pulse width PwA of the reference pulses P and I. Even though the sheet metal and detection distance are doubled, the resolution is 1/1/2.
The inconvenience of dropping to 2 is obvious. Moreover, the internal temperature of the device increases due to the increased power consumption of the power amplifier 16, and due to the use of high voltage, it is necessary to ensure sufficient creepage distance of the circuit. In the prior art, when attempting to increase the peak transmission power value, disadvantages such as a decrease in reliability of the device, an increase in size, and a significant increase in cost become apparent. In addition, P.N.
When code modulation is used, the resolution can be changed by changing only the bit width of the PN code.

Therefore, the PN modulated ultrasonic transmission pulse Pt1N whose power has been amplified by the power amplifier 16 as described above is introduced into an ultrasonic transducer (not shown) constituting the transducer 20 via the transmitter/receiver switch 18. Then, a PN modulated ultrasonic transmission pulse P is emitted from the ultrasonic transducer in a predetermined direction. Next, when the PN modulated ultrasonic transmission pulse PUN collides with an underwater object such as a school of fish, a return signal reflected from the school of fish is introduced into the ultrasonic transducer of the transducer 20 as a received signal. The received signal introduced into the transducer 20 is introduced into the receiving amplifier 22 via the transmitting/receiving switch 18, where it is amplified by a predetermined factor and then A/D converted by an A/D converter (not shown) in the receiver. A quantity correlator 24 is input. Here, since the received signal is a received signal modulated with a PN code, the correlator 24 performs despread demodulation of the spectrum related to the PN code. That is, only reflected signals such as schools of fish are introduced into the signal processor 26 after correlation with the received signal is taken. In this case, the correlator 2 introduced into the signal processor 26
An example of the output signal 34 of 4 is shown in FIG. 2C. As can be understood from FIG.
The process may be performed during the time T8 between the transmission times t and t.

Next, it is stored in a frame memory (not shown) in the signal processor 26, and sent to the display 2 via a D/A converter (not shown).
8, an output signal related to the reflected signal is displayed. Note that the next PN modulated ultrasonic transmission pulse PLIN is generated at time t2, and the next reception process is executed, and in this way, the ultrasonic wave is transmitted, the reflected signal is received, and the received signal is displayed on the display 28. The display is carried out.

[Effects of the Invention] As described above, according to the present invention, a PN code modulator is provided in a fish finder, and an ultrasonic pulse is modulated with a PN code and transmitted into the water, and the received signal reflected from a school of fish etc. It receives the data, detects the correlation, and displays it on the display. Therefore, the transmission pulse width can be easily increased without increasing the peak value of the transmission power, and the reception power can be equivalently increased. As a result, the detection distance is improved. Further, since the peak power value is not increased, the device can be configured in a time-size manner even if the detection distance capability is improved. Furthermore, if the same detection ability as the conventional one is allowed, the device can be made smaller and lower in cost.

Furthermore, the PN code can be easily changed using a digital circuit, so even if another boat using a sheet metal fish finder with the same frequency approaches, you can easily avoid interference by changing the code. .

Moreover, in order to improve the resolution, it is only necessary to reduce the bit width of the PN signal, so there is no need to reduce the pulse width, and the complexity of having to adjust the transmission power to reduce it is eliminated. Ru. Furthermore, in order to improve the detection sensitivity of schools of fish, a technique has been known in which FM is applied to a carrier wave during a transmission pulse period, and the present invention can also achieve similar effects.

Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to these embodiments.
Of course, various improvements and changes in design are possible without departing from the gist of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a fish finder according to the present invention, FIG. 2 a is an explanatory diagram of an output signal of an ultrasonic oscillator in the fish finder shown in FIG. 1, and FIG. PN sent from the fish finder shown in
FIG. 2C is a schematic explanatory diagram of a code-modulated ultrasonic pulse and an ultrasonic pulse according to the prior art. FIG. 2C is an explanatory diagram of a processing period of a received signal in the fish finder shown in FIG. 10... Ultrasonic oscillator 12... Binary phase modulator 14... PN code generator 16... Power amplifier 18... Transmit/receive switch 20... Transducer/receiver 22... Receiving amplifier 24...correlator 2
6...Signal processor 28...Display procedure correction writing method) Display of 14 cases Patent application No. 297087 of 1988 2
, title of the invention Fish finder 3, relationship with the case of the person making the amendment Patent applicant 4, agent 7, "2 ``Figure a is an explanatory diagram.'' ``Figure 2 shows the output signal of the ultrasonic oscillator in the fish finder shown in Figure 1 and the PN code modulated signal transmitted from the fish finder. This is an explanatory diagram of the ultrasonic pulse according to the conventional technology, and the processing period of the received signal in the fish finder.

Claims (1)

[Claims] (1) In a fish finder that repeatedly transmits an ultrasonic pulse as a transmission wave from a transducer, and displays the received wave that is reflected from an underwater object and returns to the transducer on a display, A modulator and a correlation processor connected to the pseudo-noise signal generator are provided, and the transmitted wave is modulated by the pseudo-noise signal generated from the pseudo-noise signal generator, and the received wave is modulated by the pseudo-noise signal. A fish finder characterized in that it is configured to take a correlation and display its output signal on a display.