JPH03216575A - Underwater acoustic detector - Google Patents

Abstract

PURPOSE:To remove the interference signal due to strain by a method wherein the output of a transceiver is inputted to a wide-band amplifying part and a BPF of detection objective frequency is connected to the output thereof and, when the input of the BPE is higher than the output thereof, the amplification (mu)-factor of the receiving part is reduced according to the height thereof. CONSTITUTION:A transmission part 4 emits an ultrasonic electric signal into water as an ultrasonic signal on the basis of the timing signal of a control display part 7 by a transceiver 1 through a switching part 2. The reflected wave from an object to be detected enters the transceiver 1 to be converted to an electric signal which in turn enters a receiving part 5 through the switching part 2. An interference signal of frequency other than a signal of detection objective frequency f0 enters the transceiver 1 and there is such a case that the level thereof is higher than that of the f0-signal. A BPF filter 6 of f0 is connected to the output of an amplifying part 3 and a comparator 8 compares the input and output of the filter 6 and, when the difference therebetween is a predetermined value or more, it is regarded as the interference signal and the gain of the receiving part 5 is temporarily lowered according to the signal intensity. By this constitution, the interference signal is removed and only the signal of an object to be detected can be displayed on the display screen of the display part 7.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an underwater acoustic detection device that emits ultrasonic waves from a transducer and performs underwater detection.

[Conventional technology]

As is well known, underwater acoustic detection devices such as sonar transmit and receive ultrasonic waves to detect objects such as schools of fish, but when a fishing boat equipped with a similar device approaches, the ultrasonic waves emitted by the device Since the desired signal is received and displayed on the screen, it is often difficult to distinguish between the desired signal and the interference signal (hereinafter referred to as interference or interfering signal).

The following methods are used to eliminate such interference.

1) Normally, the timing at which interference is received differs from screen to screen, so by taking the average of multiple screens, the level of interference that is not displayed at the same position decreases and is no longer displayed.

2) By correlating the screens, interference that does not appear in the same location is removed.

3) A receiver with wideband frequency characteristics is installed inside the transducer, and the signals obtained by this receiver are selected and the output signal is used to eliminate interference by not amplifying unintended signals. .

[Problem to be solved by the invention]

The above-mentioned conventional underwater acoustic detection device has the disadvantage that although the level of interference is reduced by taking the average, the signal from the school of fish that is the target of detection also fluctuates, so the signal level also decreases. However, when correlating the screen, there is a disadvantage that small schools of fish may not necessarily be received every time they are transmitted and received, so they disappear from the screen. Providing a wideband receiver in a transducer not only increases the price of the product, but also increases the installation space and the number of wires.

The object of the invention is to provide an underwater acoustic detection device that does not have the above-mentioned drawbacks.

[Means to solve the problem]

The underwater acoustic detection device of the present invention includes an amplifying section that amplifies the output signal of the transducer over a wide frequency range, and a filter that reduces the output of the amplifying section that has a frequency other than the frequency targeted for detection. , a comparator that outputs a control signal according to the height when the output of the amplifier section is higher than the output of the filter, and an amplification factor control means that reduces the amplification factor of the receiver section when the output of the comparator becomes active. and has.

[For production]

If the frequency of the desired signal transmitted and received by the transducer for the purpose of detection is fo, and the frequencies of the interference signals are f1, f2, etc., the transducer contains interference signals f,, f2, etc. in addition to f0. come. These signals that have passed through the transmitter/receiver switching unit are amplified by the receiver and displayed on the screen after signal processing.
2 signals etc. are displayed and it is not possible to distinguish the desired signal. Therefore, if the signal of a specific ultrasonic transducer element separated by the transmission/reception switching section is amplified and then passed through a filter with a bandpass function, the desired signal of the target frequency will not be attenuated, but the interference signal will depend on the characteristics of the filter. It will be subject to attenuation. The comparator compares the power and output of this filter, and if there is no difference, it is the signal of the target frequency,
A control signal for controlling the receiving gain is output and sent to the receiving section, and the gain is lowered so that the display related to the interference signal is not displayed.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a first embodiment of the underwater acoustic detection device of the present invention, and FIGS. 2 and 3 show frequency characteristics of the elements of the transducer 1 and the filter 6 of the embodiment shown in FIG. 1, respectively. FIG.

The control display section 7 generates a transmission timing signal and sends it to the transmission section 4. Based on the transmission timing signal, the transmitting section 4 sends an ultrasonic electrical signal to the transducer 1 via the transmitting/receiving switching section 2,
Emit it into the water as an ultrasonic signal. The ultrasonic signal that hits an object to be detected underwater is reflected and enters the transducer 1 again, where it is converted into an electrical signal and then sent to the receiver 5 via the transmitter/receiver switching section 2. The following signal is a desired signal of frequency f0 for the purpose of detection.

In addition to this frequency f signal, the transducer l receives a frequency f
Interference signals of 1 and f2 come in and are similarly sent to the receiving section 5. Normally, the transducer operates most efficiently at the frequency f0, so the output level of the signals at frequencies f,, f, should be low, but interference No. 3 differs from the reflected signal and is similar to other underwater acoustic waves. It may also be emitted from the device, and in this case the signal comes directly in, so the target frequency f6
The signal will come in at a higher level than the signal. The amplification section 3 amplifies the signal from the transmission/reception switching section 2 to a level suitable for signal processing. The filter section 6 outputs the output of the amplifier section 3 without attenuating the frequency fo, and attenuates the output of frequencies other than the frequency fo in accordance with the frequency characteristics of the filter (FIG. 3). The comparator 8 detects the difference between the signals of the amplifier 3 and the filter 6, and if the difference is less than a predetermined level, it is regarded as an interference signal, and it sends a control signal to temporarily lower the gain according to the strength of the interference signal. is sent to the receiving section 5. The receiving section 5 amplifies the output signal of the transmitting/receiving switching section 2, but if the control signal is working to lower the gain, the gain is temporarily lowered and no signal appears in the output. In this way, the interfering signal is removed and the signal is displayed on the control display section 7, so that only the signal of the detected object without the interfering signal is displayed on the screen.

Next, a second embodiment of the present invention will be described with reference to FIG.

The transducer 1 has m pieces in the circumferential direction and n stages in the axial direction, total m + n.
The elements are arranged in a cylindrical shape. During reception, the phases of the received signals of these elements are appropriately adjusted to form a reception beam, and the reception beam is rotated for underwater detection. At this time, the elements located approximately every 90 degrees of the first stage [1 (・Eal, Eb,, Ec1.
aISbl. The interference signal may be detected by using the sum of sC, , Sd1.

〔Effect of the invention〕

As explained above, the present invention first attenuates even if the signal manually input to the receiver is a strong interference signal, thereby preventing the occurrence of distortion, etc., and reducing the frequency of the interference signal due to distortion etc. As a result of the component being the same as the frequency of the target detection signal, problems such as interference not being completely removed do not occur.

In addition, it is only necessary to add a few circuits to the conventional receiver,
No special equipment or receiver is required. Furthermore, since it only uses the output of one or more transducer elements in the transducer, it can be extracted before the phase synthesis processing stage such as the scanning method, and is independent of the difference in subsequent processing methods. It has the excellent effect of being able to remove interference.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a first embodiment of the underwater acoustic detection device of the present invention, and FIGS. 2 and 3 show the frequency characteristics of the elements of the transducer 1 and the filter 6 of the embodiment of FIG. 1, respectively. FIG. 4 is a configuration diagram showing a second embodiment of the present invention. 1... Transmitter/receiver, 2... Transmit/receive switching section, 3... Amplifying section, 4...
Transmitting section, 5... Receiving section, 6...
・Filter, 7... Control display section, 8...
...Comparator.

Claims (1)

[Claims] 1. Underwater acoustic detection in which an ultrasonic wave is emitted from a transducer, the reflected wave from an object to be detected underwater is received by the transducer, amplified by the receiver, and then displayed on a display. The apparatus includes: an amplification section that amplifies the output signal of the transducer over a wide frequency range; a filter that attenuates the output of the amplification section that has a frequency other than the frequency targeted for detection; A comparator that outputs a control signal corresponding to the height when the output is higher than the output of the filter, and an amplification factor control means that reduces the amplification factor of the receiving section in accordance with the control signal of the comparator. An underwater acoustic detection device featuring: