JPH03216577A - Underwater acoustic detector - Google Patents

Abstract

PURPOSE:To extract only an objective signal by passing the output of a reception exclusive wide-band ultrasonic receiving means through a filter selecting frequency other than receiving objective frequency and reducing the amplification (mu)-factor of the receiving part of an apparatus during a time when the output thereof is a threshold value or more to remove an interference signal. CONSTITUTION:A transmission part 5 emits an ultrasonic electric signal into water as an ultrasonic signal on the basis of the timing signal of a control display part 8 by a transceiver SR 1 through a switching part 3. The reflected wave of an object to be detected is received by both of the SR 1 and a receiver R2 to be converted into an electric signal and, thereafter, the output of the SR 1 is subjected to signal processing in a receiving part 6 to be displayed on the display part 8 as an image. The output of the R2 is amplified by a wide-band amplifying part 4 to be passed through a filter 7 selecting frequency other than detection objective frequency f0 and, only during a time when an interference signal arrives as a control signal CL for controlling the gain of the receiving part 6 in a waveform shaping part 9, the gain of the receiving part 6 is reduced according to the intensity thereof. By this method, an interference signal is removed and jamming due to strain is prevented and only an objective signal can be extracted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an underwater acoustic detection device that performs underwater detection using ultrasonic waves.

[Conventional technology]

As is well known, underwater acoustic detection devices such as scanning sonar and fish finders that utilize ultrasonic waves emit ultrasonic waves to detect objects such as schools of fish. However, when a ship with a similar device comes near your own ship, the ultrasonic waves emitted by that device are received, amplified by the receiver, processed by IΔ, and then displayed on the screen. This interfering signal is displayed on the same screen as the received signal of a school of fish, etc., making it difficult to distinguish which signal is the intended signal, which may interfere with normal fish school detection, etc. Things often happen.

This interference wave is usually called interference or an interference wave, and various methods have been devised to remove this interference wave. For example, it is known that since interference is not repeatedly displayed at the same location on the screen, interference can be reduced by taking the average value of multiple screens. There is also a method that removes irregular interference signals by calculating correlation for each screen.

[Problem to be solved by the invention]

With the conventional underwater acoustic detection device described above, when taking the average value of multiple screens, the signals from schools of fish do not arrive with the same strength each time, so sometimes the images are small or large, and the average value is quite large. There is a drawback that the signal becomes smaller, and when correlation is taken, the signal of a small school of fish is displayed intermittently, so it has the disadvantage that it is not displayed due to the correlation. Also, if there is extremely strong interference from a short distance, the interference may appear in a ring shape on the screen, so there is a method to extract this characteristic and treat the ring-shaped signal as suspected of interference, but The reflected signal may also appear in a ring shape, so it must be used in conjunction with other judgment methods, and if it becomes a little weak, it will not become ring-shaped, so this method cannot be sufficiently effective. There are drawbacks.

In view of the above drawbacks, it is an object of the present invention to provide an underwater sound learning detection device that is less susceptible to interference by interference waves by lowering the amplification factor of the receiving section when interference waves arrive.

[Means to solve the problem]

The underwater detection device of the present invention includes a reception-only reception means separate from a transducer, which receives ultrasonic signals in a wide frequency range with almost uniform sensitivity, and a transmission means that receives ultrasonic signals with approximately uniform sensitivity. a filter having a function of selecting a signal of a frequency other than the target frequency to be transmitted and received by the transducer; a control signal output circuit that outputs a control signal while the output of the filter is equal to or higher than a threshold; and a control signal output circuit. and a control circuit that reduces the amplification factor of the receiver while the control signal is being output from the receiver.

[Effect]

Since the filter outputs only a signal of an unintended frequency, that is, an interference signal, the control circuit reduces the amplification factor of the receiving section only when there is an output from the filter.

(Example) Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the underwater sound learning detection device of the present invention, and FIG. 2(a). (b). (C) is a characteristic diagram showing the frequency characteristics of the receiving section 6, broadband amplifying section 4, and filter of the embodiment of FIG. 1, respectively, and FIG. 3 is a time chart showing the operation of the embodiment of FIG. 1.

Although each signal in FIG. 3 is an alternating current, only the positive polarity envelope is shown for clarity of the drawing.

The transmitting unit 5 generates an ultrasonic electrical signal according to the timing signal from the control display unit 8, and this electrical signal is transmitted to the transmitting/receiving switching unit 3.
The ultrasonic waves are switched to a transmitting state, converted into ultrasonic waves by the transducer 1, and radiated into the water. The ultrasonic signal reflected by the underwater sensing object is received by both the transducer 1 and the receiver 2. The ultrasonic signal received by the transducer 1 is converted into an electrical signal, and then sent to the receiver 6 as a signal X by the transmitter/receiver switching section 3. If the amplification factor of the receiving section 6 is not lowered by the control signal CL, the receiving section 6 operates as shown in FIG.
The signal X1 is amplified, processed, and displayed as an image on the control display unit 8.

On the other hand, the ultrasonic signal received by the receiver 2 is also converted into an electrical signal, amplified by the broadband amplifier section 4 having frequency characteristics as shown in FIG. 2(b), and sent to the filter section 7 as a signal Y1. The characteristics of the filter are as shown in Figure 2 (C), and are designed to have the highest attenuation at the frequency fo that is the purpose of detection, giving almost no attenuation to other frequencies. Therefore, the desired signal F of frequency fo received at time t2 does not appear as the output of the filter.

Here, at times 1, 13, interference signals i with frequencies f+ and f2
Consider the case where f,,if2 arrives. These signals are transmitted and received by a transducer l for the purpose of detection at a frequency f. Suppose you are far from. When such an interference signal arrives at a strong level, f included in the sound pressure and waveform distortion
. The components are outputted from the transducer l as if they were normal received signals.

Here, the interference signal if, . If2 also enters the receiver 2 as a strong sound pressure, but as shown in FIG. 2(b), the frequency f is determined by the frequency characteristics of the receiver 2 and the frequency characteristics of the broadband amplification section 4. Even the frequency f3, which is quite far from f
. Similarly, the signal is amplified to a predetermined level.

The amplified interference No. 5 is sent to the filter section 7.As mentioned above, the characteristics of this filter give almost no attenuation to f and f2, so it passes through here and is sent to the waveform shaping section 9 as a signal Y2. It will be done.

The waveform shaping section 9 shapes the ultrasonic electrical signal Y2 into a control signal CL convenient for controlling the gain of the receiving section 6, and sends it to the receiving Δ section 6. The receiver 6 receives the control signal CL and reduces the reception gain according to the strength of the interference signal during the time the interference signal arrives, so that as a result, the interference signal does not appear in the output signal x2 of the receiver 6. .

〔Effect of the invention〕

As explained above, the wooden invention distinguishes between the target signal to be detected and the interference signal based on the difference in frequency, and only when receiving the interference signal, reduces the amplification factor of the receiving section and removes the interference signal. The effect on the target signal is extremely small. In other words! Unlike averages and correlations for each screen, the target signal will not be weakened or not displayed, and there is no need to include a huge number of tuning circuits in the input circuit. Furthermore, the strong interference signal that enters the receiving section causes distortion due to the non-linear parts inside the receiving section, and since no interfering signal is generated due to this distortion, it is possible to extract only the signal for the purpose of detection. .

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the underwater acoustic detection device of the present invention, and FIGS. 2(a), (b), and (c) show the receiving section 6 and broadband amplification section of the embodiment of FIG. 1, respectively. 4. A characteristic diagram showing the frequency characteristics of the filter. FIG. 3 is a time chart showing the operation of the embodiment shown in FIG. l... Transducer/receiver, 2... Receiver, 3... Transmit/receive switching section, 4... Broadband amplifier, 5... Transmitting section, 6... Receiving section, 7... Filter , 8... Control display section, 9... Waveform shaping section.

Claims (1)

[Claims] 1. An underwater acoustic detection device that emits ultrasonic waves, receives reflected waves from an object to be detected underwater with a transducer, and amplifies them in a receiving section, comprising: a receiving means exclusively for reception that receives signals with substantially uniform sensitivity; a filter having a function of inputting the signal received by the receiving means and selecting a signal of a frequency other than the target frequency to be transmitted and received by the transducer; A control signal output circuit that outputs a control signal while the output of the filter is above a threshold value, and a control circuit that reduces the amplification factor of the receiving section while the control signal is output from the control signal output circuit. Features of underwater acoustic detection equipment.