JPH0255754B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a technique for removing unnecessary signals such as noise contained in a received amplified signal obtained using a radar, an underwater detection device, or the like.

(Prior art) Conventionally, methods for removing unnecessary waves include subtracting a signal obtained by integrating the raw signal from the raw signal (Japanese Patent Application Laid-Open No. 1983-99291), and correlation processing for signals above a certain level. What to do (Unexamined Japanese Patent Publication 1973-
No. 59291) is used.

(Problem to be solved by the invention) However, the underwater situation, the influence of other devices,
The occurrence of the above-mentioned noise varies depending on various external conditions such as the temperature around the circuit, and in such cases, it is difficult to remove unnecessary waves even if the above-mentioned conventional techniques are used individually.

(Means for Solving the Problems) The present invention has been made in view of the above, and it transmits a detection pulse, removes unnecessary waves included in the received return reflected waves, and further performs correlation. In fish finders and similar devices designed to remove interference waves, the return reflected waves are integrated and the return reflected waves are gated output only during the period in which the level of the return reflection waves is equal to or higher than the output level of the integrating circuit. It is characterized by comprising a first means and a second means configured to perform correlation processing on the output signal obtained by comparing the level of the gate output signal level with a preset setting level. The present invention provides an unnecessary signal removal device for fish finders and similar devices.

(Function) The present invention removes unnecessary waves in two stages: the first means and the second means.

The original reflected signal is supplied to the second means without undergoing any level change, and correlation processing is performed for signals above a certain level.

(Example) The present invention will be described below with reference to drawings based on an example of an underwater detection device.

1 is a transducer that repeatedly transmits ultrasonic pulses and receives the returned reflected waves; 2 is an amplification and detection circuit that amplifies and detects the received signal obtained by the transducer 1 (Figure 2a) It is. The received amplified signal from the amplification/detection circuit 2 passes through a gate 3 and is displayed on a display 4. The display 4 is one in which a received signal is recorded, for example, while the recording pen travels from one end of the width of the recording paper to the other.

5 is based on the general signal width from the target and experiments,
For example, it is an integrating circuit having a relatively large time constant of about 150 ms. Reference numeral 6 denotes a comparison circuit configured to compare the received amplified signal a and the integrated output signal (FIG. 2b) and send out a shaped pulse only during the period when the signal level of the received amplified signal a is high (FIG. 2c). .
Reference numeral 7 denotes a gate that is opened only during the output transmission period of the comparator circuit 6 and allows the received amplified signal a to pass through. The integration circuit 5, comparison circuit 6, and gate 7 constitute the first means.

8 corresponds to the second means, and the signal level of the signal d passed through the gate 7 and the set voltage
This is a comparison circuit that compares V ₀ and sends out a shaped pulse only during a period when the signal d level is high.

Reference numeral 9 denotes a known correlation circuit that performs multiple correlations on the output signal of the comparison circuit 8.

Next, the operation of the above configuration will be explained.

The received amplified signal a obtained by the amplification/detection circuit 2 is guided to the gate 3, and is also passed through the gate 7 and the integration circuit 5.
sent to The above received amplified signal a is a transmitted signal
S ₁ , interference signal S ₂ , fish school signal S ₃ , unnecessary signal S ₄ , and noise S ₅ . This received amplified signal a is integrated as a signal b by an integrating circuit 5 (however, the dotted line indicates signal a). Then, the received amplified signal a and the integrated signal b are compared in level in the comparator circuit 6, and a high-level shaped pulse is sent out only during the existence period of the signals _S1 to _S4 . The gate 7 is opened only during the high level period of the pulse c and the received amplified signal a is passed through, thereby obtaining a signal d having a level equal to each signal level of the original signal a. The signal d is compared with the set voltage V ₀ in the next-stage comparison circuit 8, and the signal D ₄ below the level V ₀ is considered to be an unnecessary signal and removed.
Furthermore, the interference wave _D3 is also removed in the correlation circuit 9. As the correlation circuit 9, a known type for selecting periodic signals and non-periodic signals can be used. The correlation output signals E ₁ and E ₂ are sent to the gate 3, and the gate 3 is opened only during this period to guide the transmission signal S ₁ of the received amplified signal a and the fish school signal S ₃ to the display 4.

(Effects of the Invention) As explained above, according to the present invention, the first means uses the comparator circuit 6 whose output level is always constant, and uses this output as a control signal for the gate 7 to generate the reflected signal. Since the gate processing is performed accurately without changing the level itself, and this output is led to the comparison circuit 8 of the second means in the next stage, it is possible to compare the level of the reflected signal and the set voltage V ₀ . becomes.

In this embodiment, noise removal was performed in the case of an underwater detection device, but in the case of a radar device, it can be easily implemented by setting the time constant of the integrating circuit separately.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.
FIG. 2 is a waveform diagram thereof.

Claims (1)

[Scope of Claims] 1. In a fish finder or similar device that emits a detection pulse and removes unnecessary waves included in the received return reflected waves, a signal obtained by supplying the signal to a display and displays it, an integrating circuit that integrates the reflected wave; and a first comparison circuit that compares the output signal of the integrating circuit with the returning reflected wave and sends out a control signal during a period in which the level of the returning reflected wave is equal to or higher than the output level of the integrating circuit. and a first gate which allows the return reflected wave to pass through when the input terminal thereof is supplied with the return reflection wave and a control signal is applied from the first comparison circuit to its control terminal; and the first gate a second comparison circuit that compares the return wave that has passed through the reference signal with a reference signal at a preset level and sends an output signal when the level of the return wave is equal to or higher than the level of the reference signal; and a correlation circuit that performs correlation processing on the output signal sent out from the second comparator circuit; An unnecessary signal removal device for fish finders and similar devices, comprising a second gate that passes the return reflected wave and supplies it to a display device.