JPS60231190A - Echo detector - Google Patents

Abstract

PURPOSE:To enable the thorough detection of reflected waves from inside the bottom of water by keeping the gain of a receiving amplifier suppressed between the transmission of a wave pulse and the proximity of tye reception of the reflected wave from the wave propagation characteristic boundary. CONSTITUTION:A trigger pulse generated from a control circuit 11 is provided to a transmitter 12 from which an ultrasonic carrier frequency pulse signal is applied to a transmitter/receiver 14 through a transmission-reception switching circuit 13. Consequently, the transmitter/receiver 14 is excited to emit an ultrasonic pulse into water. The reflected signal from the bottom 15 of water is received with the transmitter/receiver 14 to be converted into an electrical signal, which is received with a receiver 16 via the transmission-reception switching circuit 13. Here, until the reflected signal from the wave propagation characteristic boundary, namely, the bottom 15 of water is received, the gain of the amplifier in the receiver 16 is kept suppressed and thus the gain of the receiving amplifier is elavated by an STC signal from an STC signal generator 26 from the proximity of the reception of the reflected signal.

Description

[Detailed Description of the Invention] "Industrial Application Field" This invention is an echo detector that transmits waves such as sound waves or radio waves as a base wave, receives the reflected waves, and detects reflective objects. Regarding.

``Prior Art'' Conventionally, in this type of echo detector, for example, a fish finder, a transmission trigger pulse is generated as shown in FIG. As shown in Figure 1B, the transmitter radiates a wave into the water and receives the reflected wave, or suppresses the gain of the amplifier used to amplify the received signal at the same time as the one-noculus occurs. , that bird is Ichino! Immediately from the trailing edge of the loop, its gain is gradually restored, that is, increased.

Reflected waves from far away have a greater amount of attenuation during their propagation, but the greater the attenuation, the greater the gain amplification of the reflected waves.If the reflected intensity at the reflecting object is the same, regardless of the distance. , so that it can be received at a uniform level. Such gain control is generally called STC (sensitivity time control).

For example, when entering the ground below the water bed and detecting objects buried in the water bed or the state of propagation loss under the water bed, for example,
Since the distance to the bottom of the water is relatively long, when receiving reflected waves from below the bottom of the water, there is no effect to increase the gain of the receiving amplifier, and the reflected waves from inside the bottom of the water are no longer active. Cannot be detected sufficiently. Alternatively, even at a relatively shallow water bottom, the gain of the receiving amplifier has already increased to some extent, so the range in which the gain can be increased is narrow, and in this respect, the gain cannot be increased sufficiently. In particular, compared to the propagation loss of sound waves underwater, the attenuation of sound waves in the ground beneath the water is even greater. It is desirable to rise faster than However, the conventional S
As mentioned earlier, in the TC, the gain has already finished increasing and reached the maximum gain when receiving the reflected signal below the water bottom, and the range in which the gain can be increased is narrow. 9. It was difficult to fully detect the conditions under the water.

An object of the present invention is to provide an echo detector that is capable of sufficiently detecting reflected waves from, for example, the inside of the water bottom.

"Structure of the Invention" According to the present invention, the gain of the receiving amplifier is suppressed from the time of transmitting the wave pulse, and the gain of the receiving amplifier is kept in the suppressed state up to the vicinity of the time of receiving the reflected wave from the wave propagation characteristic boundary.
After that, start increasing the gain. Therefore, for example, when detecting beneath the water bottom, the gain of the receiving amplifier begins to rise after receiving the reflected waves from the water bottom, the so-called bottom signal.
Therefore, the gain increase range can be widened and the rate of increase can be increased, and the reflected signal from below the seabed can be received with sufficient gain to cope with the rapid attenuation of waves under the seabed.

Embodiment Next, as an example of an echo detector according to the present invention, an underwater detector will be described with reference to the drawings. In FIG. 2, a trigger pulse is generated from the control circuit 11 as shown in FIG. is applied to the transducer 14 through the transmission/reception switching circuit 13, the transducer 14 is excited, and an ultrasonic pulse is emitted into the water, in this example, toward the bottom 15 of the water.

The signal reflected from water etc. is received by the transducer 14, converted into an electrical signal, and passed through the transceiver switching circuit 13 to the receiver 16.
Received in.

The reflected signals include, for example, as shown in FIG.
Then, a high-level reflected signal 19 from the water bottom 15 is received, and further below (inside) the water bottom 15, a reflected signal 21 corresponding to the geology and buried objects is subsequently received.

This reflected reception signal is converted into a digital signal by the A-D converter 22 and stored in the Bach memory 23, and the reflected signal stored in the Bach memory 23 is transferred to the main memory 24. The main memory 24 is repeatedly read out, and each reflected signal is displayed on the display 25 as one display line.

The display 25 scans a rectangular display surface horizontally and vertically by main scanning and sub-scanning, and is, for example, a device similar to a television receiver. On the display surface, display lines based on the respective reflected signals are arranged and displayed in parallel in order of oldest to oldest.

An STC signal generator 26 is provided, and the STC signal generator 2
The output of 6 controls the gain of the receive amplifier in receiver 16. In the STC signal generator 26, for example, as shown in FIG. 3, one end of a resistor 28 is connected to a power supply terminal 27, and the other end of the resistor 28 is grounded through a capacitor 29. In parallel with the capacitor 29, a transistor 31
is connected, and the base of the transistor 31 is connected to the input terminal 32.
When the transistor 31 is in a conductive state because the transistor 31 is in a conductive state, the voltage on the capacitor 29 is 0, the terminal 32 is at a low level, and the transistor 3
1 becomes non-conductive, the voltage across the capacitor 29 increases from terminal 27, depending on the specific number of resistors 28 and capacitors 29, and this voltage increases from terminal 33 to ! 7 is supplied as an STC signal to the amplifier in the receiver 16 of FIG. 2, and its gain is controlled.

In this embodiment, the wave propagation characteristic boundary, i.e., in this example, the boundary between the water and the geology of the bottom, is the reflected signal from the water bottom 15, so-called bottom signal 19 (FIG. 1C). During this period, the gain increase of the amplifier in the receiver 16 is suppressed, and the gain increase of the receiver 16 is started by the STC signal from the STC signal generator 26 from the vicinity of receiving the bottom signal 19.

For example, in FIG. 2, a bottom stopper circuit 34 is provided which detects the bottom signal 19 and is similar to that generally provided in conventional fish finders. It can be used. The bottom discharge output from the bottom plug discharge circuit 34 and the trigger pulse from the control circuit 11 are supplied to the STC suppression circuit 35. STC suppression circuit 35
For example, the trigger noggle from the control circuit 11 sets the frilag frog, and its high-level set output is supplied to the STC signal generator 26 through the switch 36, and the bottom plug is When the water bottom is detected from the output circuit 34 as shown in FIG. 1E, the detection output resets the STC suppression circuit 350 noritubflop.

Therefore, the STC suppression circuit 35 generates a suppression signal as shown in FIG. 1, which is applied to the STC signal generator 26, for example, at the terminal 32 in FIG.

While this suppression signal is being generated, the transistor 31 is conductive, the terminal 33 is set to a value close to the ground level, and the gain of the amplifier of the receiver 16 is set to a suppressed small value.

Upon detection of the bottom signal 19 (Fig. 1E), the suppression of the STC is released, and from this, the first signal is transmitted from the ST, C signal generator 26.
As shown in FIG. F, the signal that increases the gain gradually increases, that is, the voltage charged in the capacitor 29 in FIG. .

According to this configuration, when the reflected signal 19 from the water bottom 15 is obtained, the gain increases from that point on, and this gain can be increased significantly and rapidly. Therefore, the reflected signal 21 from within the water bottom 15 or from within the geology below the water bottom is rapidly attenuated depending on the distance from the water bottom, and the gain of the receiver 16 is accordingly rapidly attenuated. It can be raised.

In this way, the bottom signal 19 is automatically detected and the gain increase in STC control is suppressed from the transmission trigger signal to the detection of the bottom signal, but the suppression range can be freely set. You can also do that.

For example, in FIG. 2, the trigger pulse from the control circuit 11 is supplied to the monostable multivibrator 37, and the output from the monostable multivibrator 37 is sent to the STC suppression circuit 35.
Instead, it is supplied to the STC signal generator 26 through the switch 36. This monostable multipibrator 37 generates a suppression signal as shown in the first diagram, and the suppression period can be freely selected by manually setting the monostable multipibrake 370 time constant. Ru. For example, the output pulse width of the monostable multivibrator 37 may be appropriately determined by looking at the reception state of the reflected signal. To do this, for example, as shown in FIG. 4, the output of the A-D converter 22 is supplied to a transfer Bach circuit 39 through a buffer circuit 38, and the output of the A-D converter 22 is supplied to a delay circuit. 41 to the transfer buffer circuit 39.

The transfer buffer circuit 39 is, for example, a random access memory, so-called RAM, and when the number of pixels of one display line of the display device 25 is 256, half of that number, 12
Portion 3 of the transfer buffer circuit 39 for each of the 8 pixels
9ap39b. A-D converter 22
A reflected reception signal (FIG. 1C) is written in the area 39a from the control circuit 11 at a low speed through the horizontal buffer circuit 38, and the writing is continued until the end of an appropriate set period TI in the trench where the bottom reflected wave 19 is definitely obtained. , the number of writing samples is 128.

On the other hand, immediately after the detection of the bottom signal, the output of the delay circuit 41 is taken into the area 39b of the transfer buffer memory as a high-speed pulse as 128 pulses/glue during a certain period T2.

The delay amount of the delay circuit 41 is slightly delayed with respect to the output of the buffer circuit 38, so that the bottom of the water is displayed on the display screen. In this way, when data for 128 pixels in the normal display period TI and data for 128 pixels in the period T2 for underwater display are obtained in the transfer buffer memory 39, these data are transferred to the main memory 24. It is transferred as one display line data. As a result, as shown in FIG. 5, on the display surface 43 of the display 25, an oscillation line 44 corresponding to the oscillation line signal 17 is displayed on the upper half thereof, and a fish school image 45 corresponding to the fish school reflection signal 18 is displayed on the bottom. Bottom lines 46 corresponding to the signals 19 are displayed. In the lower half of the display surface 43, there is a bottom line 47 corresponding to the bottom signal 19 from dust detection, and an image 49 corresponding to the reflected signal 21 corresponding to changes in the underground medium or buried objects under the water bottom. is displayed. While observing the depth of the normal display water bottom line 46 in the upper half of the display surface 43, adjust the time constant of the monostable multi-pie break 37 in FIG. 2, and adjust the width of its output pulse (STC suppression signal) to an appropriate value. Can be a value.

``Effects of the Invention'' As described above, the present invention can be applied to, for example, an underwater detector to detect the state of reflections under the water, the geological formations, buried objects, etc.

It is possible to detect a weak reflected signal at the bottom by sufficiently increasing the sensitivity and increasing the gain. Moreover, in this case, since the amount of attenuation in the underground portion below the water bottom is even greater than that in the water, the time constant of the STC signal generation circuit 26 can be reduced to increase the rate of increase in receiver gain. For example, the gain increase speed of STC in conventional underwater detection can be increased by about 3 to 6 times, and the time constant in FIG. 3 can be reduced by about IA to 1/3. Also, the detection range below the water bottom varies depending on whether it is sludge or hard rock, and the detection range can be set depending on the situation. For example 10m~
The distance is set at approximately 40m. Therefore, it is only necessary to set the gain increase to the maximum value within the set detection range.

Note that this invention is applicable not only to echo detectors using such sound waves, but also to so-called underground radars, for example.
Even when emitting radio waves from the top of a large pile of snow toward the ground and receiving and detecting the reflected waves from within the ground, reflections from the boundary between the snow and the ground, that is, the interface of wave propagation characteristics. It can also be applied to other echo detectors, such as suppressing the gain increase until near reception and then increasing the gain.

[Brief explanation of drawings]

Fig. 1 is a time chart for explaining the present invention in detail, Fig. 2 is a block diagram showing an example in which the invention is applied to an underwater detector, and Fig. 3 is an example of an STC signal generation circuit. Figure 4 is a block diagram showing the data intake part for normal display and underwater display, Figure 5 is a connection diagram shown.
The figure shows an example of a normal display and a sub-seafloor display. 11: control circuit, 12: transmitter, 13: transmission/reception switching circuit,
14: Transducer/receiver, 15: Bottom, 16: Receiver, 22:
A-D converter, 23: Nogurahua memory, 24
: Main memory, 25: Display, 26: STC signal generation circuit, 34: Bottom detector, 35: STC suppression circuit, 37:
Monostable Multino N"l Ibrator. Patent applicant: Kohden Seisakusho Co., Ltd. Agent, Patent attorney: Takuya Kusano 1 Figure O 3 Figure 4 Figure 5 Procedural amendment (voluntary) 2. Name of the invention Echo detector 3. Person making the amendment Relationship to the case Patent applicant Koden Seisakusho Co., Ltd. 5, subject of the amendment Detailed explanation of the invention in the specification column 7, contents of the amendment (11 Specification page 9 line 14 “Bach circuit 39” changed to “Bach circuit 39”) Corrected to ``Buffer circuit 39.''

Claims (1)

[Claims] (1) In an echo detector in which the gain of the amplifier that transmits the wave, 1,000 rus, receives the reflected wave, and amplifies the received signal is increased over time, the wave
1. An echo detector characterized in that the echo detector is provided with means for suppressing the increase in gain of the amplifier from the time when the wave is transmitted to the vicinity where the reflected wave from the boundary of the wave propagation characteristic is received.