JPH0337145B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a ship that receives an underwater echo signal of an ultrasonic wave emitted into the water and detects a Doppler shift frequency from the underwater echo signal to determine the ship's speed. This invention relates to a speed measuring device.

[Prior Art] This type of ship speed measuring device selects echoes separately from echoes from other underwater objects, echoes from schools of fish, and noise,
For convenience of explanation, I will refer to it as the sea. ) It is necessary to measure the Doppler shift frequency of the echo signal.

Conventionally, this has been done by applying STC (Short Range Sensitivity Control) to the scattered echoes at short distances to reduce the gain of the receiver at short ranges, and by applying a seafloor predictive tracking gate. There is something. Furthermore, since the seafloor echo is the same as or longer than the transmission pulse width, there is a means to remove acoustic or electrical noise shorter than the transmission pulse width using a pulse width discrimination circuit.

[Problems to be Solved by the Invention] However, the above-mentioned method of applying a seabed prediction tracking gate can cope with cases where the topography changes of the seabed are relatively gradual, but when the seafloor has a steep slope, There was a problem in that the return time of the reflected waves changed greatly, making it impossible to cope with it.

This problem is also related to ship speed, and as the ship speed increases, the change in the return time of the reflected waves also increases. Therefore, in the conventional submarine tracking method,
There was a problem that if the ship was moving fast, it would not be possible to track the ship.

On the other hand, the pulse width discrimination circuit has conventionally been provided as a separate and independent circuit from the Doppler shift detection circuit. Therefore, if a pulse width discrimination circuit is provided and the noise is removed by the above-mentioned means, there is a drawback that the circuit configuration of the ship speed measuring device becomes complicated.

The present invention has been made to solve the above-mentioned problems, and its first purpose is to select the width of the tracking gate according to the inclination of the water bottom and the speed of the ship, and to prevent sudden topographical changes on the water bottom and changes in ship speed. An object of the present invention is to provide a ship speed measuring device that can correspond to the seabed and can reliably track the bottom of the water.

A second object of the present invention is to detect the Doppler shift frequency by incorporating a pulse width discrimination function internally to simplify the circuit, and at the same time to perform pulse width discrimination of the underwater echo signal, so that the detected Doppler shift frequency is effective. It is an object of the present invention to provide a ship speed measuring device that can determine whether or not

[Means for Solving the Problems] The present invention provides a ship speed measuring device that receives a bottom echo signal of an ultrasonic wave emitted into the water, detects a Doppler shift frequency from the bottom echo signal, and determines a ship. As a solution to the above problem, within the pulse width of the bottom echo signal envelope,
The wave number of the underwater echo signal and the wave number of the reference clock signal are each counted, and when each reaches a preset count value, a counting end signal is output for each, and a Doppler shift is detected by detecting the difference in the counting end time between the two. a Doppler shift detection means that monitors the output of each counting end signal, and when each counting end signal is output within a certain sampling period, determines that the bottom echo signal has a normal pulse width, and determines normality. a pulse width discrimination means for outputting a signal; a sounding means for detecting the measured depth by counting the time from ultrasonic transmission to reception of the bottom echo signal; At the same time, as a function of the ship speed, in the direction of travel, the tracking gate is set so that it is shorter in the shallow direction and longer in the deeper direction, and in the opposite direction, the tracking gate is set longer in the shallow direction and shorter in the deeper direction. calculation means for calculating the tracking gate width and calculating the tracking gate start timing and the gate end timing after the start of the next transmission from the tracking gate width and the detected depth; and the calculated tracking gate start timing. and tracking gate setting means for setting a tracking gate based on the gate end timing.

[Function] The present invention configured as described above has the function of setting an appropriate tracking gate according to the speed of the ship and the inclination of the water bottom, and the function of suppressing the comparatively short width pulse noise that appears in the tracking gate. It also has a function to remove.

First, the operation of the tracking gate setting function will be explained with reference to FIGS. 1 to 4. In addition, Fig. 1 is an explanatory diagram showing the influence of the movement of the ship and the inclination of the seabed on the propagation path of ultrasonic waves in front of the ship, and Fig. 2 is a waveform diagram showing the relationship between the time required from transmission to reception and the tracking gate. Figure 3 shows the slope angle of the seafloor and T _R /
A graph showing the relationship between T _L and FIG. 4 is an explanatory diagram showing the influence of the movement of the ship and the inclination of the seabed on the propagation path of ultrasonic waves behind the ship.

In FIG. 1, it is assumed that the ship is moving on the sea surface from _S1 to _S2 . First, at position S ₁ , when an ultrasonic wave is emitted from a transducer (not shown) in front of the ship (in the traveling direction) at an angle of depression θ, if the distance to the sea floor A is R ₁ , then the seafloor echo will be The time T until it is received is T=
2R ₁ /ρ.

Next, assume that when the ship advances and reaches _S2 , the topography of the seafloor changes as shown by C or C' depending on the inclination angle φ. In this case, the distance from S ₂
R ₂ becomes R ₁ − or R ₁ +′. Here, the time required from transmission to reception as shown in Figure 2.
Based on T ₁ , the front (shallow side) side T _L of the gate width is
Let T _L = 2/c, and the rear (deeper) side T _R is T _R
=2'/c, the ratio T _R /T _L between the two is given by the following equation.

T _R /T _L =2'/ρ・ρ/2BC=/BC = sinφ/sin(θ−φ)・sin(θ+φ)/ABs
inφ=sin(θ+φ)/sin(θ−φ) Now, if θ=60°, the above T _R /T _L becomes as follows.

T _R /T _L = sin (60 + φ) / sin (60 − φ) In Figure 3, at angles other than 0°, this ratio is
(T _R /T _L )>1. Therefore, the measurement depth is detected by counting the time from transmission to reception.
Based on the depth detected above, in the direction of travel:
By setting the gate width asymmetrically so that it is shorter on the shallow side and longer on the deeper side, it is possible to cope with the slope of the seabed.

On the other hand, in the above case, when ultrasonic waves are emitted to the rear of the ship (in the direction opposite to the direction of travel) at an angle of depression θ, the result will be as shown in FIG. 4. Figures 1 and 4
As is clear from a geometrical comparison with the figure, in the case of FIG. 4, the relationship between T _R and T _L is T _R <T _L. Therefore, regarding the direction opposite to the direction of travel,
By setting the tracking gate width asymmetrically so that it is longer on the shallower side and shorter on the deeper side, it is possible to cope with the slope of the seabed.

Next, the operation of the function of removing pulse noise will be explained.

In the above configuration, the Doppler shift detecting means counts the wave number of the submarine echo signal and the wave number of the reference clock signal up to a preset target number within the pulse width of the submarine echo signal envelope, thereby calculating the Doppler shift between the two. This is converted into a time difference at the end, and a reference clock is applied to this time difference to detect the Doppler shift frequency.

Further, the Doppler shift detection means performs a counting operation only while the submarine echo signal envelope is being input. Therefore, if the above target number is set to correspond to the width of the normal seafloor echo signal envelope, when normal seafloor echoes are input, within a certain sampling period,
When the counting of the wave number of the Shanghai underwater echo signal and the wave number of the reference clock signal both reaches the target number, the counting ends, and the Doppler shift detection means outputs a counting end signal. On the other hand, if the pulse width of the input echo signal is shorter than the width of the seafloor echo, the counting of the wavenumber of the seafloor echo signal and the wavenumber of the reference clock signal does not reach the target number, and a counting end signal is not output.

The pulse width discrimination means determines whether or not the echo signal is a normal submarine echo signal based on the presence or absence of the counting end signal.

As described above, according to the present invention, pulse-like noise can be removed by the pulse width discrimination means attached to the Doppler shift detection means, and the circuit configuration is simplified.

[Example] An example of the present invention will be described with reference to the drawings.

<Configuration of the first embodiment> FIG. 5 shows the configuration of the first embodiment of the ship speed measuring device of the present invention.

As shown in FIG. 5, the ship speed measuring device according to the first embodiment of the present invention includes an original oscillator 11 that generates a transmission frequency and a pulse repetition frequency, an STC generator 12, and a pulse generator from the original oscillator 11. A transmitter 13 that amplifies a transmission frequency signal that is intermittently output in accordance with a repetition frequency to form an excitation current, and the excitation current from the transmitter 13 transmits ultrasonic waves in the front and rear directions of a ship in the sea. A forward transducer 1 that emits waves at a constant angle of depression in each direction and receives reflected waves.
4, rear transducer 15, and front transducer 1
4 and the rear transducer 15, the transmitter/receiver switcher 16,1 switches between the excitation current and the received signal.
7, and receivers 18 and 19 that amplify the received waves.

This ship speed measurement device also includes Doppler shift detection means 20 and 21 for detecting a Doppler shift frequency from the received submarine echo signal frequency, and an AND gate circuits 38 and 39; a detection circuit 22 for detecting the received signal and detecting the submarine echo signal envelope;
23, AND gate circuits 24 and 25 forming a tracking gate that accepts only those at pre-predicted positions in the seafloor echo envelope, and forward tracking gate setting means for sending gate signals to the AND gate circuits 24 and 25, respectively. 26 and backward tracking gate setting means 27.

Furthermore, this ship speed measuring device has the above-mentioned original oscillator 1.
sounding means 2 which measures the depth of the seabed by using the leading edge of the pulse repetition frequency signal outputted from 1 as a start signal and using the pulse width discrimination means as a stop signal;
8, 29, and the Doppler shift detection means 20,
In addition to calculating the ship speed V using the Doppler shift frequency data and pulse width discrimination signal from 21,
The tracking gate position and width for the next measurement are calculated based on the ship speed information and the depth information from the sounding means 28 and 29, and the forward tracking gate setting means 2
6 and backward tracking gate setting means 27, and a display 31 for displaying ship speed information obtained by the calculation means 30.

The tracking gate, which is one of the characteristic functions of this embodiment, will be explained in more detail with reference to FIG. There are two systems for transmitting and receiving ultrasonic waves and processing signals, one for the front direction of the ship and one for the rear direction, but since the configurations of both systems are the same, for the sake of simplicity, we will use the following:
Only the system for the forward direction will be explained.

The tracking gate setting means 26 includes counters 43 and 44, and the counter 43 has a transmission trigger synchronized with the leading edge of the pulse repetition frequency that sets the timing of intermittent output of the high frequency signal. Sent from. counters 43, 44
are both composed of preset counters, the former is preset with the above-mentioned tracking gate start signal T ₁ -T _F , and the latter is preset with the above-mentioned end signal T _F +T _B , and both form a tracking gate signal. .

The sounding means 28 includes a flip-flop 45 and a counter 46.
5, the transmission trigger is sent from the original oscillator 11. The counter 46 is connected to the flip-flop 4
It is set by the sounding gate set by No. 5 and counts the reference clock.

The detection circuit 22 detects the submarine echo signal,
The envelope is taken out and sent to the AND gate circuit 24.

The Doppler shift detection means 20 receives the submarine echo signal envelope that has passed through the AND gate circuit 24, and detects the Doppler shift from the frequency of the submarine echo signal. Note that the configuration of the Doppler shift detection means 20 will be described later.

The calculation means 30 includes, for example, a microprocessor that performs calculations, an operating program for the microprocessor, a ROM (read-on memory) that stores coefficients K _F and K _B necessary for calculation, and a storage area necessary for calculation work. It is configured with RAM (random access memory). This calculation means 30
calculates the ship speed V based on the Doppler shift frequency from the Doppler shift detection means 20, and calculates the tracking gate start signal T ₁ −T _F from the ship speed V and depth T ₁
and the end signal T _F +T _B are calculated. In this embodiment, since the ultrasonic wave is radiated in the direction of movement of a ship, the coefficients K _F and K _B are set so that the relationship in magnitude thereof is K _F <K _B.

The AND gate circuit 24 is configured to control the opening and closing of the gate by the tracking gate signal which is inverted and inputted, and receives the submarine echo signal envelope from the receiver 18 when the tracking gate signal is at a low level.

Next, the configuration of the pulse width discrimination means, which is another characteristic function of this embodiment, and the Doppler shift detection means 20 attached thereto will be explained with reference to FIG.

In FIG. 8, the Doppler shift detection means 20 of this embodiment includes a D flip-flop circuit 32 and a counter 33 constituting a first counting means for counting the wave number of the seafloor echo signal, and a second counting means for counting the reference clock. A D flip-flop circuit 34 and a counter 35 constituting the means, and an exclusive OR gate circuit 36 and an AND gate circuit 37 constituting the Doppler shift detection means 20,
Furthermore, an AND gate circuit 38 constituting the pulse width discrimination means is connected.

The submarine echo signal envelope is input to the D terminals of the D flip-flop circuits 32 and 34, and the submarine echo signal frequency is input to the clock terminal Ck. The former reset terminal is connected to the Q terminal output of the counter 33, while the latter reset terminal is connected to the Q terminal output of the counter 35.
Terminal outputs are input, and the counters are reset by high level outputs from the Q terminals of the corresponding counters 33 and 35, respectively.

Further, the Q terminal outputs of the D flip-flop circuits 32 and 34 are input to the enable terminals E of the corresponding counters 33 and 35, respectively, and are also input to the exclusive OR gate circuit 36. The output of this exclusive OR gate circuit 36 is input to an AND gate circuit 37 together with a reference high frequency clock pulse.

The clock terminal Ck of the counter 33 receives the submarine frequency signal, while the clock terminal Ck of the counter 35 receives the reference high frequency clock pulse. These counters 33,3
The Q terminal outputs of No. 5 are both input to an AND gate circuit 38.

<Operation of the first embodiment> The tracking device of the present embodiment configured as described above has the following features:
It works as follows. This effect will be explained with reference to the above figures as well as FIGS. 6, 7, and 9.

The ship speed measuring device of this embodiment is provided with a forward system and an aft system, but since the functions of both are basically the same, the forward system will be described here. I will only explain.

An excitation signal that is intermittently outputted from the original oscillator 11 according to the pulse repetition frequency is amplified by the transmitter 13, switched by the transmitter/receiver switch 16, and sent to the forward transmitter/receiver 14. , converted into ultrasonic waves, and radiated into the sea in front of the ship at a constant angle of depression. At this time, a transmission trigger is sent to flip-flop circuit 45 and counter 43. In response to this, the flip-flop circuit 45 enters the set state, outputs the sounding gate _TG , and starts counting of the counter 46. Counter 46 begins counting the clock signals. Similarly, counter 43 starts counting clock signals upon receiving a transmission trigger.

On the other hand, reflected echoes from the ocean are input to the forward transducer 14, and the echoes are converted into electrical signals as submarine echo signals. This submarine echo signal is amplified by the receiver 18 via the transmitter/receiver switch 16, and is input to the Doppler shift detecting means 20 and the detection circuit 22. The detection circuit 22 extracts the envelope from this submarine echo signal, passes through the AND gate circuit 24, and outputs the envelope to the Doppler shift detection means 20.
send to

Here, the gate of the AND gate circuit 24 is controlled to open or close based on a predicted tracking gate signal generated by the forward tracking gate setting means 26 based on the depth and speed information from the previous measurement. That is, in the AND gate circuit 24, when the tracking gate signal is at a low level, it is inverted and inputted as a high level signal.
0 and is output to the flip-flop circuit 45.
Therefore, if the seabed echo signal envelope is input within the time period during which the predicted tracking gate signal is being input, it is determined to be a normal seabed reflection signal and can be input to the Doppler shift detection means 20. This Doppler shift detecting means 20 outputs a Doppler shift frequency and a pulse width discrimination signal by the operation described below.

On the other hand, in the sounding means 28, as described above, the flip-flop circuit 45 is set using the leading edge of the pulse repetition frequency signal from the original oscillator 11 as a start signal, and when the sounding gainer _TG is output, the counter 46 of the sounding means 28 is set. starts counting, and when the flip-flop 45 is reset by the input of the pulse width discrimination signal of the Doppler shift detection means 20, the sounding gate signal _TG is terminated and counting is stopped. The counted value of the counter 46 at this time is the depth _T1 since it counts the clock signal corresponding to the unit distance.

When the calculation means 30 receives the pulse width discrimination signal, it calculates the ship speed V from the Doppler shift frequency,
From the ship speed V and the coefficients K _F and K _B stored in advance, the gate width front side of the tracking gate can be calculated using the following formula.
Find T _F and posterior T _B.

T _F = K _F V T _B = K _B V After this, the calculating means 30 calculates the tracking gate start signal T ₁ −T _F from the depth T ₁ outputted from the counter 46 and the above T _F and T _B. , the end signal T _F +T _B is calculated. The start signal T ₁ -T _F and the end signal T _F +T _B are used in the next transmission cycle, and before the next transmission, the start signal T ₁ -T _F is preset in the counter 43 and the end signal T F +T B is used in the next transmission cycle. The signal T _F +T _B is preset into the counter 44.

In this state, when the next transmission trigger is output from the original oscillator 11, the flip-flop circuit 45
is set and starts the sounding gate TG.
It is set by this sounding gate TG and counts the reference clock. In this embodiment, a 750 Hz clock pulse is used as the reference clock.

Further, the counter 43 is activated by the above-mentioned transmission trigger, and counts down from the preset value of the start signal T ₁ -T _F using the same 750 Hz clock signal as above. Next, when the count value of the counter 43 becomes 0, the counter 44 is activated by its output, and the preset end signal T _F is activated.
Count down from the value of +T _B using the same clock signal as above. Then, the counter 44
When the count value becomes 0, the counting ends, and the low level region of the counters 43 and 44 during the counting period becomes the tracking gate signal.

This tracking gate signal is inverted and input to the AND gate circuit 24. With this, the current tracking gate is set.

In this example, the case where ultrasonic waves are emitted in the direction of movement of the ship is explained, so the coefficient K _F ,
K _B is set so that the magnitude relationship thereof is K _F <K _B. Therefore, T _F <T _B , and the tracking gate width becomes shorter in the shallower direction and longer in the deeper direction, with the detected depth T ₁ as a reference. Here, T _F functions as a gate when the depth is shallower than the previous measurement depth T ₁ , and T _B functions as a gate when it is deeper.

In addition, when emitting ultrasonic waves in the direction opposite to the direction in which the ship is traveling, the magnitude relationship of the coefficients K _F and K _B is
Set so that K _F > K _B. Therefore, T _FF >
T _B , and the tracking gate width is the depth detected above.
Based on T ₁ , it becomes longer on the shallow side and shorter on the deeper side.

Next, regarding the operation of the pulse width discrimination means,
This will be explained along with the operation of the Doppler shift detection means.

The submarine echo signal envelope passed through the AND gate circuit 24 is input to the D terminals of the D flip-flop circuits 32 and 34, and the submarine echo signal from the receiver 18 is input to the clock terminal Ck. As a result, the Q terminals of both become high level, which are input to the enable terminals of the corresponding counters 33 and 35, respectively, the counter 33 counts the wave number of the submarine echo signal, and the counter 35 receives the reference high frequency clock pulse. Count. Note that the counters 33 and 35 are reset at the leading edge of the submarine echo signal envelope prior to counting.

In this embodiment, both counters 33 and 35 are preset to the same number of values after being reset, and counting is performed by down-counting.

Here, if the ship is moving forward, the reflected echo undergoes a Doppler shift, and the frequency of the submarine echo signal increases, so the width of the burst wave pulse consisting of the same wave number becomes shorter. Therefore, as shown in FIG. 9A, the count of the counter 33 reaches the predetermined count value first. As a result, the Q terminal output of the counter 33 becomes high level.

In response to this, the D flip-flop circuit 3
2 is reset, and its Q terminal output changes to low level. Therefore, a low level is input to the enable terminal E of the counter 33, and counting is stopped. On the other hand, in the exclusive OR gate circuit 36, since the output of the D flip-flop circuit 32 is at a low level and the output of the D flip-flop circuit 34 is still at a high level, its output becomes a high level.

Therefore, the AND gate circuit 37 allows the reference high frequency clock pulse to pass while the exclusive OR gate circuit 36 is outputting a high level.

Thereafter, when the counter 35 counts up to a predetermined value, its Q terminal output becomes high level, the D flip-flop circuit 34 is reset, and the counter 35 stops counting, and the exclusive OR gate circuit 36 A low level is input to . As a result, the output of the exclusive OR gate circuit 36 changes to low level.

Therefore, the AND gate circuit 37 stops passing the reference high frequency clock pulse. The passage time of the reference high-frequency clock pulse in the AND gate circuit 37 corresponds to the difference in the counting end times of the counters 33 and 35. Therefore, the wave number of the reference high frequency clock pulse that has passed through the AND gate circuit 37 corresponds to the Doppler shift.

When both the counters 33 and 35 finish counting, the output of the AND gate circuit 38 becomes high level and outputs a pulse width discrimination signal. As described above, this pulse width discrimination signal is sent to the calculation means 30 and becomes a start signal for calculation of ship speed, etc., and is also sent to the sounding means 28 as a stop signal to perform the counting operation of the sounding means 28. to stop.

Note that when the ship is moving astern, the order in which the counters 33 and 35 complete counting is reversed from the above case.

By the way, when the envelope of the received signal is shorter than the counting time of the counters 33 and 35, as shown in FIG. 9B, the counters 33 and 35
Before the counting is completed, the D flip-flop circuit 32,
34's D terminal input becomes low level, and counting stops midway. In this case, the exclusive OR gate circuit 36 and the AND gate circuit 37 do not output pulses corresponding to Doppler shift, but only spike-like transient pulses. This transient pulse is not accepted by the subsequent circuit because the pulse width discrimination signal from the AND gate circuit 38 remains at a low level. Therefore,
These received signals are removed as noise.

In this way, according to this embodiment, a received signal with less than the normal pulse width is not accepted as a signal, and the Doppler shift frequency can be detected only from the signal with the normal pulse width.

Further, in this embodiment, since a seabed prediction tracking gate is set, noise within this tracking gate is mainly removed by the pulse width discrimination function of this embodiment.

<Second Embodiment> FIG. 10 shows the configuration of Doppler shift detection means, which is a feature of the second embodiment of the present invention.

The embodiment shown in the figure is an improvement of the first embodiment, in which a reset signal generating circuit 40 is added, and all other configurations are the same as those of the first embodiment. Therefore, the differences will be explained.

The reset signal generation circuit 40 includes a monostable multivibrator 41 and an AND gate circuit 4.
2.

The monostable multivibrator 41 is triggered at the leading edge of the submarine echo signal envelope and outputs a reset signal pulse from its Q terminal. Furthermore, in the AND gate circuit 42, the terminal output and the submarine echo signal envelope are ANDed, and this output is outputted to the D flip-flop circuit 32,
It is input to the D terminal of 34. As a result, while the counters 33, 35 are being reset, the submarine echo signal envelope is transferred to the D flip-flop circuit 32,
This prevents input to the D terminal of 34.

<Modifications of Embodiments> In each of the above embodiments, submarine echo signals are counted, but a configuration may also be adopted in which signals converted to intermediate frequencies are counted.

In addition, in each of the above embodiments, an application is shown to a ship speed measuring device for a ship navigating at sea.
The present invention can also be applied to a ship speed measuring device for ships navigating rivers, lakes, etc.

[Effects of the Invention] As explained above, in the present invention, the width of the tracking gate is selected according to the inclination of the water bottom and the speed of the ship, and it is possible to cope with sudden changes in topography of the water bottom and changes in ship speed.
It has the effect of reliably tracking the bottom of the water.

Further, the present invention simplifies the circuit by incorporating a pulse width discrimination function internally to detect the Doppler shift frequency, and at the same time performs pulse width discrimination of the underwater echo signal to determine whether or not the detected Doppler shift is valid. There is an effect that can be done.

[Brief explanation of the drawing]

FIGS. 1 to 4 are drawings for explaining the effects of the present invention, respectively, in which FIG. Figure 2 is a waveform diagram showing the relationship between the time required from transmission to reception and the tracking gate, Figure 3 is a graph showing the relationship between seabed slope angle and T _R /T _L , and Figure 4 is a graph showing the relationship between the seabed slope angle and T R /T L.
The figure is an explanatory diagram showing the influence of the movement of the ship and the inclination of the seabed on the propagation path of ultrasonic waves behind the ship. Figure 5 is a block diagram showing the configuration of the first embodiment of the ship speed measuring device of the present invention. Figure 6 is a block diagram showing the seabed tracking gate function in the ship speed measuring device of the first embodiment, FIG. 7 is a waveform diagram for explaining the action of the seabed tracking gate function in the above embodiment, and FIG. 8 is a block diagram showing the seabed tracking gate function in the ship speed measuring device of the first embodiment. FIG. 9 is a circuit diagram showing the configuration of the Doppler shift detection means in the first embodiment of the measuring device, and FIG. 9 is a waveform diagram showing the actions of the Doppler shift detection means and pulse width discrimination means in the above embodiment, and A is a normal seafloor echo. B indicates the effect when receiving a signal, B indicates the effect when receiving noise, and the 10th
The figure is a block diagram showing Doppler shift detection means in a ship speed measuring device according to a second embodiment of the present invention. 11... Original oscillator, 13... Transmitter, 14...
Forward transducer, 15... Rear transducer, 1
6, 17... Transmission/reception switch, 18, 19... Receiver, 20, 21... Doppler shift detection means, 2
2, 23...detection circuit, 24, 25...AND gate circuit, 26...forward tracking gate setting means,
27...Rearward tracking gate setting means, 28, 29
... Sounding means, 30 ... Calculation means, 31 ... Display device, 32, 34 ... D flip-flop circuit, 3
3, 35... Counter, 36... Exclusive OR gate circuit, 37, 38, 42... AND gate circuit,
40... Reset signal generation circuit, 41... Monostable multivibrator, 43, 44, 46
...Counter, 45...Flip-flop circuit.

Claims (1)

[Claims] 1. A ship speed measurement device that receives a bottom echo signal of ultrasonic waves emitted into the water and detects a dopshiraft frequency from the bottom echo signal to determine the ship speed, comprising: a pulse of a bottom echo signal envelope; within the width,
The wave number of the underwater echo signal and the wave number of the reference clock signal are each calculated, and when each reaches a preset count value, a counting end signal is output for each, and a Doppler shift is detected by detecting the difference in the counting end time between the two. A dopshiraft detection means that monitors the output of each counting end signal, and when each counting end signal is output within a certain sampling period, determines that the bottom echo signal has a normal pulse width, and determines normality. pulse width discrimination means for outputting a signal; sounding means for detecting the measured depth by counting the time from ultrasonic transmission to reception of the bottom echo signal; In addition to calculating the speed, as a function of the ship speed, in the traveling direction, the shallower the shallower,
The tracking gate width is calculated so that it is longer in the deeper direction, longer in the shallower direction and shorter in the deeper direction in the direction opposite to the direction of travel, and the next transmission is performed based on the tracking gate width and the detected depth above. A calculation means for calculating the tracking gate start timing and the gate end timing after the start, and a tracking gate setting means for setting the tracking gate from the calculated tracking gate start timing and the gate end timing. A ship speed measuring device characterized by: