JPH0141949B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is provided in a ship speed measurement device that emits ultrasonic waves underwater, receives reflected waves from the bottom of the water, and detects ship speed using the Doppler effect. The present invention relates to a frequency detection circuit that detects a Doppler frequency, and particularly relates to a frequency detection circuit that has a function of removing received waves shorter than a specified width as noise.

[Prior art] A ship speed measuring device that uses the Doppler effect of ultrasonic waves uses an echo signal from the seabed (not limited to the sea, but for the sake of explanation, it will be referred to as Shanghai) as a signal from echoes from other underwater objects. , it is necessary to select it separately from echoes and noise from fish schools and measure the Doppler shift frequency of the seafloor 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 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] By the way, the pulse width discrimination circuit has conventionally been provided as an independent circuit separate from the Doppler frequency 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 in order to solve such drawbacks, and by incorporating a pulse width discrimination function internally to simplify the circuit, it detects the Doppler shift frequency and at the same time discriminates the pulse width of the submarine echo signal. It is an object of the present invention to provide a frequency detection circuit for a ship speed measurement device that can determine whether a Doppler frequency is valid or not.

[Means for Solving the Problems] The present invention is provided in a ship speed measurement device that emits ultrasonic waves into the water, receives reflected waves from the bottom of the water, and detects ship speed using the Doppler effect. As a solution to the above problems in frequency detection circuits that detect frequencies, the wave number of submarine frequency signals is counted within the pulse width of the submarine signal envelope, and when a preset count value is reached, a counting end signal is output. a first counting means; a second counting means for counting the wave number of the reference clock signal within the pulse width of the submarine signal envelope and outputting a counting end signal when a preset count value is reached; 1. A Doppler shift detection means that determines the counting end time difference of the second counting means and detects the Doppler shift frequency, and monitors the output of the counting end signal of the first and second counting means, so that both of them receive the counting end signal. The apparatus is characterized in that it comprises a pulse width discrimination means that determines that the submarine signal has a normal pulse width when output.

[Operation] In the above configuration, the first and second counting means count the wave number of the submarine frequency signal and the latter count the wave number of the reference clock signal up to a preset target number, respectively, so that the Doppler shift is achieved by both. It is converted into the time difference between the end of counting. The Doppler shift detection means applies a reference clock to this time difference to detect the Doppler shift frequency.

Further, the first and second counting means perform the counting operation only while the submarine signal envelope is being input. Therefore, if the above target number is set to correspond to the width of the normal submarine signal envelope, when normal submarine echoes are input,
Both the first and second counting means output 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, these counting means do not output a counting end signal.

The pulse width discriminator determines whether the echo signal is a normal submarine signal based on the presence or absence of the counting end signal.

As described above, according to the present invention, Doppler shift frequency detection and pulse width discrimination can be performed in one circuit, and the circuit configuration is simplified.

[Example] An example of the present invention will be described with reference to the drawings. Note that FIG. 1 is a block diagram showing an example of a ship speed measuring device to which the frequency detection circuit of the present invention is applied;
FIG. 2 is a circuit diagram showing the first embodiment of the frequency detection circuit of the present invention, FIGS. 3A and B are waveform diagrams showing the operation of the above embodiment, and FIG.
FIG. 2 is a circuit diagram showing an example.

Prior to describing the embodiments, first, the configuration of a ship speed measuring device to which the present invention is applied will be described.

As shown in FIG. 1, the ship speed measuring device includes an original oscillator 11 that generates a transmission frequency and a pulse repetition frequency, an STC generator 12, and an original oscillator 11 that generates a transmission frequency and a pulse repetition frequency.
a transmitter 13 that amplifies a transmission frequency signal that is intermittently output in accordance with a pulse repetition frequency to form an excitation current; and a forward transducer 14 and a rear transducer 1 that respectively radiate at a constant angle of depression in the rear direction and receive reflected waves.
5, transmitter/receiver switchers 16 and 17 that switch between the excitation current and the received signal for the forward transducer 14 and the rear transducer 15, and receivers 18 and 19 that amplify the received waves. There is.

This ship speed measuring device also includes frequency detection circuits 20 and 21 that detect the Doppler shift frequency from the received submarine signal frequency, and a detection circuit 2 that detects the received signal and detects the submarine signal envelope.
2, 23, tracking gate circuits 24, 25 that accept only those at pre-predicted positions among the seabed envelopes, and tracking gate circuits 24, 25;
A forward tracking gate signal generation circuit 26 and a rearward tracking gate signal generation circuit 27 are provided, each of which sends a gate signal to a forward tracking gate signal generating circuit 25.

Furthermore, this ship speed measuring device has the above-mentioned original oscillator 1.
Depth counters 28 and 29 measure the depth of the ocean floor using the leading edge of the pulse repetition frequency signal outputted from 1 as a start signal and the pulse width discrimination signal as a stop signal, and Doppler shift from the frequency detection circuits 20 and 21. The speed is calculated based on the frequency data and the pulse width discrimination signal, and the tracking gate position and width for the next measurement are calculated based on the ship speed information and the depth information from the depth counters 28 and 29, and the forward tracking gate signal generation circuit 2
6 and a rearward tracking gate signal generation circuit 27, and a display 31 for displaying ship speed information obtained by the arithmetic circuit 30.

The frequency detection circuits 20 and 21 are applied in this embodiment, and the details thereof are shown in FIG. Note that the frequency detection circuits 20 and 21 are
Since they have the same configuration, only one will be described below.

<Configuration of the first embodiment> In FIG. 2, the frequency detection circuit of the present embodiment includes a D flip-flop circuit 32 and a counter 33 constituting the first counting means, and the second
D flip-flop circuit 3 constituting the counting means of
4 and a counter 35, an exclusive OR gate circuit 36 and an AND gate circuit 37 constituting the Doppler shift detecting means, and an AND gate circuit 38 constituting the pulse width discriminating means.

A submarine signal envelope is input to the D terminals of the D flip-flop circuits 32 and 34, and a submarine frequency signal is input to the clock terminal Ck. In addition, the former reset terminal has
The Q terminal output of the counter 33 is inputted to the latter reset terminal, and the Q terminal output of the counter 35 is inputted to the latter reset terminal.
It is reset by high level output from the pin.

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 the 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> First, the operation of the ship speed measuring device to which this embodiment is applied will be described. The ship speed measurement device of this embodiment is provided with a forward circuit and an aft circuit, but since the functions of both are basically the same, only the forward circuit will be explained here. do.

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.

On the other hand, reflected echoes from the ocean are input to the forward transducer 14 and converted into electrical signals. This electrical signal passes through the transmitter/receiver switch 16, is amplified by the receiver 18, and is input as a submarine frequency signal to the frequency detection circuit 20 and the detection circuit 22. The detection circuit 22 extracts the envelope from this submarine frequency signal and sends it to the frequency detection circuit 20 via the tracking gate circuit 24.

Here, the opening/closing of the gate of the tracking gate circuit 24 is controlled by a predictive tracking gate signal generated by the forward tracking gate signal generation circuit 26 based on the depth and velocity information obtained from the previous measurement. Therefore, if the submarine 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 submarine reflection signal, and can be input to the frequency detection circuit 20. This frequency detection circuit 20 outputs a Doppler shift frequency and a pulse width discrimination signal through operations as described below.

On the other hand, the depth counter 28 starts counting the reference clock pulses using the leading edge of the pulse repetition frequency signal from the original oscillator 11 as a start signal. This counting is stopped by inputting the pulse width discrimination signal to the frequency detection circuit 20. The count value of the reference clock counted during this period corresponds to the sum of the seabed depth and the Doppler shift measurement time. This depth information is sent to the arithmetic circuit 30, and only the Doppler shift measurement time is subtracted to obtain true depth information.

Receiving the pulse width discrimination signal output from the frequency detection circuit 20, the calculation circuit 30 calculates the ship speed V from the Doppler shift frequency, and sends this to the display 31 for display. In addition, the arithmetic circuit 30
calculates the gate width of the predicted tracking gate for the next measurement from this ship speed V and the above depth information, sets the predicted position of the tracking gate, and uses this predicted tracking gate information for forward tracking. The signal is sent to the gate signal generation circuit 26. The circuit 26 counts the reference clock pulses and sends a tracking gate signal to the tracking gate circuit 24 based on the above information.

Next, the operation of the frequency detection circuit 20 will be explained with reference to the waveform diagrams shown in FIGS. 3A and 3B.

The submarine signal envelope that has passed through the tracking gate circuit 24 is input to the D terminals of the D flip-flop circuits 32 and 34, and the clock terminal
The submarine signal frequency from the receiver 18 is input to Ck. As a result, the Q terminals of both become high level, which causes the corresponding counters 33,
35 is input to the enable terminal of counter 3.
3 counts the submarine signal frequency, and counter 3
5 counts reference clock pulses. Note that the counters 33 and 35 are reset at the leading edge of the submarine 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 submarine signal frequency becomes higher, so the pulse width for the same wave number becomes shorter. Therefore, as shown in FIG. 3A, the counter 3
3 counts 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 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 clock pulse. The passage time of the reference clock pulse in the AND gate circuit 37 corresponds to the difference in the counting end times of the counters 33 and 35. Therefore, this AND gate circuit 37
The wave number of the reference clock pulse that has passed through 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.

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. 3B, 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, only transient pulses are output from the exclusive OR gate circuit 36 and the AND gate circuit 37, but this is because the pulse width discrimination signal from the AND gate circuit 38 remains at a low level. It is not accepted by this circuit. Therefore, these received signals are removed as noise.

In this way, according to the frequency detection circuit of 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.

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

<Second example> FIG. 4 shows the configuration of a 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 signal envelope and outputs a reset signal pulse from its Q terminal. Further, the AND gate circuit 42 performs a logical product of the terminal output and the submarine signal envelope, and this output is input to the D terminals of the D flip-flop circuits 32 and 34. As a result, the counters 33, 35
During the reset operation, the submarine signal envelope D is prevented from being input to the D terminals of the D flip-flop circuits 32 and 34.

<Modifications of Embodiments> In each of the above embodiments, an application is shown to a ship speed measuring device equipped with a seabed tracking gate, but the present invention is applicable to a ship speed measuring device not equipped with such a gate. It can also be applied to frequency detection circuits.

Further, in the above embodiment, the submarine signal frequency is counted, but it may be configured to count the frequency converted to an intermediate frequency in the receiver.

Furthermore, although each of the above embodiments is applied to a ship speed measuring device for ships navigating on the sea, the present invention can also be applied to a ship speed measuring device for ships navigating on rivers, lakes, etc. can.

[Effects of the Invention] As explained above, the present invention incorporates a pulse width discrimination function to simplify the circuit, detect the Doppler shift frequency, and at the same time discriminate the pulse width of the submarine echo signal, and detect the detected Doppler shift frequency. This has the effect of being able to determine whether a frequency is valid or not.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of a ship speed measuring device to which the frequency detection circuit of the present invention is applied, FIG. 2 is a circuit diagram showing a first embodiment of the frequency detection circuit of the present invention, and FIGS. 3A and B 4 is a waveform diagram showing the operation of the above embodiment, and FIG. 4 is a circuit diagram showing a second embodiment of the frequency detection circuit 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... Frequency detection circuit, 22, 23
...Detection circuit, 24, 25...Tracking gate circuit,
26...Forward tracking gate signal generation circuit, 27...
...Backward tracking gate signal generation circuit, 28, 29...
...Depth counter, 30...Arithmetic circuit, 31...Display device, 32, 34...D flip-flop circuit,
33, 35... Counter, 36... Exclusive OR gate circuit, 37, 38... AND gate circuit.

Claims (1)

[Claims] 1. A frequency detection circuit for detecting the Doppler frequency, which is installed in a ship speed measurement device that emits ultrasonic waves into the water, receives reflected waves from the bottom of the water, and detects the ship speed using the Doppler effect. a first counting means for counting the wave number of the submarine frequency signal within the pulse width of the submarine signal envelope and outputting a counting end signal when a preset count value is reached; Then, the second counting means outputs a counting end signal when the wave number of the reference clock signal reaches a preset count value, and the counting end time difference between the first and second counting means is determined. , a Doppler shift detection means for detecting a Doppler shift frequency, and the output of a counting end signal from the first and second counting means, and when both output a counting end signal, the submarine signal has a normal pulse width. What is claimed is: 1. A frequency detection circuit for a ship speed measuring device, comprising: pulse width discrimination means for determining whether the