JP2951045B2 - Ultrasonic reflection intensity measurement device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic reflection intensity measuring apparatus for searching and quantitatively measuring an underwater target using ultrasonic waves.

[0002]

2. Description of the Related Art A conventional ultrasonic reflection intensity measuring apparatus generally employs a circuit configuration shown in FIG. 4 except for a device which performs a pulse compression process in order to improve a distance resolution.
In the figure, 3 is a transmission pulse generation circuit, 4 is a power amplifier circuit, 6 is a TVG amplifier circuit, 7 is a bandpass filter for reception, 8
Is a detection circuit, 9 is a sine wave oscillation circuit, and 11 is a narrow band transmitter / receiver. The sine wave signal generated by the sine wave oscillating circuit 9 is gate-processed with the transmission pulse generated by the transmission pulse generation circuit 3 to obtain a transmission burst signal, and the transmission burst signal is power-amplified. Converted into ultrasonic pulses and transmitted underwater. An ultrasonic pulse transmitted underwater is reflected by an underwater target, and a reflected signal returned is received by a transmitter / receiver 11, the propagation attenuation is corrected by a TVG amplifier 6, and then passed through a reception band-pass filter 7 to be detected. The signal is detected by the circuit 8 and output.

In the case of the apparatus having the above-described configuration, the transmission frequency is a single frequency. Therefore, when another ship is transmitting ultrasonic pulses of the same frequency, the received signal is generated due to mutual interference of the ultrasonic pulses. There was a problem of being disturbed. In addition, when a plurality of underwater targets exist within the transmission pulse width, the phase of the reflected wave differs for each target due to the positional relationship of the underwater target, and the amplitude fluctuation of the received signal caused by the superposition of the reflected waves having different phases is removed. However, there is a problem that an error occurs when performing quantitative measurement of the underwater target.

In view of the above problem, conventionally, a circuit configuration shown in FIG. 5 is used, a plurality of transmission frequencies of different frequencies are used, and a signal after detection for each frequency is analogously converted by an averaging circuit 10. A system has been put into practical use in which the variation of the received signal is reduced by averaging to accurately measure the amount of the underwater target (publication number: 64-64).
5).

[0005]

The conventional ultrasonic reflection intensity measuring apparatus having the circuit configuration shown in FIG. 4 has a problem that a received signal is disturbed by an ultrasonic pulse of the same frequency from another ship.
When a plurality of underwater targets exist within the transmission pulse width, there is a problem that an error occurs in the quantitative measurement of the underwater target. The circuit configuration shown in FIG. Although the fluctuation of the received signal due to the positional relationship is reduced, the number of transmitting and receiving circuits is required by the number corresponding to the transmission frequency, and there is a problem that the apparatus becomes complicated and expensive. The present invention has been made in view of the above-described problem, and has a relatively simple circuit configuration and does not disturb a received signal due to a transmission pulse of another ship. It is an object of the present invention to provide an ultrasonic reflection intensity measuring device with a small number.

[0006]

An ultrasonic reflection intensity measuring apparatus according to the present invention comprises a white noise generating circuit for generating white noise, and a transmission band for extracting only a signal of a required frequency band from the white noise. A filter, a transmission pulse generation circuit,
A power amplifying circuit that amplifies power after gating an output signal from the transmission band-pass filter with a transmission pulse, and converts a transmission burst wave output from the power amplifying circuit into an ultrasonic pulse and transmits the underwater target to the underwater target; And a TV for performing propagation attenuation correction on the reflected signal received by the broadband transducer
It is characterized by comprising a G amplifier, a reception bandpass filter for extracting only a signal of a required frequency band from the TVG amplified signal, and a detection circuit for performing envelope detection on an output signal of the reception bandpass filter.

[0007]

By using band-limited white noise as a transmission signal, the frequency and phase of the carrier in the transmission pulse change every moment, so that ultrasonic pulses of a plurality of frequencies are transmitted while changing the phase. The same effect can be obtained. For this reason, the same effect as the transmission / reception system using a plurality of frequencies can be obtained with the same simple circuit configuration as the transmission / reception system using a single frequency.

[0008]

FIG. 1 shows a circuit configuration of an embodiment of the present invention.
In the figure, 3, 4, 6, 7, and 8 denote the same or corresponding components as those in FIG. 4, 1 denotes a white noise generating circuit,
2 is a transmission bandpass filter, and 5 is a wideband transducer.
FIG. 2 shows an example of a signal spectrum distribution of each circuit of the transmission system in the embodiment, and FIG. 3 shows an example of a signal waveform in each circuit of the embodiment of the present invention.

First, according to the embodiment of the present invention, an operation will be described in which the probability of receiving the interference of the transmission pulse of another ship is reduced and the fluctuation of the received signal is reduced. The frequency and phase of the white noise generated by the white noise generating circuit 1 change every moment, and the spectrum is uniformly distributed over the entire frequency region as shown in FIG. When this white noise is band-limited by the transmission band-pass filter 2,
As shown in FIG. 2B, a color signal having a frequency characteristic of a center frequency f ₀ and a bandwidth Δf is obtained. The colored signal is gated with a transmission pulse generated by the transmission pulse generation circuit 3 to obtain a transmission burst signal. This transmission burst signal is a colored signal having the frequency characteristic shown in FIG. 2C, and its frequency and phase change irregularly within the transmission pulse width. After the transmission burst signal is power-amplified by the power amplification circuit 4, it is subjected to electro-acoustic conversion by the broadband transmitter / receiver 5, and transmitted as underwater as ultrasonic pulses. The ultrasonic pulse reflected by the underwater target is received by the broadband transmitter / receiver 5, the propagation attenuation is corrected by the TVG amplifier circuit 6, and then passes through the reception bandpass filter 7 and the detection circuit 8.
The envelope component of the reflected echo is output. In this envelope component, the fluctuation of the received signal caused by the mutual interference with another ship and the positional relationship of the underwater target is significantly reduced as compared with the envelope component by a single frequency. Regarding mutual interference with other ships, it is clear that the probability of interference is significantly reduced because the frequency and phase of the transmission burst signal vary irregularly within the transmission pulse width.

[0010] Hereinafter, a description will be given of a reduction in fluctuation of a received signal. The instantaneous value Pr of the received sound pressure of the reflected echo from the underwater target is obtained by calculating the sound pressure of the reflected echo from the single target within the transmission pulse width by the total number of targets within the pulse width (for example, the total number of fish N when detecting a school of fish). , And is given by the following equation when the transmission frequency is single.

[0011]

(Equation 1)

Further, the instantaneous value Pr ² of the power of the received sound pressure based on the total number of tails existing within the pulse width is given by the following equation when the transmission frequency is single.

[0013]

(Equation 2)

Here, Pri and Prj are the reflection intensities of the target i and the target j, respectively, and {i,}
j is the initial phase of the target i and the target j in the carrier wave w. The first term of the above equation (2) is the sum of squares of the reflection intensity from each target, and the second term is a fluctuation component of the received signal caused by interference due to the positional relationship between the targets. In the case of a single frequency, it is impossible to remove the fluctuation component of the received signal for each reception. When the transmission burst signal is used as the transmission signal, the initial phases ψi and ψj in equation (2) differ for each carrier frequency within the transmission pulse width,

[0015]

(Equation 3)

Thus, the fluctuation component of the received signal is removed each time the signal is received, and the envelope signal becomes a stable signal reflecting only the reflection from the target.

Next, a detailed operation will be described. The white noise generated by the white noise generating circuit 1 is output by the transmission band-pass filter 2 as a color signal whose band is limited to a frequency band that can be transmitted and received by the wideband transmitter / receiver 5. FIG.
FIG. 3A shows an output signal waveform of the white noise generating circuit 1 and FIG.
(B) is an output signal waveform in which the amplitude of the transmission band-pass filter 2 is constant. The colored signal is gated with a transmission pulse generated by the transmission pulse generation circuit 3 to obtain a transmission burst signal. FIG. 3C shows a transmission burst signal waveform. After the transmission burst signal is power-amplified by the power amplification circuit 4, the transmission burst signal is subjected to electroacoustic conversion by the broadband transmitter / receiver 5 and transmitted underwater as ultrasonic pulses. The returned ultrasonic pulse reflected by the underwater target is subjected to acoustoelectric conversion by the broadband transducer 5, and a TVG amplifier 6
After the propagation attenuation is corrected by the
And is sent to the detection circuit 8. The reception band-pass filter 7 has a center frequency f ₀ and a bandwidth wider than the bandwidth Δf of the transmission band-pass filter 2.
The output signal of the reception band-pass filter 7 is envelope-detected by the detection circuit 8 and converted into a DC signal. The time constant of the detection circuit 8 is set to a value equal to the reciprocal of the transmission pulse width (time constant 1 / T when the pulse width is T). FIG. 3D shows an output signal waveform of the reception band-pass filter 7, and FIG.
The output signal waveform is a signal with a small variation that accurately reflects the reflection intensity of the underwater target.

By operating as described above, a stable signal corresponding to the reflection intensity of the underwater target can be obtained with a single transmitting / receiving circuit configuration without using a plurality of different transmitting frequencies requiring a plurality of transmitting / receiving circuits. By displaying the amplitude of this signal numerically or graphically, for example, the amount of fish school can be accurately grasped.

[0019]

As described above, according to the present invention,
With a single transmission / reception circuit configuration, it is possible to significantly reduce mutual interference with other ships, further reduce fluctuations in received signals due to the positional relationship of underwater targets, and obtain accurate reflection intensity. The effect of contributing to the simplification of the configuration and the reduction of the device scale is great.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a circuit configuration of an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a signal spectrum distribution of each circuit of a transmission system according to an embodiment of the present invention.

FIG. 3 is a diagram showing an example of a signal waveform of each circuit in one embodiment of the present invention.

FIG. 4 is a block diagram showing a circuit configuration of an example of a conventional ultrasonic reflection intensity measuring apparatus using a single frequency.

FIG. 5 is a block diagram showing a circuit configuration of an example of a conventional ultrasonic reflection intensity measuring device using a plurality of frequencies.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 White noise generation circuit 2 Transmission bandpass filter 3 Transmission pulse generation circuit 4 Power amplification circuit 5 Broadband transmitter / receiver 6 TVG amplification circuit 7 Reception bandpass filter 8 Detection circuit

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-1-257288 (JP, A) JP-A-55-107968 (JP, A) JP-A-3-87682 (JP, A) JP-A-4- 311109 (JP, A) JP-A-59-151075 (JP, A) JP-A-4-69787 (JP, U) JP-B 64-5655 (JP, B2) JP-B-49-43832 (JP, B2) (58) Field surveyed (Int.Cl. ⁶ , DB name) G01S 7/52-7/64 G01S 15/00-15/96

Claims (1)

(57) [Claims] 1. An ultrasonic reflection intensity measuring apparatus for searching for and quantitatively measuring an underwater target by using an ultrasonic wave, comprising: a white noise generating circuit for generating white noise; and a white noise generating circuit for generating white noise generated by the white noise generating circuit. A transmission bandpass filter for extracting only a signal in a necessary frequency band, a transmission pulse generation circuit for generating a transmission pulse, and an output signal from the transmission bandpass filter gated by a transmission pulse generated by the transmission pulse generation circuit. A power amplification circuit that amplifies power after processing, a broadband transducer that converts a transmission burst wave output from the power amplification circuit into an ultrasonic pulse, transmits the underwater wave, and receives a reflected signal from an underwater target, A TVG amplifying circuit for correcting propagation attenuation of a reflected signal received by the broadband transducer, and a TVG amplifying signal output from the TVG amplifying circuit 1. An ultrasonic reflection intensity measuring apparatus comprising: a reception bandpass filter for extracting only a signal of a required frequency band from a signal; and a detection circuit for performing envelope detection of an output signal of the reception bandpass filter.