JPS6282381A - Sonar device - Google Patents

Abstract

PURPOSE:To find the relative speed between a target and a ship in the sea at the same time even with a linear frequency-modulated acoustic wave by finding the correla tion between both of them by varying the frequency of a transmitted signal, bit by bit, and calculating the quantity of frequency variation with which the correlation is maximum. CONSTITUTION:A received signal inputted to a receiver 22 is passed through a receiving amplification parts 31 and a BPF 32 to have its unnecessary band removed and also inputted to an AD converter 41, and the receive signal 100 form calculating and displaying the distance and the direction of the target is obtained. On the other hand, the received signal passed through the converter 41 and a fast Fourier transform processor 42 becomes a received signal expressed by frequency space and inputted to a window integrator 51. The received signal expressed by the frequency space is integrated by the integrator 51 within the range of the band width of the transmitted signal. Then, a peak detector 52 calculates the integral value corresponding to the difference between the position of the integral range of the received signal and the position of the band width of the transmitted signal and also finds the quantity of frequency variation corresponding to the maximum value. A signal corresponding to this quantity of variation is inputted to a speed calculator 53 to calculate the relative speed between the ship and target.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a sonar device, and particularly to a sonar device that uses linear frequency modulated sound waves and simultaneously detects the Doppler frequency between the reflected sound waves from the target and the emitted sound waves. The present invention relates to a sonar device capable of detecting the relative speed between a target and a ship equipped with the sonar device of the present invention.

[Conventional technology]

Sonar equipment that conventionally uses linear frequency modulation method is
Signal processing such as time compression is performed on the received signal reflected back from the target, and it is widely used because it significantly improves the signal-to-noise ratio even though the signal from the target is weak. However, in order to determine the relative speed between a target and a ship equipped with a sonar device by detecting the Doppler frequency of the reflected waves, it is usually possible to determine the relative speed only when the transmitted waves have a single frequency.

Therefore, in order to determine the relative speed between a target and a ship using the above-mentioned sonar device, a single-frequency sound wave is transmitted for a certain period of time (generally about the same time as the above-mentioned sonar device), and the frequency and reflected sound wave are The relative velocity is detected by finding the double frequency between the two frequencies.

Therefore, the function of determining the distance or direction to the target and the function of determining the relative speed between the target and the ship cannot be satisfied at the same time, and therefore, when collecting these necessary information, it takes more time than it takes to satisfy either function. This will require approximately twice as much time and power consumption.

[Problem that the invention seeks to solve]

The problem with the conventional technology that the present invention aims to solve is, as described above, that the function of determining the distance or direction to an underwater target and the function of determining the relative speed between the target and the ship cannot be satisfied at the same time. In order to satisfy these functions, approximately twice the time and power consumption are required compared to the time required to satisfy either function.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a tuner device V that overcomes the above-mentioned drawbacks.

[Means for Solving the Problems] The sonar device of the present invention is a sonar device that transmits and receives linear frequency modulated sound waves, and includes a transmitting means that outputs a linear frequency modulated transmission signal, and a sonar device that outputs a linear frequency modulated transmission signal; a wave transmitting/receiving means that inputs the electrical signal, converts it into a sound wave, radiates it into the water, converts the sound wave reflected from the target and returns to an electrical signal, and outputs it; and a wave transmitting and receiving means that inputs the electrical signal, amplifies it, and outputs a received signal a receiving means for digitizing and Fourier transforming the received signal to output a frequency domain signal; and a converting means for outputting a frequency domain signal by digitizing and Fourier transforming the received signal; It is configured to include a signal processing means that calculates the integral of the frequency width and outputs a relative velocity signal between the sonar device and the target based on the difference between the frequency band corresponding to the calculated value and the transmission frequency.

〔Example〕

Next, the present invention will be described in detail with reference to drawings showing embodiments. FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, FIGS. 2(a) and 2(b) are charts representing the transmission level of the present invention in frequency space and time space,
C) and (d) are graphs representing the reception level of the present invention in frequency space and time space, FIG. 3 (a) and (b)
4(a) and (b) are graphs showing the relationship and results of representing the received level of the present invention in frequency space and integrating it over the frequency width of the transmitted wave, and Figures 4(a) and (b) show the general transmitted level in time space and frequency space. The charts shown in FIGS. 4(C) and 4(d) are charts showing general reception levels in time space and frequency space.

An overview of embodiments of the present invention will be described.

First, looking at FIGS. 4(a) to 4(d), when the transmitted signal expressed in time and space has an amplitude expressed by h(t) with respect to time t as shown in FIG. 4(a) (t= 0 indicates the reference value)
radiates this into the ocean as sound waves. When this sound wave is reflected by the target and returns, the received signal has an amplitude expressed in time and space as f (t) with respect to time t, as shown in Figure 4 (t = 0 is the reference value). 4(a)).

If these transmitted signals and received signals are expressed in frequency space, H(
ω) and F ((=)) in Figure 4(d), the frequency angular velocity range of the received signal is 60M higher than that of the transmitted signal, and according to the Doppler effect, the target is approaching. It shows that

To implement this method, first, we convert the transmitted and received signals in time space to the transmitted signal H(Q) in frequency space, respectively.
and the received signal F (→).Then, while changing the frequency of either one little by little, the correlation between the two is determined, and the amount of frequency change ΔωM at which the correlation shows the maximum value is
All you have to do is ask for. Therefore, if either one of the transmitted signal H((b) and received signal F(ω) expressed in frequency space can be controlled to a constant or a form similar to a constant, the correlation calculation will be extremely simple. Therefore, a method will be described in which the transmission signal H (Company), which is easier to control out of these two signals, is made into a constant or a form similar to this.

Looking at Figures 2(a) to (d), the transmission signal H(ω) expressed in frequency space, which is one of the signals in the correlation calculation, is limited to a frequency range as shown in Figure 2(a). and its amplitude is constant. Transmission signal H(-
When converted into the temporal and spatial transmission signal h (g, Fig. 2 (
b) However, since the energy is dispersed over time, if a range that includes most of the energy (for example, the range that accounts for 80 cm of the total energy) is used for transmission, the amplitude will not change significantly (for example, this If 80% of the total energy is included in the range, the amplitude will be at least 64 inches from the maximum value), which is easy to implement. That's a certain amount of 1
When an increase in the difference is allowed, there is no problem even if the amplitude is constant.

In this way, the transmitted signal h(1) expressed in time and space is transmitted, and the received signal f(t) expressed in time and space shown in FIG. 2(C) is reflected from the target and returned. ) f, receive;
The received signal F(ω) is converted into a received signal F(ω) expressed in frequency space.

Then, while gradually changing the frequency of the transmitted signal H ((b)) and the received signal F(ω) expressed in frequency space, the correlation between the two is determined, and the correlation is the maximum value. What is necessary is to find the amount of frequency change ΔωM that indicates the following.The method will be described next.

Looking at Figures 3(a) and (b), since the transmitted signal H(ω) expressed in frequency space is constant within a pre-specified frequency band, the transmitted signal H(→ and the received signal F(
(b) To find the correlation with good. When finding the maximum value of the window integral corresponding to that position, as shown in Figure 3(b), the position of the integration range of the received signal F(ω) and the position of the bandwidth of the transmitted signal H((b)) must be difference Δω
is the horizontal axis, and the corresponding integral value A(Δω) is calculated as shown in Fig. 3(b), and the frequency change amount Δω indicates the maximum value.
Just find M. This is the amount of Doppler change.

In addition, especially when dealing with linear frequency modulated (LFM) signals, if we focus on a certain frequency among the frequencies of the modulated signal, the transmitted signal h(t ) (near t=0), it can be considered that the winning margin as mentioned earlier will decrease.

Next, an embodiment of the present invention will be described, focusing on its configuration and operation. As shown in FIG. 1, this embodiment includes a transmitting means 1, a wave transmitting/receiving means 2, a receiving means 3, a converting means 4, and a signal processing means 5.

The transmission means 1 includes a transmission oscillation section 11 and a transmission amplification section 12, the transmission oscillation section 11 generates a linear frequency modulated (LFM) transmission signal, the output thereof is power amplified by the transmission amplification section 12, A transmission signal with the necessary power is applied to the wave transmitter 21 of the wave transmitting/receiving means.

The wave transmitting/receiving means 2 includes a wave transmitting section 21 and a wave receiving section 22. The wave transmitting section 21 converts the transmitted signal into a sound wave, radiates the sound wave into the sea, further passes through a path 91, and is reflected at the target 9. The signal passes through the path 92 and is converted into an electrical signal again by the receiver 22.
The signal is input to the reception amplification section 31 of the reception means 3.

The receiving means 3 includes a reception amplification section 31 and a band F wave device 32, and the electric signal input from the wave receiver 22 is transmitted to the telegraph amplification section 31.
The signal passes through the bandpass filter 32, is amplified, removes unnecessary bands, and is input to the AD converter 41 of the conversion means 4 as a received signal. At the same time, a received signal 100 is output to determine and display the distance and direction to the target.

The conversion means 4 includes an AD converter 41 and a high-speed 7-way converter 4.
2, and the received signal input from the band p-wave device 32 is
The received signal F((b) is digitized by the AD converter 41 and then expressed in frequency space by the fast Fourier transformer 42.
and is input to the window integrator 51 of the signal processing means 5.

The signal processing means 5 includes a window integrator 51, a peak detector 52, and a velocity calculator 53.
The received signal F((b) expressed in the frequency space input in 1 is sequentially window integrated (moving integral) within the bandwidth range of the transmitted signal H(ω) (see Figure 3(a)). From the results, the peak detector 52 further calculates the
As shown in b), the extremal value (Δω) corresponding to the difference Δω between the position of the integral range of the received signal F (target) and the position of the bandwidth of the transmitted signal H (→) is found (see Figure 3 (b)). ), the frequency change amount ΔωM corresponding to the maximum value is determined, and the signal corresponding to this is input to the speed calculator 53, where the relative speed between the ship and the target is calculated, and a relative speed signal 101 is output. be done.

As mentioned above, even with linear frequency modulated sound waves, which are generally used to determine the distance or direction to an underwater target, it is possible to simultaneously determine the relative speed between the underwater target and the ship. This is to provide a new sonar device.

〔Effect of the invention〕

As explained in detail above, the present invention makes it possible to measure relative velocity using the Doppler effect even with linear frequency modulated sound waves. This has the effect of simultaneously satisfying the function of determining the relative speed between the ship and the target, and further saving time and power consumption.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of an embodiment of the present invention. Figures 2 (a) and (b) are diagrams representing the transmission level of the present invention in frequency space and time space, Figure 2 (C
) and (d) are charts representing the received level of the present invention in frequency space and time space, and Figures 3 (a) and (b) represent the received level of the present invention in frequency space and are integrated over the frequency width of the transmitted wave. Diagrams representing relationships and their results, Part 4
Figures (a) and (b) are diagrams representing general transmission levels in time and frequency space, and Figures 4 (C) and (
d) is a chart showing general reception levels in time space and frequency space. 1... Transmission means, 2... Wave transmission/reception means,
3... Receiving means, 4... Conversion means, 5
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Claims (1)

[Claims] A sonar device that transmits and receives linear frequency modulated sound waves includes a transmitter that outputs a linear frequency modulated transmission signal, and a transmitter that inputs the transmission signal, converts it into a sound wave, emits it into the water, and reflects it from a target and returns. a wave transmitting/receiving means that converts the received sound wave into an electrical signal and outputs it; a receiving means that inputs the electrical signal, amplifies and filters it, and outputs a received signal; a conversion means for outputting a signal, a frequency domain signal that is shifted by a predetermined frequency, cut out at the modulation frequency width of the transmitted sound wave, and an integral of the modulated frequency width that is obtained, and a frequency band corresponding to the maximum value and the transmission frequency; A sonar device comprising signal processing means for outputting a relative velocity signal between the sonar device and a target based on the difference in speed.