RU2795389C1 - Method and device for active hydrolocation - Google Patents

Abstract

FIELD: searching and detecting marine objects.

SUBSTANCE: invention is related to one of the important areas of theory and practice of covering the hydroacoustic situation in the sea. In the proposed invention, the emission and reception paths are divided into two channels each, namely, the emission of probing and the reception of echo signals on one channel is carried out at a frequency f₁, on the other channel at a close (difference ± 10%) frequency f₂, while the outputs of both receiving channels are fed to a filter adder that extracts the spectrum component of the signal at the difference frequency f₃ = f₁-f₂, which reduces the loss in propagation of the echo signal with an increase in the noise resistance of the receiving channel at the difference frequency maintaining the concentration coefficient of the probing signal during its emission.

EFFECT: increased noise resistance of the receiving channel by increasing the signal-to-noise ratio.

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Description

The invention relates to one of the important areas of theory and practice of illumination of the hydroacoustic situation in the sea, namely, methods and means of increasing the range of active sonar.

The means of active sonar in the practice of navigation and the use of the marine environment in a wide range of other interests in different countries with access to the sea have appeared relatively recently, with the exception of well-known attempts to measure the speed of sound in water to the sound of bells. At the same time, all this time we are observers of more persistent and technically equipped attempts to develop and produce more and more effective means of solving long standing and emerging problems.

Possible ways to solve the problem under consideration can be analyzed using an analytical relationship that relates the value of the achieved range with the initial data in accordance with the so-called sonar equation [1]:

where: J _Smin - minimum signal intensity;

J _pom - interference intensity;

δ - recognition coefficient.

Substituting into expression (1) the values of physical parameters associated with the quantities included in it, namely, into the right side of the values associated with the range D and called propagation losses, and into the left side, called the detection potential, the rest, we obtain a generalized sonar equation in the form [ 2]:

Where: α _q - operating mode coefficient;

D - range;

p _co - reduced value of the level of the primary field;

R _a - acoustic power of the radiation channel;

γ ₁ γ ₂ - antenna concentration factors for radiation and reception;

ƒ, Δƒ - operating frequency and its bandwidth;

T - integration time (SHP mode) and radiation (ID and OP);

R _e - equivalent target radius at;

k _δ - threshold coefficient of the decisive link;

p _n0 - reduced interference pressure at the channel inlet; %

A _ƒ - sound anomaly factor;

β - sound attenuation in the marine environment.

), хотя это снизит коэффициент концентрации при излучении γ=4πSf²/с², где S - площадь антенны, а С - скорость звука в воде.As you can see, the solution of the task of increasing the range of the sonar without changing the energy parameters (P _a , γ ₁ , R _e , k _δ ), i.e. detection potential, represented by the left side of the equation, is possible only by reducing the signal propagation losses in the marine environment, which, in turn, is possible with a significant decrease in the frequency of the emitted signal f (multiplier

), although this will reduce the radiation concentration factor γ=4πSf ² /c ² , where S is the area of the antenna and C is the speed of sound in water.

The elimination of this shortcoming, i.e. preservation of the concentration coefficient during the emission of a high-frequency probing pulse and reduction of losses during its propagation is proposed by reducing the frequency of the received echo signal, choosing from its spectrum a component with a frequency lower than the frequency of the probing pulse.

The essence of the implementation of this proposal, as well as the main distinguishing feature of the invention, is the use of nonlinear phenomena [1], which accompany the reflection of the emitted pulse when the object is irradiated (mirror effect), and manifests itself in the form of spectrum expansion, a significant part of the intensity of which can be focused on a specific value its component, for example, with two-frequency radiation at a difference frequency, which as a result will significantly reduce the losses for the propagation of the reflected signal, thereby increasing its intensity and, consequently, the noise immunity of the sonar receiving channel, quantitatively expressed as the ratio of signal/noise values and, ultimately , with this, will increase its range.

The implementation of the proposed feature is illustrated in Fig. 1, which shows graphs of the decay of the intensity of the probing signal - curve 1 to point a) with single-frequency radiation and to point b) - with two-frequency radiation; the change in intensity at the point of reception - curve 2, the intersection of which with the threshold value allows you to determine the detection range of the located object. Curves 3 and 4 are plots of the decrease in the intensity of echo signals at both frequencies with a gain in the detection range in the form of D ₁ D ₂ .

The proposed method includes the emission and reception of signals reflected from objects of observation, the distinguishing feature of which is that a two-channel generator is used for their emission with a slight (up to 10%) channel difference in frequency and identical in other parameters, in particular, master oscillator circuits , modulators, power amplifiers and mode switches. The receiving path, as well as the radiation path, is two-channel, at the same frequencies and can be made according to the typical scheme "amplifier, carrier-frequency filter, detector and integrator" with the only difference that to separate the difference frequency from the spectrum of the sum of the signals, after the first filters, they go to the adder filtering the difference frequency and after this filter, to the detector and then to the integrator, as in the case of a typical circuit or to the indicator, as in this case.

This method is proposed to be implemented using a device (the block diagram is shown in Fig. 2, which includes two emission channels (elements 1, 3, 5 and 2, 4, 6) and two reception channels (elements 8 and 9) with using a dual-frequency transceiver antenna 13 with a "reception - transmission" switch 12, s (elements for subsequent processing and display of signals (elements 10 and 11).

In the composition shown in Fig. 2 block diagrams of a device that implements the described method, includes the following elements:

1, 2 - master generators for f ₁ and f ₂ ;

3, 4 - modulators f ₁ and f ₂ ;

5, 6 - power amplifiers f ₁ and f ₂ ;

7 - control unit;

8,9 - receiving channels on f ₁ and f ₂ ;

10 - filter adder;

11 - indicator device;

12 - switch reception-transmission;

13 - transceiver sonar antenna.

The technical result of the invention is to increase the noise immunity of the sonar receiving path, quantified as a signal-to-interference ratio, as a result of a decrease in echo signal propagation losses due to the transition to a frequency lower than the emitted one.

The technical result is achieved due to the fact that the emission and reception paths are divided into two channels each, and in such a way that the emission of probing signals on one channel is carried out at a frequency f ₁ , on the other channel - at a frequency f ₂ with a difference of ±10% from f ₁ , and the reception of signals reflected from the located objects is carried out on both channels at radiation frequencies f ₁ and f ₂ with their subsequent summation, separation by filtering the difference frequency and displaying the result on the indicator.

The foregoing allows us to assert that this invention meets the condition of patentability "novelty", since according to the available data from publicly available sources of information, the use of such a sonar is unknown. It also corresponds to the condition of patentability "inventive step", since the specified set of essential features of the device provides a new technical effect.

LITERATURE

1. Evtyutov A.P., Kolesnikov A.E., Korepin E.A. Reference book on hydroacoustics, - L .: "Shipbuilding", 1988

2. Shcheglov G.A. Probabilistic assessment of the range of the GAS. SPb. Proceedings of the VUNC VMF, 2018.

3. Soloviev I.V., Korolkov G.N., Baranenko A.A. Marine radio electronics. St. Petersburg: "Polytechnic", 2003.

Claims (2)

1. The method of active sonar, including the emission and reception of signals reflected from objects in the marine environment, characterized in that the emission and reception paths are divided into two channels each, while the emission of probing signals and the reception of echo signals are carried out simultaneously on one channel at a frequency f ₁ , on another channel at a frequency f ₂ that differs from the first by ±10%; reception of echo signals is carried out on both receiving channels with amplification and filtering at radiation frequencies, followed by summation, selection by filtering and display on the signal indicator of the difference frequency f ₃ =f ₂ -f ₁ . 2. An active sonar device, including paths of emission, reception and a receiving and emitting antenna, characterized in that the emission path includes two channels emitting probing pulses at frequencies f ₁ and f ₂ containing master oscillators, modulators and power amplifiers at these frequencies; the receiving path also includes two channels that receive echo signals at radiation frequencies and which include a filtering adder of signals from both channels, which extracts the difference frequency signal supplied to the indicator; the transmitting and emitting two-frequency antenna consists of an equal number of active elements at frequencies f ₁ and f ₂ , evenly distributed over the entire aperture of the antenna.

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