RU2319984C2 - System for definition of the vibrations of water surface - Google Patents

Abstract

FIELD: invention refers to seismic and acoustic prospecting of the regions covered with water and may be used for warning about the waves of tsunamis arising due to lifting and sinking of significant masses of the ocean.

SUBSTANCE: system for definition of the vibrations of water surface has microbarographs spaced on fixed distances along the coastline. The microbarographs are switched through the comparison scheme to the alarming system. Additionally the system for definition of the vibrations of water surface has a memory block, a control point and two correlators.

EFFECT: increase of reliability of definition of the vibrations of water surface.

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Description

The proposed system relates to seismic and acoustic exploration of areas covered by water, and in particular to warning systems about tsunami waves arising from the rise or lowering of significant ocean water masses.

Known methods and systems for determining the occurrence of tsunami waves (ed. Certificate of the USSR No. 568.922, 769.455, 1.070.497, 1.584.585, 1.676.651, 1.721.563; RF patents No. 2.030.789, 2.034.312, 2.041 .476, 2.068.185, 2.093.861, 2.097.792, 2.168.747, 2.201.599, 2.240.570; US patents Nos. 3,943.514, 4.126.203, 5.124.651, 5.696.514; L. Brekhovsky M. On tsunamis and observations on the ultra-long-range sound propagation in the ocean - Bull. Of the Council on Seismology of the Academy of Sciences of the USSR, 1956, No. 2, pp. 8-11; Dykhan BD et al. First registration of tsunamis in the ocean (tsunami 23.02. 80 at the South Kuril Islands), Reports of the Academy of Sciences, vol. 257, No. 5, 1981, pp. 1088-1092 and others).

Of the known systems closest to the proposed one is a system that implements the "Method for determining the fluctuations of the water surface to determine the fluctuations of the water surface" (Auth. Certificate. USSR No. 1.070.497, G01V 1/38, 1982), which is selected as a prototype.

This system provides a forecast of the propagation of tsunami waves by obtaining information about the initial displacement of the ocean surface, but does not allow to reliably determine the fluctuations of the water surface.

An object of the invention is to increase the reliability of determining fluctuations in the water surface by determining the tsunami epicenter and using complex signals with phase shift keying to transmit an alarm message to a control point.

The problem is solved in that the system for determining the fluctuations of the water surface, containing microbarographs located in the form of a branched system along the coastline and connected through a comparison circuit to the warning system, is equipped with a memory unit, a control point and two correlators, each of which consists of series-connected to one of the extreme microbarographs of the multiplier, the second input of which is connected via an adjustable delay line to the output of the other extreme microbarograph, the lower filter x frequencies, an extreme controller and an adjustable delay line, the second output of which is the output of the correlator, the warning system is made in the form of a series-connected to the output of the comparison circuit of the first key, the second input of which through the first converter, the analog code is connected to the output of the first correlator, generator of the modulating code, the third input of which is connected to the output of the comparison circuit, the phase manipulator, the second input of which is connected to the output of the master oscillator, power amplifier and transmitting ant connected to the output of the second correlator of the second analog-code converter and the second key, the second input of which is connected to the output of the comparison circuit, and the output is connected to the second input of the modulating code generator, the control point is made in the form of a series-connected receiving antenna, high-frequency amplifier, a mixer, the second input of which is connected to the output of the local oscillator, an intermediate frequency amplifier, the first switch, the second input of which is connected to the output of the low-pass filter, narrowband filter, the second multiplier, the second input of which is connected to the output of the intermediate frequency amplifier, the low-pass filter and the recording and analysis unit, the second input of the comparison circuit is connected to the output of the memory unit, the microbarographs are spaced a fixed distance d, two pairs of extreme microbarographs are spaced a fixed distance nd, where n is the number of microbarographs.

The structural diagram of the system for determining the fluctuations of the water surface is presented in figure 1. Timing diagrams explaining the operation of the system are depicted in figure 2.

The system contains receivers 1.i (i = 1, 2, ..., n) of atmospheric pressure fluctuations (microbarographs) located in the form of a branched system along the coastline and connected through the comparison circuit 2 to the warning system 3, control point 7, two correlators 5 and 6, each of which consists of a multiplier 5.1 (6.1) connected in series to one of the extreme microbarographs 1.1 (1.n), the second input of which is connected through the adjustable delay line 5.4 (6.4) to the output of the other extreme microbarograph 1.2 (1. n-1), low-pass filter 5.2 (6.2) extreme unit 5.3 (6.3) and an adjustable delay line 5.4 (6.4), the second output of which is the output of correlator 5 (6).

The notification system 3 is made in the form of a first key 3.3, connected in series to the output of the comparison circuit 2, the second input of which through the first converter 3.1, the analog code is connected to the output of the first correlator 5, the modulator code generator 3.5, the third input of which is connected to the output of the comparison circuit 2, phase the manipulator 3.7, the second input of which is connected to the output of the master oscillator 3.6, power amplifier 3.8 and transmitting antenna 3.9, connected in series to the output of the second correlator 6 of the converter 3.2 analog-code and second 3.4 th key, a second input coupled to an output of the comparison circuit 2, and an output connected to the second input of the modulating code 3.5.

The control point 7 is made in the form of a series-connected receiving antenna 7.1, a high-frequency amplifier 7.2, a mixer 7.4, the second input of which is connected to the output of the local oscillator 7.3, the intermediate-frequency amplifier 7.5, the first multiplier 7.6, the second output of which is connected to the output of the low-pass filter 7.9, narrow-band filter 7.8. the second multiplier 7.7, the second input of which is connected to the output of the intermediate frequency amplifier 7.5, a low-pass filter 7.9 and a registration and analysis unit 7.10.

The second input of the comparison circuit 2 is connected to the output of the memory unit 4, the microbarographs are spaced a fixed distance d (measuring base), two pairs of extreme microbarographs 1.1 and 1.2, 1.n and 1.n-1 are spaced a fixed distance nd, where n is the number microbarographs.

The proposed system works as follows.

The principle of determining the fluctuations of the water surface is as follows.

The period of tsunami waves is in the range from 2 to 200 minutes, the wavelength is several tens to 300-400 km at a wave height of 1-2 m.The initial elevation of the ocean surface in the center of the generation of tsunami waves does not exceed several meters and it is practically impossible to detect their propagation.

However, at the time of the emergence of a tsunami, the area of the water area of radius R rises to a height h above the ocean surface - with frequencies of 0.001-0.5 Hz, which causes a change in atmospheric pressure, which can be recorded at a distance from the tsunami focus of at least 5 tsunami wavelengths, which is determined by the ratio last to noise.

At large distances compared with the radius R, this system is equivalent to the movement of a membrane placed in a rigid screen, leading to a change in atmospheric pressure at a distance l >> R

where V ₀ - the ascent rate of the water mass;

α is the angle between the vector of the observation point and the vertical (azimuth);

ρ is the specific pressure;

C is the speed of sound in the atmosphere;

λ and k are the wavelength and the radiation vector of the wave, respectively;

I ₁ - Bessel function of first order.

, πR²≈500 км², получим для изменения давления ≈10^-3÷10^-4 бар.The natural frequencies of the system are in the range of 0.001-0.5 Hz. Substituting in the formula (1) ρ≈1.29 * 10 ^-3 · g / cm ³ , C = 330 m / s, ω = 0.1 Hz, l = 1000 km,

, πR ² ≈500 km ² , we obtain for pressure changes ≈10 ^-3 ÷ 10 ^-4 bar.

The sensitivity of modern microbarographs significantly exceeds the indicated pressure range, and their frequency range allows you to record the pressure change with the frequencies of the natural oscillations of the tsunami source.

The velocity of propagation of pressure fluctuations in the atmosphere is on average twice the speed of tsunami waves. Therefore, at distances of the order of 1000 km, the difference in the arrival time of a sound pulse and a hydrodynamic wave is approximately 30 minutes and can be used to warn of the occurrence of distant tsunamis.

Fluctuations in atmospheric pressure from the epicenter of the tsunami EC are received by two pairs of microbarographs 1.i (i = 1, 2, ..., n). Moreover, the microbarographs are spaced a fixed distance d (measuring base). Two pairs of extreme microbarographs are spaced a fixed distance nd, where n is the number of microbarographs.

Oscillations of atmospheric pressure (sound signals) from the outputs of extreme microbarographs are supplied to two correlators 5 (6), each of which consists of a multiplier 5.1 (6.1), a low-pass filter 5.2 (6.2), an extreme regulator 5.3 (6.3) and an adjustable delay line 5.4 (6.4). The cross-correlation function R (τ ₁ ) [R (τ ₂ )] obtained at the output of correlator 5 (6) has a maximum for the value of the introduced controlled delay

τ ₁ = t ₁ -t ₂ , τ ₂ = t ₃ -t ₄ ,

where t ₁ and t ₂ - the time the sound signal travels the distances from the epicenter of the EC tsunami to the first 1.1 and second 1.2 extreme microbarographs;

t ₃ and t ₄ - the time the sound signal travels the distances from the epicenter of the EC tsunami to the second pair of extreme microbarographs, respectively.

The maximum values of R (τ ₁ ) and R (τ ₂ ) are supported with the help of extreme regulators 5.3 and 6.3, acting on blocks 5.4 and 6.4 of adjustable delay, respectively. The scale of blocks 5.4 and 6.4 of adjustable delay are graded directly in the values of the angular coordinates of the epicenter of the EC tsunami

where τ ₁ and τ ₂ are introduced into the corresponding channels of the delay of sound signals corresponding to the maximum of correlation functions.

The output signals of the correlators 5 and 6 are maximum when the planes in which the microbarographs 1.1 and 1.2, 1.n-1 and 1.n lie, are located perpendicular to the directions to the epicenter of the EC tsunami (Fig. 1).

The measured values of α ₁ and α ₂ in the converters 3.1 and 3.2 are converted into digital codes.

The averaged recorded atmospheric pressure fluctuations over a group of receivers (microbarographs) determine the moment of arrival of the first extremum of the extracted signal, are compared in comparison circuit 2 with a reference signal coming from memory unit 4. Based on the comparison results, a constant voltage is generated, which is supplied to the control inputs of the keys 3.3 and 3.4, opening them. In the initial state, keys 3.3 and 3.4 are always closed.

The azimuth values α ₁ and α ₂ in digital form from the outputs of the transducers 3.1 and 3.2 analog code through public keys 3.3 and 3.4 respectively are fed to the inputs of the generator 3.5 modulating code, where the modulating code M (t) (digital message) is generated (figure 2 .a), which is fed to the first input of the phase manipulator 3.7, to the second input of which a high-frequency oscillation is supplied from the output of the master oscillator 3.6 (Fig. 2, b)

U _c (t) = V _c cos (ω _c t + φ _c ), 0≤t≤T _c ,

where V _c , ω _c , φ _c , T _c - amplitude, carrier frequency, initial phase and duration of high-frequency oscillations.

At the output of the phase manipulator 3.7, a complex signal with phase shift keying (QPSK) is generated (Fig. 2, c)

U ₁ (t) = V _{1 cos [ω c t + φ k} (t) + φ c], 0≤t≤T c,

where φ _k (t) = {0, π} is the manipulated phase component that displays the phase manipulation law in accordance with the modulating code M (t) (Fig. 2, a), and φ _k (t) = const for kτ _e < t <(k + 1) τ _e and can change abruptly at t = kτ _e , i.e. on the border between elementary premises (K = 1, 2, ..., N-1);

τ _e , N - the duration and number of chips that make up the signal of duration T _c (T _c = τ _e N),

which, after amplification in the power amplifier 3.8, is radiated by the transmitting antenna 3.9 into the ether, it is captured by the receiving antenna 7.1 of control point 7 and through the high-frequency amplifier 7.2 is fed to the first input of the mixer 7.4. The oscillator 7.3 voltage is applied to the second input of the mixer 7.4

U _T (t) = V _T cos _{(w? T} + φ _r).

At the output of the mixer 7.4, voltages of combination frequencies are generated. The amplifier 7.5 allocated voltage of the intermediate frequency (figure 2, g)

U _PR (t) = V _PR cos [ω _PR t + φ _k (t) + φ _PR ], 0≤t≤T _c ,

Where

K ₁ - gear ratio of the mixer;

ω _PR = ω _c -ω _G - intermediate frequency;

φ _PR = φ _s -φ _G ,

which goes to the first inputs of the multiplier 7.6 and 7.7. The second input of the multiplier 7.7 is supplied with a reference voltage (figure 2, d)

U ₀ (t) = V ₀ cos (ω _PR t + φ _PR )

from the output of the narrowband filter 7.8. The output of the multiplier 7.7 is formed of a low-frequency voltage (Fig.2, e)

U _Н (t) = V _Н cosφ _к (t),

Where

To ₂ is the transmission coefficient of the multiplier, proportional to the modulating code M (t) (Fig.2, a), which is allocated by the low-pass filter 7.9 and fed to the second input of the multiplier 7.6. At the output of the latter, a harmonic oscillation is formed

U ₀ (t) = V ₂ cos (ω _PR t + φ _PR ) + V ₂ cos [ω _PR t + 2φ _k (t) + φ _PR ) = V ₀ cos (ω _PR t + φ _PR ),

where V ₀ = 2V ₂ ,

which is used as the reference voltage, is allocated by a narrow-band filter 7.8 and fed to the second input of the multiplier 7.7.

The low-frequency voltage U _Н (t) is fed to the input of the registration and analysis block 7.10, where the tsunami epicenter is determined.

Multipliers 7.6 and 7.7, a narrow-band filter 7.8 and a low-pass filter 7.9 form a QPSK demodulator that is free from the “reverse operation” phenomenon, which increases the reliability of extracting the modulating code M (t) from the received QPSK signal.

It should be noted that the well-known schemes of Pistolkors A.A., Sidorov V.I., Travina G.A., Kostas D.F., which also emit the reference voltage necessary for synchronous detection of PSK signals directly from the received PSK signal, inherent phenomenon of "reverse work", which limits the capabilities of these devices.

The effectiveness of the proposed system can be estimated by comparing the time reserve between the tsunamigenic process and the arrival of a destructive wave to the coast. So, at distances of the order of 1000 km from the epicenter, the tsunami wave travels for about 100 minutes, seismic disturbance ~ 5 minutes, sound disturbance along the underwater channel ~ 10 minutes and the atmospheric channel ~ 50 minutes, which is enough to ensure safety measures for manpower and equipment .

The system also allows to increase the reliability of the forecast by obtaining information about the initial displacement of the ocean surface.

Thus, the proposed system in comparison with the prototype and other technical solutions for a similar purpose provides an increase in the reliability of determining fluctuations in the water surface. This is achieved by determining the tsunami epicenter and using complex signals with phase shift keying to transmit alarm information to the control point.

Complex signals with phase shift keying open up new possibilities in the technique of transmitting discrete alarm messages from microbarographs located in the form of an extensive system along the coastline to a control point. These signals allow the use of a new type of selection - structural selection. This means that there is a new opportunity to separate complex QPSK signals operating in the same frequency band and at the same time intervals.

From the point of view of detection, complex QPSK signals have high energy and structural secrecy.

The energy secrecy of these signals is due to their high compressibility in time and spectrum with optimal processing, which reduces the instantaneous radiated power. As a result, a complex QPSK signal at the receiving point may be masked by noise and interference. Moreover, the energy of a complex QPSK signal is by no means small; it is simply distributed over the time-frequency domain so that at each point of this region the signal power is less than the power of noise and interference.

The structural secrecy of the QPSK signals is caused by a wide variety of their forms and significant ranges of parameter changes, which makes it difficult to optimize or at least quasi-optimal processing of complex QPSK signals of an a priori unknown structure in order to increase the sensitivity of the receiver.

Claims (1)

A system for determining water surface fluctuations, containing microbarographs located in the form of a branched system along the coastline and connected through a comparison circuit to a warning system, characterized in that it is equipped with a memory unit, a monitoring station and two correlators, each of which consists of series connected to one of the extreme microbarographs of the multiplier, the second input of which is connected via an adjustable delay line to the output of the other extreme microbarograph, low-pass filter, ex alarm controller and adjustable delay line, the second output of which is the output of the correlator, the warning system is made in the form of series-connected to the output of the comparison circuit of the first key, the second input of which is connected via the first converter to the analog-code to the output of the first correlator, generator of the modulating code, the third input of which connected to the output of the comparison circuit, a phase manipulator, the second input of which is connected to the output of the master oscillator, power amplifier and transmitting antenna, subsequently properly connected to the output of the second correlator, the second analog-code converter and the second key, the second input of which is connected to the output of the comparison circuit, and the output is connected to the second input of the modulating code generator, the control point is made in the form of a series-connected receiving antenna, high-frequency amplifier, mixer the second input of which is connected to the output of the local oscillator, the intermediate frequency amplifier, the first multiplier, the second input of which is connected to the output of the low-pass filter, narrow-band filter, W the second multiplier, the second input of which is connected to the output of the intermediate frequency amplifier, the low-pass filter and the recording and analysis unit, the second input of the comparison circuit is connected to the output of the memory block, the microbarographs are spaced a fixed distance d, two pairs of extreme microbarographs are spaced a fixed distance nd, where n is the number of microbarographs.

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