RU2503980C2 - System for determining water surface vibrations - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: system includes atmospheric pressure fluctuation receivers (microbarographs) 1.i (i= 1, 2, …, n), a comparator circuit 2, a notification system 3, a memory unit 4, first 5 and second 6 correlators, first 3.1 and second 3.2 analogue-to-number converters, first 3.3 and second 3.4 switches, a modulating code former 3.6, a master generator 3.6, a phase-shift keying device 3.7, a power amplifier 3.8, a transmitting antenna 3.0, multipliers 5.1 and 6.1, lowpass filters 5.2 and 6.2, optimal controllers 5.3 and 6.3, controlled delay lines 5.4 and 6.4. A control station 7 has a receiving antenna 7.1, a high-frequency amplifier 7.2, a heterodyne 7.3, a mixer 7.4, an intermediate frequency amplifier 7.5, first 7.6, second 7.7, third 7.11 and fourth 7.12 multipliers, first 7.8 and second 7.13 narrow bandpass filters, first 7.9 and second 7.14 lowpass filters, a recording and analysis unit 7.11, and first 7.15 and second 7.16 phase inverters.

EFFECT: high noise-immunity and reliability of receiving phase-shift keyed composite signals by attenuating narrow-band interference.

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Description

The proposed system relates to seismic and acoustic exploration of areas covered by water, namely, warning systems for 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, 1.584.586, 1.676.651, 1.721.563; RF patents No. 2.030.789, 2.034.312, 2.041 .476, 2.068.185, 2.093861, 2.007.792, 2.168.747, 2.201.599, 2.240.570, 2.319.984; US patents Nos. 3,943.514, 4.126.203, 5.124.651, 5.696.614; Brekhovsky LM On tsunamis and observations of ultra-long-distance 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; Dikarev VI. Safety, protection and salvation of a person. - SPb. , 2007, S.156-162 and others).

Of the known systems closest to the proposed is the "System for determining the fluctuations of the water surface" (RF patent No. 2,319.984, G01V 1/38, 2006), which is selected as a prototype.

The known system contains microbarographs spaced at fixed distances along the coastline

Microbarographs are connected via a comparison circuit to a warning system. The system is also equipped with a memory unit, a control point and two correlators.

However, the control point of the known system does not allow suppressing narrowband interference and does not increase the noise immunity of the reliability of the reception of complex signals with phase shift keying.

An object of the invention is to increase the noise immunity and reliability of the reception of complex signals with phase shift keying by attenuation of narrowband interference.

The problem is solved in that a system for determining fluctuations in the water surface, containing, in accordance with the closest analogue, microbarographs located in the form of a branched system along the coastline and connected through a comparison circuit to a warning system, a memory unit, a control point and two correlators, each of which consists of a multiplier connected in series to one of the extreme microbarographs, the second input of which is connected via an adjustable delay line to the output of the other extreme microbaro alarm, low-pass filter, extreme 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 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, shaper 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 a transmitting antenna, connected in series to the output of the second correlator of the second analog-code converter and a 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 recording and analysis unit and connected in series a receiving antenna, a 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 multiplier, the second input of which is connected n with the output of the first low-pass filter, the first narrow-band filter, the second multiplier, the second input of which is connected to the output of the intermediate-frequency amplifier, and the first low-pass filter, the second input of the comparison circuit is connected to the output of the memory unit, the microbarographs are spaced at a fixed distance d, two pairs extreme microbarographs spaced a fixed distance nd, where n is the number of microbarographs, differs from the closest analogue in that the control point is equipped with a third and fourth multiplier, the second a band-pass filter, a second low-pass filter, a first and second phase inverters and a subtraction unit, and a third multiplier is connected in series to the output of the intermediate-frequency amplifier, the second input of which is connected to the output of the second phase inverter, the second narrow-band filter, the first phase inverter, the fourth multiplier, the second input which is connected to the output of the intermediate frequency amplifier, a second low-pass filter and a second bass reflex, the output of the first and second low-pass filters through the subtraction unit They are connected to the input of the registration and analysis unit.

The structural diagram of the system for determining the fluctuations of the water surface is presented in figure 1. The structural diagram of the control point is presented in figure 2. Timing diagrams explaining the operation of the system are shown in Fig.3. 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 serial multiplier 1.1 (1.n-1), a multiplier 5.1 (6.1), the second input of which is connected via an 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 ulyatora 5.3 (6.3) and an adjustable delay line 5.4 (6.4), whose second output is the output of the 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 manipulator 3.7, the second input of which is connected to the output of the master power generator 3.8 and transmitting antenna 3.9, connected in series to the output of the second correlator 6 of the second analog-to-code converter 3.2 and the second Lyucha 3.4, the second input of which is connected to the output of comparison circuit 2, and an output connected to the second input of the modulating code 3.5.

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 second input of the mixer 7 is connected to the output of the local oscillator 7.3, the intermediate frequency amplifier 7.5, the first multiplier 7.6, the second input of which is connected to the output of the first low-pass filter 7.9, the first narrow-band filter 7.8, the second multiplier 7.7, the second input of which is connected yield 7.5 intermediate frequency amplifier, the first filter 7.9 lowpass subtraction unit 7.17 and 7.10 unit registration and analysis. To the output of the intermediate frequency amplifier 7.5, a third multiplier 7.11 is connected in series, the second input of which is connected to the output of the second phase meter 7.16, the second narrow-band filter 7.13, the first phase inverter 7.15, the fourth multiplier 7.12, the second input of which is connected to the output of the intermediate frequency amplifier 7.5, the second lower filter 7.14 frequencies and second bass reflex 7.16. The second input of the subtraction unit 7.17 is connected to the output of the second low-pass filter 7.14. The proposed system works as follows.

The principle of determining the fluctuations of the water surface is as follows. The tsunami wave period is in the range from 2 to 200 minutes, the wavelength is from several tens to 300-400 km, with 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 record their propagation practically impossible. However, at the time of tsunami generation, the region 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 center 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 of 1 >> R

where V ₀ - the rate of rise 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 wave change vector, respectively;

J ₁ is the first order Bessel function.

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, α = π / 2, πR ² ≈500 km ² , we obtain for a change in pressure ≈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 specified pressure with the frequencies of the natural oscillations of the tsunami source.

The speed 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 and 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 ₁ (τ) [R ₂ (τ)] obtained at the output of correlator 5 (6) has a maximum for the value of the introduced adjustable delay

τ ₁ = t ₁ -t ₂ ; τ ₂ = t ₃ -t ₄ ,

where t ₁ and t ₂ - the time of the sound signal passing the distance 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 ₁ (τ) and R ₂ (τ) are supported with the help of extreme regulators 5.3 and 6.3, which act on the control inputs of blocks 5.4 and 6.4 of adjustable delays, respectively. The scales of blocks 5.4 and 6.4 of adjustable delays are graded directly in the values of the angular coordinates of the EC tsunami epicenter

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 correlators 5 and 6 are maximum when the planes in which the microbarographs 1.1 and 1.2, 1.n-1 and l.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 converters 3.1 and 3.2 analog - code through the public keys 3.3 and 3.4 respectively are fed to the inputs of the shaper 3.5 modulating code, where the modulating code M (t) is generated (figure 3), which is received the first input of the phase manipulator 3.7, at the second input of which a high-frequency oscillation is supplied from the output of the master oscillator 3.6 (Fig. 3, b)

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

where U _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. 3, c)

u ₁ (t) = U _c cos [ω _c t + φ _k (t) + φ _c ], 0≤t≤T _c ,

where φ _k (t) = {0, π} is the manipulated component of the phase that displays the law of phase manipulation in accordance with the modulating code M (t) (Fig. 3, a), and φ _k (t) = const for kτ _e < t <(k + 1) τ _e and can change abruptly at t = kτ _e , i.e. at the boundaries between elementary premises k = 1, 2, ..., N-1);

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

which after amplification in the amplifier 3.8. power enters the transmitting antenna 3.9, is radiated by it, is captured by the receiving antenna 7.1 of point 7 of the control, and through the high-frequency amplifier 7.2 it enters 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 _g (t) = U _g cos (ω _g t + φ _g ).

At the output of the mixer 7.4, voltages of combination frequencies are generated. The amplifier 7.5 allocated voltage of the intermediate frequency (Fig.3, g)

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

Where

ω _CR = ω _with -ω _g is the intermediate frequency;

φ _CR = φ _s -φ _g ,

which goes to the first inputs of the multipliers 7.6, 7.7, 7.11 and 7.12. The second inputs of the multipliers 7.7 and 7.12 from the outputs of the narrow-band filter 7.8 and the bass reflex 7.15 are supplied with reference voltages, respectively (Fig. 3, d, g):

u ₀₁ (t) = U _o cos (ω _pr t + φ _pr ),

₀₂ u _{(t) = - U o cos} (ω t + φ _{pr pr),} 0≤t≤T _c,

At the output of multipliers 7.7 and 7.12, the total voltages are formed, respectively:

u _∑1 (t) = U _∑ · cosφ _{k (t)} + U _∑ · cos [2ω _pr t + φ _k (t) + 2φ _pr ],

u _∑2 (t) = U _∑ · cosφ _{k (t)} -U _∑ · cos [2ω _pr t + φ _k (t) + 2φ _pr ],

0≤t≤T _c ,

Where

Filters 7.9 and 7.14 highlight low-frequency voltage, respectively (Fig.3, e, s):

u _н1 (t) = U _∑ cosφ _k (t),

u _{H1 (t) = U Σ · cosφ} k (t), 0≤t≤T c,

proportional to the modulating code M (t) (Fig. 3, a). The indicated low-frequency voltages are applied to the two inputs of the subtraction block 7.17. Subtracting one of the other specified low-frequency voltages taking into account their opposite polarity, the output of the subtraction block 7.17 produces a doubled (total) low-frequency voltage (figure 3, and)

u _n (t) = U _н1 (t) -U _н2 (t) = U _н cosφ _k (t),

where U _n = 2U _∑

those. it turns out the addition in absolute value of the stresses u _н1 (t) and u _н2 (t). In this case, the additive amplitude noise passes through two demodulators in the same way, changing the amplitudes of the output detected voltages in the same direction. But in block 7.17 of subtraction, they are subtracted, remaining unipolar, i.e. suppressed, mutually compensated.

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

The low-frequency voltage u _n2 (t) (Fig. 3, h) from the output of the low-pass filter 7.14 is fed to the input of the bass reflex 7.16, at the output of which a low-frequency voltage is generated (Fig. 3, k)

u _{H3 (t) = U Σ · cosφ} k (t), 0≤t≤T c.

Low-frequency voltages u _н1 (t) and u _н3 (t) from the output of the low-pass filter 7.9 and the bass reflex 7.16 are fed to the second input of the multipliers 7.6 and 7.11, respectively, at the output of which harmonic voltages are formed:

u ₀₁ (t) = U ₁ cos (ω _pr t + φ _pr ) + U ₁ cos [ω _pr t + 2φ _k (t) + φ _pr ] = U ₀ · cos (ω _pr t + φ _pr ),

u ₀₃ (t) = U ₁ · cos (ω _pr t + φ _pr ) + U ₁ · cos [ω _pr t + 2φ _k (t) + φ _pr ] = U ₀ cos (ω _pr t + φ _pr ) ,

Where

U _o = 2U ₁ .

These voltages are distinguished by narrow-band filters 7.8 and 7.13, respectively. The voltage u ₀₁ (t) (Fig. 3, d) from the output of the narrow-band filter 7.8 is supplied to the second input of the multiplier 7.7. The voltage u ₀₃ (1) is allocated by a narrow-band filter 7.13 and is fed to the input of the bass reflex 7.15, at the output of which a voltage is generated (Fig.3zh)

u ₀₂ (t) = - U ₀ · cos (ω _pr t + φ _pr ),

which is fed to the second input of the multiplier 7.12.

Multipliers 7.6 and 7.7 (7.11 and 7.12), a narrow-band filter 7.8 (7.13) and a filter 7.9 (7.14) form universal demodulators of PSK signals. Moreover, the reference voltage necessary for the synchronous detection of PSK signals is extracted directly from the received PSK signal.

Known devices that provide the selection of the reference voltage directly from the received PSK signal, for example, Pistolkors A.A., Siforov V.I., Kostas D.F. and Travina S.A. (Radio receivers. Under the editorship of A.G. Zyuko. - M .: ed. Svyaz, 1975, S.354-356, Fig. 14. 19-14.20).

However, the phenomenon of "reverse operation" is inherent in these devices, which reduces the noise immunity and reliability of the synchronous detection of complex PSK signals.

The proposed universal demodulators of complex QPSK signals are free from the phenomenon of “reverse operation”.

Narrowband interference is attenuated by the two universal demodulators mentioned above. Due to the phase inverters 7.15 and 7.16, the output voltages of the demodulators are of mutually opposite polarity. As a result of this, the mutually inverse output voltages of the demodulators are added in absolute value, and the unipolar interference voltages are mutually subtracted.

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 about 1000 km from the epicenter, the tsunami wave travels for about 100 minutes, seismic disturbance ~ 5 minutes, sound disturbance through the submarine cable ~ 10 minutes and the atmospheric channel ~ 50 minutes, which is enough to ensure safety measures for manpower and equipment .

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

To transmit alarm information to the control point, complex signals with phase shift keying are used. 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.

Thus, the proposed system in comparison with the prototype and other technical solutions for a similar purpose provides increased noise immunity and reliability of the reception of complex signals with phase shift keying at the control point. This is achieved by attenuating narrow-band interference and increasing the signal-to-noise ratio at the output of the subtraction unit using two universal demodulators, the inverse output voltages of which are added in absolute value, and unipolar interference voltages are mutually subtracted.

Claims (1)

A system for determining fluctuations in the water surface, containing microbarographs located in the form of a branched system along the coastline and connected through a comparison circuit to a warning system, a memory unit, a monitoring station and two correlators, each of which consists of a multiplier connected in series to one of multiple microbarographs, the second input of which, through an adjustable delay line, is connected to the output of another extreme microbarograph, a low-pass filter, an extreme regulator, and an adjustable line and delays, the second output of which is the output of the correlator, the warning system is made in the form of a first key, connected in series to the output of the comparison circuit, the second input of which is connected through the first converter to the analog-code to the output of the first correlator, the generator of the modulating code, the third input of which is connected to the output a comparison circuit, a phase manipulator, the second input of which is connected to the output of the master oscillator, power amplifier and transmitting antenna, connected in series to the output of the second the second converter of the analog code 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 shaper of the modulation code, the control point is made in the form of a recording and analysis unit and 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 first low-pass filter, the first narrow-band filter, the second multiplier, the second input of which is connected to the output of the intermediate frequency amplifier and the first low-pass filter, the second input of the comparison circuit is connected to the output of the memory unit, the microbarographs are spaced a fixed distance d, the two pairs of extreme microbarographs are spaced a fixed distance nd, where n is the number of microbarographs characterized in that the control point is equipped with a third and fourth multipliers, a second narrow-band filter, a second low-pass filter, a first and second phase inverters and a unit in reading, and to the output of the intermediate frequency amplifier, a third multiplier is connected in series, the second input of which is connected to the output of the second phase inverter, the second narrow-band filter, the first phase inverter, the fourth multiplier, the second input of which is connected to the output of the intermediate frequency amplifier, the second low-pass filter and the second phase inverter, the outputs of the first and second low-pass filters through the subtraction unit are connected to the input of the registration and analysis unit.

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