Method for converting ultrasound wave and apparatus for performing the same

FIELD: acoustics-electronics, ultrasonic technique.

SUBSTANCE: in controlled sound conduit 1 having length Ls and made of non-polarized ferroelectric ceramics with abnormally high dielectric permeability, ultrasonic wave with frequency ω₀ is passed. Said wave is formed by converter 4 and it interacts with electric field rotating around propagation direction of wave and generated as result of action of AC voltage supplied by means of generator 6 and phase splitter 7 upon pairs of electrodes 2, 3 arranged in sound conduit 1. Rotation frequency of electric field coincides with frequency of ultrasonic wave Ω = ω₀. According to invention it is realized resonance interaction of circular component of ultrasonic wave (whose frequency and rotation sign coincide with frequency and rotation sign of electric field having intensity more than threshold value) with such electric field. In the result ultrasound absorption is prevented and in outlet of sound conduit elliptically polarized ultrasonic wave is created with intensity more than that of said wave.

EFFECT: possibility for increasing intensity of ultrasonic wave passing through sound conduit.

2 cl, 3 dwg

The invention relates to acoustoelectronic and ultrasonic technique and can be used to create the managed devices in acoustoelectronics, namely to enhance the ultrasonic waves.

The known method and device for amplification of ultrasound in semiconductors drift of charge carriers, made in the form of the transducer shear waves placed on the entrance end face of the managed Zvukovaya connected to the active crystal having good piezoelectric properties and photoconductivity, the end face of which is coated with metal electrodes, and exposed to light [1]. Passing through the crystal ultrasonic wave is amplified, if the drift velocity of charge carriers in the direction of propagation of the wave exceeds the phase velocity.

The dynamic range of the amplifier is limited by the level of noise and nonlinear effects. To create the optimum conductivity required selection intensity and spectral composition of light from the illuminator. To prevent the destruction of the crystal due to overheating constant current pulse is applied to the operation of the amplifier. However, the pulsed mode of operation, it is necessary to select lighting limit the possible applications of amplifiers.

The closest invention technical sown the STI to claimed is a method of converting ultrasonic waves, is the impact of the rotating electric field transverse to the direction of propagation of the ultrasonic waves, the unpolarized magnetoterapia with an abnormally high value of the dielectric constant in the propagation in the acoustic wave [2].

The frequency of the ultrasonic wave and the frequency of rotation of the electric field must not equal.

The technical essence of this method is that if the ultrasonic wave is propagated in the unpolarized magnetoterapia with an abnormally high value of the dielectric constant and exposed to an electric field rotating transversely to the direction of propagation of the ultrasonic waves, depending on the ratio of the natural frequency of the ultrasonic waves, the parameters magnetoterapia, speed and intensity of the electric field of the wave changes its parameters. Taking into account these dependencies, you can control the parameters of ultrasonic waves.

In the known method, subject to the condition that the frequency of the linearly-polarized ultrasonic waves and the frequency of rotation of the electric field must not equal, converting the ultrasonic wave is to change the angle of the plane of its polarization.

However, the known method of converting ultrazvukovoy wave does not fully take into account the interrelation between the parameters and their influence on other characteristics of the ultrasonic wave.

Closest to the claimed is a device for converting ultrasonic waves containing made of non-polarized magnetoterapia with an abnormally high value of dielectric permittivity managed vukobrat, on which are placed opposite to each other are electrically insulated pair of electrodes and the transducer shear wave phase shifter, a generator of alternating voltage of ultrasonic frequency, the output of which is connected to the input of the above-mentioned phase shifter and one pair of electrodes, and the output of the phase shifter is connected with another pair of electrodes [2].

This known device has necessarily two pairs of flat electrodes and the phase shifter with a phase shift [2].

The known device provides rotation of the polarization plane of the ultrasonic waves. The amount of rotation of the plane of polarization is proportional to the length of Zvukovaya, which is chosen at random.

In the known device is not taken into account the influence of the length of Zvukovaya to ensure the best conditions of interference of their own modes of the acoustic field.

The technical problem solved by the claimed invention, is to expand the technological capabilities of the method and device and providing amplification of ultrasonic waves.

The technical result achieved is th at the same time, is expressed in the possibility of increasing the intensity transmitted through sumprod ultrasonic wave relative to the incident wave intensity.

According to the invention offers a method and a device for converting ultrasonic waves, namely to strengthen it.

The achievement of the technical result is ensured by the fact that in the method of converting the ultrasonic waves, is the impact of the rotating electric field transverse to the direction of propagation of the ultrasonic waves, the unpolarized magnetoterapia with an abnormally high value of the dielectric constant in the propagation in the acoustic wave, the frequency of rotation of the electric field set in accordance with the equality

and the electric field strength must exceed the threshold value

when this threshold value of electric field intensity set in accordance with the expression

where

E_then- the threshold value of intensity of the rotating electric field;

Ω - frequency of rotation of the electric field;

ω₀- frequency ultrasonic waves;

η₄₄- component tensor viscosity;

α₁₄₄155- the components of the tensor, taking into account electrostrictive the influence of an electric field on the elastic constants of the environment;

β₁₄₄that β₁₅₅- tensor components, taking into account electrostrictive the influence of an electric field on the viscosity of the medium.

The inventive method is implemented using a device for converting ultrasonic waves.

The achievement of the technical result is achieved in that the device for converting ultrasonology wave having managed sumprod made of non-polarized magnetoterapia with an abnormally high value of the dielectric constant, which are placed opposite to each other are electrically insulated pair of electrodes and the transducer shear wave phase shifter, a generator of alternating voltage of ultrasonic frequency, the output of which is connected to the input of the phase shifter and one pair of electrodes, and the output of the phase shifter connected to other pairs of electrodes, managed sumprod has a length corresponding to the calculation formula

where

L_s- the length of a managed Zvukovaya;

ζ₁and ζ₂- the arguments of the complex ellipticity;

the parameter s takes values from the set of integers;

k₁and k 2- the wave number of private modes of the acoustic field;

ω₀- frequency ultrasonic waves;

Ω - frequency of rotation of an electric field.

The basis of the proposed method is based on a phenomenon of suppression of absorption of ultrasonic waves. The essence of the phenomenon that due to the interference of the incident acoustic wave and converts the acoustic wave generated in magnetoterapia rotating electric field, formed a standing ultrasonic wave, to which the viscous properties of the environment manifest themselves very poorly. Because of this suppression of absorption of ultrasound is a giant amplification of the past and facing the acoustic waves as a result of highly efficient energy transfer rotating electric field of ultrasound.

Consider the propagation of ultrasonic waves along the Z-axis in the electric field with amplitude E and components

rotating with a frequency of Q around the axis Z. Such a field can be created by feeding the electric potential with a phase shift to the system of parallel metal electrodes placed on the surface of magnetoterapia. When this phase shift is determined by the number of electrodes and for the case of two pairs of electrodes is π/2. The acoustic properties of magnetoterapia can be described with what omashu generalized law of Hooke [3], taking into account the viscosity of the medium

Here σ_ikthat γ_lmand c_iklm- tensors of stress, strain and elastic constants; η_iklm- the tensor viscosity. The influence of rotating electric field (5) may lead to substantial changes in the acoustic properties of the crystal, resulting in the propagation of elastic waves with displacement vector u is described by the equation of motion

Here ρ the density of the medium, the tensors of elastic constants Λ(t) and viscosity B(t) take into account the non-stationary effect of an external electric field (5) and have the following form:

In expressions (8) designations used [4, 5]:

α and β - tensors, taking into account electrostriction impact of the field E on the elastic constants and viscosity of the medium:

the rotation matrix around the z axis by the angle ϕ= Ωt [6], tilde (˜) means transpose, c^xis an antisymmetric tensor of the dual vector C.

Using the methodology proposed in [7, 8], solutions of the equations of motion (5) we seek in the form of interconnected flat monochromatic waves

having the same wave number k(ω), RA is personal frequency ω ± Ω and the opposite circular polarization defined by the vectorswhere a and b - Horta laboratory Cartesian coordinate system.

Elastic waves in a crystal with a rotating structure (10) depend essentially on the values ωdetermined by the frequency and polarization of the incident acoustic wave. Consider the case when the boundary of the crystal at z=0 is excited by a circularly polarized ultrasonic wave

the vector of elastic displacement which has the same direction of rotation over time, as the external electric field. Due to the continuity of the vector of elastic displacement on the boundary of the crystal of the incident wave excites the crystal in the first wave with the same polarization and frequency described in the second summand in (10). Therefore,

ω₀=ω+ Ω,

and a private acoustic fashion crystal (10) can be written in the form

Consider the case

ω₀= Ω,

when the incident wave coincides with the external electric field not only in the direction of rotation and frequency. Then

i.e. own fashion crystal consists of two interconnected circular polarized waves, rasprostranyalis is in opposite directions and having the same frequency. Since the polarization is determined depending on the direction of wave propagation, circular proprietary wave crystal have essentially the same polarization.

Substituting the expression (10) in equation (7) and taking into account the explicit form of the tensor (8), we obtain the following system of linear homogeneous equations:

Equating to zero the determinant of the system (11), we find the wave number

k_3,4(ω)=-k_2,1(ω)

and the relationship of the amplitudes of the circular component

own mod (10) of the acoustic field.

In expressions (15), (16) the following notation is used:

Values ξ_kcharacterize the coupling coefficient between the circular waves that make up its own fashion the acoustic field. Further, for brevity we will call the values ξ_kellipticheskimi own acoustic modes. The rationale for using such a term is the fact that the values ξ_kreally equal to ellipticity own waves of the acoustic field, if we consider these waves in a rotating coordinate system.

Will move in a rotating coordinate system, accompanying the rotation of the external electric the field (5) and insert converted to this system, the expression (10) in equation (7), given that in a rotating coordinate system, in contrast to the laboratory, the tensors of elastic constants and viscosity (8) do not depend on time, allowing you to search for solutions of the equations of motion in the form of a plane monochromatic waves

frequency ω' and the wave number k(ω'). In the laboratory coordinate system, the displacement vector of the wave (17) has the form analogous to (10);

Consider the case when the boundary of the crystal at z=0 is excited by a circularly polarized acoustic wave (11), the vector of elastic displacement which has the same direction of rotation in time, as the external electric field. From the condition of continuity of the vector u on the boundary should ω₀=ω'+ Ω, ie ω'=ω₀- Ω. If the frequency ultrasound ω₀coincides with the frequency of the electric field Ω (case of resonant interaction), then the ratio of ω'=0, and own mods (17) of the acoustic field have the form of standing waves.

Equating to zero the determinant of the resulting system, we find expressions for the wave numbers own mod acoustic fields:

Rotating electric field can lead to significant changes in the acoustic properties of a crystal with abnormally high dialect the practical permeability. As follows from expression (18), with increasing anisotropy of the tensor of elastic constants δ and anisotropy tensor viscosity χinduced by an electric field, the imaginary parts of the wave numbers monotonically decrease to zero. Since the threshold parameter values δ and χdetermined by the condition

wave number (18) become valid, and own fashion acoustic fields cease to fade in the crystal. In accordance with condition (19) the threshold value of intensity of the rotating electric field is expressed through the parameters of the crystal as follows:

If the frequency ultrasound ω different from the frequency of the electric field Ωthen wave number (18) are integrated regardless of the strength of the electric field. As shown by numerical evaluation, with the following values of parameters characteristic of the ceramics based on barium titanate with an abnormally high dielectric constant [9-11]:

=10¹²Dyne/cm²that δ=-4,465·10¹⁰Dyne/cm²,=1000 GHS,

χ=50 GHS, ρ=5.7 g/cm³that Ω=10⁷rad/s,

performing threshold condition (17) is achieved when the electric field intensity of the order of several cvsm.

The solution of the boundary value problem allows to determine the value of the normalized intensity of the previous waves

where

the amplitude of the previous wave,

u₀the amplitude of the incident wave (11)

The expression for the normalized intensity of the previous ultrasonic waves (21) allows us to evaluate the possibility of gain.

According to the proposed method the ultrasonic wave in the form of a beam injected into the unpolarized magnetoterapia with an abnormally high value of the dielectric constant. Magnetoterapia when it is exposed to a rotating electric field transverse to the direction of propagation of the ultrasonic waves, in other words, the intensity vector field is directed normal to the wave vector of the ultrasonic waves. Tension E₀rotating electric field set in accordance with the calculation formula (2).

Speed Ω a rotating electric field set equal to the frequency of the ultrasonic wave ω₀in accordance with the calculation formula (1).

In this case, the wave number (18) become valid, own fashion acoustic fields cease to fade in the crystal and the intensity passed through sucopro the d ultrasonic waves is increased relative to the intensity of the incident wave as a result of highly efficient energy transfer rotating electric field of ultrasound.

Examples of the method are given in table 1.

As follows from table 1, the amplification of ultrasonic waves may be the case if the electric field E₀exceeds the threshold value and the frequency of ultrasonic waves ω₀coincides with the frequency of rotation of the electric field Ω.

Thus, in the inventive method potentially have a wider dynamic range what zones and more control parameters of ultrasonic waves.

The device for implementing the method provides the ability to perform operations of the method and select the desired settings. Execution of the managed Zvukovaya with length L_scorresponding calculation formula (4), provides the best conditions for the interference of their own modes of the acoustic field and allows you to maximize the last wave relative to the incident.

Figure 1 shows acoustoelectric device node (side view), figure 2 - acoustoelectric unit (front view)figure 3 - electrical diagram of the device.

Device for amplifying ultrasonic wave contains (see figure 1 and 2) managed sumprod 1, having a length L_sand made of non-polarized magnetoterapia with an abnormally high value of the dielectric constant, which can be made in the form of a rectangular parallelepiped, on the opposite faces of which are parallel to the axis of Zvukovaya, installed opposite to each other of the pair of electrodes 2, 3, respectively forming first and second pairs. The number of pairs of electrodes determines the phase shift and for the case of two pairs of electrodes is π/2. The end faces perpendicular to the axis of Zvukovaya posted Converter 4 shear waves. Managed sumprod 1 hosted pairs of electrodes 2, 3 and transducer 4 with the order acoustoelectric node 5. The first pair of electrodes 2 are connected through a first input acoustoelectric node 5 to the generator output 6 AC electric voltage of ultrasonic frequency, and the second pair of electrodes 3 are connected through a second input of the acoustoelectric node 5 to the output of the phase shifter 7.

The connection of the pairs of electrodes 2, 3 with generator 6 AC electric voltage of ultrasonic frequency and the phase shifter 7 is performed by means of coaxial cables, with the center conductor of each cable is connected to one electrode of the pair, and escape from the second. Specified mutual arrangement of the pairs of electrodes 2, 3 on sucoplate 1 and connected to the phase shifter 7 and the generator 6 AC electric voltage of ultrasonic frequency provide when the device is a constant amplitude and a constant phase shift of the electric voltages applied to the pair of electrodes 2, 3. The output of generator 6 AC electric voltage of ultrasonic frequency connected to the input of the phase shifter 7 first input of the acoustoelectric node 5, and the output of the phase shifter 7 is connected to a second input of acoustoelectric node 5 (see figure 3).

To prepare the device for operation pre-made sumprod 1, while depending on the frequency of ultrasonic waves ω₀its length L must be equal to the value calculated by the formula (4).

The device operates as follows.

Converter 4 excites shear linearly polarized with a certain orientation of the ultrasonic wave with a frequency of ω₀and sends them in the form of a beam in a controlled sumprod 1 parallel to its axis. Using generator 6 AC electric voltage and the phase shifter 7 is served on the pair of electrodes 2, 3 AC voltage, and the voltage applied to the first pair of electrodes 2, differs in phase by π/2 of the voltage applied to the second pair of electrodes 3 from the phase shifter 7. In the result of the superposition of a uniform perpendicular electric fields, time varying according to the harmonic law with a relative phase shift π/2, inside Zvukovaya 1 occurs rotating around the axis of Zvukovaya 4 electric field intensity vector which rotates with time around the axis of Zvukovaya 1 frequency Ω. Frequency Ω pre-installed on the generator 6 AC electric voltage as the amplitude of the AC electric voltage. Rotating electric field due to the effect of electrostriction affects the acoustic properties of unpolarized sign is toceramic.

Linearly-polarized wave can be represented as a sum of two circularly polarized with the same displacement amplitude and opposite direction of rotation. The circular component of the ultrasonic wave, which coincides with the rotating electric field in the direction of rotation and frequency experiences a resonance effect of the rotating electric field. Resonant interaction of ultrasonic waves with a rotating electric field for waves with opposite circular polarization does not occur in any frequency. In the ultrasonic wave at the exit from the zone of action of a rotating electric field, i.e. on the output face of the managed Zvukovaya 1, is elliptically polarized. In the resonant interaction of the circular component of the ultrasonic wave, the frequency ω₀and the direction of rotation which coincides with the frequency Ω and the direction of rotation of the electric field E₀, the intensity of which exceeds the threshold of E_thenappears an effect of suppressing the absorption of ultrasound, allowing the output from Zvukovaya is formed elliptically polarized ultrasonic wave, the intensity of which is higher than the intensity of the incident wave.

The influence of length L_ssound is the wires on the intensity of the previous wave T are presented in table 2.

This giant enhancement of ultrasound is a consequence of the suppression of the absorption of acoustic waves in a rotating electric field and the interference of their own modes of the acoustic field.

Gain control can also be achieved by the frequency deviation of the rotating electric field Ω frequency waves ω₀( Ω≠ω₀).

The examples presented in table 3.

Thus, the inventive method and device for converting ultrasonic waves have three degrees of control: gain control may vary due to joint changes the frequency of the incident wave ω₀and frequency rotating electric field Ω ( Ω=ω₀), due to the deviation of frequency rotating electric field Ω frequency waves ω₀( Ω≠ω₀), by changing the length of Zvukovaya L.

Sources of information

1. Ultrasound / CH. edit Iphoneman. Moscow: Soviet encyclopedia, 1979. S-360.

2. RF patent №2123895, publ. 1998 (prototype).

3. V.L. Gurevich Kinetics of phonon systems. Moscow, 1980. 400 S.

4. White V.N., Sevruk B.B. Control of polarization of elastic waves by an electric field, creating a helical anisotropy // Akust. Journe. 1983. T, No. 2. S-161.

5. White V.N., Sevruk B.B. PA is americasee interaction of circularly polarized electromagnetic and acoustic waves in crystals with electrostrictive nonlinearity // Coll.: Covariant methods in theoretical physics. Minsk, 1986. P.132-141.

6. Fedorov FI Theory gyrotropy. Minsk: Science and technology, 1976. 456 C.

7. I.V. Semchenko, A.N. Serdyukov. The light propagation in a medium with a rotating cholesteric structure anisotropy // Journal of applied spectroscopy, 1984. V.41, №5. S-830.

8. White V.N., Sevruk B.B. Parametric electro-acoustic effects in crystals with induced external electric field, rotating acoustic anisotropy // Journal of technical physics, 1987. T, No. 2. S-340.

9. Pekar, S., A.A. Demidenko, Zdebski A.P. and others Research electrostriction constants of the first and second order in materials with large dielectric constant. / / Dokl. THE USSR ACADEMY OF SCIENCES. Ser. Phys. 1976. T, No. 5. S-1091.

10. Habitance NICHOLAS, Kucherov IA the Study of the influence of electric field on the propagation velocity of elastic waves in isotropic solids // Ukr. physics, Ukr., 1978. Volume 23, No. 2. S-266.

11. The influence of a constant electric field on the propagation of surface acoustic waves in piezoelectric ceramics system CTS / edited Antibanner, Avery, Nevzorova, Essional // Journal of technical physics. 1986. T, No. 12. S-2375.

1. The method of conversion of the ultrasonic waves, is the impact of the rotating electric field transverse to the direction of propagation of the ultrasonic waves, d is Ignatchenko with an abnormally high value of the dielectric constant in the propagation in the acoustic wave, characterized in that the speed and tension of the rotating electric field set in accordance with the equality

and the electric field strength must exceed the threshold value

E₀>E_then,

thus

where

Ω - frequency of rotation of the electric field;

ω₀- frequency ultrasonic waves;

E_then- the threshold value of intensity of the rotating electric field;

η₄₄- component tensor viscosity;

α₁₄₄that α₁₅₅- the components of the tensor, taking into account electrostriction impact of the field E on the elastic constants of the environment;

β₁₄₄that β₁₅₅- tensor components, taking into account electrostrictive the magnetic field on the viscosity of the medium.

2. A device for converting ultrasonic waves containing managed sumprod made of non-polarized magnetoterapia with an abnormally high value of the dielectric constant, which are placed opposite each other are electrically insulated pair of electrodes and the transducer shear wave phase shifter, a generator of alternating voltage ultrasonic hour is the notes, the output of which is connected to the input of the phase shifter and one pair of electrodes, and the output of the phase shifter connected to other pairs of electrodes, characterized in that the managed sumprod has a length corresponding to the calculation formula

L_s=(ζ₁-ζ₂+2πs)/[k₁(ω₀- Ω)-k₂(ω₀- Ω)],

where L_s- the length of a managed Zvukovaya;

ζ₁and ζ₂- the arguments of the complex ellipticity;

the parameter s takes values from the set of integers;

k₁and k₂- the wave number of private modes of the acoustic field;

ω₀- frequency ultrasonic waves;

Ω - frequency of rotation of an electric field.