RU2291453C1 - Method and device for reduction of effective surface of dissipation of aerials - Google Patents

Abstract

FIELD: aerial technique.

SUBSTANCE: first controlled cellular structure made in form of screen or fairing, which is mounted in front of aerial, reflector of aerial, has parts of second controlled cellular structure, which parts are placed conformal with surface of reflector. Sizes of parts are equal or bigger than 5λx5λ. The parts change phase of reflected signal in such a way that parabolic law of change in reflector's reflection factor is not violated. Methods of manufacture of first and second cellular structures is described as well as mathematic formulas for determination of different parameters of cellular structures are given. Level of side lobes of aerial is reduced within wide frequency range which results to significant reduction of effective surface of dissipation of aerial not only during non-working period of time but during working ones as well while level of reduction of efficient surface of dissipation of aerial is kept constant within borders of its main lobe.

EFFECT: improved efficiency.

2 cl, 5 dwg

Description

The invention relates to antenna technology and radar and can be used to reduce the radar visibility of antennas by reducing their effective scattering surface (EPR).

A known method of reducing the EPR of aperture antennas (Mikhailov GD, Sergeev VI, Solomin EA, Voronov VA Methods and means of reducing the radar visibility of antenna systems. Foreign radio electronics, 1994, No. 4-5, s .54-59), consisting in the fact that in front of the antenna, a screen is installed in the form of a metal surface in the form of a cone with slotted slots. This screen transmits a wave with a frequency and polarization of its own radar and reflects like metal waves of other frequencies and polarizations. The disadvantage of the method and device for its implementation is that the EPR is reduced only at other polarizations and frequencies other than the polarization and frequency of the own radar. Despite the authors' assertion that the total ESR can be reduced by 30 dB, it is obvious that even with 100% scattering of the orthogonal polarization signal in the operating frequency band of the own radar, the ESR of the antenna can be reduced by a maximum of 3 dB.

A known method of reducing the EPR of aperture antennas (ibid.), Which consists in the fact that under the cowl antenna create a plasma screen in shape coinciding with the cowl. When the electron concentration inside the fairing is above a certain critical frequency band, the EPR of the antenna can be significantly reduced. The disadvantage of this method is that in the working frequency band of its own radar EPR antenna is not reduced. The disadvantage of the device implementing this method is the high power consumption.

The closest in technical essence and the achieved result (prototype) is a method of reducing the EPR of antenna systems (ibid.), Consisting in the design of a fairing or screen located in front of the antenna in the form of a controlled layered medium containing randomly alternating uncontrolled and controlled layers, as well as a conductive screen. Uncontrollable layers are layers of homogeneous dielectrics or two-dimensionally periodic lattices of conductive elements (strips or rods). Controlled layers are two-dimensionally periodic lattices of conductive elements (strips or rods), in the breaks of which are included controlled elements - semiconductor diodes, ferro-ceramic capacitors, nonlinear capacitances or nonlinear inductances. The controlled layers can also be made in the form of ultraviolet films, semiconductor films and resistive uncontrolled films. In the latter case, the managed layer is simply some unmanaged load. The principle of operation of controlled layered media that implement this method of EPR antenna systems is that during periods of emission and reception of pulses the layered medium is in the transmission mode of the signal, which is provided at the same level of control action (current or voltage) on the controlled elements. At a different level of control action, the controlled layered medium at a time period that does not coincide with the periods of emission and reception of the pulse switches to the reflection state of the signal. In this case, the reflected signal is also scattered by the EPR of the antenna system in the operating frequency band and decreases approximately Q (duty cycle) times within the main lobe of the radiation pattern.

The disadvantage of this method is that the EPR at separate time intervals is reduced only within the main lobe of the antenna pattern. The width of the main lobe for aperture antennas is fractions or several degrees. Outside this lobe, the EPR of the antenna does not decrease. In addition, at working intervals, the EPR does not decrease fundamentally.

A device for reducing the EPR of antennas is known that implements this method (A. Golovkov. Complex electronic devices. M: Radio and communication, 1996, p. 114-120; Controlled structure to reduce the effective antenna scattering surface. Application for invention No. 3147646 dated July 22, 86. Autos-certificate No. 266523 dated December 1, 87).

; 10^-4λ≤h≤10^-2λ, толщина d₁ диэлектрических слоев и показатель преломления n их материала выбраны равными d₁=0,25λ/n и 1,1≤n≤5,5, где λ - средняя длина волны рабочего диапазона длин волн.This device is made in the form of a controlled structure to reduce the effective antenna scattering surface, which differs from the previous device in that the square controlled grating and metal gratings are aligned in one plane, the real component of the immittance of each semiconductor element is selected negative, the levels of control low-frequency signals are selected from the conditions for providing amplifying or generating operating modes, period "a" of the square controlled grating, width d of its strips and width δ of it discontinuities are selected, respectively, equal to 0.2 / λ≤a≤0.6λ; 0.4a≤d≤0.9a; 0.05a≤δ≤0.9a, the period a _{m of the} metal lattice and the width h of its conductive strips are chosen equal to, respectively, and _m =

; 10 ^-4 λ≤h≤10 ^-2 λ, the thickness d _{1 of the} dielectric layers and the refractive index n of their material are chosen equal to d ₁ = 0.25λ / n and 1.1≤n≤5.5, where λ is the average wavelength operating wavelength range.

The disadvantages of this device repeat the disadvantages of the method that it implements. The main one is that the EPR of the antenna can not be reduced at working intervals and in the angular sector that does not coincide with the main lobe of the radiation pattern.

A device is known that implements this method and is made in the form of a controlled structure for reducing the EPR of an antenna containing a three-layer medium in the form of two identical dielectric layers of material with a refractive index of 1.1≤n≤45.5 and a controlled layer located between them and a control signal generator moreover, the controlled layer is made in the form of a semiconductor film, each dielectric layer is made of optically transparent material with a thickness equal to (0.15 ... 0.5) λ, where λ is the average wavelength of the operating range, at than the dielectric layers and the controlled layer are arranged concentrically, and at the point equidistant from the inner surface of the three-layer medium, an optical range pump lamp is installed that is connected to the control signal generator (A. Golovkov. Complex electronic devices. M .: Radio and communication, 1996, p.114-120; Controlled structure to reduce the effective scattering surface of the antenna. Application for invention No. 3186037 from 08.12.87. Auth. certificate No. 294454 of June 1, 89).

The disadvantages of this device repeat the disadvantages of the method that it implements. The main disadvantage of the prototype, as well as previous analogues, is the inability to reduce the EPR of the antenna at working intervals and in the angular sector that does not coincide with the main lobe of the radiation pattern.

Of the known devices, the closest in technical essence and the achieved result (prototype) is a device for reducing the EPR of antennas that implements the specified method (A. Golovkov. Integrated electronic devices. M: "Radio and communication", 1996, p. 114-120; Device for reducing the effective scattering surface of the antenna. Application for invention No. 3085315 of 03/19/84. Authors certificate No. 213006 of 12/28/84).

This device for reducing the effective antenna scattering surface is made in the form of a flat-layered structure consisting of a first metal square lattice adjacent to each other, a first dielectric layer, a controlled lattice of conductive strips or rods, in the gaps of which are ferroceramic capacitors or pin diodes, a second dielectric layer and the second metal lattice, respectively identical to the first dielectric layer and the first lattice, with one system of parallel strips, ar each lattice is isolated at a low frequency from another system of parallel strips perpendicular to the first, and the system of parallel strips forming the lattice is rotated 45 degrees relative to the strips of the controlled lattice, the intersection points of which are alternately connected by conductors perpendicular to the plane of the layers, with one of the parallel systems strips of the second lattice, connected alternately to different terminals of the control signal generator, connected to the output of the automatic range tracking system , Wherein the thickness of the dielectric layers equal to half the working wavelength of the radar, and the conductivity in the gratings, the inductive reactance X ₀ strips gratings and the capacitive reactance X _w discontinuities controlled lattice are determined from the ratios obtained from the conditions to maximize the reflectance in one of the states of capacitors or diodes, determined by the level of control voltage, and the minimum signal attenuation in another state of the controlled elements.

The disadvantages of this device repeat the disadvantages of the method that it implements. The main disadvantage of the prototype, as well as previous analogues, is the inability to reduce the EPR of the antenna at working intervals and in the angular sector that does not coincide with the main lobe of the radiation pattern.

The technical result of the invention is to reduce the ESR level of the antenna system at working time intervals and in the angle sector that does not coincide with the main lobe of the radiation pattern, while maintaining the level of reduction of the EPR antenna at non-working time intervals and within the main lobe of the radiation pattern.

This result is achieved by the fact that in the method of reducing the EPR of antennas based on the use of the first controlled layered structure in the form of a screen or fairing, the installation of a screen or fairing in front of the antenna, the switching of the first controlled layered structure from the transmission state at the time of emission and reception of pulses to the reflection state at time points that do not coincide with the time points of emission and reception of pulses, antenna reflectors conformally with their surface are additionally randomly arranged with their surface they generate independent sections of the second controlled layered structure, no less than 5λ × 5λ in size, which change the phase of the reflected signal in such a way that the signals reflected from these sections in the direction of the side lobes are not in phase, but a parabolic law is preserved within the main lobe changes in the phase of the reflectivity of the reflector, λ is the wavelength.

This result is achieved in that in the device for reducing the EPR of the antennas, made in the form of a fairing or screen mounted in front of the antenna, and the fairing or screen is made on the basis of the first controlled layered structure, consisting of adjacent to each other the first metal square lattice, the first dielectric layer, controlled two-dimensional periodic lattice of conductive strips or rods, in the breaks of which are included ferroceramic capacitors or pin diodes, the second dielectric layer and the second etallicheskoy lattice, respectively identical to the first dielectric layer and the first grating, and a system of parallel strips. forming each lattice, is isolated at a low frequency from another system of parallel strips perpendicular to the first, and the system of parallel strips forming the lattice is rotated 45 degrees relative to the strips of the controlled lattice, the intersection points of which are alternately connected by conductors perpendicular to the plane of the layers, with one of the parallel systems strips of the second lattice, connected alternately to different terminals of the control signal generator, connected to the output of the automatic tracking system along b, and the thickness of the dielectric layers is equal to half the working wavelength of the radar, and the conductivity B of the gratings, the inductive resistance X _{o of the} strips and the capacitance X _{w of the} gaps of the controlled grating are determined using the relations obtained from the conditions for ensuring the maximum reflection coefficient in one of the states of capacitors or diodes determined by the levels of control voltage and the minimum signal attenuation in a different state of the controlled elements, the antenna reflector conformally with its surface is random m manner arranged independent from each other by portions of the second controllable layered structure with dimensions not less than 5λ × 5λ, each of which is made of successively transferred by the reflector of the first dielectric layer with a thickness d ₁ and index of refraction n _1, controlled layer as a resistive film, a second dielectric layer with a thickness of d ₂ and a refractive index of n ₂ and a two-dimensionally periodic lattice of conductive strips or rods with reactive conductivity B _p , while the thickness of the second dielectric c loya and conductivity of a two-dimensional periodic lattice are selected using the expressions:

where M = AD + (2 + B) (1-C);

n=1, 2..., N; N - число независимых участков второй управляемой слоистой структуры; φ_n - заданные фазы коэффициентов отражения n-ого участка второй управляемой слоистой структуры; g₀, b₀ - действительная и мнимая части проводимости свободного пространства; g_yn, b_yn - действительная и мнимая части проводимости управляемых слоев в виде резистивных пленок n-ого участка второй управляемой слоистой структуры, определяемых толщиной пленки; параметры d₁, n₁, n₂, выбраны произвольно.

n = 1, 2 ..., N; N is the number of independent sections of the second controlled layered structure; φ _n - the specified phase of the reflection coefficients of the n-th section of the second controlled layered structure; g ₀ , b ₀ - real and imaginary parts of the conductivity of free space; g _yn , b _yn are the real and imaginary parts of the conductivity of the controlled layers in the form of resistive films of the nth portion of the second controlled layered structure, determined by the film thickness; parameters d ₁ , n ₁ , n ₂ , are chosen arbitrarily.

Figure 1 shows a device for implementing a method of reducing the EPR of antennas (prototype).

Figure 2 presents the controlled layered structure used in the device for implementing the prototype method.

Figure 3 shows an example of a two-dimensional periodic lattice used in a controlled layered structure that implements the prototype method.

Figure 4 presents the implementation system of the proposed method for reducing the EPR of antennas.

Figure 5 shows the structure of the layered medium located on the antenna reflector.

A device for reducing the effective scattering surface (Fig. 1) of the antenna 1 is made in the form of a plane-layered structure 2, consisting (Fig. 2) of adjacent to each other the first metal square lattice 3, the first dielectric layer 4, the controlled lattice 5 of conductive strips or rods 6 , in the gaps of which are included ferroceramic capacitors or pin diodes 7, of the second dielectric layer 8 and the second metal grating (Fig. 3), identical to the first dielectric layer 4 and the first grating 3, respectively, while one system the parallel strips 3.1 (9.1) forming each lattice are isolated at a low frequency from another system of parallel strips 3.2 (9.2) perpendicular to the first, and the systems of parallel strips forming lattices are rotated 45 degrees relative to the strips of the controlled lattice, the intersection points of which are alternately connected conductors 10, perpendicular to the plane of the layers, from one of the systems parallel to the strip of the second lattice, connected alternately to different terminals of the control signal generator 11, connected to the output of the auto system range 12, and the thickness of the dielectric layers is equal to half the working wavelength of the radar, and the conductivity B of the gratings, the inductance X _{0 of the} strips of the gratings and the capacitance X _{w of} discontinuities of the controlled grating are determined from the relations obtained from the conditions for ensuring the maximum reflection coefficient in one of states of capacitors or diodes, determined by the level of control voltage, and the minimum signal attenuation in another state of the controlled elements.

At the moments of emission and reception of pulses determined by the automatic tracking system in range, the layered medium switches to a state of transparency, and at other moments of time that do not coincide with the moments of emission and reception of pulses, the layered medium switches to a state of reflection. Moreover, during non-working time intervals in the working frequency band and within the main lobe of the radiation pattern, the EPR decreases by about Q times.

The device for implementing the proposed method (Fig. 4) differs from the device for implementing the prototype method (Fig. 1) in that additionally independent sections of a layered medium (Fig. 5) with dimensions of at least 5λ × 5λ, the parameters of which are selected in this way, are randomly arranged on the reflector that the parabolic law of the phase change of the reflectance of the reflector is preserved. Each section (figure 5) contains a conductive screen (reflector surface) 10, an adjacent first dielectric layer 11 with a refractive index n ₁ and a thickness d ₁ , a controlled layer 12 in the form of a resistive film with a given complex conductivity, and a second dielectric layer 13 s refractive index n ₂ and thickness d ₂ and a two-dimensionally periodic lattice 14 of conductive elements. Due to this, the side lobes of the antenna pattern, i.e. its ESR outside the main lobe will be reduced by about 13 dB both in the working time intervals and outside these intervals in a wide frequency band, since the signals reflected from these sections of the layered medium in the direction of the side lobes are not in phase. In this case, the function of reducing the EPR approximately by a factor of Q within the main lobe of the radiation pattern outside the working time intervals and in the working frequency band is preserved, since in the direction of the main lobe the signals reflected from sections of the layered medium are added in phase due to the conservation of the parabolic law of phase change over the reflector surface .

We show the possibility of fulfilling these conditions. We randomly divide the scheme of the nth portion of the layered medium placed on the reflector into the controlled and uncontrolled parts. The managed part includes a managed element (layer) and a part of unmanaged elements (layers). An uncontrolled part or a phase device (FC) includes only uncontrolled elements. Imagine an equivalent circuit of a layered medium in the form of a two-terminal network consisting of a four-terminal network loaded on the conductivity of the controlled part. At the same time, the four-terminal network is the equivalent circuit of the FC.

Let the phase device be directly connected to the signal source. The conductivity of the signal source y ₀ = g ₀ + j · b ₀ and the controlled layer in the form of a resistive film in the states y _yn = g _yn + j · b _yn at a fixed frequency and in the nth state determined by the level of control action are known.

It is required to determine the structure of the FE, the minimum number of layers and the values of their parameters, at which the required values of the reflection coefficient phases would be provided in two states of the controlled layer at a given frequency:

- коэффициент отражения участка слоистой среды; φ_n - значения фаз коэффициентов отражения в n-ом состоянии.Where

- reflection coefficient of the layered medium; φ _n - phase values of reflection coefficients in the n-th state.

Let FU is characterized by a wave transmission matrix:

- нормированные относительно d элементы волновой матрицы ФУ (Фельдштейн А.Л., Явич Л.Р. Синтез четырехполюсников и восьмиполюсников / Связь. М. - 1971, с.30-40). Определим входное сопротивление двухполюсника и используя известное выражение для коэффициента отражения двухполюсника (Сазонов Д.М. Антенны и устройства СВЧ / Высшая школа. М. - 1988, с.98) получим выражения для коэффициентов отражения:Where

- elements of the FU wave matrix normalized with respect to d (Feldstein A.L., Yavich L.R. Synthesis of four-terminal and eight-terminal networks / Communication. M. - 1971, p.30-40). We determine the input resistance of the two-terminal network and using the well-known expression for the reflection coefficient of the two-terminal network (Sazonov D.M. Antennas and microwave devices / Higher school. M. - 1988, p. 98) we obtain the expression for the reflection coefficients:

We substitute (3) into (1) and after separating the real and imaginary parts from each other, we obtain a system of two equations:

the solution of which is:

where: A _1,2 =

Therefore, the nth section of the layered medium with a given phase φ _{n of the} reflected signal at a fixed frequency must contain at least 2 elements (layers) in accordance with the number of equations (5). In this case, two layers should be assigned to the uncontrolled part, that is, to FU, and the remaining uncontrollable layers to the managed part. The parameters of the first two layers are determined analytically from the solution of the system system (5). The parameters of the remaining unmanaged layers are selected arbitrarily.

In accordance with the described algorithm, expressions are obtained for determining the thickness of the second dielectric layer and the conductivity of the lattice structure of the section of the layered structure shown in FIG. 5:

Where

n=1, 2,..., N; N - число независимых участков второй управляемой слоистой структуры; φ_n - заданные фазы коэффициентов отражения n-ого участка второй управляемой слоистой структуры; g₀, b₀ - действительная и мнимая части проводимости свободного пространства; g_yn, b_yn - действительная и мнимая части проводимости управляемых слоев в виде резистивных пленок n-ого участка второй управляемой слоистой структуры, определяемых толщиной пленки; параметры d₁, n₁, n₂ выбраны произвольно.

n = 1, 2, ..., N; N is the number of independent sections of the second controlled layered structure; φ _n - the specified phase of the reflection coefficients of the n-th section of the second controlled layered structure; g ₀ , b ₀ - real and imaginary parts of the conductivity of free space; g _yn , b _yn are the real and imaginary parts of the conductivity of the controlled layers in the form of resistive films of the nth portion of the second controlled layered structure, determined by the film thickness; the parameters d ₁ , n ₁ , n ₂ are chosen arbitrarily.

Numerical calculations in the Mathcad system showed that the phase of the reflection coefficient of an individual section of the layered medium with a change in the thickness of the resistive layer, which is equivalent to a change in the real and imaginary parts of its conductivity, varies within φ _{n =} 0 ° -360 ° depending on the values of g _yn , b _yn , which is sufficient to maintain the parabolic law of the phase change reflected from the reflector with sections of the layered medium of the signal within the main lobe. It should be noted that the case b ₀ = -0 is degenerate - the modulus of the reflection coefficient reaches a value of 1 only if φ _n = 180 °. This case is equivalent to reflection from a metal with high conductivity. Case b ₀ ≠ 0 corresponds to increased humidity or rainfall.

Thus, the results can be used for the practical design of sections of layered media placed on the surface of the reflector, in the interest of ensuring a decrease in the level of the side lobes of the antenna in a wide frequency band, which leads to an additional decrease in the ESR of the antenna not only during non-working periods, but also in workers, while maintaining the level of reduction of the EPR of the antenna within its main lobe.

The technical and economic efficiency of the method and device for its implementation consists in the possibility of reducing the level of the side lobes of the antenna in a wide frequency band, which leads to an additional reduction in the EPR of the antenna not only during non-working periods of time, but also in working ones, while maintaining the level of reduction of the EPR of the antenna within its main petal.

The proposed technical solution - the method is new, because from publicly available information there is no known way to reduce the effective antenna scattering surface, which reduces the level of the side lobes of the antenna in a wide frequency band, which leads to an additional decrease in the ESR of the antenna not only during non-working periods, but also in workers, while maintaining the level of reduction of the EPR of the antenna within its main lobe.

The proposed device for implementing this method is new, because from publicly available information, a device consisting of a radome made of a layered medium switched from a transparency state to working periods of time to a reflection state during non-working periods of time, and sections of another layered medium placed randomly image on the antenna reflector and preserving the parabolic law of the phase change of the reflection coefficient of the reflector.

The proposed technical solutions have an inventive step, since it does not explicitly follow from the published scientific data and the known technical solutions that the claimed sequence of operations is the implementation of an antenna cone from a layered medium switched from a transparency state to working time intervals to a reflection state during non-working time periods, placement sections of another layered medium randomly on the antenna reflector, the choice of the parameters of this layered medium from the condition of conservation of parabolic The law of changing the phase of the reflectance of the reflector leads to a decrease in the level of the side lobes of the antenna in a wide frequency band, which leads to an additional decrease in the EPR of the antenna not only during non-working periods of time, but also in working ones, while maintaining the level of decrease in the EPR of the antenna within its main petal.

The proposed technical solution is industrially applicable, since known dielectric materials, resistive graphite films of various thicknesses, two-dimensional-periodic lattices of conductive elements of various configurations, including the inclusion of controlled elements in the breaks of these lattices, the parameters of which are uniquely determined, can be used for its implementation obtained mathematical expressions given in the claims.

Claims (2)

1. A method of reducing the EPR of antennas based on the use of the first controlled layered structure in the form of a screen or fairing, the installation of a screen or fairing in front of the antenna, the switching of the first controlled layered structure from the transmission state at the time of emission and reception of pulses to the reflection state at the time coinciding with the times of emission and reception of pulses, characterized in that independent reflectors are additionally randomly arranged on the reflectors of the antennas conformally with their surface angled from each other, sections of the second controlled layered structure with dimensions of no less than 5λ × 5λ that change the phase of the reflected signal in such a way that the signals reflected from these sections in the direction of the side lobes are not in phase, and the parabolic law of the coefficient phase variation is preserved within the main lobe reflector reflection, λ is the wavelength. 2. A device for reducing the EPR of antennas, made in the form of a fairing or screen mounted in front of the antenna, and the fairing or screen is made on the basis of the first controlled layered structure, consisting of adjacent to each other the first metal square lattice, the first dielectric layer, controlled two-dimensionally periodic lattice conductive strips or rods, in the gaps of which are ferroceramic capacitors or pin diodes, the second dielectric layer and the second metal grating, identical to the first dielectric layer and the first grating, moreover, one system of parallel strips forming each grating is isolated at a low frequency from another system of parallel strips perpendicular to the first, and the system of parallel strips forming gratings is rotated 45 ° relative to the strips of the controlled grating, the intersection point which are alternately connected by conductors perpendicular to the plane of the layers, with one of the systems of parallel strips of the second lattice, connected alternately to different terminals of the generator leveling signals, connected to the output of the automatic tracking system in range, the thickness of the dielectric layers being equal to half the radar operating wavelength, and the conductivity B of the gratings, the inductance X _{0 of the} strips and the capacitance X _w of the gratings of the controlled grating are determined using the relations obtained from the conditions for the maximum reflection coefficient in one of the states of capacitors or diodes, determined by the levels of control voltage, and the minimum signal attenuation in another TATUS controlled elements, characterized in that the reflector antenna is conformal with the surface randomly arranged independent from each other portions of the second controllable layered structure with dimensions not less than 5λ × 5λ, each of which is made of successively transferred by the reflector of the first dielectric layer thickness d ₁ and the refractive index n _{1 of the} controlled layer in the form of a resistive film, a second dielectric layer of thickness d ₂ and the refractive index n ₂ and two-dimensionally periodic gratings and conductive strips or rods with reactive conductivity B _p , while the thickness of the second dielectric layer and the conductivity of a two-dimensional periodic grating are selected using the expressions:

where M = AD + (2 + B) (1-C);

n = 1, 2 ..., N; N is the number of independent sections of the second controlled layered structure; φ _n are the specified phases of the reflection coefficients of the nth portion of the second controlled layered structure; g ₀ , b ₀ - real and imaginary parts of the conductivity of free space; g _yn , b _yn are the real and imaginary parts of the conductivity of the controlled layers in the form of resistive films of the nth portion of the second controlled layered structure, determined by the film thickness; the parameters d ₁ , n ₁ , n ₂ are chosen arbitrarily.

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