CN111478056A - Nonreciprocal wave-absorbing material and manufacturing method thereof - Google Patents
Nonreciprocal wave-absorbing material and manufacturing method thereof Download PDFInfo
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- CN111478056A CN111478056A CN202010305614.6A CN202010305614A CN111478056A CN 111478056 A CN111478056 A CN 111478056A CN 202010305614 A CN202010305614 A CN 202010305614A CN 111478056 A CN111478056 A CN 111478056A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q17/00—Devices for absorbing waves radiated from an antenna; Combinations of such devices with active antenna elements or systems
- H01Q17/007—Devices for absorbing waves radiated from an antenna; Combinations of such devices with active antenna elements or systems with means for controlling the absorption
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Abstract
The invention discloses a nonreciprocal wave-absorbing material and a manufacturing method thereof, wherein the wave-absorbing material is a plate-shaped structural body and comprises the following components: a metal back plate is attached to the bottom surface of the filling medium plate; all the wave absorbing units are embedded in the filling dielectric plate in parallel at intervals; each group of wave absorbing units comprises a long-strip-shaped gyromagnetic ferrite column, a metal strip is attached to the surface of one side of the long-strip-shaped gyromagnetic ferrite column, the length of the metal strip is equal to that of the long-strip-shaped gyromagnetic ferrite column, and the width of the metal strip is smaller than the height of the side surface of the long-strip-shaped gyromagnetic ferrite column; the bias magnetic field applying assembly is embedded outside the wave absorbing unit arranged in the filling medium plate and can apply a bias magnetic field to the wave absorbing unit, and the direction of the bias magnetic field is parallel to the electric field direction of incident waves. The wave-absorbing material with the structure can break the time reversal symmetry of each long strip-shaped gyromagnetic oxide column by using an external bias magnetic field, thereby generating the nonreciprocal electromagnetic property and effectively inhibiting the transmission of reflected waves in the material.
Description
Technical Field
The invention relates to the field of wave-absorbing materials, in particular to a nonreciprocal wave-absorbing material and a manufacturing method thereof.
Background
The wave-absorbing material is an electromagnetic material or an electromagnetic structure capable of absorbing, losing and attenuating electromagnetic waves in a microwave frequency band. The wave-absorbing material has very important application in stealth, electromagnetic interference resistance, electromagnetic shielding and other aspects.
The wave-absorbing material converts the energy of the electromagnetic waves into heat energy loss through the interaction with the electromagnetic waves. The absorption performance of the wave-absorbing material to electromagnetic waves depends on whether the material has proper electromagnetic loss or not and whether the electromagnetic waves can smoothly enter the wave-absorbing material from a free space or not. Therefore, a good wave-absorbing material must have the following two conditions: 1) impedance matching at the interface: the incident electromagnetic wave can enter the wave-absorbing material to the maximum extent without reflection at the interface, that is, the characteristic impedance of the surface of the wave-absorbing material is required to be close to the impedance of free space. 2) Good loss characteristics: the electromagnetic wave entering the wave-absorbing material can be absorbed and attenuated quickly, i.e. the wave-absorbing material has good loss characteristics.
The existing wave-absorbing materials can be divided into material type wave-absorbing materials and structural type wave-absorbing materials according to different designs and implementation modes. For the traditional wave-absorbing material, whether the material type wave-absorbing material or the structural type wave-absorbing material is a reciprocal wave-absorbing material, that is, electromagnetic waves can be transmitted in two directions. The wave absorbing process of the conventional wave absorbing material 10 is shown in fig. 1, when an incident electromagnetic wave a is incident to the wave absorbing material from a free space, the incident electromagnetic wave a firstly enters the wave absorbing material and is partially lost and absorbed, energy which is not completely absorbed is reflected by a metal back plate to form a reflected wave B, and the reflected wave B is reversely transmitted in the wave absorbing material and enters the free space again. For the wave-absorbing material with reciprocity property, the electromagnetic wave can enter the wave-absorbing material from the free space, and can also enter the free space again from the inside of the wave-absorbing material through reflection, so the wave-absorbing material is difficult to stop the reflected wave from the structure principle. Meanwhile, the loss efficiency of the wave-absorbing material is limited, so that the reflected wave has certain strength, the radar scattering area of the stealth object using the wave-absorbing material is increased, the stealth effect is poor, and the observability is enhanced.
Disclosure of Invention
Based on the problems in the prior art, the invention aims to provide a nonreciprocal wave-absorbing material and a manufacturing method thereof, which can solve the problem that the stealth performance of the wave-absorbing material is influenced by reflected waves generated by the bidirectional transmission of electromagnetic wave energy in the conventional reciprocity wave-absorbing material.
The purpose of the invention is realized by the following technical scheme:
the embodiment of the invention provides a nonreciprocal wave-absorbing material, which is a plate-shaped structural body and comprises the following components:
the device comprises a filling medium plate, a metal back plate, at least one group of wave absorbing units and a bias magnetic field applying assembly; wherein the content of the first and second substances,
the metal back plate is attached to the bottom surface of the filling dielectric plate and covers the bottom surface of the filling dielectric plate;
all the wave absorbing units are embedded in the filling dielectric plate in parallel at intervals;
each group of wave absorbing units comprises a long-strip-shaped gyromagnetic ferrite column, a metal strip is attached to the surface of one side of the long-strip-shaped gyromagnetic ferrite column, the length of the metal strip is equal to that of the long-strip-shaped gyromagnetic ferrite column, and the width of the metal strip is smaller than the height of the side surface of the long-strip-shaped gyromagnetic ferrite column;
the bias magnetic field applying assembly is embedded in the filling dielectric plate and located outside the wave absorbing unit, a bias magnetic field can be applied to the wave absorbing unit by the bias magnetic field applying assembly, the direction of the bias magnetic field is parallel to the electric field direction of incident waves, and the long-strip-shaped gyromagnetic iron oxide column of the wave absorbing unit can be magnetized into tensor form with magnetic conductivity containing off-diagonal imaginary terms in a saturated way.
The embodiment of the invention also provides a method for manufacturing the wave-absorbing material based on the principle of symmetry deficiency in time reversal, which is used for manufacturing the wave-absorbing material disclosed by the invention and comprises the following steps:
a metal strip is adhered to the surface of one side of a strip-shaped gyromagnetic ferrite column to form a group of wave absorbing units;
embedding all groups of wave-absorbing units in the filling dielectric plate in parallel at intervals;
a metal back plate is attached to the bottom surface of the filling dielectric plate and covers the whole bottom surface of the filling dielectric plate;
the bias magnetic field applying assembly is embedded in the filling dielectric plate and positioned outside the wave absorbing unit, a bias magnetic field can be applied to the wave absorbing unit by the bias magnetic field applying assembly, the direction of the bias magnetic field is parallel to the electric field direction of incident waves, and the long-strip-shaped gyromagnetic iron oxide column of the wave absorbing unit can be magnetized in a saturated mode to form magnetic conductivity into a tensor form containing off-diagonal imaginary terms.
According to the technical scheme provided by the invention, the wave-absorbing material based on the time reversal symmetry defect principle and the manufacturing method thereof have the beneficial effects that:
at least one group of wave absorbing units are embedded in a filling medium plate with a metal back plate on one side surface, and a bias magnetic field applying assembly is arranged outside the wave absorbing units to form a wave absorbing material with a plate-shaped structure, each wave absorbing unit consists of a strip-shaped gyromagnetic oxygen column and a metal strip adhered to the surface of one side of the strip-shaped gyromagnetic oxygen column, the wave-absorbing unit with the structure is matched with a filling medium plate provided with a metal back plate, is designed based on the principle of time reversal symmetry deficiency, is a wave-absorbing material with nonreciprocal transmission characteristics on incident electromagnetic waves and reflected electromagnetic waves, and compared with the traditional wave-absorbing material, the wave-absorbing material can inhibit the reverse transmission of the reflected wave from the inside of the wave-absorbing material to the free space while losing the space electromagnetic wave entering the wave-absorbing material, thereby realizing more efficient wave absorption. The wave-absorbing material can break the time reversal symmetry of each long strip-shaped gyromagnetic oxide column by using an external bias magnetic field, thereby generating the nonreciprocal electromagnetic property and effectively inhibiting the transmission of reflected waves in the material. Provides a new idea for designing high-efficiency, broadband and low-frequency wave-absorbing materials.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
FIG. 1 is a schematic view of a wave-absorbing process of a conventional wave-absorbing material;
FIG. 2 is a schematic view of a non-reciprocal wave-absorbing material provided in embodiment 1 of the present invention;
FIG. 3 is a side view of a non-reciprocal wave-absorbing material according to embodiment 1 of the present invention;
fig. 4 is a schematic diagram of generating a dc applied bias magnetic field by using a square magnet according to embodiment 1 of the present invention;
FIG. 5 is a schematic diagram of generating a DC externally applied bias magnetic field by using a spiral coil according to embodiment 1 of the present invention;
fig. 6 is a dispersion relation curve between a phantom and a surface mode of electromagnetic waves in a long-strip-shaped gyromagnetic ferrite column of the wave-absorbing material provided in embodiment 1 of the present invention;
fig. 7 is a schematic view of a transmission process in the electromagnetic wave absorbing material provided in embodiment 1 of the present invention; wherein, (a) is a schematic diagram of the transmission process of electromagnetic waves in a metal-strip-free structure; (b) the transmission process of electromagnetic waves in a metal strip structure is shown schematically;
fig. 8 is a diagram of a simulation result of S11 parameter of the wave-absorbing material provided in embodiment 1 of the present invention;
FIG. 9 is a diagram showing simulation results of S11 parameters of the wave-absorbing material under different magnitudes of applied bias magnetic fields according to embodiment 1 of the present invention;
FIG. 10 is a schematic view of a wave-absorbing material based on a principle of symmetry breaking in time reversal according to embodiment 2 of the present invention;
fig. 11 is a side view of a wave-absorbing material based on a principle of symmetry breaking in time reversal according to embodiment 2 of the present invention;
fig. 12 is a graph of a simulation result of S11 parameters of the wave-absorbing material provided in embodiment 2 of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention are clearly and completely described below with reference to the specific contents of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention. Details which are not described in detail in the embodiments of the invention belong to the prior art which is known to the person skilled in the art.
As shown in fig. 2, 3 and 4, an embodiment of the present invention provides a non-reciprocal wave-absorbing material, which is designed based on a principle of symmetry loss in time reversal, and the wave-absorbing material is a plate-shaped structural body, and includes:
the device comprises a filling medium plate, a metal back plate, at least one group of wave absorbing units and a bias magnetic field applying assembly; wherein the content of the first and second substances,
the metal back plate is attached to the bottom surface of the filling dielectric plate and covers the bottom surface of the filling dielectric plate;
all the wave absorbing units are embedded in the filling dielectric plate in parallel at intervals;
each group of wave absorbing units comprises a long-strip-shaped gyromagnetic ferrite column, a metal strip is attached to the surface of one side of the long-strip-shaped gyromagnetic ferrite column, the length of the metal strip is equal to that of the long-strip-shaped gyromagnetic ferrite column, and the width of the metal strip is smaller than the height of the side surface of the long-strip-shaped gyromagnetic ferrite column;
the bias magnetic field applying assembly is embedded in the filling dielectric plate and located outside the wave absorbing unit, a bias magnetic field can be applied to the wave absorbing unit by the bias magnetic field applying assembly, the direction of the bias magnetic field is parallel to the electric field direction of incident waves, and the long-strip-shaped gyromagnetic iron oxide column of the wave absorbing unit can be magnetized into tensor form with magnetic conductivity containing off-diagonal imaginary terms in a saturated way.
In the wave absorbing material, the long-strip-shaped gyromagnetic ferrite column is a long-strip-shaped structural body. The section of the long-strip-shaped gyromagnetic ferrite column can be rectangular, square or polygonal.
In the wave absorbing material, the height of the long-strip-shaped gyromagnetic ferrite column is equal to or less than the thickness of the filling medium plate.
In the wave absorbing material, when the height of the long-strip-shaped gyromagnetic ferrite column is smaller than the thickness of the filling medium plate, the top surface of the long-strip-shaped gyromagnetic ferrite column and the top surface of the filling medium plate are in the same plane.
In the wave-absorbing material, the ratio of the width of the metal strip to the height of the side surface of the long-strip-shaped gyromagnetic ferrite column is 1:20 to 1: 5. The proportion of the two can be properly adjusted according to the specific structure and the application frequency band.
In the wave-absorbing material, the bias magnetic field applying assembly adopts two permanent magnets which are respectively arranged at the front end and the rear end of each group of wave-absorbing units; or the bias magnetic field applying assembly adopts a plurality of electrified spiral coils, and each electrified spiral coil is sleeved on the periphery of one group of wave absorbing units. Preferably, the bias magnetic field applying component forms an external bias magnetic field which is a uniform direct-current bias magnetic field. The strip-shaped gyromagnetic ferrite column can be magnetized through an external bias magnetic field of the bias magnetic field applying assembly, so that the magnetic conductivity of the strip-shaped gyromagnetic ferrite column is in a tensor form containing off-diagonal imaginary number terms, the time reversal symmetry of the material is broken, and the nonreciprocal electromagnetic property is realized.
In the wave absorbing material, the long-strip-shaped gyromagnetic ferrite columns are periodically arranged in the filling dielectric plate along the orthogonal direction of the external bias magnetic field. Under the action of an external direct-current bias magnetic field, the long-strip-shaped gyromagnetic ferrite column can be saturated and magnetized, and the magnetic permeability of the long-strip-shaped gyromagnetic ferrite column is in a tensor form containing off-diagonal imaginary terms. This form of permeability will break the time reversal symmetry, resulting in non-reciprocal electromagnetic properties. The gyromagnetic ferrite column mainly plays a role in exciting a unidirectional surface wave mode and performing loss absorption on electromagnetic waves.
In the wave absorbing material, the metal strip is attached to the surface of one side of the long-strip gyromagnetic ferrite column supporting the unidirectional transmission of the reflected wave, and the metal strip has the main function of blocking the reverse surface wave transmitted from the interior of the wave absorbing material to the free space along the surface of the gyromagnetic ferrite column.
In the wave-absorbing material, the filling dielectric plate is a plate body made of a dielectric material, and the filling dielectric plate mainly plays a role in supporting and fixing the long strip-shaped gyromagnetic ferrite column and adjusting the structural impedance so as to reduce the reflection of electromagnetic waves at the interface of the wave-absorbing material and a free space.
In the wave-absorbing material, the metal back plate is positioned at the bottommost part of the filling medium plate and is a large continuous metal sheet. The thickness of the metal back plate is larger than the skin depth of the electromagnetic waves in the working frequency band of the wave absorbing unit, so that the electromagnetic waves cannot penetrate through the metal back plate. Generally, the thickness of the metal back plate is more than 0.1mm to meet the requirement.
The invention embodiment of a method for manufacturing a nonreciprocal wave-absorbing material, which is used for manufacturing the wave-absorbing material, comprises the following steps:
a metal strip is adhered to the surface of one side of a strip-shaped gyromagnetic ferrite column to form a group of wave absorbing units;
embedding all groups of wave-absorbing units in the filling dielectric plate in parallel at intervals;
a metal back plate is attached to the bottom surface of the filling dielectric plate and covers the whole bottom surface of the filling dielectric plate;
the bias magnetic field applying assembly is embedded in the filling dielectric plate and positioned outside the wave absorbing unit, a bias magnetic field can be applied to the wave absorbing unit by the bias magnetic field applying assembly, the direction of the bias magnetic field is parallel to the electric field direction of incident waves, and the long-strip-shaped gyromagnetic iron oxide column of the wave absorbing unit can be magnetized into magnetic conductivity in a saturated mode in a tensor form containing off-diagonal imaginary terms.
The wave-absorbing material is designed based on the principle of lacking of time reversal symmetry, so that the electromagnetic waves in the wave-absorbing material have the characteristic of one-way transmission, and the wave-absorbing material is a non-reciprocal wave-absorbing material and can overcome the defect that the electromagnetic waves in the conventional reciprocal wave-absorbing material can be transmitted in two ways and cause reflection. The wave absorbing structure can enable electromagnetic waves to enter the wave absorbing structure from a free space and be transmitted forward and lost, and meanwhile, the metal back plate of the wave absorbing material or the structure behind the wave absorbing material is effectively inhibited from reflecting the backward transmission of the electromagnetic waves, so that the high-efficiency wave absorption is realized. The wave-absorbing frequency band of the wave-absorbing material body can be regulated and controlled by the magnitude of an external bias magnetic field, so that the wave-absorbing material body has great flexibility in application.
The embodiments of the present invention are described in further detail below.
The invention uses the periodic gyromagnetic ferrite column with broken time reversal symmetry as the main body part of the wave-absorbing material, realizes the supporting and fixing and impedance matching adjustment functions by using a medium material, and brings a metal strip tightly attached to one side surface of the gyromagnetic ferrite to block reflected waves transmitted in the reverse direction, thereby realizing the one-way transmission of electromagnetic waves in the wave-absorbing material structure. The invention applies an external magnetic field with a certain size to the gyromagnetic ferrite, so that the gyromagnetic ferrite column is saturated and magnetized, and the magnetic conductivity is in a tensor form containing off-diagonal imaginary number terms. This form of permeability breaks the time-reversal symmetry of the gyromagnetic ferrite material, thereby creating a unidirectional surface mode on the surface of the gyromagnetic ferrite material. The surfaces of the two opposite sides of the gyromagnetic ferrite column only allow unidirectional transmission of electromagnetic surface waves in opposite directions respectively, and the unidirectional transmission direction of the electromagnetic waves, the surface normal direction and the bias magnetic field direction are in a right-handed spiral relationship. The metal strip is attached to the surface of one side of the gyromagnetic ferrite column supporting reverse electromagnetic wave transmission, so that the one-way transmission of the electromagnetic wave on the surface can be blocked, the opposite surface of the gyromagnetic ferrite column has asymmetric transmission performance, the electromagnetic wave entering the wave absorbing material from the free space can be transmitted in the forward direction, and the reflected wave formed after being reflected by the metal back plate is restrained and lost and absorbed. The structure and performance of the wave-absorbing material of the invention are specifically explained below with reference to specific examples.
Example 1
The wave-absorbing material based on the principle of symmetry loss of time reversal in the embodiment is a periodic structure, is continuous along the direction of an electric field of incident electromagnetic waves and is periodically distributed along the direction of a magnetic field of the incident electromagnetic waves, and is a plate-shaped structural body, and is composed of a filling dielectric plate 1, a metal back plate 2 and a plurality of groups of wave-absorbing units; the bottom surface of the filling dielectric plate 1 is pasted with a metal back plate 2, and the metal back plate 2 completely covers the bottom surface of the filling dielectric plate; a plurality of groups of wave absorbing units are embedded and fixedly arranged in the filling dielectric slab at intervals in parallel, each group of wave absorbing units comprises a strip-shaped gyromagnetic ferrite column 3, and a metal strip 4 is tightly attached to the surface of one side of the strip-shaped gyromagnetic ferrite column 3; the wave-absorbing material is also provided with a bias magnetic field applying assembly which is embedded in the filling medium plate and is positioned outside the wave-absorbing unit, the bias magnetic field applying assembly can apply a bias magnetic field to the wave-absorbing unit, the direction of the bias magnetic field is parallel to the direction of an electric field of incident waves, and the long-strip-shaped gyromagnetic iron oxide column of the wave-absorbing unit can be magnetized into magnetic conductivity in a saturated way to be in a tensor form containing off-diagonal imaginary number terms.
Wherein the long-strip-shaped gyromagnetic ferrite column is a long-strip-shaped cylinder which is made of commercial Yttrium Iron Garnet (YIG) ferrite material and has a rectangular cross section, the saturation magnetization intensity of the long-strip-shaped gyromagnetic ferrite column is 4 pi Ms, the line width delta H and the relative dielectric constant of the long-strip-shaped gyromagnetic ferrite column arerAnd loss tangents of 1800Gauss, 25Oe, 15 and 0.0002, respectively; the long-strip-shaped gyromagnetic ferrite column is rectangular, the height d1 of the column is 10mm, and the thickness w of the column is 2.5 mm. Each long-strip-shaped gyromagnetic ferrite column is continuous along the y axis, a plurality of long-strip-shaped gyromagnetic ferrite columns are periodically distributed along the x axis, and the interval wp between every two adjacent units is 13.5 mm. The long-strip-shaped gyromagnetic ferrite column mainly plays a role in exciting a unidirectional surface wave mode and performing loss absorption on electromagnetic waves.
The metal strip is closely attached to one side surface of the long-strip-shaped gyromagnetic ferrite, is continuous along the y axis, has the width d2 of 1mm in the z axis direction, is attached to the middle part of one side surface of the long-strip-shaped gyromagnetic ferrite, and has the main function of blocking reverse surface waves transmitted from the interior of the wave absorbing material to the free space along the surface of the gyromagnetic ferrite column.
The filling dielectric plate is a plate body made of foam dielectric materials, the relative dielectric constant of the filling dielectric plate is 1.1, the loss tangent angle is 0.002, and the thickness d1 is 10 mm. The main function of the device is to support and fix the gyromagnetic ferrite column and adjust the structural impedance so as to reduce the reflection of electromagnetic waves at the interface of the material and the free space.
The metal back plate is a thin copper plate, and the thickness of the metal back plate is 0.5 mm.
The bias magnetic field applying component of the wave-absorbing material can adopt a permanent magnet (see figure 4) or an electrified spiral coil (see figure 5). Can generate a DC bias magnetic field with the size of H0The direction is parallel to the direction of the electric field of the incident electromagnetic wave, i.e., the + y direction in fig. 2. The magnetic permeability of the long-strip-shaped gyromagnetic ferrite columns is in a tensor form containing off-diagonal imaginary terms.
There are various methods for generating the dc bias magnetic field, and typical methods include: a bias magnetic field is generated by using the permanent magnet bias magnetic field applying unit and a bias magnetic field is generated by using the energized spiral coil as the bias magnetic field applying unit. FIG. 4 is a schematic view of applying a bias magnetic field to the wave-absorbing material by using a permanent magnet. Wherein the labels of the components are: the device comprises a filled dielectric plate 1, a metal back plate 2, ferrite columns 3, metal strips 4 and square permanent magnets 5. Magnetic field H generated between two adjacent square magnets0A linear superposition of the magnitudes of the magnetic field components in the y-direction generated by the two square magnets alone. To ensure that the magnetic field generated by the square magnet is as uniform as possible, the width wm of the square magnet should be at least twice the height d1 of the ferrite. By adjusting the geometric dimensions of the square magnet, such as length lm, width wm, and thickness tm, and by appropriately selecting the magnetization of the square permanent magnet, a relatively uniform dc applied magnetic field can be obtained. The size and the distribution of the magnetic field generated by the square magnet in the space can be obtained by two modes of numerical calculation and simulation calculation.
FIG. 5 is a schematic view of applying an external bias magnetic field to the wave-absorbing material by using a DC-powered spiral coil. Wherein the reference numerals 1-5 are respectively a dielectric material, a metal back plate, ferrite posts, a metal strip and a spiral coil. When the spiral coil is connected with a direct current with certain intensity, a relatively uniform direct current external magnetic field can be generated in the coil. By adjusting parameters such as the current in the coil, the wire diameter of a lead in the coil, the number of turns of the coil and the like, the direct-current magnetic fields with different sizes can be obtained theoretically.
When an external bias magnetic field acts on the long-strip gyromagnetic ferrite material, the magnetic conductivity of the long-strip gyromagnetic ferrite medium is in a tensor form, and the tensor form is as follows:
in the formula (1), the reaction mixture is,
ω0＝μ0γH0，ωm＝μ0γ 4 π Ms, where 4 π Ms is the saturation magnetization of the ferrite, H0Gamma is the gyromagnetic ratio of the ferrite material for the magnitude of the applied bias magnetic field.
Time reversal symmetry is also called time reversal invariance. Time-reversal symmetry describes the symmetry of a physical system under time-reversal operation. In electromagnetism, time-reversal symmetry often corresponds to symmetry or reciprocity in electromagnetic behavior. If the constitutive equation is used to describe the influence of the medium on the electromagnetic field, the method is as follows:
in three dimensions, dielectric constant
Magnetic permeability
Magnetoelectric coupling term
And
both in the form of a 3 × 3 matrix, the condition for time-reversal symmetry can be expressed as:
when the dielectric constant or magnetic permeability is in a tensor form, and an off-diagonal term has an imaginary number with opposite sign, the reversible condition is broken, the medium no longer has time reversal symmetry, and unique electromagnetic phenomena such as a magnetic surface unidirectional transmission surface wave and the like are generated.
Suppose α0And α1The dispersion relation of the electromagnetic wave in the air and the inside of the gyromagnetic ferrite can be obtained by simultaneous Maxwell's equation and formula (1) which respectively represent the loss coefficients of the electromagnetic wave in vacuum and the gyromagnetic ferrite:
k2＝α0 2+ω2/c2(4)
k2＝k0 2 rμ(1-k2/μ2)+α1 2(5)
then, by using the boundary condition at the surface of the gyromagnetic medium, the electromagnetic wave dispersion relation at the surface of the gyromagnetic medium can be obtained as follows:
in the formula (6), mumode＝(μ2-κ2) Mu is calculated as a unit. The surface mode dispersion curves of the surface electromagnetic wave and the phantom inside the gyromagnetic ferrite under the action of the applied bias magnetic field can be obtained by using the equations (5) and (6), as shown in fig. 6. Wherein the curve 1 is obtained by the formula (5) and is an electromagnetic wave phantom dispersion curve inside the gyromagnetic ferrite; the curve 2 is obtained by the formula (6) and is an electromagnetic wave surface mode dispersion curve at the surface of the gyromagnetic ferrite; curve 3 represents the dispersion curve of the electromagnetic wave in free space. The three dotted lines from top to bottom in FIG. 6 correspond to the upper boundary frequency ω of the phantom forbidden bandUMagnetic surface resonance frequency omegaSPAnd lower boundary frequency omega of the phantom forbidden bandL. It can be seen that the surface mode dispersion curve of gyromagnetic ferrite exhibits significant left-right asymmetry. In frequency band omegaSPTo omegaUIn between (nonreciprocal gap), the surface mode dispersion curve is only at k<Presence within the region of 0, ωSPAnd ωUThe following expression (7) and (8) can be used to obtain:
ωSP＝ω0+ωm/2 (7)
ωU＝ω0+ωm(8)
therefore, in the frequency band of the nonreciprocal forbidden band, the electromagnetic wave can only be transmitted along the surface of the gyromagnetic material in a single direction. At the same time due to omegaSPAnd ωUAre all related to the magnitude of the external bias magnetic field, so that the working frequency band of the non-reciprocal transmission can be changed by changing the magnitude of the external bias magnetic field.
Therefore, for the structure periodically arranged along the x-axis in fig. 7, under the applied bias magnetic field, the gyromagnetic ferrite is saturated and magnetized, the time reversal symmetry is broken, and an electromagnetic wave unidirectional transmission mode is excited at the surface. The supported unidirectional transmission directions of the electromagnetic waves are opposite on two opposite surfaces of the gyromagnetic ferrite. A, B in FIG. 7 represents the direction in which the two opposing surfaces of the gyromagnetic ferrite support the unidirectional transmission of electromagnetic waves. When the space electromagnetic wave is incident into the wave-absorbing material, the space electromagnetic wave is firstly converted into a surface wave and can only be transmitted along a path A in a one-way; when the electromagnetic wave is transmitted to the bottom of the wave-absorbing material and reflected by the metal back plate 2, the electromagnetic wave is transmitted to the free space along the path B in a single direction. Therefore, the wave absorbing unit without the metal strip in the long-strip-shaped gyromagnetic ferrite column illustrated in fig. 7(a) supports transmission of incident waves and reflected waves inside the wave absorbing unit, and the incident waves enter the free space again after being reflected after being incident into the structure, so that the wave absorbing effect is not ideal. In order to block the reflected wave which is reversely transmitted along the path B, a metal strip 4 attached to the surface of the long gyromagnetic ferrite 3 is introduced, so that a wave-absorbing material which can inhibit the transmission of the reflected wave and can 'go in and go out' of the electromagnetic wave is formed, and the transmission process of the electromagnetic wave in the wave-absorbing material is shown in fig. 7 (B).
As shown in the simulation result of FIG. 8, when the magnitude of the applied bias magnetic field is 1200Oe, the absorption band of the wave-absorbing material based on the principle of symmetry loss of time reversal in this embodiment is 6.17-8.37 GHz, the absorption of electromagnetic waves at 7.92GHz is maximized, and the reflection coefficient of S11 is lower than-40 dB. Compared with the simulation result of the reciprocal wave-absorbing material without the metal strip, the simulation result shows that when the metal strip is not added in the structure, the structure has reciprocal property on incident waves and reflected waves, most of the energy of the reflected waves returns to the free space, and the wave-absorbing effect is poor; after the metal strip is added into the structure, the structure has the property of nonreciprocal transmission for incident waves and reflected waves, the incident waves can enter the structure, and the reflected waves cannot return to a free space from the structure, so that the structure can absorb electromagnetic waves more efficiently. Meanwhile, as can be seen from fig. 9, by changing the magnitude of the external bias magnetic field, the wave-absorbing frequency band of the wave-absorbing material based on the time reversal symmetry defect of the embodiment also changes correspondingly, which indicates that the wave-absorbing material has a certain magnetic adjustability. Under the condition that the parameters of the structure are not changed, the magnitude of the external bias magnetic field is changed within the range of 800-2000 Oe, and various wave-absorbing frequency bands within the range of 5-10 GHz frequency bands can be obtained. The wave-absorbing material has better flexibility by utilizing the characteristic of regulating and controlling the wave-absorbing frequency band by the external bias magnetic field.
Meanwhile, the structure described in example 1 has versatility and universality when designing a microwave-absorbing structure in a wider range of microwave frequency bands. After the target operating frequency band is determined, the structure described in example 1 may be expanded and applied to the target frequency band by the following method: determining the magnitude of an external magnetic field by using a formula 7 and a formula 8, and selecting the magnitude of the saturation magnetization of the gyromagnetic ferrite; according to the ratio of the central frequency point of the target frequency band to the central frequency point of the structure in the example 1, and by referring to the ratio, various parameters in the wave-absorbing material structure in the embodiment 1 illustrated in fig. 2 are amplified or reduced in an equal proportion and are properly adjusted by using simulation software, and the size of the structure is smaller when the working frequency band is higher generally; the acoustic wave absorbing material working in the target frequency band can be obtained by properly adjusting the distance between the metal back plate and the gyromagnetic ferrite structure and reasonably selecting the dielectric constant of the filling medium. The wave-absorbing material structure of example 2 can also be regarded as an expansion and modification of the wave-absorbing material structure of example 1.
Example 2
The unidirectional transmission working frequency band of the surface of the gyromagnetic ferrite is determined by the magnitude of an external bias magnetic field and the saturation magnetization of the gyromagnetic ferrite, and the absorption characteristic of the wave-absorbing material based on the time reversal symmetry deficiency principle is derived from the nonreciprocity of the structure, so that the designed wave-absorbing material can work in a target frequency band by reasonably selecting the two parameters.
The non-reciprocal wave-absorbing material based on the principle of symmetry deficiency in time reversal in the embodiment is realized by properly adjusting the structure and changing the parameters of the corresponding materials on the basis of the wave-absorbing material structure in the embodiment 1, and the working frequency band of the non-reciprocal wave-absorbing material is the P band. As shown in the basic structure of the wave-absorbing material in this embodiment illustrated in fig. 10 and the side view of the wave-absorbing material in fig. 11, the basic structure and composition of the wave-absorbing material in this embodiment are substantially the same as those of the wave-absorbing material in embodiment 1, except for the size and performance parameters of the long-strip-shaped gyromagnetic ferrite column.
In the wave absorbing unit of the wave absorbing material of this embodiment, the strip-shaped gyromagnetic ferrite material is a commercial ferrite material, and the saturation magnetization of the commercial ferrite material is 4 pi Ms, the line width Δ H, and the relative dielectric constantrAnd loss tangents of 250Gauss, 45Oe, 13.8, and 0.0002, respectively; the height d1 of the long-shaped gyromagnetic oxide column is 14mm, and the thickness w is 20 mm. Each strip-shaped gyromagnetic ferrite column is continuous along the y axis, a plurality of strip-shaped gyromagnetic ferrite columns are periodically distributed along the x axis, and the interval period wp between two adjacent groups of wave absorbing units is 102 mm. The long-strip-shaped gyromagnetic ferrite columns mainly play a role in exciting a unidirectional surface wave mode and absorbing loss of electromagnetic waves.
And a metal strip is tightly attached to one side surface of each strip-shaped gyromagnetic iron column, and the metal strips are continuous along the y axis and have the width d2 of 2.5mm along the z axis. The metal strip mainly plays a role in blocking reverse surface waves transmitted from the interior of the wave-absorbing material to free space along the surface of the gyromagnetic ferrite column.
The filled dielectric plate is made of a high-dielectric-constant dielectric material, the specific high-dielectric-constant dielectric material is Rogers RO3010, the relative dielectric constant is 10.2, the loss tangent angle is 0.0035, and the thickness d3 is 32 mm. The filled dielectric plate mainly has the functions of supporting and fixing the gyromagnetic ferrite column and adjusting the structural impedance so as to reduce the reflection of electromagnetic waves at the interface of the material and the free space.
The metal back plate is made of thin copper plates with the thickness of 0.5mm, and the distance h from the bottom of each long strip-shaped gyromagnetic ferrite column which is periodically arranged is 18 mm.
The external bias magnetic field adopts a direct-current bias magnetic field with the magnitude of H0The direction is parallel to the electric field direction of the incident electromagnetic wave, i.e., + y direction in fig. 10. The effect of the applied bias field is to magnetize the ferrimagnetic pillar such that its permeability is in the form of a tensor comprising off-diagonal imaginary terms.
As shown in the simulation result shown in FIG. 12, when the applied bias magnetic field H0 is 100Oe, the reflection coefficient S11 of the wave-absorbing material of this embodiment for electromagnetic waves in the frequency band of 0.66-0.96 GHz is lower than-10 dB, and the minimum reflection coefficient at 0.69GHz is-25 dB.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (9)
1. A nonreciprocal wave-absorbing material is characterized in that the wave-absorbing material is a plate-shaped structural body and comprises:
the device comprises a filling medium plate, a metal back plate, at least one group of wave absorbing units and a bias magnetic field applying assembly; wherein the content of the first and second substances,
the metal back plate is attached to the bottom surface of the filling dielectric plate and covers the bottom surface of the filling dielectric plate;
all the wave absorbing units are embedded in the filling dielectric plate in parallel at intervals;
each group of wave absorbing units comprises a long-strip-shaped gyromagnetic ferrite column, a metal strip is attached to the surface of one side of the long-strip-shaped gyromagnetic ferrite column, the length of the metal strip is equal to that of the long-strip-shaped gyromagnetic ferrite column, and the width of the metal strip is smaller than the height of the side surface of the long-strip-shaped gyromagnetic ferrite column;
the bias magnetic field applying assembly is embedded in the filling dielectric plate and located outside the wave absorbing unit, a bias magnetic field can be applied to the wave absorbing unit by the bias magnetic field applying assembly, the direction of the bias magnetic field is parallel to the direction of an electric field of incident waves, and the long-strip-shaped gyromagnetic iron oxide column of the wave absorbing unit can be magnetized in a saturation mode into magnetic conductivity in a tensor form containing off-diagonal imaginary terms.
2. The non-reciprocal wave-absorbing material of claim 1 wherein the elongated gyromagnetic ferrite posts are elongated structures.
3. The non-reciprocal wave-absorbing material of claim 1 or 2, wherein the height of the elongated gyromagnetic ferrite pillars is equal to or less than the thickness of the dielectric slab.
4. The non-reciprocal wave-absorbing material of claim 3, wherein when the height of the elongated gyromagnetic ferrite pillars is less than the thickness of the dielectric slab, the top surfaces of the elongated gyromagnetic ferrite pillars and the top surface of the dielectric slab are in the same plane.
5. A non-reciprocal wave-absorbing material as claimed in claim 1 or 2 wherein the ratio of the width of the metal strip to the height of the side surface of the elongated gyromagnetic-oxygen column is: 1:20 to 1: 5.
6. The non-reciprocal wave-absorbing material of claim 1 or 2, wherein the bias magnetic field applying assembly employs two permanent magnets, which are respectively disposed at the front and rear ends of each wave-absorbing unit;
or the bias magnetic field applying assembly adopts a plurality of electrified spiral coils, and each electrified spiral coil is sleeved on the periphery of one group of wave absorbing units.
7. The structure of claim 6, wherein the bias magnetic field applying assembly forms an external bias magnetic field that is a uniform dc bias magnetic field.
8. The structure of non-reciprocal wave-absorbing material of claim 1 or 2, wherein the thickness of the metal back plate is greater than the skin depth of the electromagnetic wave in the working frequency band of the wave-absorbing unit.
9. A method for manufacturing a non-reciprocal wave-absorbing material, which is used for manufacturing the wave-absorbing material of any one of claims 1 to 8, and comprises the following steps:
a metal strip is adhered to the surface of one side of a strip-shaped gyromagnetic ferrite column to form a group of wave absorbing units;
embedding all groups of wave-absorbing units in the filling dielectric plate in parallel at intervals;
a metal back plate is attached to the bottom surface of the filling dielectric plate and covers the whole bottom surface of the filling dielectric plate;
and a bias magnetic field applying component is arranged outside the wave absorbing unit, is embedded in the filling medium plate and can apply a bias magnetic field to the wave absorbing unit, the direction of the bias magnetic field is parallel to the electric field direction of incident waves, and the long-strip-shaped gyromagnetic iron oxide column of the wave absorbing unit can be magnetized in a saturated mode into a tensor form with magnetic conductivity containing off-diagonal imaginary terms.
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| CN106129563A (en) * | 2016-07-08 | 2016-11-16 | 中国人民解放军空军工程大学 | A kind of based on WAVEGUIDE LOADED ferritic adjustable microwave isolator |
-
2020
- 2020-04-17 CN CN202010305614.6A patent/CN111478056A/en active Pending
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106129563A (en) * | 2016-07-08 | 2016-11-16 | 中国人民解放军空军工程大学 | A kind of based on WAVEGUIDE LOADED ferritic adjustable microwave isolator |
Non-Patent Citations (3)
| Title |
|---|
| MING ZHANG: "Passive control of runaway electron displacement by magnetic energy transfer in J-TEXT", 《FUSION ENGINEERING AND DESIGN》 * |
| RAO BO: "Design of One-way Structure for Spatial EM Wave Based on the Magnetic Surface Plasmon States", 《2019 IEEE 5TH INTERNATIONAL CONFERENCE ON COMPUTER AND COMMUNICATIONS (ICCC)》 * |
| 朱旗: "碳纳米管阵列辐射的实验研究", 《电波科学学报》 * |
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