CN108736168A - A kind of optical clear electromagnetism applied to microwave section encodes Meta Materials and basic unit - Google Patents

Abstract

The invention discloses a kind of optical clear electromagnetism applied to microwave section to encode Meta Materials and basic unit, including more than one super subelement, the super subelement are mainly made of N × N number of basic cell structure, and N is non-zero positive integer；The basic cell structure is according to corresponding digital coding matrix arrangement on two dimensional surface；The basic cell structure includes the rectangular ITO layer (tin indium oxide) set gradually, dielectric-slab layer, zero transmission layer of air layer, dielectric-slab layer and total reflection.The present invention has many advantages, such as single layer structure, easy to process, and has optically transparent characteristic, can be used for controlling the applications such as wave beam deviation, the radar cross section that can also be used for reduction target.

Description

An optically transparent electromagnetically encoded metamaterial and basic unit for microwave applications

technical field

The invention relates to a novel artificial electromagnetic material, in particular to an optically transparent electromagnetic coding metamaterial in the microwave section.

Background technique

New artificial electromagnetic materials, also known as electromagnetic metamaterials (Metamaterials), are an artificial material composed of macroscopic basic units with specific geometric shapes arranged periodically/aperiodically, or implanted into the body (or surface) of the matrix material. . The difference between electromagnetic metamaterials and traditional materials is that the original microscopic units (atoms or molecules) are replaced by macroscopic units. Although the unit sizes of the two are quite different, their responses to external electromagnetic waves are reflected by the interaction between the basic unit resonant system and the external electromagnetic field. Electromagnetic metamaterials define the behavior of electromagnetic waves from the perspective of media, and provide new ideas and methods for the design of microwave devices.

Capasso et al. proposed the generalized Snell's law in 2011. This theorem is the basic law describing the electromagnetic properties of the metamaterial surface. It takes into account the phase discontinuity and the resulting anomalies when electromagnetic waves are reflected or transmitted on the metamaterial surface. Reflection and refraction behavior. People can design artificial surface structures to artificially control this phase discontinuity, and then use two-dimensional metasurfaces to control spatially propagating waves. To achieve the purpose of arbitrarily controlling reflected and refracted waves. Realize such as vortex beam and Bessel beam, and even design a random phase distribution, so that the incident beam is randomly scattered in all directions to form diffuse reflection, thereby effectively reducing the radar cross-sectional area of the target and achieving stealth.

The units of the metamaterials mentioned above are all designed through opaque metals and media, that is, the designed metamaterials are opaque to visible light and cannot achieve stealth in the visible light frequency band.

Contents of the invention

Technical problem: In order to overcome the deficiencies in the prior art, the present invention provides an optically transparent electromagnetic encoding metamaterial and basic unit applied in the microwave segment, by designing a specific digital encoding matrix and correspondingly assigning it to each element in the material It can independently realize different functions under the irradiation of vertically incident electromagnetic waves, such as abnormal reflection, diffuse scattering, and reduction of radar cross-sectional area.

Technical solution: In order to achieve the above purpose, the technical solution adopted by the basic unit of an optically transparent electromagnetic coding metamaterial applied to the microwave section of the present invention is:

The basic unit of the electromagnetic encoding metamaterial includes a square indium tin oxide ITO layer, a dielectric plate layer, an air layer, a dielectric plate layer and a total reflection zero transmission layer arranged in sequence.

in,

The thickness of the dielectric plate layer is 0.5-1.0mm, the dielectric constant is 4.5-4.8, the thickness of the air layer is 2-3mm, and the loss tangent is 0.01-0.02.

The metamaterial of the optically transparent electromagnetic coded metamaterial basic unit applied to the microwave segment of the present invention includes more than one super subunit, and the super subunit is mainly composed of N×N basic units, and N is a non-zero positive integer.

There are two kinds of basic unit structures in the basic unit; by adjusting the side length of the square indium tin oxide ITO layer (1) film, it is obtained that two basic unit structures can be independently produced under the irradiation of normal incident linearly polarized electromagnetic waves. These two digital state responses correspond to two reflection phases. According to the two numerical state responses, two different phase digital state codes are obtained. These two different phase digital state codes correspond to two basic unit structures.

The two digital state responses generated are respectively "0" and "1", and the two reflection phases corresponding to these two digital state responses are 0 degrees and 180 degrees respectively; the two phase digital state codes are "0" and "1", which respectively represent the digital state of the reflection phase under the normal incident electromagnetic wave.

The period length L of the basic unit is 5-7mm.

Among the geometric parameters of the two basic unit structures, the side length of the square ITO layer of the "0" digital state coding unit is 2.7mm, and the side length of the square ITO layer of the "1 digital state" coding unit is 5.5mm.

The back side of the dielectric board layer is covered with a layer of ITO thin film.

Beneficial effects: Compared with the prior art, the optically transparent electromagnetic coding metamaterial and the basic unit structure provided by the present invention have the following beneficial effects:

1. The present invention is different from the traditional scheme of using equivalent medium parameters to analyze and design metamaterials, and analyzes and designs metamaterials from the perspective of digital coding, which greatly simplifies the design process.

2. The present invention adopts transparent glass and ITO film to design the metamaterial unit, so that the designed electromagnetic metamaterial has the characteristic of optical transparency.

3. The present invention realizes a variety of regulatory functions of electromagnetic metamaterials for electromagnetic waves through the combination of different coding sequences, including reflecting beams at specific angles and reducing radar cross section (RCS), so as to realize electromagnetic stealth.

4. The present invention has certain broadband characteristics. The designed metamaterial unit can realize the required design function in a wide frequency band.

5. The present invention is easy to process and easy to realize. Only relying on simple ITO patterns, it is easy to prepare and process in the microwave frequency range.

Description of drawings

Figure 1 is a schematic diagram of the electromagnetic wave regulation of the 1-bit coding metasurface under 4 different coding matrices.

Fig. 2 is a model diagram of the basic unit structure of the present invention.

Fig. 3 shows the reflection phase response and phase difference of the "0" and "1" digital state encoding units for normal incident electromagnetic waves.

Figure 4 shows four different encoding matrix patterns; Figure 4(a) is the S ₁ encoding pattern when the encoding matrix is [0 1 0 1 ...]; Figure 4(b) is the encoding matrix is [0 0 1 1 ...] S ₂ encoding pattern when ; Figure 4(c) S ₃ encoding pattern when the encoding matrix is [0 1 0 1…/ 1 0 1 0 …]; Figure 4(d) S ₄ encoding when the encoding matrix is random encoding pattern.

Fig. 5 is the far-field scattering pattern of the three-dimensional and two-dimensional numerical simulations of the three metasurfaces when the coding matrix is S ₁ , S ₂ and S ₃ ; Fig. 5(a) is the three-dimensional far-field scattering direction of the S ₁ coding matrix Fig. 5 (b) is the two-dimensional far-field scattering pattern of S ₁ coding matrix; Fig. 5 (c) is the three-dimensional far-field scattering pattern of S ₂ coding matrix; Fig. 5 (d) is S ₂ coding matrix Two-dimensional far-field scattering pattern; Figure 5(e) is the three-dimensional far-field scattering pattern of the S ₃ encoding matrix; Figure 5(f) is the two-dimensional far-field scattering pattern of the S ₃ encoding matrix.

Fig. ₆ is the metasurface 3D far-field scattering pattern with coding matrix S4; Fig. 6 (a) is the 3D far-field scattering pattern at 11.5 GHz; Fig. 6 (b) is the 3-D far-field scattering pattern at 12 GHz; Fig. 6(c) is the three-dimensional far-field scattering pattern at 12.5GHz.

Figure 7 is the experimental test results of the two-dimensional far-field scattering pattern; Figure 7(a) is the test result of the two-dimensional far-field scattering pattern of the S ₁ coding matrix; Figure 7(b) is the S ₄ coding matrix at the 11.5GHz frequency point Figure 7(c) is the test result of the two-dimensional far-field scattering pattern at the 12GHz frequency point of the S ₄ coding matrix; Figure 7(d) is the 12.5GHz frequency point of the S ₄ coding matrix The test results of the two-dimensional far-field scattering pattern at

Fig. 8 is a structural view of the basic unit structure, wherein Fig. 8(a) is a front view of the basic unit structure, and Fig. 8(b) is a sectional view along the line A-A of Fig. 8(a).

Among them are: square indium tin oxide ITO layer 1, dielectric plate layer 2, air layer 3, and total reflection zero transmission layer 4.

The meaning of each size parameter: a is the side length of the square indium tin oxide ITO layer; t is the thickness of the indium tin oxide ITO layer and the total reflection zero transmission layer; h is the thickness of the glass; H is the thickness of the air layer; p is the period length of the unit .

Detailed ways

The present invention is a basic unit structure of an optically transparent electromagnetic coded metamaterial applied in the microwave section, comprising a square ITO layer (indium tin oxide), a dielectric plate layer, an air layer, a dielectric plate layer and a total reflection zero transmission layer arranged in sequence.

An optically transparent electromagnetic coded metamaterial applied to the microwave segment, including more than one super subunit, the super subunit is mainly composed of N×N basic unit structures, N is a non-zero positive integer; the basic unit structure It includes a square ITO layer (indium tin oxide), a dielectric layer, an air layer, a dielectric layer and a total reflection zero transmission layer.

Preferably: the basic unit structure has two basic unit structures; by adjusting the side length of the square ITO film, it is obtained that two digital numbers can be independently generated for each basic unit structure under the irradiation of normal incident linearly polarized electromagnetic waves. The two digital state responses correspond to two reflection phases. According to the two numerical state responses, two different phase digital state codes are obtained. These two different phase digital state codes correspond to the two basic unit structures.

Preferably: the generated two digital state responses are "0" and "1" respectively, and the two reflection phases corresponding to these two digital state responses are 0 degrees and 180 degrees respectively; the two phase digital state codes are "0" and "1", which represent the reflection phase digital states under normal incident electromagnetic waves, respectively.

Preferably: the thickness of the dielectric layer is 0.5-1.0 mm, the dielectric constant is 4.5-4.8, the thickness of the air layer is 2-3 mm, and the loss tangent is 0.01-0.02.

Preferably: the unit period length p of the basic unit structure is 5-7 mm.

Preferably: the geometric parameters of the two basic unit structures are as follows: the side length of the square ITO layer of the "0" digital state coding unit is 2.7mm, and the side length of the square ITO layer of the "1 digital state" coding unit is 5.5mm.

Preferably: the back of the total reflection zero transmission layer is covered with a layer of ITO thin film.

Below in conjunction with specific embodiment, further illustrate the present invention, it should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention, after having read the present invention, those skilled in the art will understand various equivalent forms of the present invention All modifications fall within the scope defined by the appended claims of the present application. In the present invention, two kinds of electromagnetic metamaterial units with a phase response difference of 180 degrees are used as two kinds of digital encoding state "0" and "1" units, and different encoding matrices are designed to achieve specific function regulation. The present invention will be described in more depth below in conjunction with the accompanying drawings.

Figure 1 is a schematic diagram of the principle of 1-bit electromagnetic encoding metamaterial (metasurface) for electromagnetic wave regulation. For the same normal incident electromagnetic wave, designing metasurfaces with different encoding matrices can realize various control functions for electromagnetic waves, such as abnormal reflection at specific angles, diffuse scattering, and reduction of radar cross section.

Fig. 2 is a schematic diagram of the structure of a 1-bit electromagnetic encoding metamaterial unit. The "0" and "1" digital state coding units are, from top to bottom, an ITO thin film layer, a glass dielectric layer, an air layer, a glass dielectric layer and an ITO thin film layer. The unit period length p of the whole unit structure is 5-7mm, the thickness of the dielectric layer is 0.5-1.0mm, the dielectric constant is 4.5-4.8, the loss tangent is 0.01-0.02, and the thickness of the air layer is 2-3mm. The unit period length p of the basic unit structure is 5-7mm, and the thickness of the ITO thin film is 400nm.

As shown in Figure 3, by changing the side length of the ITO square film on the top layer, the "0" and "1" digital state encoding units with a phase response difference of 180 degrees can be obtained. The side length of the ITO square film corresponding to the "0" digital state coding unit is 2.7 mm, and the side length of the ITO square film corresponding to the "1" digital state coding unit is 5.5 mm. It can be seen from Figure 3 that the two digitally encoded state units produce a phase difference of 180 degrees at the 12Ghz frequency point, and the phase difference of the two digitally encoded state units is close to 180 degrees within a certain bandwidth.

Figure 4 shows the designed encoding metasurfaces for four different encoding matrices. In the present invention, we introduce super subunits, each subunit is composed of 5×5 identical “0” or “1” coding units to form a single coding bit, and a whole hypersurface consists of 12× It consists of 12 super subunits, so the size of the entire coded metasurface is 360mm×360mm.

Figure 5 is the far-field scattering pattern of three-dimensional and two-dimensional numerical simulations of metasurfaces under three different periodic encoding matrices. The frequency is 12 GHz, which mainly shows the control function of metasurfaces to make electromagnetic waves reflect abnormally at specific angles. Among them, the encoding matrix of S ₁ is [0 1 0 1 ...], the encoding matrix changes periodically in the direction of the x-axis, and remains unchanged in the direction of the y-axis; the encoding matrix of S ₂ is [0 0 1 1 ...], and the encoding matrix changes in the direction of the x-axis The upper period changes, and the y-axis direction remains unchanged; the S ₃ encoding matrix is [0 1 0 1.../ 1 0 1 0 ...], and the encoding matrix changes periodically in the x-axis and y-axis directions;

Figure 5(ab) shows the far-field scattering patterns of the 3D and 2D numerical simulations of the S ₁ coded matrix metasurface when the electromagnetic waves are perpendicularly incident. At this time, the reflected beam is a symmetrical double-beam output, and the beam deflection angle is 24.6 degrees. Figure 5(cd) shows the far-field scattering patterns of the 3D and 2D numerical simulations of the S2 encoding matrix _metasurface for normal normal incident electromagnetic waves. At this time, the reflected beam is a symmetrical dual-beam output, and the beam deflection angle is 12 degrees. Fig. 5(ef) shows the far-field scattering pattern of the 3D and 2D numerical simulations of the S ₃ encoding matrix metasurface for normal normal incident electromagnetic waves. At this time, the reflected beams are four beams that are symmetrical about the z axis, and the beam deflection angle is 36 degrees.

Fig. 6 is the three-dimensional far-field scattering pattern of the metasurface with coding matrix S ₄ at three different frequencies. Figure 6(a) is the three-dimensional far-field scattering pattern of the metasurface with coding matrix S4 at _11.5GHz ; Figure 6(b) is the _three -dimensional far-field scattering pattern of the metasurface with coding matrix S4 at 12GHz; Fig. 6(c) is the 3D far-field scattering pattern of the metasurface with encoding matrix S ₄ at 12.5 GHz. As shown in Figure 6(a), (b) and (c), the coded metasurfaces designed at 11.5GHz, 12GHz and 12.5GHz frequency points all exhibit good diffuse scattering effects for normal incident electromagnetic waves, effectively reducing the Radar cross section in the direction of mirror reflection.

Fig. 7 is a schematic diagram of the experimental test results of the two-dimensional far-field scattering pattern of the encoding metasurface with encoding matrices S ₁ and S ₄ . Figure 7(a) is the experimental test results of the two-dimensional far-field scattering pattern of the S ₁ coded metasurface at 12GHz frequency; Figure 7(b) is the two-dimensional far-field scattering pattern experiment of the S ₄ coded metasurface at 11.5GHz frequency Test results; Figure 7(c) is the experimental test result of the two-dimensional far-field scattering pattern of the S ₄ coded metasurface at 12GHz; Figure 7(d) is the two-dimensional far-field scattering of the S ₄ coded metasurface at 12.5GHz Directional pattern experimental test results. The experimental results effectively verify that the designed optically transparent coding metasurface can achieve abnormal reflection, diffuse scattering, and reduce the radar scattering cross-sectional area for normal incident electromagnetic waves.

Claims (8)

1. An optically transparent electromagnetic coding metamaterial basic unit applied to a microwave band, which is characterized in that: the electromagnetic coding metamaterial basic unit comprises a square Indium Tin Oxide (ITO) layer (1), a dielectric slab layer (2), an air layer (3), the dielectric slab layer (2) and a total reflection zero transmission layer (4) which are sequentially arranged.

2. The optically transparent electromagnetically encoded metamaterial unit cell for use in the microwave band as claimed in claim 1, wherein: the thickness of the dielectric plate layer (2) is 0.5-1.0mm, the dielectric constant is 4.5-4.8, the thickness of the air layer (3) is 2-3mm, and the loss tangent is 0.01-0.02.

3. A metamaterial employing the optically transparent electromagnetically encoded metamaterial unit cell of claim 1 or 2 for application in the microwave band, wherein: the metamaterial comprises more than one super subunit, wherein the super subunit is mainly composed of NxN basic units, and N is a non-zero positive integer.

4. The metamaterial for use in the microwave band as claimed in claim 3, wherein the metamaterial comprises a base unit of optically transparent electromagnetically encoded metamaterial: the basic unit has 2 basic unit structures; by adjusting the side length of the square indium tin oxide ITO layer (1) film, two digital state responses which correspond to two reflection phases and can be independently generated under the irradiation of normal incidence linear polarization electromagnetic waves can be obtained for each basic unit structure, 2 different-phase digital state codes are further obtained according to the two digital state responses, and the 2 different-phase digital state codes correspond to 2 basic unit structures.

5. The metamaterial for use in the microwave band as claimed in claim 3, wherein the metamaterial comprises a base unit of optically transparent electromagnetically encoded metamaterial: the two generated digital state responses are respectively '0' and '1', and the two digital state responses respectively correspond to two reflection phases of 0 degrees and 180 degrees; the 2 phase digital states are encoded as "0" and "1," which represent the reflected phase digital states, respectively, for a normal incident electromagnetic wave.

6. The metamaterial for use in the microwave band as claimed in claim 3, wherein the metamaterial comprises a base unit of optically transparent electromagnetically encoded metamaterial: the period length L of the basic unit is 5-7 mm.

7. The metamaterial for use in the microwave band optically transparent electromagnetically encoded metamaterial base units of claim 4, wherein: in the geometric parameters of the 2 basic unit structures, the side length of the square ITO layer of the '0' digital state coding unit is 2.7mm, and the side length of the square ITO layer of the '1 digital state' coding unit is 5.5 mm.

8. The metamaterial for use in the microwave band as claimed in claim 3, wherein the metamaterial comprises a base unit of optically transparent electromagnetically encoded metamaterial: the back surface of the dielectric plate layer (2) is covered with a layer of ITO film.