CN108808257B - Refractive index controllable super surface - Google Patents
Refractive index controllable super surface Download PDFInfo
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- CN108808257B CN108808257B CN201810416438.6A CN201810416438A CN108808257B CN 108808257 B CN108808257 B CN 108808257B CN 201810416438 A CN201810416438 A CN 201810416438A CN 108808257 B CN108808257 B CN 108808257B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
- H01Q15/0006—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices
- H01Q15/0086—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices said selective devices having materials with a synthesized negative refractive index, e.g. metamaterials or left-handed materials
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Abstract
The invention provides a refractive index controllable super surface, which comprises a first dielectric layer (1) and a porous parallel plate waveguide (5); the porous parallel plate waveguide (5) comprises a porous metal layer (2) and a second dielectric layer (3); the first dielectric layer (1), the porous metal layer (2) and the second dielectric layer (3) are sequentially arranged in the thickness extending direction; the porous metal layer (2) comprises basic units (6) with holes, and a plurality of basic units (6) with holes are integrally formed or fixedly connected. When the method is used for fitting the occasion of rapid change of the refractive index, the step value of the refractive index can be smaller by adopting the hole-shaped basic unit with the variable size; thereby enabling the size-variable perforated base unit proposed by the present invention to better fit the required rapidly-varying refractive index.
Description
Technical Field
The invention relates to the field of metamaterials, in particular to a refractive index controllable super surface.
Background
With the development of metamaterial technology, metamaterials are increasingly applied to control equivalent refractive indexes, so that the propagation direction of electromagnetic waves is controlled. Graded index profiles are required in many microwave lenses (e.g., planar luneberg lenses, maxwell fish-eye lenses, eaton lenses, etc.). Compared with the traditional method of realizing gradient refractive index by using multiple layers of materials with different refractive indexes, the metamaterial provides a new implementation mode for realizing the lens.
The existing methods for realizing the gradual change of the refractive index mainly include: multiple layers of materials of different refractive indices; a non-uniformly perforated dielectric slab; a dielectric plate with variable thickness is inserted into the parallel plate waveguide, and the distance between the upper and lower parallel plates is uniformly changed (the article 'fan-beam millimeter wave antenna designed based on cylindrical luneberg lens' published in the journal of "IEEE antenna and transmission" by wu xi dong et al in 2007 summarizes the waveguide structure capable of realizing variable refractive index in detail); the method realizes that the refractive index can be changed according to requirements to a certain extent, but provides higher requirements for materials or processing precision, and limits the precision and application range of the method. In order to improve the control precision of the refractive index and reduce the processing difficulty, the control of the refractive index of the super surface is provided.
The basic principle of realizing the gradual change of the refractive index by the super surface is to realize the change of local equivalent refractive index by changing the geometric dimension of the small electric unit, and the common structure of controlling the refractive index by the super surface is to insert a super surface layer in the parallel plate waveguide to change the boundary condition so that the equivalent refractive index of the parallel plate waveguide is controllable. Such a super-surface structure allows for precise control of the refractive index, since the electrical small cells of the super-surface can be made small. However, this method of changing the boundary condition usually works in TM wave or TE wave mode, and therefore, the working bandwidth is limited.
Disclosure of Invention
In view of the deficiencies in the prior art, it is an object of the present invention to provide a refractive index controllable meta-surface.
The refractive index controllable super surface provided by the invention comprises a first dielectric layer and a porous parallel plate waveguide; the porous parallel plate waveguide comprises a porous metal layer and a second dielectric layer;
the first dielectric layer, the porous metal layer and the second dielectric layer are sequentially arranged in the thickness extension direction;
the porous metal layer comprises a basic unit with holes, and a plurality of basic units with holes are integrally formed or fixedly connected.
Preferably, the base unit is provided with a circular opening; when the size of the hole is changed, the hole spacing formed between the circular holes on the two adjacent basic units with the holes is kept equal;
the inner space of the circular opening forms a first propagation unit, and the solid parts of the basic units with holes except the circular opening form a second propagation unit.
Preferably, the first dielectric layer comprises a first dielectric plate or a first air layer.
Preferably, the second dielectric layer comprises a second dielectric plate or a second air layer.
Preferably, the inner diameter of the circular opening is less than or equal to one tenth of the wavelength of the refracted electromagnetic wave.
Preferably, the dielectric constant of the first dielectric layer is greater than or equal to the dielectric constant of the second dielectric layer.
Preferably, the dielectric constant of the first dielectric layer is 1 or more and 10.2 or less.
Preferably, the porous parallel plate waveguide further comprises a floor layer; the first dielectric layer, the porous metal layer, the second dielectric layer and the floor layer are sequentially arranged.
Compared with the prior art, the invention has the following beneficial effects:
1. the refractive index control mode provided by the invention has a simple structure, can be processed and manufactured by using a standard printed circuit process, and is suitable for batch production.
2. The structure provided by the invention can realize the gradual change of the refractive index from the minimum value a to the maximum value b, a depends on the dielectric constant of the second dielectric layer, the minimum value a can be 1, the variable range b-a is slightly different along with the difference of the dielectric constants of the upper and lower dielectric layers and the difference of the heights of the porous parallel plate waveguides, and the variable range of the refractive index can be flexibly controlled by changing the parameters.
3. The super surface provided by the invention can realize gradual change of the refractive index with smaller step value, and the refractive index with different sizes can be realized by changing the size of the inside of a basic unit without changing the size of the basic unit used by a common super surface; the size of the basic unit with the holes of the invention is changed along with the size of the holes; therefore, the temperature of the molten metal is controlled,
4. when the unit is used for fitting the occasion of rapid change of the refractive index, the refractive index stepping value can be smaller by adopting the unit with the hole basic unit with the variable size; therefore, the temperature of the molten metal is controlled,
5. the unit with the changeable size of the basic unit with holes can be better fit to the needed continuous changing refractive index.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
FIG. 1 is a schematic diagram of a refractive index controllable super-surface structure when the second dielectric layer is an air layer;
FIG. 2 is a schematic diagram of a refractive index controllable super-surface cross section and its electric field distribution;
FIG. 3 is a schematic diagram of upper metal vias in a parallel plate waveguide; in the figure rhThe radius of the round opening is shown, and g is the hole distance;
FIG. 4 is a graph showing the change in equivalent refractive index corresponding to the size of the hole when the dielectric constant of the first dielectric layer is changed from 1 to 10.2; in the figure, Re is the real part of the refractive index, neffIn order to be an equivalent refractive index,ris the dielectric constant of the first dielectric layer.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the spirit of the invention. All falling within the scope of the present invention.
In the description of the present invention, it is to be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention.
As shown in FIG. 1 and FIG. 2, the refractive index controllable super-surface provided by the present invention comprises a first dielectric layer 1 and a porous parallel plate waveguide 5; the porous parallel plate waveguide 5 comprises a porous metal layer 2, a second dielectric layer 3 and a floor layer 4; the first dielectric layer 1, the porous metal layer 2, the second dielectric layer 3 and the floor layer 4 are sequentially arranged in the thickness extending direction; the porous metal layer 2 comprises a perforated base unit 6, and a plurality of perforated base units 6 are integrally formed or fixedly connected.
The basic unit 6 with the holes is provided with a circular opening; the hole spacing formed between the circular holes on two adjacent basic cells 6 with holes is equal, as shown in fig. 3, the internal space of the circular hole forms a first propagation unit (corresponding to unit a), and the solid part of the basic cell 6 with holes except the circular hole forms a second propagation unit (corresponding to unit B). Because the circular holes have rotational symmetry and have equal delay effect on electromagnetic waves in any direction, the upper surface of the porous parallel plate waveguide 5, namely the porous metal layer 2, is uniformly provided with the circular holes. When all the holes are uniform in size and uniformly arranged, the multi-hole parallel plate waveguide 5 can be regarded as one having an equivalent refractive index of neffOf the homogeneous material. When a gradient refractive index profile is required, the size of the circular holes is changed while keeping the hole-to-hole spacing constant, thereby changing the filling ratio of the perforated base unit 6 to change the equivalent refractive index of the perforated base unit 6. It is to be noted that here the hole pitch is kept constant as the size of the circular holes varies so that the size of the holed base unit 6 varies with the size of the circular holes. The larger the size of the circular hole, the larger the filling ratio and the larger the equivalent refractive index. Particularly, in the actual gradient refractive index design, the size of the circular hole can be selected according to the required refractive index, so that the required gradient refractive index is obtained, and the electromagnetic wave is regulated and controlled.
The invention is applied to the occasions needing the graded refractive index, such as microwave lenses, energy focusing and the like. The equivalent refractive index is improved by opening a hole on the upper surface of the porous parallel plate waveguide 5 to change the current path, the equivalent refractive index is further improved by placing the first dielectric layer 1 on the porous parallel plate waveguide 5, and the processing difficulty is reduced at the same time, so that the method can be realized by using a standard printed circuit board process. In practical application, any one or more of the following parts are processed by adopting a standard PCB process: between the first dielectric plate and the multi-aperture parallel plate waveguide 5; the integral structure of the multi-aperture parallel plate waveguide 5.
Preferably, the first dielectric layer 1 includes a first dielectric plate or a first air layer. Preferably, the second dielectric layer 3 includes a second dielectric plate or a second air layer. As shown in fig. 2, the electric field propagates mostly inside the multi-aperture parallel plate waveguide 5, but a part enters the first dielectric plate. Therefore, the equivalent dielectric constant is further improved. Here, taking the second dielectric layer 3 as an air layer as an example, verification is performed to calculate the refractive index corresponding to different sizes of the circular hole by simulating the S parameter of the super surface. Fig. 4 shows the equivalent refractive index as a function of the radius of the circular hole for dielectric constants of 1, 2.2, 3.48, 6.15 and 10.2 for the first dielectric layer 1. It can be seen from the figure that: 1. for the same kind of first dielectric slab, the larger the radius of the round hole of the porous metal layer 2 is, the larger the equivalent refractive index is; 2. for different first dielectric layers 1, the sizes of the round holes of the porous metal layer 2 are the same, the higher the dielectric constant of the first dielectric layer 1 is, the larger the equivalent refractive index is; 3. the higher the dielectric constant of the first dielectric layer 1, the larger the maximum equivalent refractive index achievable. As shown in fig. 4, when the first dielectric layer 1 is an air layer, the maximum equivalent refractive index achievable is about 1.4; the maximum equivalent refractive index achievable with a dielectric constant of 6.15 for the first dielectric layer 1 is about 2.
The working principle is as follows:
as shown in FIGS. 1 and 2, the opening of a hole in the upper surface of the porous parallel plate waveguide 5, wherein the diameter of the hole is smaller than or approximately one-tenth of a wavelength, controls the surface current distribution of the porous parallel plate waveguide 5 so that the path length of the electromagnetic field propagating in the porous parallel plate waveguide 5 is increased. Secondly, the first medium layer 1 is arranged on the upper surface of the porous parallel plate waveguide 5, so that the equivalent refractive index can be further improved under the condition that the size of the pores is not changed. FIG. 2 shows the electric field profile perpendicular to the propagation direction of the electromagnetic wave, from which it can be seen that although most of the electric field remains confined within the porous parallel plate waveguide 5, a portion of the electric field enters the first dielectric layer 1, and the first dielectric layer 1 typically has a higher dielectric constant than the second dielectric layer 3. Therefore, the refractive index is further improved. Meanwhile, the first dielectric plate is arranged on the upper surface of the porous parallel plate waveguide 5, so that the processing difficulty can be reduced. The refractive index controllable super-surface proposed by the present invention can be processed using standard printed board technology. As can be seen from the refractive index profile corresponding to the hole radius of fig. 4, the equivalent refractive index can be conveniently controlled by controlling only the hole radius. And the rate of change of the refractive index with the hole radius can be controlled by changing the dielectric constant of the first dielectric layer 1, and the maximum attainable refractive index can also be controlled.
The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes and modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.
Claims (7)
1. A refractive index controllable super-surface comprising a first dielectric layer (1) and a porous parallel plate waveguide (5); the porous parallel plate waveguide (5) comprises a porous metal layer (2), a second dielectric layer (3) and a floor layer (4); the first dielectric layer (1), the porous metal layer (2), the second dielectric layer (3) and the floor layer (4) are sequentially arranged in the thickness extending direction; the porous metal layer (2) comprises basic units (6) with holes, and a plurality of basic units (6) with holes are integrally formed or fixedly connected;
the hole spacing formed between the circular holes on two adjacent basic units (6) with holes is equal, when the basic units are used for fitting the occasion of gradual change of the refractive index, the hole size of the basic units (6) with holes is changed, the hole spacing is not changed, and the basic units with holes with variable periods are formed.
2. A refractive index controllable super surface according to claim 1, characterized in that the holed elementary units (6) are provided with circular openings; the hole spacing formed between the circular holes on the two adjacent basic units (6) with holes is equal; the inner space of the circular opening forms a first transmission unit, and the solid parts of the basic unit (6) with holes except the circular opening form a second transmission unit.
3. The refractive index controllable super surface according to claim 1, wherein the first dielectric layer (1) comprises a first dielectric sheet or a first layer of air.
4. The refractive index controllable super surface according to claim 1, wherein the second dielectric layer (3) comprises a second dielectric sheet or a second layer of air.
5. The index-controllable metasurface of claim 1, wherein an inner diameter of the circular opening is equal to or less than one tenth of a wavelength of an electromagnetic wave to be refracted.
6. The refractive index controllable meta-surface according to claim 1, characterized in that the dielectric constant of the first dielectric layer (1) is equal to or greater than the dielectric constant of the second dielectric layer (3).
7. The refractive index controllable meta-surface according to claim 1, wherein the first dielectric layer (1) has a dielectric constant of 1 or more and 10.2 or less.
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| CN112103662B (en) * | 2019-06-17 | 2022-03-01 | Oppo广东移动通信有限公司 | Lens antenna module and electronic equipment |
| CN114296155B (en) * | 2021-12-02 | 2023-02-07 | 华中科技大学 | Wide-spectrum optical zoom system based on double-layer medium super-surface |
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| JP6514657B2 (en) * | 2015-03-11 | 2019-05-15 | 富士フイルム株式会社 | Antireflection optical member |
| CN106042515B (en) * | 2016-05-18 | 2017-11-21 | 中国人民解放军国防科学技术大学 | A kind of high temperature resistant radar absorbing of sandwich and preparation method thereof |
| JP2018046395A (en) * | 2016-09-14 | 2018-03-22 | 浜松ホトニクス株式会社 | Metasurface |
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| CN103094699A (en) * | 2011-10-31 | 2013-05-08 | 深圳光启高等理工研究院 | Lens antenna based on metamaterial |
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