CN110957584B - Novel method for improving broadband OAM directivity - Google Patents
Novel method for improving broadband OAM directivity Download PDFInfo
- Publication number
- CN110957584B CN110957584B CN201911310043.9A CN201911310043A CN110957584B CN 110957584 B CN110957584 B CN 110957584B CN 201911310043 A CN201911310043 A CN 201911310043A CN 110957584 B CN110957584 B CN 110957584B
- Authority
- CN
- China
- Prior art keywords
- transformation
- lens
- dimensional
- magnetic
- oam
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
- 238000000034 method Methods 0.000 title claims abstract description 33
- 239000000463 material Substances 0.000 claims abstract description 102
- 230000009466 transformation Effects 0.000 claims abstract description 71
- 239000007787 solid Substances 0.000 claims abstract description 25
- 230000000694 effects Effects 0.000 claims abstract description 11
- 238000004519 manufacturing process Methods 0.000 claims abstract description 8
- 230000011218 segmentation Effects 0.000 claims abstract description 3
- 230000003287 optical effect Effects 0.000 claims description 20
- 230000035699 permeability Effects 0.000 claims description 13
- 239000003989 dielectric material Substances 0.000 claims description 8
- 239000011159 matrix material Substances 0.000 claims description 5
- 230000001131 transforming effect Effects 0.000 claims description 5
- 238000004088 simulation Methods 0.000 claims description 4
- 230000003247 decreasing effect Effects 0.000 claims description 2
- 238000010586 diagram Methods 0.000 description 18
- 238000009826 distribution Methods 0.000 description 18
- 230000005684 electric field Effects 0.000 description 6
- 238000013461 design Methods 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 3
- 238000013500 data storage Methods 0.000 description 2
- 238000011426 transformation method Methods 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 239000011365 complex material Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000007726 management method Methods 0.000 description 1
- 238000012576 optical tweezer Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000012552 review Methods 0.000 description 1
- 238000012795 verification Methods 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q19/00—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic
- H01Q19/06—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic using refracting or diffracting devices, e.g. lens
-
- 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
- H01Q15/02—Refracting or diffracting devices, e.g. lens, prism
- H01Q15/08—Refracting or diffracting devices, e.g. lens, prism formed of solid dielectric material
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q21/00—Antenna arrays or systems
- H01Q21/06—Arrays of individually energised antenna units similarly polarised and spaced apart
- H01Q21/20—Arrays of individually energised antenna units similarly polarised and spaced apart the units being spaced along or adjacent to a curvilinear path
Landscapes
- Aerials With Secondary Devices (AREA)
Abstract
A new method for improving the directivity of broadband OAM relates to artificial electromagnetic devices. The method comprises the steps of respectively segmenting three-dimensional areas before and after transformation according to solid angles, and then respectively applying three-dimensional zooming transformation optics to corresponding sub-areas obtained by segmentation; designing a cylindrical convergent lens, converting the cylindrical convergent lens from a Mongolian yurt-shaped area in a virtual space, calculating material parameters of the cylindrical convergent lens in a physical space, and respectively simulating the convergent effect when a filling material of the convergent lens is magnetic and non-magnetic when the convergent lens works at a single frequency point; verifying the convergence effect of the convergence lens working on a wide frequency band; the designed convergent lens is provided with a feasible manufacturing method, the convergent lens is firstly divided, the divided material of each section is ensured to be uniform, then a medium material is filled, and the convergent characteristic is verified; by placing the converging lens above the antenna array generating the OAM beam, the broadband OAM directivity can be improved.
Description
Technical Field
The invention relates to the technical field of novel artificial electromagnetic devices, in particular to a novel method for improving broadband OAM directivity by utilizing conversion optics.
Background
The extensive research heat tide was caused by the Orbital Angular Momentum (OAM) of the non-planar phase front propagation direction of the laguerre-gaussian (L-G) beam, which was discovered by the netherlands physicist L-allen in the 90's 20 th century ([1] L-allen, m.w. beijersbergen, r.j.streew, and j.p.woerdman, "Orbital angular momentum of light and the transformation of laguerre gaussian laser models," Physical Review a Atomic Molecular & Optical Physics, vol.45, No.11, pp.8185-8189,1992.). In recent years, OAM has been widely developed in a variety of applications including particle control, Optical Tweezers, and Optical data storage etc. (2 D.G.Grier, "A recycling in Optical management," Nature, vol.424, No.6950, pp.810-816,2003; [3 M.Padgett and R.Bowman, "tweeters with a t wise," Nature Photonics, vol.5, No.6, pp.343-348,2011; [3] R.J.Voogd, M.Singh, S.F.Pereira, A.S.V.D.Nes, J.M.M.Brast, "The use of organic and mol of light beam for high-density Optical data storage," SPedition of Optical data, 5380. Ex 5380. vol.. Meanwhile, the OAM wave beam can double the channel capacity, and the OAM wave beam is taken as a new degree of freedom and is widely valued and researched in the field of wireless communication. However, OAM beams are not suitable for long distance transmission due to the diverging nature of the radio waves carrying OAM. Transform optics has been widely used to design various new types of electromagnetic and optical devices as an effective means of manipulating electromagnetic waves. The theoretical basis of transform optics is the form invariance of Maxwell's equations under coordinate transformation, and once the predetermined path is determined, the coordinate transformation and its Jacobian can be obtained by transforming optics, and then calculating the material parameters ([4] J.B.Pendry, D.Schurig, and D.R.Smith, "Controlling electronic fields," Science, vol.312, No.5781, pp.1780-1782,2006.). However, in the 3-D field, the materials obtained by using the conversion optical technology are usually required to be anisotropic and non-uniform, and the characteristics of the materials make the preparation of the device very difficult.
Disclosure of Invention
The invention aims to provide a novel method for improving the directivity of broadband OAM aiming at the problems that OAM wave beams in the prior art cannot be transmitted in a long distance and the like.
The invention comprises the following steps:
1) based on transformation optics, a three-dimensional zooming transformation optics method is provided, three-dimensional areas before and after transformation are respectively divided according to solid angles, and then three-dimensional zooming transformation optics are respectively applied to corresponding sub-areas obtained by division;
2) designing a cylindrical convergent lens according to the three-dimensional zooming transformation optical method, wherein the cylindrical convergent lens is transformed from a Mongolian yurt-shaped area in a virtual space, calculating material parameters of the cylindrical convergent lens in a physical space, and respectively simulating the convergent effect when a filling material of the convergent lens is magnetic and non-magnetic when the convergent lens works at a single-frequency point;
3) in order to further verify the broadband characteristic of the three-dimensional zooming and transforming optical method, the converging effect of the converging lens working on a broadband is verified, and simulation is carried out when the filling material of the converging lens is magnetic and non-magnetic respectively;
4) the designed convergent lens is provided with a feasible manufacturing method, the convergent lens is firstly divided, the divided materials of each section are ensured to be uniform, then the medium material is filled, and then the convergent characteristic of the convergent lens filled with the medium material is verified;
5) and (3) placing the convergent lens obtained in the step (4) above the antenna array generating the OAM wave beam, so that the broadband OAM directivity can be improved.
In step 1), the specific method for respectively applying three-dimensional scaling transformation optics to the corresponding sub-regions obtained by dividing the three-dimensional regions before and after transformation according to a solid angle may be:
(1) selecting a transformation origin (generally, the central point of a three-dimensional region) in transformation domains of a virtual space and a physical space respectively, then segmenting two regions before and after transformation according to solid angles based on the transformation origin, segmenting the solid angle surrounding the transformation origin in the 3-D transformation domain from 0 to 4 pi into a plurality of solid angles, respectively obtaining a plurality of sub-regions in the virtual space and the physical space, wherein the solid angles in the virtual space and the physical space are correspondingly equal;
(2) calculating radii from the segmentation origin to points on the surface of the 3-D transform domain, using RiA radius representing an ith sub-region in virtual space; accordingly, R'iIs the radius of the ith sub-region in physical space by applying a constant scale factor R'i/RiA Jacobian matrix of the material in the physical space can be obtained, and then the material parameters of the transform domain are obtained, and the obtained material is a magnetic isotropic material;
(3) the non-magnetic isotropic material is obtained by absorbing the permeability of the transformed material into the permittivity to keep the refractive index intact, i.e. the permeability is 1, and controlling the value of the refractive index by properly selecting the effective permittivity.
In step 4), the method for providing a feasible manufacturing method for the designed converging lens includes the specific steps of dividing the converging lens and ensuring that each divided section of material is uniform, then filling the material with a medium material, and then verifying the converging characteristics of the converging lens filled with the medium material, wherein the specific steps include: the relative dielectric constant of the material obtained by the three-dimensional zooming transformation optical method is a step function, so that the material of each segmented section can be ensured to be uniform by simply segmenting the convergent lens, the transformation domain of the convergent lens is uniformly segmented into a plurality of circular truncated cones by taking a transformation origin as a center in a solid angle descending manner, the circular truncated cones are hollow and have certain thickness, then, the wall of each circular truncated cone section is filled with dielectric materials in an order from outside to inside, the relative dielectric constant of the dielectric materials is uniformly increased from 1 to the maximum value calculated by the three-dimensional zooming transformation optical method section by section, each section of the filled materials are non-magnetic uniform isotropic materials, and the convergence characteristic of the convergent lens filled with the non-magnetic uniform isotropic materials is verified.
Compared with the prior art, the invention has the following outstanding advantages:
1. the invention provides a new method for improving the directivity of broadband OAM, which does not need to design a complex feed source for improving the directivity, only needs to design a cylindrical convergent lens, and places the convergent lens above an antenna array generating OAM beams for improving the directivity of broadband OAM so as to solve the problem that the OAM beams in the prior art cannot be transmitted remotely.
2. The convergent lens designed by utilizing the three-dimensional zooming transformation optics can be made of nonmagnetic uniform isotropic materials, and the material parameters are simple, so that the convergent lens is very easy to prepare and can be popularized to a great extent.
3. The three-dimensional zooming optical transformation method provided by the invention is simple and effective, is convenient and flexible to use, can be suitable for the design of artificial electromagnetic devices in any shapes, can obtain isotropic materials in physical space as long as transformation domains in virtual and physical spaces are limited and closed 3-D areas, and has wide application prospect.
Drawings
Fig. 1 illustrates a virtual space in a schematic diagram for the principles of three-dimensional scale-change optics.
Fig. 2 illustrates the physical space in a schematic diagram for the principles of three-dimensional zoom transform optics.
Fig. 3 is an i-th sub-region obtained by dividing a virtual space in a schematic diagram illustrating the principle of three-dimensional zoom transformation optics.
Fig. 4 is an i-th sub-region obtained by dividing a physical space in a schematic diagram illustrating the principle of three-dimensional zoom transformation optics.
Fig. 5 is a transform domain of a converging lens in virtual space.
Fig. 6 is a transform domain of a converging lens in physical space.
Fig. 7 is a three-dimensional structural view of a converging lens acting on a feed.
Fig. 8 is a structural diagram of an antenna array generating an OAM beam.
FIG. 9 is a three-dimensional distribution plot of the relative permittivity of a converging lens filled with a magnetically inhomogeneous isotropic material.
FIG. 10 is a cross-sectional plot of the relative permittivity of a converging lens filled with a magnetically inhomogeneous isotropic material.
Fig. 11 is a phase distribution diagram of an OAM beam generated by an antenna array in a direction parallel to the plane of the antenna array.
Fig. 12 is a normalized electric field profile of an OAM beam generated by an antenna array perpendicular to the plane of the antenna array.
Fig. 13 is a two-dimensional far-field gain diagram of an OAM beam generated by an antenna array.
Fig. 14 is a phase profile of an OAM beam generated by an antenna array parallel to the plane of the antenna array after the addition of magnetically non-uniform isotropic converging lenses.
Fig. 15 is a normalized electric field profile of an OAM beam generated by an antenna array perpendicular to the plane of the antenna array after the addition of magnetically non-uniform, isotropic converging lenses.
Fig. 16 is a two-dimensional far-field gain plot of OAM beams produced by an antenna array with the addition of a magnetically non-uniform, isotropic converging lens.
Fig. 17 is a normalized two-dimensional far-field gain plot of an OAM beam generated by an antenna array without the addition of a converging lens and with the addition of an isotropic converging lens for magnetic inhomogeneity.
Fig. 18 is an enlarged view of a part of fig. 17 within a black dashed line frame.
Fig. 19 is a two-dimensional far-field gain diagram of OAM beams generated by an antenna array without the addition of a converging lens and with the addition of an isotropic converging lens with magnetic inhomogeneity at an operating frequency of 6 GHz.
Fig. 20 is a two-dimensional far-field gain diagram of OAM beams generated by an antenna array without the addition of a converging lens and with the addition of an isotropic converging lens with magnetic inhomogeneity at an operating frequency of 8 GHz.
Fig. 21 is a two-dimensional far-field gain diagram of OAM beams generated by an antenna array without the addition of a converging lens and with the addition of an isotropic converging lens with magnetic inhomogeneity at an operating frequency of 10 GHz.
Fig. 22 is a two-dimensional far-field gain diagram of OAM beams generated by an antenna array without the addition of a converging lens and with the addition of an isotropic converging lens with magnetic inhomogeneity at an operating frequency of 12 GHz.
FIG. 23 is a three-dimensional distribution plot of the effective permittivity of a converging lens filled with a non-magnetic, non-uniform isotropic material.
FIG. 24 is a cross-sectional view of the effective permittivity distribution of a converging lens filled with a non-magnetic, non-uniform isotropic material.
Fig. 25 is a two-dimensional far-field gain diagram of OAM beams generated by an antenna array when a converging lens is filled with a magnetically non-uniform isotropic material and when the converging lens is filled with a non-magnetically non-uniform isotropic material at an operating frequency of 6 GHz.
Fig. 26 is a two-dimensional far-field gain diagram of OAM beams generated by an antenna array when a converging lens is filled with a magnetically non-uniform isotropic material and when the converging lens is filled with a non-magnetically non-uniform isotropic material at an operating frequency of 8 GHz.
Fig. 27 is a two-dimensional far-field gain diagram of OAM beams generated by an antenna array when a converging lens is filled with a magnetically non-uniform isotropic material and when the converging lens is filled with a non-magnetically non-uniform isotropic material at an operating frequency of 10 GHz.
Fig. 28 is a two-dimensional far-field gain diagram of OAM beams generated by an antenna array when a converging lens is filled with a magnetically non-uniform isotropic material and when the converging lens is filled with a non-magnetically non-uniform isotropic material at an operating frequency of 12 GHz.
Fig. 29 is a three-dimensional configuration diagram after the field of the condenser lens is divided into 40 circular truncated cones.
Fig. 30 is a three-dimensional configuration diagram of a hollow circular truncated cone into which the condensing lens is divided.
FIG. 31 is a three-dimensional distribution of relative permittivity after a converging lens is filled with material in a segmented manner.
Fig. 32 is a distribution diagram of the relative dielectric constant of a convergent lens filled with a material in a stepwise manner, perpendicular to the plane of an antenna array.
Fig. 33 is an enlarged view of a part within a black dashed frame in fig. 32.
Fig. 34 is a normalized electric field profile of an OAM beam produced by an antenna array at right angles to the plane of the antenna array when the converging lens is filled with a non-magnetic, uniform isotropic material.
Fig. 35 is a two-dimensional far-field gain plot of OAM beams produced by an antenna array when the converging lens is filled with a non-magnetic, uniform isotropic material.
Fig. 36 is a two-dimensional far-field gain plot of OAM beams generated by an antenna array when the converging lens is filled with a magnetically non-uniform isotropic material and when the converging lens is filled with a non-magnetic uniform isotropic material.
Detailed Description
The following examples will further illustrate the present invention with reference to the accompanying drawings. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention.
The embodiment of the invention comprises the following steps:
1) based on transformation optics, a three-dimensional zooming transformation optics method is provided, three-dimensional areas before and after transformation are respectively divided according to solid angles, and then three-dimensional zooming transformation optics are respectively applied to corresponding sub-areas obtained by division;
(1) selecting a transformation origin (generally, the central point of a three-dimensional region) in transformation domains of a virtual space and a physical space respectively, then segmenting two regions before and after transformation according to solid angles based on the transformation origin, segmenting the solid angle surrounding the transformation origin in the 3-D transformation domain from 0 to 4 pi into a plurality of solid angles, respectively obtaining a plurality of sub-regions in the virtual space and the physical space, wherein the solid angles in the virtual space and the physical space are correspondingly equal;
(2) computing slave segmentationRadius of origin to point on surface of 3-D transform domain, with RiA radius representing an ith sub-region in virtual space; accordingly, R'iIs the radius of the ith sub-region in physical space by applying a constant scale factor R'i/RiA Jacobian matrix of the material in the physical space can be obtained, and then the material parameters of the transform domain are obtained, and the obtained material is a magnetic isotropic material;
(3) the non-magnetic isotropic material is obtained by absorbing the permeability of the transformed material into the permittivity to keep the refractive index intact, i.e. the permeability is 1, and controlling the value of the refractive index by properly selecting the effective permittivity.
2) Designing a cylindrical convergent lens according to the three-dimensional zooming transformation optical method, wherein the cylindrical convergent lens is transformed from a Mongolian yurt-shaped area in a virtual space, calculating material parameters of the cylindrical convergent lens in a physical space, and respectively simulating the convergent effect when a filling material of the convergent lens is magnetic and non-magnetic when the convergent lens works at a single-frequency point;
3) in order to further verify the broadband characteristic of the three-dimensional zooming and transforming optical method, the converging effect of the converging lens working on a broadband is verified, and simulation is carried out when the filling material of the converging lens is magnetic and non-magnetic respectively;
4) the designed converging lens is provided with a feasible manufacturing method, and since the relative dielectric constant of the material obtained by the three-dimensional zooming optical transformation method is a step function, it is possible to ensure that the material of each segment divided is uniform by simple division of the converging lens, the transformation domain of the convergent lens is uniformly divided into a plurality of round tables by taking the transformation origin as the center and in a solid angle descending manner, the round tables are hollow and have certain thickness, then, filling dielectric materials in the wall of each section of the circular truncated cone in the sequence from outside to inside, wherein the relative dielectric constant of the dielectric materials is uniformly increased from 1 to the inside section by section to the maximum value calculated by the three-dimensional scaling transformation optical method, the filled materials of each section are all non-magnetic uniform isotropic materials, and verifying the convergence characteristics of the converging lens filled with the non-magnetic uniform isotropic material;
5) and (3) placing the convergent lens obtained in the step (4) above the antenna array generating the OAM wave beam, so that the broadband OAM directivity can be improved.
Specific examples are given below.
The embodiment first proposes a three-dimensional scaling transformation optics (3-D STO) method based on transformation optics, and the specific implementation manner of the three-dimensional scaling transformation optics is as follows:
the theoretical basis for transform optics is the form invariance of maxwell's equations under coordinate transformation, once the appropriate transformation (x', y ', z') is determined to be f (x, y, z), the electromagnetic wave can be steered to follow a predetermined path. The spatial variables (x, y, z) and (x ', y ', z ') represent coordinates in virtual space and physical space, respectively. The relationship of the transformation medium between the virtual space and the physical space is:
and
wherein the ratio of epsilon, mu,
the permittivity in the virtual space, the permeability in the virtual space, the tensor of permittivity in the physical space, and the tensor of permeability in the physical space are respectively expressed. J is the jacobian matrix of the coordinate transformation, defined as:
considering that the medium in the virtual space is air, i.e., epsilon ═ mu ═ 1, equations (1) and (2) can be rewritten as:
for the purpose of the general transformation in general,
and
are generally non-uniform and anisotropic. To implement and fabricate devices designed by conversion optics, efforts are generally made in two respects: one is to develop techniques for manufacturing complex materials and the other is to explore new ways in which the properties of the materials can be simplified, and the work of the present invention belongs to the second aspect.
Without loss of generality, it is assumed that the transform domains in both virtual and physical space are finite and closed 3-D regions, as shown in fig. 1 and 2. First, the origin of the transformation between the virtual space and the physical space is determined and denoted as O and O', respectively. Secondly, by splitting the solid angle around the transformation origin in the 3-D transformation domain in virtual space from 0 DEG to 4 pi into N solid angles omegaiI ═ 1,2, …, N, yielding N subregions, where:
as shown in FIG. 2, the 3-D transform domain in physical space is also divided into equal parts to obtain Ω'iI is 1,2, …, N, wherein
Thus, N sub-regions may be obtained in the transformed regions in virtual and physical space, respectively, as shown in FIGS. 3 and 4, with the i-th parts in virtual and physical space being denoted O-A, respectivelyiBiCiDiAnd O '-A'iB'iC'iD'iThe solid angle accordingly satisfies Ωi＝Ω'iI is 1,2, …, N. Next, the radius from the origin to a point on the surface of the 3-D transform domain may be calculated, as shown in FIGS. 3 and 4. SiFrom O to S for points on the surface of the ith sub-region in virtual spaceiIs given by RiIs represented by, i.e., RiRepresenting the radius of the ith sub-region in virtual space. Accordingly, R'iIs the radius of the ith sub-region in physical space. According to equation (3), by applying a constant scaling factor R'i/RiThe jacobian matrix J is transformed into:
thus, the vertebral body O-AiBiCiDiIs transformed into a vertebral body O '-A'iB'iC'iD'iFrom equation (4) and equation (7), the following formula is obtained;
because of the radius RiAnd R'iAre all positive values, equation (8) indicates that the material in the physical domain is isotropic and
and
positive values. In physical space, the refractive index can be expressed as
The refractive index integrity is maintained by absorbing the permeability of the transformed material into the permittivity, i.e. permeability is 1, and the refractive index value is controlled by appropriately selecting the effective permittivity, which is then:
thus, a non-magnetic isotropic material can be obtained. Furthermore, since the effective dielectric constant obtained by this method is a step function, it is possible to ensure that the material in each segment is a uniform material by simple division. This new method is named three-dimensional scaling transformation optics (3-D STO).
A cylindrical condenser lens is designed using three-dimensional zoom transform optics, and is placed above an antenna array generating an OAM beam to improve the directivity of broadband OAM. And (3) simulating by adopting a finite element method, wherein the used simulation platform is COMSOL multi-physical field simulation software.
The transform domains of the designed converging lens in virtual space and physical space are shown in fig. 5 and 6, respectively, where point O and point O' represent the transform origin in virtual space and physical space, respectively. And (3) transforming the Mongolian yurt-shaped area consisting of the cone (1) and the cylinder (2) in the virtual space into the cylinder (2) filled with the medium in the physical space by using three-dimensional scaling transformation optics, wherein the medium material of a transformation domain in the virtual space is air, and thus calculating the material parameters of the cylindrical area. The cylindrical area filled by the calculated material was the designed converging lens with a radius W of 21.6 cm and a height H of 9.6 cm. In the virtual space, the included angle between the cone (1) and the cylinder (2) is 25 °, and therefore the height of the cone (1) located above is W tan (25 °)/2, where θ is the beam divergence angle of the OAM wave generated by the antenna array (3). A 3-D structure of a condensing lens applied to an antenna array is shown in fig. 7, an antenna array (3) as a feed source is composed of 8 patch antenna elements arranged in a circle, an OAM beam is generated by controlling a port phase of each radiation element, and the structure of the antenna array is shown in fig. 8.
First, simulate
In the case where the filling material of the condensing lens is magnetically inhomogeneousA homogeneous isotropic material. As can be seen from equation (8), of the converging lens
And
in the range of 1 to 1.525, which
The three-dimensional distribution and the cross-sectional orthogonal distribution are shown in fig. 9 and 10, respectively. When the antenna array has a topological charge of l +1, the convergence effect of the convergence lens on the OAM wave beam at the frequency f of 10GHz is verified. Fig. 11 to 13 are respectively a phase distribution of an OAM beam generated by the antenna array in parallel to the plane of the antenna array, a normalized electric field distribution in perpendicular to the plane of the antenna array, and a two-dimensional far field gain without adding a converging lens. Fig. 14-16 are phase distributions of OAM beams generated by an antenna array parallel to the plane of the antenna array, normalized electric field distributions perpendicular to the plane of the antenna array, and two-dimensional far-field gains, respectively, when a converging lens is added. The two-dimensional far-field gain was normalized for both cases as shown in fig. 17, where the dashed line represents no converging lens added and the solid line represents the converging lens added. For a clearer view, the part inside the black dashed box in fig. 17 is enlarged as shown in fig. 18. As can be seen from fig. 11 and 14, the addition of the converging lens does not affect the phase of the OAM beam. As can be seen from fig. 18, by adding the converging lens, the divergence angle of the OAM beam can be reduced from the original 25 ° to 8 °, and therefore, the converging lens designed by the embodiment of the present invention can significantly improve the directivity of the OAM beam.
To further verify the broadband characteristics of the 3-D STO, the convergence effect of the analog converging lens on OAM beams at frequencies of 6GHz,8GHz,10GHz, and 12GHz is simulated, and the two-dimensional far-field gains are shown in fig. 19 to 22, respectively, where the dotted line represents no converging lens added, and the solid line represents the addition of a converging lens. When the converging lens works at 6GHz,8GHz,10GHz and 12GHz, the far-field gains of the main lobe of the OAM wave beam are respectively increased by 5.5dB,5.9dB,6.6dB and 7dB, so that the converging lens also has good converging characteristics on broadband OAM. In particular, when the operating frequency is 10GHz, the main lobe gain of the OAM beam is 6.677dB when no converging lens is added, and 13.31dB after the converging lens is added.
The converging effect of the converging lens at a permeability of 1, i.e. the filling material is a non-magnetic non-uniform isotropic material, is then simulated by absorbing the permeability of the transformed material into the permittivity to keep the refractive index intact. From equation (9), the effective dielectric constant of the condensing lens
The range is 1-2.326, and the three-dimensional distribution and the orthogonal tangent distribution are shown in FIGS. 23 and 24, respectively. When the converging lens operates at 6GHz,8GHz,10GHz and 12GHz, the two-dimensional far-field gains are respectively shown in FIGS. 25-28, wherein the dotted line represents the addition of a magnetic converging lens and the solid line represents the addition of a non-magnetic converging lens. It can be seen that by absorbing the permeability of the transformed material into the permittivity to maintain the refractive index intact, the result is also expected when the medium of the converging lens is non-magnetic. In particular, the main lobe gain of the OAM beam after adding the non-magnetic converging lens is 13.18dB when the operating frequency is 10 GHz.
Finally, a feasible manufacturing method is provided for the converging lens, and verification is carried out when the working frequency is 10 GHz. Since the relative permittivity obtained by the method of 3-D STO is a step function, it is possible to ensure that the material of each divided segment is uniform by simply dividing the converging lens. Here, the transform domain of the condenser lens is uniformly divided into 40 circular truncated cones with the transform origin as the center and the solid angle decreasing progressively, and the outer 39 circular truncated cones are all hollow and have a certain thickness, as shown in fig. 29. For a clearer illustration, the shape of the hollow truncated cone is enlarged as shown in fig. 30. Then, the wall of each segment of the truncated cone is filled with dielectric materials from outside to inside, the relative dielectric constant of the dielectric materials is increased from 1, each segment is increased by 0.034 compared with the previous segment, and the relative dielectric constant is increased to 2.326 in the innermost layer. The three-dimensional distribution of the relative dielectric constant of the convergent lens after filling the material and the distribution perpendicular to the plane of the antenna array are shown in fig. 31 and 32, respectively, and in order to observe the distribution of the filling material more clearly, the part inside the black dashed frame in fig. 32 is enlarged as shown in fig. 33, that is, in the wall of the 40-segment hollow truncated cone, the filled material is a non-magnetic uniform isotropic material. The normalized electric field distribution and the two-dimensional far-field gain of the OAM beam at this time in the direction perpendicular to the plane of the antenna array are shown in fig. 34 and 35, respectively. To demonstrate the effectiveness of this fabrication method, the two-dimensional far field gain was paired for both cases as shown in fig. 36, where the dashed line represents the condenser lens filled with a magnetically non-uniform isotropic material and the solid line represents the condenser lens filled with a non-magnetic uniform isotropic material. The main lobe gain of the OAM beam after the addition of the non-magnetic, uniformly isotropic converging lens is 13.69 dB.
Experiments show that the invention can effectively improve the directivity of broadband OAM and solve the problem that OAM wave beams cannot be transmitted in a long distance.
Claims (1)
1. A new method for improving the directivity of broadband OAM is characterized by comprising the following steps:
1) based on transformation optics, a three-dimensional zooming transformation optics method is provided, three-dimensional areas before and after transformation are respectively divided according to solid angles, and then three-dimensional zooming transformation optics are respectively applied to corresponding sub-areas obtained by division;
the specific method for respectively applying three-dimensional zooming transformation optics to the corresponding subregions obtained by dividing the three-dimensional regions before and after transformation according to solid angles comprises the following steps:
(1) selecting a transformation origin in transformation domains of a virtual space and a physical space respectively, then segmenting two regions before and after transformation according to solid angles based on the transformation origin, segmenting the solid angle surrounding the transformation origin in a 3-D transformation domain from 0 to 4 pi into a plurality of solid angles, and respectively obtaining a plurality of sub-regions in the virtual space and the physical space, wherein the solid angles in the virtual space and the physical space are correspondingly equal;
(2) calculating radii from the segmentation origin to points on the surface of the 3-D transform domain, using RiA radius representing an ith sub-region in virtual space; accordingly, R'iIs the radius of the ith sub-region in physical space by applying a constant scale factor R'i/RiObtaining a Jacobian matrix of the material in the physical space, and further obtaining material parameters of a transform domain, wherein the obtained material is a magnetic isotropic material;
(3) the magnetic permeability of the transformed material is absorbed into the dielectric constant to keep the refractive index complete, namely the magnetic permeability is 1, and the refractive index value is controlled by properly selecting the effective dielectric constant to obtain the nonmagnetic isotropic material;
2) designing a cylindrical convergent lens according to the three-dimensional zooming transformation optical method, wherein the cylindrical convergent lens is transformed from a Mongolian yurt-shaped area in a virtual space, calculating material parameters of the cylindrical convergent lens in a physical space, and respectively simulating the convergent effect when a filling material of the convergent lens is magnetic and non-magnetic when the convergent lens works at a single-frequency point;
3) in order to further verify the broadband characteristic of the three-dimensional zooming and transforming optical method, the converging effect of the converging lens working on a broadband is verified, and simulation is carried out when the filling material of the converging lens is magnetic and non-magnetic respectively;
4) a feasible manufacturing method is provided for the designed convergent lens, the convergent lens is firstly divided, the divided materials of each section are ensured to be uniform, then a medium material is filled, and then the convergent characteristics of the convergent lens filled with the medium material are verified, and the specific method comprises the following steps: the relative dielectric constant of the material obtained by the three-dimensional zooming transformation optical method is a step function, so that the convergence lens is simply divided to ensure that each divided section of the material is uniform, a transformation original point is taken as the center, the transformation domain of the convergence lens is uniformly divided into a plurality of circular truncated cones in a solid angle decreasing mode, the circular truncated cones are hollow and have certain thickness, then, the wall of each section of the circular truncated cone is filled with dielectric materials from outside to inside, the relative dielectric constant of the dielectric materials is uniformly increased from 1 to the maximum value calculated by the three-dimensional zooming transformation optical method section by section, each section of the filled materials are non-magnetic uniform isotropic materials, and the convergence characteristic of the convergence lens filled with the non-magnetic uniform isotropic materials is verified;
5) and (3) placing the convergent lens obtained in the step (4) above the antenna array generating the OAM wave beam, namely improving the directivity of the broadband OAM.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201911310043.9A CN110957584B (en) | 2019-12-18 | 2019-12-18 | Novel method for improving broadband OAM directivity |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201911310043.9A CN110957584B (en) | 2019-12-18 | 2019-12-18 | Novel method for improving broadband OAM directivity |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN110957584A CN110957584A (en) | 2020-04-03 |
| CN110957584B true CN110957584B (en) | 2021-02-19 |
Family
ID=69982469
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201911310043.9A Expired - Fee Related CN110957584B (en) | 2019-12-18 | 2019-12-18 | Novel method for improving broadband OAM directivity |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN110957584B (en) |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107258040A (en) * | 2014-12-15 | 2017-10-17 | 蒙彼利埃大学 | Laser aid with the light beam for carrying controlled paths angular momentum |
| CN108281800A (en) * | 2017-12-15 | 2018-07-13 | 西安电子科技大学 | A kind of generating means of vortex electromagnetic wave |
| CN108539425A (en) * | 2018-03-21 | 2018-09-14 | 西安电子科技大学 | The design method of orbital angular momentum vortex electromagnetic wave generating device |
| CN109101727A (en) * | 2018-08-13 | 2018-12-28 | 厦门大学 | A kind of conformal antenna design method based on transform optics |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8983303B2 (en) * | 2004-08-04 | 2015-03-17 | The United States Of America As Represented By The Secretary Of The Army | Quantum based information transfer system and method |
| CN109103604B (en) * | 2018-07-19 | 2020-12-29 | 电子科技大学 | High-gain wide-angle scanning lens antenna based on step medium |
-
2019
- 2019-12-18 CN CN201911310043.9A patent/CN110957584B/en not_active Expired - Fee Related
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107258040A (en) * | 2014-12-15 | 2017-10-17 | 蒙彼利埃大学 | Laser aid with the light beam for carrying controlled paths angular momentum |
| CN108281800A (en) * | 2017-12-15 | 2018-07-13 | 西安电子科技大学 | A kind of generating means of vortex electromagnetic wave |
| CN108539425A (en) * | 2018-03-21 | 2018-09-14 | 西安电子科技大学 | The design method of orbital angular momentum vortex electromagnetic wave generating device |
| CN109101727A (en) * | 2018-08-13 | 2018-12-28 | 厦门大学 | A kind of conformal antenna design method based on transform optics |
Non-Patent Citations (3)
| Title |
|---|
| "A Method to Design Arbitrary-Way Multimodal OAM Generator";Chunhui Zhu et al;《IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS》;20200602;第987-991页 * |
| "A New Strategy for Transformation Optics With Index-Only Media";Chunhui Zhu et al;《IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION》;20190703;第4626-4635页 * |
| 《基于几何光学变换的OAM光束高效测量及其应用技术研究》;冯志康;《中国优秀硕士学位论文全文数据库》;20191215;第I136-156页 * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN110957584A (en) | 2020-04-03 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Yi et al. | 3D printed broadband transformation optics based all-dielectric microwave lenses | |
| Lam et al. | Steering phased array antenna beams to the horizon using a buckyball NIM lens | |
| Yi et al. | Restoring in-phase emissions from non-planar radiating elements using a transformation optics based lens | |
| You et al. | A new method to analyze broadband antenna-radome interactions in time-domain | |
| CN104112901A (en) | Conformal antenna on holographic artificial impedance surface | |
| CN108446504B (en) | Near-field array antenna directional pattern comprehensive method based on convex optimization | |
| CN110957584B (en) | Novel method for improving broadband OAM directivity | |
| WO2016012745A1 (en) | Lens design method and radiation source substrate | |
| CN108270081A (en) | The method of constitutive parameter based on transform optics structure Meta Materials | |
| Zang et al. | A bi-dimensional compressed Luneburg lens antenna for miniaturization based on transformation optics | |
| Yi et al. | A metamaterial lens based on transformation optics for horizontal radiation of OAM vortex waves | |
| CN103928763A (en) | Multi-beam antenna based on transformation optics | |
| Yu et al. | Transformation of different kinds of electromagnetic waves using metamaterials | |
| Jiang et al. | Spatial transformation-enabled electromagnetic devices: from radio frequencies to optical wavelengths | |
| CN109101727B (en) | Conformal antenna design method based on transformation optics | |
| Mola et al. | Design of a broadband right-angled bend using transformation optics | |
| Zhu et al. | The scaling transformation optics with isotropic medium | |
| Han et al. | Parameter design of invisible anti-cloak based on nonlinear transformation | |
| CN110854517A (en) | Reflector array antenna design method based on diffraction-free focusing theory | |
| Tichit et al. | Novel antenna concepts via coordinate transformation | |
| Yang et al. | A new method to analyze the EM wave propagation characteristics in the hypersonic sheath | |
| Shi et al. | Omnidirectional radiation lens design of vortex beam carrying orbital angular momentum based on spatial transformation | |
| Whiting et al. | Reflectarray Feeds Augmented With Size-Reducing GRIN Lenses for Improved Power Handling and Aperture Efficiency | |
| Yi et al. | Application of Transformation Optics and 3D Printing Technology in Vortex Wave Generation | |
| McGuirk | Electromagnetic field control and optimization using metamaterials |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20210219 |