Method for generating omnidirectional circularly polarized vortex electromagnetic wave
阅读说明：本技术 一种全向圆极化涡旋电磁波的产生方法 (Method for generating omnidirectional circularly polarized vortex electromagnetic wave ) 是由 衣建甲 李蝶 朱丽娜 刘晨晨 郭明涛 杨龙 于 2019-09-10 设计创作，主要内容包括：本发明提出了一种全向圆极化涡旋电磁波的产生方法,解决了现有技术中存在的全向涡旋电磁波增益较低、实现圆极化困难的技术问题。实现过程包括：设计圆环柱状超表面透镜组件的透镜形状；设置透镜组件参数；计算其期望涡旋电磁波相位分布、初始模型的金属层几何旋转角度分布；建立透镜组件初始模型和全波仿真；计算其汇聚相位分布及最终模型的金属层几何旋转角度分布；得到透镜组件最终模型,对其进行全波仿真验证。本发明将由透射单元结构周期排列组成的平面超表面透镜共形到圆柱表面上,构成一个圆环柱状的超表面透镜组件。本发明具有增益较高、圆极化纯度较高、馈电简单的优点,可用于通信领域。(The invention provides a method for generating omnidirectional circularly polarized vortex electromagnetic waves, which solves the technical problems of low gain of the omnidirectional vortex electromagnetic waves and difficulty in realizing circular polarization in the prior art. The implementation process comprises the following steps: designing the lens shape of the annular cylindrical super-surface lens component; setting lens assembly parameters; calculating the expected vortex electromagnetic wave phase distribution and the metal layer geometric rotation angle distribution of the initial model; establishing an initial model of a lens assembly and full-wave simulation; calculating the convergence phase distribution and the geometric rotation angle distribution of the metal layer of the final model; and obtaining a final model of the lens assembly, and performing full-wave simulation verification on the final model. The invention leads the plane super surface lens formed by the periodic arrangement of the transmission unit structures to be conformal on the cylindrical surface to form a circular ring cylindrical super surface lens component. The invention has the advantages of higher gain, higher circular polarization purity and simple feed, and can be used in the field of communication.)
1. A method for generating omnidirectional circularly polarized vortex electromagnetic waves is characterized in that: the method comprises the following steps:
(1) design of lens shape: the planar super surface obtained by periodically arranging specific transmission unit structures is conformal to a cylindrical surface with the circumference equal to the length of the planar super surface to form a circular cylindrical super surface lens assembly so as to realize phase regulation in a horizontal 360-degree omnidirectional range and convert omnidirectional circularly polarized electromagnetic waves generated by a feed source into omnidirectional circularly polarized vortex electromagnetic waves;
(2) setting parameters: overlapping the center of the annular cylindrical super-surface lens component and the center of the feed source, establishing a Cartesian rectangular coordinate system oxyz with the center, and setting a working frequency f, a transmission unit structure line number M, a transmission unit structure column number N, a unit period P of a transmission unit structure and an orbital angular momentum mode L; m, N, L are all integers;
(3) calculating the expected vortex electromagnetic wave phase distribution of the lens assembly: respectively calculating the phase of the expected vortex electromagnetic wave at the central position of the outer surface of each transmission unit structure according to the set orbital angular momentum mode and by combining a space phase formula of the vortex electromagnetic wave, traversing the whole, and further obtaining the phase distribution of the expected vortex electromagnetic wave on the outer surface of the annular cylindrical super-surface lens component;
(4) calculating the geometric rotation angle distribution of the metal layer of the initial model of the lens assembly: the phase on the initial model of the circular ring cylindrical super-surface lens assembly is expected vortex electromagnetic wave phase distribution, the geometric rotation angle of the metal layer in each transmission unit structure is respectively calculated by combining the mapping relation of the circularly polarized transmission phase of the transmission unit structure on the geometric rotation angle of the metal layer on the transmission unit structure, and the whole is traversed, so that the geometric rotation angle distribution of the metal layer on the outer surface of the initial model of the circular ring cylindrical super-surface lens assembly is obtained;
(5) establishing a lens assembly initial model and performing full-wave simulation: establishing an initial model of the circular ring cylindrical super-surface lens assembly according to the geometric rotation angle distribution of the metal layer on the outer surface of the initial model of the circular ring cylindrical super-surface lens assembly; performing full-wave simulation on the initial model of the annular cylindrical super-surface lens component to obtain the corresponding electric field distribution of the radiated electromagnetic waves;
(6) calculating a convergent phase distribution of the lens assembly: extracting a phase distribution of a circularly polarized component electric field on the surface of the initial model of the lens assembly from an electric field distribution of the radiated electromagnetic wave of the initial model of the lens assembly; taking the average value of the phase distribution of the circularly polarized component electric field on the surface of the transmission unit structure as the spatial phase delay of the transmission unit structure; m phase values corresponding to the transmission unit structures in each row form a phase curve, the curve is fitted by a quadratic function to obtain the quasi-convergence radius of the transmission unit structures in the corresponding row in the lens assembly, and the minimum value of all the quasi-convergence radii is used as the final convergence radius; according to a hyperbolic convergence phase formula, respectively calculating a convergence phase at the central position of the outer surface of each transmission unit structure according to the final convergence radius, traversing the whole, and further obtaining convergence phase distribution of the outer surface of the annular cylindrical super-surface lens component;
(7) calculating the geometric rotation angle distribution of the metal layer of the final model of the lens assembly: the total phase distribution on the final model of the annular cylindrical super-surface lens assembly is formed by the sum of the expected vortex electromagnetic wave phase distribution and the convergence phase distribution, the geometric rotation angle of the metal layer in each transmission unit structure is respectively calculated by combining the mapping relation of the circular polarization transmission phase of the corresponding transmission unit structure with respect to the rotation angle of the metal layer on the transmission unit structure, and the whole is traversed, so that the geometric rotation angle distribution of the metal layer on the outer surface of the final model of the annular cylindrical super-surface lens assembly is obtained;
(8) establishing a final model of the lens assembly and performing full-wave simulation verification: establishing a final model of the annular cylindrical super-surface lens assembly according to the geometric rotation angle distribution of the metal layer on the outer surface of the final model of the lens assembly; and performing full-wave simulation on the final model of the annular cylindrical super-surface lens component to obtain a near-field phase distribution diagram and a far-field directional diagram of the annular cylindrical super-surface lens component.
2. The method for generating an omnidirectional circularly polarized vortex electromagnetic wave according to claim 1, wherein: calculating the expected vortex electromagnetic wave phase distribution of the lens assembly in the step (3), wherein the expected vortex electromagnetic wave phase distribution of the outer surface of the annular cylindrical super-surface lens assembly is mathematically expressed as the expected vortex electromagnetic wave phase of the (m, n) th lens unit structureThe corresponding expression:
in the formula (x)mn,ymn,zmn) Is the coordinate position of the (m, n) th lens unit structure; l is an orbital angular momentum mode; m is the number of rows of the transmission unit structures in the annular cylindrical super-surface lens component, and M is 1,2, … and M; n is the number of the columns of the transmission unit structures in the annular cylindrical super-surface lens component, and N is 1,2, … and N.
3. The method of claim 1, wherein the electromagnetic wave comprises an omnidirectional circularly polarized vortex waveA method of generating, characterized by: calculating the geometric rotation angle distribution of the metal layer of the initial model of the lens assembly in the step (4), wherein the geometric rotation angle distribution of the metal layer on the outer surface of the initial model of the annular cylindrical super-surface lens assembly is expressed in a mathematical mode as the geometric rotation angle alpha of the metal layer in the (m, n) th transmission unit structuremnThe calculation formula of (a) is as follows:
。
4. the method for generating an omnidirectional circularly polarized vortex electromagnetic wave according to claim 1, wherein: calculating the convergent phase distribution of the lens assembly in the step (6), wherein the convergent phase distribution of the outer surface of the annular cylindrical super-surface lens assembly is mathematically expressed as a convergent phase at the center position of the (m, n) th transmission unit structureIs composed of
Wherein λ is the wavelength of the electromagnetic wave in free space; r is the convergence radius of the annular cylindrical super-surface lens component; m is 1,2, …, M; n is 1,2, …, N.
5. The method for generating an omnidirectional circularly polarized vortex electromagnetic wave according to claim 1, wherein: calculating the geometric rotation angle distribution of the metal layer of the final model of the lens assembly in the step (7), wherein the geometric rotation angle distribution of the metal layer on the outer surface of the final model of the annular cylindrical super-surface lens assembly is mathematically expressed as the geometric rotation angle alpha of the metal layer in the (m, n) th transmission unit structuremnThe calculation formula of' is as follows:
in the formula (I), the compound is shown in the specification,for the desired vortex electromagnetic wave phase of the (m, n) -th lens unit structure,the convergence phase of the (m, n) -th transmission cell structure.
Technical Field
The invention belongs to the technical field of communication, relates to a generation method of vortex electromagnetic waves, in particular to a generation method of omnidirectional circularly polarized vortex electromagnetic waves, and can be used in the technical field of wireless communication.
Background
The vortex electromagnetic wave is a special electromagnetic wave carrying orbital angular momentum, and the infinite orthogonal orbital angular momentum modes of the electromagnetic wave can obviously improve the channel capacity in the field of wireless communication. Due to the unique electromagnetic properties of the vortex wave, the central dark nucleus increases with the increase of the topological charge number, i.e., the divergence degree increases with the increase of the topological charge number. Aiming at the characteristic, the radiation elevation angle of the main lobe of the wave beam is folded by various convergence methods in the prior art so as to reduce the divergence degree of the wave beam. By the method for reducing the divergence angle and improving the inherent divergence characteristic of the vortex wave beam, the energy diffusion phenomenon caused by the increase of the radius of the annular wave beam along with the increase of the transmission distance of the vortex electromagnetic wave in wireless transmission is solved, and the remote transmission capability of the wave beam is indirectly improved.
As the wireless communication receiving device puts higher demands on the radiation angle range of the vortex wave beam, the demands on the radiation direction and the radiation plane of the beam are also diversified. The inherent non-orbital plane radiation direction of the vortex wave beam can not meet the requirement that wireless communication receiving equipment receives the vortex wave beam without dead angles, and the application of the vortex wave beam to the wireless communication technology neighborhood is greatly limited.
A method for generating omnidirectional vortex electromagnetic waves is disclosed in the published paper "reaction of Beam Steering Based on Plane Spiral ordered regular and regular magnetic Wave" (IEEE Transactions on Antennas and amplification 10.1109/TAP.2017.27862971558-22212018, 3 months) by Shilii, Chenliling et al. The method comprises the steps that firstly, a circular slot antenna generates vortex electromagnetic waves; then deflecting the beams through a resonant cavity between the circular slot antenna and the annular horn so that the vortex wave beams are distributed in a track plane in a concentrated manner; the two paths of eigenmode signals output by the feed source are used for carrying out beam superposition and beam energy focusing on the vortex electromagnetic waves with different eigenmode numbers, so that the vortex wave beams are radiated in a highly directional mode. The device has the advantages that the deflection of vortex wave beams is realized by combining the characteristic that the opening of the annular horn is positioned on the plane of the track and the resonant cavity between the circular slot antenna and the annular horn, so that the vortex wave beams are distributed in the plane of the track in a centralized manner.
The generation method has the following defects: although the vortex wave beams radiated by the hybrid coupler can be distributed in the track plane, the obtained omnidirectional vortex electromagnetic wave beam has lower gain due to the limitation of the resonant cavity; in addition, the omnidirectional vortex wave generated by the method is linearly polarized, but the polarization mode of the linear polarization has the defect of polarization mismatch in the communication field.
Disclosure of Invention
The invention aims to provide a method for generating omnidirectional circularly polarized vortex electromagnetic waves with higher gain, higher circularly polarized purity and simple feed aiming at the defects of the prior art.
The invention relates to a method for generating omnidirectional circularly polarized vortex electromagnetic waves, which is characterized by comprising the following steps: the method comprises the following steps:
(1) design of lens shape: the planar super surface obtained by periodically arranging specific transmission unit structures is conformal to a cylindrical surface with the circumference equal to the length of the planar super surface to form a circular cylindrical super surface lens assembly so as to realize phase regulation in a horizontal 360-degree omnidirectional range and convert omnidirectional circularly polarized electromagnetic waves generated by a feed source into omnidirectional circularly polarized vortex electromagnetic waves;
(2) setting parameters: overlapping the center of the annular cylindrical super-surface lens component and the center of the feed source, establishing a Cartesian rectangular coordinate system oxyz with the center, and setting a working frequency f, a transmission unit structure line number M, a transmission unit structure column number N, a unit period P of a transmission unit structure and an orbital angular momentum mode L; m, N, L are all integers;
(3) calculating the expected vortex electromagnetic wave phase distribution of the lens assembly: respectively calculating the phase of the expected vortex electromagnetic wave at the central position of the outer surface of each transmission unit structure according to the set orbital angular momentum mode and by combining a space phase formula of the vortex electromagnetic wave, traversing the whole, and further obtaining the phase distribution of the expected vortex electromagnetic wave on the outer surface of the annular cylindrical super-surface lens component;
(4) calculating the geometric rotation angle distribution of the metal layer of the initial model of the lens assembly: the phase on the initial model of the circular ring cylindrical super-surface lens assembly is expected vortex electromagnetic wave phase distribution, the geometric rotation angle of the metal layer in each transmission unit structure is respectively calculated by combining the mapping relation of the circularly polarized transmission phase of the transmission unit structure on the geometric rotation angle of the metal layer on the transmission unit structure, and the whole is traversed, so that the geometric rotation angle distribution of the metal layer on the outer surface of the initial model of the circular ring cylindrical super-surface lens assembly is obtained;
(5) establishing a lens assembly initial model and performing full-wave simulation: establishing an initial model of the circular ring cylindrical super-surface lens assembly according to the geometric rotation angle distribution of the metal layer on the outer surface of the initial model of the circular ring cylindrical super-surface lens assembly; performing full-wave simulation on the initial model of the annular cylindrical super-surface lens component to obtain the corresponding electric field distribution of the radiated electromagnetic waves;
(6) calculating a convergent phase distribution of the lens assembly: extracting a phase distribution of a circularly polarized component electric field on the surface of the initial model of the lens assembly from an electric field distribution of the radiated electromagnetic wave of the initial model of the lens assembly; taking the average value of the phase distribution of the circularly polarized component electric field on the surface of the transmission unit structure as the spatial phase delay of the transmission unit structure; m phase values corresponding to the transmission unit structures in each row form a phase curve, the curve is fitted by a quadratic function to obtain the quasi-convergence radius of the transmission unit structures in the corresponding row in the lens assembly, and the minimum value of all the quasi-convergence radii is used as the final convergence radius; according to a hyperbolic convergence phase formula, respectively calculating a convergence phase at the central position of the outer surface of each transmission unit structure according to the final convergence radius, traversing the whole, and further obtaining convergence phase distribution of the outer surface of the annular cylindrical super-surface lens component;
(7) calculating the geometric rotation angle distribution of the metal layer of the final model of the lens assembly: the total phase distribution on the final model of the annular cylindrical super-surface lens assembly is formed by the sum of the expected vortex electromagnetic wave phase distribution and the convergence phase distribution, the geometric rotation angle of the metal layer in each transmission unit structure is respectively calculated by combining the mapping relation of the circular polarization transmission phase of the corresponding transmission unit structure with respect to the rotation angle of the metal layer on the transmission unit structure, and the whole is traversed, so that the geometric rotation angle distribution of the metal layer on the outer surface of the final model of the annular cylindrical super-surface lens assembly is obtained;
(8) establishing a final model of the lens assembly and performing full-wave simulation verification: establishing a final model of the annular cylindrical super-surface lens assembly according to the geometric rotation angle distribution of the metal layer on the outer surface of the final model of the lens assembly; and performing full-wave simulation on the final model of the annular cylindrical super-surface lens component to obtain a near-field phase distribution diagram and a far-field directional diagram of the annular cylindrical super-surface lens component.
The invention overcomes the technical problems of lower gain of the omnidirectional vortex electromagnetic wave and difficult realization of circular polarization in the prior art.
Compared with the prior art, the invention has the following advantages:
the gain is higher: the annular cylindrical super-surface lens component is composed of a circularly polarized transmission unit structure, phase regulation and control are realized by adjusting the geometric rotation angle of a metal layer of the circularly polarized transmission unit structure, and the influence of the geometric rotation angle of the metal layer on the transmission coefficient of the unit structure is small, so that the omnidirectional circularly polarized vortex electromagnetic wave converted by the lens component can be ensured to have small non-roundness and high gain.
Has higher circular polarization purity: according to the invention, by adjusting the transmission coefficient and polarization conversion performance of the transmission unit structure in the annular cylindrical super-surface lens component, the omnidirectional circularly polarized vortex electromagnetic wave obtained by the lens component can be ensured to have higher circularly polarized purity.
Simple feed and low engineering cost: the feed source in the invention is an omnidirectional circularly polarized antenna which has wide application at present, and most of the antennas directly adopt a coaxial feed mode; the main substrate of the annular cylindrical super-surface lens component can be manufactured by 3D printing and other technologies, and the flexible substrate with the metal layers on the inner part and the outer part can be manufactured by FPC technology, so that the annular cylindrical super-surface lens component has the advantages of simple feeding and low engineering cost.
Drawings
FIG. 1 is a schematic diagram of the present invention, in which FIG. 1(a) is a schematic diagram of a lens assembly according to the present invention, and FIG. 1(b) is a schematic diagram of a coordinate position of the lens assembly and a feed source according to the present invention;
FIG. 2 is a schematic structural diagram of a structure of a transmission unit in the present invention, wherein FIG. 2(a) is a front view, FIG. 2(b) is a side view, and FIG. 2(c) is a top view;
fig. 3 is a graph showing left-handed to right-handed circular polarization transmission coefficients and transmission phases of the structure of the transmission unit according to the present invention, wherein fig. 3(a) is a graph showing the circular polarization transmission coefficients and fig. 3(b) is a graph showing the circular polarization transmission phases;
FIG. 4 is a flow chart of a method of generating an omnidirectional circularly polarized vortex wave in accordance with the present invention;
fig. 5 is a phase distribution diagram of an expected vortex electromagnetic wave of the annular cylindrical super-surface lens assembly obtained by the present invention, which is also a phase distribution diagram of an expected vortex electromagnetic wave of the annular cylindrical super-surface lens assembly in embodiment 7;
fig. 6 is a convergent phase distribution diagram of the annular cylindrical super-surface lens assembly obtained by the present invention, which is also a convergent phase distribution diagram of the annular cylindrical super-surface lens assembly in embodiment 7;
fig. 7 is a metal layer geometric rotation angle distribution diagram of a final model of the annular cylindrical super-surface lens assembly obtained by the present invention, which is also a metal layer geometric rotation angle distribution diagram of the final model of the annular cylindrical super-surface lens assembly in embodiment 7;
fig. 8 is an H-plane phase distribution diagram obtained by simulation of the final model of the annular cylindrical super-surface lens assembly obtained by the present invention, and is also an H-plane phase distribution diagram obtained by simulation of the final model of the annular cylindrical super-surface lens assembly in embodiment 7;
fig. 9 is a three-dimensional right-hand circularly polarized component far field diagram obtained by simulation of the final model of the annular cylindrical super-surface lens assembly obtained by the present invention, and is also a three-dimensional right-hand circularly polarized component far field diagram obtained by simulation of the final model of the annular cylindrical super-surface lens assembly in embodiment 7;
fig. 10 is an E-plane directional diagram obtained by simulation of the final model of the annular cylindrical super-surface lens assembly obtained by the present invention, which is also an E-plane directional diagram obtained by simulation of the final model of the annular cylindrical super-surface lens assembly in embodiment 7;
fig. 11 is an H-plane axial ratio diagram obtained by simulation of the final model of the annular cylindrical super-surface lens assembly obtained by the present invention, and is also an H-plane axial ratio diagram obtained by simulation of the final model of the annular cylindrical super-surface lens assembly in embodiment 7.
Detailed Description
The invention is described in detail below with reference to the following figures and specific examples: