CN115173071A - Vortex wave generation structure based on multifunctional shared aperture super-surface and design method - Google Patents

Vortex wave generation structure based on multifunctional shared aperture super-surface and design method Download PDF

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CN115173071A
CN115173071A CN202210530266.1A CN202210530266A CN115173071A CN 115173071 A CN115173071 A CN 115173071A CN 202210530266 A CN202210530266 A CN 202210530266A CN 115173071 A CN115173071 A CN 115173071A
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subunit
phase
polarized
super
shared aperture
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姜玉莹
刘亮亮
李姝颖
顾长青
李茁
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Nanjing University of Aeronautics and Astronautics
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Nanjing University of Aeronautics and Astronautics
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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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/36—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith
    • H01Q1/38—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith formed by a conductive layer on an insulating support
    • 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
    • H01Q15/14—Reflecting surfaces; Equivalent structures
    • 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
    • H01Q15/24—Polarising devices; Polarisation filters 

Abstract

The invention discloses a vortex wave generation structure based on a multifunctional shared aperture super-surface and a design method, and relates to the technical field of novel artificial electromagnetic materials. Vortex waves of different modes working at different wide frequency bands and with different polarizations can be generated. The technical scheme of the invention is as follows: the vortex wave generating structure comprises a multifunctional shared aperture super-surface, the multifunctional shared aperture super-surface comprises a plurality of shared aperture basic unit structures, and the shared aperture basic unit structures sequentially comprise a top pattern layer, a middle medium layer and a bottom metal layer from top to bottom; the top pattern layer comprises a right-hand circular polarization subunit formed by embedding a hollow cross ring in a square opening resonance ring, a vertical polarization subunit in an I-shaped structure and a horizontal polarization subunit in an I-shaped structure. The whole design idea is novel, simple and feasible, and the structure of the scheme is stable and the working effect is good.

Description

Vortex wave generation structure based on multifunctional shared aperture super-surface and design method
Technical Field
The invention relates to the technical field of novel artificial electromagnetic materials, in particular to a vortex wave generation structure design based on a multifunctional shared aperture super-surface.
Background
As is well known, the development of the characteristics of the traditional electromagnetic wave, such as polarization, frequency, amplitude, phase, etc., in the aspect of improving the channel capacity has reached a threshold, and the spectrum utilization rate is difficult to further improve. Due to the inherent orthogonality and infinity of the orbital angular momentum, the method becomes a new physical parameter dimension for multiplexing and manipulating electromagnetic waves, and has great potential in the development of new-generation communication systems.
The metamaterial in a two-dimensional form, namely the artificial electromagnetic super surface has the characteristics of light weight, low section, simple manufacture and the like, and has electromagnetic properties which are difficult to reach by natural materials. By reasonably designing the parameters such as period, structure, thickness, material and the like of the super-surface basic unit, the free independent regulation and control of multiple polarized multiple frequency band electromagnetic wave phases under the same unit aperture can be realized. The basic units sharing the aperture are arranged and combined, and vortex wave generation, beam scanning, beam abnormal reflection, beam focusing, polarization conversion, RCS (radar cross section) reduction and the like can be realized in the field of electromagnetic waves.
In microwave millimeter wave band, earlier methods for realizing vortex wave include spiral phase plate, plane phase plate, parabolic antenna, etc., and have great limitation in manufacturing process and working bandwidth. In recent years, antenna arrays, cavity structures and super-surface structures have been used to generate vortex waves. The super-surface has great advantages in the aspect of combining the orbital angular momentum of the vortex wave with the traditional physical parameters. However, the research of multifunctional vortex waves based on super-surface mostly stays in generating dual-band and dual-polarized vortex waves, and multilayer technology or subarray technology is used, which may result in increased difficulty in preparation and low aperture efficiency. In addition, since the design difficulty of the multifunctional super-surface is to ensure that the coupling influence between the polarized subunits operating in various wide frequency bands is small, it is more difficult to realize multiple functions on a single-layer structure than a multi-layer structure. In summary, a single-layer multi-polarization multi-band reflective super-surface with shared aperture needs to be designed by a smart structure combination and space allocation method, so that independent phase regulation of different polarized reflected waves working in different wide frequency bands is realized.
Disclosure of Invention
Aiming at the problems, the invention provides a vortex wave generating structure and a design method based on a multifunctional shared aperture super-surface, which can realize the generation of vortex waves with different polarizations and different modes, working in different wide frequency bands, and finally can generate a single-layer reflection type super-surface of l =1 right-hand circularly polarized vortex wave, l = -1 vertical polarized vortex wave and l = -2 horizontal polarized vortex wave under the working frequencies of 7.15-9.07GHz, 14-17GHz and 21-25 GHz.
The technical scheme of the invention is as follows: the vortex wave generating structure comprises a multifunctional shared aperture super surface, the multifunctional shared aperture super surface comprises a plurality of shared aperture basic unit structures, and the shared aperture basic unit structures sequentially comprise a top pattern layer, a middle medium layer and a bottom metal layer from top to bottom, wherein the top pattern layer, the middle medium layer and the bottom metal layer are fixedly connected;
the middle dielectric layer and the bottom metal layer have the same period;
the top pattern layer comprises a right-hand circularly polarized subunit 3 formed by embedding a hollow cross ring 2 into a square opening resonance ring 1, a vertical polarized subunit 4 in an I-shaped structure and a horizontal polarized subunit 5 in an I-shaped structure, wherein the vertical polarized subunit 4 is perpendicular to the horizontal polarized subunit 5, and the two are positioned in the hollow cross ring 2.
Further, the vertical polarization subunit 4 has a width w y The horizontal polarizing subunit 5 is composed of a width w x Of a metal strip of (a), w y ＞w x 。
Further, the middle dielectric layer is made of a low-loss material with a relative dielectric constant of 2.2-2.65, and the metal of the bottom metal layer and the metal of the top pattern layer are made of a metal material with a reflectivity equal to 1 approximately.
Furthermore, the period of the bottom metal layer and the period of the middle medium layer are both 7mm, and the thickness of the center medium layer is 2mm; the bottom metal layer and the top metal pattern layer are both 5.8 × 10 in conductivity 7 S/M metal copper, and the dielectric layer is made of F4B with a relative dielectric constant of 2.65 and a loss tangent of 0.0009.
Further, the multifunctional shared aperture super-surface has an overall thickness of less than one tenth of the three polarization longest operating wavelengths.
The method comprises the following steps: the method is characterized in that three subunits capable of independently controlling right-hand circularly polarized waves, vertical polarized waves and horizontal polarized waves are designed, and a proper space distribution mode is adopted, so that the three polarized subunits are reasonably distributed in a shared aperture basic unit structure, the shared apertures of the three subunits are realized, and the shared aperture basic unit structure sequentially comprises a top metal pattern layer, a middle medium layer and a bottom metal layer from top to bottom;
step 1, firstly, according to the requirements of the generated reflected vortex wave on the amplitude and the phase of a basic unit structure, the dimension parameters of the structure of the right-hand circularly polarized subunit 3 are optimized by taking the rotation angle and the slotting width of a slotted long strip of the right-hand circularly polarized subunit 3 in the shared aperture basic unit structure as optimized variables, the rotation angle takes a value from-90 degrees to 90 degrees at an interval of 5 degrees, different rotation angles respectively correspond to the slotting widths required by fixed resonance frequency points, 37 basic states are obtained in total, and the reflection coefficients of the same polarization are all larger than 0.935 and the phase span is 347 degrees; the length of a central metal strip of a vertical polarization subunit 4 in a shared aperture basic unit structure is used as an optimized variable to optimize the size parameter of the vertical polarization subunit 4 structure, the phase interval 90 degrees required by a 2-bit coding super surface is used as an optimization element, 4 basic states are obtained in total, and the reflection coefficient of the same polarization is about equal to 1 and the phase interval is about equal to 90 degrees; the length of a central metal strip of a horizontal polarization subunit 5 in a shared aperture basic unit structure is used as an optimized variable to optimize the size parameter of the horizontal polarization subunit 5 structure, and the phase interval 90 degrees required by a 2-bit coded super surface is also used as an optimization element to obtain 4 basic states in total, so that the co-polarized reflection coefficient is equal to 1 and the phase interval is equal to 90 degrees;
step 2, the shared aperture basic unit structure obtained in step 1 has basic states of 37 × 4 × 4, wherein 37 structural states of the right-hand circular polarization subunit 3 correspond to 37 phase responses, and a phenomenon of a multiple relation between a unit rotation angle and the phase responses of a PB-like phase is realized, and 4 structural states of the vertical polarization subunit 4 and the horizontal polarization subunit 5 respectively correspond to 4 phase responses with a phase interval of about 90 degrees, so that a phase gradient required by a 2-bit coded super surface is realized;
deducing an electric field expression of vortex waves transmitted along the transmission direction of the electromagnetic waves according to a Helmholtz equation of a free space, and taking vortex wave beam phases of different modes reflected along the vertical direction with different polarizations as output phases of the super surface to obtain an output phase formula of each unit on the super surface;
then, an input phase of the super surface is obtained according to an incident field source, wherein incident right-hand circularly polarized waves are plane waves, and incident vertical polarized waves and incident horizontal polarized waves are spherical waves, so that a compensation phase required to be provided by each polarized subunit structure on the super surface is obtained;
and step 3: and establishing corresponding relations between the phases of all polarized sub-unit structures of the shared aperture basic unit structure and the compensation phases by applying an MATLAB program according to a compensation phase formula to obtain compensation phase forms required to be provided by different polarized sub-unit structures of the whole super surface, and further obtain the arrangement rules of all shared aperture basic units of the super surface generating different polarized different modal vortex waves. According to the principle of phase gradient super-surface, the structural state corresponding to the phase value closest to the required phase is selected from 37 phase states by the right-hand circular polarization subunit, the 90-degree phase gradient is used for vertical polarization subunit arrangement, the 90-degree phase gradient is used for horizontal polarization subunit arrangement, and the right-hand circular polarization subunit (3), the vertical polarization subunit (4) and the horizontal polarization subunit (5) are filled into each local position of the whole super-surface according to the required phase, so that the reflection type multifunctional vortex wave generation super-surface is obtained.
The shared aperture basic unit structure designed based on the method can simultaneously keep the polarization conversion efficiency of circular polarization above 90% in the relative bandwidth range of 23.67% of C and X wave bands (7.15-9.07 GHz), realize the reflection of the same polarization and realize the phase span of 347 degrees; making the vertical polarization reflection coefficient approximately equal to 1 in the relative bandwidth range of 19.35% of Ku band (14-17 GHz), realizing co-polarized reflection and realizing 2-bit digital coding super surface; making the horizontally polarized reflection coefficient approximately equal to 1 within 17.39% of the relative bandwidth of the K-band (21-25 GHz), achieves co-polarized reflection and achieves a 2-bit digitally encoded super-surface. By theoretical derivation of vortex wave compensation phases and association of corresponding phase responses of all sub-unit structures of a shared aperture unit, right-hand circularly polarized plane waves, vertical polarized spherical waves and horizontal polarized spherical waves are used as field sources of three kinds of polarization, and a single-layer reflection type super surface capable of generating the right-hand circularly polarized vortex waves l =1, the vertical polarized vortex waves l = -1 and the horizontal polarized vortex waves l = -2 under the working frequencies of 7.15-9.07GHz, 14-17GHz and 21-25GHz is designed. The proposed scheme is subjected to simulation design through full-wave simulation, and finally, the multifunctional vortex wave super-surface structure is subjected to experimental verification and is consistent with a simulation result.
On the whole, the single-layer reflection type super-surface can finally realize the generation of vortex waves with different modes and different polarizations, which work in different wide frequency bands, and finally can generate a right-handed circularly polarized vortex wave with the frequency of l =1, a vertically polarized vortex wave with the frequency of l =1 and a horizontally polarized vortex wave with the frequency of l = 2 under the working frequencies of 7.15-9.07GHz, 14-17GHz and 21-25 GHz. The integral design idea is novel and simple and easy to implement, the structure of the scheme is stable, the working effect is good, and the single-layer multi-polarization multi-band reflection type super surface with the shared aperture achieves the purpose of independent phase regulation and control of different polarization reflected waves working in different wide frequency bands through ingenious structural combination and space distribution.
Drawings
FIG. 1 is a side view of an embodiment of a super-surface shared aperture base unit for implementing multi-polarized multi-band multi-modal vortex waves;
FIG. 2 is a top view of the super-surface shared aperture basic unit for realizing the multi-polarization multi-band multi-mode vortex wave, which is marked with the parameters of a square open resonator ring structure;
FIG. 3 is a top view of the super-surface shared aperture basic unit for realizing the multi-polarized multi-band multi-mode vortex wave of the embodiment, which is marked with the structural parameters of a hollow cross ring;
FIG. 4 is a top view of an orthogonal-positioned I-shaped structural parameter of a super-surface shared aperture basic unit for realizing a multi-polarization multi-band multi-modal vortex wave of an embodiment;
wherein: 1-square open resonance ring, 2-hollow cross ring, 3-right-hand circular polarization subunit, 4-vertical polarization subunit, 5-horizontal polarization subunit; p is the periodic side length of the basic unit, h is the thickness of the basic unit dielectric plate, o is the outer edge length of the square open resonant ring, i is the inner edge length of the square open resonant ring, g is the slot width of the square open resonant ring, alpha is the rotation angle of the slot strip, and a o Is the length of the outer edge of the hollow cross ring in the vertical direction, a i Is the inner side length of the hollow cross ring in the vertical direction, b o Is the horizontal outer edge of the hollow cross-shaped ring is long, b i The inner side of the hollow cross ring in the horizontal direction is long; d is the distance of the vertical ring from the vertical (horizontal) polaroid subunit in the horizontal (vertical) direction y The length, w, of the upper and lower horizontal arms of the larger I-shaped structure y Is the width of a metal strip with a larger size I-shaped structure y Length of side, d, of central metal strip of larger dimension "I" shaped structure x The arm length, w, of the left and right vertical arms of the smaller dimension I-shaped structure x Is the width of a metal strip with a smaller size I-shaped structure x The length of the side of the central metal strip of the I-shaped structure with smaller size.
FIG. 5 shows performance results for the shared aperture elementary unit of an embodiment, where FIG. 5 (a) is the co-polarized reflection coefficient and phase for a right-hand circularly polarized subunit, FIG. 5 (b) is the co-polarized reflection coefficient and phase for a vertical polarized subunit, and FIG. 5 (c) is the co-polarized reflection coefficient and phase for a horizontal polarized subunit;
FIG. 6 is a super-surface final compensated phase distribution calculated in MATLAB generated by three polarized different modal vortex waves operating in different wide frequency bands for an implementation of an embodiment: right-hand circular polarization, vertical polarization and horizontal polarization are respectively performed from left to right;
FIG. 7 is a test sample for generating multi-polarized multi-band multi-mode vortex waves prepared by a printed circuit board process according to an embodiment;
fig. 8 is a phase and amplitude result of a multi-polarized multiband multi-modal vortex wave simulated and tested by the embodiment, fig. 8 (a) is a phase and amplitude result of a right-handed circularly polarized wave at a far-field distance from the super-surface when a right-handed circularly polarized wave of 8GHz is incident, fig. 8 (b) is a phase and amplitude result of a vertical polarized wave at a xoy plane at 450mm from the super-surface when a vertical polarized wave of 15GHz is incident, and fig. 8 (c) is a phase and amplitude result of a horizontal polarized wave at a xoy plane at 450mm from the super-surface when a horizontal polarized wave of 22GHz is incident.
Detailed Description
For the purpose of clearly explaining the technical features of the patent, the patent will be explained in detail by means of the following detailed description and the accompanying drawings.
In this embodiment: the vortex wave generating structure comprises a feed source and a multifunctional shared aperture super-surface, wherein the feed source generates vortex waves after being incident to the multifunctional shared aperture super-surface, and comprises right-hand circularly polarized plane waves, horizontal polarized spherical waves and vertical polarized spherical waves. The multifunctional shared aperture super-surface comprises a plurality of shared aperture basic unit structures, and the shared aperture basic unit structures sequentially comprise a top pattern layer, a middle medium layer and a bottom metal layer from top to bottom, wherein the top pattern layer, the middle medium layer and the bottom metal layer are fixedly connected;
the period p of the middle dielectric layer and the bottom metal layer of the shared aperture basic unit (figure 1) is 7mm, and the thickness h of the middle dielectric layer is 2mm; both the bottom metal layer and the top patterned layer have a conductivity of 5.8 × 10 7 S/M metal copper, the central dielectric layer is composed of F4B with the relative dielectric constant of 2.65 and the loss tangent of 0.0009;
the overall size of the multifunctional super-surface is 224mm × 224mm, and is composed of 32 × 32 shared aperture basic units distributed in an array.
Three subunits capable of independently controlling right-handed circularly polarized waves, vertical polarized waves and horizontal polarized waves are required to be designed, and a proper space distribution mode is adopted, so that three polarized subunits are reasonably distributed in a shared aperture basic unit structure, the shared aperture of the three subunits is realized, and the shared aperture basic unit structure sequentially comprises a top metal pattern layer, a middle medium layer and a bottom metal layer from top to bottom;
step 1, firstly, according to the requirements of the generated reflected vortex wave on the amplitude and phase of a basic unit structure, the size parameters of the structure of a right-hand circularly polarized subunit 3 are optimized by sharing the rotation angle and the slotting width of a slotted strip of the right-hand circularly polarized subunit 3 in the hole diameter basic unit structure as optimized variables, a slot with the slot width of g is formed on a square resonance ring by the slotted strip after rotating alpha, so that a square open resonance ring 1 is formed, the rotation angle is taken from-90 degrees to 90 degrees at intervals of 5 degrees, different rotation angles respectively correspond to the slotting widths required by fixed resonance frequency points, 37 basic states are obtained in total, and the reflection coefficient of the same polarization is larger than 0.935 and the phase span is 347 degrees; the length of a central metal strip of a vertical polarization subunit 4 in a shared aperture basic unit structure is used as an optimized variable to optimize the size parameter of the vertical polarization subunit 4 structure, the phase interval 90 degrees required by a 2-bit coding super surface is used as an optimization element, 4 basic states are obtained in total, and the reflection coefficient of the same polarization is approximately equal to 1 and the phase interval is approximately equal to 90 degrees; the length of a central metal strip of a horizontal polarization subunit 5 in a shared aperture basic unit structure is used as an optimized variable to optimize the size parameter of the horizontal polarization subunit 5 structure, and the phase interval 90 degrees required by a 2-bit coded super surface is also used as an optimization element to obtain 4 basic states in total, so that the co-polarized reflection coefficient is equal to 1 and the phase interval is equal to 90 degrees;
specifically, a shared aperture basic unit is designed on the principle that the coupling influence between circular polarization subunits and linear polarization subunits is small, and the circular polarization subunit structure is modeled, simulated and optimized in CST. The basic unit structure comprises a bottom metal layer, a middle medium layer and a top metal pattern layer, wherein the middle medium layer and the bottom metal layer have the same period, the top pattern layer is a square opening resonance ring 1 combined with a hollow cross ring 2 to serve as a right-handed circular polarization subunit 3, a larger-size I-shaped structure serves as a vertical polarization subunit 4, and a smaller-size I-shaped structure serves as a horizontal polarization subunit.
As shown in fig. 2, the outer ring side length o of the square opening resonance ring 1 in the right-hand circularly polarized subunit 3 is 6.4mm, the inner ring side length i is 6mm, the rotation angle α of the slotted strip is variable from-90 ° to 90 °, the slotted width g is variable from 1.3-2.35mm, and the two are optimized variables;
as shown in FIG. 3, the length a of the outer ring side of the hollow cross ring in the vertical direction o Is 5.6mm, the length of the inner circle side a i 5.2mm, outer ring side length b in the horizontal direction o Is 5.6mm, the length of the inner circle side b i Is 5.2mm;
as shown in fig. 4, the hollow cross-shaped ring includes a vertical ring having a distance d of 0.2mm from the vertical polarization subunit 4 in the horizontal direction, and a horizontal ring having a distance d of 0.2mm from the horizontal polarization subunit 5 in the vertical direction. Arm length d of upper and lower horizontal arms of vertical polarizing subunit 4 y Is 3mm, width w of the metal strip y 0.4mm, length l of the central metal strip y The variation range is 1.5-4.39mm, and is used as an optimized variable. Arm length d of right and left vertical arms of horizontal polarizing subunit 5 x Is 1.2mm, the width w of the metal strip x 0.2mm, center metal strip length l x The variation range is 0.5-4.76mm, and is used as an optimized variable;
step 2, the shared aperture basic unit structure obtained according to the step 1 has basic states of 37 × 4 × 4, wherein 37 structural states of the right-hand circularly polarized subunit 3 correspond to 37 phase responses, the phenomenon of the multiple relation between the unit rotation angle and the phase response of the similar PB phase is realized, and 4 structural states of the vertical polarized subunit 4 and the horizontal polarized subunit 5 respectively correspond to 4 phase responses with a phase interval of about 90 degrees, so that the phase gradient required by the 2-bit coded super surface is realized;
specifically, according to the amplitude and phase requirements needed by realization of vortex waves, in the CST optimization process, for the right-handed circular polarized subunit 3, the rotation angle and the slot width of the slotted strip in the square-opening resonant ring 1 are selected as optimization variables, wherein the phase regulation and control principle of the right-handed circular polarized subunit 3 is similar to the PB phase basic principle, but technically, the rotation angle of the slotted strip needs to be adjusted, the slot width is adjusted to keep the resonant frequency point unchanged, 37 basic states for realizing 347-degree phase span can be obtained through optimization, and the circular polarization conversion rate is larger than 90% in the frequency band range (C and X wave bands) of 7.15-9.07 GHz. For the vertical polarization subunit 4, the length of the central metal strip is selected as an optimization variable, so that the co-polarization reflection coefficient is approximately equal to 1 when vertical polarization waves enter in the frequency band range of 14-17GHz, 4 basic states with the phase span of 270 degrees are realized, and the phase gradient is 90 degrees. For the horizontal polarization subunit 5, the length of the central metal strip is selected as an optimization variable, so that the co-polarization reflection coefficient is ensured to be approximately equal to 1 when horizontal polarization waves are incident within the frequency range of 21-25GHz, 4 basic states with approximately 270-degree phase span are realized, and the phase gradient is approximately equal to 90 degrees.
According to the three principles, the rotation angle α and the slot width g of the slotted strip for obtaining 37 basic states of the right-handed circular polarization subunit 3 are respectively as follows: -90 °,2.35mm; -85 °,2.30879mm; -80 °,2.18317mm; -75 °, 1.99024mm; -70 °,1.95809mm; -65 °,1.87574mm; 60 degrees, 1.84752mm; -55 °,1.87999mm; -50 °,1.44415mm; -45 °,1.3mm; -40 °,1.44415mm; 35 °,1.6491mm; -30 °,1.90526mm; -25 °,1.98609mm; -20 °,1.88359mm; -15 °,1.8635mm; -10 °,1.92931mm; -5 °,1.96749mm;0 degrees and 2mm;5 degrees, 1.96749mm;10 degrees, 1.92931mm;15 degrees, 1.8635mm; 20 °,1.88359mm;25 degrees, 1.98609mm;30 degrees, 1.90526mm;35 degrees, 1.649mm;40 °,1.44415mm; 45 degrees, 1.3mm;50 degrees, 1.44415mm;55 degrees, 1.87999mm;60 degrees, 1.84752mm;65 degrees, 1.87574mm; 70 degrees, 1.95809mm;75 degrees, 1.95809mm;80 degrees, 2.18317mm;85 degrees and 2.30879mm;90 degrees, 2.35mm; the right-hand circular polarization reflection coefficients of the 37 fundamental states are all above 0.935, and the phase span can reach 347 ° (fig. 5 (a)). The length l of the central metal strip of the 4 basic states of the vertically polarized subelement 4 y Are respectively 1.5mm, 1.97mm and 2.1 mm6mm,2.78mm; the vertical polarization reflection coefficient of these 4 fundamental states is equal to about 1 and the phase separation is equal to about 90 degrees (fig. 5 (b)). Length l of central metal strip of 4 basic states of horizontal polarizing subunit 5 x Respectively 0.61mm,2.06mm,3.06mm and 4.76mm; the horizontally polarized reflection coefficients of these 4 fundamental states are equal to about 1 and the phase spacing is equal to about 90 degrees (fig. 5 (c));
deriving an electric field expression of the vortex wave propagating along the transmission direction of the electromagnetic wave according to a Helmholtz equation of free space:
Figure RE-GDA0003836358760000081
where l is the number of OAM modes,
Figure RE-GDA0003836358760000082
is the azimuth angle, k, of the element at coordinate position (x, y) relative to the origin 0 Is the free space wavenumber, E 0 Is a constant vector. Obtaining the input phase of the super surface according to the incident field source, wherein the incident right-hand circularly polarized wave is a plane wave, and the phase compensation is not needed, and the phase compensation formula of the obtained circularly polarized subunit on the super surface is as follows:
Figure BDA0003645922490000083
the incident vertical polarization and the horizontal polarization waves are spherical waves, and the phase compensation of the spherical waves is needed, so that the phase compensation formula of the two linearly polarized subunits on the super surface is obtained:
Figure BDA0003645922490000084
wherein
Figure BDA0003645922490000085
Is the position vector of the mth unit of the x-axis and the nth unit of the y-axis,
Figure BDA0003645922490000086
k represents the wave number in vacuum at the center frequency point, which is the feed antenna position vector.
Step 3, according to the compensation phase formulas (2) and (3), using an MATLAB program to establish a corresponding relationship between the phase and the compensation phase of each polarization subunit structure of the shared aperture basic unit structure, so as to obtain compensation phase forms respectively required to be provided by different polarization subunit structures of the whole super surface, and further obtain an arrangement rule (figure 6) of all shared aperture basic units of the super surface generating different polarization vortex waves in different modes, namely calculating alpha, g, l of each shared aperture basic unit in 32x32 shared aperture basic units according to the compensation phase formulas (2) and (3) in the MATLAB program y 、l x . And respectively filling the right-hand circular polarization subunit 3 (a structural state corresponding to a phase value closest to a required phase is selected from phase states in 37), the vertical polarization subunit 4 (a structural state according to a 90-degree phase gradient) and the horizontal polarization subunit 5 (a structural state according to a 90-degree phase gradient) into each local position of the integral super-surface according to the required phase according to the arrangement rules corresponding to the right-hand circular polarization, the vertical polarization and the horizontal polarization, so as to obtain the reflective multifunctional vortex wave generation super-surface.
Step 4, modeling and simulation in CST: performing combined modeling and simulation in CST according to a super surface compensation phase program obtained by MATLAB, determining that the simulation working frequency band of a right-hand circularly polarized part is 7.15-9.07GHz, the simulation working frequency band of a vertical polarization part is 14-17GHz, the simulation working frequency band of a horizontal polarization part is 21-25GHz, respectively selecting a right-hand circularly polarized plane wave, a vertical polarized spherical wave and a horizontal polarized spherical wave as field sources to perform simulation calculation, analyzing the electric field amplitude and the phase of a near field by using a spherical wave feed source at a distance of 100mm from the super surface, and setting sampling surfaces of vertical polarization and horizontal polarization on a plane of 200mm multiplied by 200mm with a distance of 450mm from the super surface;
step 5, as shown in fig. 7, preparing a sample by a PCB (printed Circuit Board) process, completing testing in a microwave darkroom, and observing the effect realized by a device; the test results of 8GHz right-hand circular polarization (fig. 8 (a)), simulation test results of 15GHz vertical polarization and 22GHz horizontal polarization (fig. 8 (b) and (c)) are obtained, and it can be known that the effects of the electric field amplitude and the phase are basically consistent, the right-hand circular polarization is a vortex wave phase effect of l =1 (counterclockwise single-arm helix), the vertical polarization is a vortex wave phase effect of l = -1 (clockwise single-arm helix), the horizontal polarization is a vortex wave phase effect of l = -2 (clockwise double-arm helix), and the effects are consistent with expectations, and the feasibility of the structure is verified;
in summary, the present invention performs a structural design for generating a multi-polarized multi-band multi-mode vortex wave based on a single-layer multi-polarized multi-band shared aperture basic unit, and can be better applied in the frequency diversity and polarization diversity expansion direction of a communication system based on orbital angular momentum.
While the invention has been described in terms of its preferred embodiments, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

Claims (5)

1. A vortex wave generation structure based on a multifunctional shared aperture super-surface is characterized by comprising the multifunctional shared aperture super-surface, wherein the multifunctional shared aperture super-surface comprises a plurality of shared aperture basic unit structures, and the shared aperture basic unit structures sequentially comprise a top pattern layer, a middle medium layer and a bottom metal layer from top to bottom;
the middle dielectric layer and the bottom metal layer have the same period;
the top pattern layer comprises a right-hand circularly polarized subunit (3) formed by embedding a hollow cross ring (2) into a square opening resonance ring (1), a vertical polarized subunit (4) in an I-shaped structure and a horizontal polarized subunit (5) in an I-shaped structure, wherein the vertical polarized subunit (4) is perpendicular to the horizontal polarized subunit (5), and the vertical polarized subunit and the horizontal polarized subunit are both positioned in the hollow cross ring (2).
2. The vortex wave generating structure based on multifunctional shared aperture super surface as claimed in claim 1, wherein the vertical polarization subunit (4) is composed of a width w y The horizontal polarising subunit (5) consists of a metal strip of width w x Of a metal strip of (a), w y ＞w x 。
3. The multifunctional shared-aperture super-surface-based vortex wave generation structure of claim 1, wherein the period of the bottom metal layer and the middle dielectric layer is 7mm, and the thickness of the middle dielectric layer is 2mm; the bottom metal layer and the top metal pattern layer are both 5.8 × 10 in conductivity 7 S/M metal copper, and the dielectric layer is made of F4B having a relative dielectric constant of 2.65 and a loss tangent of 0.0009.
4. The structure of claim 1, wherein the thickness of the multifunctional shared aperture super-surface is less than one tenth of the longest operating wavelength of the three polarizations.
5. A method for designing a multifunctional shared aperture super-surface as claimed in claim 1, characterized by comprising the following steps:
step 1, firstly, according to the requirements of the generated reflected vortex wave on the amplitude and the phase of a basic unit structure, the dimension parameters of the structure of the right-hand circularly polarized subunit (3) are optimized by taking the rotation angle and the slot width of a slotted strip of the right-hand circularly polarized subunit (3) in a shared aperture basic unit structure as optimized variables, the rotation angle is taken from-90 degrees to 90 degrees at an interval of 5 degrees, different rotation angles respectively correspond to the slotted widths required by fixed resonant frequency points, 37 basic states are obtained in total, and the reflection coefficients of the same polarization are all larger than 0.935 and the phase span is 347 degrees; the length of a central metal strip of a vertical polarization subunit (4) in a shared aperture basic unit structure is used as an optimization variable to optimize the size parameter of the vertical polarization subunit (4) structure, the phase interval 90 degrees required by a 2-bit coded super surface is used as an optimization element to obtain 4 basic states in total, and the reflection coefficient of the same polarization is approximately equal to 1 and the phase interval is approximately equal to 90 degrees; the method comprises the steps that the length of a central metal strip of a horizontal polarization subunit (5) in a shared aperture basic unit structure is used as an optimization variable to optimize the size parameter of the horizontal polarization subunit (5) structure, the phase interval 90 degrees required by a 2-bit coded super surface is also used as an optimization element to obtain 4 basic states in total, and the reflection coefficient of the same polarization is approximately equal to 1 and the phase interval is approximately equal to 90 degrees;
step 2, the shared aperture basic unit structure obtained according to the step 1 has basic states of 37 × 4 × 4, wherein 37 structural states of the right-hand circularly polarized subunit (3) correspond to 37 phase responses, the phenomenon of the multiple relation between the unit rotation angle and the phase responses of the similar PB phase is realized, and 4 structural states of the vertical polarized subunit (4) and the horizontal polarized subunit (5) respectively correspond to 4 phase responses with the phase interval of about 90 degrees, so that the phase gradient required by the 2-bit coded super surface is realized;
deducing an electric field expression of vortex waves transmitted along the transmission direction of the electromagnetic waves according to a Helmholtz equation of a free space, and taking vortex wave beam phases of different modes reflected along the vertical direction with different polarizations as output phases of the super surface to obtain an output phase formula of each unit on the super surface;
then, an input phase of the super surface is obtained according to an incident field source, wherein incident right-hand circularly polarized waves are plane waves, and incident vertical polarized waves and horizontal polarized waves are spherical waves, so that compensation phases required to be provided by each polarized subunit structure on the super surface are obtained;
and step 3: and establishing a corresponding relation between the phases of all polarized subunit structures of the shared aperture basic unit structure and the compensation phase by applying an MATLAB program according to a compensation phase formula to obtain compensation phase forms required to be provided by different polarized subunit structures of the whole super surface, and further obtain an arrangement rule of all shared aperture basic units of the super surface generating different polarized vortex waves in different modes. According to the principle of phase gradient super-surface, the structural state corresponding to the phase value closest to the required phase is selected from 37 phase states by the right-hand circularly polarized subunit, the 90-degree phase gradient is used for vertical polarized subunit arrangement, the 90-degree phase gradient is used for horizontal polarized subunit arrangement, and the right-hand circularly polarized subunit (3), the vertical polarized subunit (4) and the horizontal polarized subunit (5) are filled into each local position of the whole super-surface according to the required phase, so that the reflecting type multifunctional vortex wave generation super-surface is obtained.
CN202210530266.1A 2022-05-16 2022-05-16 Vortex wave generation structure based on multifunctional shared aperture super-surface and design method Pending CN115173071A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116111360A (en) * 2023-01-10 2023-05-12 西安电子科技大学 Design method of double circularly polarized orbital angular momentum independently controllable super-surface array

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116111360A (en) * 2023-01-10 2023-05-12 西安电子科技大学 Design method of double circularly polarized orbital angular momentum independently controllable super-surface array
CN116111360B (en) * 2023-01-10 2023-09-26 西安电子科技大学 Design method of double circularly polarized orbital angular momentum independently controllable super-surface array

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