Dual-polarization multiplexing microwave perfect vortex metasurface and construction method thereof

Abstract

The invention discloses a dual-polarization multiplexing microwave perfect vortex metasurface and a construction method thereof, and the metasurface comprises a substrate which is of a regular polyhedron structure and has a certain thickness. The floor is arranged on the lower surface of the substrate. The patch is arranged on the upper surface of the substrate and comprises a cross-shaped structure which is orthogonally arranged in the center of the substrate and long-strip patches which are arranged on the four sides of the cross-shaped structure, and the four long-strip patches are not in contact with one another; the four vertexes of the cross-shaped patch are provided with short-strip patches perpendicular to the direction of the cross-shaped patch. The microwave perfect vortex is used for orbital angular momentum multiplexing communication, so that the divergence problem of traditional vortex waves can be effectively relieved, concentrated distribution of electromagnetic energy near an annular area with a fixed size on a receiving plane is achieved, the design of a receiving antenna is simplified, the receiving efficiency and the space utilization rate of the antenna are improved, and the cost is reduced. And the generation and multiplexing of the microwave perfect vortex are realized.

Description

Technical Field

[0001] The present invention relates to the field of electromagnetic functional materials, and in particular to a dual-polarization multiplexed microwave perfect vortex metasurface and a construction method thereof. Background Art

[0002] In recent years, with the development of science and technology and the changes in production and lifestyle, human society's demand for communication has increased day by day. Although countries around the world are entering the 5G or even B5G era, a series of technologies such as massive MIMO and non-orthogonal multiple access have greatly improved resource utilization and expanded the capacity of communication systems. However, with the gradual exhaustion of traditional space, time, code, and frequency resources, the existing communication system will face unprecedented pressure. Taking frequency resources as an example, since high-frequency bands contain rich bandwidth resources, people are increasingly inclined to expand channel capacity by increasing carrier frequency. However, the inherent physical properties of high-frequency electromagnetic waves, especially terahertz waves and visible light, such as large spatial loss, poor diffraction ability, and significant dispersion, have brought huge challenges to the further development of wireless communication technology. If new available resources can be found in addition to traditional space, time, code, and frequency resources, the communication capacity can be improved on the basis of the existing frequency bands, thereby alleviating the current predicament of tight communication resources. Against this background, people have found that vortex electromagnetic waves carrying orbital angular momentum can be used to achieve the above goals.

[0003] The angular momentum carried by electromagnetic waves can be divided into spin angular momentum and orbital angular momentum. Spin angular momentum is used to characterize the polarization mode of electromagnetic waves, while orbital angular momentum is used to characterize the spatial phase distribution of electromagnetic waves. According to electromagnetic theory, the spatial phase distribution of vortex waves carrying orbital angular momentum can be described by the term exp(ilθ), where l represents the topological charge, which determines the magnitude of the orbital angular momentum, and θ represents the rotation azimuth. For vortex waves propagating in free space, the phase distribution of their propagation cross section presents a spiral shape with a central singularity. Orbital angular momentum was first observed to exist in spiral phase light beams in the 1990s. Subsequent studies have further found that the magnitude of orbital angular momentum that a single photon can carry is (here represents the reduced Planck constant), and the wavefront phase distribution of the vortex beam carrying different orbital angular momentum has good orthogonality. These indicate that compared with the spin angular momentum with only two degrees of freedom, orbital angular momentum is more suitable for use as a new type of communication resource.

[0004] At present, researchers have explored communication schemes based on zero-order Laguerre-Gaussian vortex beams (including generation, transmission, reception, etc.) through a lot of research, and have completed experimental verification. However, the inherent defect of this beam is that the orbital angular momentum it carries will affect the size of the beam radius. As the topological charge increases, the beam radius will become larger and larger. This phenomenon brings great trouble to the design of receiving antennas, making it difficult to simultaneously receive signals of different orbital angular momentum modes through fixed-size antennas, and the space utilization rate is low. The use of perfect vortices can effectively solve this problem.

[0005] A perfect vortex beam is a special form of electromagnetic wave. Ideally, a perfect vortex beam appears as a bright ring carrying a vortex phase in a certain area, and its radius remains constant, regardless of the orbital angular momentum it carries. Under non-ideal conditions, the radius of the perfect vortex can also be kept basically the same through parameter design. The existence of a perfect vortex was first discovered in 2013. One of the important reasons for proposing this concept was to solve the problem of efficient coupling of multiple orbital angular momentum mode vortex waves to optical fibers. So far, research on perfect vortices has almost entirely focused on the optical or terahertz fields. If it is extended to the microwave field, it can be used to solve the aforementioned problem of vortex wave divergence and simplify the design of receiving antennas. In addition, the traditional design of perfect vortex generating devices is mostly based on complex optical equipment, which is bulky and single in function. Compared with these solutions, the perfect vortex antenna designed using metasurfaces has better integration and flexibility, and its practical application value is significant. By designing the size and arrangement of the surface units, the amplitude, phase, polarization mode and other characteristics of the incident electromagnetic wave can be arbitrarily controlled to generate a perfect vortex. In the field of microwave orbital angular momentum multiplexing communications, currently, no study has proposed a design scheme for a perfect vortex metasurface for single-board coaxial multiplexing in the microwave segment.

[0006] Due to the increasing demand for wireless communications, microwave orbital angular momentum multiplexing technology has become a research hotspot in the communication field. Microwave vortex electromagnetic waves carrying orbital angular momentum can be used for wireless communications, and metasurfaces can be used to generate perfect microwave vortices for communication. However, how to use metasurface units to achieve a wide range of reflected wave phase control performance in a wide frequency band to generate perfect microwave vortices for single-board coaxial multiplexing is a problem that technicians in this field urgently need to solve. Summary of the invention

[0007] In order to solve the above technical problems, the present invention provides a dual-polarization multiplexed microwave perfect vortex metasurface and a construction method thereof, which utilizes metasurface units to achieve a wide range of reflected wave phase control performance in a wide frequency band to generate a single-board coaxial multiplexed perfect microwave vortex.

[0008] The object of the present invention is achieved through the following technical solutions: a dual-polarization multiplexed microwave perfect vortex metasurface, comprising:

[0009] The substrate is a regular polyhedron structure with a certain thickness.

[0010] The floor is arranged on the lower surface of the substrate.

[0011] The patch is arranged on the upper surface of the substrate, including a cross-shaped structure arranged orthogonally in the center of the substrate and long strip patches arranged on the four sides of the cross-shaped structure, and the four long strip patches are not in contact with each other; the four vertices of the cross-shaped patch are provided with short strip patches perpendicular to the direction.

[0012] Preferably, the substrate is a regular hexahedron structure and is made of F4B material.

[0013] Preferably, the floor and the patch are both made of metal.

[0014] In addition to providing a dual-polarization multiplexed microwave perfect vortex metasurface, the present invention further provides a method for constructing the above-mentioned microwave perfect vortex metasurface, and the specific steps are as follows:

[0015] Step 1: Design the size specifications of the metasurface unit according to the wavelength data, and use the modeling software to model the metasurface;

[0016] Step 2: Use four dual-polarized electromagnetic waves from different directions to calculate the metasurface reflection phase;

[0017] Step 3, using the Fourier transform scheme of Bessel-Gaussian beam to generate a perfect vortex;

[0018] Step 4, calculating the phase condition of the multiplexed metasurface according to the parameters of the four-path incident dual-polarized plane waves;

[0019] Step 5, determine the metasurface specifications and complete the model construction of the dual-polarization multiplexed microwave perfect vortex metasurface;

[0020] Step 6. Establish an observation plane model at the set focal plane position, and use air boxes to wrap the metasurface and the observation plane respectively. After the simulation, the amplitude and phase distribution of the eight-way perfect vortex are displayed on the observation plane.

[0021] Preferably, in step 1, the operating frequency band of the metasurface is 15 GHz, and the metasurface modeling is completed using HFSS modeling software, that is, single-layer "Jerusalem cross" type unit modeling.

[0022] Preferably, in step 2, the calculation method of the metasurface reflection phase is as follows:

[0023] Take the intersection of the orthogonal cross patches as the origin, establish a coordinate system, set the propagation direction of the four incident electromagnetic waves to be in the xoz or yoz plane, in the spherical coordinate system, The angle values ​​are 0°, 90°, 180°, and 270°, respectively. After discretizing the generalized Snell's law, the reflection phase carried by the metasurface required for any electromagnetic wave can be obtained.

[0024] Preferably, in step 3, the steps of generating a perfect vortex are as follows:

[0025] The phase modulation effect of the metasurface on electromagnetic waves is used to realize all the functions of the spiral phase plate, axicon and lens, and the functional combination is achieved through phase superposition. The distribution corresponding to the spiral phase plate is Φ s , the phase distribution corresponding to the axicon is Φ a , the phase distribution corresponding to the lens is Φ l , based on the above information, calculate the phase conditions required to produce a perfect vortex:

[0026]

[0027] Φ a =krsinα

[0028]

[0029] Where l represents the topological charge of the perfect vortex, k represents the wave number in vacuum, r represents the polar coordinate radius of the plane where the metasurface is located, tanα = R / f, R represents the set radius of the perfect vortex, and f is the focal length of the lens;

[0030] According to the phase superposition principle, we can get:

[0031] Ψ=Φ s +Φ a +Φ l

[0032] The phase distribution Ψ can be used to adjust the vertically emitted Gaussian beam to generate a perfect vortex of microwaves carrying the orbital angular momentum mode l.

[0033] Preferably, in step 4, the phase distribution of the eight-way multiplexed microwave perfect vortex metasurface is as follows:

[0034]

[0035]

[0036] In the formula, the superscripts x and y represent two different polarization modes.

[0037] Preferably, in step 5, a mapping relationship between the unit S11 parameter phase and the "Jerusalem Cross" size is established based on the calculation result of step 1, and the modulation phase that each unit needs to achieve is given according to the total phase distribution formula obtained in step 4; based on the above mapping relationship, the size information corresponding to the modulation phase required for each unit is found to adjust the unit shape; these units are combined together to complete the model design of the dual-polarization multiplexed microwave perfect vortex metasurface in HFSS software.

[0038] Preferably, in step 6, when setting the focal plane position to establish the observation plane model, the excitation mode selects plane wave excitation, and the boundary condition selects FEBI boundary.

[0039] Compared with the prior art, the present invention has the following advantages:

[0040] The present invention provides a dual-polarization multiplexed microwave perfect vortex metasurface and a construction method thereof. A metasurface unit is designed by combining a Jerusalem cross pattern and a surrounding strip pattern. The phase control change of the dual-polarization reflected electromagnetic wave is achieved by different size changes in the unit pattern in the x and y directions. The Fourier transform scheme of the Bessel-Gaussian beam is used to calculate the phase distribution conditions required for generating a single-path perfect vortex. A metasurface array with size changes is designed according to the phase distribution. Four dual-polarization electromagnetic waves are incident in different directions to generate eight microwave perfect vortices carrying orbital angular momentum of different modes for coaxial transmission perpendicular to the surface.

[0041] The present invention utilizes microwave perfect vortex for orbital angular momentum multiplexing communication, which can effectively alleviate the divergence problem of traditional vortex waves, realize the concentrated distribution of electromagnetic energy near a fixed-size annular area on the receiving plane, and is conducive to simplifying the design of the receiving antenna, improving the receiving efficiency and the space utilization of the antenna, and realizing the generation and multiplexing of microwave perfect vortex.

[0042] The metasurface provided by the present invention supports independent regulation of electromagnetic waves in two polarization modes in the x and y directions. Since the two polarization modes are orthogonal to each other in space and do not interfere with each other, a new degree of freedom is provided for orbital angular momentum multiplexing, which increases the number of signal multiplexing paths supported by a single metasurface exponentially, greatly expanding the channel capacity of the communication system;

[0043] The present invention can realize the integration of multiple functions and complete complex electromagnetic phase modulation based on the phase superposition principle of the metasurface. The present invention uses a metasurface to complete the generation of eight-way microwave perfect vortex, avoiding the cumbersome instruments and equipment in optical design, making the perfect vortex generating device more lightweight and integrated, and providing reference for the direction of microwave perfect vortex. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1Schematic diagram of the dual-polarization multiplexed microwave perfect vortex metasurface structure in an embodiment of the present invention;

[0045] Figure 2 It is a side schematic diagram of a dual-polarization multiplexed microwave perfect vortex metasurface in an embodiment of the present invention;

[0046] Figure 3 Schematic diagram of a top view of a dual-polarization multiplexed microwave perfect vortex metasurface in an embodiment of the present invention;

[0047] Figure 4 Schematic diagram of the polarization amplitude of the parameter x of the metasurface unit S11 in an embodiment of the present invention;

[0048] Figure 5 Schematic diagram of the polarization phase of the parameter x of the metasurface unit S11 in an embodiment of the present invention;

[0049] Figure 6 Schematic diagram of the y polarization amplitude of the metasurface unit S11 parameter in an embodiment of the present invention;

[0050] Figure 7 Schematic diagram of the y-polarization phase of the metasurface unit S11 parameter in an embodiment of the present invention;

[0051] Figure 8 This is the x-phase distribution diagram of the dual-polarization multiplexed microwave perfect vortex metasurface in an embodiment of the present invention;

[0052] Fig. 9 This is the y-phase distribution diagram of the dual-polarization multiplexed microwave perfect vortex metasurface in an embodiment of the present invention;

[0053] Fig.10 Schematic diagram of the dual-polarization multiplexed microwave perfect vortex metasurface structure in an embodiment of the present invention;

[0054] Fig.11 : is the amplitude diagram of the x-polarized microwave perfect vortex on the focal plane in an embodiment of the present invention (0 topological charge);

[0055] Fig.12 : is the phase diagram of the x-polarized microwave perfect vortex on the focal plane in an embodiment of the present invention (0 topological charge);

[0056] Fig.13 : is the amplitude diagram of the x-polarized microwave perfect vortex on the focal plane in the embodiment of the present invention (1 topological charge);

[0057] Fig.14 : is the phase diagram (1 topological charge) of the x-polarized microwave perfect vortex on the focal plane in an embodiment of the present invention;

[0058] Fig.15: is the amplitude diagram of the x-polarized microwave perfect vortex on the focal plane in the embodiment of the present invention (2 topological charge);

[0059] Fig.16 : is the phase diagram (2 topological charge) of the x-polarized microwave perfect vortex on the focal plane in an embodiment of the present invention;

[0060] Fig.17 : is the amplitude diagram of the x-polarized microwave perfect vortex on the focal plane in the embodiment of the present invention (3 topological charge);

[0061] Fig.18 : is the phase diagram (3 topological charge) of the x-polarized microwave perfect vortex on the focal plane in the embodiment of the present invention;

[0062] Fig.19 Graph a is an analysis diagram of an orbital angular momentum pattern of an x-polarized microwave perfect vortex in an embodiment of the present invention;

[0063] Fig. 20 Figure b is an analysis diagram of the orbital angular momentum mode of the x-polarized microwave perfect vortex in an embodiment of the present invention;

[0064] Fig.21 Figure c is an analysis diagram of the orbital angular momentum mode of the x-polarized microwave perfect vortex in an embodiment of the present invention;

[0065] Fig. 22 d is an analysis diagram of the orbital angular momentum mode of the x-polarized microwave perfect vortex in an embodiment of the present invention;

[0066] Fig.23 : is the amplitude diagram of the y-polarized microwave perfect vortex on the focal plane in an embodiment of the present invention (0 topological charge);

[0067] Fig.24 : is the phase diagram of the y-polarized microwave perfect vortex on the focal plane in an embodiment of the present invention (0 topological charge);

[0068] Fig.25 : is the amplitude diagram of the y-polarized microwave perfect vortex on the focal plane in an embodiment of the present invention (1 topological charge);

[0069] Fig.26 : is the phase diagram (1 topological charge) of the y-polarized microwave perfect vortex on the focal plane in an embodiment of the present invention;

[0070] Fig. 27 : is the amplitude diagram of the y-polarized microwave perfect vortex on the focal plane in an embodiment of the present invention (2 topological charge);

[0071] Fig.28 : is the phase diagram (2 topological charge) of the y-polarized microwave perfect vortex on the focal plane in an embodiment of the present invention;

[0072] Fig.29: is the amplitude diagram of the y-polarized microwave perfect vortex on the focal plane in an embodiment of the present invention (3 topological charge);

[0073] Fig.30 : is the phase diagram (3 topological charge) of the y-polarized microwave perfect vortex on the focal plane in an embodiment of the present invention;

[0074] Fig.31 Graph a is an analysis diagram of the orbital angular momentum mode of a y-polarized microwave perfect vortex in an embodiment of the present invention;

[0075] Fig.32 Figure b is an analysis diagram of the orbital angular momentum mode of a y-polarized microwave perfect vortex in an embodiment of the present invention;

[0076] Fig.33 Figure c is an analysis diagram of the orbital angular momentum mode of a y-polarized microwave perfect vortex in an embodiment of the present invention;

[0077] Fig.34 d is an analysis diagram of the orbital angular momentum pattern of the y-polarized microwave perfect vortex in an embodiment of the present invention.

[0078] In the figure, 1 is the substrate; 2 is the floor; and 3 is the patch. DETAILED DESCRIPTION

[0079] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0080] like Figures 1 to 3 As shown, the technical solution of the present invention provides a dual-polarization multiplexed microwave perfect vortex metasurface, comprising:

[0081] The substrate 1 is a regular polyhedron structure with a certain thickness.

[0082] The floor 2 is arranged on the lower surface of the substrate 1 .

[0083] The patch 3 is arranged on the upper surface of the substrate 1, including a cross-shaped structure arranged orthogonally in the center of the substrate 1 and long strip patches arranged on the four sides of the cross-shaped structure, and the four long strip patches are not in contact with each other; the four vertices of the cross-shaped patch are provided with short strip patches perpendicular to the direction.

[0084] In one embodiment of the present invention, the substrate 1 is a regular hexahedron structure and is made of F4B material.

[0085] In one embodiment of the present invention, the floor 2 and the patch 3 are both made of metal.

[0086] In addition to providing a dual-polarization multiplexed microwave perfect vortex metasurface, the technical solution of the present invention further provides a method for constructing the above-mentioned microwave perfect vortex metasurface. The method is mainly based on ANSYS HFSS software to simulate and verify the design scheme. The specific design method and simulation verification process are as follows:

[0087] Step 1: Design the size specifications of the metasurface unit according to the wavelength data, and use the modeling software to model the metasurface;

[0088] Step 2: Use four dual-polarized electromagnetic waves from different directions to calculate the metasurface reflection phase;

[0089] Step 3, using the Fourier transform scheme of Bessel-Gaussian beam to generate a perfect vortex;

[0090] Step 4, calculating the phase condition of the multiplexed metasurface according to the parameters of the four-path incident dual-polarized plane waves;

[0091] Step 5, determine the metasurface specifications and complete the model construction of the dual-polarization multiplexed microwave perfect vortex metasurface;

[0092] Step 6. Establish an observation plane model at the set focal plane position, and use air boxes to wrap the metasurface and the observation plane respectively. After the simulation, the amplitude and phase distribution of the eight-way perfect vortex are displayed on the observation plane.

[0093] In one embodiment of the present invention, a modeling method for step 1 is provided, which is as follows: determine that the operating frequency band of the metasurface is 15 GHz, and design the size specifications of the metasurface unit according to the wavelength data. Then, use HFSS to complete the modeling of a single-layer "Jerusalem cross" unit, which is a metal patch 3, a dielectric substrate 1, and a metal ground 2 in the negative direction of the z-axis. Figures 1 to 3 As shown, the geometric parameters of the model are shown in Table 1.

[0094] The unit dielectric substrate 1 in this embodiment is made of F4B material, which has a dielectric constant of approximately 2.65 and a loss tangent of approximately 0.001. Use an "air box" to wrap the unit model, set master-slave boundary conditions on the four sides, and set a Floquent port on the top surface. Only the existence of TE and TM modes is considered here. Make sure that the propagation direction of the plane wave excitation is at an angle of 30° to the z-axis, and modify the phase data of the Floquent port to achieve an oblique incidence effect. After completing the above preparations, the relationship curve between the S11 parameter and the size change of the "cross" double arms is obtained through simulation calculation, and the following is obtained after visualization processing. Figures 4 to 7 The relationship between the S11 parameter amplitude, phase and unit size of the metasurface unit is shown. The phase information is extracted to provide data support for subsequent metasurface design.

[0095] Table 1 Description of the parameters of the simulation verification metasurface unit

[0096] Parameter name Parameter value (mm) Parameter name Parameter value (mm) p_len 7.2 b_len 0.6 t_len 0.018 a_len 1.2 h_len 1.0 l_len 6.0 w_len 0.2

[0097] In one embodiment of the present invention, a method for calculating the metasurface reflection phase for step 2 is provided, which is as follows:

[0098] In order to achieve the deflection of the propagation direction of electromagnetic waves, it is necessary to calculate the metasurface reflection phase. Take the intersection of the orthogonal cross patches as the origin, establish a coordinate system, and set the propagation directions of the four incident electromagnetic waves to be in the xoz or yoz plane. In the spherical coordinate system, The angle values ​​are 0°, 90°, 180°, and 270° respectively. After discretizing the generalized Snell's law, the reflection phase carried by the metasurface required for any electromagnetic wave can be obtained. The generalized Snell's law can be expressed as:

[0099]

[0100] The above formula is in continuous form. Here we discretize it and get the following formula:

[0101]

[0102] Where d represents the unit side length, and Φ0 represents the initial phase of the metasurface edge. Substituting the relevant data, the above formula can be used to calculate the reflection phase carried by the metasurface required for any electromagnetic wave.

[0103] In one embodiment of the present invention, a method for generating a perfect vortex in step 3 is provided, which is as follows:

[0104] The perfect vortex is generated by the Fourier transform scheme of the Bessel-Gaussian beam. According to the optical principle, this scheme needs to first generate a Bessel-Gaussian beam, and then use a lens to transform it into a perfect vortex. During this period, a spiral phase plate is used to make the beam carry orbital angular momentum. This means that at least three optical devices, a spiral phase plate, an axicon, and a lens, are required to generate a perfect vortex. Metasurface theory shows that the phase modulation effect of the metasurface on electromagnetic waves can be used to realize all the functions of the above three devices, and the functional combination can be achieved through simple phase superposition. This step requires the calculation of the phase conditions required to generate a perfect vortex. If the distribution corresponding to the spiral phase plate is Φ s , the phase distribution corresponding to the axicon is Φ a , the phase distribution corresponding to the lens is Φ l , then

[0105]

[0106] Φa =krsinα

[0107]

[0108] In the formula, l represents the topological charge of the perfect vortex, k represents the wave number in vacuum, r represents the polar coordinate radius of the plane where the metasurface is located, tanα=R / f, R represents the set radius of the perfect vortex, and f is the focal length of the lens; the set radius R of the perfect vortex is determined to be 15 cm, and the focal length f is 91 cm. According to the phase superposition principle, the following formula can be obtained:

[0109] Ψ=Φ s +Φ a +Φ l

[0110] The phase distribution Ψ can be used to adjust the vertically emitted Gaussian beam to generate a perfect vortex of microwaves carrying the orbital angular momentum mode l.

[0111] In another embodiment of the present invention, in step 4, the calculation method of the phase condition of the multiplexed metasurface is as follows:

[0112] Four dual-polarized electromagnetic waves with different directions are incident, and the phase conditions of the multiplexed metasurface are calculated according to the parameters of the four incident dual-polarized plane waves. The incident directions of the four dual-polarized plane waves are θ=30°, φ=-180°, θ=30°, φ=-90°, θ=30°, φ=0°, θ=30°, φ=90°, respectively. The topological charges expected to be carried by the x-polarized wave are 0, 1, 2, and 3, respectively, and the topological charges expected to be carried by the y-polarized wave are 3, 0, 1, and 2, respectively. Based on steps 2 and 3, the phase distribution of the eight-channel multiplexed microwave perfect vortex metasurface is determined as follows:

[0113]

[0114]

[0115] In the formula, the superscripts x and y represent two different polarization modes. Substituting a series of parameters previously set can obtain the desired metasurface phase conditions. In this embodiment, the calculation results are as follows: Figures 8 to 9 It should be pointed out here that since electromagnetic waves are much more sensitive to phase modulation than amplitude modulation, only extracting the superimposed phase information can well achieve the desired function.

[0116] In one embodiment of the present invention, in step 5, the metasurface specification is determined to be 35*35 (number of units * number of units). Based on the calculation results of step 1, a mapping relationship between the unit S11 parameter phase and the size of the "Jerusalem Cross" is established, and the modulation phase that each unit needs to achieve is given by the total phase distribution formula obtained in step 4. Based on the above mapping relationship, the size information corresponding to the modulation phase required for each unit is found to adjust the unit shape. Finally, these units are combined together to complete the model design of the dual-polarization multiplexed microwave perfect vortex metasurface in the HFSS software, as shown in FIG. Fig.10 shown.

[0117] In one embodiment of the present invention, step 6 specifically includes the following steps:

[0118] An observation plane model is established at the set focal plane position, and air boxes are used to wrap the metasurface and the observation plane respectively. The excitation method is plane wave excitation, and the boundary condition is FEBI boundary. After the simulation is completed, the amplitude and phase distribution of the eight-way perfect vortex can be seen on the observation plane. Figures 11 to 18 The amplitude and phase distribution of the x-polarized perfect vortex are described. Figures 23 to 30 It describes the amplitude and phase distribution of the y-polarized perfect vortex.

[0119] The above-mentioned embodiments are analyzed and the results show that:

[0120] from Figures 4 to 7 It can be seen that the metamaterial unit designed in the present invention has very excellent dual-polarization independent regulation performance. Figure 4 and Figure 6 The amplitude response of the unit is described. It can be seen that the amplitude values ​​of the S11 parameter are all within the interval [0.9, 1.0], which can be regarded as full reflection of energy. Figure 5 and Figure 7 The phase response of the unit is described, and the effective phase modulation range can cover about 320°, which can meet the needs of realizing multiplexing and generating microwave perfect vortex. The simulation results show that the unit has a low coupling degree of response to the two polarizations, and can achieve independent regulation of electromagnetic waves with different polarizations.

[0121] Figure 8 and Fig. 9 The metasurface modulation phase distribution under x-polarized and y-polarized electromagnetic waves is shown respectively. The metasurface based on this phase design can transform four obliquely incident dual-polarized plane waves into eight coaxially emitted microwave perfect vortices.

[0122] Figures 11 to 18 and Figures 23 to 30The amplitude and phase distribution of x-polarized and y-polarized microwave perfect vortices are shown respectively. The radius of the ring in the figure is 15 cm. The amplitude distribution results show that the energy of perfect vortices carrying different topological charges is concentrated near the ring, and the divergence is much smaller than that of ordinary Laguerre-Gaussian beams. In addition, the vortex pattern can be clearly seen from the phase distribution diagram without serious distortion. These results show that the metasurface can generate high-quality microwave perfect vortex beams and achieve the expected functions while supporting dual-polarization multiplexing.

[0123] Figures 19 to 22 and Figure 31 to Figure 34 The results of orbital angular momentum mode analysis based on spatial Fourier transform under two polarization modes are shown respectively. By sampling and calculating the phase distribution results on a 15cm ring, a bar graph of different polarizations and different orbital angular momentum modes can be drawn. In this embodiment, the modes in the range of -6 to 6 are analyzed, and it can be seen that all modes with the highest energy share are set modes, which confirms the reliability of the generated perfect vortex for orbital angular momentum multiplexing communication from a quantitative perspective.

[0124] The present invention combines metasurfaces and optical principles to provide a design method for a dual-polarization multiplexed microwave perfect vortex metasurface, designs a typical metasurface structure scheme, and verifies the design method through simulation. The designed typical metasurface structure can convert dual-polarization plane waves incident in different directions into microwave perfect vortices through phase modulation, and deflect them to the coaxial direction perpendicular to the surface for transmission, thereby realizing orbital angular momentum multiplexing based on perfect vortices. This integrated design simplifies the complex spiral phase plate-axis pyramid-lens optical path system of the traditional optical solution. A perfect vortex in the microwave band can be generated with only one metasurface, which reduces the difficulty of generating a perfect microwave vortex. In addition, the metasurface's support for independent regulation of dual-polarization electromagnetic waves also doubles the number of multiplexing paths and expands the channel capacity. In addition, the invariant radius property of the perfect vortex can overcome the divergence problem of traditional orbital angular momentum multiplexing communications, thereby greatly simplifying the design of the receiving antenna, which brings extremely important value to future orbital angular momentum multiplexing communications.

[0125] The above are preferred embodiments of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A dual-polarization multiplexed microwave perfect vortex metasurface, characterized by: The metasurface comprises: The substrate (1) is a regular polyhedron structure with a certain thickness; A floor (2) is arranged on the lower surface of the substrate (1); The patch (3) is arranged on the upper surface of the substrate (1), and comprises a cross-shaped structure arranged orthogonally at the center of the substrate (1) and long strip patches arranged at the four sides of the cross-shaped structure, wherein the four long strip patches are not in contact with each other; and short strip patches perpendicular to the direction are arranged at the four vertices of the cross-shaped patch.

2. A dual-polarization multiplexed microwave perfect vortex metasurface as claimed in claim 1, characterized in that: The substrate (1) is a regular hexahedron structure and is made of F4B material.

3. A dual-polarization multiplexed microwave perfect vortex metasurface as claimed in claim 2, characterized in that: The floor (2) and the patch (3) are both made of metal.

4. A method for constructing a dual-polarization multiplexed microwave perfect vortex metasurface, characterized in that: The method is used to construct the super surface according to any one of claims 1 to 3, and the specific steps are as follows: Step 1: Design the size specifications of the metasurface unit according to the wavelength data, and use the modeling software to model the metasurface; Step 2: Use four dual-polarized electromagnetic waves from different directions to calculate the metasurface reflection phase; Step 3, using the Fourier transform scheme of Bessel-Gaussian beam to generate a perfect vortex; Step 4, calculating the phase condition of the multiplexed metasurface according to the parameters of the four-path incident dual-polarized plane waves; Step 5, determine the metasurface specifications and complete the model construction of the dual-polarization multiplexed microwave perfect vortex metasurface; Step 6. Establish an observation plane model at the set focal plane position, and use air boxes to wrap the metasurface and the observation plane respectively. After the simulation, the amplitude and phase distribution of the eight-way perfect vortex are displayed on the observation plane.

5. The method for constructing a dual-polarization multiplexed microwave perfect vortex metasurface according to claim 4, characterized in that: In the step 1, the operating frequency band of the metasurface is 15 GHz, and the metasurface modeling is completed using HFSS modeling software, that is, single-layer "Jerusalem cross" type unit modeling.

6. The method for constructing a dual-polarization multiplexed microwave perfect vortex metasurface according to claim 5, characterized in that: In step 2, the calculation method of the metasurface reflection phase is as follows: Take the intersection of the orthogonal cross patches as the origin, establish a coordinate system, set the propagation direction of the four incident electromagnetic waves to be in the xoz or yoz plane, in the spherical coordinate system, The angle values ​​are 0°, 90°, 180°, and 270°, respectively. After discretizing the generalized Snell's law, the reflection phase carried by the metasurface required for any electromagnetic wave can be obtained.

7. The method for constructing a dual-polarization multiplexed microwave perfect vortex metasurface according to claim 6, characterized in that: In step 3, the steps for generating a perfect vortex are as follows: The phase modulation effect of the metasurface on electromagnetic waves is used to realize all the functions of the spiral phase plate, axicon and lens, and the functional combination is achieved through phase superposition. The distribution corresponding to the spiral phase plate is Φ s , the phase distribution corresponding to the axicon is Φ a , the phase distribution corresponding to the lens is Φ l , based on the above information, calculate the phase conditions required to produce a perfect vortex: F a =Krsina Where l represents the topological charge of the perfect vortex, k represents the wave number in vacuum, r represents the polar coordinate radius of the plane where the metasurface is located, tanα = R / f, R represents the set radius of the perfect vortex, and f is the focal length of the lens; According to the phase superposition principle, we can get: Ψ=Φ s +F a +F l The phase distribution Ψ can be used to adjust the vertically emitted Gaussian beam to generate a perfect vortex of microwaves carrying the orbital angular momentum mode l.

8. The method for constructing a dual-polarization multiplexed microwave perfect vortex metasurface according to claim 7, characterized in that: In step 4, the phase distribution of the eight-way multiplexed microwave perfect vortex metasurface is as follows: In the formula, the superscripts x and y represent two different polarization modes.

9. The method for constructing a dual-polarization multiplexed microwave perfect vortex metasurface according to claim 8, characterized in that: In the step 5, a mapping relationship between the unit S11 parameter phase and the "Jerusalem Cross" size is established based on the calculation result of step 1, and the modulation phase that each unit needs to achieve is given according to the total phase distribution formula obtained in step 4; based on the above mapping relationship, the size information corresponding to the modulation phase required for each unit is found to adjust the unit shape; these units are combined together to complete the model design of the dual-polarization multiplexed microwave perfect vortex metasurface in HFSS software.

10. The method for constructing a dual-polarization multiplexed microwave perfect vortex metasurface according to claim 9, characterized in that: In step 6, when setting the focal plane position to establish the observation plane model, the excitation method selects plane wave excitation, and the boundary condition selects FEBI boundary.

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