Quasi-diffraction-free Pilsey vortex beam generation method based on electromagnetic metasurfaces

Abstract

A method for generating quasi-diffraction-free Pilsier vortex beams based on electromagnetic metasurfaces is presented. This method compensates for the phase and amplitude required for quasi-diffraction-free Pilsier vortex beams with different focal points through the design of the electromagnetic metasurface, resulting in beams with excellent propagation characteristics. Generating quasi-diffraction-free beams using electromagnetic metasurfaces avoids the drawbacks of complex structures and high costs associated with traditional lenses. By integrating the design of Pilsier beams and vortex beams, a quasi-diffraction-free Pilsier vortex beam is generated in the microwave band. This beam combines the quasi-diffraction characteristics of Pilsier beams with the orthogonal OAM modes of vortex beams, offering the advantage of flexible control over the focal point position. It can be applied in far-field communication, imaging, and detection, as well as in the multiplexing and encoding / modulation of information in wireless communication, fulfilling the requirements for high-capacity, high-speed wireless communication.

Description

Technical Field

[0001] This invention belongs to the field of communication technology, and more specifically relates to a method for generating quasi-diffraction-free Pilsner vortex beams based on electromagnetic metasurfaces in the field of microwave technology. This invention can be used for multiplexing and transmitting or coding and modulating information in wireless communication, realizing the needs of high-capacity, high-speed wireless communication. Background Technology

[0002] Currently, in the field of communication technology, beams carrying orbital angular momentum (OAM) are called vortex beams, and different OAM modes are orthogonal. This new dimension of orbital angular momentum in vortex beams can be used for multiplexing and transmitting information or for coding and modulation in wireless communication, enabling high-capacity, high-speed wireless communication. Traditional vortex beams can be generated using helical phase plates, reflector antennas, and array antennas. However, due to the inherent divergence characteristics of traditional vortex beams, effective reception over long distances is difficult. This makes it challenging to use orbital angular momentum for long-distance communication. Combining quasi-diffraction-free beams with traditional vortex beams can effectively suppress the divergence angle of vortex beams, allowing them to be better applied to long-distance communication. Typical quasi-diffraction-free beams include Bessel beams, Airy beams, and Pearcey beams.

[0003] Chongqing University disclosed a beam phase modulation method in its patent application, "Two-Dimensional Enhanced Focusing Airy OAM Beam Phase Modulation Method" (Application No.: 202211310414.5, Publication No.: CN 115458947 A). This method adds a near-field focusing phase distribution to the Airy OAM phase distribution, and based on the designed focus of the Airy OAM phase distribution, the field contributions of the near-field focusing phase distribution are superimposed in the same direction to obtain an enhanced Airy OAM phase distribution. However, this design method still has shortcomings. Because it only compensates for the phase required by the beam and ignores the beam amplitude information, it affects beam performance, resulting in low energy intensity of the self-focusing beam.

[0004] Guangxi University disclosed a method for generating a self-focusing beam with adjustable focusing times and focal length in its patent application "A Method for Generating a Self-Focusing Beam with Adjustable Focusing Times and Focal Length" (Application No.: 202311203057.7, Publication No.: CN 117192786 A). This method generates a self-focusing beam with adjustable focusing times and focal length by superimposing a circular Pilsner beam and a circular Bessel beam. However, this design method still has shortcomings. Due to the complex structure and high cost of spatial light modulators, the beam generation cost is high and the structure is not simple enough.

[0005] Zhejiang Normal University disclosed a method for generating a cluster of Pearcey beams of arbitrary shape in its patent application, "A Method for Generating a Pearcey Beam Cluster" (Application No.: 201510434964.1, Publication No.: CN 105182543 A). This method, based on differential geometry and Fresnel diffraction theory, derives the general parabolic function bifurcation point set and presents a method for generating Pearcey beams of arbitrary shape using amplitude modulation and Fresnel diffraction. However, this design method still has shortcomings. Because it only designs the Pearcey beam and does not integrate the design of the Pearcey beam and the vortex beam, the beam generated by this method cannot simultaneously possess the characteristics of the Pearcey beam's freely adjustable focal length and the orthogonal OAM modes of the vortex beam. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of the prior art by proposing a design method for a quasi-diffraction-free Pilssie vortex beam electromagnetic metasurface. This method solves the problems of poor performance, complex device structure, and high cost of quasi-diffraction-free beams, and the inability of the generated beams to simultaneously possess the characteristics of Pilssie beams (allowing for free focal length adjustment) and vortex beams (allowing for mutually orthogonal OAM modes).

[0007] The purpose of this invention is to compensate for the phase and amplitude of quasi-diffraction-free Pilsey vortex beams with different focal points through the design of an electromagnetic metasurface. The resulting beam exhibits excellent propagation characteristics, superior beam performance, and high energy intensity, solving the problem of poor beam performance caused by prior art that only compensates for the phase. This invention generates quasi-diffraction-free beams through an electromagnetic metasurface, which has the advantages of simple structure, low loss, and low cost, overcoming the problems of complex and costly lens structures manufactured using optical methods in existing technologies. This invention generates a quasi-diffraction-free Pilsey vortex beam in the microwave frequency band through the design of an electromagnetic metasurface. Compared with other quasi-diffraction-free beams, this beam combines the quasi-diffraction-free characteristics of Pilsey beams with the advantages of orthogonal OAM modes in vortex beams, offering the advantage of flexible control over the focal point position. This solves the problem that existing technologies cannot simultaneously possess the freely adjustable focal length of Pilsey beams and the orthogonal OAM modes of vortex beams.

[0008] To achieve the above objectives, the technical solution adopted by the present invention includes the following:

[0009] Step 1: Calculate the focus adjustment factor based on the focus of the quasi-diffraction-free Pilssie vortex beam to be generated;

[0010] Step 2: Set the scale of the electromagnetic metasurface, the spacing of the electromagnetic metasurface units, the OAM mode of the quasi-diffraction-free Pilssie vortex beam, and the position of the feed horn.

[0011] Step 3: Calculate the Pilsier integral for each unit of the electromagnetic metasurface based on the focus adjustment factor;

[0012] Step 4: Calculate the required modulation amplitude and compensation phase for each unit of the electromagnetic metasurface based on the Pierce integral of the coordinates of each unit.

[0013] Step 5: Design the electromagnetic metasurface unit and draw the transmission phase table and transmission amplitude table of the electromagnetic metasurface unit;

[0014] Step 6: Adjust the state of each unit of the electromagnetic metasurface according to the required control amplitude and compensation phase of each unit to obtain the electromagnetic metasurface;

[0015] Step 7: Place the electromagnetic metasurface and the feed horn at the set position, and apply an radio frequency signal to the feed horn to generate a quasi-diffraction-free Pilsner vortex beam with a configurable focal length.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] First, this invention compensates for both the phase and amplitude required by the beam simultaneously through the design of an electromagnetic metasurface, overcoming the shortcomings of existing technologies that only compensate for the phase of the beam. This results in a beam with excellent propagation characteristics, superior beam performance, and high beam energy intensity, which is expected to be applied in far-field communication, imaging, detection, and other applications.

[0018] Secondly, the present invention generates quasi-diffraction-free beams through electromagnetic metasurfaces, overcoming the disadvantages of complex and high-cost lens structures manufactured by optical methods in the prior art. This makes the electromagnetic metasurface designed in the present invention have the advantages of simple structure, low loss and low cost.

[0019] Third, this invention generates a quasi-diffraction-free Pilsier vortex beam in the microwave band, overcoming the shortcomings of existing beam designs that cannot simultaneously possess the characteristics of Pilsier beams (allowing for free focal length adjustment) and vortex beams (characteristics of mutually orthogonal OAM modes). This invention's quasi-diffraction-free Pilsier beam combines the advantages of both Pilsier beams (quasi-diffraction-free characteristics) and vortex beams (mutually orthogonal OAM modes), offering the advantage of flexible control over the focal point. This facilitates its application in wireless communication for information multiplexing, transmission, or coding modulation, fulfilling the requirements of high-capacity, high-speed wireless communication. Attached Figure Description

[0020] Figure 1 This is a flowchart of the present invention;

[0021] Figure 2 This is a schematic diagram of the electromagnetic metasurface unit designed in an embodiment of the present invention;

[0022] Figure 3 This is a schematic diagram of the metal patch in the electromagnetic metasurface unit designed in an embodiment of the present invention;

[0023] Figure 4 Focal length in the simulation experiment of this invention Schematic diagram of phase compensation for electromagnetic metasurfaces;

[0024] Figure 5 Focal length in the simulation experiment of this invention Schematic diagram of the amplitude modulation of electromagnetic metasurface;

[0025] Figure 6 This is a schematic diagram of the electric field intensity on the observation surface along the beam propagation direction obtained from the simulation experiment of this invention;

[0026] Figure 7 The focus of the simulation experiment of this invention A schematic diagram of the electric field intensity at the observation surface;

[0027] Figure 8 The focus of the simulation experiment of this invention A schematic diagram of the electric field phase at the observation surface. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] Reference Figure 1 The implementation steps of the embodiments of the present invention will be described in further detail below.

[0030] Step 1: Calculate the focus adjustment factor based on the focus of the quasi-diffraction-free Pilssie vortex beam to be generated.

[0031] ,

[0032] in, This represents the focus adjustment factor obtained based on the focus of the quasi-diffraction-free Pilsier vortex beam to be generated. This represents the focal point of the quasi-diffraction-free Pilsier vortex beam to be generated, where π represents the mathematical constant pi. This indicates the operating wavelength of the electromagnetic metasurface.

[0033] Step 2: Set the scale of the electromagnetic metasurface, the spacing of the electromagnetic metasurface units, the OAM mode of the quasi-diffraction-free Pilssie vortex beam, and the position of the feed horn.

[0034] The scale of the electromagnetic metasurface, the spacing between its cells, the OAM mode of the quasi-diffraction-free Pilscher vortex beam, and the position of the feed horn are all determined and generated in the xoy plane of a Cartesian coordinate system. The electromagnetic metasurface generating the quasi-diffraction-free Pilscher vortex beam is composed of M rows and N columns of cells, where M=60 and N=60; the row spacing between any two cells is d. M d M =5mm, the column spacing between any two elements is d N d N =5mm, the OAM mode of the quasi-diffraction-free Pilsey vortex beam is set as follows: The coordinates of the feed horn in the Cartesian coordinate system are set as follows: .

[0035] Step 3: Calculate the Pilsier integral for each unit cell of the electromagnetic metasurface based on the focus adjustment factor.

[0036] ,

[0037] in, Represent the Pilsier integral of the m-th row and n-th column element in the electromagnetic metasurface. , , Let represent the coordinates of the center of the cell in the m-th row and n-th column in the planar coordinate system, exp(.) represents the exponential operation with the natural constant e as the base, j represents the imaginary unit, and s represents the characteristic parameter of the Pirsey integral function. This represents the radius of the central region of the quasi-diffraction-free Pilsey vortex beam. .

[0038] Step 4: Calculate the required control amplitude and compensation phase for each unit of the electromagnetic metasurface based on the Pilsier integral of the coordinates of each unit, in order to adjust the state of the electromagnetic metasurface unit.

[0039] The compensation phase required for each element of the electromagnetic metasurface is obtained by the following formula:

[0040] ,

[0041] in, This represents the compensation phase required for the m-th row and n-th column element in the electromagnetic metasurface. (.) indicates the operation of taking the complex argument. Indicates that it is located at The azimuth angle of the electromagnetic metasurface unit relative to the origin.

[0042] The required modulation amplitude for each unit of the electromagnetic metasurface is obtained by the following formula:

[0043] ,

[0044] in, This represents the required modulation amplitude for the m-th row and n-th column cell in the electromagnetic metasurface. (.) indicates the operation of taking the modulus of a complex number.

[0045] Step 5: Design the electromagnetic metasurface unit and draw the transmission phase table and transmission amplitude table of the electromagnetic metasurface unit.

[0046] The electromagnetic metasurface unit (EMF) design refers to an EMF unit where all structures are identical except for the metal patch. Each EMF unit includes a first metal grating layer, a second metal grating layer, a metal patch, a first dielectric layer, and a second dielectric layer. The first and second dielectric layers are cuboids of equal volume and shape. The first and second metal grating layers are printed at the top and bottom ends of the first and second dielectric layers, respectively. The first metal grating consists of three equally spaced square metal sheets arranged parallel to each other along the x-axis of the substrate. The second metal grating consists of three equally spaced square metal sheets arranged parallel to each other along the y-axis of the substrate. The metal patch is printed between the first and second dielectric layers. The shape of the metal patch can be either an open annular shape or an I-shape. The opening angle of the metal patch controls the transmission phase of the EMF unit, with a transmission phase variation range close to or exceeding 360°. The rotation angle of the metal patch controls the transmission amplitude of the EMF unit, with a transmission amplitude range of [missing information]. .

[0047] Reference Figure 2 and Figure 3 The metasurface antenna unit structure in the embodiments of the present invention will be further described.

[0048] In the embodiments of the present invention, the metal patch of the metasurface antenna element is I-shaped. Figure 2 This is a schematic diagram of the structure of an electromagnetic metasurface unit. The unit includes a first metal grating layer, a second metal grating layer, a metal patch, a first dielectric layer, and a second dielectric layer. The first and second dielectric layers are cuboids of equal volume and shape. The first and second metal grating layers are printed at their respective top and bottom ends. The first metal grating consists of three identical square metal sheets arranged parallel to each other along the x-axis of the substrate with equal spacing. The second metal grating consists of three identical square metal sheets arranged parallel to each other along the y-axis of the substrate with equal spacing. The metal patch is printed between the first and second dielectric layers and is I-shaped.

[0049] The first and second dielectric layers have the same structure, both made of F4B board material with a relative permittivity of 2.2 and a loss tangent of 0.0015, forming a cuboid with a length of 5mm, a width of 5mm, and a height of 2mm.

[0050] The first metal grating layer consists of three identical metal sheets, which are arranged uniformly along the x-axis with a spacing of 1 mm between each pair of sheets.

[0051] The second metal grating layer consists of three identical metal sheets arranged uniformly along the y-axis, with a spacing of 1 mm between each pair of sheets.

[0052] Figure 3 This is a top view of the metal patch in the electromagnetic metasurface unit.

[0053] The metal patch has an opening size of... The angle between the central axis and the x-axis is An I-shaped patch with an opening. The range of values ​​is , The range of values ​​is .

[0054] The method for drawing the transmission phase table of the electromagnetic metasurface unit is as follows: keep the rotation angle of the metal patch constant, perform simulation when the opening angle of the metal patch changes, obtain the transmission phase corresponding to each value of the opening angle of the metal patch, and draw a transmission phase table for each value of the opening angle of the metal patch and its corresponding transmission phase.

[0055] The method for drawing the transmission amplitude table of the electromagnetic metasurface unit is as follows: Keep the opening angle of the metal patch constant, perform simulation when the rotation angle of the metal patch changes, obtain the transmission amplitude corresponding to each value of the rotation angle of the metal patch, and draw a transmission amplitude table for each value of the rotation angle of the metal patch and its corresponding transmission amplitude.

[0056] Step 6: Adjust the state of each unit of the electromagnetic metasurface according to the required control amplitude and compensation phase of each unit to obtain the electromagnetic metasurface.

[0057] The steps for adjusting the state of each unit of the electromagnetic metasurface are as follows:

[0058] The first step is to find the opening angle of the metal patch corresponding to the compensation phase of each unit of the electromagnetic metasurface from the transmission phase table, and adjust the opening angle of the metal patch of each unit of the electromagnetic metasurface accordingly.

[0059] The second step is to find the rotation angle of the metal patch corresponding to the control amplitude of each unit of the electromagnetic metasurface from the transmission amplitude table, and adjust the rotation angle of the metal patch of each unit of the electromagnetic metasurface accordingly.

[0060] Step 7: Place the electromagnetic metasurface and the feed horn at the set positions, and apply an radio frequency signal to the feed horn to generate a quasi-diffraction-free Pilsner vortex beam with adjustable focal length.

[0061] The technical effects of the present invention will be further explained below in conjunction with simulation experiments and sampling results analysis.

[0062] 1. Simulation experimental conditions:

[0063] The hardware platform for the simulation experiment of this invention is: Intel(R) Core(TM) i7-10700 CPU with a main frequency of 2.90GHz and 16GB of memory.

[0064] The software platform for the simulation experiments of this invention is: Windows 10 operating system, Ansys HFSS 2021 and MATLAB R2020b.

[0065] The parameters for the simulation experiment of this invention are set as follows: the focal point of the quasi-diffraction-free Pilsier vortex beam is set to... OAM mode of quasi-diffraction-free Pilsey vortex beam. The electromagnetic metasurface that generates the quasi-diffraction-free Pilsier beam is located in the xoy plane of the Cartesian coordinate system, and the operating frequency of the electromagnetic metasurface is set to... The operating wavelength is The electromagnetic metasurface is composed of 60 rows and 60 columns of units, with a row spacing of 5 mm and a column spacing of 5 mm between each pair of units. The coordinates of the feed horn in the Cartesian coordinate system are set as follows: .

[0066] 2. Simulation content and result analysis:

[0067] The simulation experiment of this invention uses the method proposed in this invention, and calculates the focus using the simulation software MATLAB R2020b. The compensated phase diagram and modulated amplitude diagram required for time-accurate diffraction-free Pilsey vortex beams. The compensated phase diagram is as follows: Figure 4 As shown, the horizontal axis represents the position coordinate of the element in the x-direction, the vertical axis represents the position coordinate of the element in the y-direction, and the phase is distributed at 0°. Within 360°. Adjustment range as follows: Figure 5 As shown, the horizontal axis represents the position coordinate of the unit in the x-direction, the vertical axis represents the position coordinate of the unit in the y-direction, and the amplitude distribution is between 0 and 1. Between 1 and 2.

[0068] By using the Ansys HFSS 2021 simulation software to perform RF excitation on the feed horn and adding an observation surface along the beam propagation direction, the electric field intensity distribution of the beam can be obtained, such as... Figure 6 As shown. At focus By adding a 300mm × 300mm observation surface, the electric field intensity and electric field phase distribution at the beam focal point can be obtained, such as... Figure 7 and Figure 8 As shown.

[0069] The following is combined with Figure 6 , Figure 7 and Figure 8The effects of the present invention will be further described.

[0070] Figure 6 This is a diagram of the electric field intensity along the propagation direction of a quasi-diffraction-free Pilsner vortex beam in the simulation experiment of this invention, where the side axis represents the magnitude of the electric field intensity. From Figure 6 As can be seen, this invention successfully generated a quasi-diffraction-free vortex beam, and the generated beam is at the focal point. The presence of a region with strong electric field energy indicates that the designed beam has the characteristic of non-diffraction focusing within a certain transmission distance near the focal point, and the beam effect is good.

[0071] Figure 7 In the simulation experiment of this invention, at the focal point of the quasi-diffraction-free Pilsier vortex beam... An electric field intensity diagram on a 300mm × 300mm observation surface, where the lateral axis represents the magnitude of the electric field intensity. From Figure 7 As can be seen, the electric field intensity on the observation surface exhibits a circular field intensity distribution, which is consistent with the characteristics of a vortex beam.

[0072] Figure 8 This is the focus of the quasi-diffraction-free Pilsier vortex beam in the simulation experiment of this invention. An electric field phase diagram on a 300mm × 300mm observation surface, where the side axis represents the phase value of the electric field. From Figure 8 As can be seen, the electric field phase on the observation surface exhibits a spiral shape, indicating that the present invention has successfully generated the OAM mode. Quasi-diffraction-free Pilsey vortex beam.

[0073] The above simulation analysis demonstrates that the method of this invention can be used to generate quasi-diffraction-free Pilsier vortex beams.

Claims

1. A method for generating quasi-diffraction-free Pilsier vortex beams based on electromagnetic metasurfaces, characterized in that, The phase and amplitude required for quasi-diffraction-free Pilscher vortex beams with different focal points are compensated by designing electromagnetic metasurfaces. The steps for generating such quasi-diffraction-free Pilscher vortex beams are as follows: Step 1: Calculate the focus adjustment factor based on the focus of the quasi-diffraction-free Pilssie vortex beam to be generated; Step 2: Set the scale of the electromagnetic metasurface, the spacing of the electromagnetic metasurface units, the OAM mode of the quasi-diffraction-free Pilssie vortex beam, and the position of the feed horn. Step 3: Calculate the Pilsier integral for each unit of the electromagnetic metasurface based on the focus adjustment factor; Step 4: Calculate the required modulation amplitude and compensation phase for each unit of the electromagnetic metasurface based on the Pierce integral of the coordinates of each unit. Step 5: Design the electromagnetic metasurface unit and draw the transmission phase table and transmission amplitude table of the electromagnetic metasurface unit; Step 6: Adjust the state of each unit of the electromagnetic metasurface according to the required control amplitude and compensation phase of each unit to obtain the electromagnetic metasurface; Step 7: Place the electromagnetic metasurface and the feed horn at the set position, and apply an radio frequency signal to the feed horn to generate a quasi-diffraction-free Pilsner vortex beam with a configurable focal length.

2. The method for generating quasi-diffraction-free Pilsey vortex beams based on electromagnetic metasurfaces according to claim 1, characterized in that, The focus adjustment factor mentioned in step 1 is obtained by the following formula: ， in, This represents the focus adjustment factor obtained based on the focus of the quasi-diffraction-free Pilsier vortex beam to be generated. This represents the focal point of the quasi-diffraction-free Pilsier vortex beam to be generated, where π represents the mathematical constant pi. This indicates the operating wavelength of the electromagnetic metasurface.

3. The method for generating quasi-diffraction-free Pilsier vortex beams based on electromagnetic metasurfaces according to claim 2, characterized in that, The settings for the scale of the electromagnetic metasurface, the spacing between the electromagnetic metasurface units, the OAM mode of the quasi-diffraction-free Pilscher vortex beam, and the position of the feed horn, as described in step 2, are all determined and generated in the xoy plane of the Cartesian coordinate system. Specifically, the electromagnetic metasurface generating the quasi-diffraction-free Pilscher vortex beam is composed of M rows and N columns of units, where M ≥ 10, N ≥ 10, and the row spacing between any two units is d. M , The column spacing between any two cells is d. N , The OAM mode of the quasi-diffraction-free Pilsey vortex beam is set as follows: l is any integer value, and the coordinates of the feed horn in the Cartesian coordinate system are set as follows: M×d M ≤ ≤1.5M×d M .

4. The method for generating quasi-diffraction-free Pilsey vortex beams based on electromagnetic metasurfaces according to claim 3, characterized in that, The calculation of the Pilsier integral for each element of the electromagnetic metasurface in step 3 is obtained by the following formula: ， in, Represent the Pilsier integral of the m-th row and n-th column element in the electromagnetic metasurface. , , Let represent the coordinates of the center of the cell in the m-th row and n-th column in the planar coordinate system, exp(.) represents the exponential operation with the natural constant e as the base, j represents the imaginary unit, and s represents the characteristic parameter of the Pirsey integral function. This represents the radius of the central region of the quasi-diffraction-free Pilsey vortex beam. .

5. The method for generating quasi-diffraction-free Pilsey vortex beams based on electromagnetic metasurfaces according to claim 4, characterized in that, The compensation phase required for each element of the electromagnetic metasurface, as described in step 4, is obtained by the following formula: ， in, This represents the compensation phase required for the m-th row and n-th column element in the electromagnetic metasurface. (.) indicates the operation of taking the complex argument. Indicates that it is located at The azimuth angle of the electromagnetic metasurface unit relative to the origin.

6. The method for generating quasi-diffraction-free Pilsey vortex beams based on electromagnetic metasurfaces according to claim 4, characterized in that, The required modulation amplitude for each unit of the electromagnetic metasurface, as described in step 4, is obtained from the following formula: ， in, This represents the required modulation amplitude for the m-th row and n-th column cell in the electromagnetic metasurface. (.) indicates the operation of taking the modulus of a complex number.

7. The method for generating quasi-diffraction-free Pilsier vortex beams based on electromagnetic metasurfaces according to claim 1, characterized in that, In step 5, designing the electromagnetic metasurface unit means that each electromagnetic metasurface unit has the same structure except for the metal patch. Each electromagnetic metasurface unit includes a first metal grating layer, a second metal grating layer, a metal patch, a first dielectric layer, and a second dielectric layer. The first and second dielectric layers are cuboids of equal volume and shape. The first and second metal grating layers are printed at the top and bottom ends of the first and second dielectric layers, respectively. The first metal grating consists of three square metal sheets of the same size and equidistant from each other, arranged parallel to each other along the x-axis of the substrate. The second metal grating consists of three square metal sheets of the same size and equidistant from each other, arranged parallel to each other along the y-axis of the substrate. The metal patch is printed between the first and second dielectric layers. The shape of the metal patch can be either an open annular shape or an I-shape. The opening angle of the metal patch is used to control the transmission phase of the electromagnetic metasurface unit, and the rotation angle of the metal patch is used to control the transmission amplitude of the electromagnetic metasurface unit.

8. The method for generating quasi-diffraction-free Pilsier vortex beams based on electromagnetic metasurfaces according to claim 1, characterized in that, The method for drawing the transmission phase table of the electromagnetic metasurface unit in step 5 is as follows: Keep the rotation angle of the metal patch constant, perform simulation when the opening angle of the metal patch changes, obtain the transmission phase corresponding to each value of the opening angle of the metal patch, and draw a transmission phase table for each value of the opening angle of the metal patch and its corresponding transmission phase.

9. The method for generating quasi-diffraction-free Pilsier vortex beams based on electromagnetic metasurfaces according to claim 1, characterized in that, The method for drawing the transmission amplitude table of the electromagnetic metasurface unit in step 5 is as follows: Keep the opening angle of the metal patch unchanged, perform simulation when the rotation angle of the metal patch changes, obtain the transmission amplitude corresponding to each value of the rotation angle of the metal patch, and draw a transmission amplitude table for each value of the rotation angle of the metal patch and its corresponding transmission amplitude.

10. The method for generating quasi-diffraction-free Pilsier vortex beams based on electromagnetic metasurfaces according to claim 1, characterized in that, The steps for adjusting the state of each unit of the electromagnetic metasurface in step 6 are as follows: The first step is to find the opening angle of the metal patch corresponding to the compensation phase of each unit of the electromagnetic metasurface from the transmission phase table, and adjust the opening angle of the metal patch of each unit of the electromagnetic metasurface accordingly. The second step is to find the rotation angle of the metal patch corresponding to the control amplitude of each unit of the electromagnetic metasurface from the transmission amplitude table, and adjust the rotation angle of the metal patch of each unit of the electromagnetic metasurface accordingly.

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