Programmable Transmissive Metasurface for Multi-Beam Multi-Mode OAM

Abstract

A programmable transmissive metasurface unit with multi-beam multi-modal OAM is provided, which includes four layers of metal patches, two layers of dielectric substrates and one layer of connection layer; looking from top to bottom along the Z-axis direction, the whole unit is successively: receiving layer, the first layer of dielectric substrate, bias layer, connection layer, metal ground plane, the second layer of dielectric substrate, radiation layer; among them, the receiving layer, bias layer, metal ground plane and radiation layer are all metal layers. By performing an m×n periodic array on the above unit, a programmable transmissive metasurface array with multi-beam multi-modal OAM is formed. The programmable transmissive metasurface of the present invention can realize multiple functions such as dual-beam multi-modal OAM, dual-beam OAM independent beam scanning, dual-beam OAM simultaneous beam scanning and dual-beam OAM coverage beam scanning, and has very important application value in multi-target radar detection systems and multi-platform communication systems, etc.

Description

Technical Field

[0001] The present invention relates to the design technology of programmable transmissive metasurfaces, and particularly to a programmable transmissive metasurface with multi-beam and multi-modal OAM. Background Art

[0002] In the field of microwave communication, the vortex electromagnetic wave beam carrying orbital angular momentum (OAM) carries a helical phase factor In theory, there are infinitely many modes, and the OAMs of different modes are orthogonal to each other. Therefore, the OAM of each mode can be used as an independent transmission channel for communication, which provides a basis for realizing secure wireless communication and expanding communication capacity. Electromagnetic metasurface is a two-dimensional planar structure of a class of three-dimensional electromagnetic metamaterials, with the characteristics of low loss, small size, easy processing, etc. Since it can change the transmission phase, amplitude, polarization and other characteristics of electromagnetic waves at sub-wavelength scales, it has broad application prospects in manipulating electromagnetic waves. With the rapid development of metasurfaces, in 2014, the team of Academician Tiejun Cui proposed a new type of metasurface - electromagnetic coding and programmable metasurface (T.J. Cui, M.Q. Qi, X. Wan, et al., Coding metamaterials, digital metamaterials and programmable metamaterials[J]. Light Science&Applications, 2014, 3: e218.), in which the reflection and transmission phases of its unit are represented by a finite number of binary values to represent the phase distribution of "0" and "1" digital-state electromagnetic waves, providing great design convenience for the generation of OAM. Based on the digital transmission metasurface, multi-beam multi-mode OAM generation can be achieved simultaneously in the terahertz band (H. Zhao, B.G. Quan, X.K. Wang, et al. Demonstration of Orbital Angular Momentum Multiplexing and Demultiplexing Based on a Metasurface in the Terahertz Band[J]. ACS Photonics 2018, 5(5): 1726-1732.), giving full play to the advantages of spatial division multiplexing and mode division multiplexing methods to expand the transmission channel, and having important application value in wireless communication systems. To overcome the problem of real-time control of electromagnetic waves, a programmable transmission metasurface designed by combining a metal ring structure with PIN diodes (X.D. Bai, F.W. Kong, Y.T. Sun, et al., High-Efficiency Transmissive Programmable Metasurface for Multimode OAM Generation[J]. Advanced Optical Materials, 2020, 8(17): 2000570.) controls the on and off states of the loaded PIN diodes through a programmable gate array (FPGA) hardware system, inputs the code into the metasurface, and realizes the real-time regulation of the OAM mode of a single beam, breaking the defect of the fixed function of traditional transmission metasurfaces.Through comprehensive analysis of the above research results, most of the traditional transmissive metasurfaces that generate multi-beam multi-modal OAM are difficult to meet the application requirements of real-time regulation. Even the existing programmable transmissive metasurfaces only achieve the mode switching of single-beam OAM and do not achieve the real-time control of multi-beam multi-modal OAM simultaneously, resulting in the single function of the designed transmissive metasurfaces. In the fields of multi-target detection systems and multi-channel wireless communications, realizing the OAM and beam scanning functions of multi-beam multi-modal has urgent military communication application requirements and important academic value for its research. Summary of the Invention

[0003] Aiming at the problems existing in the prior art, the present invention provides a programmable transmissive metasurface unit for multi-beam multi-modal OAM, hereinafter simply referred to as "unit", which includes four layers of metal patches, two layers of dielectric substrates and one layer of connection layer; when looking at the whole unit along the Z-axis direction from top to bottom in turn: receiving layer, the first layer of dielectric substrate, bias layer, connection layer, metal ground plane, the second layer of dielectric substrate, radiation layer; among them, the receiving layer, bias layer, metal ground plane and radiation layer are all metal layers; the two layers of dielectric substrates and the connection layer are all dielectric plates; where

[0004] The two layers of dielectric substrates and the connection layer are in the shape of a thin cuboid, with square upper and lower surfaces. The sizes of the two layers of dielectric substrates are exactly the same, and the projections of the two layers of dielectric substrates and the connection layer on the horizontal plane coincide; the side lengths of the two layers of dielectric substrates and the connection layer are all L, and L is the period length of the unit;

[0005] The metal patches of the receiving layer are attached to the upper surface of the first layer of dielectric substrate and are composed of the connection of the first rectangular ring metal patch and 5 rectangular metal patches, and the first rectangular ring metal patch and 5 rectangular metal patches are integrally formed; the first rectangular ring metal patch is located at the approximate center position of the upper surface of the first layer of dielectric substrate, and the four sides of the outer ring and the inner ring of the first rectangular ring metal patch are parallel to the four sides of the dielectric substrate; the 5 rectangular metal patches include 4 small rectangular metal patches and 1 large rectangular metal patch, and the sizes of the 4 small rectangular metal patches are exactly the same. The four sides of the 5 rectangular metal patches are parallel to the four sides of the dielectric substrate; the first and second small rectangular metal patches extend from the left side of the inner ring to the right and are symmetric about the horizontal axis of symmetry of the receiving layer metal patch. There is a certain distance between the first and second small rectangular metal patches and between them and the upper and lower sides of the inner ring; the third and fourth small rectangular metal patches extend from the right side of the inner ring to the left and are symmetric with the first and second small rectangular metal patches about the vertical axis of symmetry of the receiving layer metal patch respectively. The parameters of these 4 small rectangular metal patches are exactly the same; the large rectangular metal patch extends upward from the lower side of the inner ring and is symmetric about the vertical axis of symmetry of the receiving layer metal patch;

[0006] Three metallized vias with a radius of Ra are drilled in the first-layer dielectric substrate along the direction perpendicular to the upper and lower surfaces of the dielectric substrate. The first and second metallized vias are respectively located on the metal strips on the left and right sides of the rectangular ring metal patch of the receiving layer, penetrating from the receiving layer metal patch through to the bias layer metal patch from top to bottom to connect the two. The heights of the first and second metallized vias are Sh. The third metallized via is located at the center of the entire receiving layer metal patch, penetrating from the receiving layer metal patch through to the radiation layer metal patch from top to bottom to connect the two.

[0007] The three metallized vias in the second-layer dielectric substrate have the same parameters and corresponding positions as the metallized vias in the first-layer dielectric substrate. The metallized vias corresponding to the positions of the first and second metallized vias are respectively named the fourth and fifth metallized vias. The fourth and fifth metallized vias penetrate from the metal ground plane through to the radiation layer metal patch to connect the two. The metallized via in the middle position is the third metallized via.

[0008] There is only one metallized via in the connection layer, located in the middle position, which is the third metallized via.

[0009] The bias layer metal patch is attached to the lower surface of the first-layer dielectric substrate and is composed of 2 rectangular metal patches and a bias line. The four sides of the 2 rectangular metal patches are all parallel to the four sides of the dielectric substrate, and the extension direction of the bias line is also parallel to the four sides of the dielectric substrate. The first rectangular metal patch is located in the left half of the lower surface of the first-layer dielectric substrate, and its four sides are all at a certain distance from the four sides of the dielectric substrate. It is symmetric about the X-axis direction symmetry axis of the lower surface of the first-layer dielectric substrate, and its length direction is parallel to the Y-axis. The second rectangular metal patch is located in the right half of the lower surface of the first-layer dielectric substrate, symmetric with the first rectangular metal patch about the Y-axis direction symmetry axis of the lower surface of the first-layer dielectric substrate, and at a certain distance from the first rectangular metal patch. The parameters of the first and second rectangular metal patches are exactly the same, and the distance between them is I. The bias line is connected by 7 segments of rectangular metal wires. The first segment extends a certain length to the left starting from the center of the left long side of the first rectangular metal patch; then it extends vertically downward for a certain length to form the second segment; then it extends to the right to form the third segment; the fourth segment extends a certain length to the right starting from the center of the right long side of the second rectangular metal patch; then it extends vertically downward for a certain length to form the fifth segment; the lower end of the fifth segment is connected to the rightmost end of the third segment; it extends downward for a certain length from the Y-axis direction symmetry axis on the third segment on the lower surface of the first-layer dielectric substrate to form the sixth segment; then it extends to the left until it reaches the left edge of the lower surface of the first-layer dielectric substrate to form the seventh segment; the first, third, fourth, and seventh segments are all parallel to the X-axis, and the second, fifth, and sixth segments are all parallel to the Y-axis.

[0010] The metal ground plane is a square thin layer with a side length of L, that is, the metal thin layer completely covers the lower surface of the connection layer; a circular hole is etched at the center position of the metal ground plane, and this circular hole needs to ensure that the third metallization via does not short-circuit with the metal ground plane. This circular hole is used for the metal through-hole that connects the receiving layer and the radiation layer;

[0011] The radiation layer metal patch is attached to the lower surface of the second dielectric substrate and consists of a "hui"-shaped metal patch with protrusions and two PIN diodes; the "hui"-shaped metal patch includes a second rectangular ring metal patch and six rectangular metal patches; the second rectangular ring metal patch and the six rectangular metal patches are integrally formed; the second rectangular ring metal patch is located at approximately the center position of the lower surface of the second dielectric substrate, and the four sides of the outer ring and the inner ring of the second rectangular ring metal patch are parallel to the four sides of the dielectric substrate; the six rectangular metal patches include four large rectangular metal patches and two small rectangular metal patches, the four large rectangular metal patches are of exactly the same size, and the four sides of the six rectangular metal patches are parallel to the four sides of the dielectric substrate; the 11th and 12th large rectangular metal patches extend from the left side of the inner ring to the right and are horizontally symmetric about the axis of symmetry of the radiation layer metal patch, and there is a certain distance between the 11th and 12th large rectangular metal patches and between them and the upper and lower sides of the inner ring; the 13th and 14th large rectangular metal patches extend from the right side of the inner ring to the left and are symmetric with the 11th and 12th large rectangular metal patches about the vertical axis of symmetry of the radiation layer metal patch respectively, and the parameters of these four large rectangular metal patches are exactly the same; the 15th small rectangular metal patch extends downward from the upper side of the inner ring and is vertically symmetric about the axis of symmetry of the radiation layer metal patch, and there is a certain distance between the 15th small rectangular metal patch and the left and right sides of the inner ring; the 16th small rectangular metal patch extends upward from the lower side of the inner ring and is symmetric with the 15th small rectangular metal patch about the horizontal axis of symmetry of the radiation layer metal patch, and the parameters of these two small rectangular metal patches are exactly the same; the positions of the four large rectangular metal patches in the radiation layer are approximately the same as those of the four small rectangular metal patches in the receiving layer, the distance between the 11th and 12th large rectangular metal patches is L3, the parameters of these four large rectangular metal patches are exactly the same, the length of each is L1, and the width of each is L2; the four sides of the inner ring and the outer ring of the second rectangular ring metal patch are parallel to the four sides of the dielectric substrate, and its center coincides with the center of the dielectric plate; one independent "No. 1" battery-shaped metal patch is located at the center of the "hui"-shaped metal patch, and its four sides are parallel to the four sides of the dielectric substrate; the "No. 1" battery-shaped metal patch includes a square patch and two small rectangular patches; the square patch is exactly at the center of the "hui"-shaped metal patch, the 17th small rectangular patch extends upward from the upper side of the square patch and is vertically symmetric about the axis of symmetry of the radiation layer metal patch; the 18th small rectangular metal patch extends downward from the lower side of the square patch and is vertically symmetric about the axis of symmetry of the radiation layer metal patch; there is a certain distance between the 17th and 15th small rectangular metal patches and between the 18th and 16th small rectangular metal patches; its side length is Ts; the two loaded PIN diodes include an upper PIN diode I and a lower PIN diode II, both arranged in the direction of "positive pole on top, negative pole on bottom", the upper PIN diode I is connected between the 17th and 15th small rectangular metal patches, and the lower PIN diode II is connected between the 18th and 16th small rectangular metal patches.

[0012] In one embodiment of the present invention, the side length L of the two-layer dielectric substrate and the connection layer ranges from 5 to 15 mm; the thickness Sh of the two-layer dielectric substrate ranges from 1 to 3 mm; the thickness Mh of the connection layer ranges from 0.05 to 0.25 mm, and the dielectric constant ranges from 2.0 to 4.4.

[0013] In a specific embodiment of the present invention, the side length L of the two-layer dielectric substrate and the connection layer is 10 mm; the thickness Sh of the two-layer dielectric substrate is 1.52 mm; the thickness Mh of the connection layer is 0.1 mm, the dielectric constant of the dielectric substrate is 3.55, and the dielectric constant of the connection layer is 3.3.

[0014] In another embodiment of the present invention,

[0015] In the receiving layer metal patch, the outer ring length TL of the first rectangular ring metal patch ranges from 5 to 8 mm, the outer ring width T LW ranges from 5 to 6 mm, and the annular width Tc ranges from 0.5 to 1 mm;

[0016] In the receiving layer metal patch, the length e1 of the 4 small rectangular metal patches in the X-axis direction ranges from 1 to 2 mm, and the width e2 in the Y-axis direction ranges from 0.5 to 1 mm; the distance e3 between the first and second small rectangular metal patches in the Y-axis direction ranges from 1 to 2 mm;

[0017] The length gl of the large rectangular metal patch in the Y-axis direction ranges from 2 to 4.5 mm, and the width gw in the X-axis direction ranges from 0.5 to 2 mm.

[0018] In another specific embodiment of the present invention,

[0019] In the receiving layer metal patch, the outer ring length TL of the first rectangular ring metal patch is 6.4 mm, the outer ring width T LW is 5.8 mm, and the annular width Tc is 0.8 mm;

[0020] In the receiving layer metal patch, the length e1 of the 4 small rectangular metal patches in the X-axis direction is 1.6 mm, and the width e2 in the Y-axis direction is 0.6 mm; the distance e3 between the first and second small rectangular metal patches in the Y-axis direction is 1.2 mm;

[0021] The length gl of the large rectangular metal patch in the Y-axis direction is 3.1 mm, and the width gw in the X-axis direction is 0.9 mm.

[0022] In yet another embodiment of the present invention,

[0023] In the bias layer metal patch, the lengths bl of the first and second rectangular metal patches are in the range of 3 - 6 mm, the widths bw are in the range of 1.3 - 2 mm, and the distance I between them is in the range of 4 - 8 mm;

[0024] For the first, fourth, sixth, and seventh rectangular metal wires, the lengths w1 are in the range of 0.1 - 0.5 mm; for the second and fifth rectangular metal wires, the lengths w2 are in the range of 2 - 5 mm; for the third rectangular metal wire, the length (I + 2 * bw + 2 * w1) is in the range of 8 - 9 mm; for the sixth rectangular metal wire, the length w3 is in the range of 0.05 - 0.25 mm; for the seventh rectangular metal wire, the length (L / 2 + 0.05 mm) is in the range of 4.5 - 5.5 mm.

[0025] In yet another specific embodiment of the present invention,

[0026] In the bias layer metal patch, the lengths bl of the first and second rectangular metal patches are 5 mm, the widths bw are 1.4 mm, and the distance I between them is 5 mm;

[0027] The width of each rectangular metal wire is 0.1 mm. For the first and fourth rectangular metal wires, the length w1 is 0.3 mm; for the second and fifth rectangular metal wires, the length w2 is 3 mm; for the third rectangular metal wire, the length (I + 2 * bw + 2 * w1) is 8.4 mm; for the sixth rectangular metal wire, the length w3 is 0.1 mm; for the seventh rectangular metal wire, the length (L / 2 + 0.05 mm) is 5.05 mm.

[0028] In yet another embodiment of the present invention,

[0029] In the radiation layer metal patch, the distance L3 between the 11th and 12th large rectangular metal patches is in the range of 1 - 2 mm, the lengths L1 of these 4 large rectangular metal patches are in the range of 0.5 - 2 mm, and the widths L2 are in the range of 0.25 - 0.8 mm;

[0030] For the second rectangular ring metal patch, the outer ring side length TL is in the range of 5 - 8 mm; the left and right side widths Tc are in the range of 0.5 - 1 mm, and the upper and lower side widths Tb are in the range of 0.6 - 1.5 mm;

[0031] In the "1" - shaped battery - type metal patch, the side length Ts of the square patch is in the range of 0.5 - 1.5 mm.

[0032] In yet another specific embodiment of the present invention,

[0033] In the radiation layer metal patch, the distance L3 between the 11th and 12th large rectangular metal patches is 1.6 mm, the lengths L1 of these 4 large rectangular metal patches are 1 mm, and the widths L2 are 0.6 mm;

[0034] The outer side length TL of the outer ring of the second rectangular ring metal patch is 6.4 mm; the width Tc of the left and right sides of the second rectangular ring metal patch is 0.8 mm, and the width Tb of the upper and lower sides is 1.1 mm;

[0035] The "No. 1" battery-type metal patch is formed by integrating a square patch and two small rectangular patches; among them, the side length Ts of the square patch is 1 mm;

[0036] The PIN diode model is SMP1340-040LF.

[0037] There is also provided a method of forming an m×n periodic array by grouping the programmable transmissive metasurface units of the above multi-beam multi-modal OAM, where the ranges of m and n are 2-100.

[0038] In view of the existing requirements, the present invention is for flexibly and real-time programming and controlling transmitted electromagnetic waves to achieve various specific functions. The programmable transmissive metasurface of the present invention can achieve multiple functions such as dual-beam multi-modal OAM, dual-beam OAM independent beam scanning, dual-beam OAM simultaneous beam scanning, and dual-beam OAM covering beam scanning, and has important application values in multi-target radar detection systems and multi-platform communication systems, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 The schematic diagram of the unit of the programmable transmissive metasurface proposed by the present invention and the schematic diagram of the metal patch structure of each layer are shown, where Figure 1 (a) shows the three-dimensional perspective view of the programmable transmissive metasurface unit, Figure 1 (b) shows the side view of its unit, Figure 1 (c) shows the schematic diagram of the metal patch structure of the receiving layer of the programmable transmissive metasurface unit, Figure 1 (d) shows the schematic diagram of the metal patch structure of the radiation layer of the programmable transmissive metasurface unit, Figure 1 (e) shows the schematic diagram of the metal patch structure of the bias layer of the programmable transmissive metasurface unit.

[0040] Figure 2 The transmission amplitude and phase response result diagrams of the "0" unit and the "π" unit when the linearly polarized wave is incident along the +z axis direction on the programmable transmissive metasurface unit proposed by the present invention are shown; where Figure 2 (a) is the co-polarized and cross-polarized transmission amplitude curves of the "0" unit and the "π" unit when the y-polarized wave is incident, Figure 2 (b) are the two transmission phase curves and the corresponding phase difference curve when the y-polarized wave incident along the +z axis direction passes through the "0" unit and the "π" unit.

[0041] Figure 3Shows the simulation effect diagram of the programmable transmissive metasurface system proposed by the present invention to achieve the dual-beam multi-modal OAM function under the excitation of an on-line polarized horn antenna, where Figure 3 (a) and (b) are respectively the coded phase distribution diagram designed to generate the +1 mode dual-beam OAM and the simulated three-dimensional radiation pattern. Figure 3 (c) and (d) are respectively the coded phase distribution diagram designed to generate the +2 mode dual-beam OAM and the simulated three-dimensional radiation pattern.

[0042] Figure 4 Shows the simulation effect diagram of the programmable transmissive metasurface system proposed by the present invention to achieve the beam simultaneous scanning function of dual-beam OAM under the excitation of an on-line polarized horn antenna, where Figure 4 (a), (b), and (c) are respectively the coded phase distribution diagrams designed to generate the +1 mode dual-beam OAM at the scanning angles of -10° / 10°, -30° / 30°, and -50° / 50°. Figure 4 (d) is the two-dimensional pattern obtained by simulating the implementation of the dual-beam OAM beam scanning function.

[0043] Figure 5 Shows the simulation effect diagram of the programmable transmissive metasurface system proposed by the present invention to achieve the independent beam scanning function of dual-beam OAM under the excitation of an on-line polarized horn antenna, where Figure 5 (a), (b), and (c) are respectively the coded phase distribution diagrams designed to generate the +1 mode dual-beam OAM at the scanning angles of -10° / 30°, -30° / 30° - 50° / 30°. Figure 5 (d) is the two-dimensional pattern obtained by simulating the implementation of the asymmetric beam scanning function of dual-beam OAM.

[0044] Figure 6 Shows the simulation effect diagram of the programmable transmissive metasurface system proposed by the present invention to achieve the coverage scanning function of dual-beam OAM under the excitation of an on-line polarized horn antenna, where Figure 6 (a) and (b) are respectively the coded phase distribution diagram and the simulated three-dimensional radiation pattern of the +1 mode dual-beam OAM with a beam divergence angle of 60° at the scanning angle of 20°. Figure 6 (c) and (d) are respectively the coded phase distribution diagram and the simulated three-dimensional radiation pattern of the +1 mode dual-beam OAM with a beam divergence angle of 60° at the scanning angle of -20°.

[0045] Figure 7 Shows the overall detailed schematic diagram of the programmable transmissive metasurface array and the processed sample in the test of the present invention, where Figure 7 (a) is the test environment diagram of the programmable metasurface system in the microwave anechoic chamber. Figure 7(b) is the overall layout diagram of the programmable metasurface system array and the detailed schematic diagram of the feeder.

[0046] Figure 8 Shows the multifunctional test result diagram of the programmable transmissive metasurface system proposed by the present invention in the microwave anechoic chamber, where Figure 8 (a) is the two-dimensional pattern of the +1 mode OAM far-field test result, Figure 8 (b) is the two-dimensional pattern of the +2 mode OAM far-field test result, Figure 8 (c) is the two-dimensional far-field pattern of the dual-beam OAM simultaneous scanning function test result, Figure 8 (d) The two-dimensional far-field pattern of the dual-beam OAM independent scanning function test result. Detailed implementation manner

[0047] The present invention proposes a programmable transmissive metasurface with multi-beam and multi-mode OAM. The three-dimensional perspective view of the metasurface unit (hereinafter simply referred to as "unit") is as shown in Figure 1 (a), and the side view of the unit. As shown in Figure 1 (b). The unit is mainly composed of four layers of metal patches, two layers of dielectric substrates and one layer of connection layer. Looking at the whole unit along the Z-axis direction from top to bottom in turn are: receiving layer, the first layer of dielectric substrate, bias layer, connection layer, metal ground plane, the second layer of dielectric substrate, radiation layer. Among them, the receiving layer, bias layer, metal ground plane and radiation layer are all metal layers. The two layers of dielectric substrates and the connection layer are all dielectric plates.

[0048] Specifically as follows:

[0049] The two layers of dielectric substrates and the connection layer are in the shape of a thin cuboid, with both the upper and lower surfaces being square. The sizes of the two layers of dielectric substrates are exactly the same, and the projections of the two layers of dielectric substrates and the connection layer on the horizontal plane coincide. The side lengths of the two layers of dielectric substrates and the connection layer are all L, where L is the period length of the unit. The side length L is in the range of 5 - 15 mm, and the preferred value is 10 mm; the thickness Sh of the two layers of dielectric substrates is in the range of 1 - 3 mm, and the preferred value is 1.52 mm; the thickness Mh of the connection layer is in the range of 0.05 - 0.25 mm, and the preferred value is 0.1 mm, and the dielectric constant is in the range of 2.0 - 4.4. The preferred value of the dielectric substrate is 3.55, and the preferred value of the connection layer is 3.3.

[0050] As shown in Figure 1As shown in (c), the receiving layer metal patch is surface-mounted on the upper surface of the first dielectric substrate and is composed of the connection of the first rectangular ring metal patch and 5 rectangular metal patches, which are integrally formed. The first rectangular ring metal patch is located at the approximate center position of the upper surface of the first dielectric substrate. The four sides of the outer ring and the inner ring of the first rectangular ring metal patch are all parallel to the four sides of the dielectric substrate. The length of the outer ring is TL, and the length TL of the outer ring is in the range of 5 - 8 mm, with a preferred value of 6.4 mm. The width of the outer ring is T LW , and the width T LW is in the range of 5 - 6 mm, with a preferred value of 5.8 mm. The difference in side lengths between the outer ring and the inner ring, that is, the annular width, is Tc, and the annular width Tc is in the range of 0.5 - 1 mm, with a preferred value of 0.8 mm. The 5 rectangular metal patches include 4 small rectangular metal patches and 1 large rectangular metal patch. The 4 small rectangular metal patches have exactly the same size. The four sides of the 5 rectangular metal patches are all parallel to the four sides of the dielectric substrate. The first and second small rectangular metal patches extend from the left side of the inner ring to the right and are symmetric about the horizontal symmetry axis of the receiving layer metal patch (this symmetry axis is parallel to the X direction). There is a certain distance between the first and second small rectangular metal patches and between them and the upper and lower sides of the inner ring. The third and fourth small rectangular metal patches extend from the right side of the inner ring to the left and are symmetric about the vertical symmetry axis of the receiving layer metal patch (this symmetry axis is parallel to the Y direction) with respect to the first and second small rectangular metal patches respectively. The parameters of these 4 small rectangular metal patches are exactly the same. The length along the X-axis is e1, and the length e1 is in the range of 1 - 2 mm, with a preferred value of 1.6 mm. The width along the Y-axis is e2, and the width e2 is in the range of 0.5 - 1 mm, with a preferred value of 0.6 mm. The distance between the first and second small rectangular metal patches along the Y-axis is e3, and the distance e3 is in the range of 1 - 2 mm, with a preferred value of 1.2 mm. The large rectangular metal patch extends upward from the lower side of the inner ring and is symmetric about the vertical symmetry axis of the receiving layer metal patch (this symmetry axis is parallel to the X direction). Its length along the Y-axis is gl, and the length gl is in the range of 2 - 4.5 mm, with a preferred value of 3.1 mm. The width along the X-axis is gw, and the width gw is in the range of 0.5 - 2 mm, with a preferred value of 0.9 mm;

[0051] Three metallized vias with a radius of Ra are drilled in the first-layer dielectric substrate along the direction perpendicular to the upper and lower surfaces of the dielectric substrate. The radius Ra of the metallized vias ranges from 0.1 to 0.3 mm, and the preferred value is 0.25 mm. The first and second metallized vias are respectively located on the metal strips on the left and right sides of the rectangular ring metal patch of the receiving layer, and penetrate from the receiving layer metal patch to the bias layer metal patch from top to bottom to connect the two. The height of the first and second metallized vias is Sh; the third metallized via is located at the center of the entire receiving layer metal patch (this center is on the large rectangular metal patch), and penetrates from the receiving layer metal patch to the radiation layer metal patch from top to bottom to connect the two, and the height is (2*Sh + Mh).

[0052] The three metallized vias in the second-layer dielectric substrate have the same parameters and corresponding positions as the metallized vias in the first-layer dielectric substrate. The fourth and fifth metallized vias corresponding to the positions of the first and second metallized vias are respectively named. The fourth and fifth metallized vias penetrate from the metal ground plane to the radiation layer metal patch to connect the two. The metallized via in the middle position is the third metallized via.

[0053] There is only one metallized via in the connection layer, which is located in the middle position and is the third metallized via.

[0054] As Figure 1(As shown in (e), the bias layer metal patch is attached to the lower surface of the first dielectric substrate, and its surface is similar to a "capacitor" structure, which is composed of two rectangular metal patches and a bias line. The four sides of the two rectangular metal patches are all parallel to the four sides of the dielectric substrate, and the extending direction of the bias line is also parallel to the four sides of the dielectric substrate. The first rectangular metal patch is located in the left half of the lower surface of the first dielectric substrate. The four sides of the first rectangular metal patch maintain a certain distance from the four sides of the dielectric substrate. It is symmetric about the X-axis direction symmetry axis of the lower surface of the first dielectric substrate, and its length direction is parallel to the Y-axis. The second rectangular metal patch is located in the right half of the lower surface of the first dielectric substrate. It is symmetric with the first rectangular metal patch about the Y-axis direction symmetry axis of the lower surface of the first dielectric substrate and maintains a certain distance from the first rectangular metal patch. The parameters of the first and second rectangular metal patches are exactly the same. Their lengths are both bl, and the length bl ranges from 3 to 6 mm, with a preferred value of 5 mm. Their widths are both bw, and the width bw ranges from 1.3 to 2 mm, with a preferred value of 1.4 mm. The distance between them is I, and the distance I ranges from 4 to 8 mm, with a preferred value of 5 mm. The bias line is connected by 7 segments of rectangular metal wires. The first segment extends leftward from the center of the left long side of the first rectangular metal patch for a certain length; then it extends vertically downward for a certain length to form the second segment; then it extends rightward to form the third segment; the fourth segment extends rightward from the center of the right long side of the second rectangular metal patch for a certain length; then it extends vertically downward for a certain length to form the fifth segment; the lower end of the fifth segment is connected to the rightmost end of the third segment; it extends downward from the Y-axis direction symmetry axis on the lower surface of the first dielectric substrate of the third segment for a certain length to form the sixth segment; then it extends leftward until it reaches the left edge of the lower surface of the first dielectric substrate to form the seventh segment. The first, third, fourth, and seventh segments are all parallel to the X-axis, and the second, fifth, and sixth segments are all parallel to the Y-axis. The width of each segment of rectangular metal wire is 0.1 mm. The lengths of the first and fourth segments are both w1, and the length w1 ranges from 0.1 to 0.5 mm, with a preferred value of 0.3 mm; the lengths of the second and fifth segments are both w2, and the length w2 ranges from 2 to 5 mm, with a preferred value of 3 mm; the length of the third segment is (I + 2*bw + 2*w1), and the length (I + 2*bw + 2*w1) ranges from 8 to 9 mm, with a preferred value of 8.4 mm; the length of the sixth segment is w3, and the length w3 ranges from 0.05 to 0.25 mm, with a preferred value of 0.1 mm; the length of the seventh segment is (L / 2 + 0.05 mm), and the length (L / 2 + 0.05 mm) ranges from 4.5 to 5.5 mm, with a preferred value of 5.05 mm.)

[0055] The metal ground plane is a square thin layer with a side length of L, and L is the period length of the unit, that is, the metal thin layer completely covers the lower surface of the connection layer; a circular hole is etched at the center position of the metal ground plane. This circular hole needs to ensure that the third metallization via does not short-circuit with the metal ground plane, and this circular hole is used for the metal through-hole that penetrates the connection receiving layer and the radiation layer.)

[0056] such as Figure 1(As shown in (d)), the radiation layer metal patch is attached to the lower surface of the second dielectric substrate and is composed of a "hui"-shaped metal patch with protrusions and two PIN diodes. The "hui"-shaped metal patch includes a second rectangular ring metal patch and six rectangular metal patches. The second rectangular ring metal patch and the six rectangular metal patches are integrally formed. The second rectangular ring metal patch is located at the approximate center of the lower surface of the second dielectric substrate, and the four sides of the outer ring and the inner ring of the second rectangular ring metal patch are parallel to the four sides of the dielectric substrate. The six rectangular metal patches include four large rectangular metal patches and two small rectangular metal patches. The four large rectangular metal patches have exactly the same size. The four sides of the six rectangular metal patches are parallel to the four sides of the dielectric substrate. The 11th and 12th large rectangular metal patches extend from the left side of the inner ring to the right and are symmetric about the horizontal symmetry axis of the radiation layer metal patch (this symmetry axis is parallel to the X direction). There is a certain distance between the 11th and 12th large rectangular metal patches, and between them and the upper and lower sides of the inner ring. The 13th and 14th large rectangular metal patches extend from the right side of the inner ring to the left and are symmetric with the 11th and 12th large rectangular metal patches about the vertical symmetry axis of the radiation layer metal patch (this symmetry axis is parallel to the Y direction). The parameters of these four large rectangular metal patches are exactly the same. The 15th small rectangular metal patch extends from the upper side of the inner ring downward and is symmetric about the vertical symmetry axis of the radiation layer metal patch (this symmetry axis is parallel to the Y direction). There is a certain distance between the 15th small rectangular metal patch and the left and right sides of the inner ring. The 16th small rectangular metal patch extends from the lower side of the inner ring upward and is symmetric with the 15th small rectangular metal patch about the horizontal symmetry axis of the radiation layer metal patch (this symmetry axis is parallel to the X direction). The parameters of these two small rectangular metal patches are exactly the same. The positions of the four large rectangular metal patches in the radiation layer are approximately the same as those of the four small rectangular metal patches in the receiving layer. The distance L3 between the 11th and 12th large rectangular metal patches is in the range of 1 - 2 mm, and the preferred value is 1.6 mm. The parameters of these four large rectangular metal patches are exactly the same. The length of each is L1, and L1 is in the range of 0.5 - 2 mm, and the preferred value is 1 mm. The width of each is L2, and L2 is in the range of 0.25 - 0.8 mm, and the preferred value is 0.6 mm. In an embodiment of the present invention, the second rectangular ring metal patch is a square with an outer ring side length of TL. The outer ring side length TL is in the range of 5 - 8 mm, and the preferred value is 6.4 mm. The inner ring is rectangular. The four sides of the inner ring and the outer ring are parallel to the four sides of the dielectric substrate, and its center coincides with the center of the dielectric substrate. The width of the left and right sides of the second rectangular ring metal patch is Tc, and Tc is in the range of 0.5 - 1 mm, and the preferred value is 0.8 mm. The width of the upper and lower sides is Tb, and Tb is in the range of 0.6 - 1.5 mm, and the preferred value is 1.1 mm.One independent battery - type metal patch numbered "1" is located at the center of the "hui" - shaped metal patch, and its sides are all parallel to the four sides of the dielectric substrate; the battery - type metal patch numbered "1" consists of a square patch and two small rectangular patches, which are integrally formed; the square patch is exactly at the center of the "hui" - shaped metal patch, the 17th small rectangular patch extends upward from the upper side of the square patch and is symmetric about the vertical symmetry axis of the radiation - layer metal patch (this symmetry axis is parallel to the Y - direction); the 18th small rectangular metal patch extends downward from the lower side of the square patch and is symmetric about the vertical symmetry axis of the radiation - layer metal patch (this symmetry axis is parallel to the Y - direction); there is a certain distance between the 17th and the 15th small rectangular metal patches, and between the 18th and the 16th small rectangular metal patches; the side length of the square patch is Ts, and the side length Ts ranges from 0.5 - 1.5 mm, with a preferred value of 1 mm. The two loaded PIN diodes include the upper PIN diode I and the lower PIN diode II, both arranged in the direction of "positive on top, negative on the bottom". The upper PIN diode I is connected between the 17th and the 15th small rectangular metal patches, and the lower PIN diode II is connected between the 18th and the 16th small rectangular metal patches, for example, connected by welding respectively. In other words, the 15th, 16th, 17th, and 18th small rectangular metal patches exist for achieving a good welding effect. In an embodiment of the present invention, the PIN diode model is SMP1340 - 040LF, its size is 0.85×0.6 mm, the operating frequency is 9.4 GHz. When the PIN diode is turned on, it can be equivalent to a series structure of a resistor and an inductor, and its equivalent parameters are R = 1Ω, L = 450 pH. When the PIN diode is turned off, it can be equivalent to a series structure of a resistor, a capacitor, and an inductor, and its equivalent parameters are R = 10Ω, C = 0.086 pF, L = 450 pH; when PIN diode I is turned off and PIN diode II is turned on, it is marked as the "0" unit, and when PIN diode I is turned on and PIN diode II is turned off, it is denoted as the "π" unit.

[0057] The thickness of the four - layer metal patches of the programmable transmissive metasurface unit for multi - beam multi - mode OAM is in the range of 0.02 - 1 mm, and the preferred value is 0.035 mm.

[0058] The unit metal patches are etched on the dielectric substrate through printed circuit board (PCB) technology, and the dielectric substrates of each layer are tightly bonded together, for example, by lamination, to form an integral body.

[0059] Performing an m×n periodic array on the above - mentioned programmable transmissive metasurface unit to form a metasurface array. m and n can be selected from 2 - 100, and the preferred value is 32, that is, a square array is formed. The arraying method is well - known to those skilled in the art and will not be elaborated here.

[0060] The simulation software uses CST STUDIO SUITE 2020 to perform simulation calculations on the model under the boundary conditions of the Flouquet mode. First, the electromagnetic wave propagating vertically in the +z-axis direction is set to the linear polarization mode. Figure 2 (a) respectively shows the co-polarization and cross-polarization transmission amplitude curves of the "0" unit and the "π" unit when the y-polarized wave is incident, namely, the "0" unit_S11, the "π" unit_S11, the "0" unit_S21, and the "π" unit_S21. It can be seen from the figure that the co-polarization transmission amplitude |S11| is greater than -2 dB in the frequency band of 9 - 10.5 GHz. And the cross-polarization amplitude |S21| is lower than -50 dB in the corresponding frequency band. This shows that the cross-polarization transmitted wave has basically no influence on the unit performance. Similarly, by simulating the performance of the unit in the "π" state, it can be seen that the co-polarization transmission amplitude |S11| is greater than -2 dB in the same frequency band, and its cross-polarization amplitude |S21| is also lower than -50 dB. This shows that the on-off of the voltage-controlled diode will not affect the co-polarization transmission amplitude of the metasurface unit. Figure 2 (b) respectively gives the two transmission phase curves and the corresponding phase difference curve when the y-polarized wave incident along the +z-axis direction passes through the "0" unit and the "π" unit. It can be seen that the phase difference ΔΦ between the "0" unit and the "π" unit is exactly 180° in the frequency band of 9 - 10.5 GHz, indicating that the designed unit can achieve 1-bit phase quantization coding.

[0061] Figure 3 (a) and (b) respectively represent the coded phase distribution diagram of the designed +1-mode dual-beam OAM and the simulated three-dimensional radiation pattern. It can be seen that the +1-mode OAM realized by the 1-bit programmable metasurface system has good performance, and the deflection angle of the dual-beam is about 30°. Figure 3 (c) and (d) respectively represent the coded phase distribution diagram of the designed +2-mode dual-beam OAM and the simulated three-dimensional radiation pattern. It can be seen that the radiated dual-beam has the characteristics of a complete OAM beam, and the OAM mode is the +2 mode at the corresponding deflection angle. Figure 3 The shown simulation results verify the effectiveness of the programmable transmissive metasurface system in realizing multi-mode OAM.

[0062] Figure 4 (a), (b), and (c) are respectively the coded phase distribution diagrams of the designed +1-mode dual-beam OAM at the scanning angles of -10° / 10°, -30° / 30°, and -50° / 50°. Figure 4(d) is the two-dimensional pattern obtained from the simulation of the dual-beam OAM beam scanning function. From the two-dimensional pattern, it can be seen that the dual-beam OAM moves from θ = 10° to θ = 50° in sequence. For the dual-beam OAM with a scanning angle of -10° / 10°, the gain slightly decreases. At -30° / 30°, the beam radiation performance is good. At -50° / 50°, as the beam divergence angle increases, the gain of the beam slightly decreases. Overall, the dual-beam OAM has good gain during the complete scanning cycle. Figure 4 The shown simulation results indicate that the programmable transmissive metasurface system can achieve the function of simultaneous beam scanning for the +1 mode dual-beam OAM.

[0063] Figure 5 (a), (b), and (c) are respectively the coded phase distribution diagrams designed to generate the +1 mode dual-beam OAM at scanning angles of -10° / 30°, -30° / 30°, and -50° / 30°. Figure 5 (d) is the two-dimensional pattern obtained from the simulation of the asymmetric beam scanning function of the dual-beam OAM. From the two-dimensional pattern, it can be seen that the OAM beam of the +1 mode gradually deflects from -10° to -50°, and no obvious distortion occurs to the OAM beam. Figure 5 The shown simulation results indicate that the programmable transmissive metasurface system can achieve the function of independent beam scanning for the +1 mode dual-beam OAM.

[0064] Figure 6 (a) and (b) are respectively the coded phase distribution diagram and the simulated three-dimensional radiation pattern of the +1 mode dual-beam OAM with a beam divergence angle of 60° at a scanning angle of 20°. Figure 6 (c) and (d) are respectively the coded phase distribution diagram and the simulated three-dimensional radiation pattern of the +1 mode dual-beam OAM with a beam divergence angle of 60° at a scanning angle of -20°. From the radiation pattern, it can be seen that as the scanning angle changes, the gain of the dual-beam OAM slightly fluctuates, but the gain is basically greater than 14.5 dBi. Figure 6 The shown simulation results indicate that the programmable transmissive metasurface system can achieve the function of covering scanning for the +1 mode dual-beam OAM.

[0065] The programmable transmissive metasurface array sample of the multi-beam multi-mode OAM made in the present invention is 32×32. This sample consists of 1024 units in total. The test environment is an anechoic chamber (as Figure 7 shown), and the above sample is tested using a vector network analyzer, two pairs of linearly polarized horn antennas, and a far-field measurement method.

[0066] Figure 7 (a) shows the test environment diagram of the programmable metasurface system in the anechoic chamber. Figure 7(b) is the overall layout diagram of the programmable metasurface system array and the detailed schematic diagram of the feeder.

[0067] Figure 8 (a) shows the two-dimensional pattern of the +1 mode OAM far-field test results. Figure 8 (b) is the two-dimensional pattern of the +2 mode OAM far-field test results. It can be seen from the test pattern that the deflection angles of the two double-beams in different modes are about 30°, which is consistent with the preset deflection direction. Figure 8 (c) is the two-dimensional far-field pattern of the test results of the double-beam OAM simultaneous scanning function. It can be seen that two symmetric double-beam OAMs achieve continuous scanning function in space, and the maximum gain of the beam is 13.2 dBi. Figure 8 (d) is the two-dimensional far-field pattern of the test results of the double-beam OAM independent scanning function. It can be seen that the deflection angle of one of the double-beam OAM beams is fixed at 30°, and the other beam scans from -10° to -50° without obvious deformation of the beam. The maximum gain of the beam is 12.9 dBi. Figure 8 The shown test results are basically consistent with the simulation results, which proves that the proposed programmable transmissive metasurface system can achieve multi-modal multi-beam OAM and beam scanning functions.

Claims

1. The programmable transmissive metasurface unit of multi-beam multi-modal OAM, hereinafter simply referred to as "unit", includes four layers of metal patches, two layers of dielectric substrates and one layer of connection layer; when looking at the whole unit from top to bottom along the Z-axis direction, it is in turn: receiving layer, the first layer of dielectric substrate, bias layer, connection layer, metal ground plane, the second layer of dielectric substrate, radiation layer; Among them, the receiving layer, bias layer, metal ground plane and radiation layer are all metal layers; the two layers of dielectric substrates and the connection layer are all dielectric plates; and it is characterized in that the two layers of dielectric substrates and the connection layer are in the shape of a thin cuboid, with square upper and lower surfaces. The sizes of the two layers of dielectric substrates are exactly the same, and the projections of the two layers of dielectric substrates and the connection layer on the horizontal plane coincide; the side lengths of the two layers of dielectric substrates and the connection layer are all L, and L is the period length of the unit; The receiving layer metal patch is attached to the upper surface of the first layer of dielectric substrate and is composed of the connection of the first rectangular ring metal patch and 5 rectangular metal patches, and the first rectangular ring metal patch and 5 rectangular metal patches are integrally formed; the first rectangular ring metal patch is located at the approximate center position of the upper surface of the first layer of dielectric substrate, and the four sides of the outer ring and inner ring of the first rectangular ring metal patch are all parallel to the four sides of the dielectric substrate; the 5 rectangular metal patches include 4 small rectangular metal patches and 1 large rectangular metal patch. The 4 small rectangular metal patches have exactly the same size, and the four sides of the 5 rectangular metal patches are all parallel to the four sides of the dielectric substrate; the 1st and 2nd small rectangular metal patches extend from the left side of the inner ring to the right and are symmetric about the horizontal axis of symmetry of the receiving layer metal patch. There is a certain distance between the 1st and 2nd small rectangular metal patches and between them and the upper and lower sides of the inner ring; the 3rd and 4th small rectangular metal patches extend from the right side of the inner ring to the left and are symmetric with the 1st and 2nd small rectangular metal patches about the vertical axis of symmetry of the receiving layer metal patch respectively. The parameters of these 4 small rectangular metal patches are exactly the same; the large rectangular metal patch extends upward from the lower side of the inner ring and is symmetric about the vertical axis of symmetry of the receiving layer metal patch; In the first layer of dielectric substrate, three metallized vias with a radius of Ra are drilled respectively along the direction perpendicular to the upper and lower surfaces of the dielectric substrate. Among them, the first and second metallized vias are respectively located on the metal strips on the left and right sides of the rectangular ring metal patch of the receiving layer, and penetrate from the receiving layer metal patch to the bias layer metal patch from top to bottom to connect the two. The heights of the first and second metallized vias are Sh; the third metallized via is located at the center of the whole receiving layer metal patch and penetrates from the receiving layer metal patch to the radiation layer metal patch from top to bottom to connect the two; The three metallized vias in the second layer of dielectric substrate have the same parameters and corresponding positions as the metallized vias in the first layer of dielectric substrate; the ones corresponding to the positions of the first and second metallized vias are respectively named the fourth and fifth metallized vias. The fourth and fifth metallized vias penetrate from the metal ground plane to the radiation layer metal patch to connect the two. The metallized via in the middle position is the third metallized via; There is only one metallized via in the connection layer, which is located in the middle position and is the third metallized via; The bias layer metal patch is attached to the lower surface of the first dielectric substrate and is composed of two rectangular metal patches and a bias line. The four sides of the two rectangular metal patches are parallel to the four sides of the dielectric substrate, and the extending direction of the bias line is also parallel to the four sides of the dielectric substrate. The first rectangular metal patch is located in the left half of the lower surface of the first dielectric substrate. The four sides of the first rectangular metal patch maintain a certain distance from the four sides of the dielectric substrate. It is symmetric about the X-axis direction symmetry axis of the lower surface of the first dielectric substrate, and its length direction is parallel to the Y-axis. The second rectangular metal patch is located in the right half of the lower surface of the first dielectric substrate, is symmetric with the first rectangular metal patch about the Y-axis direction symmetry axis of the lower surface of the first dielectric substrate, and maintains a certain distance from the first rectangular metal patch. The parameters of the first and second rectangular metal patches are exactly the same, and the distance between them is I. The bias line is connected by seven rectangular metal wires. The first section extends leftward from the center of the left long side of the first rectangular metal patch for a certain length. Then it extends vertically downward for a certain length to form the second section. Subsequently, it extends rightward to form the third section. The fourth section extends rightward from the center of the right long side of the second rectangular metal patch for a certain length. Then it extends vertically downward for a certain length to form the fifth section. The lower end of the fifth section is connected to the rightmost end of the third section. It extends downward from the Y-axis direction symmetry axis on the third section on the lower surface of the first dielectric substrate for a certain length to form the sixth section. Subsequently, it extends leftward until it reaches the left edge of the lower surface of the first dielectric substrate to form the seventh section. The first, third, fourth, and seventh sections are all parallel to the X-axis, and the second, fifth, and sixth sections are all parallel to the Y-axis. The metal ground plane is a square thin layer with a side length of L, that is, the metal thin layer completely covers the lower surface of the connection layer. A circular hole is etched at the center of the metal ground plane. This circular hole needs to ensure that the third metallization via does not short-circuit with the metal ground plane. This circular hole is used for the metal via that passes through the connection receiving layer and the radiation layer. The radiation layer metal patch is attached to the lower surface of the second dielectric substrate and consists of a "return" shaped metal patch with protrusions and two PIN diodes; the "return" shaped metal patch includes a second rectangular ring metal patch and six rectangular metal patches; the second rectangular ring metal patch and the six rectangular metal patches are integrally formed; the second rectangular ring metal patch is located at approximately the center position of the lower surface of the second dielectric substrate, and the four sides of the outer ring and the inner ring of the second rectangular ring metal patch are parallel to the four sides of the dielectric substrate; the six rectangular metal patches include four large rectangular metal patches and two small rectangular metal patches, the four large rectangular metal patches are of the same size, and the four sides of the six rectangular metal patches are parallel to the four sides of the dielectric substrate; the 11th and 12th large rectangular metal patches extend from the left side of the inner ring to the right and are horizontally symmetric about the axis of symmetry of the radiation layer metal patch, and there is a certain distance between the 11th and 12th large rectangular metal patches and between them and the upper and lower sides of the inner ring; the 13th and 14th large rectangular metal patches extend from the right side of the inner ring to the left and are symmetric with the 11th and 12th large rectangular metal patches about the vertical axis of symmetry of the radiation layer metal patch respectively, and the parameters of these four large rectangular metal patches are exactly the same; the 15th small rectangular metal patch extends downward from the upper side of the inner ring and is vertically symmetric about the axis of symmetry of the radiation layer metal patch, and there is a certain distance between the 15th small rectangular metal patch and the left and right sides of the inner ring; the 16th small rectangular metal patch extends upward from the lower side of the inner ring and is symmetric with the 15th small rectangular metal patch about the horizontal axis of symmetry of the radiation layer metal patch, and the parameters of these two small rectangular metal patches are exactly the same; the positions of the four large rectangular metal patches in the radiation layer are approximately the same as those of the four small rectangular metal patches in the receiving layer, the distance between the 11th and 12th large rectangular metal patches is L3, the parameters of these four large rectangular metal patches are exactly the same, the length is L1, and the width is L2; the four sides of the inner ring and the outer ring of the second rectangular ring metal patch are parallel to the four sides of the dielectric substrate, and its center coincides with the center of the dielectric board; one independent "No. 1" battery-shaped metal patch is located at the center of the "return" shaped metal patch, and its four sides are parallel to the four sides of the dielectric substrate; the "No. 1" battery-shaped metal patch includes a square patch and two small rectangular patches; the square patch is exactly at the center of the "return" shaped metal patch, the 17th small rectangular patch extends upward from the upper side of the square patch and is vertically symmetric about the axis of symmetry of the radiation layer metal patch; the 18th small rectangular metal patch extends downward from the lower side of the square patch and is vertically symmetric about the axis of symmetry of the radiation layer metal patch; there is a certain distance between the 17th and 15th small rectangular metal patches and between the 18th and 16th small rectangular metal patches; its side length is Ts; the two loaded PIN diodes include an upper PIN diode I and a lower PIN diode II, both arranged in the direction of "positive pole on top, negative pole on bottom", the upper PIN diode I is connected between the 17th and 15th small rectangular metal patches, and the lower PIN diode II is connected between the 18th and 16th small rectangular metal patches.

2. The programmable transmissive metasurface unit of multi-beam multi-modal OAM as claimed in claim 1, characterized in that, the side length L of the two-layer dielectric substrate and the connecting layer ranges from 5 to 15 mm; the thickness Sh of the two-layer dielectric substrate ranges from 1 to 3 mm; the thickness Mh of the connecting layer ranges from 0.05 to 0.25 mm, and the dielectric constant ranges from 2.0 to 4.

4.

3. The programmable transmissive metasurface unit of multi-beam multi-modal OAM as claimed in claim 2, characterized in that, the side length L of the two-layer dielectric substrate and the connecting layer is 10 mm; the thickness Sh of the two-layer dielectric substrate is 1.52 mm; the thickness Mh of the connecting layer is 0.1 mm, the dielectric constant of the dielectric substrate is 3.55, and the dielectric constant of the connecting layer is 3.

3.

4. The programmable transmissive metasurface unit of multi-beam multi-modal OAM as claimed in claim 1, characterized in that, In the receiving layer metal patch, the outer ring length TL of the first rectangular ring metal patch is in the range of 5 - 8 mm, and the outer ring width T LW is in the range of 5 - 6 mm, and the annular width Tc is in the range of 0.5 - 1 mm; in the receiving layer metal patches, the length e1 of the 4 small rectangular metal patches along the X-axis ranges from 1 to 2 mm, and the width e2 along the Y-axis ranges from 0.5 to 1 mm; the distance e3 between the 1st and 2nd small rectangular metal patches along the Y-axis ranges from 1 to 2 mm; the length gl of the large rectangular metal patch along the Y-axis ranges from 2 to 4.5 mm, and the width gw along the X-axis ranges from 0.5 to 2 mm.

5. The programmable transmissive metasurface unit of multi-beam multi-modal OAM as claimed in claim 4, characterized in that, In the receiving layer metal patch, the outer ring length TL of the first rectangular ring metal patch is 6.4 mm, and the outer ring width T LW is 5.8 mm, and the annular width Tc is 0.8 mm; in the receiving layer metal patches, the length e1 of the 4 small rectangular metal patches along the X-axis is 1.6 mm, and the width e2 along the Y-axis is 0.6 mm; the distance e3 between the 1st and 2nd small rectangular metal patches along the Y-axis is 1.2 mm; the length gl of the large rectangular metal patch along the Y-axis is 3.1 mm, and the width gw along the X-axis is 0.9 mm.

6. The programmable transmissive metasurface unit of multi-beam multi-modal OAM as claimed in claim 1, characterized in that, in the bias layer metal patches, the length bl of the 1st and 2nd rectangular metal patches ranges from 3 to 6 mm, the width bw ranges from 1.3 to 2 mm, and the distance I between them ranges from 4 to 8 mm; the length w1 of the 1st and 4th rectangular metal wires ranges from 0.1 to 0.5 mm; the length w2 of the 2nd and 5th rectangular metal wires ranges from 2 to 5 mm; the length of the 3rd rectangular metal wire (I + 2*bw + 2*w1) ranges from 8 to 9 mm; the length w3 of the 6th rectangular metal wire ranges from 0.05 to 0.25 mm; the length of the 7th rectangular metal wire (L / 2 + 0.05 mm) ranges from 4.5 to 5.5 mm.

7. The programmable transmissive metasurface unit of multi-beam multi-modal OAM as claimed in claim 1, characterized in that, in the bias layer metal patches, the length bl of the 1st and 2nd rectangular metal patches is 5 mm, the width bw is 1.4 mm, and the distance I between them is 5 mm; The width of each rectangular metal wire is 0.1 mm. The lengths w1 of the 1st and 4th rectangular metal wires are 0.3 mm; the lengths w2 of the 2nd and 5th rectangular metal wires are 3 mm; the length (I + 2*bw + 2*w1) of the 3rd rectangular metal wire is 8.4 mm; the length w3 of the 6th rectangular metal wire is 0.1 mm; the length (L / 2 + 0.05 mm) of the 7th rectangular metal wire is 5.05 mm.

8. The programmable transmissive metasurface unit of multi-beam multi-modal OAM according to claim 1, characterized in that, in the radiation layer metal patch, the distance L3 between the 11th and 12th large rectangular metal patches is in the range of 1 - 2 mm, the lengths L1 of these 4 large rectangular metal patches are in the range of 0.5 - 2 mm, and the widths L2 are in the range of 0.25 - 0.8 mm; The outer ring side length TL of the second rectangular ring metal patch is in the range of 5 - 8 mm; the left and right side widths Tc of the second rectangular ring metal patch are in the range of 0.5 - 1 mm, and the upper and lower side widths Tb are in the range of 0.6 - 1.5 mm; In the "1" battery-type metal patch, the side length Ts of the square patch is in the range of 0.5 - 1.5 mm.

9. The programmable transmissive metasurface unit of multi-beam multi-modal OAM according to claim 1, characterized in that, in the radiation layer metal patch, the distance L3 between the 11th and 12th large rectangular metal patches is 1.6 mm, the lengths L1 of these 4 large rectangular metal patches are 1 mm, and the widths L2 are 0.6 mm; The outer ring side length TL of the second rectangular ring metal patch is 6.4 mm; the left and right side widths Tc of the second rectangular ring metal patch are 0.8 mm, and the upper and lower side widths Tb are 1.1 mm; The "1" battery-type metal patch includes one square patch and two small rectangular patches, which are integrally formed; among them, the side length Ts of the square patch is 1 mm; The PIN diode model is SMP1340-040LF.

10. The programmable transmissive metasurface array of multi-beam multi-modal OAM, characterized in that, it is formed by performing an m×n periodic array on the programmable transmissive metasurface unit of multi-beam multi-modal OAM according to any one of claims 1 to 9, where the ranges of m and n are 2 - 100.

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