Planar vortex orbital angular momentum antenna based on artificial surface plasmons

Abstract

The application discloses a planar vortex orbit angular momentum antenna based on artificial surface plasmons. The application comprises a resonant antenna and a feeding system; the resonant antenna comprises an artificial surface plasmon metal ring and a first dielectric plate; the feeding system comprises a second dielectric plate, an air dielectric layer, a metal ground, a third dielectric plate and a feeding network; two microstrip stubs are arranged on the third dielectric plate, and a small metal disc is arranged at the end of each microstrip stub; the microstrip stubs are connected with the feeding network through metal vias; the surface impedance of the slotted unit of each artificial surface plasmon unit in the artificial surface plasmon metal ring is the same or different. The application can emit a vortex wave beam carrying a precisely defined orbit angular momentum on a plane, and through synthesizing multiple wave beams at a fixed frequency, the multiple wave beams can be superimposed to form a new wave beam, so that the shape of the wave beam can be controlled. The wave beam scanning can be realized by adjusting the surface impedance distribution of each wave beam.

Description

Technical Field

[0001] This invention belongs to the field of artificial electromagnetic materials and relates to a planar vortex orbital angular momentum antenna based on artificial surface plasmons. Background Technology

[0002] In recent years, with the continuous development of wireless communication technology, while enjoying the convenience brought by high-speed communication, people have also put forward higher bandwidth and higher speed communication requirements. In today's rapidly developing wireless communication landscape, spectrum resources are extremely scarce. To alleviate this scarcity, new technologies are needed to improve this predicament, making multiplexing technology research a hot topic. With the continuous evolution of communication eras, current multiplexing technologies have incorporated dimensions such as frequency, time, code type, and space, namely Frequency Division Multiplexing (FDM), Time Division Multiplexing (TDM), Space Division Multiplexing (SDM), Orthogonal Frequency Division Multiplexing (OFDM), and the massive MIMO used in 5G. The emergence of these multiplexing methods has greatly alleviated the enormous pressure on modern communication capacity and speed. However, even so, these technologies still cannot meet the actual needs of the ever-increasing number of wireless terminals. Recently, vortex beams carrying orbital angular momentum (OAM) have attracted widespread attention. Orbital angular momentum, as a new physical degree of freedom for electromagnetic waves in addition to frequency, phase, amplitude, and polarization, greatly enhances the transmission channel of wireless communication systems through "state division multiplexing" based on this new dimension.

[0003] Orbital angular momentum (OAM), as a fundamental property of electromagnetic waves, has attracted widespread attention from scholars in recent years. Since electromagnetic waves carrying different orbital angular momentum are perfectly orthogonal, orbital angular momentum can serve as a new dimension for carrying information and has the potential to improve the capacity of communication systems. In the radio frequency field, vortex electromagnetic waves carrying orbital angular momentum inevitably exhibit beam divergence and a central phase singularity, posing significant challenges to their reception and demodulation in practical communication systems. When the antenna aperture at the receiving end is limited, the orthogonality between vortex electromagnetic waves of different states is disrupted, and the communication capacity cannot be improved. Summary of the Invention

[0004] The purpose of this invention is to effectively solve the problems of unavoidable beam divergence and central phase singularity of vortex electromagnetic waves carrying orbital angular momentum. This invention proposes a cylindrical resonant cavity antenna based on artificial surface plasmons to generate planar vortex orbital angular momentum.

[0005] The planar vortex orbital angular momentum antenna based on artificial surface plasmons has a cylindrical structure, which includes a resonant antenna and a feeding system from the outside to the inside.

[0006] The resonant antenna comprises, from the outside to the inside, the following:

[0007] Artificial surface plasmon metal ring (1) is formed by connecting several periodically arranged artificial surface plasmon units (11) end to end to form a ring structure;

[0008] The first dielectric plate (2) is located on the inner side of the artificial surface plasmon metal ring (1);

[0009] The power supply system, from the outside to the inside, includes:

[0010] The second dielectric plate (3) is located on the inner side of the first dielectric plate (2);

[0011] An air medium layer (4) is located on the inner side of the second medium plate (3);

[0012] Metal ground (5) is located on the inner side of the air medium layer (4);

[0013] The third dielectric plate (6) is located on the inner side of the metal ground (5);

[0014] The power supply network (7) is located on the inner side of the third dielectric plate (6);

[0015] in:

[0016] The upper surface of the third dielectric plate (6) is provided with two microstrip stubs (8), and each microstrip stub (8) is provided with a small metal disk (9) at its end; the microstrip stubs (8) are connected to the power supply network (7) through metal vias.

[0017] The artificial surface plasmon unit (11) is composed of two sets of axisymmetric slotted units (111) with periodically changing surface impedance. The surface impedance change period of the slotted units (111) of each artificial surface plasmon metal ring (1) is the same or different. The surface impedance change period of the slotted units (111) of each artificial surface plasmon unit (11) can be one of the function periods of sine, cosine, triangular wave, sawtooth wave, etc.

[0018] Preferably, the slotting direction of the slotting unit (111) is perpendicular to the circumference of the artificial surface plasmon metal ring (1).

[0019] Preferably, the surface impedance of the slotted unit (111) is achieved by adjusting parameters such as the slotting depth and slotting width of the slotted unit (111).

[0020] Preferably, the slotted unit (111) has a rectangular, V-shaped, trapezoidal or polygonal cross-sectional shape along its own axis.

[0021] Preferably, the modulation period of the single-cycle artificial surface plasmon unit (11) is determined by the number of modulation cycles.

[0022] Preferably, the small metal disk (9) has a radius of 0.5 mm and the microstrip stub (8) has a length of 1.6 mm, in order to improve radiation efficiency and reduce end reflection of the microstrip line.

[0023] Preferably, the power supply network (7) is implemented using a bridge, with the power supply port and output port of the bridge placed at symmetrical positions on the artificial surface plasmon metal ring (1).

[0024] Preferably, the first dielectric board (2), the second dielectric board (3), and the third dielectric board (6) are made of PCB board, silicon substrate, quartz substrate or polyimide substrate.

[0025] Preferably, the air medium layer (4) is made of foam board.

[0026] Preferably, the artificial surface plasmon metal ring (1) forms a resonant ring, and there is a phase difference required for orbital angular momentum between adjacent artificial surface plasmon units (11) on the resonant ring. The number of modes of orbital angular momentum is controlled by adjusting the number of cycles of the artificial surface plasmon units (11).

[0027] Working principle:

[0028] The circumference of the artificial surface plasmonic metal ring (1) is the modulation period. For a length n times its length, the resonance condition satisfies the following equation:

[0029] (1)

[0030] in Let be the number of resonant modes of the artificial surface plasmonic metal ring (1). Let be the radius of the artificial surface plasmonic metal ring (1). The effective refractive index of the plasmonic mode on the artificial surface. The wave number is in the azimuth direction. For the wavenumber in free space, The wavelength in free space;

[0031] Because of the radius of the annulus The slot width is much larger than that of the slotted unit (111), so the wave number of the first radiation harmonic emitted by the periodically modulated ring resonator (i.e., the artificial surface plasmon metal ring (1)) in the azimuth direction satisfies the following formula:

[0032] (2)

[0033] in Azimuth direction Wave number of the second fastest wave;

[0034] From formulas (1) and (2), the azimuth propagation constant of the radiated beam at the resonant point is obtained. ,in It is the number of resonant modes of the artificial surface plasmonic metal ring (1). The modulation period number is contained in the artificial surface plasmon metal ring (1); at this time, the beam radiated by the artificial surface plasmon metal ring (1) is a planar vector vortex beam, which carries... Phase characteristics, The topological charge number, The azimuth angle is given; the beam radiated by the artificial surface plasmon metal ring (1) is a planar vector vortex beam with a helical wavefront and carries and One-to-one correspondence of orbital angular momentum modes, the correspondence being at a fixed resonance point Therefore, by adjusting the modulation period of the resonant ring... This allows for the flexible acquisition of orbital angular momentum mode numbers.

[0035] ① When the surface impedance change period of the slotted unit (111) of each artificial surface plasmon metal ring (1) is the same, that is, the artificial surface plasmon unit (11) is of one form; the modulation formula of the surface impedance is as follows:

[0036] (3)

[0037] in, Let be the average surface impedance of the artificial surface plasmon unit structure A. The modulation depth has a value ranging from 0 to 1. For the modulation period, The direction is the direction in which the electromagnetic wave propagates along the impedance surface. It is the imaginary unit.

[0038] ② When the surface impedance change period of the slotted unit (111) of each artificial surface plasmon metal ring (1) is different, and there are two types of surface impedance change periods, that is, the artificial surface plasmon unit (11) has two forms; the modulation formula of surface impedance is as follows:

[0039] By adjusting the impedance modulation function and merging the two modulation periods, the modulation formula for the surface impedance is as follows:

[0040] (4)

[0041] in and Corresponding to different orbital angular momentum modes and The modulation period length, and These are the modulation factors for two periods. To maintain consistent radiated energy of the beams in the two orbital angular momentum modes, the two modulation factors are kept consistent. Based on the modulation function described above, the artificial surface plasmon resonance structure with periodic arrangement enables the antenna to radiate two beams at different angles. Furthermore, the radiation angle of the beams can be controlled by adjusting the period length p; the two beams are independently controlled.

[0042] To generate a rotating mode, two necessary conditions are required: first, two orthogonal modes must be excited at the same frequency; second, there must be a phase difference of ±90° between the two orthogonal modes. To meet these conditions, a bridge feed is used, and the angle between the two feed positions... Determined by the following formula:

[0043] (5)

[0044] in The number of resonant modes. Since the number of each orbital angular momentum mode is orthogonal to each other, and the bridge feed ensures that the two feed positions satisfy a phase difference of ±90°.

[0045] A beam obtained by superimposing the orbital angular momentum modes of N planar vortices on a two-dimensional plane is called a structure electromagnetic wave, and its beam satisfies the formula:

[0046] (6)

[0047] Where A represents the amplitude. Indicates azimuth. This represents the initial phase carried by the planar vortex orbit angular momentum beam for each mode number. The superposition of multiple planar vortex orbit angular momentum modes can generate a highly directional beam. As the number of modes N increases, the main lobe of the generated beam becomes narrower, and the beam's directivity increases. Based on beamforming, beam scanning can be achieved using structured electromagnetic waves composed of planar vortex orbit angular momentum. Given a fixed number of planar vortex orbit angular momentum modes required for beam synthesis, the main lobe direction is determined by the initial phase of different mode numbers. Decide.

[0048] This antenna can transmit vortex beams carrying precisely defined orbital angular momentum in a plane, and at a fixed frequency, it can synthesize multiple beams and superimpose them to form a new beam, thereby controlling the shape of the beam. By adjusting the initial phase of each beam, beam scanning can be easily achieved.

[0049] The beneficial effects of this invention are as follows:

[0050] (1) Compared with the prior art, the planar vortex beam transmitter of the present invention combines the impedance surface modulation leaky antenna theory and the artificial surface plasmon theory. It achieves the modulation of the surface impedance by adjusting the slot depth of the surface plasmon unit structure, and then realizes electromagnetic wave radiation by periodically arranging the surface plasmon unit structure.

[0051] (2) Several surface plasmon structures are arranged in a circular periodic pattern to form a resonant ring, which improves radiation efficiency. At the same time, there is a phase difference between adjacent units on the resonant ring that is required for orbital angular momentum. The number of modes of orbital angular momentum can be flexibly controlled by adjusting the number of unit periods.

[0052] (3) The present invention can generate two or more different beams by modulation period without changing the structural size, and superimpose multiple beams to form a new beam, thereby controlling the shape of the new beam.

[0053] (4) The present invention can achieve beam scanning in a 360° range by modulating the initial phase.

[0054] (5) The present invention uses a simple feeding network. Different port feeding will generate vortex beams with different orbital angular momentum mode numbers, thus realizing antenna reuse.

[0055] (6) The vortex beam generated by the present invention can radiate in a plane, which solves the problem of unavoidable beam divergence and central phase singularity of vortex electromagnetic waves carrying orbital angular momentum.

[0056] (7) The present invention can change the direction of beam radiation by adjusting the initial phase of the radiation beam, thereby achieving beam scanning in a 360° range.

[0057] (8) The present invention is simple to manufacture, easy to operate, and easy to integrate into the system, saving costs. Attached Figure Description

[0058] Figure 1 This is a schematic diagram of a planar vortex orbital angular momentum antenna based on artificial surface plasmons, and a magnified view of its part;

[0059] Figure 2 is a schematic diagram of the unfolded planar vortex orbital angular momentum antenna based on artificial surface plasmons.

[0060] Figure 3 This is a schematic diagram of the cross-sectional structure of a planar vortex orbital angular momentum antenna based on artificial surface plasmons after partial unfolding.

[0061] Figure 4 (a)-(d) are schematic diagrams of the microstrip stub, feed network, multiple artificial surface plasmon elements with two modulation periods, and multiple artificial surface plasmon elements with one modulation period, respectively, of a planar vortex orbital angular momentum antenna based on artificial surface plasmons.

[0062] Figure 5 (a) and (b) are schematic diagrams of one artificial surface plasmon element and one slotted element of a planar vortex orbital angular momentum antenna based on artificial surface plasmons, respectively.

[0063] Figure 6 These are dispersion curves for slotted units with different slot depths and curves showing the relationship between slot depth and impedance surface.

[0064] Figure 7 These are curves of the S-parameters of 6- and 7-cycle and dual-cycle combined loop resonant antennas.

[0065] Figure 8 It shows the azimuth radiation beam phase distribution diagram and far-field three-dimensional radiation pattern of different ports in a single cycle at the resonant frequency.

[0066] Figure 9 It is the far-field three-dimensional radiation pattern of the azimuth-polarized radiation beams of single-cycle and double-cycle beams at different ports under the resonant frequency.

[0067] Figure 10 It is a beam scan diagram synthesized by two periods at the resonant frequency.

[0068] The diagram is labeled as follows: 1. Artificial surface plasmon metal ring, 11. Artificial surface plasmon unit, 111 slotted unit, 2. First dielectric substrate, 3. Second dielectric substrate, 4. Air dielectric layer, 5. Metal ground, 6. Third dielectric substrate, 7. Feed network, 8. Microstrip stub, 9. Small metal disk. Detailed Implementation

[0069] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings.

[0070] like Figure 1-4As shown, the planar vortex orbital angular momentum antenna based on artificial surface plasmon resonance (ASPR) of this invention has a cylindrical structure, which includes, from the outside to the inside, a periodically modulated linear leaky wave antenna and a feeding system. The periodically modulated linear leaky wave antenna (i.e., resonant antenna) includes, from the outside to the inside, an ASPR metal ring 1 and a first dielectric substrate 2. The ASPR metal ring 1 is formed by periodically arranged ASPR units 11 connected end to end to form a ring structure. The feeding system includes, from the outside to the inside, a second dielectric substrate 3, an air dielectric layer 4, a metal ground 5, a third dielectric substrate 6, and a feeding network 7. The upper surface of the second dielectric substrate 3 is provided with two microstrip stubs 8, and each microstrip stub 8 has a small metal disk 9 at its end. The microstrip stubs 8 are connected to the feeding network 7 through metal vias.

[0071] like Figure 5 As shown in (a), the artificial surface plasmon element 11 in the linear leaky wave antenna with 7 periods is composed of two sets of axisymmetric slotted elements 111 with periodically varying surface impedance. The slot depth of the slotted element 111 is exponentially related to the imaginary part of the surface impedance. One modulation period includes 12 slotted elements, with corresponding slot depths g1, g2, g3, g4, g5, g6, and g7, and corresponding values ​​of 4.28 mm, 4.21 mm, 3.92 mm, 3.23 mm, 2.05 mm, 0.81 mm, and 0.25 mm, respectively. Where p = 12 * d = 20.4 mm.

[0072] like Figure 5 As shown in (b), the slot depth of one modulation unit structure in the artificial surface plasmon resonance unit structure is h, and the slot width is a. The slot depth h is determined based on the required surface impedance of the triangular wave, and the values, grouped into sets of six, are 0.6 mm, 1.2 mm, 1.8 mm, 2.4 mm, 3 mm, and 3.6 mm, respectively, from smallest to largest.

[0073] In this embodiment, the surface impedance of the artificial surface plasmon unit 11 can be obtained by the following formula:

[0074] (7)

[0075] in, The average surface impedance of the artificial surface plasmon unit 11 is given by [the relevant parameter]. The modulation depth has a value ranging from 0 to 1. For the modulation period, The direction is the direction in which the electromagnetic wave propagates along the impedance surface. It is the imaginary unit.

[0076] Typically excited by impedance surfaces The second fastest wave is always radiated first, therefore the phase constant of the first radiation harmonic mode is... It can be derived from the following formula:

[0077] (8)

[0078] in, The wave number of the -1 fast wave, Let be the wavenumber of the surface plasmon wave along the propagation direction on the waveguide, and be the radiation angle of the radiating beam. It can be given by the following formula:

[0079] (9)

[0080] in Let be the wave number of the vacuum. The phase characteristic of the vector vortex is: Where l is the topological charge. For each revolution along the azimuth direction, the phase changes to −2π, 0, 2π, corresponding to l = -1, 0, 1. This means that the phase of our designed radiating vortex wave should satisfy the following equation:

[0081] (10)

[0082] Where C is the perimeter of the resonant antenna, so according to the formula above, we can obtain... Thus, one can also obtain Therefore, we can calculate the average surface impedance corresponding to the artificial surface plasmon unit 11 according to the following formula. :

[0083] (11)

[0084] in Let M be the free-space wave impedance. Choosing a modulation depth M = 0.7, we can obtain the following from formulas (8)-(11): Figure 6 The relationship between impedance and slot depth was calculated from the dispersion curves of elements with different slot depths.

[0085] like Figure 6 The unit dispersion curves for different groove depths shown demonstrate that different groove depths correspond to different dispersion cutoff frequencies, with larger groove depths resulting in lower cutoff frequencies. The groove depth h and surface impedance are also relevant. The relationship curve, with the ordinate representing surface impedance, in units of... , The x-axis represents ohms. The x-axis represents the groove depth h, in mm.

[0086] We bend the above n (n=7) periodically arranged artificial surface plasmon units 11 with surface impedance modulation end to end into a ring, the circumference of which is the modulation period. The length is n times the length. The condition for circular ring resonance satisfies the following equation:

[0087] (12)

[0088] in Let be the mode number of the resonant ring. Where is the radius of the annulus. The effective refractive index of the plasmonic mode on the artificial surface. The wave number is in the azimuth direction. For the wavenumber in free space, The wavelength is in free space. Because the radius of the annulus... Since the grooves on the ring are much deeper than those on a circular ring, the wavenumber of the first radiated harmonic emitted by the periodically modulated ring resonator in the azimuth direction satisfies the following formula:

[0089] (13)

[0090] in Azimuth direction The wave number of the second fastest wave.

[0091] From equations (12) and (13), the azimuth propagation constant of the radiated beam at the resonant point can be obtained. ,in It is the number of optical cycles contained in the resonant ring. This represents the number of modulation periods contained in the resonant ring. At this point, the beam radiated by the resonant ring is a planar vector vortex beam, carrying... Phase characteristics, The topological charge number, The azimuth angle is given. Furthermore, this vector vortex possesses a helical wavefront and carries [variables / significance]. One-to-one correspondence of orbital angular momentum modes, the correspondence being at a fixed resonance point More importantly, compared to other structures, this device allows for adjustment of the modulation cycle number of the resonant ring. This allows us to obtain different orbital angular momentum modes at a fixed frequency.

[0092] like Figure 4 As shown, in order to be able to convert two different orbital angular momentum modes... and By combining them into a single antenna structure, we adjust the impedance modulation function and merge the two modulation periods, which, according to formula (7), becomes the following formula:

[0093] (14)

[0094] in and Number of corresponding orbital angular momentum modes and The modulation period length, and These are the modulation factors for the two periods. To ensure consistent radiated energy of the beams in the two orbital angular momentum modes, we set both modulation factors to 0.35. Based on the modulation function described above, the artificial surface plasmonic unit structure with periodic arrangement enables the antenna to radiate two beams at different angles. Furthermore, the radiation angle of the beams can be controlled by adjusting the period length p; the two beams are independently controlled.

[0095] like Figure 1 As shown in feed network 7, two necessary conditions are required to generate the rotating mode: one is that the two orthogonal modes are excited at the same frequency, and the other is that there is a phase difference of ±90° between the two orthogonal modes. To meet these conditions, we use bridge feeding, and the angle between the two feeding positions... Determined by the following formula:

[0096] (15)

[0097] in This represents the number of resonant modes. Since each orbital angular momentum mode is orthogonal to the others, and the bridge feeding ensures a ±90° phase difference between the two feeding positions, the designed antenna satisfies the requirement for generating rotational modes. When we feed one of the ports, we can obtain the orbital angular momentum. or If we simultaneously power both ports, we can obtain the orbital angular momentum ± The synthesis of.

[0098] Figure 7 The S-parameter curves for single-cycle and dual-cycle synthesis are presented. It can be seen that, regardless of whether it is single-cycle or dual-cycle synthesis, the resonant frequency when the number of resonant modes m is 8 is around 9.8 GHz, which is consistent with our expected calculations.

[0099] like Figure 8 The diagram shows the electric field and phase distribution of a single-cycle azimuth-polarized radiation beam at the resonant frequency, as well as the far-field three-dimensional radiation pattern. When the number of cycles is 6 or 7, the optical cycle number corresponding to a fixed frequency of 9.8 GHz can be achieved. =8. The corresponding orbital angular momentum mode numbers are 2 and 1, respectively. It appears at the resonant frequency. The phase gradient changes are integer multiples, thus allowing the observation of different orbital angular momentum modes at the resonant frequency, indicating that the radiated beam carries multiple precisely defined orbital angular momentum. Furthermore, its far-field radiation pattern is omnidirectional.

[0100] A beam obtained by superimposing the orbital angular momentum modes of two planar vortexes in a two-dimensional plane is called a structure electromagnetic wave, and its beam satisfies the following formula:

[0101] (16)

[0102] Where A represents the amplitude. Indicates azimuth. This represents the initial phase carried by the planar vortex orbit angular momentum beam for each mode number. The superposition of two planar vortex orbit angular momentum modes can produce a highly directional beam. As the number of modes increases, the main lobe of the generated beam becomes narrower, and the beam's directivity increases. For example... Figure 9 The electric field and far-field three-dimensional radiation patterns of azimuth-polarized radiation beams simultaneously fed by single-cycle and dual-cycle dual-port systems at the shown resonant frequency. When dual-port fed, the number and shape of the main lobes of the far-field radiation pattern are determined by the mode number interval. Decision. When the orbital angular momentum mode number is 2, its The number is 4, and the number of main lobes in its far-field radiation pattern is also 4. The same applies to the orbital angular momentum mode number, which is 1. If it is a two-period... and In the case of synthesis, the number of main lobes is 3. The directivity of the beam synthesized by dual-period synthesis changes from omnidirectional in single-period synthesis to a beam pointing at a certain angle, thus confirming the theory of improved beam directivity.

[0103] Based on beamforming, beam scanning can be achieved using structured electromagnetic waves formed by the angular momentum of planar vortex orbits. Given a fixed number of planar vortex orbit angular momentum modes required for beam synthesis, the main lobe direction is determined by the initial phase of different mode numbers. The initial phase of the antenna is determined during trigonometric function modulation. Therefore, in the dual-cycle modulation function, the initial phase difference between the two cosine functions needs to be precisely set to the desired initial phase value. This alters the surface impedance distribution of the resonant antenna, allowing the main lobe to scan within a 360° range. Figure 10 The figure shows the three-dimensional radiation pattern of the far field under the condition that each initial phase is 60° out of phase.

[0104] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details of the above-described embodiments. Within the scope of the technical concept of the present invention, various equivalent transformations can be made to the technical solutions of the invention, and all such equivalent transformations fall within the protection scope of the present invention.

Claims

1. A planar vortex orbital angular momentum antenna based on artificial surface plasmon resonances, having a cylindrical structure, characterized in that... From the outside in, it includes a resonant antenna and a feeding system; The resonant antenna comprises, from the outside to the inside, the following: Artificial surface plasmon metal ring (1) is formed by connecting several periodically arranged artificial surface plasmon units (11) end to end to form a ring structure; The first dielectric plate (2) is located on the inner side of the artificial surface plasmon metal ring (1); The power supply system, from the outside to the inside, includes: The second dielectric plate (3) is located on the inner side of the first dielectric plate (2); An air medium layer (4) is located on the inner side of the second medium plate (3); Metal ground (5) is located on the inner side of the air medium layer (4); The third dielectric plate (6) is located on the inner side of the metal ground (5); The power supply network (7) is located on the inner side of the third dielectric plate (6); the power supply network (7) is implemented using a bridge circuit, and the power supply port and output port of the bridge circuit are respectively placed at symmetrical positions on the artificial surface plasmon metal ring (1); the angles of the two power supply positions are determined according to the following formula: （5） Among them The number of resonant modes; since the number of each orbital angular momentum mode is orthogonal to each other, and the bridge feed ensures that the two feed positions satisfy a phase difference of ±90°; in: The upper surface of the third dielectric plate (6) is provided with two microstrip stubs (8), and each microstrip stub (8) is provided with a small metal disk (9) at its end; the microstrip stubs (8) are connected to the power supply network (7) through metal vias. The artificial surface plasmon unit (11) is composed of two sets of slotted units (111) with periodic changes in surface impedance that are symmetrical about the central transverse axis of the artificial surface plasmon unit (11). The surface impedance change period of the slotted units (111) of each artificial surface plasmon unit (11) in the artificial surface plasmon metal ring (1) is the same or different.

2. The planar vortex orbital angular momentum antenna based on artificial surface plasmons according to claim 1, characterized in that... The surface impedance change period of the slotted unit (111) of each artificial surface plasmon unit (11) adopts one of the following: sine, cosine, triangular wave, or sawtooth wave function period.

3. The planar vortex orbital angular momentum antenna based on artificial surface plasmons according to claim 1, characterized in that... The slotting direction of the slotting unit (111) is perpendicular to the circumference of the artificial surface plasmon metal ring (1).

4. The planar vortex orbital angular momentum antenna based on artificial surface plasmons according to claim 1, characterized in that... The slotted unit (111) has a rectangular, V-shaped, trapezoidal or polygonal cross-sectional shape along its own axis.

5. The planar vortex orbital angular momentum antenna based on artificial surface plasmons according to claim 1, characterized in that... The first dielectric board (2), the second dielectric board (3), and the third dielectric board (6) are made of PCB board, silicon substrate, quartz substrate or polyimide substrate.

6. The planar vortex orbital angular momentum antenna based on artificial surface plasmons according to claim 1, characterized in that... The artificial surface plasmon metal ring (1) forms a resonant ring. There is a phase difference required for orbital angular momentum between adjacent artificial surface plasmon units (11) on the resonant ring. The number of modes of orbital angular momentum is controlled by adjusting the number of cycles of the artificial surface plasmon units (11).

7. The planar vortex orbital angular momentum antenna based on artificial surface plasmons according to any one of claims 1-6, characterized in that... The circumference of the artificial surface plasmonic metal ring (1) is the modulation period. For a length n times its length, the resonance condition satisfies the following equation: （1） in Let be the number of resonant modes of the artificial surface plasmonic metal ring (1). Let be the radius of the artificial surface plasmonic metal ring (1). The effective refractive index of the plasmonic mode on the artificial surface. The wave number is in the azimuth direction. For the wavenumber in free space, The wavelength in free space; Because of the radius of the annulus The groove width is larger than that of the slotted unit (111), therefore the wavenumber of the first radiation harmonic emitted by the artificial surface plasmon metal ring (1) in the azimuth direction satisfies the following formula: （2） in Azimuth direction Wave number of the second fastest wave; From formulas (1) and (2), the azimuth propagation constant of the radiated beam at the resonant point is obtained. ,in It is the number of resonant modes of the artificial surface plasmonic metal ring (1). The modulation period number is contained in the artificial surface plasmon metal ring (1); at this time, the beam radiated by the artificial surface plasmon metal ring (1) is a planar vector vortex beam, which carries... Phase characteristics, The topological charge number, It is the azimuth angle; The beam radiated by the artificial surface plasmon metal ring (1) is a planar vector vortex beam with a helical wavefront and carries and One-to-one correspondence of orbital angular momentum modes, the correspondence being at a fixed resonance point ; Therefore, by adjusting the modulation period of the resonant ring... This allows for the flexible acquisition of orbital angular momentum mode numbers.

8. The planar vortex orbital angular momentum antenna based on artificial surface plasmons according to any one of claims 1-6, characterized in that... When the surface impedance change period of the slotted unit (111) of each artificial surface plasmon metal ring (1) is the same, the modulation formula of the surface impedance is as follows: (3) in, Let be the average surface impedance of the artificial surface plasmon unit structure A. The modulation depth has a value ranging from 0 to 1. For the modulation period, The direction is the direction in which the electromagnetic wave propagates along the impedance surface. The imaginary unit; When there are two different periods of surface impedance change in the slotted unit (111) of each artificial surface plasmon metal ring (1), the modulation formula of the surface impedance is as follows: (4) in and Corresponding to different orbital angular momentum modes and The modulation period length, and These are the modulation factors for two periods. In order to keep the radiated energy of the beams in the two orbital angular momentum modes consistent, the two modulation factors are kept consistent. According to the above modulation formula, the artificial surface plasmon unit structure with the modulation period arrangement can enable the antenna to radiate two beams at different angles. The radiation angle of the beams can also be controlled by adjusting the period length p. The two beams are independently controlled.

9. The planar vortex orbital angular momentum antenna based on artificial surface plasmons according to any one of claims 1-6, characterized in that... A beam obtained by superimposing the orbital angular momentum modes of N planar vortices on a two-dimensional plane is called a structure electromagnetic wave, and its beam satisfies the following formula: (6) Where A represents the amplitude. Indicates azimuth. This represents the initial phase carried by the plane vortex orbital angular momentum beam for each mode number. The interval is the number of patterns.

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