Total-space circularly-polarized metasurface with same modulation amplitude

Abstract

The invention provides a full-space circularly polarized metasurface with identical amplitude modulation, and relates to the technical field of electromagnetic regulation and control of novel artificial electromagnetic materials. The metasurface comprises M * M metasurface units which are arranged in an array, wherein M is equal to 2, 3, 4,...; in the metasurface unit, a first metal layer comprises a first substructure and a second substructure; the first substructure is a gear and comprises four equidistantly distributed tooth roots, a pair of transverse tooth roots are equal in length, and a pair of longitudinal tooth roots are equal in length; a concentric ring is arranged in the gear ring of the first substructure; the second substructure is arranged in the concentric circular ring and comprises a double-E structure and a cross structure; openings of the double-E structure are opposite, the double-E structure is provided with two symmetry axes passing through the circle center of the gear ring, and the cross-shaped structure coincides with the two symmetry axes. The second metal layer is a metal plate etched with an annular metal groove; the first and third metal layers have the same structure. In the metasurface, a plurality of metasurface units with different polarization structures are designed, three independent functions can be realized, and the metasurface is rich in function, small in size, high in efficiency and high in integration degree.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic control of novel artificial electromagnetic materials, and in particular to a metasurface with the same amplitude modulation of circular polarization in the entire space. Background Art

[0002] A metasurface is a two-dimensional planar structure constructed by subwavelength-sized unit structures according to a certain arrangement rule. By adjusting the unit's own structure and arrangement, electromagnetic waves can be flexibly controlled. Compared with traditional three-dimensional metamaterials, metasurfaces have the advantages of low profile, low loss, easy processing and integration, so they have shown important applications in devices such as beam splitters, superlenses, vortex beam generators and polarization converters. However, the above-mentioned metasurface devices only control the phase of electromagnetic waves. If more complex and novel electromagnetic functions are to be realized, it is necessary to jointly modulate the phase and amplitude of electromagnetic waves at the same time, such as low sidelobe lens antennas, multi-beam generators with arbitrary energy distribution, high-quality holographic imaging and multi-focal lenses with arbitrary energy distribution.

[0003] Early research on the independent control of electromagnetic wave amplitude and phase using metasurfaces was mainly focused on the field of linear polarization, while there was little research on the amplitude phase modulation of circularly polarized waves. Although dual geometric phase, hybrid phase and loaded resistor elements can achieve amplitude phase modulation of circularly polarized waves, most of them are in reflection or transmission models, lacking a full-space mode of reflection and transmission, and have technical problems such as large size, single function and limited efficiency. Summary of the invention

[0004] In order to solve the above technical problems existing in the prior art, the present invention provides a metasurface with the same amplitude modulation of circular polarization in the entire space.

[0005] In the first aspect, the present invention provides a metasurface with full-space circular polarization amplitude co-tuning, and the specific technical solution is as follows:

[0006] It includes M×M metasurface units arranged in an array, where M=2, 3, 4, ...;

[0007] The metasurface unit includes a first metal layer, a first dielectric layer, a second metal layer, a second dielectric layer and a third metal layer arranged in sequence from top to bottom;

[0008] The first metal layer includes a first substructure and a second substructure each consisting of a metal strip;

[0009] The first substructure is a gear, comprising a gear ring and four tooth roots equidistantly distributed along the gear ring; wherein two transverse tooth roots are of equal length and two longitudinal tooth roots are of equal length;

[0010] Concentric rings are provided inside the gear ring of the first substructure;

[0011] The second substructure is arranged in the concentric rings, and includes a double E structure and a cross structure; the double E structure has opposite openings and two symmetry axes passing through the center of the toothed ring; the cross structure coincides with the two symmetry axes;

[0012] The second metal layer is a metal plate with a circular metal groove etched therein, wherein the radius of the circular metal groove is smaller than the inner radius of the gear ring;

[0013] The third metal layer has the same structure as the first metal layer.

[0014] Preferably,

[0015]

[0016] l x1,i ≠l x1,j ;

[0017] Where i and j are the serial numbers of the metasurface units, i = 1, 2, ..., N, j = 1, 2, ..., N, i ≠ j, N = M × M; l x1,i , l x1,j are the lengths of the transverse tooth roots of the first metal layer in the i-th and j-th metasurface units, respectively; l x,min , l x,max are respectively the minimum and maximum lengths of the transverse tooth roots of all the first metal layers in the super surface.

[0018] Preferably,

[0019]

[0020] α 1,i ≠α 1,j ;

[0021] In the formula, α 1,i , α 1,j are respectively the rotation angles of the first substructure of the first metal layer in the ith and jth metasurface units relative to the lateral direction of the array.

[0022] Preferably,

[0023]

[0024] l x2,i ≠l x2,j ;

[0025] In the formula, l x2,i , l x2,j are the lengths of the lateral tooth roots of the third metal layer in the i-th and j-th supersurface units, respectively.

[0026] Preferably,

[0027]

[0028] α 2,i ≠α 2,j ;

[0029] In the formula, α 2,i , α 2,j are respectively the rotation angles of the first substructure of the third metal layer in the ith and jth metasurface units relative to the lateral direction of the array.

[0030] Preferably,

[0031]

[0032] Δθ i ≠Δθ j ;

[0033] In the formula, Δθ i , Δθ j are the rotation angle differences between the two second substructures of the first metal layer and the third metal layer in the i-th and j-th metasurface units respectively.

[0034]

[0035] Δθ i ≠Δθ j ;

[0036] In the formula, Δθ i , Δθ j are the rotation angle differences between the two second substructures of the first metal layer and the third metal layer in the i-th and j-th metasurface units respectively.

[0037] Preferably,

[0038]

[0039] θ 1,i ≠θ 1,j ; Δθ i ∈[0°, 360°);

[0040] In the formula, θ 1,i ,θ 1,j are the rotation angles of the second substructure of the first metal layer in the i-th and j-th metasurface units relative to the lateral direction of the array, θ 2,i ,θ 2,j are respectively the rotation angles of the second substructure of the third metal layer in the i-th and j-th metasurface units relative to the lateral direction of the array.

[0041] Preferably,

[0042] The period of the metasurface unit is 10 mm;

[0043] In each metasurface unit,

[0044] The first metal layer, the second metal layer and the third metal layer are all made of copper, and the thickness is 0.018mm;

[0045] The first dielectric layer and the second dielectric layer are both made of F4B material with a dielectric constant of 2.65 and a loss tangent of 0.001, and the thickness is 1mm;

[0046] The length of the longitudinal tooth root is 1.1 mm, and the length of the transverse tooth root is between 0.15 mm and 1.1 mm;

[0047] The inner radius of the toothed ring is 3.5mm and the width is 0.2mm; the inner radius of the concentric ring is 3.1mm and the width is 0.2mm;

[0048] In the second substructure, the width of the metal strips is 0.4 mm;

[0049] In the cross structure, the length of the metal strip connecting the double E structure is 5.5 mm, and the length of the other metal strip is 4.6 mm;

[0050] In the double-E structure, the height of the letter E is 3.8 mm and the width is 1.88 mm;

[0051] In the second metal layer, the circular ring metal groove has a width of 0.4 mm and an inner radius of 2.1 mm.

[0052] The super surface in the technical solution provided by the present invention has the beneficial effects of small size and low profile.

[0053] Furthermore, each preferred scheme can independently and freely modulate the amplitude and phase of the circularly polarized wave in the reflection channel of the low-frequency band and the transmission channel of the high-frequency band of forward / reverse incidence, and can realize the flexible regulation of the circularly polarized electromagnetic wave by three channels in the whole space, with a high degree of integration; it can independently realize the three functions of energy-adjustable lateral dual focusing points, energy-adjustable longitudinal dual focusing points and multi-beam with adjustable beam direction and energy, with rich functions and high working efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 Schematic diagram of the function of the metasurface with the same amplitude modulation of circular polarization in the entire space in the present invention.

[0055] Figure 2 In the figure, (a) is a schematic diagram of the layered structure of the super surface unit in the present invention; (b) is a schematic diagram of the structure of the first metal layer of the super surface unit in the present invention; (c) is a schematic diagram of the structure of the third metal layer of the super surface unit in the present invention.

[0056] Figure 3In the figure, (a) is the current distribution diagram of the three metal layers on the surface of the metasurface under the vertical incidence of 9 GHz RCP (Right-handed Circular Polarization) wave; (b) is the current distribution diagram of the three metal layers on the surface of the metasurface under the vertical incidence of 13 GHz RCP wave.

[0057] Figure 4 In the figure, (a) is a unit simulation scattering parameter diagram of the first substructure in the present invention; (b) is a unit simulation scattering parameter diagram of the second substructure in the present invention; (c) is a unit simulation scattering parameter diagram of the overall unit merged inside and outside in the present invention.

[0058] Figure 5 In (a), when a 9 GHz linearly polarized plane wave is incident vertically on the metasurface unit of the present invention, the reflection coefficients of the incident waves polarized in the x and y directions vary with the transverse tooth root length l. x The simulation results of the changes are shown in Figure 2; (b) is a schematic diagram of the reflection amplitude and phase changes under different Δφ when the RCP plane wave with a frequency of 9 GHz is vertically incident on the metasurface unit of the present invention; (c) is a schematic diagram of the reflection amplitude and phase changes under different α1 when the RCP plane wave with a frequency of 9 GHz is vertically incident on the metasurface unit of the present invention; (d) is a schematic diagram of the transmission amplitude and phase changes with Δθ when the RCP plane wave with a frequency of 13 GHz is vertically incident on the metasurface unit of the present invention; (e) is a schematic diagram of the transmission amplitude changes with θ1 under different Δθ; (f) is a schematic diagram of the phase changes with θ1 under different Δθ.

[0059] Figure 6 In the figure, (a) is a simulation structural model diagram of the first metal layer of the metasurface with the same amplitude of circular polarization in the whole space; (b) is a simulation structural model diagram of the second metal layer of the metasurface with the same amplitude of circular polarization in the whole space; (c) is a simulation structural model diagram of the third metal layer of the metasurface with the same amplitude of circular polarization in the whole space; (d) is a processed sample of the metasurface with the same amplitude of circular polarization in the whole space.

[0060] Figure 7 Schematic diagram of the principle of generating a lateral double focusing lens.

[0061] Figure 8 Generate a schematic diagram of the principle for the longitudinal double focusing lens.

[0062] Fig. 9 In the figure, (a) and (b) are the near-field test results of the transverse double-focusing lens under the forward incidence of the 9 GHz RCP wave; (c) and (d) are the near-field test results of the longitudinal double-focusing lens under the reverse incidence of the 9 GHz RCP wave.

[0063] Fig.10In the figure, (a) is the amplitude required for multiple beam functions under 13 GHz RCP wave incidence;

[0064] (b) The phase required for multiple beam functions under the incident RCP wave of 13 GHz; (c) The rotation angle of the second substructure of the first metal layer under the incident RCP wave of 13 GHz; (d) The rotation angle of the second substructure of the third metal layer under the incident RCP wave of 13 GHz.

[0065] Fig.11 In the figure, (a) is the simulation result of the three-dimensional radiation pattern of the multi-beam generator at 13 GHz under RCP wave incidence; (b) is the two-dimensional far-field radiation pattern with an azimuth angle of 0 degrees under RCP wave incidence; (c) is the two-dimensional far-field radiation pattern with an azimuth angle of 90 degrees under RCP wave incidence. DETAILED DESCRIPTION

[0066] Hereinafter, the technical solution provided by the present invention will be further elaborated in detail in combination with embodiments.

[0067] like Figure 1 As shown, the present invention provides a metasurface with the same amplitude modulation of circular polarization in the whole space. L =9GHz) when the right-hand circularly polarized wave is incident from the forward direction, the transverse double focusing point with arbitrary energy control is realized; when the low-frequency right-hand circularly polarized wave is incident from the reverse direction, the longitudinal double focusing point with arbitrary energy control is realized; when the high-frequency (f H =13GHz) right-hand circularly polarized wave is incident from the forward direction, and multi-beam with arbitrary control of beam direction and energy is realized. The metasurface includes M×M metasurface units arranged in an array, and M is an integer greater than 1.

[0068] like Figure 2 As shown, the metasurface provided by the present invention includes M×M metasurface units arranged in an array, where M is a natural number greater than 1. Naturally, the array includes two directions, longitudinal and transverse.

[0069] Each metasurface unit comprises a total of three metal layers (the first to third metal layers from right to left in the figure) and two dielectric substrates (the first to second dielectric substrates), wherein the first metal layer and the third metal layer have the same structure and both include a first substructure and a second substructure.

[0070] The first substructure is set as a four-tooth gear structure, with two pairs of tooth roots axially symmetrical and designed vertically.

[0071] The symmetrical tooth root lengths are respectively the transverse tooth root length l x and longitudinal tooth root length l y ; The centers of the first substructures of the first metal layer and the third metal layer are both located at the center of the unit.

[0072] The second substructure is composed of a metal ring and a symmetrical trident-shaped structure, wherein the symmetrical trident-shaped structure includes a first metal strip and a second metal strip intersecting vertically, and the first metal strip is provided with a first branch, a second branch, a third branch and a fourth branch; the first metal strip and the first to fourth branches form a symmetrical trident-shaped metal patch structure which is back to back and open outward; the trident-shaped metal patch structure is symmetrical along the axis of the first metal strip and symmetrical along the center of the intersection of the first metal strip and the second metal strip; the center of the second substructure of the first metal layer and the third metal layer are both located at the center of the unit.

[0073] Between the first substructure and the second substructure, there is also a concentric metal ring with an outer radius smaller than the inner radius of the gear ring (ie, the tooth root ring), and a width consistent with the width of the gear ring.

[0074] The longitudinal symmetrical tooth root length l of the first metal layer and the first substructure of the third metal layer y is fixed at 1.1 mm, and in different metasurface units, the transversely symmetrical tooth root length l x Adjustable from 0.1mm to 1.1mm.

[0075] In different metasurface units, by adjusting the length of the transverse tooth root, the rotation angle of the first substructure and the rotation angle of the second substructure, the following three independent functions can be achieved. Among them, the rotation angle is relative to the transverse direction of the array.

[0076] (1) When multiple metasurface units are forwardly incident with low-frequency circularly polarized waves, the different lengths of the transversely symmetric tooth roots of the first substructure of the first metal layer can achieve arbitrary regulation of the reflection amplitude between [0, 1], and the reflection phase can achieve full phase coverage in [0°, 360°] through the first substructure of the first metal layer with different rotation angles and the length of the transversely symmetric tooth roots. It should be noted that adjusting the length of the transversely symmetric tooth roots will cause a change in the reflection phase, but the amplitude of this change is limited and cannot support full phase coverage of [0°, 360°].

[0077] (2) When multiple metasurface units are incident with low-frequency circularly polarized waves in the reverse direction, the different lengths of the transversely symmetric tooth roots of the first substructure of the third metal layer can achieve arbitrary regulation of the reflection amplitude between [0, 1], and the reflection phase can achieve full phase coverage in [0°, 360°] through the first substructure of the third metal layer with different rotation angles and the length of the transversely symmetric tooth roots. It should be noted that adjusting the length of the transversely symmetric tooth roots will cause a change in the reflection phase, but the amplitude of this change is limited and cannot support full phase coverage of [0°, 360°].

[0078] (3) When multiple metasurface units are incident with circularly polarized waves in the forward / reverse direction in the high-frequency band, the first metal layer and the second substructure of the third metal layer can achieve arbitrary regulation of the transmission amplitude between [0, 1] with different rotation angle differences between [0°, 90°]. The transmission phase is determined by the rotation angle of the second substructure of the first metal layer and the rotation angle difference between the second substructures of the first metal layer and the third metal layer. In multiple metasurface units, the difference in the rotation angle can achieve full phase coverage of the transmission phase between [0°, 360°]. At this time, the rotation angle difference can be greater than 90°. That is, when the rotation angle difference is determined, the full phase coverage under the rotation angle difference can be achieved by adjusting the rotation angles of the two second substructures. Similarly, it should be noted that adjusting the angle difference will cause a change in the reflection phase, but the amplitude of this change is limited and cannot support full phase coverage of [0°, 360°]. In a metasurface unit, the rotation angle of the second substructure of the first metal layer is determined, the rotation angle difference between the two second substructures of the first metal layer and the third metal layer is determined, and then the rotation angle of the second substructure of the third metal layer is determined.

[0079] The second metal layer uses a bandpass frequency selective surface structure as a metal back plate, specifically a metal plate with an annular metal groove etched. The bandpass frequency selective surface structure is arranged on the lower surface of the first dielectric plate. L = Total reflection at 9 GHz, at f H =13GHz, high-efficiency transmission is achieved to realize efficient isolation between the reflection channel and the transmission channel; meanwhile, the reflection channel isolation of the forward and reverse incident circular polarized waves in the low frequency band is realized. Among them, the radius of the annular metal groove is smaller than the inner radius of the tooth root ring.

[0080] like Figure 2 As shown in (a), (b) and (c), optionally, the structural parameters of the metasurface unit are:

[0081] p=10mm, h=1mm, a=5.5mm, b=4.6mm, r=3.1mm, r'=3.5mm, r s =2.1mm, w S =w1=0.4mm, w2=0.2mm, l1=1.88mm, l2=3mm;

[0082] Among them, p is the period length of the metasurface unit in the x and y directions, h is the thickness of the dielectric substrate, a is the long axis of the symmetrical trident-shaped structure, b is the short axis of the symmetrical trident-shaped structure, r is the inner radius of the concentric ring, r' is the inner radius of the root ring, w2 is the width of the root ring, w1 is the width of the metal strip, l1 is the arm length of the symmetrical trident-shaped structure, and l2 is the width of the symmetrical trident-shaped structure. The distance between the short axis and the symmetrical trident-shaped structure is d, the angle between the long axis of the symmetrical trident-shaped structure of the second substructure of the first metal layer and the x-axis is θ1, the angle between the long axis of the symmetrical trident-shaped structure of the second substructure of the third metal layer and the x-axis is θ2, and w s and r s are the width and radius of the second metal circular groove, l x and l y The tooth root lengths of the four-tooth gear structure in the x and y directions are shown in Figure 1. All metal layers are made of copper with a thickness of 0.018 mm. All dielectric substrates are made of F4B with a dielectric constant of 2.65 and a loss tangent of 0.001.

[0083] The electromagnetic characteristics of the metasurface unit are analyzed as follows:

[0084] To illustrate the electromagnetic characteristics of the metasurface unit, commercial simulation software was used to perform electromagnetic simulation on the unit structure. In order to verify that the reflection and transmission channels have high isolation, the metasurface unit was simulated at low frequency f L =9GHz and high frequency f H = 13GHz, right-hand circularly polarized wave is incident in the forward direction, and the electric field distribution from the first metal layer to the third metal layer. Figure 3 As shown in (a), at low frequency f L At , a strong electric field is generated at the first substructure of the first metal layer, while the electric fields of the first substructure of the first metal layer, the second metal layer, and the third metal layer are very weak, indicating that the electromagnetic wave does not pass through the metasurface and works in the reflection mode. Figure 3 As shown in (b), the high frequency f H At the second substructure of the first metal layer and the second metal layer and the circular groove of the second metal layer, strong electric fields are generated, indicating that electromagnetic waves efficiently pass through the metasurface and work in the transmission mode.

[0085] To further illustrate the working principle of the metasurface unit, the present invention simulates the scattering coefficients of three different units. Figure 4 As shown in (a), the first substructure including the first metal layer, the first dielectric substrate and the second metal layer has two reflection bands; the scattering coefficient of the second subunit is as follows: Figure 4As shown in (b), the second substructure including the first metal layer and the third metal layer, the second metal layer, the first dielectric substrate and the second dielectric substrate has a transmission band; the scattering parameters of the overall unit are as follows Figure 4 As shown in (c), there are two reflection bands and one transmission band, and their scattering parameters are consistent with the subunits.

[0086] The process of amplitude synchronization between the reflection and transmission channels is described in detail below.

[0087] For the reflection channel, since the first substructures of the first metal layer and the third metal layer are exactly the same, the first metal layer is taken as an example. The reflection amplitude and phase satisfy

[0088]

[0089] Where α is the rotation angle of the first substructure, r RR (·) represents the reflection amplitude, Δφ is the reflection phase difference between the x- and y-polarized wave excitations, Indicates the phase, They are respectively the reflection phase of the x-line polarized wave excitation and the reflection phase of the y-line polarized wave excitation.

[0090] In order to make the reflection amplitude continuously adjustable in [0, 1], adjust In the range [0°, 180°]. Figure 5 As shown in (a), the reflection coefficient of the metasurface unit at 9 GHz changes with l under the excitation of x and y linear polarization. y The change curve of l x Reflection phase changes from 0.1mm to 1.1mm The variation range is [0°, 200°], which meets the above requirements. When the metasurface unit is excited by right-hand circular polarization, the relationship between the reflection amplitude and phase at 9 GHz and Δφ is as follows: Figure 5 As shown in (b), when Δφ is in [0°, 180°], the reflection amplitude changes in [0, 1], and the reflection phase changes in [0°, 90°]. The relationship between the reflection amplitude and phase with α is shown in Figure 5 As shown in (c), when α is in [0°, 180°], the reflection phase changes in [0°, 360°] and has almost no effect on the reflection amplitude.

[0091] For the transmission channel, the transmission amplitude and The phases satisfy:

[0092]

[0093] Δθ=θ2-θ1;

[0094] Where θ1 and θ2 are the rotation angles of the second substructure of the first metal layer and the third metal layer, respectively. The transmission amplitude and phase of the metasurface unit at 13 GHz change with right-hand circular polarization excitation as shown in the figure. Figure 5 As shown in (d), at [0°, 90°], the transmission amplitude changes in [0, 0.97], and the reflection phase changes in [0°, 88°]. When the difference Δθ between θ1 and θ2 is different, the relationship between the transmission amplitude and θ1 is as follows: Figure 5 The relationship between the transmission phase and θ1 is shown in (e). Figure 5 As shown in (f), it changes in [0, 360°] and has almost no effect on the transmission amplitude.

[0095] According to the amplitude and phase distribution required for calculating the three functions, the topological structure of the metasurface is determined to realize the three-function integrated metasurface device. L When a right-hand circularly polarized wave is incident forward, by changing the rotation angle of the first substructure of the first metal layer and l x , so that it satisfies the amplitude and phase distribution of the lateral double focusing points; when the low frequency f L When the right-hand circularly polarized wave is incident in the reverse direction, by changing the rotation angle of the first substructure of the third metal layer and l x , so that it satisfies the amplitude and phase distribution of the longitudinal double focusing points; when the high frequency f H When the right-hand circularly polarized wave is incident forward, the rotation angle of the second substructure of the first metal layer and the third metal layer is changed to satisfy the amplitude and phase distribution of the multi-beam. The topological structure of the final metasurface is as follows Figure 6 As shown, it specifically includes: the simulation structure model of the first metal layer is as follows Figure 6 (a) shows the simulation structure model of the second metal layer Figure 6 (b) shows the simulation structure model of the third metal layer Figure 6 As shown in (c); the processed samples are as follows Figure 6 As shown in (d).

[0096] The three-function metasurface with the same amplitude modulation of circular polarization in the whole space provided by the present invention can realize three electromagnetic functions according to the incident direction and frequency of electromagnetic waves, including: L =9GHz, the right-hand circularly polarized wave is incident forward to achieve a lateral double focus point; at f L = 9GHz, the right-hand circularly polarized wave is incident in the opposite direction to achieve longitudinal double focusing points; at f H =13GHz, right-hand circularly polarized wave is incident forward to achieve multi-beam.

[0097] The following is a detailed introduction to the horizontal dual focusing point function, the vertical dual focusing point function and the multi-beam function realized by the three functions.

[0098] First, we design the horizontal and vertical dual focus points:

[0099] The present invention is at low frequency f L = 9GHz, the right-hand circularly polarized wave is incident forward to realize the lateral double focusing function (x-axis), and the energy ratio of the left focus to the right focus is 1:2; at low frequency f L =9GHz, the right-hand circularly polarized wave is incident in the opposite direction to realize the longitudinal double focusing function (y-axis), and the energy ratio between the upper focus and the lower focus is 2:1.

[0100] If multiple focal points need to be generated in free space, the amplitude and phase at the corresponding position (m, n) of the metasurface can be expressed as:

[0101]

[0102] Where M is the total number of generated focal points, x(m, n) and y(m, n) represent the horizontal and vertical coordinates of the hypersurface unit in the mth row and nth column, and the number of hypersurface units is set to N×N=26×26; A j and F j denote the electric field intensity and focus of the jth focusing point, respectively, x j and j They represent the position of the jth focusing point in the x and y directions respectively, and λ is the wavelength corresponding to the operating frequency.

[0103] Horizontal dual focus function setting parameters: (x1,x2=-60mm,0mm); (y1,y2=60mm,0mm); F1=F2=140mm;

[0104] Vertical dual focus function setting parameters: (x1, x2=y1, y2=0mm, 0mm); F1=60mm; F2=150mm.

[0105] Combined with the above formula, in the low frequency band f L =9GHz lateral dual focus function required amplitude and phase distribution as Figure 7 As shown on the upper side; corresponding to the first metal layer first substructure l x Rotation angle Figure 7 As shown below. In the high frequency band f H =13GHz longitudinal dual focus function required amplitude and phase distribution are as follows Figure 8 The upper side shows: l of the first substructure of the third metal layer x and the rotation angles are Figure 8 Shown below.

[0106] When the low frequency (f L=9GHz) when the right-hand circularly polarized wave is incident in the forward direction, the electric field energy distribution of the xoy plane test at z = 140mm is as follows Fig. 9 As shown in (a), it can be seen that there are two focal spots with different energy intensities on the horizontal axis. Fig. 9 (b) is Fig. 9 In (a), y=0mm, the energy curve tested along the white line is compared with the simulation results. It can be seen that the two focal spots in the simulation are at (-60mm, 0mm) and (60mm, 0mm), and the energy size is close to 1:2. The test results verify the above design.

[0107] When the low frequency (f L =9GHz) when the right-hand circularly polarized wave is incident in the reverse direction, the electric field energy distribution of the xoz plane test at y = 0mm is as follows Fig. 9 As shown in (c), it can be seen that there are two focal spots with different energy intensities on the horizontal axis. Fig. 9 In (d), the energy curve tested along the white line at x=0mm in (c) is compared with the simulation results. It can be seen that the two focal spots are located at 60mm and 150mm, and the energy size is close to 2:1. The test and simulation results verify the above design.

[0108] Secondly, multi-beam design is performed:

[0109] The present invention is in high frequency f H = 13GHz, right-hand circularly polarized wave is incident forward to realize the three-beam function, and the three beams are pointed They are (165°, 0°), (190°, 0°) and (170°, 90°) respectively, and the energy ratio is 1:2:1. Where θ and φ represent the elevation angle and azimuth angle of the beam respectively.

[0110] If multiple beams need to be generated in free space, the amplitude and phase at the corresponding position (m, n) of the metasurface can be expressed as

[0111]

[0112] Where N is the total number of generated beams, x(m,n) and y(m,n) represent the horizontal and vertical coordinates of the hypersurface unit in the mth row and nth column, and the number of hypersurface units is set to 26×26, θ j , and A j are the elevation angle, azimuth angle and electric field strength of the jth beam respectively, p and k are the unit period and vacuum propagation constant respectively.

[0113] Setting parameters:

[0114] According to the above formula, in the high frequency band f H =13GHz multiple beam function required amplitude such as Fig.10 (a) As shown; in the high frequency band f H = The phase required for the multiple beam function at 13 GHz is as follows Fig.10 As shown in (b); the corresponding rotation angle θ1 of the second substructure of the first metal layer is as follows Fig.10 As shown in (c); the rotation angle θ2 of the second substructure of the third metal layer is as follows Fig.10 As shown in (d).

[0115] When high frequency (f H =13GHz) The simulated three-dimensional far-field pattern results when the right-hand circularly polarized wave is incident forward are as follows Fig.11 As shown in (a), it can be seen that there are three beams with different directions and energies. The two-dimensional far-field pattern of the test with an azimuth angle of 0° is shown in Fig.11 As shown in (b); the two-dimensional far-field pattern of the test with an azimuth angle of 90° is as follows Fig.11 As shown in (c), the simulation values ​​are also given for comparison, and it can be seen that the directions and energies of the three beams are consistent with the design.

[0116] From the above verification, it can be seen that the three-function metasurface with the same modulation of circularly polarized wave amplitude in the whole space proposed by the present invention can independently regulate the amplitude and phase of circularly polarized waves in three channels in the whole space under the action of circularly polarized waves based on frequency and direction multiplexing. Compared with the existing adjustable and regulated transmission metasurfaces, the unit structure design is simple and the thickness is only 2mm. The present invention can obtain high reflection and transmission efficiency with only three metal layers and two dielectric layers, while the existing technology requires four metal layers, two dielectric layers and one air layer to achieve amplitude modulation and phase modulation of circularly polarized waves, and the thickness is 13.5mm. The transmission efficiency of the two transmission channels is 0.9 and 0.83.

[0117] In summary, it can be seen that the technical solution provided by the present invention has the beneficial effects of small size and low profile of the super surface.

[0118] Furthermore, each preferred scheme has achieved the following technical effects on the basis of the above-mentioned technical effects: different lengths of the transverse tooth roots can independently modulate the amplitude of the circularly polarized wave in the reflection channel of the low frequency band of the forward / reverse incidence; different rotation angles of the first substructure can independently modulate the phase of the circularly polarized wave in the reflection channel of the low frequency band of the forward / reverse incidence; the rotation angle difference of the second substructure can independently modulate the amplitude of the circularly polarized wave in the transmission channel of the high and low frequency bands of the forward / reverse incidence; the rotation angle difference of the second substructure can independently modulate the phase of the circularly polarized wave in the transmission channel of the high and low frequency bands of the forward / reverse incidence.

[0119] It can be seen that each preferred scheme can realize the flexible control of circularly polarized electromagnetic waves in three channels in the whole space, and has a high degree of integration; it can independently realize three functions: energy-adjustable transverse dual focusing points, energy-adjustable longitudinal dual focusing points, and multi-beam with adjustable beam direction and energy, with rich functions and high working efficiency.

Claims

1. A metasurface with the same amplitude modulation of circular polarization in the whole space, characterized in that: It includes M×M metasurface units arranged in an array, where M=2, 3, 4, ...; The metasurface unit includes a first metal layer, a first dielectric layer, a second metal layer, a second dielectric layer and a third metal layer arranged in sequence from top to bottom; The first metal layer includes a first substructure and a second substructure each consisting of a metal strip; The first substructure is a gear, comprising a gear ring and four tooth roots equidistantly distributed along the gear ring; wherein two transverse tooth roots are of equal length and two longitudinal tooth roots are of equal length; Concentric rings are provided inside the gear ring of the first substructure; The second substructure is arranged in the concentric rings, and includes a double E structure and a cross structure; the double E structure has opposite openings and two symmetry axes passing through the center of the toothed ring; the cross structure coincides with the two symmetry axes; The second metal layer is a metal plate with a circular metal groove etched therein, wherein the radius of the circular metal groove is smaller than the inner radius of the gear ring; The third metal layer has the same structure as the first metal layer.

2. A metasurface with the same amplitude modulation of circular polarization in the whole space as claimed in claim 1, characterized in that: l x1,i ≠l x1,j ； Where i and j are the serial numbers of the supersurface units, i∈(1,2,...,N), j∈(1,2,...,N), i≠j, N=M×M; l x1,i , l x1,j are the lengths of the transverse tooth roots of the first metal layer in the i-th and j-th metasurface units, respectively; l x,min , l x,max are respectively the minimum and maximum lengths of the transverse tooth roots of all the first metal layers in the super surface.

3. The metasurface with the same amplitude modulation of circular polarization in the whole space as claimed in claim 1, characterized in that: α 1,i ≠α 1,j ； Where i and j are the serial numbers of the hypersurface units, i∈(1,2,...,N), j∈(1,2,...,N), i≠j, N=M×M; α 1,i , α 1,j are respectively the rotation angles of the first substructure of the first metal layer in the ith and jth metasurface units relative to the lateral direction of the array.

4. The metasurface with the same amplitude modulation of circular polarization in the whole space as claimed in claim 1, characterized in that: l x2,i ≠l x2,j ； Where i and j are the serial numbers of the supersurface units, i∈(1,2,...,N), j∈(1,2,...,N), i≠j, N=M×M; l x2,i , l x2,j are the lengths of the lateral tooth roots of the third metal layer in the i-th and j-th supersurface units, respectively.

5. The metasurface with the same amplitude modulation of circular polarization in the whole space as claimed in claim 1, characterized in that: α 2,i ≠α 2,j ； Where i and j are the serial numbers of the hypersurface units, i∈(1,2,...,N), j∈(1,2,...,N), i≠j, N=M×M; α 2,i , α 2,j are respectively the rotation angles of the first substructure of the third metal layer in the ith and jth metasurface units relative to the lateral direction of the array.

6. The metasurface with the same amplitude modulation of circular polarization in the whole space as claimed in claim 1, characterized in that: Dth i ≠Δθ j ; Where i and j are the serial numbers of the hypersurface units, i∈(1,2,...,N), j∈(1,2,...,N), i≠j, N=M×M; Δθ i , Δθ j are the rotation angle differences between the two second substructures of the first metal layer and the third metal layer in the i-th and j-th metasurface units respectively.

7. The metasurface with the same amplitude modulation of circular polarization in the whole space as claimed in claim 1, characterized in that: i 1,i ≠θ 1,j ;Dth i ∈[0°, 360°); Where i and j are the serial numbers of the hypersurface units, i∈(1,2,...,N), j∈(1,2,...,N), i≠j, N=M×M; θ 1,i ,θ 1,j are the rotation angles of the second substructure of the first metal layer in the i-th and j-th metasurface units relative to the horizontal direction, θ 2,i ,θ 2,j are respectively the rotation angles of the second substructure of the third metal layer in the i-th and j-th metasurface units relative to the lateral direction of the array.

8. The metasurface with the same amplitude modulation of circular polarization in the whole space as claimed in claim 1, characterized in that: The period of the metasurface unit is 10 mm; In each metasurface unit, The first metal layer, the second metal layer and the third metal layer are all made of copper, and the thickness is 0.018mm; The first dielectric layer and the second dielectric layer are both made of F4B material with a dielectric constant of 2.65 and a loss tangent of 0.001, and the thickness is 1mm; The length of the longitudinal tooth root is 1.1 mm; the length of the transverse tooth root is between 0.15 mm and 1.1 mm; The inner radius of the toothed ring is 3.5mm and the width is 0.2mm; the inner radius of the concentric ring is 3.1mm and the width is 0.2mm; In the second substructure, the width of the metal strips is 0.4 mm; In the cross structure, the length of the metal strip connecting the double E structure is 5.5 mm, and the length of the other metal strip is 4.6 mm; In the double-E structure, the height of the letter E is 3.8 mm and the width is 1.88 mm; In the second metal layer, the circular ring metal groove has a width of 0.4 mm and an inner radius of 2.1 mm.

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