Triple-band full-space circular polarization amplitude-co-modulated metasurface integrator and design method

Abstract

The present invention belongs to the technical field of multifunctional electromagnetic metasurfaces, specifically a three-band full-space circularly polarized amplitude-co-modulated metasurface integrator and a design method. The metasurface integrator is composed of M*M metasurface units arranged in a plane; the metasurface unit is composed of 4 layers of metal structure, 2 layers of dielectric plates and an air layer; the first metal layer and the second metal layer are etched on the upper and lower surfaces of the first dielectric plate, and the third metal layer and the fourth metal layer are etched on the upper and lower surfaces of the second dielectric plate; the first metal layer structure is an X-shaped metal patch unit; the second metal layer is a metal backplane etched with double circular ring metal grooves; the third metal layer and the fourth metal layer are the same size, the outer ring is composed of two complementary double open ring groove resonators, and the inner ring is composed of an improved double open ring metal resonator. The three-band full-space circularly polarized amplitude-co-modulated metasurface integrator of the present invention can realize full-space electromagnetic regulation in different frequency bands, and has the advantages of high integration, good isolation and easy processing.

Description

Technical Field

[0001] The present invention relates to the technical field of metasurface electromagnetic control, and in particular to a three-band full-space circularly polarized amplitude-phase modulation metasurface integrator and a design method thereof. Background Art

[0002] In recent years, the research and development of metasurfaces has been in full swing. With the deepening of the understanding of metasurfaces, metasurfaces have also shown trends such as multi-function, digitalization, reconfiguration, and intelligence, and have emerged, including vortex beam / Bessel beam generators, polarization converters, beam splitters, reflection / transmission array antennas, etc. However, the above-mentioned metasurface devices mainly focus on the phase control of the metasurface, while ignoring the amplitude control. Through the joint modulation of amplitude and phase, the metasurface can present many novel functions, such as multi-beam generators, low sidelobe antennas, high-quality hologram generation, etc. Early research on the joint modulation of metasurface amplitude and phase mainly focused on the field of linear polarization, while the amplitude and phase control of circular polarization mainly included three methods: dual geometric phase, transmission and geometric phase hybrid modulation, and loading impedance unit. However, the amplitude phase modulation based on metasurfaces reported so far is mostly limited to a single frequency band and reflection mode, and there are few reports on the research on achieving full-space multi-band amplitude phase modulation. In particular, the control research of full-space metasurfaces in multi-band amplitude phase modulation is still in the primary research stage. Summary of the invention

[0003] The present invention discloses a transmission-reflection-transmission three-band full-space metasurface integrated device and its design method based on the reflection amplitude isotropic and dual-band transmission amplitude isotropic metasurface. The metasurface integrated device can electromagnetically control electromagnetic waves under linear polarization and circular polarization separately, and has the advantages of easy processing, small profile, reconfigurability and high efficiency.

[0004] Specifically, the present invention provides a three-band full-space circular polarization amplitude-coherent metasurface integrator, wherein the three-band full-space circular polarization amplitude-coherent metasurface integrator is composed of M*M metasurface units of the same size arranged in a plane at equal intervals and periodically extended;

[0005] The metasurface unit includes, from top to bottom, a first metal layer, a first dielectric plate, a second metal layer, an air layer, a third metal layer, a second dielectric plate and a fourth metal layer, and the period of the metasurface unit is p;

[0006] The first metal layer and the second metal layer are arranged on the upper and lower surfaces of the first dielectric plate, the third metal layer and the fourth metal layer are arranged on the upper and lower surfaces of the second dielectric plate, and an air layer is between the second metal layer and the third metal layer;

[0007] The first metal layer is an X-shaped metal structure, which is composed of two crossed metal structure strips. The length of the metal structure strip is L, the width is w, and the difference in rotation angle between the two metal structure strips is α. 2 ; The X-shaped metal structure rotates at an angle of β to the x-axis 2 ;

[0008] The second metal layer is a double concentric ring metal gap structure opened on the metal layer of the same size as the super surface unit. The double concentric ring metal gap structure is a metal layer with two concentric metal gap inner rings and a metal gap outer ring. The inner diameter and outer diameter of the metal gap inner ring are R 4 and R 3 , the inner and outer diameters of the outer ring of the metal gap are R 2 and R 1 ;

[0009] The third metal layer and the fourth metal layer adopt the same structure, both of which include substructure 1 and substructure 2; the outer edge of substructure 1 is the same size as the super surface unit, and the inner edge is a radius of R 7 The circle, substructure 1 is provided with an outer ring double C-slot resonator;

[0010] The double C-slot resonator includes an outer ring C-slot resonator and an inner ring C-slot resonator; the outer ring C-slot resonator is two concentric arcs, and the outer and inner diameters are both R 11 and R 10 , and the C-shaped arcs with the same curvature; the inner ring C-shaped slot resonator is composed of two concentric arcs, and the outer and inner diameters are both R 9 and R 8 , and the C-shaped arcs with the same curvature; the gap between the outer ring C-shaped slot resonator and the inner ring C-shaped slot resonator is at a 90-degree angle; the rotation angles of the double C-shaped slot resonators of the third metal layer and the fourth metal are θ 1 and θ 3 ;

[0011] The substructure 2 adopts an inner ring double C-shaped open metal resonant ring, and the double C-shaped open metal resonant ring is two concentric arcs, and the outer diameter and inner diameter are both R 6 and R 5 , and the arc is composed of C-shaped arcs with the same curvature. The gap width between the two C-shaped arcs is g. There are T-shaped branches on the inner side of the two C-shaped arcs. The length of the horizontal branch connected to the arc is L 2 , the length of the vertical branch perpendicular to it is L 1 The rotation angles of the double C-shaped open metal resonant rings of the third metal layer and the fourth metal layer are θ 2 and θ 4 .

[0012] Furthermore, the X-shaped metal structure is formed by controlling the difference α between the rotation angles of the crossed metal structure strips. 2 Control amplitude. In the range of [60°, 90°], the reflection amplitude gradually decreases from 1 to 0, and the phase remains basically unchanged;

[0013] The reflection amplitude and phase of the X-shaped metal structure can be independently adjusted by changing the x-axis rotation angle β 2 , we can get 2β 2 The reflection phase change;.

[0014] Furthermore, the dual C-slot resonator is configured to control the difference in rotation angle α. 1 Control amplitude, α 1 =θ 3 -θ 1 In the range of [0°, 60°], the reflection amplitude gradually decreases from 0.9 to 0, and the phase remains basically unchanged;

[0015] The double C-slot resonator is rotated by changing the overall rotation angle β 1 , β 1 =(Ω 3 +θ 1 ) / 2, we get 2β 1 The reflected phase changes, and the amplitude remains basically unchanged.

[0016] Furthermore, the double C-type open resonant ring controls the difference α between the upper and lower rotation angles. 3 Control amplitude, α 3 =Ω 4 -θ 2 In the range of [0°, 60°], the reflection amplitude gradually decreases from 0.83 to 0, and the phase remains basically unchanged;

[0017] The double C-type split resonant ring is rotated by changing the overall rotation angle β 3 , β 3 =(θ 4 +θ 2 ) / 2, we get 2β 3 The reflected phase changes, and the amplitude remains basically unchanged.

[0018] Furthermore, the structural parameters optimized by the metasurface unit are as follows:

[0019] The metasurface unit period p = 11 mm, the first dielectric plate thickness h 1 =3mm, the thickness of the second dielectric plate h 2 =8mm, air layer thickness h 3 =2.5mm;

[0020] The first metal layer, the second metal layer, the third metal layer and the fourth metal layer are made of copper with a thickness of 0.036 mm;

[0021] The length of the metal structure strip is L = 6 mm, and the width is w = 0.3 mm;

[0022] Inner diameter R of the inner ring of the metal gap 4 =2.28mm, the outer diameter of the inner ring of the metal gap R 3 =3.08mm, inner diameter R of the outer ring of the metal gap 2 =4.7mm, the outer diameter of the metal gap outer ring R 1 =12mm;

[0023] Outer ring C-slot resonator outer diameter R 11 =5.4mm, the inner diameter of the outer ring C-slot resonator R 10 =5.2mm, the outer diameter of the inner ring C-slot resonator R 9 =5mm, inner diameter R of inner ring C-slot resonator 8 =4.8mm, the inner edge of the double C-slot resonator is radius R 7 =4.1mm;

[0024] Double C-shaped open metal resonant ring outer diameter R 6 =2.2mm, inner diameter R of double C-shaped open metal resonant ring 5 =2.5mm, horizontal branch length L 2 =1mm, vertical branch length L 1 =1.6mm, the gap width between the C-shaped arcs g=1.1mm.

[0025] A method for designing a three-band full-space circular polarization amplitude-coherent metasurface integrator is also provided. The method for designing a three-band full-space circular polarization amplitude-coherent metasurface integrator comprises the following steps:

[0026] Step 1: Use a dual-bandpass frequency selective surface structure to replace the metal backplane to construct a transflective isolation mode; the dual-bandpass frequency selective surface structure is a double concentric ring metal gap structure, which is arranged on the lower surface of the first dielectric plate. M = Total reflection at 10.2 GHz, at f L =7GHz and f H =High transmission at 15.7 GHz;

[0027] Step 2: Introduce an X-shaped metal structure into the metasurface to construct an intermediate frequency f M The X-shaped metal structure is arranged on the upper surface of the first dielectric plate, and the co-polarization reflection band of the unit is made to overlap with the reflection band of the dual-bandpass frequency selective surface structure through parameter scanning;

[0028] Step 3: introduce double C-shaped metal slots and split resonant rings into the metasurface to construct a low-frequency f L =7GHz and high frequency f H =Dual-band high-efficiency transmission mode and amplitude and phase regulation at 15.7GHz; the double C-shaped metal grooves and the open resonant ring are respectively arranged on the upper and lower surfaces of the second dielectric plate, and the two cross-polarization transmission bands of the unit are overlapped with the two transmission bands of the dual-band pass frequency selective surface structure through parameter scanning;

[0029] Step 4: synthesize the final four-layer structure with both transmission and reflection, and evaluate the isolation between the transmission and reflection frequency bands; cascade to form a final four-layer unit structure with both transmission and reflection modes, so that the final metasurface can realize the joint modulation of the amplitude and phase of the transmission wave and the reflection wave in three frequency bands;

[0030] Step 5: Determine the topological structure of the metasurface based on the calculated three amplitude and phase distributions to realize a three-function integrated metasurface device.

[0031] Furthermore, it is characterized in that the X-shaped metal structure is formed by controlling the difference α between the rotation angles of the crossed metal structure strips. 2 Control amplitude. In the range of [60°, 90°], the reflection amplitude gradually decreases from 1 to 0, and the phase remains basically unchanged;

[0032] The reflection amplitude and phase of the X-shaped metal structure can be independently adjusted by changing the x-axis rotation angle β 2 , we can get 2β 2 The reflected phase changes.

[0033] Furthermore, the dual C-slot resonator is configured to control the difference in rotation angle α. 1 Control amplitude, α 1 =θ 3 -θ 1 In the range of [0°, 60°], the reflection amplitude gradually decreases from 0.9 to 0, and the phase remains basically unchanged;

[0034] The double C-slot resonator is rotated by changing the overall rotation angle β 1 , β 1 =(θ 3 +θ 1 ) / 2, we get 2β 1 The reflected phase changes, and the amplitude remains basically unchanged.

[0035] Furthermore, the double C-type open resonant ring controls the difference α between the upper and lower rotation angles. 3 Control amplitude, α 3 =Ω 4 -θ 2In the range of [0°, 60°], the reflection amplitude gradually decreases from 0.83 to 0, and the phase remains basically unchanged;

[0036] The double C-type split resonant ring is rotated by changing the overall rotation angle β 3 , β 3 =(θ 4 +θ 2 ) / 2, we get 2β 3 The reflected phase changes, and the amplitude remains basically unchanged.

[0037] The beneficial effects achieved by the present invention are:

[0038] The three-band multifunctional metasurface designed in the present invention has a high degree of integration. It can generate multiple vortex beams of arbitrary modes in any direction through complex amplitude superposition modulation, which is of great significance in regional coverage blind spot filling, hybrid beamforming, reducing channel fading and improving channel quality of communication systems.

[0039] The present invention has the advantage of fewer design steps in multi-band functional integration. Due to the effects of the frequency selective surface and the air layer, the isolation between reflection and transmission is better, and compared with the previous frequency multiplexing metasurface, the performance is better, which improves the functional upper limit of the multi-frequency metasurface, and realizes functions that cannot be achieved by phase-only or amplitude-only modulation metasurfaces through amplitude phase synchronization. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Schematic diagram of the functions of multi-band multi-functional integrated metasurface devices.

[0041] Figure 2 Schematic diagram of the full-space metasurface unit structure. (a) Side view of the three-band full-space amplitude phase modulation unit; (b) X-shaped unit diagram of the upper dielectric plate; (c) FSS unit diagram of the lower dielectric plate; (d) Unit structure diagram of the lower dielectric plate; (ef) Unit structure relationship diagram of the lower dielectric plate.

[0042] Figure 3 The scattering parameter diagram of the unit simulation. (a) Upper unit; (b) Lower unit; (c) Overall unit of the upper and lower layers combined.

[0043] Figure 4 The current distribution on the lower dielectric plate surface. (a) 7 GHz; (b) 15.7 GHz.

[0044] Figure 5 For LCP plane wave at vertical incidence, (ab) 7, (cd) 10.2, (ef) 15.72 GHz, different α i The amplitude and phase change curves under α i When constant, different βi Comparison of the simulated and theoretically calculated reflection phase curves, i=1,2,3.

[0045] Figure 6 (a) Different α under LCP plane wave incidence 1 The corresponding co-polarization reflection amplitude and (b) co-polarization reflection phase change curve; (c) different α 1 The corresponding cross-polarization transmission amplitude and (d) cross-polarization transmission phase.

[0046] Figure 7 (a) Different α under LCP plane wave incidence 2 The corresponding cross-polarization transmission amplitude and (b) cross-polarization transmission phase curves.

[0047] Figure 8 The amplitude and phase electromagnetic characteristics of the unit under LCP plane wave incidence. (a) Different α 3 (a) Cross-polarization transmission amplitude and (b) cross-polarization transmission phase; (c) different α 3 (a) Co-polarization reflection amplitude and (b) Co-polarization reflection phase change curves.

[0048] Fig. 9 The simulation structure model of the three-band full-space amplitude-coherent metasurface. (a) The first layer; (b) The second layer; (c) The third layer; (d) The fourth layer.

[0049] Fig.10 Schematic diagram of the y-axis double vortex beam generation principle.

[0050] Fig.11 Schematic diagram of the x-axis double vortex beam generation principle.

[0051] Fig.12 The three-dimensional far-field (a, b) amplitude radiation patterns and (c, d) phase radiation patterns of RCP waves at (a, c) 7 GHz and (b, d) 10.2 GHz obtained by simulation under LCP wave incidence.

[0052] Fig.13 Two-dimensional far-field radiation patterns of RCP waves with an azimuth angle of 90 degrees at (a) 7 GHz and an azimuth angle of 0 degrees at (b) 10.2 GHz under LCP wave incidence.

[0053] Fig.14 The near-field test results at (ad) 7 GHz and (eh) 10.2 GHz under LCP wave incidence. The (a, c, e, g) amplitude distribution and (b, d, f, g) phase distribution of the RCP wave measured at the corresponding beam vertical plane.

[0054] Fig.15 Schematic diagram of the x-axis dual focus generation principle.

[0055] Fig.16 (a) The dual focus simulation results of the xoz plane and (b) the xoy plane simulation results at z = -150 mm under LCP wave incidence. DETAILED DESCRIPTION

[0056] The technical solution of the present invention is described in more detail below in conjunction with the accompanying drawings. The present invention includes but is not limited to the following embodiments.

[0057] The three-band multifunctional integrated metasurface device provided by the present invention is a multifunctional reconfigurable transmission metasurface integrated device which can be regulated under both linearly polarized waves and circularly polarized waves based on a transmission-type isotropic unit constructed by reflection amplitude and phase regulation and dual-frequency.

[0058] like Figure 1 As shown in the figure, the invented three-band multifunctional integrated metasurface device has a L =7GHz, LCP wave incident to achieve the lower y-axis double vortex beam; at f M = 10.2 GHz, LCP wave incident to achieve the lower x-axis double vortex beam; at f H =15.7GHz, the LCP wave is incident to achieve the lower x-axis dual focus.

[0059] The three-band multifunctional integrated metasurface device provided by the present invention is composed of M*M metasurface units with the same size arranged in a plane with equal spacing and periodic extension; wherein the metasurface unit is a multi-layer structure; the metasurface unit is composed of 4 metal structure layers, 2 dielectric plates and an air layer; the metal layers are numbered as the first metal layer, the second metal layer, the third metal layer and the fourth metal layer from top to bottom; each metal structure is printed on an F4B dielectric plate; the first metal layer is an X-shaped metal structure, the second metal layer is a double concentric circular ring metal gap structure, which is respectively located on the upper and lower surfaces of the upper dielectric plate; the third metal layer and the fourth metal layer are respectively located on the upper and lower surfaces of the second dielectric plate, the metal unit structural parameters are exactly the same, the outer ring of the lower unit is composed of a double C-shaped slot resonator, and the inner ring is composed of an improved double C-shaped open metal resonant ring, and only the rotation angle is different; the two dielectric plates are separated by an air layer; the metasurface unit can work under circularly polarized waves, and the amplitude can be controlled by changing the difference in rotation angles, and the overall rotation angle controls the phase to achieve amplitude-phase joint modulation;

[0060] like Figure 2 As shown in the figure, the structural parameters of each unit are set as follows: the width of the X-shaped metal structure strip is w, and the length is L; the outer diameter and inner diameter of the outer ring of the double C-slot resonator and the outer diameter and inner diameter of the inner ring are R 11 , R 10 , R 9 , R 8; The outer and inner diameters of the improved double C-type open resonant ring are R 6 , R 5 , the gap width is g, and the lengths of the branches extending in the middle are L 1 , L 2 ; The inner and outer diameters of the inner ring of the double concentric ring metal gap are R 4 and R 3 , the inner and outer diameters of the outer ring are R 2 and R 1 ;h 1 is the thickness of the first dielectric plate, h 3 is the thickness of the second dielectric plate; the period is p, which is the length of the metasurface unit. 1 and θ 3 are the rotation angles of the upper and lower layers of the double C-slot resonator, θ 2 and θ 4 They are the rotation angles of the upper and lower layers of the improved double C-type open resonant ring. Among them, the dielectric plate is made of polytetrafluoroethylene F4B, with a dielectric constant of 2.65 and an electrical tangent loss of 0.001.

[0061] According to the requirements of the three-band multifunctional integrated metasurface device, the present invention also provides a design method for a three-band full-space circularly polarized phase-modulated metasurface integrator, which specifically includes:

[0062] Step 1: Use a dual-bandpass frequency selective surface structure (FSS) instead of a metal backplane to construct a transflective isolation mode;

[0063] Inspired by the frequency selective surface, in order to build a good isolation mode in the transmission frequency band and reflection frequency band of the metasurface, a dual-bandpass frequency selective surface structure (FSS) is used here to replace the metal backplane and is placed at the bottom of the first dielectric plate and on the back of the X-shaped metal structure. M Total reflection at f L and f H High transmittance.

[0064] like Figure 2 As shown in (a) and (c), the dual-bandpass FSS is a double concentric ring metal gap structure, where the inner and outer diameters of the inner and outer rings are R 4 , R 3 , R 2 , R 1 , located at the bottom of the upper dielectric plate. Since the air layer isolates the two dielectric plates, the isolation between the transmission and reflection frequency bands is good.

[0065] Step 2: Introduce an X-shaped metal structure into the metasurface to construct an intermediate frequency f M Efficient reflection mode and amplitude and phase control at:

[0066] For the dual-bandpass FSS, in order to construct an efficient joint control of amplitude and phase in the reflection frequency band, an X-shaped metal unit is introduced on the top of the first dielectric plate. Through parameter scanning, the co-polarization reflection band of the unit is made to coincide with the reflection frequency band of the FSS, and the two transmission frequency bands of the FSS are hardly affected. Finally, through the principle of dual geometric phase, the design realizes the amplitude phase tuning of the unit in the reflection frequency band.

[0067] like Figure 2 As shown in (b), the width of the two metal strips of the X-shaped metal structure is w and the length is L. Through parameter scanning optimization, its reflection frequency band is located in the middle of the two transmission frequency bands of FSS. The simulation results are shown in Figure 3 As shown in (a), the upper dielectric plate unit composed of FSS and X-type metal units has a co-polarization reflection band and two transmission bands; Figure 5 As shown in (cd), the X unit controls the difference in rotation angle α 2 Control amplitude, in the range of [60°, 90°], the reflection amplitude gradually decreases from 1 to 0, and the phase remains basically unchanged, and by changing the overall rotation angle β 2 , we can get 2β 2 The reflection phase changes, and the amplitude remains basically unchanged. It can be seen that the reflection amplitude and phase can be basically independently and freely regulated; therefore, according to the α in the curve 2 With amplitude and β 2 Corresponding relationship with phase, every time an amplitude is determined, the corresponding angle α can be obtained according to the curve 2 Similarly, for each phase determined, the corresponding angle β can be obtained according to the curve 2 .

[0068] Step 3: introduce double C-shaped metal slots and split resonant rings into the metasurface to construct a low-frequency f L and high frequency f H Dual-band high-efficiency transmission mode and amplitude and phase control at:

[0069] Double C-shaped metal slots and split resonant rings were introduced on the second dielectric plate. The two cross-polarization transmission bands of the unit were made to coincide with the two transmission bands of FSS by parameter scanning. Finally, based on the principle of dual geometric phase, the unit was designed to have the same amplitude phase modulation in the transmission band. Figure 2 As shown in (de), the lower dielectric plate unit consists of two parts, the outer part is a double C-shaped slot resonator, and the inner part is an improved double C-shaped open resonant ring. The outer ring radius and inner ring radius of the double C-shaped slot resonator are R 11 , R 10 , R 9 , R 8 ; The outer and inner diameters of the improved double C-type open resonant ring are R 6 , R 5, the gap width is g, and the lengths of the branches extending in the middle are L 1 , L 2 ,like Figure 3 As shown in (b), the cross-polarization transmission frequency band is made to coincide with the two transmission frequency bands of FSS through parameter scanning optimization; Figure 4 As shown, at low frequency f L At the point, a strong current is generated in the gap of the outer double C-shaped metal ring, while the current is almost zero when it reaches the inner metal ring. Similarly, in the high frequency band f H At the inner improved double C-shaped ring, a strong surface current is generated, but there is almost no current in the outer ring. Figure 5 As shown in (ab), the double C-slot resonator controls the difference in rotation angle α 1 Control amplitude, rotation angle difference α 1 There is a one-to-one corresponding curve between the amplitude and the amplitude. Through simulation, we get an α 1 The corresponding database between the amplitude and the amplitude, for any amplitude between 0-1, select the corresponding α through the curve 1 That’s it; where α 1 =θ 3 -θ 1 , in the range of [0°, 60°], the reflection amplitude gradually decreases from 0.9 to 0, and the phase remains basically unchanged, and by changing the overall rotation angle β 1 , where β 1 =(θ 3 +θ 1 ) / 2, we can get 2β 1 The reflection phase changes, and the amplitude remains basically unchanged; similarly, Figure 5 As shown in (ef), the improved double C-type split resonant ring controls the difference α between the upper and lower layers 3 Control amplitude, rotation angle difference α 3 There is a one-to-one corresponding curve between the amplitude and the amplitude. Through simulation, we get an α 3 The corresponding database between the amplitude and the amplitude, for any amplitude between 0-1, select the corresponding α through the curve 3 That’s it; where α 3 =θ 4 -θ 2 , in the range of [0°, 60°], the reflection amplitude gradually decreases from 0.83 to 0, and the phase remains basically unchanged, and by changing the overall rotation angle β 3 , where β 3 =(θ 4 +Ω 2 ) / 2, we can get 2β 3 The reflection phase changes, and the amplitude remains basically unchanged. It can be seen that the amplitude and phase of the transmission in the two frequency bands can be basically regarded as independent regulation.

[0070] In order to more accurately ensure the correspondence between angle, amplitude and phase, a large number of parameter scans were performed to establish α i and β i (i=1,2,3) and the corresponding database between amplitude and phase. Every time you need an amplitude between 0-1 and a phase between 0-360°, you can find the corresponding α in the database. i and β i ,like Figure 5 (af) shown.

[0071] Step 4, synthesizing the final four-layer structure with integrated transmission and reflection, and evaluating the isolation between the transmission and reflection frequency bands;

[0072] With the unit structures of efficient reflection and dual-frequency transmission designed in the first two steps, a four-layer unit structure with both transmission and reflection modes can be cascaded to form a final structure, and the transmission and reflection frequency bands are highly isolated, so that the final metasurface can realize the joint modulation of the amplitude and phase of the transmitted wave and the reflected wave in three frequency bands.

[0073] like Figure 3 As shown in (c), the scattering parameters of the overall unit can be obtained by combining the units. It can be seen that the overall unit has a co-polarization reflection band and two cross-polarization transmission bands. Next, the independence of the three frequency bands of the unit is simulated and analyzed. Since the unit itself has a certain rotational symmetry, it is only necessary to consider the influence of the difference in the rotation angles of the three units on the amplitude and phase change characteristics of the three frequency bands.

[0074] First combine Figure 6 , the difference in unit rotation angle α 1 When f changes M = The co-polarization reflection amplitude and reflection phase at 10.2 GHz are almost unchanged. Similarly, f H = The cross-polarization transmission amplitude and transmission phase at 15.7 GHz also have almost no change. Figure 7 and Figure 8 They represent the difference in unit rotation angle α 2 and α 3 When the frequency band changes, the amplitude and phase of the other two frequency bands hardly change, the amplitude change range is less than 0.1, and the phase change range is within 20°. In summary, the three frequency bands can be regarded as independent of each other.

[0075] Step 5, determining the topological structure of the metasurface according to the calculated three amplitude and phase distributions, and realizing a three-function integrated metasurface device;

[0076] In the reflection frequency band f MBy changing the difference in the rotation angles of the two metal arms of the X-shaped metal structure, α 2 and the overall rotation angle to control the reflection amplitude and phase so that it satisfies the amplitude and phase distribution of the y-axis double vortex beam; similarly, in the transmission frequency band f L and f H By changing the difference α between the rotation angles of the double C-shaped metal grooves on the upper and lower surfaces and the split resonant ring structure 1 , α 3 The transmission amplitude and phase are controlled by the overall rotation angle to satisfy the amplitude and phase distribution of the x-axis double vortex beam and the x-axis double focus. The final topological structure of the metasurface is as follows Fig. 9 shown.

[0077] According to the method of the present invention, the optimized structural parameters are as follows: p = 11 mm, g = 1.1 mm, w = 0.3 mm, L 1 =1.6mm, L 2 =1mm, L=6mm, R 1 =12mm, R 2 =4.7mm, R 3 =3.08mm, R 4 =2.28mm, R 5 =2.5mm, R 6 =2.2mm, R7=4.1mm, R 8 =4.8mm, R 9 =5mm, R 10 =5.2mm, R 11 =5.4mm,h 1 =3mm,h 2 =8mm,h 3 =2.5mm; the metal is copper with a thickness of 0.036mm.

[0078] In one embodiment, the triple-band multifunctional integrated metasurface device is L =7GHz, LCP wave incident to achieve the lower y-axis double vortex beam; at f M = 10.2 GHz, LCP wave incident to achieve the lower x-axis double vortex beam; at f H =15.7GHz, the LCP wave is incident to achieve the lower x-axis dual focus.

[0079] In order to realize the triple-band multifunctional integrated metasurface device, the x-axis and y-axis double vortex beam design is first carried out:

[0080] The present invention is at low frequency f L =7GHz, the function of the Y-axis double vortex beam in the transmission mode is designed, and at low frequency f M= The function of the x-axis double vortex beam in the transmission mode is designed at 10.2 GHz. Here, we predetermine the deflection directions of the two transmission vortex beams to be (30°, 0°) and (45°, 180°), and the pointing angles of the two reflected vortices to be (45°, 90°) and (30°, 270°).

[0081] If multiple vortex beams need to be generated in free space, the superposition of the complex amplitudes of the electric field at the corresponding positions (x, y) of the metasurface can be expressed as:

[0082]

[0083] In the above formula, N is the total number of vortex beams generated, x and y represent the horizontal and vertical coordinates of the metasurface unit, and l n refers to the mode number of the nth vortex beam, θ n and They refer to the elevation angle and azimuth angle of the nth beam, respectively. f represents the operating frequency. A n is the power coefficient of the nth beam and can be used to adjust the size of each beam. c refers to the speed of light, l i Represents the topological charge of the vortex beam.

[0084] According to formula 1, in the low frequency band f L =7GHz produces a y-axis double vortex beam at the intermediate frequency f M =10.2GHz to generate an x-axis double vortex beam. In order to simplify the design process, a circularly polarized plane wave is used to excite the metasurface. The amplitude and phase distribution of the electromagnetic wave before reaching the metasurface are uniform. The required phase distributions are as follows: Fig.10 and 11 As shown on the left. Then, the complex amplitude of the electric field is superimposed according to Formula 1, and finally we get Fig.10 and 11 Amplitude and phase distribution on the right.

[0085] like Fig.12 As shown, the two figures above are the three-dimensional far-field radiation amplitude patterns of time domain simulation, and the two figures below are the far-field phase patterns. It can be seen that the radiation amplitude pattern shows two obvious deflected beams, and there is an obvious depression in the center of the beam; the two figures below are the radiation phase patterns of four beams in two frequency bands. It can be seen that from the cross-section of each beam radiation direction, the phase distribution is fan-shaped around the center point, which is an obvious vortex phase distribution. Fig.13 The left and right pictures are f L = 2D far-field pattern at 7 GHz with an azimuth angle of 90°, and f M= 2D far-field pattern at 10.2 GHz with an azimuth angle of 0°. It can be seen that there are two obvious bulges on both sides of the center of (a) and (b), and there is a "zero depth" phenomenon in the center of each bulge. Fig.13 The center positions of the two beams in (a) are -30° and 45°, and the center positions of the two beams in (b) are -45° and 30°. The simulation results verify the previous design.

[0086] Fig.14 Clearly draw f L =7GHz and f M =Near field scan result at 10.2GHz. Fig.14 (ad) is f L =The test results of the double vortex beam in the transmitted half space at 7 GHz, (eh) is the test result of the double vortex beam in the reflected half space. An obvious zero-depth effect can be observed from the four amplitude distribution diagrams on the left, that is, the energy in the central area is close to zero, and the energy is distributed in a donut shape around the zero point. The phase distribution diagram on the right shows the counterclockwise and clockwise spiral phase distributions, respectively, which proves that the characteristics of the OAM beam are not damaged in the process of complex amplitude superposition and power regulation, and the equal-amplitude double vortex beam radiation in different directions is achieved. According to the spiral phase distribution shown on the right side of the figure, it can be seen that the mode numbers of the four vortex waves are l respectively. 1 =1,l 2 =-1, l 3 =1,l 4 = -1. For the OAM beams in the reflection half-space and the transmission half-space, it can be observed that there are certain differences in their measured phase distributions. This can be attributed to manufacturing and measurement errors. The processing error causes a certain deviation between the beam pointing and the designed beam pointing; the second is the measurement error. Due to the limitations of the measurement site and the instrument, there is a problem that the scanning plane is not precisely perpendicular to the beam pointing during the test. Overall, at the intermediate frequency f M =10.2GHz, the vortex wave effect of the reflecting half-space is better than that of the transmitting half-space. This can be attributed to the fact that the electrical size of the metasurface is larger for the mid-frequency reflection band than for the low-frequency transmission band, and the amplitude and phase distribution characteristics of the vortex beam are also better.

[0087] Secondly, the x-axis dual focus design was performed;

[0088] The present invention is at low frequency f H = The x-axis dual focus function in transmission mode is designed at 15.7 GHz. The complex amplitude distribution of the dual focus can be expressed as:

[0089]

[0090] Formula 2 represents the complex amplitude distribution required to achieve dual focus at any position, where A 1 , A 2 represents the focal depth, that is, the amplitude ratio of the two focal points, (d 1x , d 1y , F 1 ) represents the three-dimensional coordinate position of focus 1. Similarly, (d 2x , d 2y , F 2 ) represents the three-dimensional coordinate position of the second focus. Here, we predetermine two focus positions (80,0,-150) and (-80,0,-150).

[0091] like Fig.15 As shown, according to formula 2, we can get f H = ...

[0092] Fig.16 Given f H = Simulation results of dual-focus focusing at 15.7 GHz. Fig.16 (a) is the simulated electric field amplitude diagram of the xoz surface. Fig.16 (b) The simulated electric field amplitude diagram of the xoy surface at z = -150 mm. As can be seen from Figure (a), there are two obvious energy focus points at a distance of 150 mm from the metasurface, and these two focus points are symmetrically distributed. Figure 5 .16(b) It can be observed that the positions of the two energy focusing points have moved 80 mm to the left and right respectively. In addition, the spatial energy distribution at other positions except the two energy focusing points is very small, which shows that the focusing effect of the dual focus is very good. The results prove that the metasurface has a good focusing effect at f H = The dual focus function is well realized at 15.7GHz.

[0093] The invention is not limited to the above-mentioned specific implementation modes. A person skilled in the art can implement the invention in various other specific implementation modes according to the embodiments and the disclosure of the drawings. Therefore, any design that adopts the design structure and concept of the invention and makes some simple transformations or changes falls within the scope of protection of the invention.

Claims

1. A three-band full-space circular polarization phase-modulated metasurface integrator, characterized in that: The three-band full-space circular polarization amplitude-coherent metasurface integrator is composed of M*M metasurface units of the same size arranged in a plane with equal spacing and periodic extension; The metasurface unit includes, from top to bottom, a first metal layer, a first dielectric plate, a second metal layer, an air layer, a third metal layer, a second dielectric plate and a fourth metal layer, and the period of the metasurface unit is p; The first metal layer and the second metal layer are arranged on the upper and lower surfaces of the first dielectric plate, the third metal layer and the fourth metal layer are arranged on the upper and lower surfaces of the second dielectric plate, and an air layer is between the second metal layer and the third metal layer; The first metal layer is an X-shaped metal structure, which is composed of two crossed metal structure strips, the length of the metal structure strip is L, the width is w, the difference in rotation angle between the two metal structure strips is α2; the rotation angle between the X-shaped metal structure and the x-axis is β2; The second metal layer is a double concentric ring metal gap structure opened on the metal layer of the same size as the metasurface unit, wherein the double concentric ring metal gap structure is a metal layer provided with two concentric metal gap inner rings and a metal gap outer ring, the inner diameter and outer diameter of the metal gap inner ring are R4 and R3, and the inner diameter and outer diameter of the metal gap outer ring are R2 and R1; The third metal layer and the fourth metal layer adopt the same structure, both including substructure 1 and substructure 2; the outer edge of substructure 1 is the same size as the metasurface unit, the inner edge is a circle with a radius of R7, and an outer ring double C-shaped slot resonator is opened on substructure 1; The double C-slot resonator includes an outer ring C-slot resonator and an inner ring C-slot resonator; the outer ring C-slot resonator is two concentric arcs, and the outer and inner diameters are both R 11 and R 10 , and the C-shaped arcs with the same curvature; the inner ring C-shaped slot resonator is composed of two concentric arcs, the outer diameter and inner diameter are R9 and R8, and the C-shaped arcs with the same curvature; the gap between the outer ring C-shaped slot resonator and the inner ring C-shaped slot resonator is at an angle of 90 degrees; the rotation angles of the double C-shaped slot resonators of the third metal layer and the fourth metal are θ1 and θ3 respectively; The substructure 2 adopts an inner ring double C-shaped open metal resonant ring. The double C-shaped open metal resonant ring is composed of two concentric arcs, with an outer diameter and an inner diameter of R6 and R5, and C-shaped arcs with the same curvature. The width of the gap between the two C-shaped arcs is g, and T-shaped branches are arranged on the inner sides of the two C-shaped arcs. The length of the horizontal branch connected to the arc is L2, and the length of the vertical branch perpendicular to it is L1; the rotation angles of the double C-shaped open metal resonant rings of the third metal layer and the fourth metal are θ2 and θ4 respectively.

2. The three-band full-space circular polarization phase-modulated metasurface integrator according to claim 1, characterized in that: The X-shaped metal structure controls the amplitude by controlling the difference α2 of the rotation angles of the crossed metal structure strips. In the range of [60°, 90°], the reflection amplitude gradually decreases from 1 to 0, and the phase remains basically unchanged; The reflection amplitude and phase of the X-shaped metal structure can be independently adjusted, and a reflection phase change of 2β2 can be obtained by changing the x-axis rotation angle β2.

3. The three-band full-space circular polarization phase-modulated metasurface integrator according to claim 1, characterized in that: The dual C-slot resonator controls the amplitude by controlling the difference in rotation angle α1, where α1=θ3-θ1 is within the range of [0°, 60°], and the reflection amplitude gradually decreases from 0.9 to 0, while the phase remains substantially unchanged; The double C-slot resonator obtains a reflection phase change of 2β1 by changing the overall rotation angle β1, β1=(θ3+θ1) / 2, and the amplitude remains basically unchanged.

4. The three-band full-space circular polarization phase-modulated metasurface integrator according to claim 1, characterized in that: The double C-shaped open metal resonant ring controls the amplitude by controlling the difference α3 between the upper and lower layer rotation angles. α3=θ4-θ2 is within the range of [0°, 60°], and the reflection amplitude gradually decreases from 0.83 to 0, while the phase remains basically unchanged. The double C-shaped open metal resonant ring obtains a reflection phase change of 2β3 by changing the overall rotation angle β3, β3=(θ4+θ2) / 2, and the amplitude remains basically unchanged.

5. The three-band full-space circular polarization phase-modulated metasurface integrator according to claim 1, characterized in that: The structural parameters optimized by the super surface unit are as follows: The metasurface unit period p=11 mm, the first dielectric plate thickness h1=3 mm, the second dielectric plate thickness h2=8 mm, and the air layer thickness h3=2.5 mm; The first metal layer, the second metal layer, the third metal layer and the fourth metal layer are made of copper with a thickness of 0.036 mm; The length of the metal structure strip is L = 6 mm, and the width is w = 0.3 mm; The inner diameter of the metal gap inner ring is R4=2.28mm, the outer diameter of the metal gap inner ring is R3=3.08mm, the inner diameter of the metal gap outer ring is R2=4.7mm, and the outer diameter of the metal gap outer ring is R1=12mm; Outer ring C-slot resonator outer diameter R 11 =5.4mm, the inner diameter of the outer ring C-slot resonator R 10 =5.2mm, the outer diameter of the inner ring C-shaped slot resonator R9 = 5mm, the inner diameter of the inner ring C-shaped slot resonator R8 = 4.8mm, and the inner edge of the double C-shaped slot resonator has a radius of R7 = 4.1mm; The outer diameter of the double C-shaped open metal resonant ring is R6=2.2mm, the inner diameter of the double C-shaped open metal resonant ring is R5=2.5mm, the horizontal branch length is L2=1mm, the vertical branch length is L1=1.6mm, and the gap width g between the C-shaped arcs is 1.1mm.

6. A method for designing a three-band full-space circularly polarized phase-modulated metasurface integrator as claimed in any one of claims 1 to 5, characterized in that: The method for designing a three-band full-space circular polarization phase-modulated metasurface integrator comprises the following steps: Step 1: Use a dual-bandpass frequency selective surface structure to replace the metal backplane to construct a transflective isolation mode; the dual-bandpass frequency selective surface structure is a double concentric ring metal gap structure, which is arranged on the lower surface of the first dielectric plate. M = Total reflection at 10.2 GHz, at f L =7GHz and f H =High transmission at 15.7 GHz; Step 2: Introduce an X-shaped metal structure into the metasurface to construct an intermediate frequency f M The X-shaped metal structure is arranged on the upper surface of the first dielectric plate, and the co-polarization reflection band of the unit is made to overlap with the reflection band of the dual-bandpass frequency selective surface structure through parameter scanning; Step 3: introduce double C-shaped slot resonators and double C-shaped open metal resonant rings into the metasurface to construct a low-frequency f L =7GHz and high frequency f H = A dual-band high-efficiency transmission mode and amplitude and phase control at 15.7 GHz; the dual C-slot resonator and the dual C-open metal resonant ring are respectively arranged on the upper and lower surfaces of the second dielectric plate, and the two cross-polarization transmission bands of the unit are overlapped with the two transmission bands of the dual-band pass frequency selective surface structure through parameter scanning; Step 4: synthesize the final four-layer structure with both transmission and reflection, and evaluate the isolation between the transmission and reflection frequency bands; cascade to form a final four-layer unit structure with both transmission and reflection modes, so that the final metasurface can realize the joint modulation of the amplitude and phase of the transmission wave and the reflection wave in three frequency bands; Step 5: Determine the topological structure of the metasurface based on the calculated three amplitude and phase distributions to realize a three-function integrated metasurface device.

7. The design method of the three-band full-space circular polarization phase-modulated metasurface integrator according to claim 6 is characterized in that: The X-shaped metal structure controls the amplitude by controlling the difference α2 of the rotation angles of the crossed metal structure strips. In the range of [60°, 90°], the reflection amplitude gradually decreases from 1 to 0, and the phase remains basically unchanged; The reflection amplitude and phase of the X-shaped metal structure can be independently adjusted, and a reflection phase change of 2β2 can be obtained by changing the x-axis rotation angle β2.

8. The design method of the three-band full-space circular polarization phase-modulated metasurface integrator according to claim 6 is characterized in that: The dual C-slot resonator controls the amplitude by controlling the difference in rotation angle α1, where α1=θ3-θ1 is within the range of [0°, 60°], and the reflection amplitude gradually decreases from 0.9 to 0, while the phase remains substantially unchanged; The double C-slot resonator obtains a reflection phase change of 2β1 by changing the overall rotation angle β1, β1=(θ3+θ1) / 2, and the amplitude remains basically unchanged.

9. The design method of the three-band full-space circular polarization phase-modulated metasurface integrator according to claim 6 is characterized in that: The double C-shaped open metal resonant ring controls the amplitude by controlling the difference α3 between the upper and lower layer rotation angles. α3=θ4-θ2 is within the range of [0°, 60°], and the reflection amplitude gradually decreases from 0.83 to 0, while the phase remains basically unchanged. The double C-shaped open metal resonant ring obtains a reflection phase change of 2β3 by changing the overall rotation angle β3, β3=(θ4+θ2) / 2, and the amplitude remains basically unchanged.

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