A broadband polarization conversion unit, converter and wireless communication system

Abstract

This application discloses a broadband polarization conversion unit, a converter, and a wireless communication system. The broadband polarization conversion unit includes a metal substrate, an intermediate dielectric plate, and a metasurface structure. The intermediate dielectric plate is attached to one side of the metal substrate. The metasurface structure includes a graphene strip and two metal strips. The graphene strip is attached to the side of the intermediate dielectric plate opposite to the metal substrate and is inclined within its plane. The two metal strips are attached to the side of the intermediate dielectric plate opposite to the metal substrate and are located on opposite sides of the graphene strip along its width direction. The metal strips are in contact with the graphene strip, and the Fermi level of the graphene strip is adjustable. By adjusting the Fermi level of the graphene strip, the polarization conversion can be freely adjusted within three frequency bands from 0.87THz to 1.37THz, with a polarization conversion rate of over 95%. When the polarization conversion rate is over 90%, a wider bandwidth polarization conversion can be achieved in the 636GHz~736GHz and 0.82THz~1.38THz frequency bands.

Description

Technical Field

[0001] This application relates to the field of polarization converter technology, and in particular to a broadband polarization conversion unit, converter and wireless communication system. Background Technology

[0002] Polarization is a crucial characteristic parameter in the transmission, propagation, and reception of electromagnetic waves. Electromagnetic wave polarization refers to the phenomenon where the magnitude and direction of the electric field intensity vector of the composite wave changes over time at any given point in space, and is vividly described by the trajectory of the endpoints of the electric field intensity vector over time. Polarization converters have wide applications in numerous engineering fields, such as antennas, satellite navigation, communication, and radar detection. Effectively controlling the polarization mode and state of electromagnetic waves is of paramount importance. Metasurfaces are ultrathin two-dimensional metamaterial layers with electromagnetic response characteristics not found in many traditional materials. For example, metasurfaces have been shown to produce anomalous reflections, superabsorption, or guide and modulate surface waves to obtain desired radiation characteristics. Metasurfaces exhibit widespread anisotropy and inhomogeneity, which can be conveniently used to control the polarization direction.

[0003] In related technologies, a transducer with a single-layer metal structure has achieved orthogonal polarization conversion of transmission, with a polarization conversion rate of 90% in the range of 0.91~1.45THz. Alternatively, a reflective broadband polarization converter based on a fractal structure and using multi-frequency point superposition has been designed, with a polarization conversion rate of over 90% in the range of 8~24GHz.

[0004] However, the aforementioned metasurface polarization converters have limited functionality and fixed bandwidth, making dynamic adjustment impossible. Summary of the Invention

[0005] Based on this, this application provides a broadband polarization conversion unit, converter, and wireless communication system to solve the problems of limited functionality, fixed bandwidth, and inability to dynamically adjust the bandwidth of metasurface polarization converters in related technologies.

[0006] In a first aspect, embodiments of this application provide a broadband polarization conversion unit, comprising:

[0007] metal substrate;

[0008] An intermediate dielectric plate is attached to one side of the metal substrate;

[0009] A metasurface structure comprising a graphene strip and two metal strips, wherein the graphene strip is attached to the side of the intermediate dielectric plate opposite to the metal substrate and is inclined in its plane, and the two metal strips are attached to the side of the intermediate dielectric plate opposite to the metal substrate and are respectively located on both sides of the graphene strip along its width direction, the metal strips being bonded to the graphene strip, wherein the Fermi level of the graphene strip is adjustable.

[0010] In some embodiments, the angle between the graphene strip and the edge of the intermediate dielectric plate is 45°.

[0011] In some embodiments, the two ends of the graphene strip extend to the diagonal of the intermediate dielectric plate.

[0012] In some embodiments, the two metal strips are arranged symmetrically along the centerline of the graphene strip.

[0013] In some embodiments, the period of the broadband polarization conversion unit is p, where p satisfies: p = 120 μm;

[0014] The width of the graphene strip is W1, where W1 = 10 μm, and the thickness of the graphene strip is h1, where h1 = 0.01 μm.

[0015] The length of the metal strip is L1, and L1 satisfies: L1=100μm; the width of the metal strip is W2, and W2 satisfies: W2=10μm; the thickness of the metal strip is h2, and h2 satisfies: h2=0.2μm.

[0016] In some embodiments, the thickness of the metal substrate is h3, wherein h3 satisfies: h3 = 0.2 μm;

[0017] The thickness of the intermediate medium plate is h4, and h4 satisfies: h4=35μm.

[0018] In some embodiments, the metal substrate and the metal strip are made of gold, and the intermediate dielectric plate is made of silicon dioxide.

[0019] In some embodiments, the broadband polarization conversion unit further includes a control device, which includes a bias voltage, one end of which is electrically connected to the metal strip and the other end of which is electrically connected to the metal substrate.

[0020] Secondly, this application also provides a broadband polarization converter, which includes a plurality of broadband polarization conversion units as described in the first aspect, and the plurality of broadband polarization conversion units are arranged in a periodic array in a plane.

[0021] Thirdly, this application also provides a wireless communication system, which includes the broadband polarization converter described in the second aspect.

[0022] This application has at least the following beneficial effects:

[0023] A metal substrate, an intermediate dielectric plate, and a metasurface structure are stacked vertically from bottom to top. The graphene strips are angled, meaning they form an angle with the edge of the intermediate dielectric plate. Two metal strips are attached to either side of the graphene strip along its width. The metal substrate, intermediate dielectric plate, and metasurface structure work together to achieve polarization conversion and phase modulation of electromagnetic waves. The Fermi level of the graphene strip can be adjusted, allowing for a continuous transition of the graphene strip's properties from metallic to semiconducting. When the graphene strip is metallic, it and the two metal strips together form a single structural device. When the graphene strip is semiconducting, only the two metal strips function, allowing the polarization conversion to be freely adjusted within three frequency bands from 0.87 THz to 1.37 THz, with a polarization conversion rate exceeding 95%. When the polarization conversion rate exceeds 90%, wider bandwidth polarization conversion can be achieved in the 636 GHz to 736 GHz and 0.82 THz to 1.38 THz frequency bands. Simultaneously, by linearly altering the Fermi level of graphene, modulation of the phase difference from -135° to 90° was achieved within the 0.7THz-1.3THz frequency band. At a phase difference of -90°, it can also be used as a broadband half-wave plate in optics. Furthermore, simulations verify that the device exhibits strong robustness to incident terahertz waves at varying incident angles; when the incident angle increases to 40°, the polarization conversion efficiency remains above 90% over a wide frequency range. This solves the problem of converters having limited functionality, fixed bandwidth, and the inability to achieve dynamic adjustment. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the structure of the broadband polarization conversion unit in some embodiments of this application;

[0026] Figure 2 This is a top view of a broadband polarization conversion unit in some embodiments of this application;

[0027] Figure 3 This is a side view of a broadband polarization conversion unit in some embodiments of this application;

[0028] Figure 4 The graphs show the relationship between reflectivity and frequency for cross-polarization (Rxy) and co-polarization (Ryy) of graphene strips at Fermi levels of 0.1 eV and 0.6 eV in some embodiments of this application. The dashed line represents Ryy and the solid line represents Rxy. The graphs also show the cross-polarization phase difference at different Fermi levels of graphene.

[0029] Figure 5 The graphs show the polarization conversion efficiency of graphene strips at different Fermi levels in some embodiments of this application.

[0030] Figure 6 This is a graph showing the relationship between polarization conversion rate and frequency at different oblique incidence angles in some embodiments of this application;

[0031] Figure 7 The surface current density distribution of graphene strips at a Fermi level of 0.1 eV is shown in some embodiments of this application.

[0032] Figure 8 This is a surface current density distribution diagram of graphene strips at a Fermi level of 0.6 eV in some embodiments of this application.

[0033] Explanation of reference numerals in the attached figures:

[0034] 100 - Broadband polarization conversion unit, 10 - Metal substrate, 20 - Intermediate dielectric plate, 30 - Metasurface structure, 31 - Graphene strip, 32 - Metal strip. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar components or components having the same or similar functions throughout. The described embodiments are some, but not all, of the embodiments of this application. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application. The embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0036] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, an indirect connection through an intermediate medium, or the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0037] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0038] The terms “first,” “second,” and “third” (if any) in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0039] Furthermore, the terms “comprising” and “having”, and any variations thereof, are intended to cover non-exclusive inclusion, such that a process, method, system, product, or display that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or display.

[0040] First, let me explain the terms used in this application:

[0041] Terahertz (THz) refers to electromagnetic waves with frequencies ranging from 100 GHz to 10 THz. Its wavelength is much shorter than that of typical microwaves and millimeter waves, and it possesses characteristics such as low energy, high penetration, wide bandwidth, and transient response. These features have led to its widespread application in various fields, including terahertz medical imaging, atmospheric environmental monitoring, and terahertz radar. Particularly in the field of communications, terahertz antennas, benefiting from the advantages of terahertz waves, enable wireless devices to carry more signals, which is of great significance for the upcoming 6G communication systems.

[0042] Metasurfaces are ultrathin two-dimensional metamaterial layers that possess electromagnetic response properties not found in many traditional materials. For example, metasurfaces have been shown to generate anomalous reflections, superabsorptions, or to guide and modulate surface waves to obtain desired radiation characteristics. Metasurfaces exhibit widespread anisotropy and inhomogeneity, which can be conveniently used to control polarization directions.

[0043] Reconfigurable metasurfaces are novel composite materials developed within the theoretical framework of traditional metasurfaces by introducing reconfigurable materials. Reconfigurability refers to the ability of a material to change its physical or chemical properties under external stimulation, and then revert to its original properties once the external stimulation ceases. Using reconfigurable metasurfaces, tunable or functionally switchable metasurface control devices can be realized, with their functions controlled by external stimuli, opening a new direction for the dynamic manipulation of electromagnetic waves. Currently, metasurfaces are combined with graphene, phase change materials, and microelectromechanical structures (MEMS) to achieve optical, electrical, heating, and electromechanical control of these materials or structures, enabling the switching or dynamic adjustment of certain functions. While this increases fabrication complexity, it greatly enhances the diversity of devices.

[0044] Polarization is a crucial characteristic parameter in the transmission, propagation, and reception of electromagnetic waves. Electromagnetic wave polarization refers to the phenomenon where the magnitude and direction of the electric field intensity vector of the composite wave changes over time at any given point in space, and is vividly described by the trajectory of the endpoints of the electric field intensity vector over time. Polarization converters have wide applications in numerous engineering fields, such as antennas, satellite navigation, communication, and radar detection. Therefore, effectively controlling the polarization mode and state of electromagnetic waves is of paramount importance.

[0045] In related technologies, a transducer with a single-layer metal structure has achieved orthogonal polarization conversion of transmission, with a polarization conversion rate of 90% in the range of 0.91~1.45THz. Alternatively, a reflective broadband polarization converter based on a fractal structure and using multi-frequency point superposition has been designed, with a polarization conversion rate of over 90% in the range of 8~24GHz.

[0046] The applicant found that the aforementioned metasurface polarization converter has a single function, fixed bandwidth, and cannot be dynamically adjusted.

[0047] In view of this, the applicant has designed a broadband polarization conversion unit, a converter, and a wireless communication system. The broadband polarization conversion unit, converter, and wireless communication system provided in the embodiments of this application are described in detail below with reference to the accompanying drawings.

[0048] like Figures 1 to 3As shown, this application embodiment provides a broadband polarization conversion unit 100, which includes a metal substrate 10, an intermediate dielectric plate 20, and a metasurface structure 30. The intermediate dielectric plate 20 is attached to one side of the metal substrate 10. The metasurface structure 30 includes a graphene strip 31 and two metal strips 32. The graphene strip 31 is attached to the side of the intermediate dielectric plate 20 away from the metal substrate 10, and the graphene strip 31 is inclined in its plane. The two metal strips 32 are attached to the side of the intermediate dielectric plate 20 away from the metal substrate 10 and are respectively located on both sides of the graphene strip 31 along its width direction. The metal strips 32 are bonded to the graphene strip 31. The Fermi level of the graphene strip 31 is adjustable.

[0049] A metal substrate 10, an intermediate dielectric plate 20, and a metasurface structure 30 are stacked vertically from bottom to top. Graphene strips 31 are inclined, meaning they form an angle with the edge of the intermediate dielectric plate 20. Two metal strips 32 are attached to both sides of the graphene strip 31 along its width. The metal substrate 10, intermediate dielectric plate 20, and metasurface structure 30 work together to achieve polarization conversion and phase modulation of electromagnetic waves. The Fermi level of the graphene strip 31 can be adjusted, thus achieving a continuous transition of the graphene strip 31's properties from metallic to semiconducting. When the graphene strip 31 is metallic, it and the two metal strips 32 together constitute a single structural device. When the graphene strip 31 is semiconducting, only the two metal strips 32 function, allowing the polarization conversion to be freely adjusted within three frequency bands from 0.87 THz to 1.37 THz, with a polarization conversion rate exceeding 95%. When the polarization conversion efficiency exceeds 90%, a wider bandwidth polarization conversion can be achieved in the 636GHz~736GHz and 0.82THz~1.38THz frequency bands. Simultaneously, by linearly altering the Fermi level of graphene, modulation with a phase difference from -135° to 90° is achieved in the 0.7THz~1.3THz frequency band. At a phase difference of -90°, it can also be used as a broadband half-wave plate in optics. Furthermore, simulations verify that the device exhibits strong robustness to incident terahertz waves at varying incident angles; when the incident angle increases to 40°, the polarization conversion efficiency remains above 90% over a wide frequency range. This solves the problem of converters having limited functionality, fixed bandwidth, and the inability to achieve dynamic adjustment.

[0050] like Figures 1 to 2 As shown, in some embodiments, the angle between the graphene strip 31 and the edge of the intermediate dielectric plate 20 is 45°.

[0051] The graphene strip 31 is arranged in a long strip shape, with the angle between the edge of the graphene strip 31 and the edge of the intermediate dielectric plate 20 being 45°. This means the graphene strip 31 is attached to the intermediate dielectric plate 20 at a 45° tilt angle. This design ensures that the x-polarization component of the incident electromagnetic wave is effectively converted into the y-polarization component during resonance, thus achieving cross-polarization conversion. Simultaneously, it reduces the dependence on the incident wave direction, thereby maintaining more stable performance under complex incident angle scenarios.

[0052] like Figures 1 to 2 As shown, in some embodiments, the two ends of the graphene strip 31 extend to the diagonal of the intermediate dielectric plate 20.

[0053] The intermediate dielectric plate 20 is square, with a 45° angle between its diagonal and its side. The center line of the graphene strip 31 coincides with the diagonal of the intermediate dielectric plate 20. Both ends of the graphene strip 31 extend to the diagonal of the intermediate dielectric plate 20, and the ends of the graphene strip 31 are adapted to the diagonal of the intermediate dielectric plate 20 at right angles. In other words, the graphene strip 31 is roughly hexagonal. This arrangement allows both ends of the graphene strip 31 to extend to the edge region of the broadband polarization conversion unit 100, facilitating the connection between the control device and the graphene strip 31.

[0054] like Figures 1 to 2 As shown, in some embodiments, the two metal strips 32 are symmetrically arranged along the center line of the graphene strip 31.

[0055] The two metal strips 32 are identical in length, width, and thickness, and are symmetrical along the midline of the graphene strip 31. This design allows for effective bandwidth widening through synergistic coupling of multiple resonant modes. The symmetrical metal strips 32 and graphene strip 31 can excite resonant characteristics at different frequency bands, and the symmetrical structure ensures smooth fusion of the two resonant peaks, forming a continuous broadband response. It also enhances the device's angular stability and fabrication robustness. For incident electromagnetic waves at different angles (especially large-angle incident scenarios from 0° to 45°), the symmetrical structure maintains a stable electromagnetic response, ensuring that polarization conversion efficiency and bandwidth do not significantly decrease, thus improving the device's adaptability to practical applications.

[0056] like Figures 2 to 3 As shown, in some embodiments, the period of the broadband polarization conversion unit 100 is p, where p = 120 μm; the width of the graphene strip 31 is W1, where W1 = 10 μm; the thickness of the graphene strip 31 is h1, where h1 = 0.01 μm; the length of the metal strip 32 is L1, where L1 = 100 μm; the width of the metal strip 32 is W2, where W2 = 10 μm; and the thickness of the metal strip 32 is h2, where h2 = 0.2 μm.

[0057] like Figure 3 As shown, in some embodiments, the thickness of the metal substrate 10 is h3, where h3 = 0.2 μm; the thickness of the intermediate dielectric plate 20 is h4, where h4 = 35 μm.

[0058] In some embodiments, the metal substrate 10 and the metal strip 32 are made of gold, and the intermediate dielectric plate 20 is made of silicon dioxide.

[0059] The high conductivity of gold ensures that the metal substrate 10 and metal strip 32 form an efficient resonant structure, while the stable dielectric properties of silicon dioxide optimize the propagation path of electromagnetic waves in the intermediate dielectric plate 20. The high conductivity of gold and the stable dielectric properties of silicon dioxide optimize the performance stability of the resonant structure. Simultaneously, energy loss during electromagnetic wave propagation is reduced, thereby maintaining a higher polarization conversion rate over a wide frequency range.

[0060] In some embodiments, the broadband polarization conversion unit 100 further includes a control device, which includes a bias voltage. One end of the bias voltage is electrically connected to the metal strip 32, and the other end of the bias voltage is electrically connected to the metal substrate 10.

[0061] The bias voltage is electrically connected to the metal strip 32 and the metal substrate 10, and the metal strip 32 abuts against the graphene strip 31, thereby achieving dynamic adjustment of the Fermi level of the graphene. This maintains efficient polarization conversion and phase modulation performance over a wide bandwidth.

[0062] To verify the performance of the above-mentioned device, the metal substrate 10 and the metal strip 32 are both made of gold, the intermediate dielectric plate 20 is made of silicon dioxide, the period of the broadband polarization conversion unit 100 is p=120μm, the width of the graphene strip 31 is W1=10μm, the thickness of the graphene strip 31 is h1=0.01μm (which can be regarded as a material with no thickness during simulation), the thickness of the metal strip 32 is h2=0.2μm, the width of the metal strip 32 is W2=10μm, the length of the metal strip 32 is L1=100μm, the thickness of the metal substrate 10 is h3=0.2μm, and the thickness of the intermediate dielectric plate 20 is h4=35μm. The electromagnetic simulation software CST is used to model it, and the polarization conversion performance of the proposed metasurface is numerically analyzed using a frequency domain solver.

[0063] The incident wave is set as a perpendicularly incident x-polarized terahertz wave. Unit cell boundary conditions are set in the x and y directions, and open add space boundary conditions are set in the z direction. An adaptive tetrahedral mesh is used to accelerate convergence. In the material parameter simulation settings, the relative permittivity ε of the silicon dioxide film is 3.9. The conductivity of the gold film is set to σ = 4.56 × 10⁷ S / m. The graphene simulation uses the built-in modeling method of CST: temperature is set to 293 K, and relaxation time is 1 ps.

[0064] Please refer to Figure 4 (a) Figure 1 shows the relationship between reflectivity and frequency for cross-polarization (Rxy) and co-polarization (Ryy) of the graphene metasurface at Fermi levels of 0.1 eV and 0.6 eV. The dashed line represents Ryy, and the solid line represents Rxy. It can be seen that within a bandwidth of 0.64 THz to 1.38 THz, the average reflectivity in the co-polarization direction is less than 0.2, while the reflectivity in the cross-polarization direction is above 0.8.

[0065] Please refer to Figure 4 (b) As shown in the attached figure, the phase difference (∆Φ=Φyy-Φxy) between x-polarization and y-polarization in the frequency range of 0.7THz to 1.3THz exhibits a dynamic change from -135° to 90° as the graphene Fermi level changes linearly. In particular, by dynamically adjusting the graphene Fermi level, when the phase difference is -90° in the frequency range of 0.76THz to 1THz, this device can also be used as a broadband half-wave plate in the optical field.

[0066] To further illustrate the polarization conversion characteristics of this metasurface, polarization conversion efficiency (PCR) was introduced to characterize its polarization conversion performance:

[0067]

[0068] The polarization conversion efficiency of graphene at different Fermi levels was calculated from the simulation results, as follows: Figure 5 As shown.

[0069] Please refer to Figure 5 (a) When the Fermi level of graphene is 0.1 eV, the metasurface achieves cross-polarization conversion in the frequency range of 1.03 THz to 1.31 THz with a PCR > 95%. When the Fermi level of graphene is adjusted to 0.6 eV, the metasurface achieves cross-polarization conversion in two frequency bands: 0.87 THz to 1.07 THz and 1.26 THz to 1.37 THz with a PCR > 95%. In other words, by simply adjusting the Fermi level of graphene, cross-polarization can be achieved in the frequency band of 0.87 THz to 1.37 THz with a polarization conversion rate of over 95%.

[0070] Please refer to Figure 5 (b) When PCR>90% is used as the performance reference standard, a wider polarization conversion can be achieved in the 636GHz~736GHz and 0.82THz~1.38THz frequency bands, which not only widens the frequency band, but also moves closer to the low frequency 636GHz~736GHz.

[0071] In real life, the incident direction of electromagnetic waves is arbitrary; therefore, studying the polarization conversion characteristics of metasurfaces under different incident angles is of great significance. Please refer to... Figure 6 , Figure 6 The relationship between PCR and frequency under different incident angles is shown. Within the frequency range of 0.8 THz to 1.40 THz, when the incident angle varies from 0° to 40°, the PCR rate remains above 90%. However, as the incident angle increases, the bandwidth of polarization conversion narrows, and the polarization conversion rate decreases significantly. The main reason for this phenomenon is that as the incident angle increases, the magnetic and electric fields perpendicular to the incident direction are decomposed and reduced, and the resonance between the upper and lower metal layers gradually weakens.

[0072] Using graphene Fermi levels of 0.1 eV and 0.6 eV as examples, the physical mechanism of the high-bandwidth polarization conversion of the metasurface in this application is explained. Please refer to... Figure 7 , Figure 7 The image shows the surface current density distribution of the graphene pattern at Ef = 0.1 eV. Figure 4 Analysis at frequencies of 0.67 THz and 1.22 THz revealed that the common-polarization reflection coefficient was minimized at these two frequencies, indicating resonance. Figure 7 As shown in (a) and 7(b), at the resonant point of 0.67 THz, the surface current and the current in the bottom metal plate are in opposite directions, forming a current loop in the dielectric layer, indicating magnetic resonance. At the resonant point of 1.22 THz, as... Figure 7 As shown in (c) and 7(d), the surface current and the bottom metal plate current are in the same direction, forming an equivalent electric resonance.

[0073] Similarly, please refer to Figure 8 , Figure 8 The image shows the surface current distribution of the graphene pattern at Ef = 0.6 eV, based on... Figure 4 Select Figure 4 The lowest polarization reflectivity points of 0.98THz and 1.34THz are the resonant points. The incident electromagnetic wave generates electromagnetic resonance with the metasurface. The superposition of these electromagnetic resonances allows the polarization converter to operate in a wider frequency band.

[0074] Based on the same inventive concept, this application also provides a broadband polarization converter, which includes a plurality of the above-mentioned broadband polarization conversion units, which are arranged in a periodic array in a plane.

[0075] Since the broadband polarization converter includes the aforementioned broadband polarization conversion unit, it naturally possesses all the beneficial effects of the broadband polarization conversion unit, which will not be elaborated upon here.

[0076] Based on the same inventive concept, embodiments of this application also provide a wireless communication system, which includes the aforementioned broadband polarization converter.

[0077] Since the wireless communication system includes the aforementioned broadband polarization converter, it naturally possesses all the beneficial effects of a broadband polarization converter, which will not be elaborated upon here.

[0078] It should be noted that wireless communication systems can include base station antennas, car radars, etc.

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A broadband polarization conversion unit, characterized in that, include: metal substrate (10); Intermediate dielectric plate (20), the intermediate dielectric plate (20) is attached to one side of the metal substrate (10); A metasurface structure (30) includes a graphene strip (31) and two metal strips (32). The graphene strip (31) is attached to the side of the intermediate dielectric plate (20) away from the metal substrate (10) and is inclined in its plane. The two metal strips (32) are attached to the side of the intermediate dielectric plate (20) away from the metal substrate (10) and are respectively located on both sides of the graphene strip (31) along its width direction. The metal strips (32) are attached to the graphene strip (31). The Fermi level of the graphene strip (31) is adjustable.

2. The broadband polarization conversion unit according to claim 1, characterized in that, The angle between the graphene strip (31) and the edge of the intermediate medium plate (20) is 45°.

3. The broadband polarization conversion unit according to claim 2, characterized in that, The two ends of the graphene strip (31) extend to the diagonal of the intermediate medium plate (20).

4. The broadband polarization conversion unit according to claim 3, characterized in that, The two metal strips (32) are symmetrically arranged along the center line of the graphene strip (31).

5. The broadband polarization conversion unit according to claim 3, characterized in that, The period of the broadband polarization conversion unit (100) is p, and p satisfies: p = 120 μm; The width of the graphene strip (31) is W1, where W1 = 10 μm, and the thickness of the graphene strip (31) is h1, where h1 = 0.01 μm. The length of the metal strip (32) is L1, and L1 satisfies: L1=100μm. The width of the metal strip (32) is W2, and W2 satisfies: W2=10μm. The thickness of the metal strip (32) is h2, and h2 satisfies: h2=0.2μm.

6. The broadband polarization conversion unit according to claim 1, characterized in that, The thickness of the metal substrate (10) is h3, and h3 satisfies: h3 = 0.2 μm; The thickness of the intermediate medium plate (20) is h4, and h4 satisfies: h4=35μm.

7. The broadband polarization conversion unit according to claim 1, characterized in that, The metal substrate (10) and the metal strip (32) are made of gold, and the intermediate dielectric plate (20) is made of silicon dioxide.

8. The broadband polarization conversion unit according to claim 1, characterized in that, The broadband polarization conversion unit (100) further includes a control device, which includes a bias voltage. One end of the bias voltage is electrically connected to the metal strip (32), and the other end of the bias voltage is electrically connected to the metal substrate (10).

9. A broadband polarization converter, characterized in that, It includes a plurality of broadband polarization conversion units (100) as described in any one of claims 1-8, wherein the plurality of broadband polarization conversion units (100) are arranged in a periodic array in a plane.

10. A wireless communication system, characterized in that, Includes the broadband polarization converter as described in claim 9.

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