Broadband Huygens metasurface and dual-polarization mode multiplexing OAM wave beam generation and regulation method thereof

Abstract

The invention discloses a broadband Huygens metasurface and a dual-polarization modal multiplexing orbital angular momentum (OAM) wave beam generation and regulation method thereof, the broadband Huygens metasurface comprises m * n Huygens metasurface basic units, the phase compensation of the basic units at different positions is meticulously designed, the OAM wave beam can be generated in the frequency band range of 8.5 GHz to 11.5 GHz, and the deflection angle is controlled. According to the invention, the basic unit adopts the complementary cross-shaped metal strips with different lengths to form an antisymmetric structure to excite Huygens resonance, and has all-phase coverage and high transmission efficiency. According to the Huygens metasurface basic unit, a magnetic dipole is removed from a physical structure, so that the structure is more compact. The metasurface also has the characteristic of independent polarization, can generate a dual-polarized OAM wave beam, can directionally deflect the generated wave beam, and has the advantages of wide band, low profile, independent polarization and mode multiplexing.

Description

Technical Field

[0002] This invention relates to the field of novel artificial electromagnetic materials and OAM beam generation and control, and in particular to a broadband Huygens metasurface and its dual-polarization mode multiplexing OAM beam generation and control method. Background Technology

[0004] With the rapid development of modern wireless communication technology, the scarcity of available spectrum resources is becoming increasingly prominent. Therefore, improving channel capacity and spectrum utilization has become a critical challenge that urgently needs to be addressed. OAM vortex electromagnetic waves, with their unique helical phase factor and mutual orthogonality between different modes, provide a new degree of freedom for information modulation. Metasurfaces, as two-dimensional artificial electromagnetic structures, offer advantages such as high efficiency, low profile, and flexible control due to their ability to manipulate electromagnetic waves using subwavelength structures. Huygens metasurfaces, by balancing the resonance of electric and magnetic dipoles through impedance matching, achieve low profile, full phase coverage, and high transmittance, providing a novel method for the generation and modulation of OAM beams. This invention proposes a broadband Huygens metasurface and its method for generating and modulating dual-polarized mode-multiplexed OAM beams, capable of stably generating dual-polarized mode-multiplexed OAM beams with directional deflection capabilities. This invention offers advantages such as broadband bandwidth, low profile, polarization independence, and mode multiplexing. Summary of the Invention

[0006] Purpose of the invention: The purpose of this invention is to provide a broadband Huygens metasurface and its dual-polarization mode multiplexing OAM beam generation and control method, which can be used in the field of multi-target wireless communication in the future.

[0007] Technical solution: The Huygens metasurface of the present invention comprises m×n Huygens metasurface basic units. The basic unit comprises 3 layers, from top to bottom: a top cross-shaped metal strip layer, a middle dielectric substrate layer, and a bottom complementary cross-shaped metal strip layer.

[0008] Furthermore, the dielectric substrate layer of the basic unit is made of polytetrafluoroethylene fiberglass cloth dielectric substrate with copper foil on both sides, with a dielectric constant of 2.65 and a loss tangent of 0.001.

[0009] Furthermore, the top and bottom layers of the individual basic unit have metal strips of the same length and width, while the lengths of the basic unit metal strips at different locations on the metasurface are different;

[0010] Furthermore, when the lengths of the two axes of the top and bottom cross-shaped metal strips change respectively, the basic unit of the metasurface controls electromagnetic waves in different polarization directions, achieving 360° transmission phase modulation in the 8.5GHz-11.5GHz frequency band.

[0011] Furthermore, the basic units at different locations on the metasurface have different phases, when the phase distribution satisfies When the metasurface can generate OAM beams over a wide bandwidth, l is the OAM mode, λ is the incident electromagnetic wavelength, and F is the distance between the feed and the metasurface.

[0012] Furthermore, when the phases of the two polarization directions of the basic units at different positions of the metasurface satisfy the phase distribution of claim 5, the metasurface can simultaneously generate broadband dual-polarized OAM beams with modes lx and ly.

[0013] Furthermore, in addition to simultaneously generating dual-polarized OAM beams with modes lx and ly, the metasurface further superimposes different phase gradient distributions in the two polarization directions. and The metasurface can realize OAM beam scanning with broadband dual-polarization mode multiplexing in the xoz and yoz polarization planes respectively.

[0014] The broadband Huygens metasurface and its dual-polarization mode-multiplexed OAM beam generation and control method of the present invention have the following advantages:

[0015] (1) The broadband Huygens metasurface and its dual-polarization mode-multiplexed OAM beam generation and control method of the present invention exhibit full phase coverage, high transmission efficiency and polarization independence in the 8.5GHz-11.5GHz frequency band, and can stably generate dual-polarization mode-multiplexed OAM beams with directional deflection capability. The invention has the advantages of broadband, low profile, polarization independence and mode multiplexing.

[0016] (2) The broadband Huygens metasurface and its dual-polarization mode multiplexing OAM beam generation and control method of the present invention have good application potential in multi-target wireless communication systems and radar imaging technology. Attached Figure Description

[0018] Figure 1 This invention relates to a broadband Huygens metasurface and its dual-polarization mode multiplexing OAM beam generation and control method as described in the embodiments of the present invention.

[0019] Figure 2 This is a schematic diagram of the Huygens metasurface unit structure described in an embodiment of the present invention;

[0020] Figure 3 This is the amplitude phase diagram corresponding to the change in the length of the Huygens metasurface unit metal strip in the embodiments of the present invention;

[0021] Figure 4This is a simulation diagram of the Huygens metasurface generating OAM beams with different polarizations in two modes, lx and ly, according to an embodiment of the present invention; under x-polarization: (a) 3-bit discrete phase coding distribution; (b) normalized electric field amplitude distribution of the lx-mode OAM beam; (c) normalized electric field amplitude distribution of the ly-mode OAM beam; under y-polarization: (d) 3-bit discrete phase coding distribution; (e) normalized electric field amplitude distribution of the lx-mode OAM beam; (f) normalized electric field amplitude distribution of the ly-mode OAM beam;

[0022] Figure 5 The following are far-field simulation diagrams of OAM beams generated by the Huygens metasurface with different deflection angles in the embodiments of the present invention; Scenario 1 (a) x-polarization, lx mode: (−45°, 0°) (b) x-polarization, OAM beam of 8.5GHz-11.5GHz; (c) y-polarization, ly mode: (30°, 0°) (d) y-polarization, OAM beam of 8.5GHz-11.5GHz; Scenario 2 (e) x-polarization, lx mode: (−30°, 90°) (f) x-polarization, OAM beam of 8.5GHz-11.5GHz; (g) y-polarization, ly mode: (15°, 0°) (h) y-polarization, OAM beam of 8.5GHz-11.5GHz;

[0023] Figure 6 This is a schematic diagram of the Huygens metasurface sample fabricated according to an embodiment of the present invention;

[0024] Figure 7 These are experimental test images of OAM beams with different polarizations in two modes, lx and ly, generated by the Huygens metasurface in this embodiment of the invention; lx mode: (a) phase, (b) amplitude, (c) comparison of simulated and experimental OAM beam purity. ly mode: (d) phase, (e) amplitude, (f) comparison of simulated and experimental OAM beam purity;

[0025] Figure 8 The images show far-field test results of OAM beams with different polarization angles at 9.5 GHz and 10.5 GHz generated by the Huygens metasurface in this embodiment of the invention; Scene 1 (a) lx mode: (−45°, 0°) (b) ly mode: (30°, 0°) Scene 2 (c) lx mode: (−30°, 90°) (d) ly mode: (15°, 0°). Detailed Implementation

[0027] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings.

[0028] This invention discloses a broadband Huygens metasurface and its dual-polarization mode-multiplexed OAM beam generation and control method. The working principle involves a metasurface whose basic unit consists of complementary cross-shaped metal strips at the top and bottom. Surface currents flow in opposite directions on the top and bottom metal strips, inducing surface magnetic currents generated by magnetic dipoles. These surface magnetic currents interact with the currents, leading to Huygens resonance, thus achieving full-phase coverage and high transmission efficiency without increasing the complexity of the unit structure. Furthermore, due to the anisotropic design of the cross-shaped metal strip structure, electromagnetic control independent of polarization is achieved by adjusting the lengths of the two axes of the cross-shaped metal strips separately. This Huygens metasurface operates in the 8.5 GHz–11.5 GHz frequency band, belonging to the X-band.

[0029] like Figure 1 As shown, a broadband Huygens metasurface and its dual-polarization mode multiplexing OAM beam generation and control method are described. The broadband Huygens metasurface consists of m×n Huygens metasurface units arranged according to a certain phase compensation. The feed source is located directly in front of the center of the metasurface to radiate spherical waves. The designed Huygens metasurface converts the spherical waves into variable OAM beams and can further control the deflection angle of the OAM beams.

[0030] like Figure 2 As shown, the basic unit comprises three layers, from top to bottom: a top cross-shaped metal strip layer, a middle dielectric substrate layer, and a bottom complementary cross-shaped metal strip layer. The dielectric substrate layer uses F4B material with a dielectric constant of 2.65 and a loss tangent of 0.001. The width of the metal strips remains constant at 0.2 mm. By controlling the lengths of the two axes of the top and bottom cross-shaped metal strips, the phase-shifted electromagnetic response of the same polarization (3-bit) can be tuned, laying the foundation for subsequent OAM beam design. Furthermore, since only narrower metal strips exist in the cross-polarization direction, the cross-polarization electromagnetic response remains unchanged. Due to these structural characteristics, a 3-bit phase state is selected to discretize the formula. By combining the phase distributions of the two polarizations, polarization multiplexing of the OAM beam is achieved.

[0031] like Figure 3 As shown, based on this, we simulated a metasurface array composed of corresponding units using the numerical simulation software CST Microwave Studio. Using open boundary conditions in the 8-12 GHz frequency range, the feed source was perpendicularly irradiated along the z-direction onto the designed Huygens metasurface. Its near-field phase and amplitude distributions are as follows: Figure 4 As shown. Figure 4 (b) and 4(e) show typical OAM phase distributions corresponding to the lx and ly modes, respectively, while Figure 4The amplitude distributions in (c) and 4(f) exhibit characteristic patterns with a central singularity. This demonstrates that the designed Huygens metasurface effectively generates polarization-multiplexed OAM beams, verifying the practicality of the proposed method.

[0032] like Figure 5 As shown, to further demonstrate the electromagnetic control capability of the metasurface, we independently adjust the deflection angle of the orthogonally polarized OAM beam. A phase gradient is introduced in the phase compensation to achieve beam deflection, and the deflection angle is defined as (θ, φ), where θ represents the elevation angle and φ represents the azimuth angle. To facilitate the demonstration of beam manipulation, two OAM beam deflection scenarios are given: In scenario 1, the metasurface achieves a deflection angle of (−45°, 0°) in the x-polarized lx = −1 mode and (30°, 0°) in the y-polarized ly = +1 mode, with the corresponding column phase gradients being: ( , , , , , , , , , , , , , , , , , , , , , , , (), , , , , , 0, , , , , , , , , , , , , , , , , , In scenario 2, for the x-polarized mode lx = −1, the metasurface deflection angle is (−30°, 90°), and the row phase gradient is: ( , , , , , , , , , , , , , , , , , , , , , , , For the y-polarized ly = +1 mode, with a deflection angle of (15°, 0°), the column phase gradient is: ( , , , , 0, , , , , , , ,0, 0, , , , , , , , , , Based on the relationship between unit geometry and phase response, we designed a corresponding structure to physically realize the expected function. The simulation results for scenario 1 are as follows: Figure 5 As shown in (a) and 5(c), both OAM beams are located in the xoz plane. Figure 5 (e) and 5(g) show scenario 2, where the OAM beam of ly is located in the xoz plane, while the OAM beam of lx is modulated in the yoz plane. Figure 5 (b), (d), (f), and (h) show that, in each case, the OAM beam can be observed over a wide frequency range from 8.5 GHz to 11.5 GHz. These results further validate the broadband and polarization-independent nature of the metasurface.

[0033] like Figure 6 As shown, to experimentally verify the functional feasibility and theoretical applicability, we fabricated printed circuit board samples corresponding to different functional designs. Testing. Figure 7 (a), 7(b), 7(d), and 7(e) correspond to sample 1, demonstrating the electric field amplitude and phase distribution of the transmitted wave measured using a vector network analyzer (VNA), verifying the generation and multiplexing of the OAM beam. Furthermore, Figure 7 In sections (c) and 7(f), the modal purity of the OAM beam measured by computational analysis was compared with the simulation results, confirming the effectiveness of the proposed OAM beam multiplexing generation method. Test Results Figure 8 (a) and 8(b) correspond to sample 2, showing the deflection angles in the xoz plane in the lx and ly modes as (−45°, 0°) and (30°, 0°), respectively. Figure 8 (c) and (d) correspond to sample 3, showing the beam deflection in the yoz plane (−30°, 90°) and in the xoz plane (15, 0°) in the lx and ly modes, respectively. The results confirm that the proposed Huygens metasurface effectively achieves broadband directional deflection of the OAM beam in the lx and ly modes. Therefore, the invented Huygens metasurface can independently generate and manipulate OAM beams with different polarizations over a broadband range, realizing a broadband Huygens metasurface and its dual-polarization mode-multiplexed OAM beam generation and control method.

Claims

1. A broadband Huygens metasurface and its dual-polarization mode-multiplexed OAM beam generation and control method, characterized in that, The metasurface consists of m×n Huygens metasurface basic units. Each unit comprises three layers, from top to bottom: a top cross-shaped metal strip layer, a middle dielectric substrate layer, and a bottom complementary cross-shaped metal strip layer.

2. The broadband Huygens metasurface and its dual-polarization mode-multiplexed OAM beam generation and control method according to claim 1, characterized in that, The dielectric substrate layer of the basic unit is made of polytetrafluoroethylene fiberglass cloth dielectric substrate with copper foil on both sides, with a dielectric constant of 2.65 and a loss tangent of 0.

001.

3. The broadband Huygens metasurface and its dual-polarization mode-multiplexed OAM beam generation and control method according to claim 1, characterized in that, The top and bottom layers of a single basic unit have metal strips of the same length and width, while the lengths of the unit metal strips at different locations on the metasurface vary.

4. The broadband Huygens metasurface and its dual-polarization mode-multiplexed OAM beam generation and control method according to claim 1, characterized in that, When the lengths of the two axes of the top and bottom cross-shaped metal strips change, the basic metasurface units control electromagnetic waves in different polarization directions, achieving 360° transmission phase modulation in the 8.5GHz-11.5GHz frequency band.

5. The broadband Huygens metasurface and its dual-polarization mode-multiplexed OAM beam generation and control method according to claim 1, characterized in that, The elements at different locations on the metasurface have different phases, when the phase distribution satisfies When the metasurface can generate OAM beams over a wide bandwidth, l is the OAM mode, λ is the incident electromagnetic wavelength, and F is the distance between the feed and the metasurface.

6. The broadband Huygens metasurface and its dual-polarization mode-multiplexed OAM beam generation and control method according to claim 1, characterized in that, When the two polarization directions of the metasurface satisfy the phase distribution of claim 5, the metasurface can simultaneously generate broadband dual-polarized OAM beams with modes lx and ly.

7. The broadband Huygens metasurface and its dual-polarization mode-multiplexed OAM beam generation and control method according to claim 1, characterized in that, Based on the simultaneous generation of dual-polarized OAM beams with modes lx and ly, the metasurface further superimposes different phase gradient distributions in the two polarization directions. and The metasurface can realize OAM beam scanning with broadband dual-polarization mode multiplexing in the xoz and yoz polarization planes respectively.

Images