Dual-frequency independent modulation superstructure grating

Abstract

The application relates to the technical field of microwave communication, in particular to a double-frequency independent regulation superstructure grating, which comprises a plurality of superstructure units, the superstructure units are periodically arranged in a two-dimensional direction, each superstructure unit comprises a dielectric substrate, a reflecting plate and a conductor structure; the grating can equivalently regard the low-frequency band of the superstructure unit as one period, equivalently regard two high-frequency response conductors as two periods, so that the superstructure grating can work in two frequency bands at the same time, in each frequency band, the superstructure unit has independent variable parameters for adjusting impedance density, thereby realizing a specific response designed. Only one superstructure unit can realize independent regulation of a double-frequency beam, the independent parameters in two frequencies can realize control of the impedance of the unit, the structure is simple and easy to realize; the problems that the realization of the double-frequency superstructure grating can only be realized by overlapping the units working under two frequencies or by designing an active superstructure grating to realize regulation of the frequency are solved, the structure is relatively complex and difficult to realize.

Description

Technical Field

[0001] This invention relates to the field of microwave communication technology, specifically to a dual-frequency independently modulated meta-grating. Background Technology

[0002] Metagratings are a novel type of electromagnetic wave manipulation device that overcomes some of the defects of traditional metasurfaces. They can achieve the required beam transformation by precisely adjusting the diffraction field and have important application value in sensing, spectral control, absorption, and imaging. They have always been a research hotspot in academia.

[0003] In recent decades, metamaterials constructed from subwavelength artificial design units have exhibited properties and functions not found in natural materials, such as negative permittivity, negative refraction, stealth, and filtering. However, due to their three-dimensional nature, metamaterials face limitations such as high fabrication difficulty and low efficiency. Researchers have further developed the concept of metasurfaces by arranging metaunits in two dimensions. Metasurfaces possess ultrathin planar structures and flexible beam manipulation capabilities, making them an important branch of micro-nano optics. However, the manipulation of the light field by metasurfaces is achieved through phase abrupt changes generated by a single-layer scatterer, relying on local resonance of independent unit structures, which leads to impedance mismatch issues and makes it difficult to design them passively and losslessly, thus limiting efficiency improvements. Gradient-unit metasurfaces are inherently limited by discrete phase sampling, resulting in low conversion efficiency and hindering applications in areas such as large-angle deflection and large-aperture focusing. To address this issue, metagratings were developed by combining the diffraction properties of gratings with the scattering modulation characteristics of metaatoms. Metagratings are composed of periodically sparsely arranged metaunits with specific electromagnetic responses. By designing the units to generate the optimal diffraction mode that matches the desired output field, metagratings can meet the conditions of being passive and lossless, breaking the limitations between large-angle wavefront shaping and conversion efficiency, and providing a simpler and more effective way to control diffraction light fields.

[0004] Metagratings are two-dimensional structures composed of periodic polarization line currents or line current arrays. They have a deep subwavelength period in one direction, forming a certain impedance density in that dimension. The period in the other direction determines the number of modes that can propagate, and the propagation angle of each mode is determined by the grating equations.

[0005]

[0006] Once the incident angle θ is determined, the number of diffraction modes is controlled by selecting the period Λ. Under oblique incidence conditions, by selecting a certain range of periods, it can be ensured that only one diffraction mode exists besides the zero mode. The diffraction modes of the metagrating can be accurately analyzed using analytical expressions. When excited by an external electromagnetic field, it produces a scattered field of the form of the sum of Flokai harmonics, which is related to the unit cell characteristics and geometric arrangement. Using Ohm's law and the no-power-dissipation condition, the impedance density matching the realized diffraction field mode can be calculated. Therefore, the metagrating can achieve efficient functions such as anomalous diffraction, beam splitting, and near-field manipulation.

[0007] Although metagratings can manipulate electromagnetic waves efficiently, their period is frequency-dependent according to the diffraction equation. The realization of dual-frequency metagratings can only be achieved by overlapping the units operating at two frequencies, or by designing active metagratings to control the frequency, which is structurally complex and difficult to implement. Summary of the Invention

[0008] To address the problem that existing technologies for dual-frequency meta-gratings can only achieve frequency control by overlapping units operating at two frequencies or by designing active meta-gratings, which are complex and difficult to implement, this invention provides a dual-frequency independently controllable meta-grating. The same meta-unit can operate simultaneously in two frequency bands through periodic switching. It has a simple structure, is easy to manufacture, and has low cost.

[0009] To achieve the above objectives, the present invention employs the following technical solution:

[0010] A dual-frequency independently controllable meta-grating, characterized in that it comprises a plurality of meta-units, the meta-units being periodically arranged in a two-dimensional direction, each meta-unit comprising a dielectric substrate, a reflector and a conductor structure;

[0011] The conductor structure is disposed on the surface of the dielectric substrate. The conductor structure includes a low-frequency response conductor and two high-frequency response conductors. The high-frequency response conductors are symmetrically disposed on the dielectric substrate on both sides of the low-frequency response conductors, and the high-frequency response conductors and the low-frequency response conductors are connected by metal connecting wires.

[0012] The reflective substrate is disposed on the surface of the dielectric substrate opposite to the conductor structure.

[0013] Preferably, the dielectric substrate is a high-frequency PCB material with a dielectric constant of 3 and a loss tangent of 0.0007.

[0014] Preferably, the thickness of the dielectric substrate is 5.5 mm to 7.5 mm.

[0015] Preferably, the reflector is made of copper.

[0016] Preferably, the thickness of the reflector is 0.03mm to 0.05mm.

[0017] Preferably, the conductor structure is made of copper wire.

[0018] Preferably, the width of the copper wire is less than one-tenth of the wavelength.

[0019] Preferably, the low-frequency response conductor is a closed rectangular structure, the high-frequency response conductor is an I-shaped structure, and the two high-frequency response conductors are perpendicularly connected to both sides of the low-frequency response conductor by metal connecting wires.

[0020] Preferably, the metaunit has dual-frequency response characteristics.

[0021] Preferably, the meta-grating exhibits the following characteristics: at a center frequency of 20 GHz, with an incident angle of 10°, the deflection angle is -55° and the efficiency is 93.6%; at a center frequency of 6.16 GHz, it has broadband characteristics: at an incident angle of 65°, the deflection angle is -64° and the efficiency is 93% at 5.5 GHz; at a center frequency of 6.16 GHz, the deflection angle is -45° and the efficiency is 94.6%; and at a center frequency of 6.5 GHz, the deflection angle is -38° and the efficiency is 97.6%.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] This invention discloses a dual-frequency independently controllable meta-grating, comprising several meta-units arranged periodically in a two-dimensional direction. Each meta-unit includes a dielectric substrate, a reflector, and a conductor structure. The conductor structure can generate a specific distributed current under the excitation of an incident wave, and the -1 diffraction energy can be varied by adjusting the load impedance per unit length. The dielectric substrate can cancel out the specular reflection caused by the reflector and the field of the 0th diffraction order of the grating. The reflector can also suppress diffraction at the transmission end. By setting the low-frequency response conductor and two high-frequency response conductors in the conductor structure, the low-frequency band of the meta-unit can be equivalent to one period, and the two high-frequency response conductors can be equivalent to two periods, allowing the meta-grating to operate simultaneously in two frequency bands. In each frequency band, the meta-unit has independent variable parameters to adjust the impedance density, thereby achieving the designed specific response. It can switch between high and low frequencies by multiples of the cycle, and can achieve independent control of dual-frequency beams through only one metacell. It has independent parameters at the two frequencies, which can realize the control of the unit impedance. It has a simple structure, is easy to implement, easy to process, and easy to integrate. It has important application value in microwave communication, holography, sensing, filtering and other fields.

[0024] Furthermore, the dielectric substrate is made of a high-frequency PCB material with a dielectric constant of 3 and a loss tangent of 0.0007. The thickness of the dielectric substrate is designed to ensure that the specular reflection brought by the reflector cancels out the field of the 0th diffraction order of the grating.

[0025] Furthermore, the material and thickness of the reflector can effectively suppress diffraction at the transmission end, so that the meta-grating only has diffraction modes at the reflection end.

[0026] Furthermore, the material, width parameters, and structural settings of the conductor structure can enable it to generate a specific distributed current under the excitation of the incident wave. By adjusting the magnitude of the load impedance per unit length, the energy of the -1 diffraction order can be maximized.

[0027] Furthermore, testing revealed that the metasurface exhibits a deflection angle of -55° and an efficiency of 93.6% at a center frequency of 20 GHz and an incident angle of 10°. It also demonstrates broadband characteristics at a center frequency of 6.16 GHz, with a deflection angle of -64° and an efficiency of 93% at 5.5 GHz and a deflection angle of -45° at 6.16 GHz, resulting in an efficiency of 94.6%. Finally, at a center frequency of 6.5 GHz, the deflection angle is -38°, achieving an efficiency of 97.6%. This demonstrates highly efficient beam control capabilities, overcoming the problem of low large-angle diffraction efficiency caused by impedance mismatch in metasurfaces. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of a dual-frequency independently controllable meta-grating according to the present invention.

[0029] Figure 2 This is a structural diagram of the metacellular unit of the present invention.

[0030] Figure 3 This is a schematic diagram of the geometric parameters of the metaunit of the present invention.

[0031] Figure 4 This is a schematic diagram of the surface current and impedance density of the present invention; wherein, (a) is the surface current distribution diagram when f1 = 6.16 GHz, (b) is the surface current distribution diagram when f2 = 20 GHz, (c) is the curve of the element impedance density as a function of the element structure parameter g, and (d) is the curve of the element impedance density as a function of the element structure parameter A.

[0032] Figure 5 The following are simulation results of the infinite periodic structure of the present invention; wherein, (a) is a schematic diagram of the diffraction angle when the center frequency f1 = 6.16 GHz, (b) is a schematic diagram of the diffraction angle when f2 = 20 GHz, (c) is the diffraction efficiency curve in the low frequency band, and (d) is the diffraction efficiency curve in the high frequency band.

[0033] Figure 6 The image shows the far-field direction simulation results of the 10×50 finite periodic structure of the present invention.

[0034] Among them, 1-dielectric substrate, 2-reflector, 3-conductor structure, 31-low frequency response wire, 32-high frequency response wire, 33-metal connecting wire. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0036] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0037] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0038] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present invention 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 the present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0039] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0040] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0041] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0042] See Figure 1 The present invention discloses a dual-frequency independently controllable meta-grating, comprising a plurality of meta-units, wherein the meta-units are periodically arranged in a two-dimensional direction and the meta-units have dual-frequency response characteristics;

[0043] See Figure 2 Each meta-unit includes a dielectric substrate 1, a reflector 2, and a conductor structure 3;

[0044] The conductor structure 3 is disposed on the surface of the dielectric substrate 1. The conductor structure 3 includes a low-frequency response wire 31 and two high-frequency response wires 32. The high-frequency response wires 32 are symmetrically disposed on the dielectric substrate 1 on both sides of the low-frequency response wire 31 and are connected to the low-frequency response wire 31 through a metal connecting wire 33.

[0045] The reflective substrate 2 is disposed on the surface of the dielectric substrate 1 opposite to the conductor structure 3.

[0046] Preferably, the dielectric substrate 1 is made of F4BM300 high-frequency PCB board with a dielectric constant of 3 and a loss tangent of 0.0007; the thickness of the dielectric substrate 1 is 5.5mm to 7.5mm, preferably 6.82mm; the reflector 2 is made of copper, and the thickness of the reflector 2 is 0.03mm to 0.05mm, preferably 0.035mm; the conductor structure 3 is made of copper wire, and the width of the copper wire is less than one-tenth of the wavelength, which is 0.4mm to 0.6mm, preferably 0.5mm.

[0047] Testing revealed that the meta-grating exhibits the following characteristics: at a center frequency of 20 GHz and an incident angle of 10°, the deflection angle is -55° with an efficiency of 93.6%; at a center frequency of 6.16 GHz, it demonstrates broadband characteristics: at 5.5 GHz with an incident angle of 65°, the deflection angle is -64° with an efficiency of 93%; at a center frequency of 6.16 GHz, the deflection angle is -45° with an efficiency of 94.6%; and at a center frequency of 6.5 GHz, the deflection angle is -38° with an efficiency of 97.6%.

[0048] Preferably, in this invention, the arm length of the high-frequency response conductor is denoted as parameter A, and the width of the low-frequency response conductor is denoted as parameter g, as two variable parameters. This is because they can cover a wide range of load impedance densities, and these two parameters can be independently adjusted at the two frequencies. A only affects the unit impedance at high frequencies, and g only affects the unit impedance at low frequencies. To verify the limitations of the proposed scheme, a dual-frequency meta-grating consisting of 10 × 50 periods, capable of operating simultaneously at 6.16 GHz and 20 GHz, was designed, using a dielectric constant ε. r Using F4BM300 as dielectric substrate 1, with a loss tangent tanδ = 0.0007 and a thickness of 6.82 mm, a beam deflection of -55° can be achieved at a center frequency of 20 GHz and an incident angle of 10°. At a center frequency of 5.5 GHz to 6.5 GHz and an incident angle of 65°, a beam deflection of 38° to 64° can be achieved. The diffraction efficiency exceeds 93% in both cases.

[0049] The specific design method is as follows:

[0050] Step 1), under oblique incidence conditions, maximize the -1 diffraction order energy using a single metaunit;

[0051] Step 2), calculate the load impedance density required to maximize the energy of the -1 diffraction order, and plot the load impedance density variation curve;

[0052] Step 3): Based on the load impedance density variation curves at two frequencies, design the scattering parameter values ​​of the meta-unit.

[0053] Step 4) Based on the theoretical design, simulations are performed on the infinite periodic structure and the finite periodic structure respectively to further verify their performance;

[0054] Step 5) Based on simulation verification, the PCB meta-grating with finite periodic structure is processed and its performance is tested.

[0055] See Figure 3The period length along the y-axis is Ly = 30.21 mm, the period length along the x-axis is Lx = 6 mm, the thickness of the dielectric substrate 1 is h = 6.82 mm, the wire width is w = 0.5 mm, the length of the metal connecting wire 33 is B = 2.5 mm, the length of the low-frequency response wire 31 is D = 9.105 mm, and the arm length A of the high-frequency response wire 32 and the width g of the low-frequency response wire 31 are two adjustable parameters used to adjust the impedance density of the unit.

[0056] See Figure 4 At low frequency f1, the induced current is generated almost entirely by the central rectangular structure of the elementary atoms, while at high frequency f2, the superunit is equivalent to two completely symmetrical units that generate the induced current, with the central part having almost no effect. Therefore, the period is converted to L. y / 2. Through multiple-cycle conversion, the proposed structure can achieve independent beam control at two different frequencies. The impedance density curves at the two different frequencies, as well as the unit structure parameters A and g, show that at frequency f1, parameter g is an independent parameter for impedance density adjustment, while at frequency f2, parameter A is another independent parameter for adjusting the impedance density.

[0057] See Figure 5 Through periodic simulation results, it can be observed that at 6.16 GHz, the meta-grating can reflect the incident beam in the 65° direction to -45° with a diffraction efficiency of 99.2% and a relative bandwidth of over 20%; at 20 GHz, it can reflect the incident beam in the 10° direction to -55° with a diffraction efficiency of 94.5%.

[0058] See Figure 6 Simulation results show that at incident angles of 65° at frequencies of 5.5 GHz, 6.16 GHz, and 6.5 GHz, the main lobe points to -64° with an efficiency of 93% and a half-wavelength of 20°; at 6.16 GHz, the main lobe points to -45° with an efficiency of 94.6% and a half-wavelength of 11°; and at 6.5 GHz, the main lobe points to -38° with an efficiency of 97.5% and a half-wavelength of 10°. At 20 GHz, with an incident angle of 10°, the main lobe points to -55° with an efficiency of 93.6% and a half-wavelength of 4.7°. The far-field simulation results are consistent with the theoretical design, and the efficiency exceeds 93% in both frequency bands.

[0059] In summary, this invention provides a dual-frequency independently controllable meta-grating. This grating can achieve independent control of dual-frequency beams through only one meta-unit. It has independent parameters at the two frequencies, which can control the unit impedance. The structure is simple and easy to implement.

[0060] The above description is merely a preferred embodiment of the present invention and is not intended to limit the technical solution of the present invention in any way. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can be modified and replaced in several simple ways, and these modifications and replacements are all within the scope of protection covered by the claims.

Claims

1. A dual-frequency independently controllable meta-grating, characterized in that, It includes several meta-units, which are periodically arranged in a two-dimensional direction. Each meta-unit includes a dielectric substrate (1), a reflector (2), and a conductor structure (3). The meta-unit has dual-frequency response characteristics. The conductor structure (3) is disposed on the surface of the dielectric substrate (1). The conductor structure (3) includes a low-frequency response conductor (31) and two high-frequency response conductors (32). The high-frequency response conductors (32) are symmetrically disposed on the dielectric substrate (1) on both sides of the low-frequency response conductor (31), and the high-frequency response conductors (32) and the low-frequency response conductors (31) are connected by metal connecting lines (33). The low-frequency response conductor (31) is a closed rectangular structure, and the high-frequency response conductors (32) are I-shaped structures. The two high-frequency response conductors (32) are perpendicularly connected to both sides of the low-frequency response conductor (31) by metal connecting lines (33). The reflector (2) is disposed on the surface of the dielectric substrate (1) opposite to the conductor structure (3).

2. The dual-frequency independently controllable meta-grating according to claim 1, characterized in that, The dielectric substrate (1) is made of a high-frequency PCB material with a dielectric constant of 3 and a loss tangent of 0.0007.

3. The dual-frequency independently controllable meta-grating according to claim 2, characterized in that, The thickness of the dielectric substrate (1) is 5.5 mm to 7.5 mm.

4. The dual-frequency independently controllable meta-grating according to claim 1, characterized in that, The material of the reflector (2) is copper.

5. The dual-frequency independently controllable meta-grating according to claim 4, characterized in that, The thickness of the reflector (2) is 0.03mm to 0.05mm.

6. The dual-frequency independently controllable meta-grating according to claim 1, characterized in that, The conductor structure (3) is made of copper wire.

7. The dual-frequency independently controllable meta-grating according to claim 6, characterized in that, The width of the copper wire is less than one-tenth of the wavelength.

8. The dual-frequency independently controllable meta-grating according to any one of claims 1-7, characterized in that, The meta-grating exhibits a deflection angle of -55° and an efficiency of 93.6% at a center frequency of 20 GHz and an incident angle of 10°. It also demonstrates broadband characteristics at a center frequency of 6.16 GHz, with a deflection angle of -64° and an efficiency of 93% at a center frequency of 5.5 GHz and an incident angle of 65°; a deflection angle of -45° and an efficiency of 94.6% at a center frequency of 6.16 GHz; and a deflection angle of -38° and an efficiency of 97.6% at a center frequency of 6.5 GHz.

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