A multi-polarization conversion reflection method based on 1-bit electromagnetic metasurface

Abstract

The application discloses a multi-polarization conversion reflection method based on a 1-bit electromagnetic metasurface, belongs to the field of wide-angle regulation of spatial electromagnetic waves, and comprises the following steps: a 180-degree phase difference code of state 0 and state 1 is realized by constructing a double-layer resonance structure and introducing a mirror-symmetry unit. The structure supports polarization conversion and reflection regulation of linear polarization and circular polarization incident waves in a wide-angle range, and has the characteristics of low loss and high conversion efficiency. Based on phase compensation and state coding, an 8*8 array is constructed to realize three-dimensional beam regulation and angle reciprocity verification, is suitable for far-field gain acquisition under excitation of various polarization feed sources, and significantly improves the flexibility and resource utilization rate of a communication system.

Description

Technical Field

[0001] This invention belongs to the field of wide-angle manipulation of spatial electromagnetic waves, and particularly relates to a multi-polarization conversion reflection method based on a 1-bit electromagnetic metasurface. Background Technology

[0002] With the development of technology, stable and efficient communication technology has become a core requirement in fields such as medicine, military industry, and the industrial internet. Both wireless and wired communication rely on the transmission of electromagnetic waves. Therefore, how to quickly and accurately control the physical characteristics of electromagnetic waves (such as wavelength, amplitude, polarization, and frequency) has become a critical issue that urgently needs to be addressed. These characteristics not only determine the quality of communication content but also improve the security and reliability of information transmission. By controlling electromagnetic waves, various functions such as signal amplification, encryption, and directional coverage can be achieved.

[0003] Electromagnetic metasurfaces have become a research hotspot. These two-dimensional structures have a thickness only a fraction of the operating wavelength, ranging from a few tenths to a few hundredths. Through special design, they can achieve negative permeability and negative permittivity, exhibiting anomalous refraction and reflection properties, thus enabling precise control of electromagnetic waves. Among various types of electromagnetic metasurfaces, coded metasurfaces have attracted significant attention due to their flexible electromagnetic wave control capabilities and wide range of applications. Coded metasurfaces can be categorized into reflective, transmissive, and hybrid transmissive-reflective types. Reflective coded metasurfaces undoubtedly offer more advantages: ① easier to achieve diffuse reflection; ② higher space utilization; ③ higher electromagnetic wave utilization efficiency; ④ flexible feed placement, facilitating research on metasurface operation under non-perpendicular incidence. A 1-bit metasurface is one of the simplest representations of a coded metasurface, possessing two-state encoding of "0" and "1," providing a convenient control method while reducing design complexity and operational losses. However, as mentioned above, polarization conversion capability is currently a research hotspot, and traditional 1-bit unit designs only focus on phase control, limiting application scenarios. Furthermore, existing research is mostly based on ideal conditions of perpendicular incidence, lacking exploration of phase stability under wide-angle incidence. Therefore, developing a 1-bit multi-polarization conversion reflection method that can operate stably over a wide angle has become the key to solving the bottleneck in practical applications. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a multi-polarization conversion reflection method based on a 1-bit electromagnetic metasurface, comprising:

[0005] The target frequency band was determined and a two-dimensional double-layer microstrip structure was constructed accordingly. Based on transmission line theory, electromagnetic coupling effect and equivalent circuit theory, a double-layer resonant structure consisting of an upper square resonant patch and a lower aperture resonant patch was designed.

[0006] By performing x-axis mirror symmetry on the double-layer resonant structure, two mirror-image unit structures are obtained, which serve as state 0 and state 1 of the 1-bit metasurface.

[0007] Electromagnetic simulations were performed on the state 0 and state 1 units respectively to obtain the phase, amplitude and polarization conversion parameters of the reflected waves under different incident polarization waves and different elevation angles.

[0008] Based on the simulation results, an 8×8 small metasurface array was constructed to verify the results. Three-dimensional beam control was achieved through phase compensation and state coding, and its angle reciprocity was verified.

[0009] The 8×8 metasurface array is excited by linearly polarized feed sources and circularly polarized feed sources respectively to obtain the far-field gain distribution and realize the multi-polarization conversion reflection function.

[0010] Optionally, determining the target frequency band and constructing a two-dimensional dual-layer microstrip structure includes:

[0011] Select the operating frequency band based on the application scenario, and determine the side length of the microstrip structure by combining the wavelength calculation formula;

[0012] The microstrip structure is designed as a reflective structure consisting of a double-layer metal patch and a dielectric substrate. The double-layer metal patch includes an upper square patch and a lower open-hole resonant patch.

[0013] Optionally, the lower-layer open-hole resonant patch includes an outer double-opening annular shape and an inner regular octagon;

[0014] The structure of the lower-layer open-hole resonant patch includes:

[0015] The outer double-opening ring structure has its opening direction aligned with the x-axis or y-axis.

[0016] It has an inner regular octagonal structure with a cross-shaped opening slot rotated 45° in the center, which is used to adjust the polarization state of the reflected wave.

[0017] The outer double-opening ring and the inner regular octagon are used to adjust the phase and amplitude of the reflected wave through electromagnetic coupling.

[0018] Optionally, the mirror symmetry operation is used to generate state 1 unit, including: mirror symmetrically flipping state 0 unit along the x-axis, so that the opening direction of the outer double-opening ring changes from +x / +y to +x / -y, completing the introduction of a 180° phase difference and realizing 1-bit encoding.

[0019] Optionally, the electromagnetic simulation includes:

[0020] For linearly polarized incident waves, scan their elevation angle changes to obtain the reflection coefficients and phase differences of circularly polarized reflected waves of state 0 and state 1 elements under x-polarization and y-polarization.

[0021] For a circularly polarized incident wave, obtain the reflection loss and co-polarization / cross-polarization conversion parameters of the state 0 and state 1 elements under vertical incidence.

[0022] Optionally, the construction of the 8×8 metasurface array includes:

[0023] Arrange the state 0 and state 1 units into an 8×8 array according to the preset encoding rules;

[0024] The compensation phase of each element is calculated using the phase compensation formula, and the element state is iteratively adjusted using a Matlab optimization algorithm to achieve the target beam pointing.

[0025] Optionally, the three-dimensional beam modulation includes:

[0026] With a linearly polarized feed incident vertically, beam deflection within the elevation angle range of 0°–45° is achieved by adjusting the unit state coding;

[0027] Record the far-field gain distribution under different deflection angles to verify the correspondence between beam pointing and cell state.

[0028] Optionally, the angle reciprocity verification includes:

[0029] Keeping the relative positions of the feed and the array unchanged, adjust the feed incident elevation angle and detect whether the reflected wave points to the original incident direction;

[0030] Record the reciprocal correspondence between the angle of incidence and the angle of reflection when the state code remains unchanged.

[0031] On the other hand, the present invention also provides an electronic device including a memory, a processor, and a computing program stored in the memory and executable on the processor, wherein the processor implements the method when executing the computing program.

[0032] On the other hand, the present invention also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the method.

[0033] Compared with the prior art, the present invention has the following advantages and technical effects:

[0034] Compared to traditional methods for realizing 1-bit metasurfaces, this invention enables simultaneous control of 1-bit phase and polarization conversion at wide angles, overcoming the limitations of 1-bit metasurface application scenarios and significantly improving the applicability of metasurface relay control in dynamic scenarios. This low requirement for the incident source greatly increases electromagnetic wave utilization, making it an ideal choice for electromagnetic signal processing, wireless communication, and microwave imaging. The electromagnetic metasurface realized by this method exhibits extremely low reflection loss at all operating incident angles, a valuable characteristic required for wireless transmission. Simultaneously, this 1-bit metasurface achieves three-dimensional beamforming, satisfying the angle reciprocity characteristic based on wide angles, solving the problem of complex beamforming devices, and providing a basic solution for applying metasurfaces in dual-link systems to address signal deviation. Ultimately, both states of the metasurface can achieve orthogonal reflected waves of different frequency bands under perpendicularly incident circularly polarized waves, ensuring improved communication capacity and information processing accuracy through enhanced frequency band and polarization characteristics, and also enabling functions such as multi-target detection and multi-target tracking. Attached Figure Description

[0035] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0036] Figure 1 This is a schematic diagram of the method flow according to an embodiment of the present invention;

[0037] Figure 2 These are the front view and cross-sectional view of the electromagnetic metasurface unit in an embodiment of the present invention.

[0038] Figure 3 This is a schematic diagram of the electromagnetic metasurface unit in an embodiment of the present invention.

[0039] Figure 4 This is a schematic diagram of the initial structure, mirror symmetry structure, and two coordinate systems of the electromagnetic metasurface unit in an embodiment of the present invention.

[0040] Figure 5 The reflection coefficients and phase differences of the electromagnetic metasurface unit under different operating states of the same polarization and cross polarization when a wide-angle y-polarized wave is incident are shown in the embodiments of the present invention.

[0041] Figure 6 This is a schematic diagram of the co-polarization and cross-polarization reflection loss of the electromagnetic metasurface unit under different operating states when a right-hand circularly polarized wave is incident, according to an embodiment of the present invention.

[0042] Figure 7 This is a schematic diagram showing the axial ratio and normalized ellipticity of the electromagnetic metasurface unit under different working states at a wide angle in an embodiment of the present invention.

[0043] Figure 8 This is a schematic diagram showing the circular polarization wave reflection loss and circular polarization wave state phase difference of the electromagnetic metasurface unit under different working states at a wide angle in an embodiment of the present invention.

[0044] Figure 9 This is a schematic diagram of the polarization conversion rate when a right-handed circularly polarized wave is incident, as shown in an embodiment of the present invention.

[0045] Figure 10 This is a schematic diagram of metasurface beam control and a unit state table in an embodiment of the present invention.

[0046] Figure 11 This is a schematic diagram and a cell state table for verifying the metasurface angle reciprocity in an embodiment of the present invention.

[0047] Figure 12 This invention is used to verify the far-field plots and polar plots of metasurface angle-based same-polarization conversion and cross-polarization conversion in embodiments of the invention.

[0048] The components are: 1. Upper reflective metal patch; 2. Lower perforated metal patch; 3. Dielectric cylinder; 4. Dielectric substrate; 5. Metal ground plane. Detailed Implementation

[0049] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0050] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0051] Please explain the following terms:

[0052] Reflective Electromagnetic Metasurface (REMMetasurface): This electromagnetic material is a two-dimensional subwavelength structure with a thickness only a fraction of the wavelength. By designing the surface structure to cause a phase abrupt change in the incident electromagnetic wave, the physical properties of the reflected electromagnetic wave—polarization, amplitude, frequency, and phase—can be controlled.

[0053] 1-bit reflective electromagnetic metasurface: This type of metasurface is a coded metasurface with two unit states, represented by codes "0" and "1", and has a 180° phase difference.

[0054] Axial ratio (AR): A parameter that measures whether an electromagnetic wave is linearly polarized or circularly polarized. When the axial ratio is greater than 3dB, it confirms that the beam is linearly polarized; when the axial ratio is in the range of 0-3dB, it confirms that the beam is circularly polarized.

[0055] Normalized ellipticity (NE): A parameter that measures the left-hand circular polarization and right-hand circular polarization of electromagnetic waves. When the value is approximately -1, it is a right-hand circularly polarized wave, and +1 is a left-hand circularly polarized wave.

[0056] State phase difference: The phase difference of the reflected wave of the unit under different states.

[0057] Polarization Conversion Ratio (PCR): A parameter that measures the efficiency of converting an incident initially polarized electromagnetic wave into a target polarized electromagnetic wave. Its value is in the range of 0-1, and the polarization conversion efficiency increases with the value.

[0058] Example 1

[0059] This embodiment provides a multi-polarization conversion reflection method based on a 1-bit electromagnetic metasurface, including:

[0060] The target frequency band was determined and a two-dimensional double-layer microstrip structure was constructed accordingly. Based on transmission line theory, electromagnetic coupling effect and equivalent circuit theory, a double-layer resonant structure consisting of an upper square resonant patch and a lower aperture resonant patch was designed.

[0061] By performing x-axis mirror symmetry on the double-layer resonant structure, two mirror-image unit structures are obtained, which serve as state 0 and state 1 of the 1-bit metasurface.

[0062] Electromagnetic simulations were performed on the state 0 and state 1 units respectively to obtain the phase, amplitude and polarization conversion parameters of the reflected waves under different incident polarization waves and different elevation angles.

[0063] Based on the simulation results, an 8×8 small metasurface array was constructed to verify the results. Three-dimensional beam control was achieved through phase compensation and state coding, and its angle reciprocity was verified.

[0064] The 8×8 metasurface array is excited by linearly polarized feed sources and circularly polarized feed sources respectively to obtain the far-field gain distribution and realize the multi-polarization conversion reflection function.

[0065] S1. Determine the operating frequency band of the metasurface and determine the size of the two-dimensional microstrip structure based on the wavelength calculation formula and actual optimization. Design a double-layer resonant patch based on transmission line theory, electromagnetic coupling effect, and equivalent circuit theory to obtain linear-circular polarization conversion and circular-multi-circular polarization conversion metasurface units. Obtain the new unit structure after mirror symmetry of the metasurface unit along the x-axis to obtain a reflective 1-bit multi-polarization conversion electromagnetic metasurface unit;

[0066] S101. Determine the target operating frequency band of the invention based on currently common application frequency bands. Calculate the corresponding wavelength using the wavelength calculation formula to obtain the precise length and width of the two-dimensional microstrip structure;

[0067] S102. For linear-circular polarization conversion, the circularly polarized reflected wave is decomposed into +x and +y directions, with equal amplitudes and a phase difference of +90°. For circular-multi-circular polarization conversion, the reflected wave exhibits co-polarization and cross-polarization in different frequency bands. Therefore, based on transmission line theory, electromagnetic coupling effect, and equivalent circuit theory, the design of the double-layer resonant structure is determined to ensure that the polarization components meet the above criteria, thus obtaining the corresponding metasurface unit.

[0068] S103. Mirror-symmetrically represent the above metasurface unit along the x-axis. For linear-circular polarization conversion, decompose the circularly polarized reflected wave into +x and +y directions, with equal amplitudes and a phase difference of -90°. For circular-multi-circular polarization conversion, the reflected wave exhibits co-polarization and cross-polarization at different frequency bands. The linear-circular polarization reflected waves of both types have a 180° phase difference, resulting in a reflective 1-bit metasurface. For circular-multi-circular polarization conversion, the reflected waves maintain co-polarization and cross-polarization, resulting in a multi-circular polarization converter.

[0069] Specifically, when the line-circle configuration is used, a 1-bit metasurface is constructed, and the reflected waves are left-handed and right-handed circularly polarized reflected waves with a phase difference of 180 degrees. When the circle-circle configuration is used, a multi-circularly polarized reflector is constructed, realizing co-polarized and cross-polarized circular reflected waves.

[0070] In this embodiment, the polarization state of the electromagnetic wave represents the shape profile of the electric field vector in space as it changes over time. When the electromagnetic wave propagates incidentally along the -z direction, the electric fields in the incident x and y directions are as follows:

[0071]

[0072] in, Let x be the initial electric field vector in the x and y directions, and k be the space wave vector, whose value is equal to... ω is the angular velocity, and ωt reflects the change of the electric field phase with time.

[0073] The reflected circularly polarized wave propagates along the +z direction, and can be decomposed into x-polarized and y-polarized waves. The electric fields of the reflected waves can be expressed as follows:

[0074]

[0075] Where, r x r y These are the x-polarized reflection coefficient and the y-polarized reflection coefficient. This is the initial electric field vector.

[0076] The phase difference between the y-polarized and x-polarized reflected waves is as follows:

[0077]

[0078] in, The initial phases are in the y and x directions.

[0079] For the optimal reflected circularly polarized wave, the electric field completely satisfies... (n = 0, ±1, ±2…), that is, when the y-polarization component lags behind the x-polarization component… Right-hand circular polarization is achieved when n = 0, ±1, ±2…; (n = 0, ±1, ±2…), that is, when the y-polarization component leads the x-polarization component. Left-hand circular polarization is achieved when n = 0, ±1, ±2…. The synthesized right-hand and left-hand circularly polarized waves are represented as follows:

[0080]

[0081] Where - represents right-handed circular polarization and + represents left-handed circular polarization. These are the normalized coefficients.

[0082] To facilitate the explanation of this embodiment, we take a y-polarized incident wave as an example. From the above analysis, it can be concluded that the same-polarized and cross-polarized reflected waves must satisfy the following conditions: equal amplitude and phase difference. conditions.

[0083] To meet the above conditions, this embodiment combines transmission line theory, electromagnetic coupling effect, and equivalent circuit theory, starting with an asymmetric, two-layer structure, and gradually optimizes and controls the same polarization and cross polarization components of the reflected wave. By achieving an initial state of mirror-symmetric units, the current directions on the unit surface under linearly polarized incident waves are orthogonal to each other, thus the polarization forms of the two units are orthogonal. Based on this, the units have completely different current paths, resulting in a 180° phase difference between them, thereby generating orthogonal circularly polarized reflected waves with a 180° phase difference. At this point, the polarization judgment value of the circularly polarized reflected wave has not reached the critical state, and the operating frequency band is much larger than WLAN 5.8GHz, initially indicating wide-angle stability.

[0084] In this embodiment, the method for converting the x-polarized incident wave into a circularly polarized reflected wave is the same as above.

[0085] To facilitate the explanation of this embodiment, a right-hand circularly polarized incident wave is taken as an example. From the above analysis, it can be concluded that its x-polarized and y-polarized reflected waves must satisfy the following conditions: equal amplitude and phase difference.

[0086] To meet the aforementioned amplitude and phase requirements, this embodiment differs from traditional inventions by rationally designing the patch to alter the surface current resonance forms in the x and y directions, thereby achieving co-circularly polarized and cross-circularly polarized reflectors in different frequency bands. The cross-shaped slot current loop does not affect the phase of the x and y direction waves. Through the combined action of the upper reflective metal patch, the outer double-opening ring, and the inner regular octagonal surface current loop, a phase state is achieved where the y-direction wave leads the x-direction wave by 90° or lags the x-direction wave by 90°, producing co-polarized and cross-polarized reflection effects.

[0087] In this embodiment, the method for achieving co-polarization and cross-polarization reflection of left-hand circularly polarized incident waves is the same as above.

[0088] In this embodiment, compared to a traditional 1-bit metasurface, it has more functions and a simpler design. A 1-bit phase can be achieved simply through mirror symmetry, without requiring a new cell design. Furthermore, the cells of the two structures can achieve cross-polarization and co-polarization under circularly polarized incident light. By adjusting the cell size, the metasurface can be applied to other frequencies.

[0089] S2. Let the initial unit be state 0 and the mirror-symmetric unit be state 1. Obtain the phase difference and reflection coefficient parameters of the double-layer resonant patch and reflected wave in state 0, and the phase difference and reflection coefficient parameters of the double-layer resonant patch and reflected wave in state 1, for linearly polarized incident waves (x / y polarization) at different elevation angles. Transform the incident wave into a circularly polarized wave with an elevation angle of 0° to obtain the double-layer resonant patch and reflected wave loss parameters in state 0, and the double-layer resonant patch and reflected wave loss parameters in state 1.

[0090] S201. Group the metasurfaces in the two states. The initial element is denoted as state 0, corresponding to the double-opening rings pointing towards the +x and +y directions. The mirror-symmetric element is denoted as state 1, corresponding to the double-opening rings pointing towards the +x and -y directions.

[0091] S202. Based on the grouping results, change the elevation angle of the linearly polarized incident wave to obtain the phase difference and reflection coefficient parameters of the double-layer resonant patch and the reflected wave in state 0, and the phase difference and reflection coefficient parameters of the double-layer resonant patch and the reflected wave in state 1.

[0092] S203. Transform the incident wave into a vertically incident circularly polarized wave to obtain the double-layer resonant patch and reflection loss parameters in state 0, and the double-layer resonant patch and reflection loss parameters in state 1.

[0093] In this embodiment, the basic concept of elevation angle is first introduced, which is the angle between the incident wave or reflected wave and the positive z-axis. Traditional inventions only study the metasurface operating at an elevation angle of 0°. However, in practical applications, the feed placement is varied, and stable operation at wide angles is necessary for most application scenarios. Currently, a few inventions specifically address metasurfaces with polarization conversion at wide angles or 1-bit metasurfaces at wide angles, but these inventions have limited angle ranges and do not simultaneously achieve the control of multiple electromagnetic wave physical properties. In contrast, the reflective electromagnetic metasurface of this invention simultaneously achieves polarization conversion and 1-bit phase control at wide angles, making it an excellent choice for relay control in communication equipment.

[0094] In this embodiment, both state units have the same elevation angle change and the same method for obtaining the physical parameters of the reflected wave under x-polarized and y-polarized incident waves.

[0095] In this embodiment, electromagnetic simulation software CST STUDIO SUITE is used for modeling and simulation. Taking a y-polarized wide-angle incident wave as an example, the resulting parameters are obtained.

[0096] In this embodiment, as Figure 5 The figure shows the co-polarization reflection loss, cross-polarization reflection loss, and phase difference of state 0 and state 1 units under different incident elevation angles. It can be seen that within the WLAN 5.8GHz (5.725-5.875GHz) operating frequency band, state 0 unit, under vertical incidence, has the lowest co-polarization reflection coefficient of 0.56 and the highest cross-polarization reflection coefficient of 0.83 at 5.725GHz, and the highest co-polarization reflection coefficient of 0.9 and the lowest cross-polarization reflection coefficient of 0.44 at 5.86GHz. The phase difference is stable within the range of -90° to -71° under different incident angles, preliminarily determining that it meets the standard of a right-hand circularly polarized reflector within the 0°-70° range. The State 1 unit exhibits the lowest co-polarization reflection coefficient of 0.57 and the highest cross-polarization reflection coefficient of 0.82 at 5.725 GHz under vertical incidence, and the highest co-polarization reflection coefficient of 0.9 and the lowest cross-polarization reflection coefficient of 0.43 at 5.84 GHz. The phase difference remains stable within the range of 88°-110° under different incident angles. It is preliminarily determined that it meets the standard of left-hand circular polarization reflector in the range of 0°-70°. However, the maximum incident elevation angle and reflection wave characteristics of the linear-circular polarization conversion of the State 0 and State 1 units still need to be calculated and verified in detail later.

[0097] In this embodiment, both state units have the same method for obtaining the physical parameters of the reflected wave under the perpendicular incidence of right-hand circularly polarized waves and left-hand circularly polarized waves. The simulation is carried out using right-hand circularly polarized incident waves as an example.

[0098] In this embodiment, as Figure 7The diagram shows the reflection loss of the unit in two states. The solid square lines represent cross-polarization reflection loss (left-hand circular polarization wave reflection loss), and the solid circular lines represent co-polarization reflection loss (right-hand circular polarization wave reflection loss). It can be seen that the unit in the 5.56-5.67 GHz range is a co-polarization reflector. At 5.56 GHz, the maximum co-polarization reflection loss of unit 0 is 1.2 dB, and at 5.67 GHz, the maximum co-polarization reflection loss of unit 1 is 0.96 dB. In the 6.29-6.5 GHz range, the unit is a cross-polarization reflector. At 6.5 GHz, units 0 and 1 have the highest cross-polarization reflection losses of 0.73 dB and 0.98 dB, respectively. Therefore, the unit exhibits low-loss characteristics during co-polarization and cross-polarization conversion. Further verification of the polarization conversion efficiency is needed.

[0099] In this embodiment, the reflection coefficients of similar magnitude and cross-polarization are achieved at a wide angle, and the phase difference meets the requirements of circularly polarized waves, verifying the wide-angle polarization conversion characteristics. Under circularly polarized incident waves, neither state unit needs adjustment, and both can achieve polarization conversion in a fixed frequency band, exhibiting extremely low reflection loss. Compared to traditional n-bit metasurfaces, it has lower loss, a wider incident angle, and more polarization conversion types.

[0100] S3. Based on the corresponding formula, further verify the maximum incident elevation angle of the 1-bit line-circular polarization conversion and calculate the efficiency of the circular-multi-circular polarization conversion.

[0101] S301. Based on Stokes' theorem, it is further verified that under linearly polarized incident wave, state 0 and state 1 units achieve the maximum incident elevation angle of linear-circular polarization conversion and maintain the maximum incident elevation angle of 1 bit phase.

[0102] S302. Substituting into the polarization conversion rate calculation formula, we obtain the polarization conversion rates of the same polarization and cross polarization of the state 0 element and the same polarization and cross polarization of the state 1 element under circularly polarized incident wave.

[0103] The metasurface unit includes an upper reflective metal patch 1, a lower perforated metal patch 2, a dielectric cylinder 3, a dielectric substrate 4, and a metal ground plane 5;

[0104] The upper reflective metal patch 1 is a square structure and is placed at the center of the metasurface. The lower perforated metal patch 2 is placed at the center of the metasurface and includes an outer double-opening annular structure and an inner regular octagonal structure. The inner regular octagon has a cross-shaped opening groove, which is rotated 45° counterclockwise and is centrally symmetrical, located at the center of the octagon. There are four dielectric cylinders 3, with their bottoms placed on the outer double-opening annular structure of the lower perforated metal patch 2 and their tops located at the four vertices of the upper reflective metal patch 1, to support the upper reflective metal patch 1. The dielectric substrate 4 and the metal ground plate 5 are both square structures, and the upper reflective metal patch 1, the lower perforated metal patch 2, and the metal ground plate 5 have the same thickness.

[0105] Table 1

[0106] Dimensions v d <![CDATA[h1]]> <![CDATA[R1]]> <![CDATA[R2]]> c <![CDATA[R3]]> a b <![CDATA[h2]]> l value / mm 10 0.4 1 6.8 5.5 0.2 5.3 1 7.95 1.6 25

[0107] In this embodiment, the multi-layer structure is as follows: Figure 3 As shown, the dielectric substrate and the dielectric cylinder 3 support are both made of FR4 (ε=4.3, μ=1, tanδ=0), and the metal patch thickness is 0.06mm. Table 1 shows the physical scale of the reflective metasurface unit.

[0108] In this embodiment, the state of a 1-bit metasurface unit is as follows: Figure 4 As shown, the uov coordinate system is obtained by rotating the xoy coordinate system counterclockwise by 45°.

[0109] (1) Taking a +y polarized electromagnetic wave incident perpendicularly as an example:

[0110] Operating State 0: The outer double-opening rings point towards the +x and +y directions. With the incident electromagnetic wave, the 1 / 4 open ring has almost no strong current. The upper reflective metal patch forms a strong current coupling with the remaining 3 / 4 open ring, with the current pointing towards the +u direction. The cross-shaped slot and the inner regular octagon form a strong capacitive-inductive circuit. This ensures equal amplitude components for the xy-polarized wave and, in conjunction with the 3 / 4 open ring, causes the current in the upper reflective metal patch to concentrate mainly at the four vertices, ultimately achieving a right-hand circularly polarized reflected wave.

[0111] Operating State 1: The outer double-opening rings point towards the +x and -y directions. With the incident electromagnetic wave, the 1 / 4 open ring has almost no strong current. The upper reflective metal patch forms a strong current coupling with the remaining 3 / 4 open ring, with the current pointing towards +v. The cross-shaped slot and the inner regular octagon form a strong capacitive-inductive circuit. This ensures equal amplitude components for the xy-polarized wave and, in conjunction with the 3 / 4 open ring, causes the current in the upper reflective metal patch to concentrate mainly at the four vertices, ultimately achieving a left-handed circularly polarized reflected wave.

[0112] Based on this, the loop formed by the cross-shaped opening slot and the inner regular octagon has completely opposite current directions in states 0 and 1, thus generating a 1-bit phase reflected circularly polarized wave. The current directions of the upper reflective metal patch and the outer double-opening ring are 90° different in states 0 and 1, thus obtaining right-hand circularly polarized reflected waves and left-hand circularly polarized reflected waves, respectively.

[0113] (2) Taking a +x polarized electromagnetic wave incident perpendicularly as an example:

[0114] Operating State 0: The outer double-opening rings point towards the +x and +y directions. With the incident electromagnetic wave, the 1 / 4 open ring has almost no strong current. The upper reflective metal patch forms a strong current coupling with the remaining 3 / 4 open ring, with the current pointing towards the -u direction. The cross-shaped slot and the inner regular octagon form a strong capacitive-inductive circuit. This ensures equal amplitude components for the xy-polarized wave and, in conjunction with the 3 / 4 open ring, causes the current in the upper reflective metal patch to concentrate mainly at the four vertices, ultimately achieving a right-hand circularly polarized reflected wave.

[0115] Operating State 1: The outer double-opening rings point towards the +x and -y directions. With the incident electromagnetic wave, the 1 / 4 open ring has almost no strong current. The upper reflective metal patch forms a strong current coupling with the remaining 3 / 4 open ring, with the current pointing towards +v. The cross-shaped slot and the inner regular octagon form a strong capacitive-inductive circuit. This ensures equal amplitude components for the xy-polarized wave and, in conjunction with the 3 / 4 open ring, causes the current in the upper reflective metal patch to concentrate mainly at the four vertices, ultimately achieving a left-handed circularly polarized reflected wave.

[0116] Based on this, the loop formed by the cross-shaped opening slot and the inner regular octagon has completely opposite current directions in states 0 and 1, thus generating a 1-bit phase reflected circularly polarized wave. The current directions of the upper reflective metal patch and the outer double-opening ring are 90° different in states 0 and 1, thus obtaining right-hand circularly polarized reflected waves and left-hand circularly polarized reflected waves, respectively.

[0117] In this embodiment, Stokes' formula is introduced to calculate the axial ratio and normalized ellipticity, as follows:

[0118] I = |r x | 2 +|r y | 2 ;

[0119] Q = |r x | 2 -|r y | 2 ;

[0120]

[0121] Wherein, I, Q, U, and V describe the total reflected wave amplitude, the amplitude difference between the x-polarized and y-polarized reflected waves, the difference in polarization in the ±45° direction, and the state of circular polarization, respectively. x r y This is the reflection coefficient.

[0122] Therefore, the formula for calculating the shaft ratio is:

[0123]

[0124] When the axial ratio is less than 3dB, the reflected wave is a circularly polarized wave.

[0125] The normalized ellipticity is introduced to further verify the polarization type of the reflected circularly polarized wave. A normalized ellipticity approximately -1 represents a right-handed circularly polarized wave; approximately +1 represents a left-handed circularly polarized wave. The formula is as follows:

[0126]

[0127] In this embodiment, Figure 7 The axial ratio and normalized ellipticity are shown for different states. When the cell is operating in the WLAN 5.8GHz band, the maximum axial ratio of state 0 cell is 2.63dB, the incident angle is as high as 60°, and the normalized ellipticity is between -1 and 0.84, realizing a right-hand circularly polarized reflector. State 1 cell also has an axial ratio of less than 2.75dB at an incident angle of 60°, and the normalized ellipticity is in the range of 0.83-1, realizing a left-hand circularly polarized reflector. Therefore, the wide angle for the metasurface to achieve linear-circular polarization conversion is between 0° and 60°.

[0128] In this embodiment, Figure 8 The loss and phase difference of the circularly polarized reflected wave are shown in different states. At incident angles of 0°-60°, the reflection loss of the right-hand circularly polarized wave in state 0 is less than 0.36dB, and the reflection loss of the left-hand circularly polarized wave in state 1 is less than 0.39dB. Therefore, the loss is extremely low during the conversion of the incident wave into a circularly polarized reflected wave, and almost all the beams are converted and reflected. Simultaneously, the phase difference of the circularly polarized reflected wave is located between 177°-182° at most elevation angles. At an incident angle of 50°, the phase difference shifts slightly by 180°, but still remains between 170°-174°, with a fluctuation range of less than 10°. Therefore, the 0°-60° cells possess a high-performance 1-bit low-loss circularly polarized reflected wave, and also possess dual-circularly polarized reflected waves.

[0129] When the incident wave is a circularly polarized wave, the formulas for the same polarization conversion rate and cross-polarization conversion rate are:

[0130]

[0131]

[0132] Where co and cross represent co-polarization and cross-polarization, respectively, and r co The reflection coefficient, r, represents the reflection coefficient of a co-polarized (e.g., a right-hand circularly polarized incident wave converted to a right-hand circularly polarized reflected wave) wave. cross This represents the reflection coefficient for cross-polarization (e.g., converting a right-hand circularly polarized incident wave into a left-hand circularly polarized reflected wave).

[0133] (1) Taking a right-hand circularly polarized electromagnetic wave incident perpendicularly as an example:

[0134] Operating State 0: The outer double-opening ring points towards the +x and +y directions. For same-polarity conversion, the upper reflective metal patch forms a strong current coupling with the outer double-opening ring, with the current pointing towards the -u direction. The phase increments of the current distribution in the cross-shaped opening slot cancel each other out, and the inner octagonal current points towards the -x direction. Ultimately, the y-direction wave phase is 315°, and the x-direction wave phase is 405°, reflecting a right-hand circularly polarized wave. For cross-polarity conversion, the current in the upper reflective metal patch points towards the +x direction, the current in the outer double-opening ring deviates from this direction (counterclockwise) by 20°, the inner octagonal current points towards the -y direction, and the cross-shaped opening slot current is distributed along a single arm, canceling out the phase increments. Ultimately, the y-direction wave phase is 430°, and the x-direction wave phase is 340°, reflecting a left-hand circularly polarized wave.

[0135] Operating State 1: The outer double-opening ring points towards the +x and -y directions. For same-polarity conversion, the upper reflective metal patch and the outer double-opening ring form strong current coupling, with the current pointing towards the +v direction. The phase increments of the current distribution in the cross-shaped opening slot cancel each other out, while the current in the inner octagon points towards the +y direction. Ultimately, the phase of the wave in the y direction is 135°, and the phase of the wave in the x direction is 225°, reflecting a right-hand circularly polarized wave. For cross-polarity conversion, the current in the upper reflective metal patch points towards the -x direction, the current in the outer double-opening ring deviates from this direction by -20°, the current in the inner octagon points towards the -y direction, and the current in the cross-shaped opening slot is distributed along a single arm, canceling out the phase increments. Ultimately, the phase of the wave in the y direction is 830°, and the phase of the wave in the x direction is 740°, reflecting a left-hand circularly polarized wave.

[0136] (2) Taking a vertically incident left-hand circularly polarized electromagnetic wave as an example:

[0137] Operating State 0: The outer double-opening rings point towards the +x and +y directions. For same-polarity conversion, the upper reflective metal patch forms two loops, one above the other, with a 20° deviation from the +x axis as the boundary. These loops point towards the -x direction. The current in the outer double-opening rings points towards the +u direction, while the inner octagon forms two loops, one on the left and one on the right, with the loops along the +y direction. The phase increments of the current distribution in the cross-shaped slot cancel each other out. Ultimately, the y-direction wave has a phase of 0°, and the x-direction wave has a phase of 270°, reflecting a left-handed circularly polarized wave. For cross-polarity conversion, the upper reflective metal patch and the outer double-opening rings form a strong current coupling, with the current pointing towards the +x direction. The current in the inner octagon flows along the -y direction, and the current in the cross-shaped slot is distributed along a single arm. The phase increments cancel each other out, resulting in a y-direction wave phase of 90° and an x-direction wave phase of 180°, reflecting a right-handed circularly polarized wave.

[0138] Operating State 1: The outer double-opening rings point towards the +x and -y directions. For same-polarity conversion, the upper reflective metal patch forms two loops, one above the other, with a 20° deviation from the +y axis as the boundary. The loops point towards the +y direction. The current in the outer double-opening rings points towards the -v direction. The inner octagon forms two loops, one on the left and one on the right, with the x-axis as the boundary. The loops are along the +x direction, and the phase increments of the current distribution in the cross-shaped slot cancel each other out. The final y-direction wave phase is 315°, and the x-direction wave phase is 225°, reflecting a left-handed circularly polarized wave. For cross-polarity conversion, the upper reflective metal patch and the outer double-opening rings form a strong current coupling, with the current pointing towards the +x direction. The current in the inner octagon flows along the +y direction, and the current distribution in the cross-shaped slot is distributed along a single arm. The phase increments cancel each other out, and the final y-direction wave phase is 360°, and the x-direction wave phase is 270°, reflecting a right-handed circularly polarized wave.

[0139] In this embodiment, Figure 9 The same-polarization slew rate and cross-polarization slew rate of the unit in state 0 and state 1 were calculated. In the 5.56-5.67 GHz range, the same-polarization slew rate of the unit in state 0 is between 0.76 and 1, while the cross-polarization slew rate is between 0.84 and 0.97 in the 6.29-6.5 GHz range. In the same frequency band, the same-polarization slew rate of the unit in state 1 is between 0.8 and 1, and the cross-polarization slew rate is greater than 0.8. It can be seen that in both states, the metasurface can achieve highly efficient reflection of multiple circularly polarized waves in different frequency bands. Traditional inventions mainly focus on a single circular polarization or multiple circular polarizations within the same frequency band; this invention demonstrates a polarization conversion capability not possessed by the aforementioned methods.

[0140] S4. Construct an 8×8 small metasurface to verify the results. Select a suitable linearly polarized feed source, calculate the unit compensation phase value, assign the unit initial state, and then further optimize the unit state through the Matlab algorithm program to complete the three-dimensional spatial electromagnetic wave beam control. Next, adjust the feed source incident angle to complete the angular reciprocity verification of the metasurface. Replace the linearly polarized feed source with a circularly polarized feed source to obtain the far-field gain of the cross-polarized and co-polarized reflection fields.

[0141] S401, construct an 8×8 metasurface, select a linearly polarized feed, the feed is located in the far field region, and the incident wave elevation angle is 0°;

[0142] S402. The compensation angle at different positions is determined by the phase compensation formula. After the initial unit state is obtained, the metasurface state is automatically iterated by the Matlab optimization algorithm to complete the beam control at any angle in three-dimensional space and confirm the maximum beam control elevation angle.

[0143] S403. Keep the distance between the feed center and the metasurface array center constant, adjust the feed incident angle, and obtain the beam pointing angle of the metasurface under different incident angles under the same encoding condition to verify the angle reciprocity.

[0144] S404. Construct 8×8 metasurfaces for state 0 and state 1 elements respectively. Select circularly polarized feed sources and place the feed sources in the far field region. Simulate and obtain the far field gain of right-hand circularly polarized and left-hand circularly polarized metasurface of state 0, and the far field gain of right-hand circularly polarized and left-hand circularly polarized metasurface of state 1.

[0145] In this embodiment, the array state is obtained based on the phase compensation formula and the automatic iterative algorithm. The phase compensation formula is as follows:

[0146]

[0147] Where k0 is the beam size. m and n are the number of rows and columns of the cells in the array, and l is the side length of a single square cell. The location of the unit is described. x, y, and z describe the relative position of the feed in the spatial coordinate system. θ and σ are the beam control elevation angle and horizontal azimuth angle, respectively.

[0148] After obtaining the initial cell state, automatic optimization is performed using a Matlab algorithm. This invention considers the coupling effect of cells in different states, avoiding inaccurate and incomplete results caused by ignoring the coupling effect. Optimization is performed one by one, executed multiple times until the far-field gain stabilizes. First, the far-field value and cell state are obtained under the initial state. The "0" and "1" states of cells are changed one by one. If the far-field value increases after the change, the changed cell state is retained, and the new far-field value is used as a comparison value; if the far-field value remains unchanged or decreases, the original state is returned. This optimization method is fully automated, requires no manual intervention, and has low time cost. Compared with inventions that only perform phase compensation to achieve beam control, it has higher accuracy, is more suitable for complex application environments, and has greater adaptability.

[0149] In this embodiment, the combined 8×8 metasurface selector horn antenna is used as the feed source. The waveguide port of the horn antenna is WR-159 and is placed vertically 5.5λ above the center of the array to generate y-polarized waves.

[0150] Array far-field modulation results are as follows Figure 10 As shown, the array center operating frequency is selected as 5.8 GHz. The beam steering pointing angles are (0°, 0°), (20°, 30°), (30°, 90°), and (45°, 0°), with corresponding gains of 15.76 dBi, 15.05 dBi, 13.68 dBi, and 12.94 dBi, respectively. The figure shows that even at a 45° elevation angle, the sidelobe gain is still much smaller than the main lobe gain at the target angle. Therefore, this 8×8 small array exhibits excellent beam steering characteristics between 0° and 45°. As the steering angle increases, the sidelobes increase slightly; increasing the number of array elements can compensate for this deficiency and further expand the beam steering angle.

[0151] In this embodiment, the concept of angle reciprocity is introduced. Angle reciprocity refers to the phenomenon that, under the same metasurface conditions, when the incident wave angle is replaced by the reflected wave angle, the reflected wave points in the original incident wave direction. To simulate an oblique incidence scenario, the radius from the feed source to the center of the metasurface is taken as the distance along... The circular curve in the plane rotates to simulate the change of the oblique incidence angle θ.

[0152] like Figure 11 The figure shows the reciprocity results of the metasurface after taking any two angles. When the incident angle is changed from (0°, 0°) to (45°, 0°), the reflection angle of the metasurface in the same state changes from (45°, 0°) to (0°, 0°); when the incident angle is changed from (0°, 0°) to (17°, 180°), the reflection angle of the metasurface in the same state changes from (17°, 180°) to (0°, 0°). Therefore, the metasurface has excellent angle reciprocity. At the same time, the design of this metasurface mainly considers the current large-scale application frequency band WLAN 5.8GHz, which further increases the reliability of the metasurface in the field of communication.

[0153] In this embodiment, the method for achieving beam control and angle reciprocity of the x-polarized incident wave is the same as above.

[0154] This embodiment achieves beam control of a small array. Based on the low-loss characteristics and stable 1-bit phase characteristics of the 1-bit circularly polarized reflected wave, the array control angle is wider than that of an array of the same number, further enhancing the integrability of metasurfaces as relay devices. Furthermore, this invention solves the angle reciprocity problem through the wide-angle characteristics of metasurfaces and their ability to generate 1-bit phase difference beams. This is an area not addressed in most inventions and is of great significance for optimizing the performance and improving the efficiency of communication systems.

[0155] In this embodiment, the size of the circularly polarized patch antenna is reasonably adjusted so that its operating frequency band includes the metasurface cross-polarization conversion and co-polarization conversion frequency bands. The circularly polarized patch antenna is placed at the exact center 5λ of the metasurface to generate a right-hand circularly polarized wave.

[0156] like Figure 12As shown, taking the operating frequencies of the same-polarization and cross-polarization centers as examples, the metasurface achieves same-polarization conversion at 5.62 GHz. In states 0 and 1, the metasurface reflects right-hand circularly polarized waves with gains of 7.27 dBi and 8.82 dBi, respectively, and reflects left-hand circularly polarized waves with gains of 0.76 dBi and -0.83 dBi, respectively. At 6.4 GHz, the metasurface achieves cross-polarization conversion. In states 0 and 1, the metasurface reflects right-hand circularly polarized waves with gains of 0.53 dBi and 0.34 dBi, respectively, and reflects left-hand circularly polarized waves with gains of 8.41 dBi and 8.46 dBi, respectively. The metasurface simulation results are consistent with the element reflection loss conclusion, namely, achieving a same-polarization reflector in the 5.56-5.67 GHz range and a cross-polarization reflector in the 6.29-6.5 GHz range.

[0157] In this embodiment, the method for achieving same polarization conversion and cross-polarization conversion of the left-hand circularly polarized incident wave is the same as above.

[0158] Currently, common inventions focus only on a single circular polarization or multiple circular polarizations within the same frequency band. In this embodiment, to address the problem of limited communication resources, mirror symmetry is used to ensure that the two-state metasurface can reflect right-handed and left-handed circularly polarized waves at different frequency bands. This expands the available electromagnetic wave resources for communication from both the spectrum and polarization dimensions, while also reducing multipath effects and ensuring stability during propagation.

[0159] On the other hand, this embodiment also provides an electronic device, including a memory, a processor, and a computing program stored in the memory and executable on the processor, wherein the processor implements the method when executing the computing program.

[0160] On the other hand, this embodiment also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the method.

[0161] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A multi-polarization conversion reflection method based on a 1-bit electromagnetic metasurface, characterized in that, include: The target frequency band was determined and a two-dimensional double-layer microstrip structure was constructed accordingly. Based on transmission line theory, electromagnetic coupling effect and equivalent circuit theory, a double-layer resonant structure consisting of an upper square resonant patch and a lower aperture resonant patch was designed. By performing x-axis mirror symmetry on the double-layer resonant structure, two mirror-image unit structures are obtained, which serve as state 0 and state 1 of the 1-bit metasurface. Electromagnetic simulations were performed on the state 0 and state 1 units respectively to obtain the phase, amplitude and polarization conversion parameters of the reflected waves under different incident polarization waves and different elevation angles. Based on the simulation results, an 8×8 small metasurface array was constructed to verify the results. Three-dimensional beam control was achieved through phase compensation and state coding, and its angle reciprocity was verified. The 8×8 small metasurface array is excited by linearly polarized feed and circularly polarized feed respectively to obtain the far-field gain distribution and realize the multi-polarization conversion reflection function. The lower-layer perforated resonant patch includes an outer double-opening ring and an inner regular octagon; The structure of the lower-layer open-hole resonant patch includes: The outer double-opening ring structure has its opening direction aligned with the x-axis or y-axis. It has an inner regular octagonal structure with a cross-shaped opening slot rotated 45° in the center, which is used to adjust the polarization state of the reflected wave. The outer double-opening ring and the inner regular octagon jointly adjust the phase and amplitude of the reflected wave through electromagnetic coupling; The construction of the 8×8 small metasurface array includes: Arrange the state 0 and state 1 units into an 8×8 array according to the preset encoding rules; The compensation phase of each element is calculated using the phase compensation formula, and the element state is iteratively adjusted using a Matlab optimization algorithm to achieve the target beam pointing.

2. The method according to claim 1, characterized in that, The process of determining the target frequency band and constructing a two-dimensional dual-layer microstrip structure includes: Select the operating frequency band based on the application scenario, and determine the side length of the microstrip structure by combining the wavelength calculation formula; The microstrip structure is designed as a reflective structure consisting of a double-layer metal patch and a dielectric substrate. The double-layer metal patch includes an upper square resonant patch and a lower open-hole resonant patch.

3. The method according to claim 1, characterized in that, The mirror symmetry operation is used to generate state 1 unit, including: mirror symmetrically flipping state 0 unit along the x-axis, so that the opening direction of the outer double-opening ring changes from +x / +y to +x / −y, completing the introduction of a 180° phase difference and realizing 1-bit encoding.

4. The method according to claim 1, characterized in that, The electromagnetic simulation includes: For linearly polarized incident waves, scan their elevation angle changes to obtain the reflection coefficients and phase differences of circularly polarized reflected waves under x-polarization and y-polarization for state 0 and state 1 elements. For a circularly polarized incident wave, obtain the reflection loss and co-polarization / cross-polarization conversion parameters of the state 0 and state 1 elements under vertical incidence.

5. The method according to claim 1, characterized in that, The three-dimensional beam manipulation includes: With a linearly polarized feed incident vertically, beam deflection within the elevation angle range of 0°–45° is achieved by adjusting the unit state coding; Record the far-field gain distribution under different deflection angles to verify the correspondence between beam pointing and cell state.

6. The method according to claim 1, characterized in that, The verification of the angle reciprocity includes: Keeping the relative positions of the feed and the array unchanged, adjust the feed incident elevation angle and detect whether the reflected wave points to the original incident direction; Record the reciprocal correspondence between the angle of incidence and the angle of reflection when the state code remains unchanged.

7. An electronic device comprising a memory, a processor, and a computing program stored in the memory and executable on the processor, characterized in that, When the processor executes the computing program, it implements the method of any one of claims 1-6.

8. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by a processor, it implements the method of any one of claims 1-6.

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