A double-layer symmetric meander cross metamaterial unit and high-gain wide-beam metamaterial reflector antenna

Abstract

This invention provides a double-layer symmetrical cross-shaped metasurface element and a high-gain wide-beam metasurface reflective antenna. The antenna includes a conical horn feed and a reflective array, the reflective array being composed of multiple reflective metasurface elements. The metasurface elements employ a symmetrical double-layer cross-shaped metal patch structure with an air gap between the two patches. Continuous modulation of the reflected phase of the incident electromagnetic wave is achieved through electromagnetic coupling between the multi-layer structure. The reflective array is designed with phase compensation based on the spatial phase distribution of the feed antenna, converting the reflected wave from a spherical wave to a quasi-plane wave, thereby achieving directional radiation and extending the beam coverage. This invention features a compact structure, low loss, and can achieve synergistic optimization of high directional radiation and a wide beam under limited aperture conditions, making it suitable for applications such as emergency communications.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic wave modulation and antenna technology, and particularly relates to a double-layer symmetrical cross-shaped metasurface unit and a high-gain wide-beam metasurface reflective antenna. Background Technology

[0002] In complex environments such as emergency communications, stable and reliable wireless communication links are essential. Traditional communication systems often employ omnidirectional or wide-beam antennas, which have low gain and limited communication range; furthermore, their energy is dispersed, making it difficult to achieve directional coverage. To improve communication range, high-gain directional antennas, such as parabolic antennas or microstrip array antennas, are typically used. However, parabolic antennas are bulky and inconvenient to deploy; microstrip array antennas have complex structures, high costs, and narrow beamwidths. In practical applications, high-gain antennas are often accompanied by the problem of excessively narrow beams, and in dynamic environments, pointing deviations can easily lead to a decrease in communication performance, creating a technical contradiction of "difficulty in balancing gain and beamwidth." Therefore, there is an urgent need for an antenna structure that combines high gain and a moderate beamwidth within a limited aperture.

[0003] In recent years, metasurfaces, as artificial two-dimensional periodic / aperiodic structures, have provided new ideas for antenna design. They can control the phase and amplitude of electromagnetic waves through subwavelength-scale unit structures, theoretically enabling high-gain beamforming on planar structures. However, existing metasurface antenna research largely focuses on transmission-type or transmission-reflection integrated designs. For purely reflective metasurface antennas, especially those excited by horn feeds, challenges remain in engineering applications: 1) How to achieve efficient feed-metasurface coupling and reduce feed obstruction and spillover losses; 2) How to optimize unit arrangement within a limited aperture to achieve synergistic optimization of radiation gain and beamwidth to adapt to dynamic application scenarios; 3) How to ensure stable radiation performance and sufficient operating bandwidth within the target frequency band. Therefore, there is an urgent need for a dedicated antenna that balances high gain, moderate beamwidth, compact structure, portability, and stable performance to fundamentally improve the reliability and communication range of emergency communication systems in complex disaster environments. Summary of the Invention

[0004] Purpose of the invention: The technical problem to be solved by the present invention is to address the shortcomings of the prior art by providing a double-layer symmetrical cross-shaped metasurface element and a high-gain wide-beam metasurface reflector antenna.

[0005] The present invention first provides a double-layer symmetrical cross-shaped metasurface unit, which adopts a symmetrical multi-layer stacked architecture. Along the Z-axis perpendicular to the unit plane, from top to bottom, there are an upper metal patch layer, a first dielectric substrate layer, an air gap layer, a lower metal patch layer, a second dielectric substrate layer, and a metal ground layer.

[0006] The upper and lower metal patch layers have the same structure, both being centrally symmetrical structures composed of cross-shaped main ribs and meander extension structures at the ends; by adjusting the geometric parameters of the meander extension structures, continuous control of the reflection phase within the target frequency band can be achieved.

[0007] Both the upper and lower metal patch layers are centrally symmetrical cross-shaped metal patches, and the metal material is copper.

[0008] Both the upper and lower metal patch layers are located within the square unit period and are composed of metal lines of equal width. The core is a cross-shaped metal main rib running through the center of the unit. The cross-shaped metal main rib divides the unit plane into four rectangular hollow areas of equal size. The four ends of the cross-shaped metal main rib extend outwards with meandering extension structures, forming a composite structure with the cross as the skeleton and the meandering as the wings. The upper and lower metal patch layers simultaneously satisfy 180° central symmetry, and all line corners are 90° right angles. The width of the metal lines is w.

[0009] The herringbone extension structure includes a herringbone extension arm and a herringbone inner arm. The length of the herringbone extension arm is L2, and the length of the herringbone inner arm is L3. L2 is an adjustable parameter used to adjust the reflection phase characteristics, and L3 is used to determine the basic geometric shape of the herringbone structure.

[0010] Both the first dielectric substrate layer and the second dielectric substrate layer are square flat plate structures with side lengths consistent with the cell period and a thickness of H_sub, and are made of low dielectric loss material.

[0011] The first dielectric substrate layer is bonded to the lower surface of the upper metal patch layer, and the second dielectric substrate layer is bonded between the lower surface of the lower metal patch layer and the upper surface of the metal ground layer.

[0012] The air spacer layer is a square cavity structure with a side length consistent with the unit period and a thickness of H_air. It is sandwiched between the first dielectric substrate layer and the lower metal patch layer to form an air resonant cavity structure.

[0013] The metal floor layer is a complete square copper plate with a side length consistent with the unit period and a thickness of h.

[0014] The present invention also provides a high-gain wide-beam metasurface reflective antenna based on the double-layer symmetrical cross metasurface unit, including a conical horn feed and a reflective array;

[0015] The reflective array is composed of two or more metasurface units arranged in an aperiodic phase-compensated distribution.

[0016] Within the operating frequency band, the reflective array is designed with phase compensation based on the spatial phase distribution of the conical horn feed source, so that the reflected wave is converted from a spherical wave to a quasi-plane wave, enabling the antenna to form a directional radiation main lobe, and expanding the beam coverage range while ensuring concentrated energy radiation, while effectively suppressing the sidelobe level.

[0017] The reflective array is designed through the following steps:

[0018] Step 1: Design metasurface units and determine the correspondence between the geometric parameters of the metasurface units and the reflection phase;

[0019] Step 2: Construct a reflective array consisting of two or more metasurface units in an aperiodic arrangement.

[0020] Step 3: Select a feed antenna to excite the reflective array;

[0021] Step 4: Determine the array layout parameters based on the feed characteristics and the size of the reflective array;

[0022] Step 5: Position the feed antenna at the focal point corresponding to the reflector array;

[0023] Step 6: Obtain the near-field phase distribution of the feed antenna in the aperture plane of the reflector array;

[0024] Step 7: Calculate the compensation phase distribution required for the reflective array based on the near-field phase distribution;

[0025] Step 8: Based on the correspondence between geometric parameters and reflection phase, convert the compensation phase distribution into the geometric parameters of each metasurface unit;

[0026] Step 9: Arrange the reflection array according to the geometric parameters of each unit;

[0027] Step 10: Complete the design and construction of the reflective array, and form a high-gain wide-beam metasurface reflective antenna.

[0028] Beneficial effects: (1) Wide-range phase modulation with ultra-low loss: The present invention adopts a multi-layer architecture of "double-layer symmetrical cross-shaped metal patch + double-layer low-loss dielectric substrate (Rogers5880 in the embodiment) + air gap cavity". Within the target operating frequency band, a wide range of continuous coverage of the reflection phase can be achieved by adjusting the geometric parameters of the cross-shaped extension structure. In this embodiment, the reflection amplitude is higher than -0.2dB in the entire phase range (reflection efficiency >95.5%). Compared with existing metasurface units (the amplitude fluctuation is usually around -1dB), the amplitude fluctuation of the present invention is extremely low, which significantly reduces the array radiation loss and provides key support for achieving high gain in small aperture.

[0029] (2) Synergistic Breakthrough of High Gain and Wide Beamwidth in Compact Aperture: In a compact aperture of 450mm×450mm, the present invention exhibits high radiation gain and moderate beamwidth in the embodiments. Compared with traditional high-gain antennas (beamwidth is usually <6° under the same aperture), the present invention effectively solves the contradiction between "gain and beamwidth", and can significantly reduce the risk of link interruption caused by antenna pointing deviation in dynamic emergency communication scenarios. The present invention achieves synergistic output of wide beamwidth and high gain without increasing the complexity of the feed network through structural symmetry and air cavity coupling design. This technical effect cannot be obtained by existing technologies through simple structural replacement or parameter adjustment. Attached Figure Description

[0030] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0031] Figure 1 This is a schematic diagram of the metasurface unit structure of the present invention.

[0032] Figure 2 This is a schematic diagram of the metasurface unit reflection phase curves corresponding to different helical extension arm lengths L2 at 3.5 GHz.

[0033] Figure 3 These are the metasurface unit reflection amplitude curves corresponding to different helical extension arm lengths L2 at 3.5 GHz.

[0034] Figure 4 This is a flowchart of metasurface array design.

[0035] Figure 5 This is a schematic diagram of the near-field phase of the feed antenna.

[0036] Figure 6 This is a schematic diagram of the near-field amplitude of the feed antenna.

[0037] Figure 7 This is a schematic diagram of the overall structure of the reflector array antenna.

[0038] Figure 8 It is a two-dimensional polar coordinate pattern.

[0039] Figure 9 It is a three-dimensional far-field gain pattern. Detailed Implementation

[0040] This invention provides a reflective metasurface unit operating in the 2GHz~5GHz frequency band and designed with a target frequency of 3.5GHz, such as... Figure 1As shown, a symmetrical multilayer stacked architecture is adopted, and the following layers are stacked sequentially from top to bottom along the Z-axis direction perpendicular to the unit plane: upper metal patch layer, first dielectric substrate layer, air gap layer, lower metal patch layer, second dielectric substrate layer, and metal ground plane layer. Figure 1 In the diagram, L1, L2, L3, and W are structural dimension parameters, p is the periodic side length, H_sub represents the dielectric substrate thickness, H_air represents the air gap layer thickness, and h represents the metal thickness.

[0041] The upper and lower metal patch layers have identical geometric structures and dimensional parameters, and the first and second dielectric substrate layers have identical materials, thicknesses, and dimensional parameters. The overall structure possesses central symmetry, enabling efficient and stable control of incident electromagnetic waves, providing a core phase control unit for high-gain, wide-beam metasurface antennas. The core of this invention lies in the multi-layer coupling structure formed by a double-layer symmetrical cross-shaped metal patch layer and an air-spaced cavity, achieving low-loss full-phase control. Specifically:

[0042] Both the upper and lower metal patch layers are centrally symmetrical cross-shaped metal patches, and the metal material used is copper. The entire structure is located within a square unit period and is composed of copper lines of equal width. The core is a cross-shaped copper main rib running through the center of the unit. The cross structure divides the unit plane into four rectangular hollow areas of equal size. The four ends of the cross main rib extend outwards with a meandering extension structure, forming a composite structure of "cross as the skeleton and meandering as the wings". The patch structure also satisfies 180° central symmetry, all line corners are 90° right angles, and the width of the metal lines is w. The length of L2 in the meandering extension structure is an adjustable parameter. The other structural dimensions can be determined by electromagnetic simulation in combination with the target operating frequency band and radiation performance requirements. The meandering extension structure changes the current path distribution by changing its geometric parameters, thereby introducing a multimode resonant coupling effect and realizing continuous control of the reflected phase of the incident electromagnetic wave. The meander extension structure includes a meander extension arm length L2 and a meander inner arm length L3, where L2 is an adjustable parameter used to adjust the reflection phase characteristics, and L3 is used to determine the basic geometric shape of the meander structure.

[0043] Both dielectric substrate layers (first / second) are square flat plate structures with side lengths consistent with the cell period and a thickness of H_sub. They employ low dielectric loss materials, such as Rogers 5880 dielectric material, with a dielectric constant of [missing value]. With a loss tangent tanδ=0.0009, it possesses excellent low dielectric loss and stable characteristics. The first dielectric substrate layer is bonded to the lower surface of the upper metal patch layer, and the second dielectric substrate layer is bonded between the lower surface of the lower metal patch layer and the upper surface of the metal ground layer, which can effectively support the metal patch and reduce electromagnetic wave transmission loss.

[0044] The air spacer layer is a square cavity structure with a side length consistent with the cell period and a thickness of H_air. It is sandwiched between the first dielectric substrate layer and the lower metal patch layer to form an air resonant cavity structure. The low dielectric loss of the air dielectric reduces the overall loss of the cell and simultaneously modulates the equivalent impedance matching characteristics of the resonant structure.

[0045] The metal ground plane is a complete square copper plate with a side length consistent with the unit period and a thickness of h. Serving as the reflective ground of the reflective metasurface, it completely blocks electromagnetic wave transmission, enabling total internal reflection electromagnetic wave modulation and ensuring the high-gain radiation performance of the metasurface antenna. The use of copper further reduces ohmic loss and improves the electromagnetic modulation efficiency of the unit. The specific structural parameters of this metasurface unit are shown in Table 1.

[0046] Table 1. Structural parameters of reflective metasurface units

[0047]

[0048] Figure 2 , Figure 3 The figures show the reflection phase and amplitude curves for different ribbed extension arm lengths L2. This metasurface element achieves excellent electromagnetic control performance at the target operating frequency of 3.5 GHz through parameter scanning design with adjustable structural parameters: by adjusting the geometric parameters of the ribbed extension arm to change the electromagnetic coupling relationship within the element, it forms a continuously changing equivalent resonant state in the target frequency band, thereby achieving full-range continuous coverage of the reflection phase and meeting the phase compensation design requirements of the reflective metasurface antenna. Arbitrary wavefront control can be achieved through element combinations with different parameter values, providing a core phase control basis for high-gain wide-beam radiation. In the simulation results of this embodiment, the reflection amplitude of the element corresponding to the full phase range remains above -0.2 dB, with small amplitude fluctuations, effectively reducing the radiation loss of the metasurface antenna. The composite structure of the double-layer symmetrical ribbed cross metal patch and the air spacer layer achieves full-phase coverage while possessing excellent polarization stability and wideband characteristics, effectively extending the 3 dB beamwidth of the metasurface antenna and realizing the synergistic optimization of high gain and wide beam. The phase modulation mechanism relies on the coupling effect between multilayer structures, which is different from the existing technology that achieves phase change by adjusting the size of a single layer structure.

[0049] like Figure 4 As shown, this embodiment of the invention also provides a design method for a reflective array based on the aforementioned metasurface unit, including steps such as obtaining the feed phase distribution, calculating the phase compensation distribution, and establishing a mapping relationship between unit parameters and the reflection phase. The design method, by spatially distributing and controlling the reflection phase, transforms the reflected wavefront from a spherical wave to a quasi-plane wave, thereby increasing radiation gain while expanding beam coverage, achieving synergistic optimization of gain and beamwidth.

[0050] Combining the metasurface units designed above, an 18×18 metasurface array is constructed, using a conical horn as the feed source. This conical horn feed source provides a gain of 12dBi at the center frequency of 3.5GHz, with a 3dB beamwidth of 50°. Based on the reflection phase curves of the metasurface units, a mapping relationship between unit geometric parameters and reflection phase is established. Based on the near-field phase distribution of the horn feed source, the compensation phase distribution matrix required for the reflection array is calculated. According to the phase-parameter mapping relationship, the phase distribution matrix is ​​converted into the specific geometric dimensions corresponding to each metasurface unit, thus completing the design and construction of the entire aperiodic metasurface reflection array. Figure 4 The diagram shown is a flowchart of the design process for a metasurface array.

[0051] Figure 5 and Figure 6 The phase and amplitude distributions extracted at the center frequency of 3.5 GHz in the near-field region directly in front of the designed metasurface array (450 mm × 450 mm aperture) are shown. A standard gain horn feed is used, positioned at the focal point of the array (focal length F = 350 mm). Analysis reveals that the near-field phase distribution shows a centrally symmetrical spherical wave distribution incident on the array surface, forming a regular concentric ring-shaped isophase profile with the array center as the origin. The phase changes continuously radially, with no abrupt phase changes across the entire array, providing a stable reference for the phase compensation design of the metasurface. Simultaneously, the corresponding amplitude distribution exhibits a tapered characteristic, strong at the center and smoothly decreasing at the edges. This beneficial amplitude gradient helps suppress far-field sidelobes and improve radiation efficiency. The phase and amplitude distributions demonstrate that the structure can achieve stable phase compensation and energy distribution.

[0052] Figure 7 , Figure 8 and Figure 9 This paper demonstrates specific embodiments of the reflective metasurface antenna described in this invention and its key performance characteristics. Figure 7 A schematic diagram of the overall structure of the antenna is provided, which intuitively presents the compact reflector system architecture consisting of a horn feed, a metasurface reflector array (with an aperture of 450mm×450mm) and an air gap layer. Its physical layout is the basis for realizing subsequent electrical performance.

[0053] Figure 8The far-field radiation results shown demonstrate that the present invention can achieve high gain and moderate beamwidth under limited aperture conditions. The two-dimensional polar pattern (3.5 GHz, Phi=90° plane) reflects the antenna's radiation characteristics: directional radiation is formed in the normal direction with concentrated radiated energy, while sidelobes are effectively suppressed, indicating that the wavefront modulation mechanism based on phase compensation can achieve good directional radiation. Simulation results further show that the structure can still achieve high radiation gain and wide beam coverage under limited aperture conditions, demonstrating that the multi-layer coupling mechanism can achieve synergistic optimization of directional energy concentration and beamwidth without relying on complex feed networks, thereby overcoming the technical problem of excessively narrow beams in traditional high-gain antennas.

[0054] Figure 9 The three-dimensional far-field gain pattern provides intuitive evidence from a spatial perspective. For example... Figure 9 As shown, the radiated energy is highly concentrated in the forward direction, forming a symmetrical, sharp main lobe, and the spatial radiation level outside the main lobe decays rapidly. This indicates that the antenna has high directivity, high radiation purity, and excellent spatial anti-interference capability, ensuring that energy can be efficiently and stably directed towards the target in complex multipath environments.

[0055] In conclusion, Figure 7 , Figure 8 and Figure 9 This demonstrates that the antenna of the present invention possesses excellent radiation performance and spatial energy distribution characteristics. The phase compensation mechanism converts the electromagnetic wave from a spherical wave to a quasi-plane wave, thereby achieving a directional and concentrated energy distribution in space. Simulation results show that the antenna has high gain and wide beam characteristics, providing a technical foundation for long-distance communication.

[0056] This invention provides a double-layer symmetrical cross-shaped metasurface element and a high-gain wide-beam metasurface reflector antenna. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. A double-layer symmetrical cross-shaped metasurface unit, characterized in that, The structure adopts a symmetrical multilayer stacked architecture, with the upper metal patch layer, the first dielectric substrate layer, the air gap layer, the lower metal patch layer, the second dielectric substrate layer and the metal ground layer arranged from top to bottom along the Z-axis perpendicular to the cell plane. The upper and lower metal patch layers have the same structure, both being centrally symmetrical structures composed of cross-shaped main ribs and meander extension structures at the ends; by adjusting the geometric parameters of the meander extension structures, continuous control of the reflection phase within the target frequency band can be achieved.

2. The double-layer symmetrical cross-shaped metasurface unit according to claim 1, characterized in that, Both the upper and lower metal patch layers are centrally symmetrical cross-shaped metal patches, and the metal material is copper.

3. The double-layer symmetrical cross-shaped metasurface unit according to claim 2, characterized in that, Both the upper and lower metal patch layers are located within the square unit period and are composed of metal lines of equal width. The core is a cross-shaped metal main rib running through the center of the unit. The cross-shaped metal main rib divides the unit plane into four rectangular hollow areas of equal size. The four ends of the cross-shaped metal main rib extend outwards with meandering extension structures, forming a composite structure with the cross as the skeleton and the meandering as the wings. The upper and lower metal patch layers simultaneously satisfy 180° central symmetry, and all line corners are 90° right angles. The width of the metal lines is w.

4. The double-layer symmetrical cross-shaped metasurface unit according to claim 3, characterized in that, The herringbone extension structure includes a herringbone extension arm and a herringbone inner arm. The length of the herringbone extension arm is L2, and the length of the herringbone inner arm is L3. L2 is an adjustable parameter used to adjust the reflection phase characteristics, and L3 is used to determine the basic geometric shape of the herringbone structure.

5. The double-layer symmetrical cross-shaped metasurface unit according to claim 4, characterized in that, Both the first dielectric substrate layer and the second dielectric substrate layer are square flat plate structures with side lengths consistent with the cell period and a thickness of H_sub, and are made of low dielectric loss material.

6. The double-layer symmetrical cross-shaped metasurface unit according to claim 5, characterized in that, The first dielectric substrate layer is bonded to the lower surface of the upper metal patch layer, and the second dielectric substrate layer is bonded between the lower surface of the lower metal patch layer and the upper surface of the metal ground layer.

7. The double-layer symmetrical cross-shaped metasurface unit according to claim 6, characterized in that, The air spacer layer is a square cavity structure with a side length consistent with the unit period and a thickness of H_air. It is sandwiched between the first dielectric substrate layer and the lower metal patch layer to form an air resonant cavity structure.

8. The double-layer symmetrical cross-shaped metasurface unit according to claim 7, characterized in that, The metal floor layer is a complete square copper plate with a side length consistent with the unit period and a thickness of h.

9. A high-gain, wide-beam metasurface reflector antenna based on the double-layer symmetrical cross-shaped metasurface unit as described in any one of claims 1 to 8, characterized in that, Includes a conical horn feed and a reflector array; The reflective array is composed of two or more metasurface units arranged in an aperiodic phase-compensated distribution. Within the operating frequency band, the reflective array is designed with phase compensation based on the spatial phase distribution of the conical horn feed source, so that the reflected wave is converted from a spherical wave to a quasi-plane wave, enabling the antenna to form a directional radiation main lobe, and expanding the beam coverage range while ensuring concentrated energy radiation, while effectively suppressing the sidelobe level.

10. A high-gain wide-beam metasurface reflector antenna as described in claim 9, characterized in that, The reflective array is designed through the following steps: Step 1: Design metasurface units and determine the correspondence between the geometric parameters of the metasurface units and the reflection phase; Step 2: Construct a reflective array consisting of two or more metasurface units in an aperiodic arrangement. Step 3: Select a feed antenna to excite the reflective array; Step 4: Determine the array layout parameters based on the feed characteristics and the size of the reflective array; Step 5: Position the feed antenna at the focal point corresponding to the reflector array; Step 6: Obtain the near-field phase distribution of the feed antenna in the aperture plane of the reflector array; Step 7: Calculate the compensation phase distribution required for the reflective array based on the near-field phase distribution; Step 8: Based on the correspondence between geometric parameters and reflection phase, convert the compensation phase distribution into the geometric parameters of each metasurface unit; Step 9: Arrange the reflection array according to the geometric parameters of each unit; Step 10: Complete the design and construction of the reflective array, and form a high-gain wide-beam metasurface reflective antenna.

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