A broadband beam-steering fabry-perot antenna based on water-based metasurface

Abstract

A kind of broadband beam regulation and control fabry-perot antenna based on water-based metasurface, wherein the feed antenna is composed of a ground plate, a dielectric substrate I, a metal radiation patch and a coaxial probe for providing excitation for the metal radiation patch;Part of the reflecting surface is composed of a water-based metasurface, and the unit structure is composed of a dielectric substrate II with a bottom etched square metal patch, a water container next to the top and a water layer therein;The water-based metasurface is expanded as a partially reflective surface and loaded above the feed antenna to form a fabry-perot resonant cavity antenna, with a working bandwidth covering 5.10-5.63GHz, realizing the expansion of the working frequency band and a peak gain of 11.2dBi;On this basis, by controlling the water injection and emptying state of each independent water cavity to adjust the unit reflection phase, and using the coded water injection combination of different water cavities to construct various reflection phase gradient distributions on the aperture of the partially reflective surface, the flexible regulation and control of the beam deflection direction and angle can be realized.

Description

Technical Field

[0001] This invention relates to the field of communication equipment and component technology, and in particular to antennas based on metasurfaces and reconfigurable beam control antenna technology, specifically to a broadband beam-tuned Fabry-Perot antenna based on a water-based metasurface. Background Technology

[0002] As modern wireless communication systems evolve towards higher frequencies, greater integration, and multi-scenario applications, antennas, as core front-end devices, face the challenge of designing a synergistic combination of performance indicators, including high gain, wide bandwidth, and flexible beam control. Traditional antenna types, such as microstrip antennas and horn antennas, while each with its advantages, exhibit significant limitations in achieving both high gain and wideband radiation. Fabry-Perot resonator antennas (FPRAs), with their unique resonator structure, effectively concentrate electromagnetic energy and generate high-directional radiation by constructing multiple reflections and interference mechanisms between the partially reflective surface (PRS) and the ground plane, thus attracting widespread attention in the field of high-gain antennas. However, in complex and ever-changing communication environments, the antenna's dynamic beam control capability has become crucial for improving system performance. Whether achieving flexible coverage through beam scanning or improving spatial multiplexing efficiency through multi-beam radiation, beam control technology is of great significance for meeting the application requirements of base station communication, satellite links, and multi-target sensing. Therefore, antennas with dynamic beam control capabilities have become one of the core technical requirements of modern wireless communication systems.

[0003] Traditional FPRAs (Front-Field Resonant Radiation Arrays) have significant limitations in beam control. Their radiation properties are determined by the electromagnetic characteristics of the resonant cavity structure and some reflective surfaces. Once the antenna is fabricated, its beam pointing and shape are fixed, making dynamic adjustment difficult. Existing research on FPRA beam control mostly employs methods such as loading active devices like PIN diodes or mechanical rotation. The former often introduces nonlinear distortion and high control circuit losses, while the latter suffers from slow response speed and complex structure, failing to meet the requirements of integration and dynamic reconfigurability. Therefore, achieving simple, efficient, and reversible dynamic beam control while maintaining the high gain and broadband advantages of FPRAs has become a critical technological bottleneck that urgently needs to be overcome in this field.

[0004] Metasurfaces, as artificial electromagnetic structures composed of subwavelength element arrays, possess the ability to flexibly control parameters such as electromagnetic wave amplitude, phase, and polarization, providing new design ideas for optimizing antenna performance. Introducing metasurfaces into FPRA structures to replace traditional partial reflective surfaces can not only effectively extend the antenna's operating bandwidth but also improve radiation characteristics through phase modulation, achieving a better balance between high gain and broadband. In recent years, water materials have demonstrated unique advantages in the field of tunable electromagnetic devices due to their high dielectric constant, low loss, optical transparency, and environmental friendliness. The dielectric properties of water can be dynamically changed by filling and discharging it; introducing it into metasurface structures can achieve reversible electromagnetic response modulation, providing a potential technical path for antenna beam reconfiguration. Summary of the Invention

[0005] The purpose of this invention is to address the problems of fixed beam pointing in existing Fabry-Perot resonant cavity antennas and their beam reconfiguration techniques. Furthermore, relying on traditional active devices such as PIN diodes or mechanical rotation for dynamic control easily introduces large nonlinear distortion, high control circuit losses, and slow system response. Consequently, water-based metasurface antennas suffer from difficulties in achieving efficient liquid filling and discharging and accurate spatial phase gradient construction while maintaining high gain, low sidelobes, and other electromagnetic radiation performance, due to the lack of reasonable physical boundary isolation and fluid channel structure optimization between array elements. Therefore, this invention is proposed.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A broadband beam-tuned Fabry-Perot antenna based on a water-based metasurface, the antenna comprising a bottom feed antenna, a top reflective surface, and a middle resonant cavity; Some of the reflective surfaces are composed of several adjacent water-based metasurface units; from top to bottom, the water-based metasurface units are a metal backplate, a dielectric substrate II, and a water container; the internal cavity of the water container is used to contain the water layer.

[0007] The cross-sections of the metal backplate, dielectric substrate II, and water container are all square; the internal cavity of the water container used to contain the water layer is generally square in structure, and a central groove is provided through the upper side to the lower layer of the square structure; water channels connecting the water containers of other adjacent water-based metasurfaces are provided on both sides of the water container.

[0008] In the water-based metasurface unit, the water channels on both sides of the water container are located on the same straight line, and the central groove is cylindrical. The straight line penetrates the central groove radially in a cylindrical shape.

[0009] The partially reflective surface is obtained by arranging several water-based metasurface units in a longitudinal and transverse checkerboard pattern, and removing the L-shaped structure composed of three water-based metasurface units at the four corners of the checkerboard.

[0010] From bottom to top, the feed antenna consists of a coaxial probe, a metal ground plane, dielectric substrate I, and a metal radiating patch. The dielectric substrate I and the metal ground plane covering it are square structures, and a circular hole is opened in the middle of the dielectric substrate I and the metal ground plane to allow the coaxial probe to pass through.

[0011] The metal radiating patch has a square structure and is etched on the center of the upper surface of dielectric substrate I. The cross-section of the metal radiating patch is obtained by subtracting two sectors from the two centrally symmetrical corners of the square. The coaxial probe consists of an inner conductor, an outer conductor, and an intermediate medium. The top of the inner conductor is connected to a metal radiation patch, and the outer conductor is connected to a metal ground plane.

[0012] An air resonant cavity is formed between the partial reflective surface and the metal ground plane of the feed antenna; the electromagnetic waves emitted by the feed antenna are reflected multiple times in the resonant cavity and superimposed on each other, and then transmitted out through the partial reflective surface of the water-based metasurface to enhance the electromagnetic waves in a specific frequency band, thereby improving the gain.

[0013] The water-based metasurface adjusts the unit reflection phase by controlling the injection and drainage of water layers in each water cavity, and constructs multiple reflection phase gradient distributions on part of the reflective surface aperture by using coded water injection combinations of different water cavities, thereby achieving flexible control of beam deflection angle and direction.

[0014] The coaxial probe, metal ground plane, metal radiating patch, and metal backplate in the feed antenna and water-based metasurface structure are all made of copper, with a thickness of [missing information]. The diameters of the inner and outer cylindrical conductors of the coaxial probe are respectively: The width of the metal grounding plate is The diameter of the circular hole through which the coaxial probe passes is The width of the metal radiation patch is The subtracted radius of the sector structure is The central angle is 90°; the width of the metal back plate is... .

[0015] The width of the hollowed-out square water layer on the water-based metasurface is The diameter of the cylindrical structure excavated at its center is The width of the water channels added to its left and right is The thickness of the rectangular water layer is The thickness of the water channel is This allows the adjacent hollow rectangular water layers to be interconnected.

[0016] The water container is made of PDMS material through a secondary molding process, with a relative permittivity of 2.72 and a loss tangent of 0.0027; its width is... Thickness is The distances from the upper and lower surfaces of the water container to the upper and lower surfaces of the rectangular perforated water layer are both ; Both dielectric substrate I and dielectric substrate II are square structures, with widths of: The dielectric substrate I is made of FR4 material with a relative permittivity of 4.3, and it has a hole with a diameter of [missing information]. The circular hole allows the coaxial probe to pass through; the dielectric substrate II is made of Rogers 4003C material with a relative permittivity of 3.55; The air resonant cavity between the partially reflective surface of the water-based metasurface and the feed antenna, i.e., the spatial distance between the upper surface of the dielectric substrate I and the lower surface of the water container, is... .

[0017] Compared with the prior art, the present invention has the following technical effects: 1) This invention provides a Fabry-Perot resonator antenna based on a water-based metasurface, using the periodically extended ground metasurface as a partial reflective surface. Compared to feed antennas, this antenna effectively broadens the operating bandwidth and improves gain. Furthermore, by controlling the filling and draining of water in the water-based metasurface unit, the reflection amplitude and phase can be controlled, thereby regulating the electromagnetic response characteristics of the partial reflective surface and achieving dynamic control of the antenna beam deflection direction and angle. 2) The L-shaped structure at the four corners of the checkerboard-style reflective surface has been removed. This design effectively improves the electromagnetic field distribution at the antenna aperture and reduces edge diffraction effects. Combined with the bottom-mounted feed antenna, it can maintain a high peak gain (up to 11.2 dBi) while achieving wide-band operation (5.1-5.6 GHz) and effectively reducing sidelobe levels. 3) The square metal radiating patch of the feed antenna has a fan-shaped structure removed at the two centrally symmetrical corners, which can excite and degenerate two similar orthogonal resonant modes, thereby effectively expanding the inherent impedance bandwidth of the bottom feed antenna and providing a stable excitation source for the entire system to achieve beam scanning in a wide frequency band. 4) In the water-based metasurface unit, the present invention sets water channels on the same straight line only on both sides of the water container; this structure constitutes a low-resistance microfluidic channel in terms of fluid dynamics, which effectively improves the transmission efficiency of water flow between units and the water filling and discharging response speed; at the same time, the two sides without channels form a physical partition, ensuring the independence between different quadrants (water chambers) of the metasurface array, which is convenient for subsequent construction of different reflection phase gradients. 5) The water container uses a cylindrical groove instead of a polygonal structure, which reduces right-angle dead cavities during fluid transmission and lowers the probability of microbubble trapping, thereby maintaining the stability of the dielectric constant of the water layer and improving the accuracy of reflection phase control; at the same time, the cylindrical structure exhibits a more uniform electromagnetic resonance response when facing incident electromagnetic waves with different polarization directions. 6) The design of the water channel, which is cylindrical and radially penetrates the central slot, maintains the axial physical and electromagnetic boundary symmetry of the water-based metasurface unit. This symmetrical structure effectively suppresses cross-polarization radiation caused by structural asymmetry, enabling the antenna to maintain good co-polarization purity during beam deflection. Attached Figure Description

[0018] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 This is a perspective view of a broadband beam-controlled Fabry-Perot antenna based on a water-based metasurface, as described in Example 1. Figure 2 The top and side views are of a prototype of a broadband beam-controlled Fabry-Perot antenna based on a water-based metasurface, as described in Example 1. Figure 3 This is a structural diagram and side view of the metal radiating patch structure of the feed antenna in a broadband beam-controlled Fabry-Perot antenna based on a water-based metasurface, as shown in Example 1. Figure 4 (a), (b), and (c) are an overall view of the water-based metasurface unit structure, a top view of the water layer, and a side view of the unit structure of a broadband beam-controlled Fabry-Perot antenna based on a water-based metasurface in Example 1. Figure 5 This is a schematic diagram of the reflection amplitude and reflection phase of the water-based metasurface in a broadband beam-controlled Fabry-Perot antenna based on a water-based metasurface, as shown in Example 2. Figure 6 The S-type feed antenna in a broadband beam-controlled Fabry-Perot antenna based on a water-based metasurface, as described in Example 3. 11 Simulation results of gain; Figure 7 The simulated radiation patterns of the feed antenna in a broadband beam-controlled Fabry-Perot antenna based on a water-based metasurface in Example 3 are shown at 5.2 GHz and 5.6 GHz. Figure 8 This is a schematic diagram showing the numbering order of the four water chambers of the water-based metasurface PRS in a broadband beam-controlled Fabry-Perot antenna based on a water-based metasurface, as described in Example 4. Figure 9This document presents schematic diagrams and simulated and measured radiation patterns of eight beam control modes of a broadband beam-controlled Fabry-Perot antenna based on a water-based metasurface, at 5.3 GHz and 5.5 GHz, along the ±45° diagonal directions of the E-plane, H-plane, and EH-plane, respectively. Figure 10 Example 5 illustrates the S-mode of a broadband beam-controlled Fabry-Perot antenna based on a water-based metasurface in eight beam control modes. 11 Simulation and measured results of gain are shown in the figure; Figure 11 This is a side view of a model of a broadband beam-controlled Fabry-Perot antenna based on a water-based metasurface, as shown in Example 1. Detailed Implementation

[0019] like Figures 1 to 4 As shown, the broadband beam-tuned Fabry-Perot antenna based on a water-based metasurface consists of a bottom feed antenna, a top reflective surface, and a middle resonant cavity. Some of the reflective surfaces are composed of several adjacent water-based metasurface units; from top to bottom, the water-based metasurface units are a metal backplate, a dielectric substrate II, and a water container; the internal cavity of the water container is used to contain the water layer.

[0020] The cross-sections of the metal backplate, dielectric substrate II, and water container are all square; the internal cavity of the water container used to contain the water layer is generally square in structure, and a central groove is provided through the upper side to the lower layer of the square structure; water channels connecting the water containers of other adjacent water-based metasurfaces are provided on both sides of the water container.

[0021] In the water-based metasurface unit, the water channels on both sides of the water container are located on the same straight line, and the central groove is cylindrical. The straight line penetrates the central groove radially in a cylindrical shape. The purpose of using a structure where the water channels on both sides of the water container are aligned in a straight line, rather than being open on all four sides, is twofold: First, in terms of electromagnetic control, setting channels only on both sides ensures physical and electromagnetic isolation between different array regions (i.e., four independent water chambers); second, in terms of fluid dynamics, the design of channels on both sides being aligned in a straight line creates a DC microfluidic channel with minimal resistance, which reduces the transmission obstruction of water flow between units and improves the water filling and discharging response speed and dynamic switching efficiency of the antenna when switching between different beam states.

[0022] The structure employs a cylindrical central groove. On one hand, the cylindrical groove avoids the edge concentration effect (sharp effect) of the electromagnetic field caused by right angles, resulting in a more uniform and symmetrical electromagnetic resonance response from the metasurface unit when facing incident electromagnetic waves with different polarization directions. On the other hand, fluid passing through the right-angle structure easily generates eddies and traps tiny bubbles. The cylindrical design eliminates right-angle dead cavities from a fluid dynamics perspective, completely avoiding abrupt changes in the dielectric constant caused by residual bubbles, thus ensuring the accuracy and repeatability of reflection phase control.

[0023] The structure employs a straight line radially penetrating the central slot in a cylindrical shape. This strict radial symmetry ensures the absolute consistency of the physical and electromagnetic boundary conditions of the water-based metasurface unit along the left and right axes of symmetry. This extreme symmetry suppresses cross-polarization radiation caused by structural asymmetry, ensuring that the antenna maintains extremely high co-polarization purity and extremely low signal distortion during high-gain beam scanning.

[0024] The partially reflective surface is obtained by arranging several water-based metasurface units in a longitudinal and transverse checkerboard pattern, and removing the L-shaped structure composed of three water-based metasurface units at the four corners of the checkerboard. Removing the L-shaped structure at the four corners optimizes the field distribution of the antenna aperture and suppresses edge diffraction. This allows the FPRA antenna to maintain high gain (up to 11.2 dBi) while reducing sidelobe levels and improving the directional radiation purity of the main lobe. At the same time, this angled design, combined with the centrally symmetrical array arrangement, physically defines four independent water chambers (quadrants I to IV); this provides a physical spatial isolation and symmetry basis for subsequently realizing eight beam deflection modes in the E-plane, H-plane, and ±45° diagonal direction through four-bit binary encoding (such as 0011, 1100); From bottom to top, the feed antenna consists of a coaxial probe, a metal ground plane, dielectric substrate I, and a metal radiating patch. The dielectric substrate I and the metal ground plane covering it are square structures, and a circular hole is opened in the middle of the dielectric substrate I and the metal ground plane to allow the coaxial probe to pass through.

[0025] The metal radiating patch has a square structure and is etched on the center of the upper surface of dielectric substrate I. The cross-section of the metal radiating patch is obtained by subtracting two sectors from the two centrally symmetrical corners of the square. By adopting this structure, two similar orthogonal resonant modes can be excited and degenerate by introducing a fan-shaped perturbation structure of a specific size at the diagonal of the symmetrical square patch. This not only expands the inherent impedance bandwidth of the underlying feed antenna, but also forms the feed basis for the final antenna to achieve stable high-gain beam scanning in the 5.1-5.6 GHz wideband.

[0026] The coaxial probe consists of an inner conductor, an outer conductor, and an intermediate medium. The top of the inner conductor is connected to a metal radiation patch, and the outer conductor is connected to a metal ground plane.

[0027] An air resonant cavity is formed between the partial reflective surface and the metal ground plane of the feed antenna; the electromagnetic waves emitted by the feed antenna are reflected multiple times in the resonant cavity and superimposed on each other, and then transmitted out through the partial reflective surface of the water-based metasurface to enhance the electromagnetic waves in a specific frequency band, thereby improving the gain.

[0028] The water-based metasurface adjusts the unit reflection phase by controlling the injection and drainage of water layers in each water cavity, and constructs multiple reflection phase gradient distributions on part of the reflective surface aperture by using coded water injection combinations of different water cavities, thereby achieving flexible control of beam deflection angle and direction.

[0029] The coaxial probe, metal ground plane, metal radiating patch, and metal backplate in the feed antenna and water-based metasurface structure are all made of copper, with a thickness of [missing information]. The diameters of the inner and outer cylindrical conductors of the coaxial probe are respectively: The width of the metal grounding plate is The diameter of the circular hole through which the coaxial probe passes is The width of the metal radiation patch is The subtracted radius of the sector structure is The central angle is 90°; the width of the metal back plate is... .

[0030] The 90° central angle of the fan-shaped chamfer precisely matches the orthogonal boundary of the square radiating patch. This specific geometric perturbation not only causes a specific phase shift in the surface current path of the patch, exciting and degenerates two near-range resonant modes with equal amplitude and orthogonal phase, but also avoids the asymmetric higher-order mode interference that might be introduced by a non-90° chamfer. Thus, while ensuring that the radiation beam is not distorted, the impedance bandwidth of the underlying feed antenna is widened to the maximum extent. The copper layer thickness is limited to 0.025~0.035mm, which is just greater than the skin depth of electromagnetic waves in the copper conductor at the 5GHz frequency band. This ensures efficient transmission of radio frequency signals and minimizes conductor ohmic loss. At the same time, strictly controlling the thickness to within 0.035mm reduces lateral etching (lateral etching effect) in the etching process, ensuring the processing accuracy of the metasurface subwavelength unit width of 11.9~12.0mm, which is conducive to maintaining the accuracy of the resonant phase at high frequencies. The width of the hollowed-out square water layer on the water-based metasurface is The diameter of the cylindrical structure excavated at its center is The width of the water channels added to its left and right is The thickness of the rectangular water layer is The thickness of the water channel is This allows the adjacent hollow rectangular water layers to be interconnected.

[0031] By limiting the width and thickness of the water channels to the sub-millimeter level of 0.9~1mm, an optimized microcapillary effect is achieved from a fluid dynamics perspective. This size avoids the extremely high liquid flow resistance caused by excessively narrow channels, while preventing electromagnetic leakage and parasitic electromagnetic coupling between adjacent water chambers caused by excessively wide channels; it ensures rapid liquid drive while maintaining high electromagnetic isolation between the four quadrant water chambers. The water container is made of PDMS material through a secondary molding process, with a relative permittivity of 2.72 and a loss tangent of 0.0027; its width is... Thickness is The distances from the upper and lower surfaces of the water container to the upper and lower surfaces of the rectangular perforated water layer are both ; Choosing PDMS with its specific dielectric properties as the substrate for water containers offers a dual electromagnetic synergy. On one hand, its extremely low loss tangent (0.0027) ensures that the absorption of electromagnetic wave energy is minimized when used as a partial reflective surface (PRS), maintaining the high gain characteristics of the antenna. On the other hand, its relatively low dielectric constant (2.72) creates a significant dielectric contrast with the high dielectric constant of liquid water (approximately 80). This large gradient difference allows for a sufficiently large reflection phase difference (such as the 60° mentioned above) when switching between "filling" and "draining" states, thus providing ample phase adjustment margin for large-angle deflection of the broadband beam.

[0032] Both dielectric substrate I and dielectric substrate II are square structures, with widths of: The dielectric substrate I is made of FR4 material with a relative permittivity of 4.3, and it has a hole with a diameter of [missing information]. The circular hole allows the coaxial probe to pass through; the dielectric substrate II is made of Rogers 4003C material with a relative permittivity of 3.55; The bottom feed uses FR4 with a high dielectric constant (4.3), which reduces the physical size of the metal radiating patch, suppresses surface wave excitation, and makes the feed structure more compact. The top metasurface uses Rogers 4003C with a lower dielectric constant (3.55) and extremely low high-frequency loss, which helps improve the transmittance and phase response stability of some reflective surfaces. This heterogeneous stacked design, with a high dielectric constant at the bottom for convergent size and a low dielectric constant at the top for reduced loss, effectively achieves high radiation efficiency for the entire antenna in the 5.1-5.6 GHz frequency band. The air resonant cavity between the partially reflective surface of the water-based metasurface and the feed antenna, i.e., the spatial distance between the upper surface of the dielectric substrate I and the lower surface of the water container, is... .

[0033] Within the 5.1-5.6 GHz operating frequency band, this distance, combined with the reflection phase of the water-based metasurface and the metal ground plane, satisfies the positive feedback interference superposition condition within the resonant cavity; locking the distance in the 25.5~26.5 mm range allows the multipath reflected wave to achieve ideal in-phase transmission near the center frequency point, thereby achieving a resonant cavity physical gain peak of up to 11.2 dBi. Example 1: This example discloses a broadband beam-tuned Fabry-Perot antenna based on a water-based metasurface, the overall structure of which is as follows: Figure 1 As shown, the proposed FPRA was physically manufactured, and its top and side views are as follows. Figure 2 As shown. The proposed antenna consists of a bottom-feed antenna, a partially reflective surface placed parallel to the feed, and an air resonant cavity between them. The feed antenna structure, from bottom to top, comprises a coaxial probe, a metal ground plane, dielectric substrate I, and a metal radiating patch etched onto it. The specific structure is shown in top and side views. Figure 3 As shown. Dielectric substrate I is made of FR4 material with a relative permittivity of 4.3, and its thickness is... The metal radiating patch and metal ground plane etched on the upper surface of dielectric substrate I are both made of metal with a thickness of 0.035 mm. The metal radiating patch consists of a width... The square structure minus the radius at one diagonal It consists of a sector-shaped structure, with the center of the sector located 0.1 mm from the vertex of the square. The width after subtracting... The size of the metal ground plane is the same as that of dielectric substrate I. To allow the coaxial probe to pass through and connect with the metal radiating patch, the horizontal distance between the center point of dielectric substrate I and the metal ground plane is... vertical distance An opening is provided. The coaxial probe consists of an inner conductor, an outer conductor, and an intermediate dielectric. The inner conductor is connected to a metal radiating patch, and the outer conductor is connected to a metal ground plane.

[0034] Perspective and side views of the water-based metasurface unit structure are as follows: Figure 4 As shown in (a) and (c), from top to bottom, they are a metal backplate, dielectric substrate II, a water container, and a water layer therein. Dielectric substrate II has a thickness of... It is made of Rogers 4003C with a relative permittivity of 3.55. The width of both the dielectric substrate II and the water container is... The water container is made of PDMS with a relative permittivity of 2.72. The metal backplate is [width missing]. The square structure corresponds at its center to dielectric substrate II. The water layer is located at a distance from both the upper and lower surfaces of the water container. At this point, the overall thickness of the water layer A top view of the water layer structure is shown below. Figure 4 As shown in (b), it is a hollowed-out square structure with a cylindrical groove carved out in the center, and its width is... The radius of the cylindrical groove To facilitate water flow between unit structures, a width of [missing information] is applied near the bottom at the center of the left and right sides of the water layer. ,high The water channel. The partially reflective surface is composed of 12×12 adjacent water-based metasurface units, and the "L"-shaped structure formed by the three units at the four corners is removed.

[0035] Example 2: The FPRA (Feature-Plug-in Reflector) achieves a gain boost by loading a partial reflective surface (PRS) onto the feed antenna and combining it with a metal ground plane to form a resonant cavity. The electromagnetic waves radiated by the feed antenna undergo multiple reflections and interferences within the resonant cavity before being transmitted again. The maximum gain increment of the FPRA relative to the feed antenna can be described by the following formula:

[0036] in For the maximum gain increment, This represents the amplitude of the reflection coefficient of the partially reflecting surface. This indicates that the larger the reflection amplitude of the partially reflecting surface, the stronger the cavity's ability to improve antenna gain.

[0037] For the beam control principle of FPRA, its beam deflection angle is constrained by the resonance condition:

[0038] in, Beam deflection angle, The reflection phase of the PRS, The reflected phase of the metal ground plane. The height of the resonant cavity. The wavelength of electromagnetic waves in free space. N This refers to the mode order. It is generally accepted that a metallic ground plane can be considered an ideal conductor with total internal reflection characteristics, and its reflection phase... Furthermore, the height of the resonant cavity is typically a fixed value. Therefore, the reflection phase of the PRS becomes a key variable for achieving beam control. Specifically, if the reflection phase of the PRS exhibits a gradient distribution on the aperture plane of the feed antenna, the transmitted wavefront will tilt, thereby achieving beam deflection.

[0039] Based on the above principles, this invention uses a water-based metasurface to construct a PRS (Pressure Reflection Array). Utilizing the reversible change in the dielectric properties of water with and without water filling and discharging, the metasurface units possess different reflection phases in the "with water" and "without water" states. By rationally arranging the two types of units, the required reflection phase gradient can be formed on the PRS aperture surface, thereby achieving dynamic control of beam deflection without altering the antenna's physical structure.

[0040] To verify the electromagnetic properties of the water-based metasurface, the reflection amplitude and phase of the water-based metasurface under two conditions of water filling and discharging were simulated and calculated using CST (Computer Simulation Technology) software. Boundary conditions were maintained along... x shaft and y Set the axis to "unit cell". z The axis is set to "open (add space)", and electromagnetic waves are generated by... z max The light is incident on the metal backplate. Figure 5 As shown in (a), the reflection amplitude of the metasurface remains relatively stable with frequency in the absence of water, consistently above 0.8. With water, the reflection amplitude of the metasurface decreases overall, but remains above 0.70 in the 5.0-5.8 GHz frequency band, reaching a maximum of 0.78. Figure 5 As shown in (b), the reflection phase of the metasurface decreases with increasing frequency in both the waterless and water-containing states, and there is a 60° reflection phase difference between the water-containing and waterless states. This phase difference provides a design basis for constructing the reflection phase gradient on the PRS aperture surface. Overall, the water-based metasurface proposed in this invention possesses both high reflection amplitude to ensure the gain performance of the FPRA in both "water-containing" and "waterless" states, and can provide significant reflection phase differences to achieve dynamic beam control, laying a theoretical foundation for the final broadband high-gain and flexible beam control of the antenna.

[0041] Example 3: The performance of the feed antenna directly determines the overall radiation characteristics of the Fabry-Perot resonator antenna. To achieve the ultimate goal of wide bandwidth and high gain, the feed antenna must meet requirements such as wide bandwidth, stable gain, and directional radiation. For the designed feed antenna, its S... 11 The parameters and gain were simulated and calculated, such as Figure 6 As shown in the figure. From the figure, we can obtain the operating frequency band (S...) of this feed antenna. 11 The radiation patterns (<-10dB) are 5.14-5.34GHz and 5.40-5.63GHz. Within its operating frequency band, the gain is consistently above 5.8dBi, with a maximum gain reaching 6.5dBi. To further analyze its radiation characteristics, the E-plane and H-plane radiation patterns at 5.2GHz and 5.6GHz were monitored, as shown below. Figure 7 As shown in (a)(b). From Figure 7 As can be seen, the feed antenna exhibits stable radiation within its operating frequency band, demonstrating good radiation directivity and high symmetry. Overall, the designed feed antenna possesses a wide operating bandwidth, stable in-band gain, and excellent directional radiation characteristics, providing reliable feed support for achieving the final FPRA.

[0042] Example 4: The PRS consists of a 12×12 array of water-based metasurfaces arranged periodically, with three units removed from each of the four corners of the square array to form an "L"-shaped structure. Simultaneously, the array is symmetrically divided into four independent water chambers along its center and numbered, with each group consisting of 33 units. Figure 8 As shown. By controlling the filling and emptying states of different water chambers, different combinations of reflection phase gradients are formed along the surface of the PRS, thereby achieving multiple beam deflection modes. The PRS is placed parallel above the feed antenna, and the resonant cavity height is set to 25.5 mm to form the final FPRA.

[0043] To facilitate the description of the water filling and emptying states corresponding to different beam deflection modes of the FPRA, water-filled chambers are coded as "1", while unfilled (i.e., air-filled) chambers are coded as "0". Therefore, all possible water filling combinations for the four chambers (Ⅰ ~ Ⅳ) can be represented by four-bit binary codes (0000) to (1111). Of the 16 combinations mentioned above, 8 configurations can produce effective beam deflection. As shown in Example 2, the reflection phase of water-filled and waterless metasurface units has a relatively fixed difference. Therefore, different water filling combinations will generate different phase gradients along the PRS surface, thereby guiding the beam radiated from the resonant cavity to undergo angular deflection.

[0044] To investigate the specific beam deflection of the FPRA, the radiation patterns of the FPRA at 5.3 GHz and 5.5 GHz were monitored. The specific simulation and measurement results are as follows: Figure 9 As shown. Figure 9 (a) shows the E plane ( xoz A schematic diagram of beam deflection within the surface, corresponding to water-filled combinations (0011) and (1100). The water-based metasurface PRS will deflect the beam away from the direction of the normal. Figure 9 As shown in (b), at a frequency of 5.3 GHz, the simulated beam deflection angle is ±23°. The measured (1100) combination matches the simulation, while the measured deflection angle of the (0011) combination reaches 30°. At 5.5 GHz, as... Figure 9 (c) The simulated beam deflection angle is ±25°. The measured deflection angle is basically consistent with the simulation, but the sidelobe amplitude has increased. Similar to the E-plane, beam deflection in the H-plane can be achieved by the phase gradient created by the water-filled combination (0110) and (1001), corresponding to the deflection plane ( yoz (Surface) and deflection conditions as follows Figure 9 As shown in (d). Figure 9 (e) shows that the simulated deflection angles for both water-filling combinations at 5.3 GHz are ±23°, and the measured deflection angles match the simulations. Figure 9 (f) shows that at 5.5 GHz, the simulated deflection angle of the FPRA reached ±26°. In the actual measurement, the deflection angle of the (1001) combination is consistent with the simulation, while the deflection angle of the (0110) combination decreased to -22°. The above results show that by controlling the water filling combination of the four water chambers to create a phase gradient along the E and H planes, the beam deflection of the FPRA on the E and H planes can be realized.

[0045] Furthermore, defining the E-plane as a horizontal rotation of 0°, then the H-plane is a rotation of 90° perpendicular to the E-plane. Similarly, beam deflection along the ±45° rotation direction is achieved by controlling the water filling combination of the four water chambers. For the -45° plane (corresponding to...) xy=0 noodle), Figure 9 (g) shows the corresponding beam deflection. For example... Figure 9 As shown in (h)(i), when the water-filled combinations are (0111) and (1101), the water-based metasurface PRS guides the beam to the -45° plane. At this time, the simulated deflection angle of the FPRA at 5.3 GHz is ±26°, while the measured value for combination (0111) is 22°, and combination (1101) is similar to the simulation. At 5.5 GHz, the simulated deflection angle of the FPRA reaches ±30°, the measured value for combination 0111 decreases to 24°, and combination 1101 basically matches the simulation. At both frequencies, the sidelobe amplitudes of the measured radiation pattern increase. Correspondingly, Figure 9 (j) shows the +45° plane (i.e.) x+y=0 A schematic diagram of beam deflection within the plane. When the water-filled combination is (1011)(1110), the beam is guided to the +45° plane. (See diagram for example.) Figure 9As shown in (k)(l), the simulated deflection angle at 5.3 GHz is ±25°, and the measured deflection angle is the same as the simulation, but the sidelobe amplitude increases. At 5.5 GHz, the deflection angle of the FPRA reaches ±31°. In the actual measurement, the (1110) combination is 24°, and the (1011) combination is the same as the simulation. The overall measured sidelobe amplitude decreases compared to the simulation. Overall, the proposed FPRA can achieve a total of 8 beam deflection modes in the E-plane, H-plane, and ±45° diagonal direction. The maximum deflection angle obtained in the simulation is 31°, which demonstrates the effectiveness of the antenna in beam dynamic control. The measured results of the FPRA further verify the accuracy of the simulation results.

[0046] Example 5: To further evaluate the overall performance of the proposed FPRA, the S-beam deflection modes in Example 4 were compared. 11 The parameters and gain characteristics were analyzed through simulation and experimental measurements. The simulation results of the FPRA operating bandwidth are as follows: Figure 10 As shown in (a), the eight deflection modes corresponding to the E-plane, H-plane, and EH-plane ±45° diagonal directions all achieved a working bandwidth coverage of 5.10-5.63 GHz. The measured results are similar to the simulation results; the working bandwidth of all eight beam deflection modes broadened in the low-frequency and high-frequency portions of the simulated working bandwidth, and also increased in the S... 11 The curve becomes deeper at the first resonance peak and shallower at the second resonance peak. The simulation and measured results of the gain performance are as follows: Figure 10 As shown in (b), simulation results indicate that under both E-plane and H-plane beam deflection modes, the overall gain within the FPRA operating bandwidth remains above 8.7 dBi, with a peak gain reaching 11.2 dBi. In actual measurements, the H-plane deflection mode matches the simulation in the low and high frequency ranges, while the gain in the mid-frequency band decreases, reaching a minimum of 6.8 dBi. In contrast, the overall gain increases under the E-plane deflection mode, reaching a maximum of 13 dBi. For the ±45° diagonal beam deflection mode in the EH plane, the simulated gain is lower than the previous two modes, with an overall bandwidth gain exceeding 6 dBi and a peak of 8.9 dBi. In actual measurements, under the -45° diagonal deflection mode, the gain decreases by approximately 0.5 dBi below 5.6 GHz compared to the simulation, and the curve trend matches the simulation. Above 5.6 GHz, the gain increases, with a maximum increase of 1 dBi. Under the +45° diagonal deflection mode, the gain below 5.4 GHz largely matches the simulation, while above 5.4 GHz, the gain increases, with a maximum increase of 2 dBi.

[0047] As demonstrated in Examples 4 and 5, the FPRA proposed in this invention, by controlling the water filling combination of four independent water chambers, can achieve a total of eight beam deflection modes in the E-plane, H-plane, and EH-plane ±45° diagonal directions, with a maximum deflection angle of 31°. Simultaneously, the antenna maintains a wide operating bandwidth (5.10~5.63 GHz) and good gain performance (11.2 dBi peak gain within the band) in all deflection modes. The experimental results effectively verify the accuracy of the simulation design and further highlight its comprehensive advantages in broadband, high gain, and dynamic beam control.

Claims

1. A broadband beam-tuned Fabry-Perot antenna based on a water-based metasurface, characterized in that, The antenna consists of a bottom-feed antenna, a top reflective surface, and a middle resonant cavity; Some of the reflective surfaces are composed of several adjacent water-based metasurface units; from top to bottom, the water-based metasurface units are a metal backplate, a dielectric substrate II, and a water container; the internal cavity of the water container is used to contain the water layer.

2. The antenna according to claim 1, characterized in that, The cross-sections of the metal backplate, dielectric substrate II, and water container are all square; the internal cavity of the water container used to contain the water layer is generally square in structure, and a central groove is provided through the upper side to the lower layer of the square structure; water channels connecting the water containers of other adjacent water-based metasurfaces are provided on both sides of the water container.

3. The antenna according to claim 2, characterized in that, In the water-based metasurface unit, the water channels on both sides of the water container are located on the same straight line, and the central groove is cylindrical. The straight line penetrates the central groove radially in a cylindrical shape.

4. The antenna according to claim 1, characterized in that, The partially reflective surface is obtained by arranging several water-based metasurface units in a longitudinal and transverse checkerboard pattern, and removing the L-shaped structure composed of three water-based metasurface units at the four corners of the checkerboard.

5. The antenna according to claim 1, characterized in that, From bottom to top, the feed antenna consists of a coaxial probe, a metal ground plane, dielectric substrate I, and a metal radiating patch. The dielectric substrate I and the metal ground plane covering it are square structures, and a circular hole is opened in the middle of the dielectric substrate I and the metal ground plane to allow the coaxial probe to pass through.

6. The antenna according to claim 5, characterized in that, The metal radiating patch has a square structure and is etched on the center of the upper surface of dielectric substrate I. The cross-section of the metal radiating patch is obtained by subtracting two sectors from the two centrally symmetrical corners of the square. The coaxial probe consists of an inner conductor, an outer conductor, and an intermediate medium. The top of the inner conductor is connected to a metal radiation patch, and the outer conductor is connected to a metal ground plane.

7. The antenna according to any one of claims 1 to 6, characterized in that, An air resonant cavity is formed between the partially reflective surface and the metal ground plane of the feed antenna; the electromagnetic waves emitted by the feed antenna are reflected multiple times in the resonant cavity and superimposed on each other before being transmitted out through the partially reflective surface of the water-based metasurface, thereby enhancing the electromagnetic waves in a specific frequency band and thus improving the gain. The water-based metasurface adjusts the unit reflection phase by controlling the injection and drainage of water layers in each water cavity, and constructs multiple reflection phase gradient distributions on part of the reflective surface aperture by using coded water injection combinations of different water cavities, thereby achieving flexible control of beam deflection angle and direction.

8. The antenna according to any one of claims 1 to 6, characterized in that, The feed antenna and the coaxial probe, metal ground plane, metal radiating patch, and metal backplate in the water-based metasurface structure are all made of copper, with a thickness of [missing information]. ; The diameters of the inner and outer cylindrical conductors of the coaxial probe are as follows: The width of the metal grounding plate is The diameter of the circular hole through which the coaxial probe passes is The width of the metal radiation patch is The subtracted radius of the sector structure is The central angle is 90°; the width of the metal back plate is... .

9. The antenna according to any one of claims 1 to 6, characterized in that, The width of the hollowed-out square water layer on the water-based metasurface is The diameter of the cylindrical structure excavated at its center is The width of the water channels added to its left and right is The thickness of the rectangular water layer is The thickness of the water channel is This allows the adjacent hollow rectangular water layers to be interconnected.

10. The antenna according to any one of claims 1 to 6, characterized in that, The water container is made of PDMS material through a secondary molding process, with a relative permittivity of 2.72 and a loss tangent of 0.0027; its width is... Thickness is The distances from the upper and lower surfaces of the water container to the upper and lower surfaces of the rectangular perforated water layer are both ; Both dielectric substrate I and dielectric substrate II are square structures, with widths of: The dielectric substrate I is made of FR4 material with a relative permittivity of 4.3, and it has a hole with a diameter of [missing information]. The circular hole allows the coaxial probe to pass through; the dielectric substrate II is made of Rogers 4003C material with a relative permittivity of 3.55; The air resonant cavity between the partially reflective surface of the water-based metasurface and the feed antenna, i.e., the spatial distance between the upper surface of the dielectric substrate I and the lower surface of the water container, is... .

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