Broadband circularly polarized metasurface antenna based on liquid reconfiguration

Abstract

The invention discloses a reconfigurable broadband circularly polarized metasurface antenna based on liquid, which is composed of three parts of structures including a top metal metasurface layer, a middle liquid layer and a bottom feed source antenna part. The top-layer metal metasurface comprises a dielectric plate F4B and a radiation metal sheet; the middle liquid layer is of a hollow structure in which liquid can be injected, and the structure consists of a medium PDMS (Polydimethylsiloxane); the bottom feed source antenna sequentially comprises a metal grounding plate, a dielectric plate F4B and a Wilkinson feed network from top to bottom. Signals are input to the Wilkinson power divider from the microstrip line connected with the 50-ohm microstrip line, and are transmitted to the middle liquid layer and the top metal metasurface through the four coupling gaps on the metal grounding plate, and switching of radiation and scattering modes by the antenna is realized by switching liquid injected into the liquid layer.

Description

Technical Field

[0001] This invention relates to the field of wireless communication technology, and more particularly to electromagnetic metasurface technology, specifically to a liquid-reconfigurable broadband circularly polarized metasurface antenna. Background Technology

[0002] With the rapid development of wireless communication technology, antenna technology, as a core component of communication systems, is facing dual requirements for performance and functionality. Metasurface antennas, as an emerging technology with low profile, high integration, and reconfigurability, have become the focus of antenna research. However, in practical deployment, metasurface antennas still face significant technical obstacles in broadband circular polarization and radar cross-section (RCS) control. How to achieve a balance between scattering and radiation effectiveness has become a new challenge in antenna design.

[0003] Metasurface antennas, leveraging the electromagnetic modulation properties of metamaterials, achieve precise modulation of the phase, amplitude, and polarization of electromagnetic waves through the periodic arrangement of subwavelength elements. This technology's outstanding performance in miniaturization, high gain, wide bandwidth, and reconfigurability makes it a promising candidate for applications in 5G communications, satellite communications, radar detection, and the Internet of Things (IoT). In the future, metasurface antennas are expected to find widespread application in even more fields, such as smart cities, telemedicine, and autonomous driving, providing strong support for the innovation of wireless communication technologies. Wideband circular polarization, a key pursuit in modern antenna technology, is highly favored in satellite communications, navigation systems, and radar due to its high tolerance to polarization mismatch and strong resistance to multipath interference. For example, in satellite communication systems, wideband circularly polarized antennas can ensure stable signal transmission in complex environments, thereby improving the reliability and stability of the communication system. Furthermore, in navigation systems, wideband circularly polarized antennas can reduce the impact of multipath effects on positioning accuracy, improve the performance of navigation systems, and provide more accurate positioning services for user travel safety.

[0004] In the field of modern radar and stealth technology, RCS control is the core of improving target stealth performance. As a key indicator for measuring the radar detectability of a target, reducing RCS is crucial for improving stealth performance.

[0005] Traditional RCS reduction methods face numerous challenges. For example, the paper "Phase Gradient Metasurface Radome Offering Beam Angle Translation and Wideband Absorption" describes using radome design to reduce the antenna's radar cross section, but its large size is detrimental to antenna concealment and limits its application on stealth platforms. The stealth coating mentioned in "Effects of radar absorption materials application on stealth performance of inlet based on risk theory" can reduce the radar detectability of targets, but its material properties often fail to meet the requirements of use in harsh environments such as high temperature and high humidity, leading to coating peeling or failure. "Simulation of Active Echo Cancellation Effects Using the ARCS Concept" utilizes active cancellation of the incident wave magnetic field, but the need for continuous signal transmission results in high energy consumption. In recent years, water-based metasurfaces have attracted widespread attention due to their unique electromagnetic control advantages. Water, as a tunable medium, can dynamically adjust electromagnetic parameters by changing its liquid state, providing new degrees of freedom for metasurface design. However, existing research largely focuses on the application of water-based metasurfaces in the field of absorbers, with few studies integrating them into antennas and simultaneously achieving circularly polarized radiation and RCS reduction. Therefore, how to maintain the antenna's stealth performance while preserving its high-gain characteristics has become an urgent problem to be solved in the current antenna design field. Summary of the Invention

[0006] To address the technical problem that the RCS reduction methods described above cannot maintain the antenna's stealth performance while preserving its high gain characteristics, this invention proposes a liquid-reconfigurable broadband circularly polarized metasurface antenna.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A broadband circularly polarized metasurface antenna based on liquid reconfiguration includes a metal metasurface layer, a metasurface dielectric layer, a liquid layer filled with liquid, a slotted metal plate, an antenna dielectric layer, and a metal feed network stacked from the top to the bottom layer. The metal metasurface layer includes at least one metal metasurface layer unit, and each metal metasurface layer unit includes at least one metal metasurface layer subunit; Each metal metasurface layer subunit is a hexagonal ring structure with openings on a pair of parallel sides; a rectangular patch is located in the center of the hexagonal ring structure.

[0008] The opening described above is obtained by subtracting two rectangular patches from a pair of parallel sides of a hexagonal ring structure; A rectangular patch is provided in the middle of the hexagonal ring structure. The long side of the rectangular patch is parallel to the side of the hexagonal ring structure where there is an opening.

[0009] Each metal metasurface layer subunit corresponds to a metasurface dielectric layer subunit. The surface of each metasurface dielectric layer subunit is a rectangular surface. Taking one side of the rectangular surface as a reference line, the acute angle formed by connecting the extension line of the opening side on the hexagonal ring structure with the reference line is 45 degrees.

[0010] One side of the metasurface dielectric layer subunit is a metal metasurface layer subunit, and the other side is a liquid layer subunit for filling liquid. The liquid layer subunit for filling liquid consists of a first PDMS dielectric layer, a liquid layer, and a second PDMS dielectric layer from one side to the other. A cavity for accommodating the liquid layer is formed between the first PDMS dielectric layer and the second PDMS dielectric layer. The aforementioned cavity includes a cross-shaped liquid channel, which divides the liquid layer subunit into four regions on a plane. The four regions are divided into a first region, a second region, a third region, and a fourth region in a clockwise or counterclockwise direction. A liquid receiving cavity with a square cross-section is provided in the first region and the third region or the second region and the fourth region. The aforementioned cross-shaped liquid channel is tightly connected / communicated with the square liquid receiving cavity.

[0011] If the square liquid-containing cavity in the liquid layer subunit for adding liquid is located in the second region and the fourth region, then the vertical projection of the opening edge of the hexagonal ring structure in the corresponding metal metasurface subunit onto the plane where the corresponding liquid layer is located falls in the first region and the third region. If the square liquid-containing cavity in the liquid layer subunit for adding liquid is located in the first region and the third region, then the vertical projection of the opening edge of the hexagonal ring structure in the corresponding metal metasurface subunit onto the plane where the corresponding liquid layer is located falls in the second region and the fourth region.

[0012] The aforementioned metal metasurface layer comprises four metal metasurface layer units, each of which includes four metal metasurface layer sub-units arranged in a consistent manner; the arrangement angles of the metal metasurface layer sub-units in adjacent metal metasurface layer units differ by 90 degrees.

[0013] The slotted metal plate consists of four sets of unit structures, with a slot opened in each set of unit structures, and the slots of adjacent sets of unit structures are perpendicular to each other. The metal-fed network uses three Wilkinson power dividers. The input of the first Wilkinson power divider is connected to the side-fed waveguide port, and the output of the first Wilkinson power divider is connected to the input of the second and third Wilkinson power dividers respectively. The outputs of the second and third Wilkinson power dividers are four output ports. The electromagnetic waves output from the four output ports radiate out from the gaps between the slotted metal plates and couple through the gaps to the liquid layer filled with liquid, the metasurface dielectric layer, and the metal metasurface layer. The metal metasurface layer and the liquid layer filled with liquid modulate these electromagnetic waves to further optimize the antenna's radiation performance, improve gain, and reduce sidelobe levels.

[0014] The metal metasurface layer, slotted metal plate, and metal power supply network are made of copper with a thickness of 0.03-0.04 mm. Both the metasurface dielectric layer and the antenna dielectric layer are F4B dielectric layers with a dielectric constant of 2.2 and a loss tangent of 0.001. The thickness of the metasurface dielectric layer is 2.8-3 mm, and the thickness of the antenna dielectric layer is 0.5-0.6 mm. The length and width are 62-63 mm. In the unit structure of the metal metasurface layer, the rectangular patch has a length of 4.3-4.5 mm and a width of 1.9-2.1 mm.

[0015] The PDMS dielectric layer has a dielectric constant of 2.72, a loss tangent of 0.0027, a thickness of 1.4-1.6 mm, a length of 62-63 mm, and a width of 62-63 mm; the thickness of the added liquid is 0.4-0.6 mm; the liquid channel is 15-16 mm long and 0.8-1.2 mm wide, with a diagonal square side length of 4.8-5.2 mm. The gaps in the slotted metal plate are 21-23mm long and 2.5-2.7mm wide.

[0016] The aforementioned application areas / scenarios of liquid-based reconfigurable broadband circularly polarized metasurface antennas include satellite communications, circularly polarized anti-interference signal transmission, and electromagnetic stealth platforms.

[0017] Compared with the prior art, the present invention has the following technical effects: 1) This invention designs a novel metasurface structure, innovatively combining a liquid layer and a metallic metasurface for use in antenna array design. Rotating a 2×2 liquid-based metasurface unit structure into four groups to form an integral liquid-based metasurface structure, which is then loaded onto the antenna array, achieves excellent circular polarization radiation performance and effectively reduces the antenna's RCS. Compared to a feed antenna, the metallic metasurface-loaded antenna exhibits improved functionality across all aspects, with the gain increasing from 7.8 dBic to 11.1 dBic, and the axial ratio of circular polarization performance improving from above 3 dB to below 3 dB, resulting in an axial ratio bandwidth of 7.2-9.6 GHz below 3 dB. Through the innovative combination of the water layer and the metallic metasurface layer, the antenna operates in scattering mode, expanding the reduced range of the water-based metasurface antenna from 11-15 GHz for metallic metasurface antennas to 6-16.2 GHz. Switching the liquid to ethanol converts the antenna to radiation mode, achieving a maximum gain of 10.9 dBic and widening the axial ratio bandwidth to 6.9-10.6 GHz.

[0018] 2) The antenna provided by this invention has a reconfigurable function, which can be switched by injecting different liquids. It can effectively reduce radar detectability both within and outside its operating frequency band, thereby improving the stealth performance of the entire system; its circular polarization radiation advantage allows it to accept antennas of arbitrary linear polarization, effectively ensuring antenna interaction efficiency. It has significant application value in satellite communication systems. Attached Figure Description

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 This is a three-dimensional schematic diagram of a liquid-based metasurface unit structure. Figure 2 A planar view of a metallic metasurface; Figure 3 This is a planar view of the liquid layer; Figure 4 This is a schematic diagram of a metal-fed network; Figure 5 This is a schematic diagram of the overall structure of a metallic metasurface; Figure 6 This is a schematic diagram of the overall three-dimensional structure of the antenna; Figure 7 This is a front view of the metallic metasurface of the antenna physical model; Figure 8 The physical model of the antenna includes the liquid layer structure and the slotted ground plane; Figure 9 This is a physical model of the antenna feed antenna structure. Figure 10 For metallic metasurface antennas and feed antennas S 11 Simulation curves; Figure 11Simulation curves for the gain of the metallic metasurface antenna and the feed antenna; Figure 12 Antennas with different liquid layers loaded on a metallic metasurface layer 11 Simulation curves; Figure 13 Simulation comparison curves of axial ratio for feed antenna, metallic metasurface antenna, water-based metasurface antenna, and ethanol-based metasurface antenna; Figure 14 The gain simulation comparison curves of the feed antenna, the metallic metasurface antenna, the water-based metasurface antenna, and the ethanol-based metasurface antenna are shown. Figure 15 Simulated and measured radiation patterns of an ethanol-based metasurface antenna at 8 GHz; Figure 16 Simulated and measured radiation patterns of an ethanol-based metasurface antenna at 8.7 GHz; Figure 17 Comparison of RCS reduction for feed antenna, metallic metasurface antenna, water-based metasurface antenna, and ethanol-based metasurface antenna; Figure 18 Three-dimensional scattering patterns of the feed antenna, water-based metasurface antenna, and ethanol-based metasurface antenna at 11 GHz and 15 GHz; Figure 19 S for an ethanol-based metasurface antenna with ls = 20-24 mm 11 Simulation curves; Figure 20 Gain simulation curves for an ethanol-based metasurface antenna with ls = 20-24 mm; Figure 21 Figures (a) and (b) show actual microwave anechoic chamber radiation performance testing scenarios, while figures (c) and (d) show horn antenna plane wave scattering performance testing scenarios. Figure 22 RCS reduction for simulation and testing of water-based metasurface antennas; Figure 23 RCS reduction for simulation and testing of ethanol-based metasurface antennas; Figure 24 S for simulation and testing of metallic metasurface antennas and feed antennas 11 curve; Figure 25 S for simulation and testing of water-based metasurface antennas and ethanol-based metasurface antennas 11 curve. Detailed Implementation

[0020] A broadband circularly polarized metasurface antenna based on liquid reconfiguration includes a metal metasurface layer, a metasurface dielectric layer, a liquid layer filled with liquid, a slotted metal plate, an antenna dielectric layer, and a metal feed network stacked from the top to the bottom layer. The metal metasurface layer includes at least one metal metasurface layer unit, and each metal metasurface layer unit includes at least one metal metasurface layer subunit; Each metal metasurface layer subunit is a hexagonal ring structure with openings on a pair of parallel sides; a rectangular patch is located in the center of the hexagonal ring structure.

[0021] The opening is obtained by subtracting two rectangular patches from a pair of parallel sides of a hexagonal ring structure; A rectangular patch is provided in the middle of the hexagonal ring structure. The long side of the rectangular patch is parallel to the side of the hexagonal ring structure where there is an opening.

[0022] Each metal metasurface layer subunit corresponds to a metasurface dielectric layer subunit. The surface of each metasurface dielectric layer subunit is a rectangular surface. Taking one side of the rectangular surface as a reference line, the acute angle formed by connecting the extension line of the opening side on the hexagonal ring structure with the reference line is 45 degrees.

[0023] One side of the metasurface dielectric layer subunit is a metal metasurface layer subunit, and the other side is a liquid layer subunit for filling liquid. The liquid layer subunit for filling liquid consists of a first PDMS dielectric layer, a liquid layer, and a second PDMS dielectric layer from one side to the other. A cavity for accommodating the liquid layer is formed between the first PDMS dielectric layer and the second PDMS dielectric layer. The cavity includes a cross-shaped liquid channel, which divides the liquid layer subunit into four regions on the plane. The four regions are divided into a first region, a second region, a third region, and a fourth region in a clockwise or counterclockwise direction. A liquid receiving cavity with a square cross-section is provided in the first region and the third region or the second region and the fourth region. The cross-shaped liquid channel is tightly connected / communicated with the square liquid receiving cavity.

[0024] If the square liquid-containing cavity in the liquid layer subunit for adding liquid is located in the second region and the fourth region, then the vertical projection of the opening edge of the hexagonal ring structure in the corresponding metal metasurface subunit onto the plane where the corresponding liquid layer is located falls in the first region and the third region. If the square liquid-containing cavity in the liquid layer subunit for adding liquid is located in the first region and the third region, then the vertical projection of the opening edge of the hexagonal ring structure in the corresponding metal metasurface subunit onto the plane where the corresponding liquid layer is located falls in the second region and the fourth region.

[0025] The metal metasurface layer comprises four metal metasurface layer units, each of which comprises four metal metasurface layer sub-units arranged in the same manner; the metal metasurface layer sub-units in adjacent metal metasurface layer units are arranged at angles that differ by 90 degrees.

[0026] The slotted metal plate consists of four sets of unit structures, with a slot opened in each set of unit structures, and the slots of adjacent sets of unit structures are perpendicular to each other. The metal-fed network uses three Wilkinson power dividers. The input of the first Wilkinson power divider is connected to the side-fed waveguide port, and the output of the first Wilkinson power divider is connected to the input of the second and third Wilkinson power dividers respectively. The outputs of the second and third Wilkinson power dividers are four output ports. The electromagnetic waves output from the four output ports radiate out from the gaps between the slotted metal plates and couple through the gaps to the liquid layer filled with liquid, the metasurface dielectric layer, and the metal metasurface layer. The metal metasurface layer and the liquid layer filled with liquid modulate these electromagnetic waves to further optimize the antenna's radiation performance, improve gain, and reduce sidelobe levels.

[0027] The metal metasurface layer, slotted metal plate, and metal power supply network are made of copper with a thickness of 0.03-0.04 mm. Both the metasurface dielectric layer and the antenna dielectric layer are F4B dielectric layers with a dielectric constant of 2.2 and a loss tangent of 0.001. The thickness of the metasurface dielectric layer is 2.8-3 mm, and the thickness of the antenna dielectric layer is 0.5-0.6 mm. The length and width are 62-63 mm. In the unit structure of the metal metasurface layer, the rectangular patch has a length of 4.3-4.5 mm and a width of 1.9-2.1 mm.

[0028] The PDMS dielectric layer has a dielectric constant of 2.72, a loss tangent of 0.0027, a thickness of 1.4-1.6 mm, a length of 62-63 mm, and a width of 62-63 mm; the thickness of the added liquid is 0.4-0.6 mm; the liquid channel is 15-16 mm long and 0.8-1.2 mm wide, with a diagonal square side length of 4.8-5.2 mm. The gaps in the slotted metal plate are 21-23mm long and 2.5-2.7mm wide.

[0029] The application areas / scenarios of the liquid-based reconfigurable broadband circularly polarized metasurface antenna include satellite communication, circularly polarized anti-interference signal transmission, and electromagnetic stealth platforms.

[0030] Example: like Figures 1-6As shown, the liquid-reconfigurable broadband circularly polarized metasurface antenna provided in this embodiment includes, from top to bottom, a metal patch layer, a metasurface dielectric layer, a liquid layer for filling with liquid, a slotted metal plate, an antenna dielectric layer, and a metal feed network; wherein the metal patch layer is composed of four groups of 2×2 arranged units rotated together, each unit structure being an open hexagonal ring placed at a 45° angle and arranged non-contactly with the central rectangular patch; the liquid layer for filling with liquid includes, from top to bottom, PDMS dielectric-liquid-PDMS dielectric, with the liquid being two diagonally opposite squares connected to other units through rectangular channels. Figure 2 The unit structure shown has a period p = 15.6 mm. Multiple units are arranged periodically and closely. The overall structural diagram is shown below. Figure 6 As shown.

[0031] The top-layer metal metasurface unit consists of an open hexagonal ring placed at a 45° angle, with two rectangles of length *a* and width *b* in the center. The open hexagonal ring is formed by chamfering the four corners of a rectangle of width *w1* and length *l1* to create hexagonal patches of length *w1 / 2*, subtracting the four corners of a rectangle of width *w2* and length *l2* to create hexagonal patches, and then subtracting two rectangles of length *a* and width *b*. The planar diagram of the top-layer metal metasurface unit is shown below. Figure 2 As shown. Figure 3 The liquid portion shown consists of two diagonally opposite squares of length c and a rectangular channel of width g.

[0032] Preferably, the metal metasurface units and liquid unit structures are arranged in a 2×2 pattern as a group, and one group is rotated 90 degrees to obtain four groups, which constitute the entire liquid-based metasurface.

[0033] Preferably, the metal metasurface layer, the slotted metal plate, and the metal feed network are made of copper with a thickness of 0.03-0.04 mm; more preferably, the thickness is 0.035 mm. Both the metasurface dielectric layer and the antenna dielectric layer are F4B dielectric layers with a dielectric constant of 2.2 and a loss tangent of 0.001. The metasurface dielectric layer has a thickness of 2.8-3 mm, more preferably hp=3 mm; the antenna dielectric layer has a thickness of 0.5-0.6 mm, more preferably 0.5 mm. The liquid layer for filling is a PDMS dielectric layer with a dielectric constant of 2.72, a loss tangent of 0.0027, and a thickness of 1.4-1.6 mm, more preferably h1=1 mm and h2=0.5 mm; the thickness of the filled liquid is 0.4-0.6 mm, more preferably 0.5 mm; the overall antenna model is 62-63 mm long, 62-63 mm wide, and 5-5.2 mm high, more preferably 62.4 mm long, 62.4 mm wide, and 5.105 mm high.

[0034] Preferably, the slotted metal plate is composed of four sets of unit structures, each set of unit structures has a slot, and the slots of two adjacent sets of unit structures are perpendicular to each other; the slot is 21-23mm long and 2.5-2.7mm wide, more preferably 22mm long and 2.6mm wide.

[0035] Preferably, the electromagnetic waves output from the Wilkinson feed network antenna at its four output ports radiate through the gaps between the slotted metal plates and couple to a liquid-based metasurface. These electromagnetic waves are modulated by the metal metasurface structure and the liquid layer, further optimizing the antenna's radiation performance, increasing gain, and reducing sidelobe levels. Three Wilkinson power dividers output the signal from one input port to all four ports, with side-feed waveguide ports located at the input ports. The two output terminals of the Wilkinson power dividers are connected by 100Ω resistors.

[0036] Figure 4 This displays the specific dimensions of the microstrip lines in each branch of the Wilkinson feeder network. Figure 5 This is a front view of the antenna; the three-dimensional structure of each layer is as follows: Figure 6 As shown in Table 1, the specific parameter values ​​for the microstrip line in the power supply network are provided.

[0037] Table 1

[0038] To analyze the impact of metallic metasurface structures on antenna performance, this invention analyzes antennas with metallic metasurface layers and Wilkinson feed network antennas. Without a metasurface, the Si of the Wilkinson feed network antenna is... 11 The curve shows that the impedance bandwidth at -10dB has two frequency bands: 6.8-7.5GHz and 7.8-11GHz. Figure 10 As shown by the red curve, the antenna with the added metallic metasurface has two almost identical impedance bandwidths below -10dB, but with greater depth. This is more concentrated in the 8-11GHz range. Figure 10 The black curve represents the shift in antenna operating frequency band towards lower frequencies by adding a metasurface. The gain comparison diagram is provided by... Figure 11 It is known that the Wilkinson feed network antenna without a metallic metasurface achieves a maximum gain of 7.8 dBic at 10 GHz. Adding a metallic metasurface increases the maximum gain by 3.3 dBic, bringing the maximum gain of the metallic metasurface antenna to 11.1 dBic. The metallic metasurface, as a radiating structure, can effectively improve antenna gain.

[0039] To analyze the effects of loading different liquid layers on metallic metasurface antennas, this invention conducted simulation analyses on loading aqueous and ethanol solutions. The S values ​​for loading water and ethanol solutions... 11 The curve is from Figure 12As can be seen, good performance is maintained in the 6.8-10.5 GHz range. Simulation analysis was also performed on the axial ratio and gain, such as... Figure 13 and Figure 14 As shown. In Figure 13 The axial ratio bandwidth with the liquid layer is approximately 6.9-10.6 GHz, representing a 1.3 dB improvement compared to the unloaded metallic metasurface antenna (7.2-9.6 GHz). Adding an aqueous solution to the liquid layer causes the gain to drop to 9 dBic. To improve this, replacing the aqueous solution with an ethanol solution increases the gain to 10.9 dBic. Figure 15 and Figure 16 The radiation patterns of the metasurface antenna loaded with ethanol solution at 8 GHz and 8.7 GHz are shown. The antenna mainly operates in right-hand circularly polarized (RHCP) mode, with a gain significantly higher than that of the left-hand circularly polarized (LHCP) component. The measured radiation patterns in the main lobe region are in high agreement with the simulation results, and both side lobes are more than 15 dB lower than the main lobe, demonstrating excellent sidelobe suppression and high directivity. Overall, the antenna exhibits significant directional radiation characteristics in both operating frequency bands and possesses excellent beam focusing capabilities.

[0040] The proposed liquid-based metasurface antenna model has the function of RCS reduction. The simulation results of the monostatic RCS of the metal metasurface antenna, water-based metasurface antenna, ethanol-based metasurface antenna and reference feed antenna without the loading of liquid layer are compared. Figure 17 Three-dimensional scattering field maps of different antennas are shown. The scattering map of the feed antenna exhibits a focused main lobe, indicating a concentrated distribution of electromagnetic energy. This demonstrates that traditional feed antenna designs inherently lack electromagnetic scattering control capabilities. To overcome this limitation and verify the electromagnetic scattering control capabilities of metasurface materials, this invention designs a water-based metasurface antenna for comparative research. The sidelobe level of the water-based metasurface is significantly reduced, fully verifying its ability to control electromagnetic waves. The significant reduction at 15 GHz is mainly due to the inherent electromagnetic absorption characteristics of water, highlighting the dominant role of water in high-frequency electromagnetic wave absorption. Figure 18 The reduction in RCS is shown. Under plane electromagnetic wave incidence, the ethanol-based metasurface antenna exhibits an RCS reduction bandwidth of 6.2-15.8 GHz, while the water-based metasurface antenna shows an average reduction of over 6 dB within the 6-16.2 GHz range, demonstrating the best performance. Compared to the metal metasurface antenna's reduction range of 11-15 GHz, this is a significant improvement. In the low-frequency band, the scattering characteristics of the two liquid metasurface antennas are similar; however, in the high-frequency band, the water-based antenna exhibits superior RCS suppression performance compared to the ethanol-based antenna. Figure 10 andFigure 12 As shown, the advantages of ethanol-based antennas are mainly reflected in their radiation performance, with higher gain; while water-based antennas have better scattering performance, exhibiting a wider bandwidth and stronger RCS suppression effect in the high-frequency band.

[0041] This invention proposes a liquid-reconfigurable broadband circularly polarized metasurface antenna, achieving both in-band and out-of-band radar cross-section suppression and high-gain circularly polarized radiation. The metasurface structure is composed of a metallic metasurface and replaceable liquid layers (ethanol / water), combined with a Wilkinson power divider-based feed network to form a complete reconfigurable antenna. By changing the liquid medium, the antenna can switch between radiation-controlled and scattering-controlled modes: the ethanol-based configuration achieves a 47% relative impedance bandwidth and a maximum gain of 10.9 dBic in the 8.5 GHz band; the water-based configuration achieves monostatic RCS suppression exceeding 6 dBsm in the 6.0-16.2 GHz band, covering both in-band and out-of-band suppression. At 15.1 GHz, the maximum RCS suppression reaches 25 dBsm. To meet the needs of different application scenarios, such as those requiring high gain or prioritizing strong scattering suppression, the proposed liquid metasurface antenna can be reconfigured by switching the injected fluid (ethanol / water), utilizing its unique electromagnetic properties to achieve optimal performance adaptation. More importantly, this state switching does not require complex electronic devices; it can be achieved simply by changing the liquid, providing a new technological path for modern communication systems.

[0042] The influence of the metal ground plane gap length ls on the reflection coefficient of this antenna model was investigated. With ws = 2.6 mm selected, ls was increased from 20 mm to 24 mm in 2 mm increments. Figure 19 As can be seen, in order to ensure better working bandwidth, S is required. 11 The curve should be below -10dB, and the simulated curve only meets the requirement when ls = 22mm. At this point, the impedance bandwidth reaches 6.8-10.8GHz. Figure 20 The antenna gain was compared under three conditions. The highest antenna gain was greater when ls=22mm and ls=24mm than when ls=20mm. Therefore, based on comprehensive analysis, the optimal metal ground plane gap length ls was selected as 22mm.

[0043] To verify the feasibility of the simulation experiment, the proposed antenna was subjected to actual measurement and analysis. The actual measurement environment was as follows: Figure 21 As shown. Figure 21 (a)(b) Test the antenna's radiation performance; (c)(d) Test the antenna's scattering performance. The experiment uses a horn antenna to emit electromagnetic waves to measure the scattering performance, i.e., RCS reduction, of a metasurface antenna loaded with a liquid layer. The test results are as follows: Figure 22 and Figure 23As shown in the figure. In the actual measurement, there was signal interference error, which caused abrupt changes. However, the overall reduction trend was consistent with the simulation results. Figure 22 The figure in the middle is a comparison between the measured and simulated RCS reduction of the water-based metasurface antenna. The measured RCS reduction frequency band (greater than 6dB) is in the range of 6.1-7GHz and 7.9-17.5GHz. Figure 23 The figure in the middle shows a comparison between the measured and simulated RCS reduction of the ethanol-based metasurface antenna. The measured RCS reduction bands are 6-7 GHz, 7.1-7.4 GHz, and 7.8-14 GHz. The above test results demonstrate good scattering performance, and the antenna can reduce its own radar detectability.

[0044] By measuring the radiation performance of the antenna, this invention obtains the following: Figure 24 and Figure 25 S shown 11 curve. Figure 24 The measured metallic metasurface antenna S 11 The bandwidth less than -10dB is 6.8-10.9GHz, and the feed antenna bandwidth is also 6.8-10GHz, roughly consistent with the simulated bandwidth. In the actual measurement of the metallic metasurface antenna, the first resonance peak occurs around 6.9GHz, while the simulation shows it around 7GHz; the second resonance peak is measured at 8GHz, while the simulation shows it at 8.2GHz, with the measured result shifting to the left compared to the simulation result. Both the measured and simulated results for the feed antenna show three distinct resonance peaks, with the measured peak frequency shifting slightly to the left. Figure 25 Measured Ethanol-based Metasurface Antenna and Water-based Metasurface Antenna S 11 The bandwidths less than -10dB are 6.8-10GHz and 6.85-10.2GHz, respectively, which are largely consistent with the simulation results, with slight differences in the resonance peak depth. The factors causing these errors are due to the inability of the liquid layer fabrication process to achieve the same precision as the simulation model, as well as experimental operational errors, which can be ignored.

[0045] In summary, this invention proposes a liquid-reconfigurable broadband circularly polarized metasurface antenna. This device can be used for satellite communication, exhibits good circular polarization performance, and can reduce RCS, thereby reducing radar wave detectability and improving its stealth effect. It has broad application prospects in stealth communication and satellite communication.

Claims

1. A broadband circularly polarized metasurface antenna based on liquid reconfigurability, characterized in that: It includes a metal metasurface layer, a metasurface dielectric layer, a liquid layer filled with liquid, a slotted metal plate, an antenna dielectric layer, and a metal feed network stacked from top to bottom; The metal metasurface layer includes at least one metal metasurface layer unit, and each metal metasurface layer unit includes at least one metal metasurface layer subunit; Each metal metasurface layer subunit is a hexagonal ring structure with openings on a pair of parallel sides; a rectangular patch is located in the center of the hexagonal ring structure.

2. The liquid-reconfigurable broadband circularly polarized metasurface antenna according to claim 1, characterized in that, The opening is obtained by subtracting two rectangular patches from a pair of parallel sides of a hexagonal ring structure; A rectangular patch is provided in the middle of the hexagonal ring structure. It is located at the center of the ring structure, and the long side of the rectangular patch is parallel to the side of the hexagonal ring structure where there is an opening.

3. The liquid-reconfigurable broadband circularly polarized metasurface antenna according to claim 2, characterized in that, Each metal metasurface layer subunit corresponds to a metasurface dielectric layer subunit. The surface of each metasurface dielectric layer subunit is a rectangular surface. Taking one side of the rectangular surface as a reference line, the acute angle formed by connecting the extension line of the opening side on the hexagonal ring structure with the reference line is 45 degrees.

4. The liquid-reconfigurable broadband circularly polarized metasurface antenna according to any one of claims 1 to 3, characterized in that, One side of the metasurface dielectric layer subunit is a metal metasurface layer subunit, and the other side is a liquid layer subunit for filling liquid. The liquid layer subunit for filling liquid consists of a first PDMS dielectric layer, a liquid layer, and a second PDMS dielectric layer from one side to the other. A cavity for accommodating the liquid layer is formed between the first PDMS dielectric layer and the second PDMS dielectric layer. The cavity includes a cross-shaped liquid channel, which divides the liquid layer subunit into four regions on the plane. The four regions are divided into a first region, a second region, a third region, and a fourth region in a clockwise or counterclockwise direction. A liquid receiving cavity with a square cross-section is provided in the first region and the third region or the second region and the fourth region. The cross-shaped liquid channel is tightly connected / communicated with the square liquid receiving cavity.

5. The liquid-reconfigurable broadband circularly polarized metasurface antenna according to claim 4, characterized in that, If the square liquid-containing cavity in the liquid layer subunit for adding liquid is located in the second region and the fourth region, then the vertical projection of the opening edge of the hexagonal ring structure in the corresponding metal metasurface subunit onto the plane where the corresponding liquid layer is located falls in the first region and the third region. If the square liquid-containing cavity in the liquid layer subunit for adding liquid is located in the first region and the third region, then the vertical projection of the opening edge of the hexagonal ring structure in the corresponding metal metasurface subunit onto the plane where the corresponding liquid layer is located falls in the second region and the fourth region.

6. The liquid-reconfigurable broadband circularly polarized metasurface antenna according to claim 1, 2, 3, or 5, characterized in that, The metal metasurface layer comprises four metal metasurface layer units, each of which comprises four metal metasurface layer sub-units arranged in the same manner; the metal metasurface layer sub-units in adjacent metal metasurface layer units are arranged at angles that differ by 90 degrees.

7. The liquid-reconfigurable broadband circularly polarized metasurface antenna according to claim 6, characterized in that, The slotted metal plate consists of four sets of unit structures, with a slot opened in each set of unit structures, and the slots of two adjacent sets of unit structures are perpendicular to each other. The metal-fed network uses three Wilkinson power dividers. The input of the first Wilkinson power divider is connected to the side-fed waveguide port, and the output of the first Wilkinson power divider is connected to the input of the second and third Wilkinson power dividers respectively. The outputs of the second and third Wilkinson power dividers are four output ports. The electromagnetic waves output from the four output ports radiate out from the gaps between the slotted metal plates and couple through the gaps to the liquid layer filled with liquid, the metasurface dielectric layer, and the metal metasurface layer. The metal metasurface layer and the liquid layer filled with liquid modulate these electromagnetic waves to further optimize the antenna's radiation performance, improve gain, and reduce sidelobe levels.

8. The liquid-reconfigurable broadband circularly polarized metasurface antenna according to claim 1, characterized in that, The metal metasurface layer, slotted metal plate, and metal power supply network are made of copper with a thickness of 0.03-0.04 mm. Both the metasurface dielectric layer and the antenna dielectric layer are F4B dielectric layers with a dielectric constant of 2.2 and a loss tangent of 0.

001. The thickness of the metasurface dielectric layer is 2.8-3 mm, and the thickness of the antenna dielectric layer is 0.5-0.6 mm. The length and width are 62-63 mm. In the unit structure of the metal metasurface layer, the rectangular patch has a length of 4.3-4.5 mm and a width of 1.9-2.1 mm.

9. The liquid-reconfigurable broadband circularly polarized metasurface antenna according to claim 1, characterized in that, The PDMS dielectric layer has a dielectric constant of 2.72, a loss tangent of 0.0027, a thickness of 1.4-1.6 mm, a length of 62-63 mm, and a width of 62-63 mm; the thickness of the added liquid is 0.4-0.6 mm; the liquid channel is 15-16 mm long and 0.8-1.2 mm wide, with a diagonal square side length of 4.8-5.2 mm. The gaps in the slotted metal plate are 21-23mm long and 2.5-2.7mm wide.

10. The method according to claim 1, 2, 3, 5, 7, 8, or 9, characterized in that, The application areas / scenarios of the liquid-based reconfigurable broadband circularly polarized metasurface antenna include satellite communication, circularly polarized anti-interference signal transmission, and electromagnetic stealth platforms.

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