A conformal multifunctional active metasurface with high angular stability

Abstract

This invention discloses a conformal multifunctional active metasurface with high angular stability. It comprises several periodically and closely arranged unit structures. Each periodic unit structure mainly includes two metal layers, one dielectric layer, a metallized via connecting the two metal layers, and two PIN diodes. The two metal layers are etched on the upper and lower surfaces of the dielectric layer, respectively, and the two PIN diodes are embedded between the upper and lower metal layers. This invention features a simple and compact design with excellent flexibility and curvature, enabling conformal surface design. The metasurface unit is designed using a helical bending line, increasing the equivalent resonant length of the unit while maintaining the same unit size, thus increasing the equivalent inductance. It achieves polarization insensitivity and can simultaneously or independently switch between different polarization operating states, realizing both full-polarization electromagnetic switching and orthogonal polarization control functions.

Description

[Technical Field]

[0001] This invention relates to the field of electromagnetic control materials technology, specifically to a conformal multifunctional active metasurface with high angular stability. [Background Technology]

[0002] Flexible smart skin technology is a current research hotspot with broad application prospects. As an important component, conformal metasurface technology is widely used in various fields.

[0003] Metasurfaces are two-dimensional periodic array structures with bandpass or bandstop electromagnetic properties. They can selectively emit or shield electromagnetic waves in specific frequency bands. Therefore, metasurfaces are widely used in microwave absorbers, radomes, electromagnetic shielding, and other fields.

[0004] Currently, research on metasurfaces mainly focuses on planar structures. However, in practical applications, metasurfaces typically need to be designed to conform to the surface of objects. Therefore, metasurfaces need to maintain excellent flexibility and surface conformability while ensuring their performance. However, the current design of conformal metasurfaces results in large unit sizes, leading to problems such as angular instability and polarization sensitivity.

[0005] To address the aforementioned issues, it is necessary to miniaturize the metasurface unit cell structure as much as possible. Miniaturized metasurfaces allow for the placement of as many units as possible within a limited application area. When the structure conforms to a curved surface, the metasurface can maintain a stable frequency response at different oblique angles of incidence. However, current research on conformal metasurfaces mainly focuses on passive forms; once fabricated, their electromagnetic properties are difficult to alter, thus lacking flexibility in controlling electromagnetic performance.

[0006] Active metasurfaces possess reconfigurable properties, making them possible for manipulating electromagnetic waves. They typically incorporate PIN diodes or varactor diodes within the metasurface, allowing control of their electromagnetic properties through adjustment of external excitation. However, traditional active metasurfaces, which usually only offer one control function, still face many limitations. With the increasing complexity of electromagnetic environments, traditional single-function active metasurfaces can no longer meet application requirements.

[0007] In recent years, the huge demand for multifunctional and multistandard communication and radar systems has made the application of multifunctional switchable active metasurfaces more urgent. For example, in wireless communication systems, active metasurfaces with polarization manipulation can increase the degree of control freedom and provide more information transmission channels. For radar applications, multifunctional active metasurfaces can be used as multifunctional radomes with radar stealth, electromagnetic shielding and radar target feature conversion. Therefore, multifunctional active metasurfaces have received widespread attention from researchers. Although Professor Cao Qunsheng's team at Nanjing University of Aeronautics and Astronautics has proposed a variety of multifunctional active frequency selective surfaces that can realize different functions of electromagnetic switching and polarization selection, such as: [1] H.Li, Q.Cao, and Y.Wang, “A novel2-B multifunctional active frequency selective surface for LTE-2.1GHz,”IEEE Trans. Antennas Propag., vol.65, no.6, pp.3084–3092, Jun.2017. [2] J.Liang, Q.Cao, Y.Wang and Z.Wan, "A Multifunctional and Miniaturized Flexible ActiveFrequency Selective Surface," IEEE Antennas and Wireless Propagation Letters, vol.20, no.12, pp.2549-2553, Dec.2021. Chinese Invention Patent CN106329041A; Chinese Invention Patent CN112838374A. However, including the above-mentioned prior art, there are very few broadband flexible metasurface designs that achieve miniaturization of unit size while also possessing multiple electromagnetic control functions. In addition, current research on multifunctional switchable active metasurfaces mainly focuses on planar structures, while research on multifunctional active metasurfaces with conformal curved surfaces is almost non-existent. Obtaining miniaturized multifunctional active metasurfaces with excellent angular stability and polarization insensitivity under conformal active metasurface structures is a significant challenge. [Summary of the Invention]

[0008] To address the shortcomings of existing technologies, the present invention aims to propose a miniaturized conformal multifunctional active metasurface structure with high angular stability.

[0009] The metasurface structure is designed on a thin, flexible dielectric substrate, suitable for conformal curved surfaces. Furthermore, by independently controlling the on / off states of the PIN diodes on the upper and lower surfaces of the substrate, four different operating states and two different functions are achieved. The use of a helical structure extends the equivalent resonant length of the unit cell, achieving excellent unit miniaturization. Therefore, it exhibits excellent angular stability even within a large incident angle range of 0–80°. The metasurface structure designed in this invention is a four-arm square helical resonant structure, which is isolated in the horizontal and vertical directions, enabling polarization insensitivity or independent polarization switching control. Therefore, the uniqueness of the proposed miniaturized conformal multifunctional active metasurface structure lies in its ability to integrate four independent operating states and two different functions while achieving a conformal curved surface structure, exhibiting excellent angular stability and polarization insensitivity.

[0010] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0011] This invention provides a conformal multifunctional active metasurface with high angular stability, comprising several periodically closely arranged unit structures. Each periodic unit structure mainly includes two metal layers, one dielectric layer, a metallized via connecting the two metal layers, and two PIN diodes. The two metal layers are respectively etched on the upper and lower surfaces of the dielectric layer, and the two PIN diodes are respectively embedded between the upper and lower metal layers.

[0012] The two metal layers are specifically an upper surface metal patch and a lower surface metal patch. The upper surface metal patch has a four-armed spiral structure, consisting of four coiled curved lines. Each curved line can be obtained by rotating one of the curved lines around the unit center by 90°, 180°, or 270°, exhibiting excellent rotational symmetry.

[0013] The lower metal patch is identical to the upper metal patch, also featuring a four-arm spiral structure. Four metal bends at opposite positions on the upper and lower layers are connected by metallized vias, which are centrally symmetrically distributed. To prevent solder leakage and short circuits during diode soldering, the distance between the metallized vias and the cell center must be controlled. Therefore, the metallized vias are designed to be located at the corners of the metal bends near the cell center.

[0014] The two metal layers each contain a pair of metal pads at the center of the upper and lower surfaces of the dielectric layer. The pair of metal pads on the upper surface are printed vertically on the upper surface of the dielectric layer and electrically connected to two bent metal lines along the vertical direction for soldering PIN diodes arranged vertically. The pair of metal pads on the lower surface are printed horizontally on the lower surface of the dielectric layer and electrically connected to two bent metal lines along the horizontal direction for soldering PIN diodes arranged horizontally.

[0015] This invention further provides an array composed of the aforementioned conformal multifunctional active metasurface units with high angular stability. In this array, for PIN diodes embedded in the upper surface metal layer, several PIN diodes in the same column along the vertical direction are connected in series through metasurface units, and then aggregated through an additional feeding network, connected to the first interface V1(+) and the first interface V1(-) of the feeding network. For PIN diodes embedded in the lower surface metal layer, several PIN diodes in the same row along the horizontal direction are connected in series through metasurface units, and then aggregated through an additional feeding network, connected to the second interface V2(+) and the second interface V2(-) of the feeding network. The PIN diodes embedded in the upper and lower surface metal layers are connected in the same way, but their directions are orthogonal to each other. The PIN diodes arranged along the vertical and horizontal directions are isolated from each other and can be controlled simultaneously or independently by external excitation. By controlling the first interface V1 and the second interface V2 to provide bias voltages to the PIN diodes, the state of the metasurface units in the vertical and horizontal polarization directions can be controlled independently, thereby allowing independent modulation of two orthogonally polarized incident electromagnetic waves.

[0016] The dielectric layer is made of a flexible dielectric substrate with good flexibility and curvature, which can be used for conformal curved surfaces. The thickness is 0.1 to 0.5 mm and the dielectric constant is 2.2 to 4.4.

[0017] The flexible dielectric substrate includes: polytetrafluoroethylene high-frequency microwave dielectric substrate, PDMS (polydimethylsiloxane) dielectric substrate, PI (polyimide) dielectric substrate, PET (polyethylene terephthalate) dielectric substrate, or Polystyrene dielectric substrate.

[0018] The diode in question is a PIN diode with the smallest package, TSLP-2-19.

[0019] The present invention further provides a control method for the conformal multifunctional active metasurface array with high angular stability, which is achieved by controlling the "on / off" state of PIN diodes embedded in the upper and lower metal surfaces.

[0020] In each metasurface unit cell, two PIN diodes are positioned between the upper and lower metal surfaces of each cell. They are orthogonal to each other, connecting two perpendicular curved metal strips, each responsible for modulating electromagnetic waves of two different polarizations. When the PIN diodes are in the ON state, the metasurface unit cell can be equivalent to a hybrid parallel LC resonant circuit, achieving a bandpass frequency response, and the electromagnetic wave is transmitted. Conversely, when the PIN diodes are in the OFF state, the metasurface unit cell can be equivalent to a hybrid series LC resonant circuit, achieving a bandstop frequency response, and the electromagnetic wave is reflected. Most importantly, by independently controlling the ON / OFF states of the two PIN diodes on the upper and lower metal layers of the control unit, the bandstop / transmission electromagnetic characteristics of the two orthogonally polarized regions can be independently switched.

[0021] Furthermore, in the control method described above, each metasurface unit contains "0" and "1" digital states in both the vertical and horizontal polarization directions, and these digital states are independently adjustable, possessing a two-bit encoding function. The on / off states of the diodes under vertical and horizontal polarization are encoded using binary code "ij". "i" represents the on / off state of the PIN diode embedded in the upper metal surface, and "j" represents the on / off state of the PIN diode embedded in the lower metal surface. A binary bit 0 represents the unbiased off state of the PIN diode, and a binary bit 1 represents the forward-biased on state of the PIN diode. Therefore, four different encoding states "00", "11", "01", and "10" can be implemented. A topology interface circuit is used to provide bias voltage to the PIN diodes on the metasurface unit, causing the metasurface unit to exhibit different electromagnetic characteristics in the vertical and horizontal polarization directions. Therefore, four different operating states can be implemented: dual-polarization bandstop, dual-polarization bandpass, TM polarization wave selection, and TE polarization wave selection, thereby enabling two different control functions: full-polarization electromagnetic switching and orthogonal polarization control.

[0022] The conformal multifunctional active metasurface proposed in this invention has great potential for multifunctional device applications in radar and wireless communication systems.

[0023] The beneficial effects of this invention are as follows:

[0024] (1) The multifunctional active metasurface is designed on a thin flexible dielectric substrate, which has good flexibility and bending, and can realize the conformal application of curved surfaces.

[0025] (2) The metasurface unit is designed with a spiral bending line, which increases the equivalent resonant length of the unit without changing the unit size, thus increasing the equivalent inductance. Furthermore, the spiral structure allows for interaction between different bent metal strips, generating longer parallel coupling lines and forming a larger equivalent capacitance. Therefore, the physical size of the unit can be significantly reduced, ultimately making it easier to achieve excellent angular stability. Under the conformal structure, stable switchable characteristics can be achieved for both TE and TM polarizations within a large incident angle range of 0–80°.

[0026] (3) The four-armed spiral unit structure can be obtained by rotating a curved line around the unit center by 90°, 180°, and 270°. Therefore, the entire unit has excellent rotational symmetry, thus achieving polarization insensitivity. Moreover, the corresponding metal strips of different layers are connected through metallized vias, further improving the polarization insensitivity.

[0027] (4) The unit structure is designed to be electrically connected to each other to realize the series feeding of PIN diodes. The unit itself is used as the bias feed line of the PIN diodes, avoiding the negative impact of the additional feeding network on the active metasurface. Moreover, by controlling the bias voltage of the bias feed line on each layer, the operating states of different polarizations can be switched simultaneously or independently, thereby realizing the two functions of full polarization electromagnetic switching and orthogonal polarization control.

[0028] (5) The conformal multifunctional active metasurface proposed in this invention achieves a conformal structure while possessing advantages such as multiple functions, high angular stability, polarization insensitivity, and broadband transmission and reflection electromagnetic switching characteristics. Furthermore, it is simple to design and compact in structure, showing great potential for future applications in multifunctional devices in radar and wireless communication systems. [Attached Image Description]

[0029] Figure 1a -c The conformal multifunctional active metasurface unit structure proposed in this invention, wherein Figure 1a This is a perspective view of a metasurface unit. Figure 1b The upper metal surface of the metasurface unit. Figure 1c It is the lower metal surface of the metasurface unit.

[0030] Figure 2 A schematic diagram of the conformal multifunctional active metasurface array and its bias feeding system proposed in this invention.

[0031] Figure 3 A schematic diagram of the conformal fabrication of the conformal multifunctional active metasurface proposed in this invention.

[0032] Figure 4a-d The transmission coefficients of the conformal multifunctional active metasurface proposed in this invention, measured under different incident angles and polarizations, for four operating states, wherein... Figure 4a It is in the "00" state. Figure 4b "11" status, Figure 4c "01" state, Figure 4d "10" status.

Detailed Implementation Methods

[0033] To better understand the present invention, the technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0034] To meet the conformal application requirements of active metasurfaces in multifunctional radomes and wireless communication devices, there is an urgent need to design a flexible, multifunctional active metasurface. For conformal active metasurfaces, most of their region falls within the range of oblique incidence at different angles. Therefore, the performance of a conformal active metasurface depends on its good angular stability and polarization insensitivity.

[0035] like Figure 1a As shown, this invention designs a miniaturized flexible multifunctional active metasurface with high angular stability and polarization insensitivity. The specific implementation of the flexible multifunctional active metasurface structure includes several periodically closely arranged unit structures. Each periodic unit structure mainly includes a dielectric layer 1, two metal layers 2 and 3, a metallized via 5 connecting the two metal layers, and two PIN diodes 4. The two metal layers are respectively etched on the upper and lower surfaces of the dielectric layer, and the two PIN diodes are embedded between the upper and lower metal layers.

[0036] like Figure 1b and Figure 1c As shown, the multifunctional active metasurface structure comprises two metal layers, mainly consisting of an upper surface metal patch and a lower surface metal patch. The upper surface metal patch is a four-armed spiral structure composed of four coiled curved lines. Using a spiral curved line design for the metasurface unit increases the equivalent resonant length of the unit while maintaining the same unit size, thus increasing the equivalent inductance. Furthermore, the spiral structure allows for interaction between the different curved metal strips, generating longer parallel coupling lines and forming a larger equivalent capacitance. Therefore, the physical size of the unit can be significantly reduced, with a miniaturized unit size reaching 0.082λ0 × 0.082λ0 × 0.005λ0 (λ0 being the wavelength corresponding to the center frequency). The unit size ultimately allows for easier achievement of excellent angular stability.

[0037] Each bend can be obtained by rotating one of the bends around the cell center by 90°, 180°, or 270°, exhibiting excellent rotational symmetry. Therefore, polarization insensitivity is achieved. The lower and upper metal patches are identical, also featuring a four-armed spiral structure. The four metal bends in opposite positions on the upper and lower layers are connected by 0.2mm diameter metallized vias, which are centrally symmetrically distributed, further enhancing polarization insensitivity. To prevent solder leakage and short circuits during diode soldering, the distance between the metallized vias and the cell center must be controlled; therefore, the metallized vias are designed to be located near the corners of the metal bends close to the cell center.

[0038] The two metal layers each contain a pair of metal pads at the center of their respective upper and lower surfaces. The pair of metal pads on the upper surface are printed vertically on the upper surface of the dielectric layer and electrically connected to two bent metal lines along the vertical direction for soldering PIN diodes arranged vertically. The pair of metal pads on the lower surface are printed horizontally on the lower surface of the dielectric layer and electrically connected to two bent metal lines along the horizontal direction for soldering PIN diodes arranged horizontally.

[0039] The dielectric layer is made of F4BM polytetrafluoroethylene high-frequency microwave board with a dielectric constant of 2.2, a loss tangent of 0.0007, and a thickness of 0.25mm. It has excellent flexibility and bending ability and can be used for conformal curved surfaces.

[0040] The present invention further provides a control method for the conformal multifunctional active metasurface with high angular stability, which is achieved by controlling the "on / off" state of PIN diodes embedded in the upper and lower metal surfaces.

[0041] In each metasurface unit cell, two PIN diodes are positioned between the upper and lower metal surfaces of each cell. They are orthogonal to each other, connecting two perpendicular curved metal strips, each responsible for modulating electromagnetic waves of two different polarizations. When the PIN diodes are in the ON state, the metasurface unit cell can be equivalent to a hybrid parallel LC resonant circuit, achieving a bandpass frequency response, and the electromagnetic wave is transmitted. Conversely, when the PIN diodes are in the OFF state, the metasurface unit cell can be equivalent to a hybrid series LC resonant circuit, achieving a bandstop frequency response, and the electromagnetic wave is reflected. Most importantly, by independently controlling the ON / OFF states of the two PIN diodes on the upper and lower metal layers of the control unit, the bandstop / transmission electromagnetic characteristics of the two orthogonally polarized regions can be independently switched.

[0042] The on / off states of diodes under TE and TM polarization are encoded using binary code "ij". "i" represents the on / off state of the PIN diode embedded in the upper metal surface, and "j" represents the on / off state of the PIN diode embedded in the lower metal surface. A binary bit 0 indicates the unbiased off state of the PIN diode, and a binary bit 1 indicates the forward-biased on state. Therefore, four different encoding states "00", "11", "01", and "10" can be implemented. This corresponds to four different operating states: dual-polarization bandstop, dual-polarization bandpass, TM polarization wave selection, and TE polarization wave selection. Furthermore, two different control functions can be implemented: full-polarization electromagnetic switching and quadrature polarization control.

[0043] The geometry of the proposed conformal multifunctional active metasurface was designed using CST Microwave Studio software. The proposed element's geometric parameters are: m x =4.1mm, l1=2.98mm, l2=2.98mm, l3=1.6mm, g1=0.34mm, g2=0.34mm, l g =0.5mm, w g =0.3mm, l w =0.35mm, D v =0.2mm, D f =1.64mm, h=0.25mm, w1=0.22mm.

[0044] Figure 2 This diagram illustrates the conformal multifunctional active metasurface array and its bias feeding system proposed in this invention. In the active metasurface array structure, for the PIN diodes embedded in the upper surface metal layer, several PIN diodes in the same column are connected in series, and PIN diodes in different columns are connected in parallel, ultimately achieving overall switching control through an additional feeding network. For the PIN diodes embedded in the lower surface metal layer, their connection method is the same as that of the PIN diodes embedded in the upper surface metal layer, and their directions are orthogonal to each other. The PIN diodes arranged vertically and horizontally in the upper and lower layers are isolated from each other and can be controlled simultaneously or independently by external excitation.

[0045] The present invention further provides an array composed of the above-mentioned conformal multifunctional active metasurface with high angular stability. In the array, the cell structure is designed to be electrically connected to each other to realize series feeding of PIN diodes. The cell itself is used as the bias feed line of the PIN diode, avoiding the negative impact of additional feeding network on the active metasurface. In addition, two additional bias lines 6 (V1(+), V1(-) and V2(+), V2(-)) are arranged on both sides of the upper and lower metal layers to provide bias voltages for the PIN diodes in the vertical and horizontal directions. The PIN diodes arranged in the vertical and horizontal directions are isolated from each other and can be controlled simultaneously or independently by external excitation. Two types of lumped inductors 7 are embedded between the external bias lines and the active metasurface array to isolate DC and induced current (RF). By providing bias voltages to the PIN diodes through control interfaces I and I2, the state of the metasurface unit in the vertical and horizontal polarization directions can be controlled independently, and the incident electromagnetic waves of two orthogonal polarizations can be independently regulated, thereby realizing both full polarization electromagnetic switching and orthogonal polarization control functions.

[0046] like Figure 3 As shown, to further verify the performance of the design, the proposed conformal multifunctional active metasurface was fabricated and tested. Metal patches were printed on an F4BM flexible dielectric substrate with a thickness of only 0.25 mm. The fabricated flexible multifunctional active metasurface has a total size of 263 mm × 263 mm and consists of 60 × 60 units. Surface mount technology was used to solder pin PIN diodes and other lumped components. The PIN diodes used were the BAR64-02 model with the smallest package, TSLP-2-19. In addition, two lumped inductors, AIMC-0603-2N2S-T and AIMC-0603-3N3S-T, were used to isolate the active metasurface array from the external bias feed. Finally, the fabricated prototype was conformally mounted on a cylinder with a radius of 200 mm and its experimental performance was tested.

[0047] like Figure 4a As shown in -d, the transmission characteristics of the conformal multifunctional active metasurface were tested, and the effects of different incident angles on the resonant frequency and multifunctional electromagnetic control performance under the conformal surface condition were analyzed. Figure 4a and 4bThe electromagnetic switching functionality of the proposed conformal multifunctional active metasurface is demonstrated under TE and TM polarization. The frequency response of the transmission coefficient is approximately identical under TE and TM polarization. In the "00" state, the measured -10 dB bandwidth of the transmission coefficient under both TE and TM polarization is 3.22 GHz (4.73 GHz–7.95 GHz), operating in a band-stopped reflection state. In the "11" state, the proposed conformal multifunctional active metasurface operates in a transmission state for both TE and TM polarized incident waves. When the two PIN diodes switch from the "00" state to the "11" state, the measured bandwidth with a transmission coefficient difference greater than 10 dB is 2.8 GHz (5.2 GHz–8 GHz). Therefore, the curved conformal multifunctional active metasurface possesses stable electromagnetic switching functionality. Stable dual-polarization switching functionality can be obtained in both coded states by actively controlling the bias state of the PIN diodes. Figure 4c and Figure 4d As shown, the orthogonal polarization control function of the proposed conformal multifunctional active metasurface is verified. The transmission coefficient of the proposed conformal multifunctional active metasurface was measured in the "01" and "10" states. When the PIN diodes soldered to the upper and lower surfaces are in different bias states, incident electromagnetic waves of different polarizations can be selectively transmitted or reflected. It has a maximum transmission coefficient isolation of over 30 dB at 6.6 GHz. The excellent orthogonal polarization control function of the curved conformal multifunctional active metasurface is verified. Furthermore, even at large incident angles up to 80°, the proposed conformal multifunctional active metasurface still has a stable transmission coefficient frequency response in the conformal state. In summary, the proposed conformal multifunctional active metasurface has multifunctional electromagnetic modulation characteristics of full polarization electromagnetic switching and orthogonal polarization control, and also has excellent angular stability and polarization insensitivity.

[0048] It is worth noting that previous research on conformal applications of metasurfaces has mainly focused on passive forms. Research on conformal applications of active metasurfaces remains lacking. The multifunctional active metasurface proposed in this paper achieves a conformal structure while also possessing flexible electromagnetic control capabilities. Furthermore, it completes the multifunctional design of an active metasurface, exhibiting excellent full-polarization electromagnetic switching and orthogonal polarization control even in a conformal structure. In addition, this structure also has significant advantages in conformality, miniaturization, wide bandwidth control, angular stability, and polarization stability.

Claims

1. A conformal multifunctional active metasurface with high angular stability, characterized in that: It includes several periodically and closely arranged unit structures. Each periodic unit structure includes two metal layers, one dielectric layer, a metallized via connecting the two metal layers, and two PIN diodes. The two metal layers are respectively etched on the upper and lower surfaces of the dielectric layer, and the two PIN diodes are respectively embedded between the upper and lower metal layers. The two metal layers are specifically an upper surface metal patch and a lower surface metal patch; wherein, the upper surface metal patch has a four-armed spiral structure, consisting of four coiled curved lines; and has rotational symmetry. The lower metal patch is exactly the same as the upper metal patch, and it is also a four-arm spiral structure; the four metal bending lines in the upper and lower layers are connected by metallized vias, and the four metallized vias are centrally symmetrically distributed. The two metal layers each contain a pair of metal pads at the center of the upper and lower surfaces of the dielectric layer. The pair of metal pads on the upper surface are printed vertically on the upper surface of the dielectric layer and electrically connected to two metal bending lines along the vertical direction, for soldering PIN diodes arranged vertically. The pair of metal pads on the lower surface are printed horizontally on the lower surface of the dielectric layer and electrically connected to two metal bending lines along the horizontal direction, for soldering PIN diodes arranged horizontally.

2. The conformal multifunctional active metasurface with high angular stability according to claim 1, characterized in that: Each curved line is obtained by rotating one of the curved lines around the center of the unit by 90°, 180°, or 270°.

3. The conformal multifunctional active metasurface with high angular stability according to claim 1, characterized in that: The metallized via is located at the corner of the metal bend line near the center of the cell.

4. The conformal multifunctional active metasurface with high angular stability according to claim 1, characterized in that: The dielectric layer is made of flexible dielectric substrate with a thickness of 0.1 to 0.5 mm and a dielectric constant of 2.2 to 4.

4.

5. A conformal multifunctional active metasurface with high angular stability according to claim 4, characterized in that: The flexible dielectric substrate includes: polytetrafluoroethylene high-frequency microwave dielectric substrate, PDMS polydimethylsiloxane dielectric substrate, PI polyimide dielectric substrate, PET polyethylene terephthalate dielectric substrate, or Polystyrene dielectric substrate.

6. A conformal multifunctional active metasurface with high angular stability according to claim 1, characterized in that: The diode in question is a PIN diode with the smallest package, TSLP-2-19.

7. A conformal multifunctional active metasurface array with high angular stability, characterized in that: The array is composed of a metasurface as described in any one of claims 1-6. In the array, several PIN diodes in the same column along the vertical direction are connected in series through metasurface units, and then aggregated through an additional feeding network, connected to the first interface (+) and the first interface (-) of the feeding network. For PIN diodes embedded in the lower surface metal layer, several PIN diodes in the same row along the horizontal direction are connected in series through metasurface units, and then aggregated through an additional feeding network, connected to the second interface (+) and the second interface (-) of the feeding network. The PIN diodes embedded in the upper surface metal layer and the PIN diodes embedded in the lower surface metal layer are connected in the same way, but their directions are orthogonal to each other. The PIN diodes arranged along the vertical and horizontal directions are isolated from each other and are controlled simultaneously or independently by external excitation. By controlling the first interface and the second interface to provide bias voltage to the PIN diodes, the state of the metasurface units in the vertical and horizontal polarization directions is independently controlled, thereby independently regulating the two orthogonally polarized incident electromagnetic waves.

8. A control method for a conformal multifunctional active metasurface array with high angular stability as described in claim 7, which is achieved by controlling the "on / off" state of PIN diodes embedded in the upper and lower metal surfaces.

9. The control method according to claim 8, characterized in that: In each metasurface unit structure, two PIN diodes are arranged between the upper and lower metal surfaces of each unit; they are orthogonal to connect two perpendicular curved metal strips, which are responsible for modulating two different polarizations of electromagnetic waves respectively; when the PIN diodes are in the conducting state, the metasurface unit is equivalent to a hybrid parallel LC resonant circuit, realizing a bandpass frequency response, and the electromagnetic wave is transmitted; conversely, when the PIN diodes are in the off state, the metasurface unit is equivalent to a hybrid series LC resonant circuit, realizing a bandstop frequency response, and the electromagnetic wave is reflected; By independently controlling the on / off state of the two PIN diodes on the upper and lower metal layers of the control unit, the band-stop / transmission electromagnetic characteristics of the two orthogonal polarizations can be switched independently.

10. The control method according to claim 8, characterized in that: The control method described above includes "0" and "1" digital states for each metasurface unit in both vertical and horizontal polarization directions, and these digital states are independently adjustable, possessing a two-bit encoding function. A binary code "ij" is used to encode the on / off state of the diodes under vertical and horizontal polarization. "i" represents the on / off state of the PIN diode embedded in the upper metal surface, and "j" represents the on / off state of the PIN diode embedded in the lower metal surface. A binary bit 0 represents the unbiased off state of the PIN diode, and a binary bit 1 represents the forward-biased on state of the PIN diode. This achieves four different encoding states: "00", "11", "01", and "10". A topology feed network interface is used to provide bias voltage to the PIN diodes on the metasurface unit, causing the metasurface unit to exhibit different electromagnetic characteristics in the vertical and horizontal polarization directions, corresponding to four different operating states: dual-polarization bandstop, dual-polarization bandpass, TM polarization wave selection, and TE polarization wave selection. This enables two different control functions: full-polarization electromagnetic switching and orthogonal polarization control.

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