Dual-frequency dual-polarization active multifunctional metasurface with low scattering characteristic

Abstract

The invention belongs to the field of wireless communication, relates to a metasurface technology, and particularly provides a dual-frequency dual-polarization active multifunctional metasurface with a low scattering characteristic, which can flexibly control the amplitude, polarization and phase of electromagnetic waves. The active multifunctional metasurface adopts the design that two subunits are arranged in a staggered mode to form a super unit, and meanwhile independent control over a low working frequency band and a high working frequency band is achieved by loading four PIN diodes in each subunit. In addition, an additional impedance layer is designed to absorb out-of-band electromagnetic waves. Finally, the active multifunctional metasurface can independently switch a reflection state and a polarization conversion state in double working frequency bands, absorbs electromagnetic energy outside the working frequency bands, and constructs one-bit phase coding to realize amplitude control and wide-angle double-beam scanning of reflected waves. According to the invention, excellent multi-dimensional and dual-frequency independent control capability is shown, and huge potential is shown in various applications of a next-generation wireless communication system.

Description

Technical Field

[0001] This invention belongs to the field of wireless communication and relates to metasurface technology. Specifically, it provides a dual-frequency dual-polarization active multifunctional metasurface with low scattering characteristics. Background Technology

[0002] Metasurfaces are two-dimensional artificial electromagnetic materials composed of periodic or aperiodic arrangements of subwavelength structures. For decades, they have attracted widespread attention due to their remarkable ability to manipulate the amplitude, phase, and polarization of electromagnetic waves. Early research on metasurfaces focused primarily on passive designs; however, their static response characteristics under electromagnetic irradiation limited their flexibility in complex electromagnetic environments. Compared to passive metasurfaces, active metasurfaces can achieve dynamic control and multifunctional switching of electromagnetic responses while maintaining the device structure, making them suitable for diverse electromagnetic scenarios.

[0003] Active multifunctional metasurfaces typically achieve operating mode switching and frequency tuning by integrating active devices such as PIN diodes and varactor diodes, or by injecting liquid metal or water, or by combining functional materials such as liquid crystals, vanadium dioxide, and graphene. Among these, PIN diodes are widely chosen due to their fast response time, low cost, and ability to precisely control phase and switch operating modes. To date, numerous studies have utilized PIN diodes to achieve switching of operating modes. For example, in the paper "Q. Guo, F. Hao, M. Qu, J. Su, and Z. Li, “Multiband multifunctional polarization converter based on reconfigurable metasurface,” IEEE Antennas Wirel. Propag. Lett., vol. 23, no. 4, pp. 1241–1245, 2024," Guo et al. proposed an active multifunctional metasurface that can control the polarization state of reflected waves by switching PIN diodes. However, its bias network has high complexity, which may introduce signal interference and cannot guarantee long-term stability in practical systems. Another example is the paper "M. Zhao, H. Li, J. Shi, and Q. Cao, “A polarization-independent multifunctional activefrequency selective surface with compound modes of absorption, transmission and reflection,” IEEE Antennas Wirel. Propag. Lett., pp. 1–5. In “2024”, although Zhao et al. proposed a dual-polarized active multifunctional metasurface that can switch between transmission, absorption and reflection, the design has a narrow transmission bandwidth, which limits its application in broadband systems.Later, this concept was further extended to design a dual-polarized active multifunctional metasurface with four operating modes for amplitude modulation of electromagnetic waves. In the literature “B.Jiang, H. Hu, J. Tian, ​​S. Lei, Y. Wu, and B. Chen, “An active multifunctional metamaterial with four operating modes,” IEEE Trans. Antennas Propag., vol.72, no. 5, pp. 4221–4231, 2024”, Jiang et al. proposed a dual-polarized active multifunctional metasurface integrating four operating modes, simultaneously realizing polarization and amplitude modulation. Due to its ability to flexibly adjust electromagnetic propagation, such as beamforming, programmable imaging, and wireless communication, active multifunctional metasurfaces that utilize hardware controllers such as field-programmable gate arrays (FPGAs) to precisely control the phase of array units in real time have been widely studied.

[0004] Integrating amplitude, polarization, and phase modulation into a single metasurface system has become an important research direction for applications requiring high flexibility and high integration. However, as the scale of metasurface arrays increases, their radar cross-section increases accordingly, leading to intensified out-of-band scattering and significant electromagnetic exposure risks. Therefore, RCS reduction across the entire operating frequency band should also be considered in the design. Based on this, designing and realizing a dual-frequency, dual-polarization, reconfigurable, multifunctional metasurface with low scattering characteristics has become the research focus of this invention. Summary of the Invention

[0005] The purpose of this invention is to provide a dual-frequency, dual-polarization active multifunctional metasurface with low scattering characteristics, capable of flexibly manipulating the amplitude, polarization, and phase of electromagnetic waves. The active multifunctional metasurface employs a design where two sub-units are arranged in an alternating pattern to form a super-unit. Independent control of the lower and higher operating frequency bands is achieved by loading four PIN diodes in each sub-unit. Furthermore, an additional impedance layer is designed to absorb out-of-band electromagnetic waves. Ultimately, this active multifunctional metasurface can independently switch between reflection and polarization conversion states within both operating frequency bands, absorb electromagnetic energy outside the operating frequency band, and simultaneously construct a 1-bit phase code to achieve amplitude manipulation of reflected waves and wide-angle dual-beam scanning. This invention demonstrates excellent multidimensional and dual-frequency independent control capabilities, showing great potential in various applications of next-generation wireless communication systems.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A dual - frequency and dual - polarization active multi - functional metasurface with low - scattering characteristics, which is characterized by being composed of an impedance layer and a reconfigurable polarization - conversion metasurface, and there is an air gap between the impedance layer and the reconfigurable polarization - conversion metasurface;

[0008] The impedance layer includes: a dielectric substrate and a metal structure on its upper surface. The metal structure is composed of 4 metal units, and the 4 metal units are arranged in a 2×2 array;

[0009] The reconfigurable polarization - conversion metasurface includes a feeding layer, a lower - layer dielectric substrate, an adhesive substrate, a metal reflection layer, an upper - layer dielectric substrate, and a polarization - conversion layer stacked in sequence from bottom to top;

[0010] The polarization - conversion layer is composed of high - frequency - band super - cells and low - frequency - band super - cells. The high - frequency - band super - cells and the low - frequency - band super - cells are respectively distributed along two diagonals. The high - frequency - band super - cell is composed of two high - frequency - band sub - cells, and the low - frequency - band super - cell is composed of two low - frequency - band sub - cells. The 4 sub - cells are arranged in a 2×2 array, and each sub - cell corresponds to a metal unit in the impedance layer one by one.

[0011] Further, the high - frequency - band sub - cell and the low - frequency - band sub - cell respectively include: two fish - bone - shaped patches and a circular metal loop. The two fish - bone - shaped patches are orthogonally arranged and connected by the circular metal loop, and PIN diodes are respectively loaded between the two ends of each fish - bone - shaped patch and the circular metal loop.

[0012] Furthermore, a first feeding end is set at the cross - position of the two fish - bone - shaped patches. All PIN diodes are connected to the second feeding end through the circular metal loop, and the two feeding ends are respectively connected to the feeding layer through metal vias; the loading directions of the PIN diodes on the two fish - bone - shaped patches are opposite. When the PIN diode loaded on one fish - bone - shaped patch is turned on, the PIN diode loaded on the other fish - bone - shaped patch is turned off.

[0013] Furthermore, an inductor is loaded between the circular metal loop and the second feeding end.

[0014] Further, the metal unit includes: a square metal patch. A swastika - shaped (卍) slit is opened in the square metal patch, and the swastika - shaped (卍) slit is located on the center line of the square metal patch; the mid - points of the four sides of the square metal patch are respectively connected to a interdigital structure through a first microstrip line, and a lumped resistor is loaded at the mid - point of the first microstrip line; the other end of the interdigital structure is connected to a parallel metal line through a second microstrip line.

[0015] Furthermore, the square metal patch with a swastika-shaped (卍) slit and the interdigital structure respectively equivalently form an LC parallel resonator. At the same time, the parallel metal lines of adjacent metal units equivalently form a capacitor, and the microstrip line equivalently forms an inductor. The capacitor, inductor and lumped resistor together constitute an RLC series circuit.

[0016] Further, the dual-band dual-polarization active multi-functional metasurface has four working modes, namely: A-R-A-R-A mode, A-P-A-P-A mode, A-P-A-R-A mode and A-R-A-P-A mode, where A represents absorption, R represents reflection, and P represents polarization conversion.

[0017] Based on the above technical solutions, the beneficial effects of the present invention are as follows:

[0018] The present invention provides a dual-band dual-polarization active multi-functional metasurface with low scattering characteristics, aiming at the multi-dimensional manipulation of electromagnetic waves, and at the same time having excellent out-of-band low scattering characteristics; through the design of staggered supercells (formed by two sub-units), the independent manipulation of dual-band and dual-polarization is realized, and at the same time, multi-dimensional manipulation of amplitude, polarization and phase is realized according to the unique design; in addition, in response to the requirement of reducing the Radar Cross-Section (RCS) in modern communication systems, the present invention realizes out-of-band RCS reduction and controllable in-band amplitude variation, further reducing the scattering of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 FIG. is a schematic diagram of the topological structure of the dual-band dual-polarization active multi-functional metasurface with low scattering characteristics in the present invention, Figure 1 where (a) is a three-dimensional structure diagram, Figure 1 where (b) is a side view cross-sectional diagram, Figure 1 where (c) is a top view diagram.

[0020] Figure 2 FIG. is a schematic diagram of the structure of the reconfigurable polarization conversion metasurface in the present invention, Figure 2 where (a) is a three-dimensional structure diagram, Figure 2 where (b) is a schematic diagram of the sub-unit structure in the low-frequency band, Figure 2 where (c) is a schematic diagram of the sub-unit structure in the high-frequency band, Figure 2 where (d) is an equivalent circuit model of the PIN diode, Figure 2 where (e) is a schematic diagram of the feed layer structure.

[0021] Figure 3 FIG. is the simulated reflection coefficient of the dual-band dual-polarization active multi-functional metasurface with low scattering characteristics in the present invention under 4 working modes, Figure 3 where (a) is the A-R-A-R-A mode, Figure 3 (b) represents the APAPA mode. Figure 3 (c) represents APARA mode. Figure 3 (d) represents the ARAPA mode.

[0022] Figure 4 This refers to the cross-polarization reflection coefficient of the dual-frequency dual-polarization active multifunctional metasurface with low scattering characteristics in this invention. Figure 4 (a) and Figure 4 (b) shows the amplitude and phase response in APAPA mode. Figure 4 (c) and Figure 4 (d) shows the amplitude and phase response in APARA mode. Figure 4 (e) and Figure 4 In the middle (f), the amplitude and phase response are shown.

[0023] Figure 5 The cross-polarization reflection coefficient of the dual-frequency dual-polarization active multifunctional metasurface with low scattering characteristics in this invention under square wave modulation signals with different duty cycles (D) is given. Figure 5 (a) represents dual operating frequency bands. Figure 5 (b) shows the amplitude modulation in APAPA mode at low operating frequencies. Figure 5 (c) shows the amplitude modulation in APAPA mode at high operating frequencies. Figure 5 (d) represents amplitude modulation in APARA mode at low operating frequencies. Figure 5 (e) represents the amplitude modulation of the high operating frequency band in ARAPA mode.

[0024] Figure 6 The radiation patterns of the dual-frequency dual-polarization active multifunctional metasurface with low scattering characteristics in this invention are measured and simulated at different frequencies under y-polarization excitation. Figure 6 (a) is 4.65 GHz. Figure 6 (b) is 7.3 GHz. Figure 6 (c) is 4GHz. Figure 6 The MHz (d) is 6GHz. Figure 6 The MHz (e) is 8.5 GHz.

[0025] Figure 7 This is the normalized scanning radiation pattern obtained from simulation and measurement of the dual-frequency dual-polarization active multifunctional metasurface with low scattering characteristics in this invention under y-polarization excitation. Figure 7 (a) is 4.65 GHz. Figure 7 (b) is 7.3 GHz. Detailed Implementation

[0026] To make the objectives, technical solutions, and beneficial effects of the present invention more clear and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0027] This embodiment provides a dual - frequency and dual - polarization active multifunctional metasurface with low - scattering characteristics, which consists of an impedance layer and a reconfigurable polarization - conversion metasurface. Its topological structure is as Figure 1 shown, Figure 1 where (a) in it is a three - dimensional structure schematic diagram, Figure 1 where (b) in it is a side - view sectional view, Figure 1 where (c) in it is a top - view schematic diagram, and the impedance layer and the reconfigurable polarization - conversion metasurface are separated by an air gap.

[0028] The impedance layer includes: a dielectric substrate and a metal structure on its upper surface; the metal structure is composed of 4 metal units, and the 4 metal units are arranged in a 2×2 array;

[0029] The metal unit includes: a square metal patch with a swastika - shaped (卍) slit opened in it. The swastika - shaped (卍) slit is located on the center line of the square metal patch; the mid - points of the four sides of the square metal patch are respectively connected to a interdigital structure through a first microstrip line, and a lumped resistor is loaded at the mid - point of the first microstrip line; the other end of the interdigital structure is connected to a parallel metal line through a second microstrip line; the square metal patch with a swastika - shaped (卍) slit and the interdigital structure respectively form an LC parallel resonator to transmit electromagnetic waves with low loss within two working frequency bands; at the same time, the parallel metal lines of adjacent metal units form a capacitor equivalently, and the microstrip lines form an inductor equivalently. The capacitor, inductor, and lumped resistor together constitute an RLC series circuit to absorb electromagnetic waves outside the working frequency bands;

[0030] Specifically, all the structural parameters of the impedance layer in this embodiment are: R = 110Ω, l1 = 8.2mm, l2 = 6mm, l3 = 3mm, l4 = 1.8mm, l5 = 1.3mm, l6 = 3.4mm, w1 = 0.2mm, w2 = 0.6mm, w3 = 0.25mm, t1 = 0.254mm, t2 = 3mm, t3 = 0.1mm, t4 = 0.254mm, h1 = 9mm.

[0031] The reconfigurable polarization - conversion metasurface is as Figure 2 shown, Figure 2 [ where (a) in it is a three - dimensional structure schematic diagram, <00> Figure 2 where (b) in it is a schematic diagram of the sub - unit structure of the low - frequency band, Figure 2 where (c) in it is a schematic diagram of the sub - unit structure of the high - frequency band, Figure 2 where (d) in it is the equivalent circuit model of the PIN diode, Figure 2(e) is a schematic diagram of the feed layer structure; the reconfigurable polarization conversion metasurface includes a feed layer, a lower dielectric substrate, an adhesive substrate, a metal reflective layer, an upper dielectric substrate, and a polarization conversion layer stacked sequentially from bottom to top;

[0032] The polarization conversion layer consists of high-frequency supercells and low-frequency supercells to achieve dual polarization characteristics. The high-frequency supercells and low-frequency supercells are distributed along two diagonals on the upper surface of the upper dielectric substrate. Each high-frequency supercell consists of two high-frequency sub-units, and each low-frequency supercell consists of two low-frequency sub-units. The four sub-units are arranged in a 2×2 array, and each sub-unit corresponds one-to-one with a metal unit in the impedance layer (center overlap).

[0033] The high-frequency segment unit and the low-frequency segment unit each include: two herringbone-shaped patches and a circular metal ring. The two herringbone-shaped patches are orthogonally arranged and connected by the circular metal ring, and PIN diodes are loaded between the two ends of each herringbone-shaped patch and the circular metal ring. A first feed terminal is set at the intersection of the two herringbone-shaped patches and connected to the feed layer through a metal via. All PIN diodes are connected to a second feed terminal through the circular metal ring and connected to the feed layer through a metal via. The loading directions of the PIN diodes on the two herringbone-shaped patches are opposite. When the PIN diode loaded on one herringbone-shaped patch is turned on, the PIN diode loaded on the other herringbone-shaped patch is turned off. An inductor is loaded between the circular metal ring and the second feed terminal to prevent radio frequency leakage.

[0034] Specifically, in this embodiment, all structural parameters of the reconfigurable polarization conversion metasurface are: P = 17.5 mm, l a1 =6.875mm, l a2 =1.5mm, l a3 =1.567mm, l a4 =0.567mm, l a5 =2.173mm, l a6 =1.423mm, l a7 =1.3mm, w a1 =1mm, w a2 =0.5mm, r a1 =8.525mm, r a2 =7.525mm, θ=30°, l b1 =3.4mm, l b2 =3.4mm, l b3 =1.85mm, l b4 =3.2mm, W b1 =1.2mm, W b2 =0.5mm, R b1 =5.55mm, Wc1 =0.5mm, W c2 =0.2mm, R f1 =8Ω, R f2 =2Ω, L f =0.45nH, C f =0.113pF.

[0035] To achieve the switching of operating states, four Skyworks-manufactured PIN diodes (SMP1345-040LF) are respectively loaded into the two types of sub-cells; such as Figure 2 (b) and Figure 2 As shown in (c), the positive ("+") and negative ("-") terminals of the PIN diode are marked on the sub-unit; when the diode is in the off state, the PIN diode can be equivalent to a series RLC circuit, while when the PIN diode is on, the diode behaves like an inductor L. f Series on-resistance; all PIN diodes share the same bias voltage through a circular metal ring, and the PIN diodes along the 45° direction (i.e., the v-direction) or the 315° direction (i.e., the u-direction) are simultaneously modulated to the same state, such as... Figure 2 As shown in (b), the PIN diode along the 315° direction in the low-frequency segment sub-unit is named PIN1, while the PIN diode along the 45° direction is named PIN2; similarly, Figure 2 In (c), PIN3 refers to the PIN diode along the 315° direction in the high-frequency segment sub-unit, while PIN4 refers to the PIN diode along the 45° direction.

[0036] Meanwhile, inductors of models LQW15AN15NG00D and LQW15AN4N4C00D were inserted into the low-frequency segment unit and the high-frequency segment unit, respectively, to prevent radio frequency leakage.

[0037] The polarization conversion layer and the metal reflective layer are printed on both sides of the 3mm thick F4BTMS300 substrate (ε1=3, tanδ=0.0013), and the metal reflective layer is used to block the transmission of electromagnetic waves; while the power feeding layer is printed on the 0.254mm thick IT180A substrate (ε2=4.1, tanδ=0.016); in addition, a 0.1mm thick RO4450F substrate (ε3=3.52, tanδ=0.004) is used as an adhesive layer, and the F4BTMS300 substrate and the IT180A substrate are laminated in sequence.

[0038] The beneficial effects of the present invention will be explained in detail below with reference to simulation tests.

[0039] By controlling the bias states of different diodes, four different operating modes can be achieved, namely absorption-reflection-absorption-reflection-absorption (ARARA) mode, absorption-polarization conversion-absorption-polarization conversion-absorption (APAPA) mode, APARA mode, and ARAPA mode. The corresponding diode bias states are shown in Table 1.

[0040] like Figure 3 The figure shows the electromagnetic simulation results of this invention in simulation software under periodic boundary conditions and with electromagnetic waves incident perpendicularly. It can be seen that in ARARA mode, the device exhibits two 3-dB reflection bands in the ranges of 4.48-5.1GHz (12.9%) and 7.11-7.67GHz (7.6%), respectively, while the cross-polarization reflection coefficient drops below -35dB at the frequency of interest. In APAPA mode, x-polarized and y-polarized incident waves are converted into cross-polarized reflected waves (Ryx and Rxy) in the ranges of 4.44-4.85GHz (8.8%) and 7-7.67GHz (9.1%), respectively. Figure 3 (c) and Figure 3 As shown in (d), the active multifunctional metasurface achieves polarization conversion (or reflection) at lower operating frequencies and reflection (or polarization conversion) at higher operating frequencies in APARA mode (or ARAPA mode). Furthermore, the active multifunctional metasurface of this invention exhibits significantly lower out-of-band scattering characteristics in all operating modes.

[0041] Table 1. Diode status under different operating modes

[0042]

[0043] It is worth noting that the PIN diodes loaded in orthogonal directions always operate in opposite states, resulting in the proposed active multifunctional metasurface having nine different operating states, as shown in Table 1.

[0044] like Figure 4The diagram shows the cross-polarization reflection coefficient and phase response of the active multifunctional metasurface proposed in this invention under different operating modes. It can be seen that under the same operating mode, the magnitudes of all operating states are the same, while three different phase shifts can be achieved: a dual operating frequency band with a phase difference of 180°±10° (i.e., states 2 and 3 or states 4 and 5), a lower operating frequency band with a phase difference of 180°±10° (i.e., states 2 and 5, states 3 and 4, or states 6 and 7), and a higher operating frequency band with a phase difference of 180°±10° (i.e., states 2 and 4, states 3 and 5, or states 8 and 9). Therefore, by controlling the switching state of the PIN diodes in the sub-units, the phase shift of the active multifunctional metasurface in the lower and higher operating frequency bands can be independently controlled.

[0045] Furthermore, in order to thoroughly evaluate the application potential of the active multifunctional metasurface proposed in this invention, this embodiment takes a 10×10 array as an example to explore its amplitude modulation and beam scanning capabilities for reflected waves under the condition of perpendicular electromagnetic wave incidence.

[0046] like Figure 5 The figure shows the cross-polarization reflection coefficients measured for square wave modulated signals with different duty cycles at a modulation frequency of 500kHz. It can be seen that the amplitude of the cross-polarization reflection coefficient gradually decreases as the duty cycle increases from 0 to 0.5. When D=0.5, the amplitude drops below -25dB across the entire frequency band. Therefore, controllable RCS reduction can be achieved within the frequency of interest. Furthermore, by selecting specific operating states, the amplitudes of the lower and higher frequency cross-polarization reflection coefficients can be independently controlled in APAPA mode (APARA or ARAPA mode), such as... Figure 5 (a) Figure 5 As shown in (e).

[0047] like Figure 6 The figure shows the measured and simulated radiation patterns of the xoz plane under y-polarized plane wave excitation. As can be seen from the figure, the measured and simulated radiation patterns of the active multifunctional metasurface proposed in this invention are in good agreement. The device produces two symmetrical scattered beam configurations under plane wave incident conditions. At the same time, the gain of the radiation pattern outside the operating frequency band (e.g., 4 GHz, 6 GHz, and 8.5 GHz) is less than -10 dBi, indicating that the reflection of the proposed device is suppressed. In addition, when the scanning angle of one operating band changes, the radiation pattern of the other band can remain stable.

[0048] To better explore the advantages of the active multifunctional metasurface proposed in this invention in beam control, dual-band wide-angle beam scanning was implemented and verified; such as Figure 7The figure shows the simulated and measured normalized scanning radiation pattern of the active multifunctional metasurface proposed in this invention on the xoz plane. As can be seen from the figure, under y-polarization excitation, the symmetrical dual beams can continuously scan in the range of 0-60° in the lower operating frequency band and the range of 0-35° in the higher operating frequency band. This shows that the active multifunctional metasurface has excellent beam control performance and matches the preset target well, effectively verifying the ability of the proposed active multifunctional metasurface to achieve beam scanning under online polarization wave excitation. In addition, since the array encoding can be independently controlled by FPGA, the beam pointing of different operating frequency bands can be continuously adjusted in real time as needed.

[0049] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.

Claims

1. A dual-frequency dual-polarization active multifunctional metasurface with low scattering characteristics, characterized in that, It consists of an impedance layer and a reconfigurable polarization conversion metasurface, and an air gap is provided between the impedance layer and the reconfigurable polarization conversion metasurface; The impedance layer includes: a dielectric substrate and a metal structure on its upper surface. The metal structure is composed of 4 metal units, and the 4 metal units are arranged in a 2×2 array; The reconfigurable polarization conversion metasurface includes a feeding layer, a lower dielectric substrate, an adhesive substrate, a metal reflection layer, an upper dielectric substrate and a polarization conversion layer which are stacked in sequence from bottom to top; The polarization conversion layer is composed of high-frequency supercells and low-frequency supercells. The high-frequency supercells and the low-frequency supercells are respectively distributed along two diagonals. The high-frequency supercell is composed of two high-frequency subcells, and the low-frequency supercell is composed of two low-frequency subcells. The 4 subcells are arranged in a 2×2 array, and each subcell corresponds to a metal unit in the impedance layer one by one.

2. The dual-frequency dual-polarization active multifunctional metasurface with low scattering characteristics according to claim 1, characterized in that, The high-frequency subcell and the low-frequency subcell respectively include: two fishbone-shaped patches and a circular metal loop. The two fishbone-shaped patches are orthogonally arranged and connected by the circular metal loop, and PIN diodes are respectively loaded between the two ends of each fishbone-shaped patch and the circular metal loop.

3. The dual-frequency dual-polarization active multifunctional metasurface with low scattering characteristics according to claim 2, characterized in that, A first feeding end is arranged at the intersection position of the two fishbone-shaped patches. All the PIN diodes are connected to the second feeding end through the circular metal loop. The two feeding ends are respectively connected to the feeding layer through metal vias; the loading directions of the PIN diodes on the two fishbone-shaped patches are opposite. When the PIN diode loaded on one fishbone-shaped patch is turned on, the PIN diode loaded on the other fishbone-shaped patch is turned off.

4. The dual-frequency dual-polarization active multifunctional metasurface with low scattering characteristics according to claim 2, characterized in that, An inductor is loaded between the circular metal loop and the second feeding end.

5. The dual-frequency dual-polarization active multifunctional metasurface with low scattering characteristics according to claim 1, characterized in that, The metal unit includes: a square metal patch with a swastika-shaped (卍) slit opened in it. The swastika-shaped (卍) slit is located on the center line of the square metal patch; the midpoints of the four sides of the square metal patch are respectively connected to an interdigital structure through a first microstrip line, and a lumped resistor is loaded at the midpoint of the first microstrip line; the other end of the interdigital structure is connected to a parallel metal line through a second microstrip line.

6. The dual-frequency dual-polarization active multifunctional metasurface with low scattering characteristics according to claim 5, characterized in that, The square metal patch with a swastika-shaped (卍) slit opened in it and the interdigital structure respectively form an LC parallel resonator. At the same time, the parallel metal lines of adjacent metal units form a capacitor equivalently, and the microstrip lines form an inductor equivalently. The capacitor, the inductor and the lumped resistor together constitute an RLC series circuit.

7. The dual-frequency dual-polarization active multifunctional metasurface with low scattering characteristics according to claim 1, characterized in that, The dual-band dual-polarization active multifunctional metasurface has four working modes, namely: A-R-A-R-A mode, A-P-A-P-A mode, A-P-A-R-A mode and A-R-A-P-A mode, where A represents absorption, R represents reflection, and P represents polarization conversion.

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