A high cross-polarization discrimination dual-polarization 2-bit programmable metasurface

Abstract

The present invention discloses a high cross-polarization discrimination dual-polarization 2-bit programmable metasurface, which comprises a metasurface array formed by periodically arranging 12×12 metasurface units, and the unit states are switched in real time by an electrically tunable manner; the metasurface unit includes three dielectric plates, namely dielectric plate one, dielectric plate two and dielectric plate three, a pp layer one is added between dielectric plate one and dielectric plate two, and a pp layer two is added between dielectric plate two and dielectric plate three; the metasurface unit is provided with four copper layers from top to bottom, which are successively divided into a main resonator layer, a current isolation layer, a ground layer and a feeding network layer; the main resonator layer is located on the upper surface of dielectric plate one, the current isolation layer is located on the lower surface of dielectric plate one, the ground layer is at the bottom of dielectric plate two, and the bottom layer of the unit is used for the layout of the DC feeding network to form the feeding network layer, and the feeding network layer is located at the bottom of dielectric plate three. The present invention can increase the electromagnetic wave regulation ability of the programmable metasurface and achieve a breakthrough progress in the intelligent metasurface platform.

Description

Technical Field

[0001] The present invention belongs to the technical field of phase-programmable metasurfaces, and particularly relates to a high cross-polarization discrimination dual-linear polarization 2-bit programmable metasurface. Background Art

[0002] Existing programmable metasurfaces are mainly 1-bit metasurfaces. This blurring of the phase reduces the design difficulty, but greatly reduces the ability to control electromagnetic waves. It can only perform phase control of 0° and 180° on the incident wave, with a large quantization error. When forming an array, there is a quantization error greater than 3 dB. Moreover, most existing programmable metasurfaces can only be adjusted in a single polarization direction, or through specific designs, the two polarizations must be adjusted simultaneously, resulting in low adjustment flexibility.

[0003] Although dual-polarized programmable metasurfaces have been successively proposed by some researchers, they generally have some defects. In (N.Zhang et al., “A Dual-polarized Reconfigurable Reflectarray Antenna Basedon Dual-channel Programmable Metasurface,” IEEE Trans.Antennas Propag., pp.1–1, 2022, doi:10.1109 / TAP.2022.3165872.), a symmetric dual-polarized 1-bit programmable metasurface was designed. Each unit uses 4 PIN diodes. By simultaneously turning on and off 2 PIN diodes in each polarization direction, a 1-bit phase change of the dual-channel is achieved. Although the designed metasurface can achieve independent regulation of the orthogonal channels, the resolution is relatively low, and there are many inherent defects of the 1-bit metasurface. Moreover, each unit uses 4 PIN diodes, resulting in an increase in cost. After that, the aperture efficiency of the metasurface is still relatively low, which also reduces the robustness of the system. In (Y.Wang, S.Xu, F.Yang, andD.H.Werner, “1Bit Dual-Linear Polarized Reconfigurable Transmitarray AntennaUsing Asymmetric Dipole Elements With Parasitic Bypass Dipoles,” IEEETrans.Antennas Propag., vol.69, no.2, pp.1188–1192, 2021, doi:10.1109 / TAP.2020.3005713.), a single-polarized 1-bit programmable dipole metasurface unit was designed. By arranging the units orthogonally, 1-bit independent regulation of orthogonal dual polarization was achieved. Although the form is different, it has the same defects. By using varactor diodes, multi-bit independent regulation of dual polarization can be achieved (K.Chen, N.Zhang, G.Ding, J.Zhao, T.Jiang, and Y.Feng, “Active Anisotropic Coding Metasurface withIndependent Real-Time Reconfigurability for Dual Polarized Waves,” Adv.Mater.Technol., vol.5, no.2, p.1900930, 2020, doi:https: / / doi.org / 10.1002 / admt.201900930.).However, due to the large loss of varactor diodes and the relatively complex regulation, which requires regulating the voltage across the diodes, it is often impossible to achieve precise regulation. The design is difficult and the system robustness is lower. As a result, the multi-bit metasurfaces achieved often have low aperture efficiency and limited regulation accuracy.

[0004] As of now, no one has proposed a co-aperture dual-linear-polarization independently tunable 2-bit programmable metasurface based on PIN diodes. Summary of the Invention

[0005] In order to overcome the deficiencies of the above-mentioned prior art, the purpose of the present invention is to provide a dual-linear-polarization 2-bit programmable metasurface with high cross-polarization discrimination, which has the structural characteristics of simple and clear working principle and low profile and is easy to integrate. It can increase the regulation ability of the programmable metasurface for electromagnetic waves and achieve a breakthrough in the intelligent metasurface platform.

[0006] In order to achieve the above purpose, the technical solution adopted by the present invention is:

[0007] A dual-linear-polarization 2-bit programmable metasurface with high cross-polarization discrimination includes a metasurface array composed of 12×12 metasurface units arranged periodically, and the unit states are switched in real time by an electrically tunable method;

[0008] The metasurface unit includes three dielectric plates, namely dielectric plate one, dielectric plate two, and dielectric plate three. A pp layer one is added between dielectric plate one and dielectric plate two, and a pp layer two is added between dielectric plate two and dielectric plate three;

[0009] The metasurface unit is provided with four copper layers from top to bottom, which are successively divided into a main resonator layer, a current isolation layer, a ground layer, and a feeding network layer;

[0010] The main resonator layer is located on the upper surface of dielectric plate one, the current isolation layer is located on the lower surface of dielectric plate one, the ground layer is at the bottom of dielectric plate two, and the bottom layer of the unit is used for the layout of the DC feeding network to form the feeding network layer, and the feeding network layer is located at the bottom of dielectric plate three.

[0011] The main resonator layer is composed of two dipoles orthogonally placed in the ±45° directions and four parasitic patches. A plurality of metallized vias are arranged in the middle and at the four ends of the unit. The metallized vias are used to connect the main resonator layer to the feeding network layer, and then directly connected to the ground layer through an inductor and a blind hole in the center.

[0012] The metasurface unit includes 8 inductors to isolate radio frequency and direct current. Among them, 4 are respectively located at the edge positions of the main resonator layer of the unit to isolate radio frequency and the positive DC bias signal, and the other 4 are located at the center of the feeding network layer to isolate radio frequency and DC ground.

[0013] The two orthogonal basic dipoles and two parasitic patches in their respective directions are separated by slots, and PIN diodes are placed between each pair of slots. By controlling the on / off state of the PIN diodes.

[0014] The two dipoles are two centrally symmetric patches. The parasitic patches and the central patches are connected by diodes. The cathodes of the diodes face the center of the structure and are finally grounded. At the center of the structure, the two orthogonal central resonant patches are separated by a cross-isolation structure of the second copper layer.

[0015] The dielectric board is an F4B copper-clad dielectric board, which is laminated. The thickness of the board is 2 mm, the dielectric constant is 2.2, the loss tangent is 0.001, and a pp layer is laminated between the dielectric boards. The thickness of the pp layer is about 0.05 mm.

[0016] The overall cross-sectional height of the metasurface unit is about 0.07 wavelength in terms of the electrical size at the center frequency of 3.5 GHz.

[0017] The period of the metasurface unit is 30.1 mm, and the electrical size is 0.35 wavelength.

[0018] The metasurface array operates at 3.5 GHz. A horn antenna is used to spatially feed the metasurface. The RF signal is input from the horn end, radiated to the metasurface through the horn antenna. The metasurface realizes functions such as beam scanning and beam splitting of the scattered beam through the real-time switching of the PIN tube sequence, thereby verifying the performance of the metasurface.

[0019] The horn antenna is fixed at a distance of 288 mm from the metasurface, and the focal diameter ratio is 0.8.

[0020] The programmable metasurface is used for wireless communication, deep space exploration, energy transmission, and microwave imaging.

[0021] The technical problems solved by the present invention:

[0022] Solve the problems of low electromagnetic regulation flexibility, low phase resolution, and few polarization regulation dimensions of the programmable metasurface. By designing a sub-wavelength co-aperture dual-linear polarization independently controllable 2-bit phase programmable metasurface unit and forming an array as shown in Figure 1 to achieve the two-polarization independent 2-bit modulation of the programmable metasurface.

[0023] Solve the problem of low aperture efficiency of the programmable metasurface. The designed metasurface unit is 2-bit digital coding with small quantization loss. Based on the cross-dipole resonant unit as shown in Figure 2 and using the minimum number of PIN diodes required for 2-bit control on it, and selecting a dielectric substrate with appropriate thickness and dielectric constant, so that the insertion loss of the unit is small, realizing an aperture efficiency far greater than that of the existing dual-linear polarization programmable metasurface.

[0024] Solve the problems of low robustness and relatively high cost of existing programmable metasurfaces. This design uses 4 PIN diodes to achieve 2-bit independent regulation of dual linear polarization of the metasurface. The theoretically minimum number of PIN diodes is used, reducing the cost and increasing the system robustness.

[0025] Solve the problems of high crosstalk and low cross-polarization discrimination of dual linear polarization programmable metasurfaces. To evaluate the crosstalk between two orthogonal channels, the concept of cross-polarization discrimination commonly used in base station antennas is used in this design, and a cross-isolation structure is designed to achieve a metasurface with high cross-polarization discrimination.

[0026] Advantages of the present invention:

[0027] The present invention designs a novel co-aperture dual linear polarization independently adjustable high cross-polarization discrimination 2-bit programmable metasurface. The unit realizes the function of 2-bit phase regulation of dual linear polarization using the minimum number of PIN tubes through two orthogonally placed asymmetric dipoles, and realizes a dual linear polarization independently regulated metasurface with high cross-polarization discrimination through the design of a cross-isolation structure. The invention has higher flexibility in electromagnetic wave regulation, more regulation dimensions, large aperture efficiency, low cost, high system robustness, high cross-polarization discrimination and low crosstalk between two polarization channels. Description of the drawings

[0028] Figure 1 Schematic diagram of the response of the +45° polarized electromagnetic wave incident on the metasurface of the present invention.

[0029] Figure 2 Three-dimensional schematic diagram of the unit structure of the present invention.

[0030] Figure 3 Top view of the unit of the present invention.

[0031] Figure 4 Schematic diagram of the amplitude-phase response of the unit of the present invention when excited by ±45° polarization respectively under a given PIN tube state sequence.

[0032] Figure 5 Schematic diagram of the electric field and current distribution when the +45° polarization is excited with different PIN tube states and structures of the present invention.

[0033] Figure 6 Simulated main polarization and cross-polarization patterns in the 0° direction of the target beam when the +45° polarization is excited in the present invention.

[0034] Figure 7 Schematic diagram of the simulation results of beam scanning in the E-plane when the +45° polarization is excited in the present invention; schematic diagram of the simulation results of beam scanning in the H-plane when the -5° polarization is excited.

[0035] Figure 8 Schematic diagram of split beams with target beams of ±30° and ±45° polarization generated during x-polarization excitation of the present invention.

[0036] Figure 9 Schematic diagram of generating a circularly polarized beam and performing beam scanning during x-polarization excitation of the present invention. Detailed implementation manners

[0037] The present invention will be further described in detail below with reference to the accompanying drawings.

[0038] The present invention provides a co-aperture dual-linear-polarization independently adjustable 2-bit programmable metasurface based on PIN diodes. The metasurface array operates at 3.5 GHz and is formed by periodically arranging the designed units.

[0039] A horn antenna is used to spatially feed the metasurface. The RF signal is input from the horn end, radiated to the metasurface through the horn antenna, and the metasurface realizes functions such as beam scanning and beam splitting of the scattered beam through real-time switching of the PIN tube sequence, thereby verifying the performance of the metasurface. The schematic diagram of the overall array model is as Figure 1 shown. The horn antenna is fixed 288 mm away from the metasurface, and the focal diameter ratio is 0.8.

[0040] The metasurface array is obtained by periodically arranging 12×12 metasurface units. The unit states are switched in real time through an electronic tuning method, and the working states of each unit on the array can be synthesized according to the target function to realize the corresponding functions.

[0041] Among them, the schematic diagram of the unit structure is as Figure 2 shown. The unit is composed of three layers of F4B copper-clad dielectric plates laminated together. The thickness of the plate is 2 mm, the dielectric constant is 2.2, the loss tangent is 0.001, and a pp layer is laminated between the dielectric plates, with a thickness of about 0.05 mm. The overall profile height of the obtained unit is about 0.07 wavelength of the electrical size at the center frequency of 3.5 GHz, and the profile is relatively low.

[0042] The unit structure period is 30.1 mm, and the electrical size is 0.35 wavelength. The copper layers from top to bottom are successively divided into a main resonator layer, a current isolation layer, a ground layer, and a feeding network layer.

[0043] Among them, the top main resonator layer is composed of two dipoles (two centrally symmetric patches) orthogonally placed in the ±45° directions and four parasitic patches. The cross isolation structure at the center of the unit avoids the direct flow of current between the two main resonators. Multiple metallized vias at the middle and four-edge positions of the unit first connect the main resonator layer to the feeding network layer, and then are directly connected to the ground layer through an inductor and a blind hole at the center.

[0044] To achieve programmable phase control of the metasurface, in this application, the PIN diode MADP-000907 produced by M / A-COM is used as a switch, and the inductor LQP03HQ16NH02D made by Murata is used as an inductor for isolating radio frequency and direct current. Among them, these devices can be replaced by other diodes and inductors with similar functions. The switch and the inductor for isolating radio frequency and direct current are surface-mounted on the top and bottom metals of the metasurface unit.

[0045] Figure 3 The top view of the unit is given. Two centrosymmetric patches and four parasitic patches with different lengths are used as the main resonator structure. The parasitic patches are connected to the central patch through diodes. The negative poles of the diodes face the center of the structure and are finally grounded. At the center of the structure, two orthogonal central resonator patches are separated by a cross-isolation structure on the second copper layer. The ground layer is at the bottom of the dielectric board 2 and is 4 mm away from the top main resonator. The bottom copper layer of the unit is the feed network layer for the layout of the DC feed network. A total of 8 inductors are used in the unit to isolate radio frequency and direct current. Among them, 4 are located at the edges of the main resonator layer of the unit to isolate radio frequency and the positive DC bias signal, and the other 4 are located at the center of the feed network layer to isolate radio frequency and DC ground. Its main parameters are listed in Table I.

[0046] Table I Main Dimension Parameters (Unit: MM)

[0047] L1 L2 L3 L4 L5 L6 W1 W2 2.15 2.75 2.8 3.45 6.25 6.95 4.5 6

[0048] The unit is modeled and simulated in the commercial simulation software Ansys Electronics Desktop 2022R1, and its high-frequency response near 3.5 GHz can be obtained.

[0049] The dipole antenna is one of the most common antennas. By the orthogonal arrangement of dipole antennas and specific designs, a dual-linear polarization antenna can be realized. Correspondingly, a novel orthogonally placed programmable dipole scatterer unit is designed here. As a novel dual-linear polarization resonant scattering structure unit, it can achieve 2-bit phase control of electromagnetic waves incident in the ±45° directions. At the top, two orthogonally placed dipoles are respectively on the two orthogonal polarization directions of ±45°, corresponding to controlling the incident fields in the ±45° polarization directions.

[0050] First, through the design of the overall structure, especially the top dipole patch, a strong resonance is generated in the unit near 3.5 GHz. Two orthogonal basic dipoles and two parasitic patches in their respective directions are separated by slots. PIN diodes are placed between each pair of slots. By controlling the on / off state of the PIN diodes, the coupling relationship between the basic dipole and the parasitic patch can be adjusted. Here, for the sake of concise and clear expression, the PIN tubes in the unit shown in the figure are numbered 3, 1, 4, 2 in a counterclockwise direction starting from the upper left corner. For example, when the PIN switch 2 in the +45° direction is turned on and other PIN switches are turned off, the corresponding serial number is "00 / 10". Obviously, through the operation adjustment of the 4 PIN diodes, the unit can switch among 16 working states as a whole. Due to the orthogonality and cross structure of the two dipoles, the responses in the two directions are independent, which can also be observed from the subsequent result discussion.

[0051] Due to the approximate central symmetry of the structure, the working mechanism in the +45° polarization direction is taken as an example for illustration. One dipole patch, two parasitic patches in the +45° direction, and two PIN diodes in the middle of the slots act as electrically tunable resonant devices. By applying forward and reverse voltages across the PIN diodes, the effective electrical length of the dipole can be changed, thereby changing the resonant characteristics of the dipole and generating a 2-bit relative phase change in the electromagnetic wavefront. When the two PIN switches 1 and 2 in the +45° direction are turned on, the central dipole is considered to be connected to the patches on both sides. At this time, the structure resonates with the maximum electrical length, approximately 0.39 dielectric wavelengths. When the two PIN diodes are turned off, the electrical length becomes 0.31 dielectric wavelengths. Similarly, other states of the PIN switches (such as one side short-circuited and the other side open-circuited) also cause the dipole to resonate at different frequencies. Different resonant frequencies naturally result in different phase responses at 3.5 GHz. At the same time, the ground plane ensures the reflection of most of the radio frequency energy. The working principle of the unit in the -45° polarization direction is similar.

[0052] Figure 4The simulated reflection coefficients of the main polarization of the PIN switch under a given state sequence are presented. It can be seen that when the ±45° polarized waves are incident respectively, almost all the RF energy is reflected. There is a loss of about 2 dB near the center frequency, which is caused by the resonance and ohmic loss of the scatterer. When the corresponding main polarized wave irradiates the unit, the absolute phase changes of the reflection phase at 3.5 GHz are 111.1°, 15.3°, -69.3°, -163.0° in the +45° polarization direction and 107.0°, 13.4°, -71.1°, -160.9° in the -45° direction. The relative phase deviation of each state is about 90°, and all can be quantified to a 2-bit phase resolution. At the same time, the phase response of the main polarization is independent of the state of the PIN diodes placed in the cross-polarization direction, because when the state of the PIN diodes in the orthogonal direction is switched, almost no change in the RF performance of the unit can be seen. When the state sequence of the unit PIN tubes changes from "01 / 00" to "01 / 10", under the +45° incidence, the reflection phase changes from 15.3° to 16.4°, which is almost negligible. Figure 6 The electric field and current distributions of the unit in the corresponding states are analyzed. When the sequence is "01 / 00" and "01 / 10', the electric field and current distribution diagrams on the surface of the unit under the +45° polarization incidence are both very similar to those of the classical crossed dipole antenna. When the PIN diode placed in the -45° direction is switched, the electric field and current distributions hardly change, which also verifies the result that the reflection coefficient hardly changes from another aspect. Therefore, the electromagnetic wave regulation of the two orthogonal channels is independent of each other, which also shows that the PIN diode state serial number can be used to characterize the 2-bit phase of the unit.

[0053] In the design of the unit, it is difficult to avoid the appearance of asymmetry, especially after loading active devices such as PIN tubes, which will lead to the deterioration of cross polarization. At the same time, a higher cross-polarization level usually means greater interference or crosstalk in the communication system. However, in order to achieve the 2-bit resolution phase regulation of the dual-line polarized incident electromagnetic wave with as few PIN diodes as possible, the unit uses an asymmetric dipole to realize the 2-bit phase resolution regulation of two PIN tubes for single-line polarization. The asymmetry during the switching of the unit working state will surely lead to the deterioration of cross polarization. Here, a cross isolation structure is designed and constructed to avoid the current flow between the two orthogonal asymmetric dipoles, thus significantly reducing the cross-polarization level of the structure.

[0054] First, observe Figure 6The electric field and current shown can qualitatively evaluate the coupling characteristics between the two channels and the degree of cross-polarization interference. Here, it is still assumed that the +45° polarization is the main polarization. As mentioned above, when the main polarization wave irradiates the unit, the dipoles in this polarization direction will be in a strong resonance state and will induce a relatively large current, which will flow along the +45° dipole arms. Obviously, the other orthogonally placed dipole will hardly be excited. In addition, through the introduction of the cross-isolation structure, the current flowing along the main polarization direction is effectively prevented from directly flowing to the cross-polarization direction, thereby reducing the cross-polarization field radiation and energy leakage. Although as Figure 6 shown, a certain current is induced, but the current flows in opposite directions on both sides of the dipole, which will make the generated cross-polarized electric field quite small. Here, the simulation results of an asymmetric cross-dipole with the same size but without a cross-isolation structure are also given. It can be seen that due to the asymmetry, a relatively large current is induced at the center of the orthogonal dipole and an obvious electric field is generated.

[0055] To measure the cross-polarization level more precisely, the cross-polarization definition of Ludwig Ⅲ commonly used in antenna measurements and the concept of cross-polarization discrimination commonly used in base station antenna design standards are adopted here.

[0056] For the proposed metasurface unit, the +45° and -45° polarization electric fields are defined as follows:

[0057]

[0058] Here, the dual-polarization independently adjustable structure ensures the modulation characteristics of the unit for any incident polarization. Therefore, the polarization of the incident wave will determine the direction of the main polarization, and its orthogonal direction will be the cross-polarization component, that is, the direction of the interference term.

[0059] Correspondingly, the cross-polarization discrimination of the unit can be obtained:

[0060]

[0061] Thus, the cross-polarization discrimination of the unit operating in different PIN diode states in the end-fire direction is analyzed. Table Ⅱ lists the typical cross-polarization discrimination simulation results for a given PIN diode sequence. It can be seen that this value remains above 35 dB in all states, and there is an obvious improvement compared with the directly connected cross-dipole, and it can be seen that the cross-isolation structure suppresses the cross-polarization interference.

[0062] Table Ⅱ Typical values of the cross-polarization discrimination of the unit

[0063]

[0064]

[0065] Embodiment:

[0066] Based on the above structural design and principle, a metasurface composed of 12×12 units was constructed, and the electrical size of the array was 4.2×4.2λ 2 . To provide a radio frequency source with high linear polarization purity, a double-ridged horn in the 2-18 GHz band was selected as the source feed, with a gain of 10 dBi. At a frequency of 3.5 GHz, the cross-polarization discrimination in the end-fire direction was 50 dB. The horn was fixed at a position 288 mm away from the center of the metasurface, and the focal ratio was set to 0.8. Simulations were carried out on the efficiency, beam scanning, and cross-polarization discrimination of the metasurface.

[0067] The compensation phase distribution of the metasurface was calculated using the ray tracing method, that is

[0068]

[0069] is the compensation phase for each unit, k 0 is the wave number in free space, is the position vector of each unit, is the position vector of the horn feed, is the unit vector in the direction of the target beam, is a constant phase value that can be optimized.

[0070] When excited with +45° polarization and the target beam of the metasurface is in the end-fire direction, the phase distribution is obtained from the above formula. Through the FPGA and the feeding network, each unit can be encoded in real time as Figure 6 the encoding shown, and the simulation results obtained are as shown in Figure 6 . It can be seen that the main polarization gain reaches 19.1 dBi, and the corresponding aperture efficiency reaches 36.7%, which is much greater than that of the existing dual-linear polarization 1-bit metasurface. At the same time, the cross-polarization discrimination reaches 37 dB. Similarly, the results under beam scanning can be obtained. Figure 7 The simulation results of the beam scanning of the metasurface in the E-plane when excited with +45° polarization and in the H-plane when excited with -45° polarization within 0 to 40° are given. It can be seen that within the scanning angle, the gain of the metasurface remains within -3 dB, and a high cross-polarization discrimination and a low sidelobe level are maintained. Table III gives the cross-polarization discrimination results of the metasurface during beam scanning. It can be seen that within any scanning angle range, the cross-polarization discrimination of the metasurface along the main beam direction is greater than 27 dB, and the sidelobe levels are all less than -10 dB. The proposed metasurface also has obvious advantages in cross-polarization discrimination compared with the existing dual-linear polarization metasurfaces.

[0071] Table III Cross-polarization discrimination results during beam scanning

[0072]

[0073] In addition, due to the high phase resolution and flexible modulation dimensions of this metasurface, multi-dimensional modulation of electromagnetic waves can be achieved. Figure 8 The results of splitting the beam into two beams with ±45° polarization when the metasurface is irradiated by an x-polarized horn are given; Figure 9 The results of realizing linear-circular polarization conversion and performing beam scanning of this metasurface are given.

Claims

1. A high cross-polarization discrimination dual-polarized 2-bit programmable metasurface, characterized in that, it includes a metasurface array composed of 12×12 metasurface units arranged periodically, and the unit state is switched in real time by an electrically tunable method; the metasurface unit includes three dielectric plates, namely dielectric plate one, dielectric plate two and dielectric plate three. A pp layer one is added between dielectric plate one and dielectric plate two, and a pp layer two is added between dielectric plate two and dielectric plate three; the metasurface unit is provided with four copper layers from top to bottom, which are successively divided into a main resonator layer, a current isolation layer, a ground layer and a feeding network layer; the main resonator layer is located on the upper surface of dielectric plate one, the current isolation layer is located on the lower surface of dielectric plate one, the ground layer is at the bottom of dielectric plate two, and the bottom layer of the unit is used for the layout of the DC feeding network to form a feeding network layer, and the feeding network layer is located at the bottom of dielectric plate three; the main resonator layer is composed of two dipoles orthogonally placed in the ±45° directions and four parasitic patches of different lengths. A plurality of metallized vias are arranged in the middle and at the four ends of the unit. The metallized vias are used to connect the main resonance layer to the feeding network layer, and then directly connected to the ground layer through an inductor and a blind hole in the center; the metasurface unit includes 8 inductors to isolate radio frequency and direct current. Among them, 4 are respectively located at the edge positions of the main resonator layer of the unit to isolate radio frequency and the positive DC bias signal, and the other 4 are located at the center of the feeding network layer to isolate radio frequency and DC ground; the two orthogonal dipoles and two parasitic patches in their respective directions are separated by slots, and PIN diodes are placed between each slot.

2. A high cross-polarization discrimination dual-polarized 2-bit programmable metasurface according to claim 1, characterized in that, the two dipoles are two centrally symmetric patches, and the parasitic patches and the central patches are connected by diodes. The negative electrodes of the diodes face the center of the structure and are finally grounded. At the center of the structure, the two orthogonal central resonant patches are separated by the cross isolation structure of the second copper layer.

3. A high cross-polarization discrimination dual-polarized 2-bit programmable metasurface according to claim 1, characterized in that, the dielectric plate is a copper-clad F4B dielectric plate, which is formed by pressing copper-clad F4B dielectric plates. The thickness of the plate is 2 mm, the dielectric constant is 2.2, the loss tangent is 0.001, and a pp layer is added between the dielectric plates for pressing. The thickness of the pp layer is 0.05 mm; the overall cross-sectional height of the metasurface unit is 0.07 wavelength of the electrical size at the center frequency of 3.5 GHz.

4. A high cross-polarization discrimination dual-polarized 2-bit programmable metasurface according to claim 1, characterized in that, the period of the metasurface unit is 30.1 mm, and the electrical size is 0.35 wavelength.

5. A high cross-polarization discrimination dual-polarized 2-bit programmable metasurface according to claim 1, characterized in that, The metasurface array operates at 3.5 GHz. A horn antenna is used to spatially feed the metasurface. The radio frequency signal is input from the horn end, radiated to the metasurface through the horn antenna. The metasurface realizes the functions of beam scanning and beam splitting of the scattered beam through the real-time switching of the PIN diode sequence, thereby verifying the performance of the metasurface.

6. A high cross-polarization discrimination dual-polarized 2-bit programmable metasurface according to claim 5, characterized in that, the horn antenna is fixed at a distance of 288 mm from the metasurface, and the focal diameter ratio is 0.

8.

7. A high cross-polarization discrimination dual-polarized 2-bit programmable metasurface according to any one of claims 1-6, characterized in that, the programmable metasurface is used for wireless communication, deep space exploration, energy transmission, and microwave imaging.

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